Platinum Metals Review - Johnson Matthey Technology Review

VOLUME 53 NUMBER 4 OCTOBER 2009

Platinum Metals Review

www.platinummetalsreview.com E-ISSN 1471–0676

© Copyright 2009 Johnson Matthey PLC

http://www.platinummetalsreview.com/ Platinum Metals Review is published by Johnson Matthey PLC, refiner and fabricator of the precious metals and sole marketing agent for the six platinum group metals produced by Anglo Platinum Limited, South Africa. All rights are reserved. Material from this publication may be reproduced for personal use only but may not be offered for re-sale or incorporated into, reproduced on, or stored in any website, electronic retrieval system, or in any other publication, whether in hard copy or electronic form, without the prior written permission of Johnson Matthey. Any such copy shall retain all copyrights and other proprietary notices, and any disclaimer contained thereon, and must acknowledge Platinum Metals Review and Johnson Matthey as the source. No warranties, representations or undertakings of any kind are made in relation to any of the content of this publication including the accuracy, quality or fitness for any purpose by any person or organisation.

E-ISSN 1471–0676

PLATINUM METALS REVIEW A Quarterly Survey of Research on the Platinum Metals and of Developments in their Application in Industry www.platinummetalsreview.com

VOL. 53 OCTOBER 2009 NO. 4

Contents Platinum Metals Review Highlights PGM Research

182

An editorial by David Jollie

A Highly Active Palladium(I) Dimer for Pharmaceutical Applications

183

By Thomas J. Colacot

Precious Palladium-Aluminium-Based Alloys with High Hardness and Workability

189

By Julien Brelle, Andreas Blatter and René Ziegenhagen

The 23rd Santa Fe Symposium on Jewelry Manufacturing Technology

198

A conference review by Christopher W. Corti

Novel Chiral Chemistries Japan 2009

203

A conference review by David J. Ager

Melting the Platinum Group Metals

209

By W. P. Griffith

PGM Highlights: Ruthenium Complexes for Dye Sensitised Solar Cells

216

By M. Ryan

“PEM Fuel Cell Electrocatalysts and Catalyst Layers: Fundamentals and Applications”

219

A book review by Gregory J. Offer

The Taylor Conference 2009

221

A conference review by S. E. Golunski and A. P. E. York

Abstracts

226

New Patents

228

Indexes to Volume 53

230

Editor: David Jollie; Assistant Editor: Sara Coles; Editorial Assistant: Margery Ryan; Senior Information Scientist: Keith White Platinum Metals Review, Johnson Matthey PLC, Orchard Road, Royston, Hertfordshire SG8 5HE, U.K. E-mail: [email protected]

DOI: 10.1595/147106709X477160

Platinum Metals Review Highlights PGM Research Welcome to the October 2009 issue of Platinum Metals Review. In this issue, we introduce a new occasional series of “PGM Highlights”, in which we present selected examples of activity in an area of current interest in platinum group metal (pgm) research. Here, we have chosen the area of photoconversion, in which ruthenium-based dyes play a significant role for dye sensitised solar cells. This mini-review by Margery Ryan, of the PMR Editorial Team, highlights some of the innovative work in the recent patent literature. It is an extension of the patent abstracts that we select for each issue, and aims to provide more in-depth coverage of the chosen area together with some background, referenced to the wider scientific literature, to set the scene.

Platinum Metals Rev., 2009, 53, (4), 182

Additionally, this issue includes as usual our annual Subject and Name Indexes, to appear in November. The Name Index lists the names of all authors, reviewers and conference speakers whose work has appeared in Volume 53. The Subject Index gives detailed, fully cross-referenced entries for all of the pgm-containing catalysts, alloys, compounds and complexes mentioned in this Volume, together with the principal topics by keyword. It serves to demonstrate the richness of pgm research that we have reported throughout 2009 and we hope that you will find it a useful reference. If you have any comments please contact me on: [email protected]. DAVID JOLLIE, Editor

182

DOI: 10.1595/147106709X472147

A Highly Active Palladium(I) Dimer for Pharmaceutical Applications [Pd(µ-Br)( t Bu3P)]2 AS A PRACTICAL CROSS-COUPLING CATALYST By Thomas J. Colacot Johnson Matthey, Catalysis and Chiral Technologies, West Deptford, New Jersey 08066, U.S.A.; E-mail: [email protected]

The Pd(I) dimer [Pd(μ-Br)( tBu3P)]2 is one of the best third-generation cross-coupling catalysts for carbon–carbon and carbon–heteroatom coupling reactions. Information on its characterisation and handling are presented, including its decomposition mechanism in the presence of oxygen. The catalytic activity of [Pd(μ-Br)( tBu3P)]2 is higher than either ( tBu3P)Pd(0) or the in situ generated catalyst system based on Pd2(dba)3 with tBu3P. Examples of suitable reactions for which the Pd(I) dimer offers superior performance are given.

Introduction The palladium(I) dimer, di-μ-bromobis(tri-tertbutylphosphine)dipalladium(I), [Pd(μ-Br)( t Bu3P)]2, was synthesised and fully characterised by Mingos (1, 2). However, its potential as a unique C–C and C–N coupling catalyst (3) was first explored by Hartwig (6). It has emerged as one of the best third-generation coupling catalysts for cross-coupling reactions, including C–heteroatom coupling and α-arylations. In this review, the physical and chemical characteristics of the Pd(I) dimer as a catalyst material are discussed from a practical viewpoint, and up to date information on its applications in coupling catalysis is provided.

Characteristics and Handling The Pd(I) dimer is a dark greenish-blue crystalline material, which gives a single peak in the 31 P NMR spectrum at (δ) 87.0 ppm. The 1H NMR spectrum gives a peak at (δ) 1.33 ppm (singlet; on expansion it appears as a distorted triplet) in deuterated benzene (1, 2). The compound decomposes in

chlorinated solvents, especially in deuterated chloroform. The X-ray crystal structure is reported in the literature as a dimer with Pd–Pd bonding, stabilised by bromine atoms via bridge formation (1, 2). It can be handled in air as a solid for a short period of time, allowing the user to place it into a reactor in the absence of a solvent, degas and then carry out catalysis under inert conditions. However, this compound is highly sensitive to air and moisture in the solution phase. It can also decompose in the solid phase if not stored under strictly inert conditions. The solid state decomposition pattern over time was monitored in our laboratory at 0, 48 and 112 hours (Figure 1) (4). Its sensitivity towards oxygen is well understood, and is based on the formation of an oxygen-inserted product with the elimination of hydrogen (Scheme I) (5). Figure 2 shows the oxygen sensitivity of the Pd(I) dimer on a proton-decoupled 31P NMR spectrum recorded using a solvent which was not degassed. The peak at 107 ppm indicates the presence of the oxygeninserted decomposition product. Fig. 1 The solid state oxygen sensitivity of pure Pd(I) dimer, [Pd(μ-Br)( tBu3P)]2, with time (4)

0h

Platinum Metals Rev., 2009, 53, (4), 183–188

48 h

112 h

183

Fig. 2 The oxygen sensitivity of Pd(I) dimer, [Pd(μ-Br)( tBu3P)]2, as observed in the 31 P NMR (ppm) spectrum recorded using non-degassed C6D6

180

160

140

120

100

80

60

Applications in Coupling Catalysis The high catalytic activity of the Pd(I) dimer [Pd(μ-Br)(tBu3P)]2 is due to its ease of activation, presumably to a highly active, coordinatively unsaturated and kinetically favoured ‘12-electron’ catalyst species, (tBu3P)Pd(0) (Scheme II). This renders the Pd(I) dimer more active than either the known ‘14-electron Pd(0)’ catalyst, (tBu3P)2Pd(0), or the Pd(0) catalyst generated in situ by mixing Pd2(dba)3 with two molar equivalents of tBu3P. The applications of the Pd(I) dimer in organic synthesis are described below.

Carbon–Heteroatom Coupling Hartwig identified the potential of the Pd(I) dimer as a highly active catalyst for C–N coupling

40

20

0 ppm

using aryl chlorides as substrates with various amines at room temperature. A few examples are shown in Scheme III (6). Typically, aryl chloride coupling requires higher temperatures and longer reaction times when using the in situ generated Pd(0) catalyst, or even the (tBu3P)2Pd(0) complex (7). Around the same time, Prashad and coworkers at Novartis reported an amination reaction using [Pd(μ-Br)(tBu3P)]2 with challenging substrates such as hindered anilines (8). Scheme IV shows the coupling of N-cyclohexylaniline with bromobenzene, comparing the performance of the Pd(I) dimer with those of in situ generated catalysts derived from Pd(OAc)2 with tBu3P, BINAP, Xantphos or DPEphos. The performance of [Pd(μ-Br)(tBu3P)]2 is superior in each case.

CH2 P

Br P

Pd

Pd

O2 -2 H –2H

P

Br

Pd(I) dimer Pd (I) dimer 87 PPM P NMR: 87 ppm

3 1P NMR: 31

Br

31

Br

O Pd

Pd O

3P 1PNMR: NMR:

P

CH2 107 ppm 1 07 P PM

Br P

Pd

Pd

P

Scheme I The oxygen sensitivity of Pd(I) dimer, [Pd(μ-Br)( tBu3P)]2, with the formation of an inactive Pd-O species (5)

P

Pd

Br

Scheme II The activation of Pd(I) dimer to a 12-electron catalyst species during coupling catalysis

Highly active 12-electron species

Platinum Metals Rev., 2009, 53, (4)

184

R Cl +

NH

N

NaOtBu, RT 15 min–1 h

R

Scheme III Aryl chloride coupling at room temperature (6)

R

0.5 mol% Pd(I) dimer

R Yield 88–99%

R = Bu, Ph or R2NH = morpholine

Br

H N

N

Pd catalysts

+

NaOtBu, Toluene, 110°C Catalyst loading

Yield

0.25 mol%

93%

Pd(OAc)2 + Bu3P

0.5 mol%

86%

Pd(OAc)2 + BINAP

0.5 mol%

27%

[Pd(μ-Br)(tBu3P)]2 t

Pd(OAc)2 + Xantphos

0.5 mol%

27%

Pd(OAc)2 + DPEphos

0.5 mol%

none

Scheme IV Pd(I) dimer-catalysed C–N coupling of N-cyclohexylaniline (8)

Hartwig’s group subsequently conducted a detailed study to understand the activity and scope of [Pd(μ-Br)(tBu3P)]2 in the amination of fivemembered heterocyclic halides. Various combinations of Pd precursors with tBu3P were studied for a model system, the reaction of N-methylaniline with 3-bromothiophene. The fastest reaction occurred with the Pd(I) dimer (9). More recently, Eichman and Stambuli reported a very interesting zinc-mediated Pd(I) dimercatalysed C–S coupling, which should generate much interest in the area of C–S coupling (Scheme V) (10). For the reactions of alkyl thiols with aryl bromides and iodides, potassium hydride was the best base, as illustrated in Scheme V. For the Pd-catalysed cross-coupling reactions of aryl ZnCl2 (catalyst) KH (1.1 equiv.)

Ar-X + RSH X = Br, I

0.5–2.0 mol% Pd(I) dimer THF


bromides and benzenethiol using zinc chloride in catalytic amounts, with sodium tert-butoxide as the base, most of the reactions were sluggish and gave low yields. However, the addition of stoichiometric amounts of lithium iodide increased the rate of the reaction significantly, which is speculated to be due to the anionic effects proposed by Amatore and Jutand (11).

Carbon–Carbon Bond Formation Hartwig’s group also studied the Suzuki coupling of sterically hindered tri-substituted aryl bromides. A Pd(I) dimer loading of 0.5 mol%, in the presence of alkali metal hydroxide base, gave good yields at room temperature within minutes (Scheme VI) (6). Scheme V Zinc-mediated Pd(I) dimer-catalysed C–S coupling (10) Ar-S-R Yield 46–99% R = tBu, nBu, PhCH2

185

X

Scheme VI Room temperature Suzuki coupling of sterically bulky aryl bromides (6)

Ph

R2

R1 +

0.5 mol% Pd(I) dimer R2 PhB(OH)2

R1

KOH, THF 15 min, RT

R3

R3

X = Br; R1 = H, CN, CF3, OCH3 or CH3; R2, R3 = H or CH3

Research work from Ryberg at Astra Zeneca (12) demonstrated a very practical, clean method for C–CN coupling using the Pd(I) dimer [Pd(μ-Br)(tBu3P)]2 to produce 3 kg to 7 kg of product routinely (Scheme VII). During the initial in situ studies, Pd2(dba)3 in combination with commercial ligands such as Q-Phos, tBu2Pbiphenyl or Cy2P-biphenyl gave poor results, although with proper process tweaking improvements were made. The conventional ligands, such as Ph3P and dppf, were not useful. However, the P(o-tol)3/Pd2(dba)3 system behaved somewhat well with the formation of some byproducts. The

Yield 84–95%

Pd loading was as high as 5 mol% (12). For the α-arylation (13) of fairly challenging carbonyl compounds, Hartwig identified the Pd(I) dimer [Pd(μ-Br)(tBu3P)]2 as one of the best catalysts, especially for amides and esters. The work from Hartwig’s group provided general conditions for α-arylations of esters and amides (14–16). The coupling reactions of aryl halides with esters are summarised in Scheme VIII (17). For aryl bromides, lithium dicyclohexylamide (LiNCy2) was the best base, while sodium hexamethyldisilazide (NaHMDS) was required for aryl chloride substrates. Intermolecular α-arylation of

OH

OH Pd(I) dimer, Zn(CN)2 Zn, DMF

Br N

NC N

50ºC, 1–3 h

N

N O

O

R

Scheme VII The Pd(I) dimer-catalysed cyanation reaction, which may be carried out on a kilogram scale (12)

H N

H N

1

O

+ R3

R2

(ii) Pd(I) dimer RT–100ºC, 4 h OR

R1, R2 = Me, H; R = Me, tBu X = Br, Cl; R3 = Me, MeO, F

R1

(i) LiNCy2 (X = Br) or X NaHMDS (X = Cl) Toluene, RT, 10 min

R2 O OR

R3 Yield 71–88%

Scheme VIII α-Arylation of esters under milder conditions using the Pd(I) dimer catalyst (17)


186

in situ generated zinc enolates of amides was also reported in excellent yield under Reformatsky conditions using the Pd(I) dimer, (Scheme IX) (18). The appropriate choice of base for the substrate is critical for this reaction. The α-vinylation of carbonyl compounds has been reported recently by Huang and coworkers at Amgen, catalysed by the Pd(I) dimer in conjunction with lithium hexamethyldisilazide (LiHMDS) base (Scheme X) (19). The same catalytic system can be extended to the α-vinylation

of ketones and esters. The combination of Pd2(dba)3 with Buchwald ligands such as X-Phos and S-Phos gave inferior results, as did in situ catalysis with ligands such as Xantphos, (S)-MOP, BINAP and IPr-HCl (carbene) in the presence of Pd2(dba)3. Amgen researchers also reported a stereoselective α-arylation of 4-substituted cyclohexyl esters using the Pd(I) dimer at room temperature, with lithium diisopropylamide (LDA) as the base. Diastereomeric ratios, dr, of up to 37:1 were achieved (Scheme XI) (20). O

Br

O N

NMe2

NMe2 (i) 1.5 equiv. Zn* THF, RT, 30 min (ii) 2.5 mol% Pd(I) dimer

X

O

N Yield 94%

O

X R''

R'

R

+ R

2

R'''

R3

R

1

R3

Pd(I) dimer, LiHMDS

1

Toluene, 80ºC, 24 h

Scheme IX α-Arylation of amides under Reformatsky conditions (18); Zn* = activated zinc species

R'

X = Br, OTf, OTs

R''

R'''

R2

Yield 48–95%

Scheme X α-Vinylation reaction using Pd(I) dimer catalyst (19); OTf = trifluoromethane sulfonate; OTs = tosylate

Glossary Ligand

Full name

BINAP

2,2' -bis(diphenylphosphino)-1,1' -binaphthyl

t

Bu2P-biphenyl

2-(di-tert-butylphosphino)biphenyl

t

Bu3

tri-tert-butylphosphine

Cy2P-biphenyl

2-(dicyclohexylphosphino)biphenyl

dba

dibenzylideneacetone

DPEphos

bis(2-diphenylphosphinophenyl)ether

dppf

1,1' -bis(diphenylphosphino)ferrocene

IPr-HCl (carbene)

1,3-bis-(2,6-diisopropylphenyl)imidazolium chloride

(S)-MOP

2-(diphenylphosphino)-2' -methoxy-1,1' -binaphthyl

OAc

acetate

P(o-tol)3

tri(o-tolyl)phosphine

Ph3P

triphenylphosphine

Q-Phos

1,2,3,4,5-pentaphenyl-1' -(di-tert-butylphosphino)ferrocene

S-Phos

2-dicyclohexylphosphanyl-2' ,6' -dimethoxybiphenyl

Xantphos

4,5-bis(diphenylphosphino)-9,9-dimethylxanthene

X-Phos

2-dicyclohexylphosphino-2' ,4' ,6' -triisopropylbiphenyl


187

R

1

Pd(I) dimer, LDA +

R1

R–X

R

Toluene, RT, 3–24 h CO2Et

CO2Et Yield 37–85% Up to 37:1 dr

Conclusions The Pd(I) dimer [Pd(μ-Br)(tBu3P)]2 stands out as unique among the third generation catalysts for cross-coupling. It has a higher activity than other catalysts, a fact which can be attributed to its ability to form a 12-electron ‘ligand-Pd(0)’ species during the activation step in the catalytic cycle. Its application to a wide variety of C–C, C–N and C–S

Scheme XI Room temperature diasteroselective α-arylation of 4-substituted cyclohexyl esters using Pd(I) dimer (20)

cross-coupling reactions will enable higher yields and better product selectivities under relatively mild conditions.

Acknowledgements Fred Hancock and Gerard Compagnoni of Johnson Matthey’s Catalysis and Chiral Technologies are acknowledged for their support of this work.

References 1 R. Vilar, D. M. P. Mingos and C. J. Cardin, J. Chem. Soc., Dalton Trans., 1996, (23), 4313 2 V. Durà-Vilà, D. M. P. Mingos, R. Vilar, A. J. P. White and D. J. Williams, J. Organomet. Chem., 2000, 600, (1–2), 198 3 T. J. Colacot, ‘Di-μ-bromobis(tri-tert-butylphosphine)dipalladium(I)’, to be included in 2009 in “e-EROS Encyclopedia of Reagents for Organic Synthesis” , eds. L. A. Paquette, D. Crich, P. L. Fuchs and G. Molander, John Wiley & Sons Ltd., published online at: www.mrw.interscience. wiley.com/eros (Accessed on 30th July 2009) 4 Johnson Matthey Catalysts, ‘Coupling Catalysis Application Table’, West Deptford, New Jersey, U.S.A.: http://www.jmcatalysts.com/pharma/pdfsuploaded/Coupling%20%20Apps%20Table.pdf (Accessed on 30th July 2009) 5 V. Durà-Vilà, D. M. P. Mingos, R. Vilar, A. J. P. White and D. J. Williams, Chem. Commun., 2000, (16), 1525 6 J. P. Stambuli, R. Kuwano and J. F. Hartwig, Angew. Chem. Int. Ed., 2002, 41, (24), 4746 7 R. Kuwano, M. Utsunomiya and J. F. Hartwig, J. Org. Chem., 2002, 67, (18), 6479 8 M. Prashad, X. Y. Mak, Y. Liu and O. Repic, J. Org. Chem., 2003, 68, (3), 1163

9 M. W. Hooper, M. Utsunomiya and J. F. Hartwig, J. Org. Chem., 2003, 68, (7), 2861 10 C. C. Eichman and J. P. Stambuli, J. Org. Chem., 2009, 74, (10), 4005 11 C. Amatore and A. Jutand, Acc. Chem. Res., 2000, 33, (5), 314 12 P. Ryberg, Org. Process Res. Dev., 2008, 12, (3), 540 13 C. C. C. Johansson and T. J. Colacot, Angew. Chem., 2009, in press 14 T. Hama and J. F. Hartwig, Org. Lett., 2008, 10, (8), 1549 15 T. Hama and J. F. Hartwig, Org. Lett., 2008, 10, (8), 1545 16 T. Hama, X. Liu, D. A. Culkin and J. F. Hartwig, J. Am. Chem. Soc., 2003, 125, (37), 11176 17 T. Hama and J. F. Hartwig, Synfacts, 2008, (7), 0750 18 T. Hama, D. A. Culkin and J. F. Hartwig, J. Am. Chem. Soc., 2006, 128, (15), 4976 19 J. Huang, E. Bunel and M. M. Faul, Org. Lett., 2007, 9, (21), 4343 20 E. A. Bercot, S. Caille, T. M. Bostick, K. Ranganathan, R. Jensen and M. F. Faul, Org. Lett., 2008, 10, (22), 5251

The Author Dr Thomas J. Colacot is a Research and Development Manager in Homogeneous Catalysis (Global) of Johnson Matthey’s Catalysis and Chiral Technologies business unit. Since 2003 his responsibilities include developing and managing a new catalyst development programme, catalytic organic chemistry processes, scale up, customer presentations and technology transfers of processes globally.


188

DOI: 10.1595/147106709X472192

Precious Palladium-Aluminium-Based Alloys with High Hardness and Workability PROMISING POTENTIAL FOR APPLICATION IN JEWELLERY AND WATCHMAKING By Julien Brelle and Andreas Blatter* PX Holding SA, R&D, Boulevard des Eplatures 42, CH-2300 La Chaux-de-Fonds, Switzerland; *E-mail: [email protected]

and René Ziegenhagen Cartier Horlogerie, Branch of Richemont International SA, 10 Chemin des Aliziers, CH-2300 La Chaux-de-Fonds, Switzerland

New palladium-aluminium-based alloys with promising potential for application in the areas of jewellery and watchmaking are presented. A particular emphasis is placed on the mechanical behaviour of ternary palladium-aluminium-ruthenium (PdAlRu) alloys with 95 wt.% Pd. The new alloys combine high plasticity with high hardness relative to common Pd alloys. The low work-hardening rate enables cold working in excess of 95% reduction without intermediate annealing. The hardness (Vickers pyramid indentation) ranges from 100 HV to 300 HV in the annealed condition, depending on the Al:Ru ratio. Their whiteness in terms of colour coordinates is compared with platinum and white gold. The feasibility of porcelain fusion to PdAlRu for decorative purposes is also demonstrated.

Palladium is not widely recognised as a precious metal in jewellery and watchmaking. Yet, with the price evolution of precious metals over the last few years, use of palladium in these markets has seen renewed interest (1–3). For illustration, gold was roughly double the price of palladium in 2006 and about four times the price of palladium at the end of 2008 (4). In addition, palladium alloys for jewellery, which usually contain 95 wt.% Pd (950 Pd), have a lower density (around 12 g cm–3) than 18 carat white gold (close to 15 g cm–3) and 950 platinum (about 21 g cm–3). Hence, an item of volume 1 cm3 in 950 Pd contains 11.4 g Pd. By comparison, the same item made in 18 carat white gold (750 Au) or 950 Pt will contain, respectively, 11.3 g Au or 20 g Pt. Furthermore, the 950 Pd alloys approach the ‘ideal’ white colour of platinum without requiring rhodium plating like most white gold alloys. Unlike for gold alloys, the white sheen will therefore not wear off, eliminating the bother and expense of replating. 950 Pd alloys also satisfy the general requirements for jewellery and watch alloys: they


are nickel-free, malleable, easy to polish, and have desirable setting and forming characteristics. Their high Pd content also confers good corrosion and tarnishing resistance, a crucial aspect in jewellery and watchmaking. The inherently low hardness of Pd alloys is, however, an important technical limitation for their use in jewellery and particularly in watchmaking. The hardness of existing 950 Pd alloys, with alloying metals such as ruthenium (PdRu), gallium (PdGa) or copper (PdCu), falls between 70 HV (PdCu) and 120 HV (PdGa) in the annealed state, and between 145 HV (PdCu) and 200 HV (PdGa) after 75% strain hardening. These values are substantially lower than those typical of platinum or white gold alloys (≥ 130 HV annealed, ≥ 250 HV work hardened). In an attempt to develop a 950 Pd single-phase alloy with substantially higher hardness, comparable with platinum and white gold, while maintaining the favourable colour and workability of conventional Pd alloys, we investigated PdAlbased compositions, in particular the PdAlRu

189

system. This paper describes the background to the alloy development, presents the main characteristics of 950 PdAlRu alloys in terms of mechanical properties and workability, and addresses the possibility of fusing coloured ceramic material to the alloy for decorative purposes.

Background to the Development of the PdAlRu Alloys While precipitation hardening may also be of interest to further increase the rigidity and wear resistance of finished components, solid solution strengthening is the mechanism that must provide the base hardness of the alloy in the annealed state. Solid solution strengthening is the result of strain produced in the crystal lattice, mainly by the size misfit between matrix and solute atoms. Since size misfit also limits the terminal solid solubility, as described by the Hume-Rothery rules (5), it must be kept within certain limits to ensure a solubility of at least 5 wt.%, which is necessary for a 950 Pd single-phase alloy. For a given solute, the strength increases with its atomic fraction (at.%). Higher atomic fractions are achieved when alloying with light elements. In 950 Pd, for illustration, 5 wt.% aluminium corresponds to 17.2 at.%. A 950 Pd alloy may include several alloy additions, which must be fully soluble and must add up to a total of 5 wt.%. The effects of a great number of solute elements on the hardness of palladium have been compiled previously (6, 7). Germanium, silicon and boron have a strong hardening effect. However, B is difficult to alloy and Ge and Si both exhibit nearly zero solubility. As a result, when added in sufficient concentrations to give a hardness above 150 HV, these elements tend to precipitate at the grain boundaries and thereby render the alloy too brittle for practical use. For those elements which are more practical in terms of alloying, such as other precious metals or 3d transition metals, the hardness values attained at concentrations of 5 wt.% barely exceed 100 HV. Ru is one of the elements showing the most pronounced effect on the hardness of Pd alloys. Hardness values in the range 150 HV to 200 HV can be achieved with rare earth metals such as cerium (8).


With respect to the light elements, 5 wt.% titanium raises the hardness to 150 HV (9), while Al boosts the value to 320 HV (440 HV after 80% cold work), according to our own experiments. While a hardness of 150 HV is at the lower edge of the target range, a value of 320 HV may be inconveniently high for many conventional jewellery manufacturing operations such as stamping or setting. The present study therefore focused on PdAlbased alloys, incorporating ternary additions of Ru, Ti and magnesium in order to moderate the hardness. Ru was chosen because it is a noble metal, a good solution hardener, and commonly used in 950 Pd alloys. Ti and Mg were chosen because they are lightweight, good solution hardeners, and may possibly provide a mechanism of precipitation hardening by the formation of tiny AlTi or AlMg compounds upon ageing – in similarity with superalloys. Table I shows the hardness values obtained for various ternary alloys in the annealed and 80% work hardened conditions, respectively. This shows that the hardness values in the annealed state lie in the target range and that cold work generates substantial hardening. The values displayed are those for ‘low’ and ‘high’ concentrations of the ternary additions; intermediate concentrations gave intermediate values for hardness. All alloys were single phase and sufficiently malleable for a rolling reduction of 80% without cracking. It is interesting to note that there have been two independent patent applications for 950 PdAl-based alloys (10, 11). Table I

Vickers Hardness Values of Various PdAl-(Ti, Mg, Ru) Alloys in the Annealed and 80% Reduction Work-Hardened States* Alloy

Hardness, HV Annealed

Work-hardened

Pd95.5Al1.3Ti3.2

154

366

Pd95.5Al0.4Ti4.1

128

338

Pd95.5Al3.8Mg0.7

242

400

Pd95.5Al1.9Mg2.6

170

340

Pd95.5Al2.8Ru1.7

224

343

Pd95.5Al0.9Ru3.6

158

247

* The standard deviations associated with the displayed mean values are below ± 7 HV

190

The advantage of Ru as the ternary element is that unlike Mg or Ti, it does not cause a violent reaction with Al upon alloying. In this paper, we focus on our development work on the 950 PdAlRu system.

Properties

Intensity, a.u.

Two alloys of nominal composition (in wt.%) Pd95.5Al0.9Ru3.6 and Pd95.5Al2.8Ru1.7 were prepared in a vacuum induction melting unit. The unit chamber was evacuated and purged with argon several times before backfilling with argon to 600 mbar. The elemental metals were melted in a zirconia crucible. The Al flakes were wrapped in Pd sheets to avoid any reaction with the crucible and also to alloy the Al with the higher melting point Pd without significant expulsion of Al. Plate-like ingots of 5 kg each were cast into an oxidised copper mould to constitute the feedstock for the various tests. After a first flat rolling, rods were cut off the plate and further rolled to adequate size for tensile testing while the rest of the plate was used for workability tests and microstructural investigations. The X-ray diffraction pattern in Figure 1 reveals that the ternary alloys are essentially single phase, face centred cubic (f.c.c.) solid solutions. In Ru-rich alloys, a new diffraction peak appears, and its intensity increases with increasing Ru content. Additional peaks, too weak to be seen in Figure 1, become visible when zooming into the data. These peaks, located at scattering angles, 2θ, of 44.0º,

58.3º, 78.2º, 84.8º, and 104.8º, respectively, are close to those of pure Ru and enable the second phase to be assigned to a Ru-rich PdRu hexagonal close packed (h.c.p.) solid solution. The measured lattice constants, a, of the ternary f.c.c. matrix are accurately reproduced with a hard sphere approximation by the linear combination of the atomic sizes, Sj, defined as the minimum interatomic distance in the unit cell of element j (Equation (i)): a = 2 ×⋅ ∑ c j S j

where the coefficients c j correspond to the atomic fraction of element j. The atomic sizes for Pd, Al and Ru are, respectively, 2.750 nm, 2.863 nm and 2.650 nm (12). Since Al has a greater atomic size than Pd by 4.1%, whereas Ru is smaller by 2.6%, the apparent shift in a is marginal among different ternary alloys. In other words, strengthening due to lattice distortion is not apparent through a significant shift of the diffraction peaks. In particular, there exists a ternary composition for which the lattice constant almost matches that of elemental Pd. The lattice constant derived from the diffraction pattern of Pd95.5Al0.9Ru3.6 is 3.888 nm, compared to 3.886 nm for Pd.

Hardness The hardness of the PdAlRu alloys in the annealed state (1000ºC for one hour), measured using a Vickers hardness tester with a 1 kg load Fig. 1 X-Ray diffraction patterns of annealed Pd95.5Al0.9Ru3.6. A θ–2θ configuration and Cu Kα1 radiation (α = 0.15408 nm) were employed. The sample is predominantly f.c.c. single phase. An additional peak at 2θ ≈ 42 indicates the presence of a second phase

Pd95.5Al0.9Ru3.6

0

20

40

60

80

(i)

j

100

120

Scattering angle, 2θ


191

Fig. 2 Variation of Vickers hardness values, HV1, with Al content x (wt.%) of annealed Pd95AlxRu(5 – x) alloys. The linear approximation is shown

Vickers hardness, HV1

350 300 250 200 y = 42.523x + 109 150

R2 = 0.9911

100 50 0

1

2

3

5

4

6

Aluminium, wt.%

(HV1), approximates to a linear function of the Al content, as shown in Figure 2. Therefore, the hardness can be tuned to any value from about 100 HV (PdRu) to 320 HV (PdAl). The hardness values in the work-hardened condition range from 165 HV (PdRu) to 440 HV (PdAl). Corresponding values for two ternary compositions are given in Table I. Upon ageing of annealed samples at 700ºC for twenty minutes, the hardness of those alloys with higher Ru content increases slightly, indicating a mechanism of precipitation hardening. The intensity of age hardening remains modest, however: it approaches but does not exceed the increase of 25 HV observed at the highest Ru content, i.e. for the binary 950 PdRu alloy. This strengthening is also evident in an

increase in yield strength of 50 MPa for Pd95.5Al0.9Ru3.6 (Figure 3). Age hardening is accompanied by a substantial increase in electrical resistivity, ρel, as measured by means of the four-point probe technique on discs of thickness 2 mm and diameter 27 mm (13). For Pd95.5Al0.9Ru3.6, ρel reversibly switches from 25.5 μΩ cm in the annealed state to 91 μΩ cm in the age hardened state. By comparison, the values for Pd95.5Al2.8Ru1.7, which does not exhibit age hardening, are 32.1 μΩ cm and 35.6 μΩ cm, respectively. Since an increase in electrical resistivity is caused by additional scattering of electrons at crystal imperfections, such as a lattice distortion or the presence of precipitates, and since age hardening occurs with the appearance of a PdRu phase as Fig. 3 Typical engineering stressstrain curves recorded for Pd95.5Al2.8Ru1.7 and Pd95.5Al0.9Ru3.6 in the annealed (AN), agehardened (AH) and 85% cold-worked (CW) states

1200 Pd95.5Al2.8Ru1.7 Engineering stress, MPa

1000

CW

Pd95.5Al0.9Ru3.6

800 AH 600

AN AH AN

400 200

0

5

10

15

20

25

30

35

Engineering strain, %


192

discussed above, it is tempting to correlate age hardening with PdRu precipitates. However, the main diffraction peak of the PdRu phase persists upon annealing, suggesting that the precipitates are not fully solubilised. Figure 4 shows the variation of conventional yield strength, Rp0.2, ultimate tensile strength, Rm, and fracture strain, A50, with cold work. The alloys undergo significant strain hardening only upon initial cold working. Beyond about 30% of cold work, yield strengths (Figure 4) and hardness values (Figure 5) remain essentially constant. It is worth mentioning that the tensile properties of the Ru-rich alloy after standard annealing (1000ºC for 1 hour) depend on its thermomechanical history.

This is no longer the case after cold working. We attribute this memory behaviour to a variable evolution and dissolution of the PdRu precipitates. The work hardening exponent, n, can be roughly estimated from a fit of the Hollomon equation (Equation (ii)) to the true stress-true strain curve (14): σt = Kεtn

(ii)

Here, K, the strength index, is a constant and the true stress-true strain data (σt, εt) is obtained from the engineering data (σ, ε) by Equations (iii) and (iv): σt = σ(1 + ε)

(iii)

εt = ln(1 + ε)

(iv)

1200

42

1000

35

Rm

28 Rm

600

21 Rp0.2

Pd95.5Al2.8Ru1.7 14

400 Pd95.5Al0.9Ru3.6 200

7

A50

0

0

40

20

60

A50, %

Rm/Rp0.2, Mpa

Rp0.2 800

Fig. 4 Yield strengths, Rp0.2, ultimate tensile strengths, Rm, and fracture strains, A50, as derived from standard tensile testing (EN 10002-1: 1990) of two PdAlRu alloys at various degrees of cold work. Each data point is the average of five tests (standard deviation < 3% except for A50). Connecting lines serve as a guide to the eye

100

80

Cold work, % Fig. 5 Variation of Vickers hardness, HV1, with cold work. Each data point is the average of five tests (standard deviation < 5%)

Vickers hardness, HV1

350 300 250 200 150 Pd95.5Al2.8Ru1.7 100

Pd95.5Al0.9Ru3.6

50 0

20

40

60

80

100

Cold work, %


193

where σt is the true stress, σ is the engineering stress, εt is the true strain and ε is the engineering strain. When applied to the stress-strain curves of annealed samples in the plastic domain (Figure 3), this approximation returns n = 0.29 for Pd95.5Al2.8Ru1.7 and n = 0.25 for Pd95.5Al0.9Ru3.6, values that are typical of low stacking-fault energy alloys such as Al alloys. Figure 6 depicts the mechanical properties of PdAlRu alloys in comparison with those of common Pd, Pt or Au alloys. The ternary 950 PdAlRu alloys exhibit higher strength and hardness than conventional 950 PdRu, but lower fracture strains. Tensile strengths and hardness values are similar to those of Pt or Au alloys. Fracture strains are comparable or somewhat lower in the annealed state, whereas they are higher after 75% cold work. Yield strengths may be somewhat lower or higher in the annealed condition, depending on the Al content.

After cold working, however, the yield strengths of the PdAlRu alloys remain largely below those of the Pt or Au alloys – another clear manifestation of the low work-hardening rate, i.e. the high plasticity, of these ternary alloys. Young’s modulus, E, and Poisson’s ratio, ν, are listed in Table II. These elastic properties were deduced from measurements of the longitudinal and transverse sound velocities (15). The pulseecho measurements were performed on plates 2 mm to 3 mm thick, using appropriate transducers to excite either the longitudinal (at 10 MHz) or the transverse (2.5 MHz) acoustic mode. The Poisson’s ratio of 0.37 is typical for precious metals. The Young’s modulus of 139 GPa to 145 GPa is comparable to that of the conventional PdRu alloy (148 GPa). It lies between those of 18 carat Au alloys (90 GPa to 110 GPa) and 950 Pt alloys (approximately 170 GPa to 210 GPa). Regarding specific stiffness, E/ρ, the PdAlRu alloys with

1000 Rm, MPa

1200

800 Rp0.2, MPa

1000

600 400 200

400 200

0

0 CW

An

AH

Vickers harness, HV

50 40 A50, %

800 600

30 20 10 0 CW

An

AH

CW

An

AH

CW

An

AH

350 300 250 200 150 100 50 0

PtRuGa

PdRu

AuPdCu

5N red gold

PdAl2.8Ru1.7

PdAl0.9Ru3.6

3N yellow gold

Fig. 6 Comparison of mechanical properties of two PdAlRu alloys with commonly used precious metal alloys: a 950 Pt alloy (PtRuGa); a 950 Pd alloy (PdRu); a 13 wt.% Pd-containing 18 carat white gold (AuPdCu); 3N yellow gold; and 5N red gold. The comparison is made for 75% cold-worked (CW), annealed (AN), and age-hardened (AH) materials. Rm = tensile strength; Rp0.2 = conventional yield strength; A50 = fracture strain; HV = Vickers hardness


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Table II

Density, Young’s Modulus and Poisson’s Ratio of PdAlRu Alloys Alloy

State

Density,

Young’s modulus,

Poisson’s ratio,

ρ, g cm–3

E, GPa

ν

Pd95.5Al2.8Ru1.7

Annealed

10.8

139

0.37

Pd95.5Al0.9Ru3.6

Annealed

11.4

145

0.37

densities, ρ, in the range 10.5 g cm–3 to 11.6 g cm–3 slightly exceed Pt alloys (ρ ≥ 20 g cm–3) and clearly outperform Au alloys (ρ ≥ 15 g cm–3).

Colour The CIELab colorimetric indices L* (lightness), a* (red-green chromaticity index) and b* (yellowblue chromaticity index) of polished samples were determined using a spectrophotometric colorimeter (Konica Minolta CM-3610d spectrophotometer) (16). The measurement was carried out in a standard configuration with D65 illumination, a 10º observer, and in specular component included (SCI) mode. The ideal white would return (L*/a*/b*) indices of (100/0/0). The measured values are (84/1/4.5) for Pd95.5Al2.8Ru1.7 and (86/0.9/4.1) for Pd95.5Al0.9Ru3.6. These values are comparable to those of standard 950 PdRu, and closer to the colour of the platinum alloy 950 PtRu (87.7/0.7/3.4) than to ‘premium’ 18 carat white gold (82/> 1.5/> 6). However, the colour indices of the two PdAlRu alloys suggest that the effect of aluminium is to add a slight yellowish tinge and to somewhat diminish the brightness. For the classification of white gold alloys, a simple colour grading system based on the ASTM D1925 (1988) yellowness index (YI) has recently been proposed (17). Within this system, the lower the YI the whiter the alloy. The whitest metals and alloys such as silver or 950 PtRu have values of YI ≈ 8. The PdAlRu alloys attain YI ≈ 10, which is comparable to pure Pd or Pt. White gold alloys, in contrast, have substantially higher indices, at YI ≥ 15.

Workability Figure 4 shows another characteristic feature of the two PdAlRu alloys: their yield strengths do not


steadily approach their tensile strengths with increasing cold work. Rather, the gap between the two parameters remains relatively large, thus facilitating the forming of complex and asymmetric shapes. The good workability of the two alloys was confirmed by the fabrication of watch cases, backs and bezels by employing rolling, stamping and annealing operations. Plate ingots with surfaces machined to eliminate possible microcracks and flaws were used as a starting material. The plates were easily rolled to over 90% reduction without intermediate annealing. In accordance with the data in Figure 5, the hardness rose by only about 40 HV upon increasing the cold work from 23% to 95% reduction. Blanks were then roughly punched out from bands of thickness 8.8 mm, followed by fine punching for improved surface finish and dimensional tolerances. The final shaping of larger series of components by progressive die stamping is in progress. The most intriguing observation during these operations was the pronounced tendency of both alloys to heat up considerably during plastic work. While heating to a certain extent is usual for rolling processes, the heating up of a disc during punching to temperatures so high that it cannot be touched by hand is extraordinary. This significant temperature rise during plastic deformation might be related to the low work hardening by promoting dynamic recovery.

Use of the Ceramic Fusion Technique with PdAlRu Alloys Inspired by the dental technique of ceramic veneering of precious metals, the feasibility of fusing coloured ceramic overlays on PdAlRu alloys for decorative purposes was investigated. In the

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dental technique, Pd-containing alloys are in fact preferred. Pd oxidises more readily than Au or Pt, which guarantees a better bonding to the ceramic. The presence of Al in the PdAlRu alloys is certainly favourable in this respect. The dental sector commercialises a broad range of ceramic materials with coefficients of thermal expansion (CTE) in the range 8 × 10–6 K–1 to 14 × 10–6 K–1 (18, 19). The CTE of Pd is 12 × 10–6 K–1, and alloying with a total of 5 wt.% Al and Ru is not expected to change this value significantly. A close match of the ceramic CTE to the metal CTE is important to avoid cracking, notably during cooling after the firing process. Two types of commercial dental ceramics were tested: VITA VM®13 veneering material for intensive or translucent colours, and the VITA Akzent® stain powder for pitch black dyeing (19). The ceramics were either applied as overlays or filled in to trench patterns machined into the PdAlRu discs. The ceramic-to-metal fusion was performed following the directions of the ceramic supplier (19). In short, it consists of preparing the metal surface by sandblasting and controlled thermal oxidation. Different ceramic layers are then applied and fired one after the other at 890ºC for one to two minutes: a first layer to promote cohesion, a second opaque layer, and a final glass-ceramic coloured layer. Additional layers may be necessary in order to fill in possible gaps produced upon firing. Figure 7 exemplifies PdAlRu discs prepared and polished by the methods described above, with differently coloured ceramic inlays. The colours are uniform and no pores or cracks are apparent.

Fig. 7 PdAlRu alloy discs with ceramic inlays

Conclusions In search of 950 Pd alloys with improved mechanical properties, PdAlRu alloys proved particularly promising. The PdAlRu alloys presented in this paper possess beneficial characteristics for applications in jewellery, and in particular in watchmaking. The palladium content of 95 wt.% is common to most countries. The PdAlRu alloys are whiter than most 18 carat white gold alloys. Furthermore, they are compatible with the dental veneering technique, which opens up the potential for decorating articles with ceramic ornaments in appealing colours. The PdAlRu alloys exhibit excellent workability and forming characteristics, similar to those of commonly used 950 Pd alloys. At the same time, they exhibit much higher strength and hardness, more comparable to those of gold or platinum alloys. Moreover, the mechanical properties can be tuned in an extended range by varying the Al:Ru ratio. Upon cold working, for a given strain, the yield stress increases much less than it does in other precious metals, while the tensile strength increases in broadly similar fashion. This characteristic imparts to the alloys enhanced plasticity and excellent workability.

References 1 S. A. Forrest and B. Clarke, ‘End-Users, Recyclers and Producers: Shaping Tomorrow’s PGM Market and Metal Prices’, in “International Platinum Conference ‘Platinum Surges Ahead’”, Sun City, South Africa, 8th–12th October, 2006, Symposium Series S45, The Southern African Institute of Mining and Metallurgy, Johannesburg, South Africa, 2006, p. 307 2 B. Libby, ‘Palladium Premieres’, MJSA Journal, March 2006, p. 35


3 “The Santa Fe Symposium on Jewelry Manufacturing Technology 2008”, ed. E. Bell, Proceedings of the 22nd Symposium in Albuquerque, New Mexico, U.S.A., 18th–21st May, 2008, Met-Chem Research Inc, Albuquerque, New Mexico, U.S.A., 2008 4 Kitco, Inc, Past Historical London Fix: http:// www.kitco.com/gold.londonfix.html (Accessed on 3rd July 2009) 5 W. Hume-Rothery, R. E. Smallman and C. W. Haworth,

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6

7

8 9 10

11

12 13

“The Structure of Metals and Alloys”, 5th Edn., The Metals and Metallurgy Trust, London, U.K., 1969, 407 pp G. Beck, in “Edelmetall-Taschenbuch”, 2nd Edn., ed. A. G. Degussa, Hüthig-Verlag, Heidelberg, Germany, 1995, p. 217 The PGM Database: http://www.platinummetalsreview.com/jmpgm/ index.jsp (Accessed on 3rd July 2009) J. R. Hirst, M. L. H. Wise, D. Fort, J. P. G. Farr and I. R. Harris, J. Less-Common Met., 1976, 49, 193 J. Evans, I. R. Harris and L. S. Guzei, J. Less-Common Met., 1979, 64, (2), P39 A. Blatter, J. Brelle and R. Ziegenhagen, PX Holding SA, ‘Alliage à Base de Palladium’, Swiss Appl. CH00032/08; 2008 P. Battaini, 8853 SpA, ‘High-Hardness Palladium Alloy for Use in Goldsmith and Jeweller’s Art and Manufacturing Process Thereof’, Italian Appl. TO2006/0086; U.S. Appl. 2008/0,063,556 H. W. King, Bull. Alloy Phase Diagrams, 1982, 2, (4), 527 F. M. Smits, Bell Syst. Tech. J., 1958, 37, 711

14 R. Hill, “The Mathematical Theory of Plasticity”, Oxford Classic Texts in the Physical Sciences, Oxford University Press Inc, New York, U.S.A., 1998, 366 pp 15 “Nondestructive Testing Handbook”, Volume 7, “Ultrasonic Testing”, eds. A. S. Birks, R. E. Green, Jr. and P. McIntire, American Society for Nondestructive Testing, Columbus, Ohio, U.S.A., 2007, 600 pp 16 “Precise Color Communication: Color Control from Perception to Instrumentation”, Product Applications, Konica Minolta Sensing Inc, Japan, 1998: http:// www.konicaminolta.com/instruments/knowledge/ color/pdf/color_communication.pdf (Accessed on 3rd July 2009) 17 S. Henderson and D. Manchanda, Gold Bull., 2005, 38, (2), 55 18 Wieland Dental online: Products: Veneering Ceramic: http://www.wieland-dental.de/produkte/ verblendkeramik/page.html?L=1 (Accessed on 3rd July 2009) 19 VITA Zahnfabrik website: http://www.vitazahnfabrik.com/ (Accessed on 3rd July 2009)

The Authors Julien Brelle graduated in Materials Science and Engineering from the École Polytechnique Fédérale in Lausanne, Switzerland (2005), with a specialisation in metal matrix composites. He is now working as a Research Engineer at PX Group, a producer of metal products for the watch, jewellery and medical sectors. He is mainly involved in the development of speciality alloys and related processing.

After his Ph.D. in Physics (1986), Andreas Blatter led a research group at the Institute of Applied Physics in Berne, Switzerland, and spent a year at the IBM Almaden Research Center, U.S.A, as a Visiting Scientist. His research was focused on non-equilibrium laser processing, thin films and metallic glasses. Since 1996, he has been the R&D Director of PX Group. His main research topics include precious metals and speciality alloys and their related technologies, as well as corrosion and biocompatibility studies.

René Ziegenhagen received his degree in Materials Science and Engineering from the École Polytechnique Fédérale in Lausanne, Switzerland (1986). He was then involved in the research of precious metals and the development of new industrial processes, such as metal injection moulding and forging, before joining Cartier in the Richemont Group as a Senior Project Manager. At Cartier, his main concerns include the quest for new materials and new production technologies to meet requirements and regulations on biocompatibility and ecotoxicity.


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DOI: 10.1595/147106709X474208

The 23rd Santa Fe Symposium on Jewelry Manufacturing Technology NOVEL MELTING APPROACH FOR 950 PALLADIUM CASTINGS SHOWS PROMISE Reviewed by Christopher W. Corti COReGOLD Technology Consultancy, Reading, U.K.; E-mail: [email protected]

The 23rd annual Santa Fe Symposium® was held in Albuquerque, New Mexico, U.S.A., from 17th–20th May 2009 (1). Attendance was down on previous years, perhaps reflecting the impact of the current recession on the jewellery industry in the U.S.A., although surprisingly representation from Europe was stronger than in previous years. Once again, the organisers had put together a strong, attractive programme covering all areas of activity, although platinum- and palladium-centred topics were fewer than last year. Having said that, palladium’s position as a relatively new metal for jewellery sustained its prominence at the conference.

The Platinum Group Metals The interest in platinum group metals (pgms) remains strong, judging by the reaction to the lucid presentation by Mark Danks (Johnson Matthey New York, U.S.A.). His topic was ‘The Precious Metal Price Equation’ and he reviewed the price history of platinum and palladium, coinciding with Platinum Week in London, U.K., and the publication of the Johnson Matthey “Platinum 2009” market review (2). 2008 was a year of mixed fortunes, with the price of platinum starting high, rising even further during the first half-year before dropping severely during the third quarter due to softening demand in both the industrial and jewellery sectors, although there was some recovery at the year end. Danks analysed the supply and demand for platinum and palladium and the reasons behind the changes compared to 2007. He covered the fall in demand from the automotive sector, the rise in exchange traded funds (ETFs) and examined trends in jewellery demand for platinum and palladium. The high price of platinum inevitably had a negative impact on jewellery demand, while demand for palladium in this sector


increased in Europe and the U.S.A., due to improved technical knowledge of the metal and its favourable price compared to gold and platinum.

Palladium On the technical side, Paolo Battaini (8853 SpA, Italy) gave another excellent presentation on the casting of 950 palladium alloys, using an innovative melting technique borrowed from the dental industry. Titled ‘Production of Hard 950 Palladium-Based Jewellery Using an Arc Melting Method under Argon Protection’, Battaini showed how employing arc plasmas for melting (as in tungsten inert gas (TIG) welding) in the investment casting of palladium jewellery can overcome some of the problems found with conventional casting processes. In particular, it enables good control of the melting and casting atmosphere as well as allowing rapid melting to the high temperatures required. Use of argon gas is preferred over helium to avoid overheating of the melt. Casting trials were carried out on a hard 950 palladium alloy containing gallium, indium and other minor alloying additions. The alloy development was described in Battaini’s earlier paper, presented in 2006 (3): in the as-cast condition, it has a Vickers hardness of 190 HV. Casting was carried out in an Orotig Srl ‘Speedcast 220MJ’ machine, which is also used to cast platinum and titanium jewellery. Casting is accomplished by rotating the chamber to gravity fill and applying an argon overpressure to the casting mould and flask. During melting, the tungsten electrode is moved over the melt in a circular motion. Three types of melting crucible were trialled: alumina, fused quartz (silica) and zirconia, along with four types of mould investment: a two-part phosphate-bonded, quick burn-out dental investment, a

198

one-part water-bonded platinum investment containing chopped glass fibres, the same without glass fibres, and a two-part phosphoric acid-bonded investment for platinum. The arc current employed was related to the melt size and casting was accomplished in about forty seconds after arc ignition. Zirconia crucibles were preferred for melting as less current is needed (due to zirconia’s lower thermal diffusivity compared to silica and alumina), allowing for better process control. Castings were evaluated for pattern filling, surface quality and defects, including cracks, fins and porosity; additionally, metallographic examination and mechanical property assessments were made. Other factors such as devesting of the castings and recastability of scrap were also examined. In general, the two-part platinum investment gave the best results for the 950 palladium alloy. Detail reproduction was good with a smooth surface (Figure 1), and there was no reaction between

metal and investment. Flask temperature (650ºC and 750ºC) made little difference to the slight oxidation observed, although if higher temperatures are used a vitreous layer may be formed. The twopart dental investment resulted in castings with heavy oxidation and hot tearing. The latter problem was also seen with the glass fibre-containing investment, suggesting that both investments have poor thermal expansion compatibility and/or too high a level of stiffness. Pattern filling was generally good with all investments, attributed to the argon overpressure applied just after pouring. Recastability was good, even with use of 100% scrap as the charge if properly cleaned. Normal casting results in large dendritic grains, but in this study metallographic examination revealed a moderate as-cast grain size of about 300 μm, with some microsegregation across dendrites. The grain size increased a little in thicker sections.

1 mm

1 mm

2 mm 2 mm

500 μm Fig. 1 As-cast surfaces of the 950 palladium alloy after water jet removal of the two-part platinum investment. Surface is smooth, with slight defects in the wax reproduced – particularly evident on the grid. (Inset: Scanning electron microscope image of the grid. The black particles are the only remaining traces of the investment material) (Courtesy of Paolo Battaini, 8853 SpA, Italy)


199

Gas porosity was noted frequently but was hardly detected after polishing. Care was needed to avoid shrinkage porosity in thick (> 3 mm) sections, but the normal precautions to prevent this occurrence in other precious metals also work for palladium alloys. Battaini noted that the feed sprues should be optimised to assist directional solidification. He concluded that arc melting proved to be a reliable method for investment casting of this 950 palladium alloy, and that short melting times and an argon atmosphere help to avoid alloy contamination. He also reiterated that the right choice of investment remains essential to obtain good results and recommended that a specific investment tailored for palladium should be developed.

Platinum On the platinum front, technology is more established and attracted less attention. However, Jurgen Maerz (Platinum Guild International, U.S.A.) gave an interesting presentation on the investment casting of 950 platinum alloys, ‘Historic Casting Methods’. This was a review of old methods used to cast platinum in the early days of jewellery making and, more specifically, of a project in which the old manual sling casting method was reproduced in a modern guise and shown to produce acceptable castings. It was well illustrated by a video clip of the whole process. It is something only likely to be used by the small craft jeweller – however, whirling hot molten platinum around one’s head may not meet modern workplace health and safety requirements!

Metallurgy and Manufacturing A number of papers were presented that covered all the jewellery precious metals: gold, silver, platinum and palladium. Starting the conference, Chris Corti (COReGOLD, U.K.) gave the third part of his ongoing ‘Basic Metallurgy’ series on ‘Cracks, Defects and Their Prevention’ (4, 5). This examined the causes of cracking and other defects commonly encountered while manufacturing jewellery. These included embrittlement by impurities and minor alloying additions such as silicon, which can manifest itself as hot tearing and quench


cracking during casting; these can occur in all four precious metals. Other causes include cracking due to shrinkage porosity, inclusions and pipes from casting, and fire cracking from annealing. Stress corrosion cracking can occur after manufacture, when the jewellery is in service. Hardness and its significance was a popular topic in 2008 (6), and it continued to attract attention in 2009. Gary Dawson (Goldworks Jewelry Art Studio, U.S.A.) examined the effect of burnishing jewellery on hardness of the surface layer for a range of materials, including 950 platinum and 950 palladium alloys. This utilised the ‘drop hardness’ test to determine hardness, which is easy to do in the absence of proper hardness testing equipment. This study concluded that, as had been found earlier, burnishing with steel media in either a rotary tumbler or vibratory machine leads to hardening of the surface, rotary tumbling having a larger effect and giving a smoother surface. The depth of hardening was lower for the 950 platinum alloy than for the 950 palladium alloy, although both saw larger relative hardness increases than the gold or silver alloys tested. Dawson noted that final polishing after burnishing could remove the hardened layer. ‘Hardness and Hardenability’ was a topic presented by John Wright (Wilson-Wright Associates, U.K.), author of the Johnson Matthey jewellery technical manual “An Introduction to Platinum” (7). He investigated the indentation hardness test and how work hardening affects the value measured, and explained why it is not easy to correlate results measured by one test with those measured by another type, or with tensile data. Improved wear, scratch and tarnish resistances of jewellery are desirable features in jewellery manufacture. Marco Actis Grande (Turin Polytechnic, Italy) spoke about ‘Transparent Coatings Applied in Jewellery: A Challenge for Success?’. Using plasma-enhanced chemical vapour deposition (PECVD), he deposited thin non-stoichiometric silicon oxide coatings on sterling silver and performed a range of corrosion, tarnish and wear tests. These showed that a 100 nm-thick coating gave the best improvement in resistance to corrosion and tarnish. Actis Grande concluded that

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PECVD can be one method to improve corrosion and tarnish resistance of sterling silver. Wear test results are awaited. These coatings may have application to the other precious metals for improved wear resistance, especially where the alloys are relatively soft. Looking to the future, Joe Strauss (HJE Company, Inc, U.S.A.) gave an excellent review of how rapid prototyping is developing into a manufacturing process, in ‘Rapid Manufacturing (RM) and Precious Metals’. Noting that computer aided design/computer aided manufacturing (CAD/CAM) and rapid prototyping are becoming familiar technologies in the jewellery industry, he looked at how these technologies are being developed into manufacturing processes and how these might relate to jewellery manufacture in the future. There are a number of RM technologies emerging, many based on metal powders as the starting material: selective laser fusing and sintering, electron beam melting, laser powder forming and selective inkjet binding. These techniques are already in use in dental, biomedical, Formula 1 motor racing and three-dimensional artwork applications, where the attraction is the ability to customise components. Strauss believes that the use of these techniques in jewellery manufacture should have the objective of utilising their key attributes, namely: reduction of lead time to market, the creation of unique shapes, the use of novel materials and the possibility for innovative design features, rather than competing with current manufacturing technologies. There are some challenges and issues, he admitted, such as quality of surface finish, affordability of equipment and material costs and availability. Investment casting is probably the most widely used manufacturing process in jewellery. It comprises many steps, starting with master models and rubber mould manufacture. Tyler Teague (Jett Research, U.S.A.) gave an excellent paper, ‘Technical Model Making (It’s Not Just the Size of Your Sprue That Counts)’, which examined various factors including the adaptation of traditional casting techniques to jewellery, in particular the use of risers, to prevent shrinkage porosity. Hubert Schuster (Consultant, Italy) looked at rubber mould manufacture in his absorbing presentation


‘Innovative Mould Preparation and Cutting for Very Thin and High Precision Items’. This involved use of different rubber compounds in parts of the mould and expert cutting after vulcanising.

General Interest Back to basics once again with Klaus Wiesner (Wieland Dental + Technik GmbH & Co KG, Germany) who gave an overview of precious metal tube manufacturing techniques and some of the problems encountered, in his presentation ‘Tube Manufacturing – Some Basics’. There were several presentations on decorative effects in jewellery: purple and blue gold alloys were discussed by Ulrich Klotz (FEM, Germany) and Jörg Fischer-Bühner (Legor Srl, Italy); a presentation on an ancient Japanese technique known as ‘mokume gane’ that bonds many layers of precious metals into a single patterned piece was given by Chris Ploof (Chris Ploof Studio, U.S.A.) (Figure 2) (8); a description of colour gradients in carat

Fig. 2 Triple white mokume gane ring, with 950 palladium alloy, 14 carat palladium white gold and silver (Courtesy of Chris Ploof Studio, U.S.A.)

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golds by gradient casting was given by Filipe Silva (University of Minho, Portugal); and a scientific study of Japanese patination techniques was presented by Cóilín Ó Dubhghaill and Hywel Jones (Sheffield Hallam University, U.K.). Other papers included a study of the practical application of some new (tarnish-resistant) sterling silvers by Mark Grimwade (The Worshipful Company of Goldsmiths, U.K.), and discussions of electromechanical polishing of silver by Alex Verdooren (Rio Grande, U.S.A.) and hot tearing in casting sterling silver by Daniele Maggian (ProGold Srl, Italy). These were followed by a review of gold-filled products by Rick Greinke (Award Concepts, Inc, U.S.A.), and by the discussion of unconventional manufacturing techniques for models and prototypes by Michael Jones (Evangel Arts, U.S.A.), age-hardenable carat golds by Grigory Raykhtsaum (Sigmund Cohn Corp, U.S.A.) and design of fire assay laboratories by Rajesh Mishra (A-1 Specialized Services and Supplies, Inc, U.S.A.).

A Lifetime Achievement Award was presented to John C. Wright, who has made a significant contribution over many years to further our knowledge and understanding in jewellery manufacture, particularly in platinum (see for example (7, 9)). Professor Wright has presented several times at the Symposium, and also wrote the World Gold Council “Technical Manual for Gold Jewellery” (10).

Concluding Remarks Interest in palladium as a new jewellery metal remains high, while platinum technology is better known and established. The conference continues to provide good coverage of general techniques in jewellery manufacture, of interest to workers in all the precious metals. The Santa Fe Symposium® proceedings are published as a book and the PowerPoint® presentations are available on CDROM. They can be obtained from the organisers (1). The 24th Santa Fe Symposium will be held in Albuquerque on 16th–19th May 2010.

References 1 The Sante Fe Symposium: http://www.santafesymposium.org/ (Accessed on 3rd August 2009) 2 D. Jollie, “Platinum 2009”, Johnson Matthey, Royston, U.K., 2009: http://www.platinum.matthey.com/ publications/Pt2009.html (Accessed on 3rd August 2009) 3 C. W. Corti, Platinum Metals Rev., 2007, 51, (1), 19 4 C. W. Corti, ‘Basic Metallurgy of the Precious Metals’, in “The Santa Fe Symposium on Jewelry Manufacturing Technology 2007”, ed. E. Bell, Proceedings of the 21st Symposium in Albuquerque, New Mexico, U.S.A., 20th–23rd May, 2007, Met-Chem Research Inc, Albuquerque, New Mexico, U.S.A., 2007, pp. 77–108 5 C. W. Corti, ‘Basic Metallurgy of the Precious Metals – Part II’, in “The Santa Fe Symposium on Jewelry

6 7

8 9 10

Manufacturing Technology 2008”, ed. E. Bell, Proceedings of the 22nd Symposium in Albuquerque, New Mexico, U.S.A., 18th–21st May, 2008, Met-Chem Research Inc, Albuquerque, New Mexico, U.S.A., 2008, pp. 81–101 C. W. Corti, Platinum Metals Rev., 2009, 53, (1), 21 “An Introduction to Platinum”, Johnson Matthey New York, U.S.A.: http://www.johnsonmattheyny.com/ technical/platinumTechManual (Accessed on 3rd August 2009) Chris Ploof Studio, Traditional Mokume Gane: http://www.chrisploof.com/traditionalpattern.html (Accessed on 3rd August 2009) J. C. Wright, Platinum Metals Rev., 2002, 46, (2), 66 J. C. Wright, “Technical Manual for Gold Jewellery – A practical guide to gold jewellery manufacturing technology”, World Gold Council, London, U.K., 1997

The Reviewer Christopher Corti holds a Ph.D. in Metallurgy from the University of Surrey (U.K.) and has recently retired from the World Gold Council after thirteen years, the last five as a consultant. During this period, he served as Editor of Gold Technology magazine, Gold Bulletin journal and the Goldsmith’s Company Technical Bulletin. He continues to consult in the field of jewellery technology and, as a ® recipient of the Santa Fe Symposium Research, Technology and Ambassador Awards, he is a frequent presenter at the Santa Fe Symposium.


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DOI: 10.1595/147106709X474226

Novel Chiral Chemistries Japan 2009 PGMs RETAIN THEIR PIVOTAL ROLE IN ASYMMETRIC CATALYSIS Reviewed by David J. Ager DSM, PMB 150, 9650 Strickland Road, Suite 103, Raleigh, NC 27615, U.S.A.; E-mail: [email protected]

The third Novel Chiral Chemistries Japan (NCCJapan) Conference and Exhibition was held in Tokyo on 18th and 19th April 2009 (1). The second meeting had been held in 2007 (2) and the first in 2006. All meetings in the series have followed a similar format, with keynote addresses and supporting lectures, although this time there were some dual presentations in which two speakers from the same company gave complementary talks on slightly different topics within a single time slot. Professor Takao Ikariya (Tokyo Institute of Technology, Japan) and his team, in particular Kyoko Suzuki, must be congratulated for the excellent job they did to ensure that the conference ran smoothly. As in previous meetings, Professor Ikariya put together an exciting mix of speakers from both academia and industry across the world. There were around 130 attendees, with the majority being from Japan. During the coffee and lunch breaks there was an exhibition by companies with products mainly associated with chiral chemistry. The exhibitors ranged from companies that provide biocatalysts and chemical catalysts including ligands, to chromatography, chemistry services and instrument manufacturers.

simultaneous use of bio- and chemocatalysis to enable dynamic kinetic resolutions (DKR) to be carried out. The initial work was performed with secondary alcohols. The readily available enzyme, Candida antarctica lipase B (CALB) (Novozym® 435), which is derived from a yeast, is used to acylate one enantiomer of a secondary alcohol. A ruthenium catalyst then racemises the unreacted enantiomer. Initially the Shvo catalyst, 1, was used but the racemisation is slow and requires heating to give acceptable reaction rates. Use of the monomeric ruthenium catalyst 2 provides faster reactions, even at ambient temperatures. Ph

O Ph

Ph Ph OC 1

O

H

Ph

Ph

Ru H Ru

Ph

CO OC CO Ph

Ph

Ph

Ph

Ru Cl

Ph 2

Ph

OC

CO

Keynote Presentations The opening keynote address was given by Professor Yoshiji Takemoto (Kyoto University, Japan) on asymmetric catalysis with multifunctional ureas. The reactions described included asymmetric versions of the Michael and Mannich reactions, hydrazination and the aza-Henry reaction with 1,3-dicarbonyl compounds, as well as Petasis-type additions to quinolines and conjugate additions to enones. The second keynote address was given by Professor Jan-Erling Bäckvall (Stockholm University, Sweden). This lecture covered his work on the


CALB provides the (R)-acetate, while a specially treated subtilisin Carlsberg enzyme gives the (S)-product ester. With 1,3-dihydroxy compounds, the selectivity of the enzyme ensures high selectivity for the (R,R)-diacetoxy product. However, due to the slow racemisation rates with the Shvo catalyst system, significant amounts of meso-products were formed with 1,4- and 1,5-diols. Use of the faster catalyst 2 alleviates this problem. Analogous uses of the concept have been employed for the DKR of chlorohydrins, amines and allenic alcohols.

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The third keynote address was given by Professor Hisashi Yamamoto (University of Chicago, U.S.A.) on the uses of Brønsted acids in organic synthesis. The emphasis of the talk was on the use of triflimide, (CF3SO2)2NH, as a superacid that can regenerate itself during a Mukaiyama aldol reaction. The use of the tris(trimethylsilyl)silyl (TTMS) group as a ‘super silyl’ group also makes the enol ether more reactive.

OMe

H2N

OMe

H2N 4 (S)-DAIPEN

Asymmetric Catalysis In addition to these keynote addresses there were fifteen other presentations. Topics included the uses of biocatalysis, transition metal catalysis and the synthesis of target molecules, among others. In line with the emphasis of this publication, those talks relating to the use of platinum group metals (pgms) have been highlighted. Fred Hancock (Johnson Matthey Catalysis and Chiral Technologies, U.K.) gave an overview of some case histories in which Johnson Matthey had looked for an appropriate catalyst to perform an asymmetric transformation. He described the advantages of chemocatalytic and enzymatic methods for the reduction of carbonyl compounds for a number of example systems. The reduction of aryl ketones can be achieved in high yield and with high enantioselectivity by the system RuCl2[(R)P-Phos][(S)-DAIPEN], 3a and 4, in a manner analogous to the method developed by Noyori (3). The use of this system with xyl-P-Phos, 3b, was illustrated for a pharmaceutical application as part of the synthesis of Nycomed’s imidazo[1,2-a]pyridine BYK-311319. The P-Phos family of ligands can also be used in the catalyst system [RuCl2(PPhos)(DMF)n] (DMF = N,N-dimethylformamide),

for the reduction of α,β- and γ,δ-enoic acids for pharmaceutical applications, such as in the preparation of an intermediate for Solvay’s SONU 20250180. α,β-Enoic acids can also be reduced by an iridium or rhodium catalyst with Me-BoPhozTM, 5, as the chiral ligand or by a rhodium–Xyl-PhanePhos, 6, system.

P(xyl)2

N PPh2 PPh

2

Fe

P(xyl)2

5 (R)-Me-BoPhozTM

6 (R)-Xyl-PhanePhos

André de Vries and David Ager (DSM, The Netherlands and U.S.A., respectively) gave a joint presentation. de Vries described the advantages of performing asymmetric hydrogenations of unsaturated carbon–carbon multiple bonds with a rhodium catalyst using the MonoPhosTM family of ligands, 7 (4). The method can be automated, which allows for rapid screening of products. R4

OMe N

3 a Ar = Ph ((R)-P-Phos) b Ar = xyl ((R)-xyl-P-Phos)

MeO

PAr2

MeO

PAr2

R5

R3

O O R5

N

P

NR1R2

R3 R4

OMe


7 MonoPhosTM family of ligands

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Higher reaction rates and enantioselectivities can be observed when two different monodentate ligands are used at the same time. This has resulted in an economical process for the preparation of part of Novartis’ renin inhibitor, Aliskiren. The phosphoramidite MonoPhosTM ligands are also useful for the reduction of carbonyl groups, including β-keto esters, with ruthenium as the metal. Iridium systems with phosphoramidites can be used to prepare phenylalanines by asymmetric hydrogenation, and also provide high selectivity in the reduction of imines. Ager discussed enzymatic methods to prepare cyanohydrins with high enantioselectivity, and the development of the industrial production of DSM’s PharmaPLETM, a recombinant pig liver esterase that can be used in pharmaceutical applications. Professor Andreas Pfaltz (University of Basel, Switzerland) continued the asymmetric hydrogenation theme with his iridium-catalysed asymmetric reduction of unfunctionalised alkenes in the presence of P,N-ligands. In addition to the well-established system 8, which can be used with a wide variety of alkene substitution patterns, the phosphinooxazolines, 9, have also proven useful, particularly with trisubstituted alkenes. For this class of reductions, it is particularly important to use a non-nucleophilic counterion for the metal, such as tetra[3,5-bis(trifluoromethyl)phenyl]borate (BArF).

O PAr2 8

2

O PAr2 N

N R

9

Ar = Ph or o-Tol

3

Ph

Kunihiko Murata (Kanto Chemical Co, Inc, Japan) described the development of the ruthenium-based asymmetric transfer hydrogenation catalyst 10 for the reduction of ketones, which removes the need for a chiral phosphine ligand. The diamine provides the asymmetry. This catalyst can also be used to carry out asymmetric Henry and Michael reactions.


R1SO2 Ph

R2

N

N H2

R1 = aryl or alkyl Ar–R2 = cymene, mesitylene or hexamethylbenzene

Ru Ph

X = Cl

X 10

Ian Lennon (Chiral Quest, Inc, U.K.) described the chemistry and uses of a number of ligand systems developed by Chiral Quest. C3-TunePhos, 11, provides excellent enantioselectivity for the reduction of β-keto esters. The analogue C3*-TunePhos, 12, extends this to ketones and α-keto esters as well as retaining its selectivity with β-keto esters. TangPhos, 13, has proven to be a useful ligand in the rhodium-catalysed reduction of dehydroamino acids, itaconates and enamides. The latter class of compounds can now be accessed from oximes by a rhodium-on-carbon-catalysed hydrogenation in the presence of acetic anhydride. The analogue of TangPhos, DuanPhos, 14, provides excellent stereoselectivity for the reduction of functionalised aryl alkyl ketones, while BINAPINE, 15, provides access to β-amino esters. Christophe Le Ret (Umicore AG & Co KG, Germany) described a different aspect of asymmetric hydrogenation: the formation of metal–ligand complexes and the influence of the metal precursor. For rhodium, an example ligand was MandyPhosTM, 16. For the asymmetric reduction of (Z)-acetamidocinnamic acid methyl ester, with Rh(nbd)2 (nbd = 2,5-norbornadiene) as the metal source, in situ formation of the catalyst or the use of the P,N-complex gave a slower hydrogenation rate than the P,P-complex system. With ruthenium, it was found that the use of bis(η5-2,4-dimethylpentadienyl)ruthenium(II), 17, was superior for complex formation with MandyPhosTM and other ferrocene-based ligands. Wataru Kuriyama (Takasago International Corp, Japan) described the synthesis of chiral alcohols by the catalytic reduction of esters. The system is based on a ruthenium–diamine complex, 18. For high enantioselectivity, the stereogenic centre has to be present in the substrate, as it is in α-alkyl, βamino, β-alkoxy, β-hydroxy and α-hydroxy esters.

205

12 C3*-TunePhos

O

O

PPh2

PAr2

PPh2

O

H P

PAr2

O

H

H

P

t t t-Bu Bu Bu t-Bu

13 TangPhos 11 C3-TunePhos Ar = Ph, 4-MePh, 3,5-di-tBuPh, 3,5-diMePh or 4-MeO-3,5-di-tBuPh

H

H

P

H

H

P

P

P

t t t-Bu Bu Bu t-Bu

15 BINAPINE

t t t-Bu Bu Bu t-Bu

14 DuanPhos NMe2

Ph Ph H2 PH N

Ph Fe

Ru

PPh2

Ru PH N Ph H PhPhPhBH 2 3

Ph Me2N

PPh2

16 MandyPhos

Ph

Ph 18

17

The key to success was performing the reactions in the absence of base. Professor Ken Tanaka (Tokyo University of Agriculture and Technology, Japan) presented on rhodium-catalysed [2 + 2 + 2] cycloadditions for the preparation of axial chiral aromatic compounds. The products can be biaryl systems or others with hindered rotation, such as benzamides. The ligands used for the reactions are BINAP, 19, and derivatives, such as H8-BINAP, 20, and SEGPHOS®, 21.

David Chaplin (Dr Reddy’s Laboratories Ltd, U.K.) described asymmetric hydroformylation reactions. Linear products are most commonly formed from an achiral hydroformylation reaction, but the product aldehydes can be substrates for a wide variety of reactions. For an asymmetric version of the reaction, regioselectivity as well as enantioselectivity must be considered, as the branched aldehyde is usually the required product because it generates the stereogenic centre. This

O

PPh22

PPh22

O

PPh2

PPh PPh22

PPh22

O

PPh22

O 19 BINAP


20 H8-BINAP

®

21 SEGPHOS

206

problem can be exacerbated if the alkene is not terminal. A screening exercise showed that the DiazaPhos-SPE diazaphospholane ligand system, 22, was the best to prepare a bistetrahydrofuran with good diastereoselectivity in the presence of a rhodium-based catalyst, Scheme I.

R 2P

NMe2

P

Fe

R 2P

23 Kephos O Ph

N H O

P

P

N

Ph

2

24 Fengphos

Fe

Ph

P R1

N

Fe

N

O H N

O H N O

Fe

P

NMe2 R1

PR2 25 Chenphos

PR2 O H

26 Jospophos

Ph

O

22 Bis(R,R,S)-DiazaPhos-SPE

Hans-Ulrich Blaser and Garrett Hoge (Solvias AG, Switzerland) gave a joint presentation. Blaser described the extensive Solvias ligand families, mainly based on the ferrocene skeleton. New ligands that have been prepared and are currently being evaluated are Kephos, 23, Fengphos, 24, Chenphos, 25, and Jospophos, 26. Hoge explained how Solvias performs ligand screenings and illustrated the methodology with a number of practical examples including the reduction of acrylic acids and ketones. Professor Bernhard Breit (Albert-LudwigsUniversität Freiburg, Germany) uses the concept of self-assembly to prepare bisphosphine ligands by dimerisation of monophosphines, such as 6diphenylphosphinyl-2(1H)-pyridinone (6-DPPon), 27. The dimeric ligand can be used to achieve high ratios of linear products in the hydroformylation of terminal alkenes. Use of an organocatalyst such

as L-proline with an aldehyde and an alkene under hydroformylation conditions provides 1,3-diols with good enantioselectivity. The self-assembly concept has been extended to chiral ligands in which the phosphorus moiety provides the asymmetry, such as 3-DMPICon, 28, and 3-BIPICon, 29. As with the reductions using DSM MonoPhosTM, the use of monodentate ligands allows for synergistic effects when two different ligands are used in asymmetric hydrogenations. Yongkui Sun (Merck & Co, Inc, U.S.A.) described some case studies on the use of asymmetric hydrogenations for drug synthesis at Merck. The final step in the synthesis of sitagliptin, 30, is an asymmetric hydrogenation to give the β-amino amide. The use of a ferrocene ligand has been superseded by the use of a ruthenium–DM-SEGPHOS® (SEGPHOS® with P(xyl)2 groups in place of PPh2) catalyst, with the β-keto amide in the presence of ammonium salicylate as the amine donor. Examples of enzymatic reactions, such as ketone reductions, HO

H

(i) Rh(CO) DiazaPhos-SPE 1. Rh(CO) Ligand 2(acac), 2(acac),

O O

PR

O

N H O N

Fe

1

OH

CO/H2CO/ H2 (ii)HCl THF, HCl 2. THF,

O

O H

endo:exo = 10:1 α:β = 8:1


Scheme I Hydroformylation reaction to prepare a bistetrahydrofuran in the presence of a rhodium-based catalyst system with DiazaPhos-SPE ligand

207

F F

NH2

P Ph 2P

N H

F

N

N

O

27 6-DPPon

30 Sitagliptin

28 3-DMPICon

R O P

O

NH O

N

N

NH

O

O

R 29 3-BIPICon (R = H)

transaminations and the formation of cyanohydrins were also given. Professor Mikiko Sodeoka (RIKEN Advanced Science Institute, Japan) described asymmetric reactions of metal enolates primarily based on the use of palladium, with DM-SEGPHOS® as the chiral ligand. A wide range of reactions give high enantioselectivities including Michael, aldol, Mannich and α-fluorination reactions. For the last class of reactions, use of N-fluorobenzenesulfonamide, (PhSO2)2NF, (NFSI) as the fluorinating agent provides the best selectivity.

CF3

in particular the use of pgm-based systems with phosphine ligands. As in the previous meetings, there was a good balance between the discovery of new methods and the industrial application of existing techniques. This conference series deserves to continue to grow and prosper and Professor Ikariya hinted that the next one might have the title Novel Chiral Chemistries Asia. I wish him well with this endeavour and look forward to another excellent meeting.

References 1

2 3 4 5

Novel Chiral Chemistries Japan 2009 (NCCJapan) Conference Programme: http://www.takasagoi.co.jp/news/2009/NCCJ2009_Program.pdf (Accessed on 27th July 2009) D. J. Ager, Platinum Metals Rev., 2007, 51, (4), 172 R. Noyori, Angew. Chem. Int. Ed., 2002, 41, (12), 2008 D. J. Ager, A. H. M. de Vries and J. G. de Vries, Platinum Metals Rev., 2006, 50, (2), 54 CPhI Japan: http://www.cphijapan.com/eng/ (Accessed on 27th July 2009)

The Reviewer

Concluding Remarks As with the other meetings in this series, NCCJapan 2009 was held just before CPhI Japan (5), allowing participants to attend both. There was sufficient time between lectures and at the banquet to allow for interaction between the participants, exhibitors and speakers. As noted above, a wide variety of methodology was covered, much associated with the use of transition metal catalysis, and


David Ager has a Ph.D. (University of Cambridge), and was a post-doctoral worker at the University of Southampton. He worked at Liverpool and Toledo (U.S.A.) universities; NutraSweet Company’s research and development group (as a Monsanto Fellow), NSC Technologies, and Great Lakes Fine Chemicals (as a Fellow) responsible for developing new synthetic methodology. David was then a consultant on chiral and process chemistry. In 2002 he joined DSM as the Competence Manager for homogeneous catalysis. In January 2006 he became a Principal Scientist.

208

DOI: 10.1595/147106709X472507

Melting the Platinum Group Metals FROM PRIESTLEY, LAVOISIER AND THEIR CONTEMPORARIES TO MODERN METHODS By W. P. Griffith Department of Chemistry, Imperial College, London SW7 2AZ, U.K.; E-mail: [email protected]

Some fifty years ago Donald McDonald wrote in Platinum Metals Review on ‘The History of the Melting of Platinum’ (1) and Leslie B. Hunt marked the event’s bicentenary in ‘The First Real Melting of Platinum: Lavoisier’s Ultimate Success with Oxygen’(2), which is also covered in the invaluable “A History of Platinum and its Allied Metals” (3). The topic is revisited and extended here, showing how oxygen, first isolated by Joseph Priestley and Carl Wilhelm Scheele, was used by Antoine Lavoisier to melt platinum. Work on the melting of the other platinum group metals (pgms) and modern methods for melting the metals are also discussed.

Early Attempts to Melt Platinum Before 1782 little more than a ‘partial agglomeration’ of platinum had been achieved, mainly by hot forging from the powder which, although it sufficed to make many platinum artefacts, did not produce homogeneous molten metal (1–3). The first to melt impure platinum may have been Henrik Theophil Scheffer (1710–1759) who in 1751 melted platinum with copper, and later arsenic, in a furnace (4). Franz Achard (1753–1821) similarly melted the metal with arsenic (5). In both cases alloys of platinum, rather than pure platinum, are likely to have been melted. In 1775 Pierre Macquer (1718–1784) and Antoine Baumé

(1724–1804) unsuccessfully attempted to melt platinum in a porcelain crucible over a wood fire. Macquer and others (later including Lavoisier) then tried with burning glasses: a 56 cm diameter concave mirror which focused the sun’s rays quickly melted iron but platinum gave only silverywhite glistening particles – the product probably contained impurities of carbon which lowered its melting point (1). In 1774 a magnificent 1.2 m diameter burning glass filled with alcohol was mounted on a carriage and installed in the Jardin de l’Infante, Paris, France: it melted many materials, but not platinum (1, 6). An illustration of this device is shown in Figure 1 (3). Fig. 1 The large burning glass built for the Académie Royale des Sciences and used in an early attempt to melt platinum (3)


209

Priestley, Scheele and the Discovery of Oxygen

Lavoisier, Oxygen and the Melting of Platinum

Joseph Priestley (1733–1804) was born in Fieldhead, Birstall, near Leeds in the U.K., and died in Philadelphia, U.S.A. He was better known in the eighteenth century for his radical religious and political beliefs; opposition to these and his enthusiasm for the French Revolution led him to leave the U.K. in 1794. We remember him for his science: photosynthesis, optics, electrostatics, biology and physiology and above all chemistry (7). He discovered many new ‘airs’ – N2O, NO, NO2, CO, SO2, NH3 and SiF4 – and investigated HCl, SO3, Cl2, PH3 and N2. He discovered oxygen on 1st August 1774, by heating mercuric oxide (HgO) with a burning glass, and showed that it supported combustion (8–11). He called it ‘dephlogisticated air’, believing in phlogiston, the alleged principle of combustion, to the end. Phlogiston features in one of his last papers, which also describes experiments on dissolving platinum in aqua regia (12). In October 1774, travelling in France with his patron the statesman Lord Shelburne, Priestley dined with Lavoisier and told him that he had obtained ‘a new kind of air’ by heating HgO (11). Carl Wilhelm Scheele (1742–1786), a Swedish pharmacist for whom chemistry was a rewarding hobby, rivals Priestley in the extent of his discoveries. He was the first to isolate chlorine (in 1774), HF and HCN, and did fundamental work on NH3, HCl, compounds of Ba, Mn, Mo, Ce, P and on several organic compounds. He made oxygen between 1773 and 1775 by heating MnO2, KNO3, HgO, HgCO3, MgNO3 or Ag2CO3, calling it ‘vitriol air’ (aer vitrolicus) or ‘fire air’ (aer nudus); he too was a phlogistonist until he died. His paper on oxygen was submitted in 1775 but not published until 1777 (13) so Priestley did not know of his work. Lavoisier did know, however. On 12th April 1774, he sent two copies of his “Opuscules Physique et Chimique” to Stockholm with a copy for Scheele. In September 1774 Scheele wrote thanking him and told him how to make ‘fire air’ from silver carbonate and a burning glass. His letter was rather vague and Lavoisier did not reply (14).

Antoine Lavoisier (1743–1794) is a supreme figure in chemistry, a pivotal contribution being his refutation of the phlogistic theory (10, 15, 16). There is some controversy as to whether Lavoisier discovered oxygen independently (10, 17, 18) – he was not averse to letting people think this. However, in his paper on the melting of platinum (19) Lavoisier did grudgingly allude to Priestley’s priority: “...cet air, que M. Priestley a découvert à peu-près dans la même temps que moi, & je croi même avant moi…” (…this air, which M. Priestley discovered about the same time as I, and I believe even before me…) – although some of his later publications omit the last phrase. Unlike Priestley, however, he began to understand the real significance of oxygen. In 1778 he refers to a principe oxygine (20), and in the first edition of the 1789 edition of his textbook (21) – after melting platinum – he refers to oxygène, from οξυζ (acide) and γενηζ (j’engendre – ‘I beget’ or ‘I generate’). He believed oxygen to be an element which was a constituent of all acids.


Lavoisier’s Melting of Platinum Priestley never attempted to melt platinum with ‘dephlogisticated air’ but the idea did occur to his friend, the Reverend John Michell (1724–1793), who wrote to him that “possibly platina might be melted by it”, recollected by Priestley in his book of 1775 (8) which Lavoisier may have read. In April 1782 Lavoisier directed a stream of oxygen from his caisse pneumatique (a storage device capable of producing a stream of hydrogen, oxygen or both, shown in Figure 2 (3)) onto hot hollowedout charcoal containing powdered platinum. It is not clear from his paper whether it was solely oxygen or a hydrogen-oxygen mixture: he had means of producing and storing both gases. He reported to the Académie des Sciences on 10th April 1782, that “...le platine est fondue complètement, et les petits grenailles se sont reunités en un globule parfaitement rond…” (...the platinum melts completely, and the particles united in a perfectly round globule...) (19). On 6th June 1782, Lavoisier demonstrated his discovery at the Académie to a visiting Russian

210

Fig. 2 A drawing by Madame Marie Anne Paulze Lavoisier of the apparatus designed by Lavoisier to burn continuous streams of oxygen and hydrogen (3)

nobleman. Benjamin Franklin (1706–1790), a friend and supporter of the often penniless Priestley, was also present, writing to Priestley that: “Yesterday the Count du Nord was at the Academy of Sciences, when sundry Experiments were exhibited for his Entertainment; among them, one by M. Lavoisier, to show that the strongest Fire we yet know, is made in a Charcoal blown on with dephlogisticated air. In a Heat so produced, he melted Platina presently, the Fire being much more powerful than that of the strongest burning mirror” (22), Figure 3 (3). Although neither Lavoisier, Priestley nor Scheele could have realised it, the ability of oxygen to support combustion, a process which emits the

degree of intense heat needed to melt platinum, arises largely from the intrinsic weakness of its O–O bond (496 kJ mol–1) (23). This weakness and consequent facile bond cleavage arises from electron lone pair-lone pair repulsions between the atoms in the O2 molecule. The heat emitted from, for example, charcoal burning in an H2-O2 mixture arises from the formation of the much stronger C=O bonds in CO2 and O–H bonds in H2O which are the products of combustion.

Later Methods for Melting Platinum and the Other PGMs Lavoisier’s method was not suited to large-scale production of molten platinum. In 1816 William Fig. 3 The concluding paragraph of Benjamin Franklin’s letter to Priestley, dated 7th June 1782, the day after Lavoisier demonstrated his technique for melting platinum at the Académie (3)


211

Hyde Wollaston (3) wrote to the Cambridge mineralogist Edward Clarke (1769–1822), suggesting that he might try to melt iridium and the native alloy osmiridium. Clarke used a blowpipe with an H2-O2 mixture. Despite several explosions he melted 0.5 ounces of the metal, writing that it melted more quickly than did lead in a fire (24). He also melted palladium, rhodium, iridium and native osmiridium (25). Another early claim was made for melting of rhodium by a ‘hydro-pneumatic blow pipe’ (26). A different approach was to fuse the metal by placing it between the poles of a large voltaic battery. John Frederic Daniell (1790–1845), using seventy large copper/zinc-sulfuric acid cells in series, melted platinum, rhodium, iridium and native osmiridium (27). The work of Henri Sainte-Claire Deville (1818–1881) and Jules Henri Debray (1827–1888) led the way to large-scale production of molten platinum. Their furnace used two large hollowedout blocks of lime containing the metal, fired by a coal gas-oxygen mixture; the refractory lime absorbed the slag formed by oxidation of base metal impurities. They melted a 600 g sample of platinum in 1856 (28, 29), and this remained the method of choice for melting platinum until induction furnaces became available in the early twentieth century. In 1855 George Matthey (1825–1913) visited the Paris Exhibition of 1855 and there met Debray, who in 1857 offered him the British rights for his method for melting platinum. By 1861 the process was in commercial use by Johnson Matthey and Company at Hatton Garden in London, U.K. In 1862 Deville came to London, and with Matthey melted a huge 100 kg ingot of platinum. The production of platinum, in the hands of Johnson Matthey, passed from a labora-

tory procedure to a full-scale operation, making the metal available worldwide. Michael Faraday (1791–1867) tried but failed to persuade Deville to demonstrate his method at the Royal Institution of Great Britain. Instead, in one of his last discourses there, entitled ‘On Platinum’, Faraday demonstrated its melting by using a ‘voltaic battery’, mentioning that “if you go into the workshops of Mr. Matthey [you will] see them hammering and welding away [at platinum]…”. He noted that five of the six pgms had been melted, the exception being osmium. He wrote that ruthenium has the highest melting point, followed by iridium, rhodium, platinum and finally palladium (30). Faraday also referred to platinum in his celebrated “Chemical History of a Candle” (31).

Melting Points of the PGMs It was not until the late nineteenth and early twentieth centuries that reliable pyrometers were devised for determining melting points (32, 33). Table I lists modern values for their melting and boiling points (34); osmium has the highest values for both (35).

Current Methods for Melting the PGMs Early methods for melting the pgms used blowpipe procedures, while Daniell used electricity. These days the same basic procedures are still used, albeit with newer techniques. Oxy-hydrogen or oxy-propane blowpipes or torches are still in use for bench-scale repair of platinum jewellery (36, 37), and certainly temperatures as high as 2500ºC and probably higher can be reached. Three principal methods, all electrical, are currently used to melt the pgms for industrial use and

Table I

Melting and Boiling Points of the Platinum Group Metals (ºC) (34, 35) Ru

Rh

Pd

Os

Ir

Pt

m.p.

2333

1963

1555

3127 ± 50

2446

1768

b.p.

4319 ± 30

3841 ± 90

2990 ± 50

5303 ± 30

4625 ± 50

3876 ± 20


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for large-scale jewellery manufacture (see Figure 4). Induction heating, derived from Faraday’s discovery in 1831 (38) of electrical induction, uses high-frequency alternating current passed through a water-cooled copper coil surrounding a refractory crucible containing the metal sample. Electron beam heating uses a refractory cathode, often tungsten or molybdenum: the electrons from this are accelerated in vacuo by a high-voltage direct current source to the metal (which becomes the anode) in a refractory container, the beam being steered by a magnetic field. Energies developed can reach 150 keV, and material can be melted at temperatures above 2100ºC. Finally, in arc melting, which can be traced back to Humphry Davy’s early experiments with a voltaic pile, the arc is struck under argon between a tungsten cathode and the metal which rests on a water-cooled copper anode. A direct current potential of 50 V to 80 V and a current of several hundred amperes is commonly used. The technique melts tungsten

(which has a melting point of 3422ºC), and so can melt all six pgms. These methods have been well described, although without reference to pgms (39), and there is a recent history of the induction method (40). For larger quantities of platinum or palladium (1 kg to 20 kg), induction heating is the quickest and most effective procedure. The metal charge is held in alumina or zirconia crucibles and is typically melted in air since oxidation is not a problem for these metals. Graphite or copper alloy moulds form the ingots and the molten metal is poured by an automated procedure. For the higher-melting iridium and rhodium, induction heating is less suitable. For these, arc melting is used for smaller quantities, usually less than 1 kg, and is effected in an inert gas atmosphere with the charge held in a water-cooled copper alloy mould. A tungsten cathode generates and maintains the arc, which is moved over the metal to melt and consolidate it. Electron beam Fig. 4 Industrial casting of molten platinum. Image courtesy of Johnson Matthey Noble Metals


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melting is used to make larger ingots: an evacuated chamber is used under a vacuum in excess of 10–4 Torr, with the metal held in water-cooled copper alloy moulds as for arc melting. As with the latter technique, several melting sequences are required with the ingot being turned over several times to ensure complete and even melting. Ingot sizes are typically between 2 kg and 15 kg (41). There is a recent paper in this Journal providing information on the melting of iridium (42).

Conclusions The discovery and production of gaseous oxygen, by Scheele and Priestley, allowed the first melting of pure platinum by Lavoisier in the late

18th century. The other platinum group metals were melted during the early 19th century, and by the mid-19th century commercial-scale production of platinum had become possible for the first time. The methods developed during this period remained in use until the early 20th century, when modern methods of industrial scale production using electrical heating became possible.

Acknowledgements I am grateful to the editorial and technical staff of Johnson Matthey for information on modern procedures for melting the pgms, and to Dr Max Whitby, Imperial College London, U.K., for general advice on these aspects.

References 1 D. McDonald, Platinum Metals Rev., 1958, 2, (2), 55 2 L. B. Hunt, Platinum Metals Rev., 1982, 26, (2), 79 3 D. McDonald and L. B. Hunt, “A History of Platinum and its Allied Metals”, Johnson Matthey, London, U.K., 1982 4 H. T. Scheffer, Kungl. Vetensk. Akad. Handl., 1752, 13, 269–276 5 F. K. Achard, Nouv. Mém. Acad. R. Sci. Berlin, 1781, 12, 103 6 J. C. P. Trudaine de Montigny, P. J. Macquer, L. C. Cadet, A. Lavoisier and M. J. Brisson, Mém. Acad. R. Sci., 1774, 88, 62 7 “Joseph Priestley: A Celebration of His Life and Legacy”, eds. J. Birch and J. Lee, The Priestley Society, Birstall, South Yorkshire, U.K., 2007 8 J. Priestley, “The Discovery of Oxygen, Part 1”, Experiments by Joseph Priestly, LL.D. (1775); Alembic Club Reprints, No. 7, W. F. Clay, Edinburgh, 1894, p. 8 9 W. P. Griffith, Notes Rec. R. Soc. Lond., 1983, 38, (1), 1 10 W. H. Brock, “The Fontana History of Chemistry”, Fontana Press, London, U.K., 1992, 744 pp 11 J. Priestley, “The Doctrine of Phlogiston Established, and That of the Composition of Water Refuted”, 2nd Edn., Printed by Andrew Kennedy for P. Byrne, Philadelphia, U.S.A., 1803 12 J. Priestley, Trans. Am. Phil. Soc., 1802, 4, 1 13 C. W. Scheele, “Chemische Abhandlung von der Luft und dem Feuer”, M. Swederus, Upsala and Leipzig, 1777; ‘Chemical Treatise on Air and Fire’ in L. Dobbin (translated into English), “Collected Papers of Carl Wilhelm Scheele”, G. Bell & Sons, Ltd, London, 1931; See also Alembic Club Reprints, No. 8, The Alembic Club, Edinburgh, 1906


14 U. Bocklund, ‘A Lost Letter from Scheele to Lavoisier’, Lychnos, 1957–58, 39 15 A. Lavoisier, Mém. Acad. R. Sci., 1775, 429 (issued in 1778); Reprinted in “Œuvres de Lavoisier”, Imprimerie Impériale, Paris, 1862, Vol. 2, p. 122 16 A. Lavoisier, Mém. Acad. R. Sci., 1783, 505 (issued in 1786); Reprinted in “Œuvres de Lavoisier”, Imprimerie Impériale, Paris, 1862, Vol. 2, p. 623 17 J. Priestley, “Experiments and Observations on Different Kinds of Air”, 2nd Edn., Printed for J. Johnson, London, U.K., 1784, Vol. 2, p. 34 18 S. J. French, J. Chem. Educ., 1950, 27, 83 19 A. Lavoisier, Mém. Acad. R. Sci., 1782, 457 (issued in 1785); Reprinted in “Œuvres de Lavoisier”, Imprimerie Impériale, Paris, France, 1862, Vol. 2, p. 423 20 A. Lavoisier, Mém. Acad. R. Sci., 1778, 535 (issued in 1781); Reprinted in “Œuvres de Lavoisier”, Imprimerie Impériale, Paris, France, 1862, Vol. 2, p. 248 21 A. Lavoisier, “Traité Eléméntaire de Chimie”, 1st Edn., Cuchet, Paris, France, 1789, Vol. 1, p. 48 22 “The Writings of Benjamin Franklin”, ed. A. H. Smyth, in 10 volumes, Macmillan, London, U.K., 1906, Vol. VIII, p. 453 23 H. M. Weiss, J. Chem. Educ., 2008, 85, (9), 1218 24 E. D. Clarke, Thomson’s Ann. Philos., 1817, 9, 89 25 E. D. Clarke, “The Gas Blow-Pipe or, Art of Fusion by Burning the Gaseous Constituents of Water”, printed by R. Watts for Cadell & Davies, London, 1819 26 J. Cloud, Trans. Am. Phil. Soc., 1818, 1, 161 27 J. F. Daniell, Phil. Trans. R. Soc. Lond., 1839, 129, 89 28 H. Sainte-Claire Deville, Ann. Chim. Phys., 1856, 46, (3), 182 29 H. Sainte-Claire Deville and H. J. Debray, Comptes Rendus Acad. Sci., Paris, 1857, 44, 1101

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30 M. Faraday, Chem. News, 1861, 3, 136 31 M. Faraday, “A Course of Six Lectures on the Chemical History of a Candle: to Which is Added a Lecture on Platinum”, ed. W. Crookes, Griffin, Bohn, and Company, London, U.K., 1861, p. 173 32 H. L. Callendar, Philos. Mag., 1899, 47, 191 33 Circular of the National Bureau of Standards, No. 7, U.S. Department of Commerce, Washington, D.C., U.S.A., 1910 34 J. W. Arblaster, Platinum Metals Rev., 2007, 51, (3), 130 35 J. W. Arblaster, Platinum Metals Rev., 2005, 49, (4), 166 36 Platinum Guild International, Technical Articles: http://www.platinumguild.com/output/Page2414.asp

(Accessed on 21st July 2009) 37 Platinum Guild International, Technical Videos: http://www.platinumguild.com/output/Page1749.asp (Accessed on 21st July 2009) 38 M. Faraday, Phil. Trans. R. Soc. Lond., 1832, 122, 125 39 A. C. Metaxas, “Foundations of Electroheat: A Unified Approach”, John Wiley & Sons, Chichester, U.K., 1996 40 A. Mühlbauer, “History of Induction Heating and Melting”, Vulkan Verlag, Essen, Germany, 2008 41 Johnson Matthey Noble Metals, Private communication, 20th March 2009 42 E. K. Ohriner, Platinum Metals Rev., 2008, 52, (3), 186

The Author Bill Griffith is an Emeritus Professor of Chemistry at Imperial College, London, U.K. He has much experience with the platinum group metals, particularly ruthenium and osmium. He has published over 270 research papers, many describing complexes of these metals as catalysts for specific organic oxidations. He has written seven books on the platinum metals, and is currently writing another on oxidation catalysis by ruthenium complexes. He is the Secretary of the Historical Group of the Royal Society of Chemistry.


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DOI: 10.1595/147106709X475315

PGM HIGHLIGHTS Progress in Ruthenium Complexes for Dye Sensitised Solar Cells The need to move towards a low carbon economy has led to unprecedented interest in renewable energy sources, including solar power. One type of solar cell, the dye sensitised solar cell (DSSC), first reported in 1991 by Michael Grätzel and coworkers at the Ecole Polytechnique Fédérale de Lausanne (1), is a photoelectrochemical device which contains ruthenium in the photoanode and platinum in the counter electrode. It therefore represents another example of a platinum group metal-based sustainable technology. In this review, DSSC technology is briefly discussed to provide some context for selected examples of recent patent activity.

Background Historically, conventional solar cells have relied on a solid semiconductor to perform the dual function of light absorption and charge conduction, imposing strict requirements on the composition and purity of materials used (2). DSSCs, by contrast, use a monolayer of photosensitive ruthenium-based dye adsorbed on a thin layer of nanocrystalline titanium dioxide (TiO2) to harvest light and, as a result, have comparatively low manufacturing costs. They can take the form of thin, flexible and transparent sheets, making them useful in applications such as building-integrated power sources (3). Furthermore, they perform effectively in dim and diffuse light (1), allowing for use indoors and in mobile electronic devices. These advantages largely offset the lower efficiency of DSSCs, which stands at a record of 10% to 11% (3–5) – significantly lower than the 15% to 18% achieved by the widely-used polycrystalline silicon cell (6). Efforts are continually being undertaken to improve the efficiency and hence the competitiveness of the technology. Overall cell efficiency is subject to a number of factors, but fundamental considerations relating to the dye are: firstly, how efficiently the molecules absorb incident photons; secondly, how efficiently these photons are converted to electron-hole pairs;


and thirdly, how effectively charge separation and collection occurs (2). The most efficient DSSCs demonstrated to date have all been based on ruthenium dyes developed by the Grätzel group: the N3, N719 and ‘black’ dyes (4) (Figure 1 (4, 7)). As well as superior light harvesting properties and durability, a considerable advantage of these dyes lies in the metal-ligand charge transfer (MLCT) transition, through which the photoelectric charge is injected into the TiO2. For these ruthenium complexes, this transfer takes place at a much faster rate than the back reaction, in which the electron recombines with the oxidised dye molecule rather than flowing through the circuit and performing work (2). Conversion efficiency of absorbed photons is also very high, and offers little room for improvement (2, 8). Therefore, continued research efforts are largely focused on improving the absorption of incident light. This can be achieved by manipulating the dye’s molecular structure to either increase the degree of absorption of photons in the functional wavelength range (as measured by the molar extinction coefficient, ε), or to extend the functional range – ideally, to within the near infrared (N-IR) region (9). Here, we have selected three patents, all claiming novel ruthenium complexes for application to DSSCs, to demonstrate strategies currently being investigated in this area.

Novel Ruthenium Dye Complexes The first example, filed by Dongjin Semichem Co, Ltd, South Korea (7), claims a number of new complexes based on the N3 structure. The structure has been altered by replacing one or both of the COOH groups on at least one of the bipyridyl ligands with a range of more highly π-conjugated moieties. The absorption spectra of six examples of the new complexes are presented, and the values of ε for three of the new dyes indicate a significant improvement in absorption: in one embodiment ε = 22,640 M–1 cm–1 at 533 nm, compared to values of between 14,000 M–1 cm–1 and 15,000 M–1 cm–1 for

216

COOH

COOTBA

COOH

HOOC

COOH

HOOC

N

N N

N

N

N

Ru N

Ru

S

N

N

N

C

COOH

C

S

COOTBA

C

COOH

S

N3 dye

N

N

C

S

N719 dye

COOTBA

TBAOOC N N

N Ru

Black dye N

N

N

C S

C S

C

TBA = tetrabutylammonium cation

S

Fig. 1 Structures of the ruthenium-based dyes N3, N719 and ‘black dye’ developed by the Grätzel group (4, 7)

N3 and N719 at ~ 535 nm (8, 10). In two other embodiments, ε values of ~ 21,000 M–1 cm–1 to 22,500 M–1 cm–1 are achieved at wavelengths longer than 550 nm, indicating a shift towards longer wavelengths. These improvements do not appear to translate into increased cell efficiency and values given for short-circuit current density (Jsc) and open circuit voltage (Voc) are lower than for the established dye. However, an interesting point to note is the possibility of using a combination of dyes, an approach which may allow greater flexibility in optimising both absorption and range. An application filed by Turkiye Sise ve Cam Fabrikalari AS, Turkey (11), aims in one embodi-

ment to increase ε through extended π-conjugation and a double core. A ruthenium dimer structure is claimed, designated K20 (Figure 2) and described as having ε = 22,000 M–1 cm–1. The wavelength at which this measurement is taken is not given, although elsewhere the authors show that the longest-wavelength absorption peak occurs at 520 nm. This ε value is again higher than values for N3 and N719 at similar wavelengths. Overall efficiency is also good, being comparable to the existing dyes. The technique of increasing conjugation through the use of larger and more complex ligands is again demonstrated by a patent granted in 2009 to inventors from Everlight Chemical COOH

COOH

COOH

HOOC

H 3C

N N

N N S

N

N

N Ru N

N H 3C

CH3

N C

C S

N

N

N

Ru C

CH3

K20

N C S

S

Fig. 2 Structure of a novel ruthenium dimer dye complex (11)


217

Industrial Corp (U.S.A.) and Academia Sinica in Taiwan (12). The complexes claimed here are also based on N3, with one of the ligands modified to a structure with additional aromatic rings and, in some embodiments, containing alkyl chains. The inventors present the results of comparative tests of one of the complexes (shown in Figure 3) against N719: at the longest peak wavelength (~ 530 nm), ε is increased to 14,007 M–1 cm–1 (from 12,617 M–1 cm–1 quoted for N719) and a slight redshift in the absorption spectrum is seen. The values claimed for Jsc and Voc are very similar to those achieved using N719, and the overall cell efficiency is also comparable to the existing dyes.

achieved in the patents discussed here holds promise for increased cell efficiency, which may be realised with further refinements. With DSSCs now at the pilot scale and seeing increasing commercial investment (18–21), developments in this area will be watched with interest. M. RYAN

References 1 2 3 4 5

COOH

6 HOOC

7

N N

N Ru N C S

N

N

C S

Fig. 3 A modified complex based on the ruthenium dye N3 (12)

8 9 10

11

Concluding Remarks It is clear that research into dyes for DSSCs is progressing and new ruthenium-based structures continue to be reported. Although alternative dyes have been developed, including non-metal organic dyes (13) and dyes based on iron and zinc (14, 15), these have so far proved inferior to the ruthenium dyes (4). Dyes formulated from platinum and iridium complexes are also showing some promise (16, 17), but this research is still in the early stages. With this in mind, the most promising current strategy is to increase the efficiency of light absorption at the molecular level by modifying or enhancing the established ruthenium-based dyes, which still hold their place at the forefront of the technology. The improved light absorption


12 13 14 15

16 17 18 19 20 21

B. O’Regan and M. Grätzel, Nature, 1991, 353, (6346), 737 M. Grätzel, Platinum Metals Rev., 1994, 38, (4), 151 M. Grätzel, Innovation, 2007, 7, (3), cover story Z. Jin, H. Masuda, N. Yamanaka, M. Minami, T. Nakamura and Y. Nishikitani, J. Phys. Chem. C, 2009, 113, (6), 2618 Md. K. Nazeeruddin, P. Péchy, T. Renouard, S. M. Zakeeruddin, R. Humphry-Baker, P. Comte, P. Liska, L. Cevey, E. Costa, V. Shklover, L. Spiccia, G. B. Deacon, C. A. Bignozzi and M. Grätzel, J. Am. Chem. Soc., 2001, 123, (8), 1613 K. Bullis, ‘More Efficient, and Cheaper, Solar Cells’, Technology Review, MIT, U.S.A., 14th September 2009: http://www.technologyreview.com/energy/23459/ H. Bae, C. Lee, J. Baek and H. Yang, Dongjin Semichem Co Ltd, ‘Novel Ru-Type Sensitizers and Method of Preparing the Same’, World Appl. 2009/082,163 M. K. Nazeeruddin, A. Kay, I. Rodicio, R. HumphryBaker, E. Müller, P. Liska, N. Vlachopoulos and M. Grätzel, J. Am. Chem. Soc., 1993, 115, (14), 6382 Y. Liu, H. Shen and Y. Deng, Front. Mater. Sci. China, 2007, 1, (3), 293 Md. K. Nazeeruddin, S. M. Zakeeruddin, R. HumphryBaker, M. Jirousek, P. Liska, N. Vlachopoulos, V. Shklover, C.-H. Fischer and M. Grätzel, Inorg. Chem., 1999, 38, (26), 6298 S. Icli, C. Zafer, K. Ocakoglu, C. Karapire, B. Yoldas, Y. Teoman and B. Kuban, Turkiye Sise ve Cam Fabrikalari AS, ‘Novel Ruthenium Complex PhotoSensitizers for Dye Sensitized Solar Cells’, World Appl. 2009/078,823 J.-T. Lin, Y.-C. Hsu, Y.-S. Yen and T.-C. Yin, Everlight USA, Inc and Academia Sinica, ‘Ruthenium Complex’, U.S. Patent 7,538,217; 2009 K.-J. Jiang, K. Manseki, Y. Yu, N. Masaki, J.-B. Xia, L.-M. Yang, Y. Song and S. Yanagida, New J. Chem., 2009, 33, (9), 1973 S. Ferrere, Inorg. Chim. Acta, 2002, 329, (1), 79 Q. Wang, W. M. Campbell, E. E. Bonfantani, K. W. Jolley, D. L. Officer, P. J. Walsh, K. Gordon, R. Humphry-Baker, Md. K. Nazeeruddin and M. Grätzel, J. Phys. Chem. B, 2005, 109, (32), 15397 E. A. M. Geary, L. J. Yellowlees, L. A. Jack, I. D. H. Oswald, S. Parsons, N. Hirata, J. R. Durrant and N. Robertson, Inorg. Chem., 2005, 44, (2), 242 E. Baranoff, J.-H. Yum, M. Grätzel and Md. K. Nazeeruddin, J. Organomet. Chem., 2009, 694, (17), 2661 Dyesol: http://www.dyesol.com/ G24 Innovations: http://www.g24i.com/ 3GSolar Ltd, Solar Energy Modules: http://3gsolar.com/ Solaronix SA: http://www.solaronix.com/

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DOI: 10.1595/147106709X474361

“PEM Fuel Cell Electrocatalysts and Catalyst Layers: Fundamentals and Applications” EDITED BY J. ZHANG (NRC Institute for Fuel Cell Innovation, Canada), Springer-Verlag London Ltd, Guildford, Surrey, U.K., 2008, 1137 pages, ISBN 978-1-84800-935-6, £121.50, €134.95, U.S.$209.00 (Print version); e-ISBN 978-1-84800-936-3, DOI: 10.1007/978-1-84800-936-3 (Online version)

Reviewed by Gregory J. Offer Department of Earth Science and Engineering, South Kensington Campus, Imperial College, London SW7 2AZ, U.K.; E-mail: [email protected]

“PEM Fuel Cell Electrocatalysts and Catalyst Layers: Fundamentals and Applications”, edited by Jiujun Zhang, is an excellent book. The editor is an experienced electrochemist with twenty-four years of experience, nine in fuel cells, and is the Technical Leader in Catalysis at the National Research Council Institute for Fuel Cell Innovation in Canada. Zhang states in his introduction that a comprehensive and in-depth book that focuses on both fundamental and application aspects of polymer electrolyte membrane (PEM) fuel cell electrocatalysts and catalyst layers is definitely needed. I agree, PEM fuel cells have made major advances in recent years, and have begun to enter their eagerly-anticipated commercialisation phase (1). However, this has brought new challenges, requiring electrochemists to work much more closely with engineers to optimise systems for specific applications. Therefore I read this book eagerly, hoping that the authors had managed to write a fundamental electrochemistry book that was readable by an informed engineer. I believe they have succeeded in this, and in this short review I have discussed a few key points which should illustrate this. The book is split into useful chapters, a number of them identifying and discussing mitigation strategies for some of the most significant barriers remaining to the wider adoption of PEM fuel cells, such as Chapter 17 on ‘Reversal-tolerant Catalyst Layers’. Other chapters introduce more fundamental electrochemical concepts such as adsorption, activation energies and thermodynam-


ics, which are discussed in Chapter 5, ‘Application of First Principles Methods in the Study of Fuel Cell Air-Cathode Electrocatalysis’. The level of thoroughness and detail is also impressive: for example, Chapter 16 on ‘CO-tolerant Catalysts’ alone has almost 450 references. This chapter describes both the fundamental concepts and reaction mechanisms necessary to understand the problem of carbon monoxide ‘poisoning’ of fuel cell catalysts – in particular the bifunctional mechanism of carbon monoxide tolerance exhibited by platinum-ruthenium alloy catalysts, where ruthenium provides the ability to generate hydroxyl species to oxidise CO at lower potentials (2). The chapter then goes on to discuss the development of other carbon monoxide-tolerant catalysts, describing the vast array of mostly platinum-based catalysts that have been developed over the last thirty to forty years (3, 4). Crucially, each chapter ends in a brief but useful conclusion which identifies the avenues of research where we should anticipate future breakthroughs. The references are conveniently located at the end of each chapter, making them easy to access. Each chapter can be read as a stand-alone piece. The book claims to be aimed at the broader fuel cell community, including engineers, industry researchers and students. I would agree with this claim, but with the small caveat that I would not recommend it to a total novice, as the level of detail would rapidly become overwhelming for someone not familiar with the language and concepts associated with fuel cells and electro-

219

chemistry. The book is clearly up to date and represents a considerable amount of work by the authors, who all appear well qualified to write their respective chapters. The subject area of each chapter would merit an entire book in that field alone – but these exist already, and the value here is in linking the subject areas together so that the reader can benefit from having them all in one volume. The end result is rather long at over 1100 pages, but this is necessary and not a criticism, and represents good value considering the list price. For the reader who is interested in platinum group metals (pgms) this book contains plenty of information. Nearly every chapter discusses an area that is dominated by the electrochemistry of platinum and other pgms, but this is not surprising considering the central role of platinum in PEM fuel cell catalysis. From this point of view, the book also provides a good review of current technology and does not appear to make any major omissions of information that the pgm catalyst specialist would be expecting to see. On the whole I got a very positive impression of this book, and feel that it does succeed in its aims. It is well written and sufficiently consistent in style considering its multiple authors, and the editor has done a good job of pulling together so many topics and presenting them as a coherent whole. The book would be a good purchase for


anyone who has an interest in the science of PEM fuel cells. If you are new to the field, perhaps an undergraduate, there are probably better books to start with (see for example (5)). However, if you are a scientist or engineer, either at the top of your field or with just a year or more of experience in electrochemistry and/or electrocatalysis, this is a worthy addition to your book collection.

References 1

2 3 4 5

“Fuel Cells: Commercialisation”, Fuel Cell Today, U.K., 2008: http://www.fuelcelltoday.com/events/industry-review (Accessed on 14th August 2009) A. R. Kucernak and G. J. Offer, Phys. Chem. Chem. Phys., 2008, 10, (25), 3699 O. A. Petry, B. I. Podlovchenko, A. N. Frumkin and H. Lal, J. Electroanal. Chem., 1965, 10, (4), 253 J. S. Spendelow, P. K. Babu and A. Wieckowski, Curr. Opinion Solid State Mater. Sci., 2005, 9, (1–2), 37 R. O’Hayre, S.-W. Cha, W. Colella and F. B. Prinz, “Fuel Cell Fundamentals”, 2nd Edn., John Wiley & Sons, Inc, New York, U.S.A., 2009, 576 pp

The Reviewer Dr Gregory Offer is a Research Associate in Fuel Cell Science and Engineering, within the Faculty of Engineering at Imperial College, London, U.K., working with both the Department of Earth Science Engineering and the Department of Materials. He is also project manager of Imperial Racing Green, an undergraduate teaching project building hydrogen-powered fuel cell hybrid vehicles. He is currently on secondment to the Energy and Climate Change Committee at the Houses of Parliament in London, U.K.

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DOI: 10.1595/147106709X474307

The Taylor Conference 2009 CONVERGENCE BETWEEN RESEARCH AND INNOVATION IN CATALYSIS Reviewed by S. E. Golunski§ and A. P. E. York*‡ Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, U.K.; ‡

and Department of Chemical Engineering and Biotechnology, University of Cambridge, New Museums Site, Pembroke Street, Cambridge CB2 3RA, U.K.; *E-mail: [email protected]

The Taylor Conferences are organised by the Surface Reactivity and Catalysis (SURCAT) Group of the Royal Society of Chemistry in the U.K. (1). The series began in 1996, to provide a forum for discussion of the current issues in heterogeneous catalysis and, equally importantly, to promote interest in this field among recent graduates. The fourth in the series was held at Cardiff University in the U.K. from 22nd to 25th June 2009, attracting 120 delegates, mainly from U.K. academic centres specialising in catalysis. Abstracts of all lectures given at the conference are available on the conference website (2). The first half of the conference consisted of presentations by established researchers from the U.K., Japan and the U.S.A., with each presentation afforded ample time for debate and discussion. The format of the second half was similar, but with a key difference: the presenters were some of the postgraduate students and postdoctoral researchers who, it is hoped, will become the future generation of catalysis experts.

Concepts, Theories and Methodology Professor Sir Hugh Taylor, after whom the Taylor conferences are named, was a pioneer in the study of chemisorption and catalysis on metals and metal oxides (3). As Professor Frank Stone (Emeritus Professor of Chemistry, University of Bath, U.K.) reminded us in his opening address, H. S. Taylor (as he was known in his time) was responsible for introducing the concepts of activated adsorption and of the active site, both of which were highly controversial when he first proposed them around 1930 (4), but which have become fundamental to our understanding of many catalytic phenomena.

Professor Gabor Somorjai (University of California, Berkeley, U.S.A.) developed the theme that progress in catalysis is stimulated by revolutionary changes in thinking. He predicted that, whereas in previous eras new catalysts were identified through an Edisonian approach (based on trial and error) or discovered on the basis of empirical understanding, future catalyst design will be based on the principles of nanoscience. He highlighted his idea of ‘hot electrons’ that are ejected from a metal by the heat of reaction produced at active sites, but which could become a potential energy source if they were generated by the absorption of light. As described by Professor Richard Catlow (University College London, U.K.) and Stephen Jenkins (University of Cambridge, U.K.), quantum mechanical techniques for modelling manyelectron systems lend themselves to the study of catalytic materials and catalytic reaction pathways. Professor Catlow’s particular expertise lies in the study of defective metal oxides, and the way in which they interact with metal particles. In the case of palladium deposited on ceria, his models predict an increase in the concentration of Ce3+ species resulting from electron transfer from the metal to the metal oxide. Jenkins has been examining the likelihood of specific reaction steps taking place on the surface of supported metal catalysts. For both alkane synthesis and combustion, his calculations implicate a common formyl intermediate, which is not readily detected by spectroscopic techniques. However, Professor Charles Campbell (University of Washington, U.S.A.) cautioned against an overreliance on surface modelling. Based on classical microcalorimetric measurements, he has shown that density functional theory (DFT) underpredicts

§

Present address: Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, U.K.


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the heat of adsorption for a variety of molecules (for example, carbon monoxide, cyclohexene and aromatics) on a range of surfaces (such as carbon, precious metals or metal oxides).

Taking a View Professor Lynn Gladden (University of Cambridge) described how macroscopic and microscopic events can be tracked in an optically opaque system, such as a catalytic reactor. Using magnetic resonance imaging (MRI) – essentially the same technique as used diagnostically in medicine – she has been able to observe the liquid flow fields that develop in packed bed reactors. By combining the images with measurements from temperature sensors, detailed reaction profiles can be produced for steady-state and dynamic operating conditions. On a different scale, Professor Chris Kiely (Lehigh University, U.S.A.) has used dark-field imaging techniques to detect the smallest metallic, bimetallic and metal oxide particles (less than 1 nm in diameter) by electron microscopy. In what may become a seminal study, he has correlated the high CO-oxidation activity of a specific gold/iron oxide (Au/Fe2O3) catalyst with the presence of twolayer, 0.5 nm-diameter gold clusters. The importance of studying catalysis over a range of scales was emphasised by Professor Trevor Rayment (Diamond Light Source Ltd, U.K.). The new U.K. synchrotron light source is intended to provide understanding of ‘real catalysts, under real conditions, in real time’ (5). One of the ambitions is to increase the throughput for techniques such as X-ray absorption spectroscopy, by reducing the amount of nonproductive beam time. Although the Diamond facilities are not expected to provide the tools for catalyst discovery, it is hoped that they can accelerate the development process by identifying the critical relationships between catalyst structure and performance.

Controlling Selectivity Stressing a point made by Professor Somorjai that catalysis in the 21st century is all about selectivity, Chris Baddeley (University of St Andrews, U.K.) and Professor Andrew Gellman (Carnegie


Mellon University, U.S.A.) separately described the complex dependence of enantioselective reactions on surface composition and structure. As explained by Professor James Anderson (University of Aberdeen, U.K.), in the context of alkyne hydrogenation, poor selectivity is often the result of heterogeneity in the exposed sites, even on apparently clean and compositionally homogeneous surfaces. Through targeted use of additives, such as bismuth in the case of palladium-based hydrogenation catalysts, specific non-selective sites can be deliberately blocked. During the direct synthesis of hydrogen peroxide from hydrogen and oxygen, the combustion of hydrogen and the over-hydrogenation of hydrogen peroxide to water need to be suppressed. Professor Graham Hutchings (Cardiff University, U.K.) has shown that gold-palladium catalysts are among the most effective, but their performance can be sensitive to the support material used. In collaboration with Professor Kiely, he has found that the nature of the dispersed gold-palladium can vary, with core-shell particles (on titania and alumina) producing lower yields of H2O2 than palladium-rich alloy particles (on carbon). Both types of core-shell particle, those with a gold core and palladium shell and those with a palladium core and gold shell, were less active than the palladiumgold alloy. Professor Masatake Haruta (Tokyo Metropolitan University, Japan) has found that small gold clusters can selectively catalyse some particularly challenging reactions. The outstanding example is the selective insertion of oxygen into propylene to form propylene oxide, which is currently produced by indirect processes that produce large quantities of waste byproducts. By reactively grinding a nonchloride Au(III) precursor with titanium silicalite (TS-1), Professor Haruta has dispersed the gold as 1.6 nm particles, which can activate propylene to react with O–O–H species formed from oxygen and water at the metal-support interface.

Promoting and Maintaining Activity Vanadia supported on θ-alumina is one of the best catalysts for butane dehydrogenation, but the rate of reaction is very sensitive to the vanadia

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loading. Professor David Jackson (University of Glasgow, U.K.) reported that maximum activity coincides with the presence of a mainly polymeric form of vanadate species which covers most of the alumina surface. However, another key performance criterion is durability. During butane dehydrogenation, two forms of deactivation can be discerned: a short-term but reversible effect caused by deposition of carbon-rich species on the catalyst surface, and a longer-term effect associated with an irreversible phase change in the alumina. In the Francois Gault Lecture, Professor Robbie Burch (Queen’s University Belfast, U.K.) explained the challenges faced in developing and studying catalyst technology for removing nitrogen oxides (NOx) from diesel exhaust. Focusing on the use of silver for NOx reduction by direct reaction with some of the diesel fuel, he showed that its performance can be dramatically improved by the addition of hydrogen. As described in a presentation by Stan Golunski (Johnson Matthey Technology Centre, Sonning Common, U.K.) the hydrogen can be generated in situ through a process of exhaust gas reforming using a rhodium catalyst. Professor Burch explained how X-ray absorption fine structure (EXAFS) studies of silver have been used to refute one of the proposed roles of hydrogen, as a structural modifier, implying instead that it is directly involved in the NOx-reduction mechanism. Although several spectroscopic studies have been published (6) showing the presence of cyanide and isocyanate on the silver surface when hydrogen is present, kinetic measurements at Queen’s University Belfast have ruled these out as reactive intermediates, suggesting that more transitory species (such as hydroxamic acid or ammonia) are involved.

Future Prospects During his introduction to the postgraduate student and postdoctoral researcher presentations, Jack Frost (Johnson Matthey Fuel Cells, U.K.) compared and contrasted the academic process of research with the industrial activity of innovation. He used the example of vehicle emission control to show how the pressing need for improved local


air quality led to the development of technology for catalytic aftertreatment using pgm catalysts (7). This highly effective technology does not, however, address the global problem of greenhouse gas emissions, which is now the prime motivator for the introduction of fuel cells. Appropriately, there was an environmental theme running through many of the presentations in this section of the conference. For example, CO oxidation was covered by Sankaranarayanan Nagarajan (National Chemical Laboratory, Pune, India), who looked at oxygen mobility and the role of subsurface oxygen on palladium surfaces (8, 9), Figure 1. The subject was also covered by Kevin Morgan (Queen’s University Belfast), who presented a temporal analysis of products (TAP) study showing that the addition of gold to CuMnOx results in the availability of more surface oxygen and promotion of the Mars-van Krevelen oxygen transfer mechanism. A number of researchers from Cardiff University presented work on selective oxidation reactions. For example, Jonathan Counsell has been studying the effect of adding gold to a supported palladium acetoxylation catalyst. He has found that the gold suppresses carbon formation on the palladium surface by preventing dehydrogenation. Kara Howard described her work on modelling oxygen dissociation on gold clusters supported on iron oxide, and showed that the iron oxide stabilises dissociated oxygen atoms. Dyfan Edwards presented a surface science study of the synergy between the individual metal oxides in iron molybdate catalysts, which are used for oxidising methanol to formaldehyde. The selectivity of iron oxide changes with the level of coverage by molybdenum, from total combustion when no molybdenum is present, to partial oxidation (to CO) at low coverage, and finally selective oxidation (via a methoxy intermediate) at high coverage. Dr Jennifer Edwards has been examining the effect of preparation and pretreatment variables on the performance of gold-palladium catalysts for the direct synthesis of hydrogen peroxide. Acid pretreatment of the support material has resulted in catalysts with lower activity for the unwanted consecutive hydrogen peroxide-hydro-

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O2

1

2

CO Pd(111)

Pd(111) 3

δ+

4

δ

Pd (111)

Pd +(111) 5

δ

Pd +(111)

CO2

6

δ

Pd +(111)

Fig. 1 Schematic model for oxygen diffusion followed by CO + O2 reaction on Pd(111) > 550 K. Pd δ+= mildly oxidised Pd (Courtesy of Chinnakonda S. Gopinath, National Chemical Laboratory, Pune, India)

genation reaction, leading to very impressive hydrogen peroxide yields. The influence of the iron:cobalt ratio in an Fe2O3-Co3O4 catalyst, for converting ethanol to hydrogen, has been studied by Abel Abdelkader (Queen’s University Belfast). Fe2O3 catalyses ethanol steam reforming, and Co3O4 the water-gas shift reaction, so that a 1:1 ratio produces the optimum yield. In the field of syngas and hydrogen utilisation, Poobalasuntharam Iyngaran (University of Cambridge) presented a study of the effect of potassium promoters on ammonia synthesis over iron, which showed that stepwise hydrogenation of nitrogen surface adatoms is unaffected by the presence of potassium. Sharon Booyens (Cardiff University) is interested in DFT modelling of CO adsorption on iron surfaces, in the context of Fischer-Tropsch catalysis. The models predict that surface carbon causes a weakening of the Fe–CO interaction, and therefore CO dissociation becomes less favourable. Andrew McFarlane (University of Glasgow) presented his work on C5 olefin hydrogenation over 1% Pd/Al2O3. He suggested that reaction of the cis-pentene isomer must proceed via formation of the trans isomer before hydrogenation can occur.


Finally, there were several very topical presentations concerned with clean synthesis of chemicals and fuels. Lee Dingwall (University of York, U.K.) has been synthesising and working with a bifunctional heterogeneous catalyst that combines an active ruthenium organometallic centre with a polyoxometallate cage, Figure 2. This provides acid sites and also confers great stability, and the catalyst structure displays high activity for C–C bond formation. Ceri Hammond (Cardiff University) described the reaction of glycerol with urea over zinc, gallium or gold supported on zeolite. Glycerol carbonate can be obtained with high selectivity in a one-step solvent-free process over these catalysts, though there is some question over their stability. The prize for the best student presentation was awarded to Janine Montero (University of York) who is researching the use of heterogeneous catalysts for biodiesel synthesis by transesterification, as a replacement for the liquid catalysts currently in use. She has shown, by Auger electron spectroscopy, that high-temperature calcination of nanoparticulate magnesium oxide results in increased surface polarisability, and therefore higher Lewis basicity. Her results show that there is a

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+

Ru

C

O

W

P HNEt33

Fig. 2 Proposed structure of the polyoxometallate-tethered ruthenium complex [HNEt3] +[(Ru{η 5-C5H5}{PPh3}2)2(PW12O40)] – (Courtesy of Karen Wilson, University of York, U.K.)

P

linear relationship between polarisability and transesterification activity over these MgO catalysts.

Summary In summing up the conference, Professor Wyn Roberts (Emeritus Professor, Cardiff University) recalled that when he began his Ph.D. he had to make the choice between studying clean surfaces (i.e. single crystals) or real catalysts. As many of the presentations highlighted, this distinction is no longer useful, with the so-called ‘material’ and ‘pressure’ gaps in catalysis, between results obtained from surface science studies, usually using idealised surfaces under high

vacuum, and those from real catalyst materials at ambient or high pressures (10), having gradually narrowed. Frost had earlier commented on a similar convergence, between research and innovation. As he pointed out, though, these activities need to remain distinct, because they fulfil quite different functions. However, with their shared values of insight, integrity, creativity and professionalism, they will be increasingly directed in parallel at our most urgent challenges in catalysis and in society: sustainability and environmental protection. The fifth Taylor Conference is scheduled to take place in Aberdeen in 2013 (11).

References 1 Royal Society of Chemistry, Surface Reactivity and Catalysis (SURCAT) Group: http://www.rsc.org/ Membership/Networking/InterestGroups/Surface Reactivity/index.asp (Accessed on 5th August 2009) 2 The Taylor Conference 2009: http://www.taylor. cf.ac.uk/ (Accessed on 5th August 2009) 3 E. R. Rideal and H. S. Taylor, “Catalysis in Theory and Practice”, Macmillan and Co Ltd, London, U.K., 1919 4 P. B. Weisz, Microporous Mesoporous Mater., 2000, 35–36, 1 5 Diamond Light Source, Publications, Case Studies: http://www.diamond.ac.uk/Home/Publications/case _studies.html (Accessed on 27th August 2009)

6 F. Thibault-Starzyk, E. Seguin, S. Thomas, M. Daturi, H. Arnolds and D. A. King, Science, 2009, 324, (5930), 1048 7 M. V. Twigg, Appl. Catal. B: Environ., 2007, 70, (1–4), 2 8 C. S. Gopinath, K. Thirunavukkarasu and S. Nagarajan, Chem. Asian J., 2009, 4, (1), 74 9 S. Nagarajan, K. Thirunavukkarasu and C. S. Gopinath, J. Phys. Chem. C, 2009, 113, (17), 7385 10 J. M. Thomas, J. Chem. Phys., 2008, 128, (18), 182502 11 Royal Society of Chemistry, Publishing, Journals, PCCP, News, 2009: http://www.rsc.org/Publishing/ Journals/CP/News/2009/TaylorPCCPPrizes.asp (Accessed on 5th August 2009)

The Reviewers Stan Golunski has recently been appointed Deputy Director of the Cardiff Catalysis Institute; he was formerly Technology Manager of Gas Phase Catalysis at the Johnson Matthey Technology Centre at Sonning Common in the U.K. His research interests include catalytic aftertreatment and reforming.


Andy York is a Johnson Matthey Research Fellow in the Department of Chemical Engineering and Biotechnology at the University of Cambridge, U.K. His research interests lie at the interface between catalyst chemistry and reaction engineering.

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DOI: 10.1595/147106709X475324

ABSTRACTS CATALYSIS – APPLIED AND PHYSICAL ASPECTS

EMISSIONS CONTROL

Catalytically Active, Magnetically Separable, and Water-Soluble FePt Nanoparticles Modified with Cyclodextrin for Aqueous Hydrogenation Reactions K. MORI, N. YOSHIOKA, Y. KONDO, T. TAKEUCHI and H. YAMASHITA, Green Chem., 2009, 11, (9), 1337–1342

Thermal decomposition of Fe(CO)5, followed by reduction of Pt(acac)2 in the presence of oleic acid and oleylamine, gave FePt nanoparticles (1) with Ferich cores and Pt-rich shells. (1) were subsequently treated with γ-cyclodextrin (γ-CD). FePt-γ-CD (2) exhibited superparamagnetic behaviour at 300 K. (2) was used for aqueous hydrogenation reactions, with easy recovery of (2) by applying an external magnet. Catalytic Inactivation of Bacteria Using Pd-Modified Titania L. R. QUISENBERRY, L. H. LOETSCHER and J. E. BOYD,

Catal.

Commun., 2009, 10, (10), 1417–1422

For the photocatalytic sterilisation of Escherichia coli in H2O, Pd/TiO2 was faster than Pt/TiO2. Pd/TiO2 was also active in the absence of light. Pd/TiO2 temporarily lost bactericidal activity after use, but was reactivated in air. It is proposed that the Pd metal on the surface of Pd/TiO2 is reduced in solution during the reaction, and must be reoxidised to regain activity. The reduction may initiate the bactericidal activity.

CATALYSIS – REACTIONS Iridium Catalysed Alkylation of 4-Hydroxy Coumarin, 4-Hydroxy-2-quinolones and Quinolin4(1H)-one with Alcohols under Solvent Free Thermal Conditions R. GRIGG, S. WHITNEY, V. SRIDHARAN, A. KEEP DERRICK, Tetrahedron, 2009, 65, (36), 7468–7473

and

A.

Re-evaluation and Modeling of a Commercial Diesel Oxidation Catalyst Y.-D. KIM and W.-S. KIM, Ind. Eng. Chem. Res., 2009, 48, (14), 6579–6590

A modelling approach to predict the performance of a DOC used published experimental data and a new set of conversion experiments. Steady-state experiments with DOCs (Pt supported on an Al2O3 washcoat) mounted on a light-duty turbocharged diesel engine were carried out. The reaction rates for CO, HC, and NO oxidations in diesel exhaust over fresh Pt/Al2O3 were determined in conjunction with a transient 1D heterogeneous plug-flow reactor model. NOx Abatement for Lean-Burn Engines under Lean–Rich Atmosphere over Mixed NSR-SCR Catalysts: Influences of the Addition of a SCR Catalyst and of the Operational Conditions E. C. CORBOS, M. HANEDA, X. COURTOIS, P. MARECOT, D. DUPREZ and H. HAMADA, Appl. Catal. A: Gen., 2009, 365,

(2), 187–193

The NOx removal efficiency of a Pt-Rh/Ba/Al2O3 NSR model catalyst under a lean/rich atmosphere was improved by the addition of a SCR catalyst (Co/Al2O3 or Cu/ZSM-5). Both SCR catalysts were able to reduce NOx using the NH3 formed during the rich cycles on Pt-Rh/Ba/Al2O3. With Cu/ZSM-5, this was independent of the reductant used (CO or H2) and of the reduction time (10, 5 or 2.5 s).

FUEL CELLS Origin and Quantitative Analysis of the Constant Phase Element of a Platinum SOFC Cathode Using the State-Space Model S. RICCIARDI, J. C. RUIZ-MORALES and P. NUÑEZ, Solid State Ionics, 2009, 180, (17–19), 1083–1090

Ir-catalysed alkylation of the title compounds with substituted benzyl and aliphatic alcohols under solventfree heating gave the monoalkylated products in high to excellent yield. 3,3'-Bis (heterocyclyl) methane products can arise via a Michael addition pathway. The alkylation of 4-hydroxy-1-methyl-2(1H)-quinoline with BzOH, KOH and the Ir chloro-bridged [Cp*IrCl2]2 dimer was carried out at 110ºC for 48 h in a sealed tube.

A SOFC cathode was investigated using SEM, electrochemical impedance spectroscopy and simulations using the state-space model. The kinetic parameters were determined. The triple phase boundary length was measured and its width deduced. A quantitative analysis of the constant phase element using surface roughness and energy activation distribution is presented.

An Alternative Synthesis of Tamiflu®: A Synthetic Challenge and the Identification of a RutheniumCatalyzed Dihydroxylation Route

Fabrication of High Precision PEMFC Membrane Electrode Assemblies by Sieve Printing Method

K. YAMATSUGU, M. KANAI

and M. SHIBASAKI, Tetrahedron,

2009, 65, (31), 6017–6024

A Ru-catalyzed dihydroxylation synthetic route was identified for Tamiflu®, which removes the need for a Mitsunobu inversion step. Only 0.5 mol% of RuCl3 was required. The use of explosive trifluoroperacetic acid, generated in situ, is also avoided.


A. B. ANDRADE, M. L. MORA BEJARANO, E. F. CUNHA, E. ROBALINHO and M. LINARDI, J. Fuel Cell Sci. Technol., 2009,

6, (2), 021305 (3 pages)

A sieve printing technique was used for the preparation of PEMFC gas diffusion electrodes. MEA evaluation was carried out in a 25 cm2 single PEMFC with loadings of 0.4 mg Pt cm–2 and 0.6 mg Pt cm–2 on the anode and cathode, respectively. The MEAs had higher power density than spray printed ones.

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Synthesis of Intermetallic PtZn Nanoparticles by Reaction of Pt Nanoparticles with Zn Vapor and Their Application as Fuel Cell Catalysts A. MIURA, H. WANG, B. M. LEONARD, H. D. ABRUÑA and F. J. DiSALVO, Chem. Mater., 2009, 21, (13), 2661–2667

Intermetallic PtZn nanoparticles (1) were synthesised by reaction of C-supported Pt nanoparticles with Zn vapour at 500ºC for 8 h under flowing N2 at atmospheric pressure. The catalytic activities of supported (1) toward formic acid and MeOH electrooxidation were studied by differential electrochemical mass spectrometry. (1) exhibited higher currents for both oxidations than supported Pt nanoparticles with similar particle sizes.

METALLURGY AND MATERIALS

APPARATUS AND TECHNIQUE Nanocomposite Based on Depositing Platinum Nanostructure onto Carbon Nanotubes through a One-Pot, Facile Synthesis Method for Amperometric Sensing D. WEN, X. ZOU, Y. LIU, L. SHANG and S. DONG, Talanta, 2009,

79, (5), 1233–1237

Pt nanoparticles deposited onto carbon MWNTs, through direct chemical reduction, can electrocatalyse the oxidation of H2O2 and substantially raise the response current. Glucose oxidase (GOD) was immobilised on the nanocomposite-based electrode with a thin layer of Nafion. This glucose biosensor with a GOD loading concentration of 10 mg ml–1 had a detection limit of 3 μM and a response time of 3 s.

Facile Approach to the Synthesis of 3D Platinum Nanoflowers and Their Electrochemical Characteristics

BIOMEDICAL AND DENTAL

J. N. TIWARI, F.-M. PAN and K.-L. LIN, New J. Chem., 2009, 33,

R. C. TODD and S. J. LIPPARD, Metallomics, 2009, 1, (4), 280–291

(7), 1482–1485

Structural investigations of Pt–DNA adducts and the effects of these lesions on global DNA geometry are reviewed. Research detailing inhibition of cellular transcription by Pt–DNA adducts is presented. A mechanistic analysis of how DNA structural distortions induced by Pt damage may inhibit RNA synthesis in vivo was carried out. (155 Refs.)

3D Pt nanoflowers (1) were synthesised by a potentiostatic pulse plating method on a Si substrate. Electrochemical analysis established that (1) had a much larger active surface area than a Pt thin film by a factor of > 110, and were likely preferentially oriented in the (100) and (110) surface planes. (1) exhibited excellent electrocatalytic activity toward MeOH oxidation and a high CO tolerance as compared with a Pt thin film. Fe Oxidation versus Pt Segregation in FePt Nanoparticles and Thin Films L. HAN, U. WIEDWALD, B. KUERBANJIANG and P. ZIEMANN,

Nanotechnology, 2009, 20, (28), 285706 (7 pages)

The oxidation behaviour of differently sized FePt nanoparticles (1) was investigated by XPS and compared to a FePt reference film. For the as-prepared samples Fe3+ is formed, becoming detectable for exposures to pure O2 above 106 langmuir, while Pt0 remains. After annealing at 650ºC, large (1) as well as the reference film exhibited a 100–1000 times enhanced resistance against oxidation, whereas small (1) (diameter 5 nm) showed no such enhancement. Atomic-Level Pd–Au Alloying and Controllable Hydrogen-Absorption Properties in SizeControlled Nanoparticles Synthesized by Hydrogen Reduction H. KOBAYASHI, M. YAMAUCHI, R. IKEDA and H. KITAGAWA,

Chem. Commun., 2009, (32), 4806–4808

PVP-protected Pd nanoparticles were prepared from the alcoholic reduction of PdCl2 in the presence of PVP. An aqueous solution of HAuCl4 was added and the mixture was stirred under H2 gas to form Pd-Au alloy nanoparticles. 20 at.% of Au in Pd suppressed H2 absorption completely. The amount of H2 absorption is controllable by low-concentration alloying with Au.


Inhibition of Transcription by Platinum Antitumor Compounds

CHEMISTRY Synthesis and Structural Characterization of Binuclear Palladium(II) Complexes of Salicylaldimine Dithiosemicarbazones T. STRINGER, P. CHELLAN, B. THERRIEN, N. SHUNMOOGAMGOUNDEN, D. T. HENDRICKS and G. S. SMITH, Polyhedron, 2009,

28, (14), 2839–2846

The title complexes were synthesised by the reaction of ethylene- and phenylene-bridged dithiosemicarbazones with Pd(PPh3)2Cl2. Two representative Pd complexes were characterised by XRD. The two Pd centres are coordinated in a slightly distorted squareplanar geometry, which gives rise in each case to fiveand six-membered chelate rings. The ligands coordinate to Pd in a tridentate manner, through the phenolic O, imine N and thiolate S atoms. Synthesis, Properties and Crystal Structures of Volatile β-Ketoiminate Pd Complexes, Precursors for Palladium Chemical Vapor Deposition G. I. ZHARKOVA, P. A. STABNIKOV, I. A. BAIDINA, A. I. SMOLENTSEV and S. V. TKACHEV, Polyhedron, 2009, 28, (12),

2307–2312

β-Aminovinylketone ligands CH3C(NH2)CHC(O)CH3 and CH3C(NHCH3)CHC(O)CH3 were synthesised. Their reaction with PdCl2 in an amine medium afforded the complexes Pd[CH3C(NH)CHC(O)CH3]2 (1) and Pd[CH3C(NCH3)CHC(O)CH3]2 (2). In (1) and (2), the Pd atom exhibits square coordination, Pd O2N2.

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DOI: 10.1595/147106709X474622

NEW PATENTS CATALYSIS – APPLIED AND PHYSICAL ASPECTS Preparation of Platinum on Activated Carbon UNIV. KEBANGSAAN MALAYSIA

World Appl. 2009/057,992

A catalyst with ≥ 40 wt.% loading of Pt and mean particle size of 28 μm is prepared by adding a solution of H2PtCl6 or (NH4)2PtCl4 in aqua regia to activated C powder with particles 20–30 μm in size, pretreated with HNO3. A base such as NH4OH is added to raise the pH to 9.7–9.9. The solution is boiled and calcined by heating at 120–130°C then at 340–360°C. Palladium-Gallium Hydrogenation Catalysts MAX-PLANCK-GESELLSCHAFT

World Appl. 2009/062,848

Optionally supported, ordered intermetallic PdGa compounds are prepared by reacting a Pd compound, preferably Pd(acac)2, with a Ga compound, preferably a Ga halide, in the presence of a reductant such as LiBEt3H and optionally a solvent such as THF or diglyme. Alternatively, Pd is reacted with a vaporised Ga compound, such as GaI3. Particular application for the selective conversion of ethyne to ethene in the presence of an excess of ethene is claimed.

CATALYSIS – INDUSTRIAL PROCESS Two-Stage Distillate to Gasoline Conversion CONOCOPHILLIPS CO

U.S. Appl. 2009/0,134,061

Distillate with research octane number (RON) 25–50, is converted to gasoline with RON > 65, by contact with: (a) 0.5–5 (preferably 0.5–3) wt.% Pt and/or Pd on an acidic support, preferably zeolite, in the presence of H2, at 220–260ºC, then (b) 0.5–5 (preferably 0.5–3) wt.% Ir and optionally Ni on a support such as SiO2 or Al2O3, at 280–330ºC.

CATALYSIS – REACTIONS Iridium Catalyst for Nitrile Hydration UNIV. OKAYAMA

Japanese Appl. 2009-023,925

Amides are produced from nitriles under mild conditions using a catalyst system formed from an Ir complex, XIrL2, YIrZ2 or (YIrZ)2, with an electronwithdrawing organic phosphine; where X = a Group 15 element or a bidentate ligand containing O–; L = a phosphine or a neutral ligand exchangeable with a phosphine; Y = a multidentate ligand containing C– or N–; and Z = a negatively charged monodentate ligand.

Lean NOx Trap and Reduction Catalyst TOYOTA MOTOR CORP


A NOx occlusion and reduction catalyst has Rh supported on two different oxide materials, such as a mixture of Al2O3 and ZrO2-TiO2, in the ratio 1:9–5:1. Rh solubility is ≥ 70% in the first and < 70% in the second oxide, when heat treated at > 750ºC and at a loading of 0.01–5 wt.% Rh. During lean operation, Rh goes into solid solution in the first oxide, preventing grain growth and sintering. In the rich phase, Rh precipitates out of solution to catalyse NOx reduction.

FUEL CELLS Membrane Electrode Assembly Evaluation GM GLOBAL TECHNOL. OPER. INC

U.S. Appl. 2009/0,124,020

A PEMFC MEA is soaked in an unsaturated organic compound, such as 0.5–2.0 wt.% polyoxyethylene (10) oleyl ether (Brij® 97) in H2O, and then stained with a strongly oxidising agent, specifically OsO4. The MEA is embedded in an epoxy and thin sections for viewing using TEM are prepared. Ionomer and catalyst particles will appear as dark regions and pores as light regions, allowing porosity and size and distribution of particles to be determined. Membrane Electrode Assembly with Anion Exchange TOSHIBA CORP


A membrane/electrode composite includes an anion exchange substance, deposited on the anode catalyst layer or the electrolyte membrane, which captures mobile Ru-containing anions to prevent catalyst degradation. The substance is deposited as a film, or as particles with diameter 0.01–50 μm, in mass ratio of 5:95–90:10 relative to the anode catalyst, or at a loading of 1–50 mg cm–2 of electrode surface area.

METALLURGY AND MATERIALS Platinum Jewellery Alloy HEIMERLE & MEULE GmbH

World Appl. 2009/059,736

A Pt alloy consists of (in wt.%): 94.0–96.5 Pt (preferably 95.1–95.5); 2.5–4.5 W (preferably 3.7–3.8); 0.5–3.0 Cu (preferably 0.9–1.1); and 0.02–2.0 (preferably 0.04–0.07) of at least one of Ru, Rh and Ir, and is free of Au. It offers high hardness and resistance to abrasion combined with good workability and cold formability. Semi-finished jewellery components are also claimed.

EMISSIONS CONTROL

Corrosion-Resistant Platinum-Rhodium Alloy

Efficient Treatment of Particulate Matter

ISHIFUKU MET. IND. CO, LTD

ETM INT. LTD

World Appl. 2009/090,447

A catalyst cartridge contains mineral fibres with density 300–1000 g m–3, composed of ≥ 80 wt.% SiO2 with Pt and/or Ir, arranged in radial undulations with rectilinear sections of length l perpendicular to the direction of gas flow. The fibres are 0.3–1 mm thick, with distance d between undulations such that l/d = 5–12.



A PtRh alloy for high-temperature and electrical applications is described as possessing good resistance to corrosion caused by P, Pb, As, B, Bi, Si, Zn, but in particular P. It consists of 10–40 wt.% Rh with at least one of (in wt.%): 0.1–5.0 V, Cr, Nb, Mo, Ta, Re and/or W; 0.1–3.0 Mn and/or Co; 0.3–5.0 Ru, Pd, Ir, Au and/or Ag; and/or 0.01–1.0 Al, and the balance Pt.

228

APPARATUS AND TECHNIQUE

ELECTRICAL AND ELECTRONICS

Spark Plug with Iridium Alloy Tip

Ruthenium-Doped Semi-Insulator for Laser Diode

HONEYWELL INT. INC

U.S. Appl. 2009/0,127,996

T. KITATANI et

al.

U.S. Appl. 2009/0,129,421

A spark plug with electrode tip formed from an Ir alloy is presented. The alloy composition is (in wt.%): 60–70 Ir, 30–35 Rh, 0–10 Ni and has minor additions (in ppm) either: (a) 3500-4500 Ta and 100-200 Zr, or (b) 50–100 Ce. These allow for better bonding of the tip with the Ni alloy of the electrode body through interdiffusion. The Ir alloy offers high wear resistance.

A semi-insulating layer is formed by doping a semiconductor material such as InP with Ru, Os, Rh or Ti, but in particular Ru. It is included between the p-type and n-type semiconductor layers to limit current leakage in the window region of a semiconductor laser, particularly a short cavity edge-emitting laser.

Unsupported Palladium Membranes

HEWLETT-PACKARD DEV. CO, LP

J. D. WAY et

al.

U.S. Appl. 2009/0,176,012

Defect-free, 7.2 μm-thin Pd membranes are formed by electroless plating on a support such as mirrorfinished stainless steel, in an EDTA-free plating bath at 50ºC with addition of 1 part per 100 of hydrazine solution (3 M). The support may be seeded with metallic Pd crystallites from Pd acetate. A second metal such as Cu, Ag or Au may also be deposited by electroless plating and the membrane homogenised by annealing. The membrane is freed from the support by scoring the edges. H2 permeabilities may be equivalent to thicker membranes and H2/N2 selectivity can reach 40,000. Porous Platinum Nanoparticles UNIV. MIYAZAKI

Palladium Complex for Printed Circuits


Monocrystalline Pt nanoparticles with nanopores, for use in catalysts, electrodes or sensors, and their method of production are described. The particles are sheets 2–25 nm thick with outer diameter 30–600 nm. The pores may have diameter 1–3.5 nm or may be elliptical or rectangular with dimensions 1 × 3.5 to 3.5 × 10 nm, and are arrayed at regular intervals of 4–5 nm or at intervals varying from 1–5 nm. The particles may be composed of Pt, Pt and a base metal, or an alloy of Pt with Pd, Rh, Ir, Ru, Au, and/or Ag.

U.S. Appl. 2009/0,201,333

A Pd aliphatic amine complex (1) in a liquid carrier is inkjet printed on a substrate, a second composition containing a reducing agent such as formic acid is applied and the substrate is heated at 50–80ºC to reduce (1) to Pd metal. Alternatively, (1) can be applied as a seed layer for a subsequent conductive metal such as Pt, Pd, Rh, Au, Cu, Ni or various alloys.

PHOTOCONVERSION Luminescent Platinum Complexes ARIZONA STATE UNIV.

World Appl. 2009/086,209

Pt(II) di(2-pyrazolyl)benzene chloride and its analogs, which are obtained by forming an aromatic six-membered ring, 1,3-di-substituted by aromatic five-membered heterocyles such as pyrazolyl, imidazolyl, thiazolyl or substituted groups thereof, and reacting with an acidic Pt-containing solution. The benzene may be fluorinated, difluorinated, methylated, or replaced by pyridine. Cl may be replaced by a phenoxy group. The Pt(II) complexes, which in some embodiments are phosphorescent, are claimed for use as blue or white light emitters in OLEDs.

REFINING AND RECOVERY

BIOMEDICAL AND DENTAL

Ruthenium Recovery from Solid Components

Anticancer Rh(III) and Ir(III) Complexes Novel octahedral metal(III) polypyridyl complexes M(hal)3(sol)(pp) for the prevention and treatment of cancer and its metastases are claimed, described as exhibiting superior cytotoxic activity in cell cultures. M is Rh or Ir, preferably Rh. Sol is a solvent, preferably DMSO or H2O; hal is a halogen, preferably Cl or Br, or a psuedohalogenide, preferably SCN; and pp is a polypyridyl ligand, preferably dpq, dppz or dppn.

Ru is selectively recovered from hard disks, electrodes etc. by contact with an aqueous solution to form a Ru compound which is subsequently eluted and separated by filtration. The aqueous solution can be: (a) formic acid, (b) oxalic acid, (c) an acid and sugars, or (d) an acid and formic acid, alcohols, aldehydes or an acetal/hemiacetal compound (or precursors thereof). For (c) and (d), the acid is preferably 1–90 wt.% of the solution. The solid may also be oxidised by one of O2, air, O3 or H2O2 for second-pass removal of Ru.

Ultra-Low Magnetic Susceptibility Palladium Alloys

Dry Method for Recovering PGMs

European Appl. 2,072,521

FREIE UNIV. BERLIN

DERINGER-NEY INC

U.S. Appl. 2009/0,191,087

Pd alloys for biomedical components compatible with the use of magnetic resonance imaging are claimed. The composition is (at.%): ≥ 75 Pd; 3–20 Sn, Al or Ta; plus one or more of whichever of Sn, Al or Ta are not used in the binary composition, and/or Nb, W, Mo, Zr or Ti, up to a total of 22 at.%. The alloys are formulated such that the volume magnetic susceptibility (cgs) is between 3 × 10–6 and –3 × 10–6.


TOSHIBA KK

World Appl. 2009/093,730

DOWA METALS AND MINING CO LTD


A sealed electric furnace is charged with spent pgmcontaining solid components and granular Cu oxide having a particle diameter of 0.1–10 mm, a powdered reducing agent and a flux, and melting is done at pressures < 1 atm. The pgms preferentially dissolve in the molten Cu, and the oxides are removed in the slag, which has final Cu content of < 3%.

229

NAME INDEX TO VOLUME 53 Page

Abdelkader, A. 224 Abe, T. 52, 106 Abruna, H. D. 227 Abu Sheikha, G. 176 Actis Grande, M. 200 Adams, R. D. 50 Adler, J. 175 Adschiri, T. 154 Advani, S. G. 175 Ager, D. J. 203, 204 Agert, C. 154 Aggarwal, V. K. 88 Akçin, N. 105 Albrecht, B. 40 Al-Noaimi, M. 176 Alonso, E. 43 Alvarez, P. J. J. 105 Amore, S. 51 An, G. 105 Ananikov, V. P. 105 Anderson, C. 41 Anderson, J. A. 112, 222 Andrade, A. B. 226 Andrews, P. 36 Antipin, M. Yu. 105 Antolini, E. 51 Antonova, O. V. 138 Anzai, Y. 51 Arbizo, C. 43 Arico, A. S. 151 Aronson, J. 36 Arunachalampillai, A. 52 Auberson, A. 25 Baca, E. 40 Bäckvall, J.-E. 203 Baddeley, C. 222 Bagshawe, K. 36 Baidina, I. A. 227 Balle, P. 175 Balzani, V. 45, 46 Barigelletti, F. 45 Barnard, C. 36, 67 Basi, M. 41 Battaini, P. 21, 198, 199 Beebe, Jr., T. P. 175 Beletskaya, I. P. 105 Bertel, E. 176 Bhat, V. V. 176 Bhushan, B. 52 Blankenstein, U. 41

Page

Blaser, H.-U. Blatter, A. Blom, D. A. Bloxham, L. Blumberg, P. Boggs, M. E. Bonder, M. J. Book, D. Booyens, S. Borisov, S. M. Boro, B. J. Borzone, G. Bousa, M. Bouzek, K. Boyd, J. E. Braibant, C. Breit, B. Brelle, J. Brock, P. Bull, S. Bullock, J. Bullock, J. P. Bultel, Y. Burch, R. Byriel, I. P. Calman, K. Calvert, H. Cameron, D. S. Campagna, S. Campbell, C. Capela, S. Captain, B. Carlson, B. Casey, P. Catlow, R. Chakraborty, D. Chang, L. Chaplin, D. Chayama, K. Chellan, P. Chen, C.-Y. Chen, J.-G. Chen, W. Cho, B.-G. Choi, J.-S. Chong, L. C. Chown, L. H. Christgen, B. Christie, D. A. Claassen, P. Clarke, N.


207 189 50 179 43 175 51 84 224 106 52 51 41 148 226 40 207 189 36 89 40 106 154 223 148 36 36 147 45 221 170 50 106 42 221 149 105 206 102 227 52 52 86 106 169 50 2, 155 152 35 82 41

Page

Colacot, T. J. 183 Compagnoni, G. 188 Contescu, C. I. 176 Cooke, S. 43 Corbos, E. C. 226 Cordin, M. 176 Cornish, L. A. 2, 69, 155 Correia, I. 176 Cortes Felix, N. 164 Corti, C. W. 21, 24, 198, 200 Coughlin, M. 42 Counsell, J. 223 Courtois, X. 226 Creeth, A. M. 151 Cunha, E. F. 226 Curry, R. J. 50 Danks, M. 198 Davies, P. 86, 87 Davis, S. 25 Dawson, G. 200 De Castro, E. 40 de Vries, A. 204 Deisl, C. 176 Delsante, S. 51 Demkowicz, P. 105 Derrick, A. 226 Deutschmann, O. 175 Dinderman, M. A. 106 Ding, K. 105 Dingwall, L. 224 DiSalvo, F. J. 227 Diskin-Posner, Y. 52 Divakar, D. 50 Do, J. S. 175 Doná, E. 176 Dong, S. 227 Douglas, A. 2, 69 Douglas, P. 51 Dressick, W. J. 106 Dudek, D. 51 Duesler, E. N. 52 Dufour, J. 176 Duisberg, M. 175 Dujardin, C. 168 Dupont, J. 67 Duprez, D. 226 Dyson, P. J. 35 Eccarius, S. Edwards, D.

154 223

Page

Edwards, H. Edwards, J. Egebo, T. Eichinger, B. E. El-Eswed, B. Enders, M. Epling, W.

89 223 147 106 176 50 168

Fang, Y.-L. 105 Feller, M. 52 Ferguson, S. 40 Fermvik, A. 101 Ficicilar, B. 153 Fischer-Bühner, J. 22, 201 Fisher, J. M. 153 Foo, R. 164 Fordred, P. 89 Forzatti, P. 50 Fossey, J. S. 86, 89 Franchini, C. 176 Frost, C. 86, 89 Frost, J. 85, 223 Fryé, T. 22, 23 Furimsky, E. 135 Furukawa, Y. 88 Gallego, N. C. 176 Gamino-Arroyo, Z. 100 Gammon, R. 82 Gan, J. 105 Gayduk, K. A. 105 Gellman, A. 222 George, E. 145 Georges, S. 154 Gilby, S. 152 Giunti, T. 82 Gladden, L. 222 Glaner, L. 2, 155 Gökaliler, F. 150 Goldberg, K. I. 52 Golunski, S. E. 221, 223 Gonzalez, E. R. 51 Gopinath, C. S. 224 Grahame - Smith, D. 36 Gralla, R. 36 Grant, R. A. 100 Gray, P. 150 Green, R. 79 Gregory, D. 83 Greinke, R. 202

230

Page

Griffith, W. P. Grigg, R. Grimwade, M. Grundmann, A. Gülzow, E. Guo, M.

209 226 202 154 151 50

Haas, W. 106 Hadjipanayis, G. C. 51 Hagelueken, C. 41 Hallikainen, A. 105 Hamada, H. 226 Hammond, C. 224 Han, B. 105 Han, L. 227 Hancock, F. 188, 204 Haneda, M. 226 Harrap, K. 36 Harris, R. 84 Harrison, J. 79 Haruta, M. 222 Heck, K. N. 105 Helliwell, J. 81 Hendricks, D. T. 227 Hepworth, R. 79 Hernández, J. R. 166 Hill, P. J. 69 Hiro, T. 165 Hiromi, C. 52 Ho, K.-C. 52 Hoeschele, J. 36 Hoge, G. 207 Holdcroft, S. 52 Howard, K. 223 Huang, C.-J. 105 Huang, Y. H. 51 Huot, J. 176 Hutchings, G. 222 Huuhtanen, M. 105 Ianniello, R. Ikariya, T. Ikeda, N. Ikeda, R. Inoue, M. Irandoust, M. Iron, M. A. Itakura, T. Iwata, Y. Iyngaran, P. Izatt, S. Jackson, D. Jacobsen, R. James, K.

42 203, 208 106 227 52 106 52 106 165 224 41, 43 223 41, 43 43

Page

Jenkins, S. Jin, Y. Jiskra, J. Johnson, M. T. Johnson, T. V. Jollie, D. Jones, H. Jones, M. Joshaghani, M. Judson, I. Jun, B.-H.

221 176 42 52 37 182 202 202 106 36 50

Kallinen, K. 105 Kallio, T. 58 Kaminsky, W. 106 Kanai, M. 226 Kanehara, M. 106 Kang, H. 50 Keep, A. 226 Keiski, R. L. 105 Kemp, R. A. 52 Kendall, K. 78, 80 Khrustalev, V. N. 105 Khurshid, H. 51 Kiely, C. 222 Kim, I.-K. 106 Kim, J.-H. 50 Kim, P. S. 165 Kim, W.-S. 226 Kim, Y.-D. 226 Kitagawa, H. 227 Kitami, T. 52 Kittelson, D. B. 31 Kjellin, P. 51 Klein, J.-M. 154 Klerke, A. 149 Klimant, I. 106 Klotz, U. 201 Kobayashi, H. 227 Koch, F. 79 Kohl, G. 50 Kolb, G. 172 Kolli, T. 105 Kondo, Y. 226 Kontturi, K. 58 Kossov, A. 98 Kramer, E. P. 101 Krog, O. 147 Kuai, P. 50 Kuerbanjiang, B. 227 Kumar, P. 128 Kureti, S. 175 Kuriyama, W. 205 Kurz, T. 154 Kwak, K. J. 52


Page

Lapidus, G. T. 100 Latini, A. 176 Le Ret, C. 205 Lee, M. H. 175 Lee, S.-H. 50 Lee, W.-Y. 153 Lee, Y.-S. 50 Lei, Y. J. 43 Leitus, G. 52 Lennon, I. 205 Leonard, B. M. 227 Lewis, J. 85 Li, G. 176 Li, J. 175 Li, J.-Y. 52 Liang, X. 50 Liang, Z. X. 105 Libuda, J. 170 Lietti, L. 50 Lin, K.-L. 227 Lin, Z. 176 Linardi, M. 226 Linderoth, S. 154 Lindner, E. 176 Lippard, S. J. 227 Liu, C.-J. 50 Liu, Y. 227 Liu, Z. 105 Loetscher, L. H. 226 Lohwongwatana, B. 25 Lopes, T. 51 Loschialpo, P. 106 Lu, W. 176 Luo, Y. 176 Lupton, D. 42, 145 Ma, D. 176 Maerz, J. 24, 200 Maggian, D. 202 Mahittikul, A. 105 Manikandan, D. 50 Mansur, M. B. 100 Manziek, L. 40 Marecot, P. 226 Martin, A. 79 Matsubara, H. 169 Matsuzono, Y. 175 Mauser, A. 78 McCarney, J. 172 McCloskey, J. 25 McFarlane, A. 224 Mekasuwandumrong, O. 175 Melke, J. 153 Miao, S. 105

Page

Miller, J. T. 105 Millet, C.-N. 170 Milstein, D. 52 Miner, W. 36 Mishra, R. 202 Miura, A. 227 Modolo, G. 101 Montero, J. 224 Mora Bejarano, M. L. 226 Morgan, K. 223 Mori, K. 226 Muhamad, E. N. 51 Murakumo, T. 69 Murata, K. 205 Murrer, B. 36 Nagarajan, S. Nakatsuji, T. Nakken, T. Narita, H. Naylor, R. Nishimura, T. Nova, I. Nunez, P. Nuss, G. Nutt, M. O.

223 166, 175 83 101 36 89 50 226 106 105

Ó Dubhghaill, C. 202 Obuchi, A. 167 Offer, G. J. 219 Ohara, S. 153, 154 Ouyang, F. 50 Palacio, M. 52 Palmer, S. 78 Palmqvist, A. E. C. 51 Pan, F.-M. 105, 227 Pan, Z. F. 43 Pandey, D. K. 91 Panfilov, P. 138 Panpranot, J. 175 Park, H.-S. 106 Park, J. 50 Park, J.-G. 106 Park, J.-Y. 106 Parkinson, P. 41 Parodi, N. 51 Penfold, G. 25 Pentz, L. 98 Pereira Morais, M. P. 89 Petti, D. 105 Pfaltz, A. 205 Pfeffer, M. 67

231

Page

Phelan, G. D. Phillips, P. R. Pickup, P. G. Pilyugin, V. P. Ploof, C. Pollet, B. G. Poulston, S. Pourshahbaz, M. Prasad, A. K. Prasassarakich, P. Praserthdam, P. Pratsinis, S. E. Price, G. Pridmore, S. Prior, J. Pritzkow, H. Puhakka, E.

106 27 175 138 201 78 112 106 175 105 175 11 86 89 41 50 153

Quisenberry, L. R.

226

Rafiee, E. Raja, R. Rangel, C. M. Rau, J. V. Raykhtsaum, G. Rayment, T. Redinger, J. Rempel, G. L. Reynolds, B. Ricciardi, S. Ricketts, S. R. Riess, M. Robalinho, E. Roberts, W. Robinson, D. J. Rossmeisl, J. Rowsell, L. Rudd, J. Ruiz-Morales, J. C. Ryan, M.

106 50 150 176 202 222 176 105 36 226 51 40 226 225 100 152 112 36 226 216

Saf, R. 106 Sage, P. 25 Samulski, E. T. 51 Sánchez-Loredo, M. G. 102 Sanderson, R. 43 Sanger, G. 36 Santasalo, A. 58 Saruyama, M. 106 Sato, K. 154 Sato, N. 175 Satsuma, A. 164, 165 Sawabe, K. 165 Scandola, F. 45

Page

Schädel, B. T. 175 Schmehl, R. 46 Schmuck, M. 106 Schott, F. J. P. 175 Schulz, G. L. 52 Schuster, H. 25, 201 Shang, L. 227 Shaw, M. 88, 89 Sheu, J.-T. 105 Shibasaki, M. 86, 226 Shimizu, K. 165 Shimon, L. J. W. 52 Shinozaki, K. 106 Shulgin, D. 42 Shunmoogam-Gounden, N. 227 Si, Y. 51 Silva, F. 202 Silva, S. R. P. 50 Singh, D. 91 Singhal, S. C. 147 Sivakumar, T. 50 Sjunnesson, L. 148 Skea, J. 78 Smith, A. W. J. 112 Smith, D. 106 Smith, G. S. 227 Smith, R. A. P. 55, 109 Smolentsev, A. I. 227 Sodeoka, M. 208 Somboonthanakij, S. 175 Somorjai, G. 221 Sorel, C. 101 Sridharan, V. 226 Stabnikov, P. A. 227 Stadelmann, P. A. 70 Stolojan, V. 50 Stone, F. 221 Strauss, J. 25, 201 Stringer, T. 227 Strobel, R. 11 Sullivan, S. P. 175 Sun, S.-G. 106 Sun, Y. 207 Sunjuk, M. 176 Süss, R. 2, 69, 155 Suzuki, K. 203 Sweidan, K. 176 Taguchi, A. Takahashi, N. Takeguchi, T. Takemoto, Y. Takeshita, K.


52 170 51 203 102

Page

Takeuchi, T. 226 Tanaka, K. 206 Tandon, P. 123 Tang, J. 52 Tanizawa, M. 52 Tansey, E. M. 35 Tansey, T. 36 Tao, R. 105 Tasker, P. A. 102 Tattersall, D. 36 Taylor, H. S. 221 Teague, T. 201 Teranishi, T. 106 Terry, L. A. 112 Therrien, B. 227 Thomas, J. M. 50 Thomson, A. 36 Thumberg, M. A. 101 Tian, N. 106 Tian, X. 154 Tierney, B. 40 Tiwari, J. N. 227 Tkachev, S. V. 227 Todd, R. C. 227 Toops, T. J. 170 Trufan, E. 50 Tully, J. 43 Twigg, M. V. 27, 135 Tyler, C. 41 Tzeng, T.-C. 105 Ueda, W. Umetsu, M. Uozumi, Y. Uttam, K. N.

51 154 175 123

Vargas, C. Verdooren, A.

101 202

Wagner, G. Walker, J. Walport, M. Wang, G. Wang, H. Wang, L. Wang, Q. Ward, M. D. Welton, T. Wen, D. Wendt, O. F Wenn, J. Whitby, M. Whitney, S. Wiedwald, U. Wiesner, K.

50 98 36 51 227 176 176 45 176 227 52 36 214 226 227 25, 201

Page

Wilkinson, L. 36 Williams, G. 46 Williams, J. M. J. 86 Williams, R. 36 Williamson, I. 81 Willis, M. 86 Wills, M. 83, 84 Wilson, K. 225 Wiltshaw, E. 36 Wisniewski, M. 102 Wong, M. S. 105 Wong, W.-Y. 176 Woods, T. 36 Woollam, S. F. 100 Wright, J. C. 200, 202 Wright, K. 105 Wu, C.-G. 52 Wu, S.-J. 52 Xie, Y. Xu, J. B.

105 105

Yadawa, P. K. Yamada, Y. M. A. Yamaguchi, T. Yamamoto, H. Yamashita, H. Yamatsugu, K. Yamauchi, M. Yermakov, A. Yezerets, A. Yonkeu, A. York, A. P. E. Yoshioka, N. Yu, X.

91 175 175 204 226 226 227 138 169 176 221 226 175

Zabetakis, D. Zhang, F.-Y. Zhang, J. Zhao, T. S. Zharkova, G. I. Zhou, G.-J. Zhou, Z.-Y. Zhu, L. D. Zhu, R. Ziegenhagen, R. Zielonka, A. Ziemann, P. Zito, D. Zou, X. Zucca, R. Zuo, Y. Züttel, A.

106 175 219 105 227 176 106 105 50 189 25 227 25 227 176 52 84

232

SUBJECT INDEX TO VOLUME 53 Page a = abstract (Z)-Acetamidocinnamic Acid Methyl Ester, reduction 203 Acetoxylation 221 Adsorption, ethylene, Pd-promoted zeolite 112 AFM Probes, Pt-coated Si, thermally-treated, a 52 Alcohols, aerobic oxidation, in H2O, a 175 aliphatic, in alkylation, a 226 benzyl, substituted, in alkylation, a 226 chiral, by reduction of esters 203 EtOH, oxidation 58, 105 electro-, a 106 fuels, for PEFC 58 generation of H2 78 MeOH, electrooxidation, a 227 oxidation, a 227 solvent, a 176 secondary, dynamic kinetic resolution 203 racemisation 203 Aldehydes, addition, across multiple C–C 86 fuels, for PEFC 58 Alkenes, formation 86 hydroacylation 86 hydrogenation, a 105 unfunctionalised, asymmetric reduction 203 Alkylation, 4-hydroxy coumarin, a 226 4-hydroxy-2-quinolones, a 226 quinolin-4(1H)-one, a 226 Alkylidene Carbenoids, by activation of alkynes 86 Alkynes, activation 86 hydroacylation 86 Amides, α-arylation 183 Amination, Buchwald-Hartwig, palladacycle catalysts 67 Amines, coupling reactions 183 Ammonia, storage 164 synthesis 135 Antimicrobial Agents 11 Apparatus and Technique, a 51, 227 Aryl Halides, coupling reactions 183 α-Arylation, amides 183 esters 183 Autocatalysts, new production facility, for Russia 98 pgm demand, impact of CO2 legislation 179 recycling 40 Bacteria, catalytic inactivation, a Biomedical and Dental, a Book Reviews, “Carbons and Carbon Supported Catalysts in Hydroprocessing” “Fuel Processing: for Fuel Cells” “Palladacycles: Synthesis, Characterization and Applications” “PEM Fuel Cell Electrocatalysts and Catalyst Layers: Fundamentals and Applications” “Photochemistry and Photophysics of Coordination Compounds”, Parts I & II “The Discovery, Use and Impact of Platinum Salts as Chemotherapy Agents for Cancer” Buchwald-Hartwig Amination, palladacycle catalysts Butane, steam reforming, a

226 227 135 172 67 219 45 35 67 175

CAD/CAM, jewellery 21, 198 Cancer, anti-, drugs, cisplatin 35 palladacycles 67 Pt compounds, a 227 Capacitors, DRAM, Ru bottom electrodes, a 106 Carbon, pgm/activated charcoal, catalysts 135 pgm/C, catalysts 135 supported catalysts, hydroprocessing 135 Carbon Oxides, CO, clean-up, in fuel processing 172 contaminated gas, low pressure operation of PEFC 147 emissions, diesel 179


Page Carbon Oxides, CO, (cont.) + H2, reduction of NOx, lean conditions, a 175 + O2 221 oxidation, in diesel exhaust, a 226 selective catalytic reduction 164 selective oxidation 11 tolerant catalysts, for PEM fuel cells 219 CO2, emissions, legislation 179 Casting, industrial, Pt 209 investment, Pd alloys 21, 198 Pt alloys 21, 198 Catalysed Soot Filters 27, 179 Catalysis, Applied and Physical Aspects, a 50, 105, 226 asymmetric 203 book reviews 67, 135 concepts 221 conferences 86, 164, 203, 221 methodology 221 Reactions, a 50, 105, 175, 226 theories 221 Catalysts, book reviews 67, 135 C supported, hydroprocessing 135 four-way, see Four-Way Catalysts heterogeneous, precious metals, for industry 40 surface characterisation, by XPS 55, 109 leaching, for new catalytic reactions, a 105 NOx control 27 petroleum, spent, sampling 40 pgm/activated charcoal, preparation 135 pgm/C, preparation 135 pgms, catalytic aftertreatment, vehicle emissions 221 precious metals, treatment, in plasma heater reactors 40 recycling, a 50, 226 refinery, precious metals, treatment, in PlasmaEnvi® 40 supported pgms, by flame synthesis 11 three-way, see Three-Way Catalysts Catalysts, Iridium, Ir/γ-Al2O3, soot and NOx removal, a 50 Ir/ZSM-5, soot and NOx removal, a 50 IrBa/WO3-SiO2, CO-SCR 164 Catalysts, Iridium Complexes, [Cp*IrCl2]2, alkylation, 4-hydroxy coumarin, 4-hydroxy-2-quinolones, quinolin-4(1H)-one, solvent-free heating, a 226 ‘hydrogen borrowing’, for formation of C–C, C–N 86 [Ir(COD)(PCy3)(py)]PF6, hydrogenation of NRL, a 105 TM Ir Me-BoPhoz , reduction of α,β-enoic acids 203 Ir phosphoramidites, synthesis of phenylalanines 203 Ir(III) quinolyl-functionalised Cp, hydrogenation, a 50 P,N-ligands, asymmetric reduction of alkenes 203 Catalysts, Osmium Complexes, OsO4 immobilised onto polystyrene-sg-imidazolium resin, dihydroxylation of olefins, a 50 Catalysts, Palladium, Au-Pd, direct synthesis of H2O2 221 preparation, pretreatment 221 Au-Pd/Al2O3, direct synthesis of H2O2 221 221 Au-Pd/C, direct synthesis of H2O2 Au-Pd/TiO2, direct synthesis of H2O2 221 Co/Pd-HFER, NO2-CH4 reaction 164 combustion, in fuel processing 172 diesel emission control systems 179 diesel oxidation catalysts 174 electrocatalysts, Pd-based, formic acid oxidation 58 Pd/C, anodes, for DFAFC, a 175 Pd/TiO2/C, anodes, for PEFC, a 51 Pd-Pt/hollow core mesoporous shell C, for PEMFC 147 Pt-Pd/C, for DEFCs, a 51 PdRu nanoparticles, anodes, for DMFC 147 nano-Pd/SiO2, 1-heptyne hydrogenation, a 175 by one-step flame spray pyrolysis, a 175 Pd(111), CO + O2 221 Pd, + Au, acetoxylation 221 + Bi additive, hydrogenation 221 hydrodechlorination, a 105

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Catalysts, Palladium, (cont.) Pd-on-Au, hydrodechlorination, a 105 Pd/activated charcoal, hydrogen activation 135 164 Pd-Al2O3, NO+H2+O2 Pd/Al2O3, Ar plasma reduced; glucose selective oxidation, a 50 C5 olefin hydrogenation 221 effect of S, diesel oxidation, a 105 enantioselective hydrogenation 11 H2 thermally reduced; glucose selective oxidation, a 50 Pd/Ba/Al2O3, NOx storage 164 Pd/bentonite, hydrogenation of citral, a 50 preparation, effect of reduction, a 50 Pd/C, C–C bond forming processes 135 direct carbonylation reactions 135 dissociative H2 chemisorption 135 hydrogenation reactions 135 hydrogenolysis reactions 135 Pd/C black, hydrogen activation 135 Pd/CeO2, effect of S, diesel oxidation, a 105 Pd/graphite, hydrogen activation 135 Pd/La-Al2O3, catalytic combustion 11 Pd-LaCoO3, NO+H2+O2 164 Pd/La2O3, catalytic combustion 11 Pd/sepiolite, Heck reactions, a 105 hydrogenation of alkenes, a 105 preparation, using an ionic liquid, a 105 Pd/SiO2, 1-heptyne hydrogenation, a 175 hydrogenation 11 Pd/TiO2, inactivation of bacteria, a 226 Pd/ZrO2, effect of S, diesel oxidation, a 105 Pd-fullerite, 1-ethynyl-1-cyclohexanol hydrogenation, a 50 Pd-Pt/Al2O3, CH4 combustion 11 Pt/Pd, catalysed soot filter 27 diesel oxidation catalyst 27, 37 Pt/Pd/Au, diesel oxidation catalyst 37 Catalysts, Palladium Complexes, amphiphilic resindispersion of Pd nanoparticles: aerobic oxidation of alcohols, in H2O; hydrodechlorination of chloroarenes, a 175 palladacycles, Buchwald-Hartwig amination 67 Heck, Sonogashira, Suzuki couplings 67 t [Pd(μ-Br)( Bu3P)]2, alkyl thiols + aryl bromides 183 alkyl thiols + aryl iodides 183 aryl bromides + benzenethiol 183 aryl chlorides + amines 183 α-arylation of amides, esters 183 carbon–carbon bond formation 183 carbon–heteroatom coupling 183 characteristics 183 cyanation 183 handling 183 N-cyclohexylaniline + bromobenzene 183 N-methylaniline + 3-bromothiophene 183 183 O2 sensitivity Suzuki coupling of sterically bulky aryl bromides 183 α-vinylation of esters, ketones 183 Pd enolate + DM-SEGPHOS, aldol reaction 203 α-fluorination reaction 203 Mannich reaction 203 Michael reaction 203 Pd(OAc)2 + BINAP, N-cyclohexylaniline + bromobenzene 183 t Pd(OAc)2 + Bu3P, N-cyclohexylaniline + bromobenzene 183 Pd(OAc)2 + Xantphos, N-cyclohexylaniline + bromobenzene 183 Pd particles/organic S ligands/phosphanes, synthesis of cyclic vinyl sulfides, a 105 Pd particles/organic Se ligands/phosphanes, synthesis of cyclic vinylt selenides, a 105 t ( Bu3P)Pd(0), from [Pd(μ-Br)( Bu3P)]2 183 Catalysts, Platinum, Ba-K/Pt-Rh/A-ZT, NOx storage and reduction 164 Ba-K/Pt-Rh/AZT, NOx storage and reduction 164

Catalysts, Platinum, (cont.) CO clean-up, in fuel processing 172 combustion, in fuel processing 172 diesel aftertreatment 179 175 electrocatalysts, Corich core-Ptrich shell/C, ORR, a Pd-Pt/hollow core mesoporous shell C, for PEMFC 147 Pt, anodes, for PEMFC 147 sieve printed, for PEMFC, a 226 cathodes, for fuel cells 147 for MFC 147 for PEMFC 147 sieve printed, for PEMFC, a 226 for SOFC, a 226 electrodes, for PEMFC 147 spray printed, for PEMFC, a 226 MEAs, for PEMFC 147 for PEMFC 175, 219 Pt/C, anodes, for PEFC, a 51 cathodes, for DMFC 147 electrodes, for DEFC 147 Pt/Vulcan XC-72 C, cathodes, for PEFCs 58 Pt-Au, surface characterisation, by XPS 55, 109 Pt-Bi, formic acid oxidation 58 Pt3Ni, cathodes, for fuel cells 147 Pt-Pd/C, for DEFCs, a 51 PtRu, anodes, for DMFC 147 Pt-Ru, anodes, for PEFC 147 for PEM fuel cells 219 Pt-Ru/C, anodes, for DMFC 147 electrodes, for DEFC 147 Pt-Ru/Vulcan XC-72 C, anodes, for PEFCs 58 Pt-Sn, ethanol oxidation 58 Pt-Sn/C, electrodes, for DEFC 147 PtZn nanoparticles, for fuel cells, a 227 FePt-γ-CD, aqueous hydrogenations, a 226 Pd-Pt/Al2O3, CH4 combustion 11 production of H2SO4 40 Pt, catalysed soot filter 27 diesel oxidation catalyst 27 layer, diesel particulate filter 37 Pt/activated charcoal, hydrogen activation 135 Pt/Al2O3, by flame synthesis 11 by precipitation/impregnation 11 combustion of CO 164 enantioselective hydrogenation 11 Pt/γ-Al2O3, removal of soot and NOx, a 50 Pt/Al2O3 washcoat, diesel oxidation catalyst, a 226 Pt/(75% Al-21% BaCO3-2% K2CO3), NOx storage 164 Pt-Ba/Al2O3, lean NOx trap, regeneration with H2, a 50 Pt/Ba/Al2O3 washcoat, lean NOx trap 164 Pt/Ba/ZrO2/Al2O3, four-way catalyst 164 11 Pt/BaCO3/Al2O3, NOx storage-reduction Pt/C, dissociative H2 chemisorption 135 Pt/C black, hydrogen activation 135 Pt/Ce-Pr-ZrOx, NOx storage 164 Pt/CeO2, NH3 storage 164 Pt/CeO2-Al2O3, NOx storage and reduction 164 Pt sintering 164 Pt/CexZr1–xO2, three-way catalyst 11 Pt/graphite, hydrogen activation 135 Pt/TiO2, inactivation of bacteria, a 226 oxidation 11 photocatalysis 11 Pt/WO3/ZrO2, NOx + H2, in O2-rich exhaust, a 175 Pt-Ni/alumina, oxidative steam reforming 147 Pt/Pd, catalysed soot filter 27 diesel oxidation catalyst 27, 37 Pt/Pd/Au, diesel oxidation catalyst 37 Pt-Rh/Al2O3, partial oxidation of CH4 11 Pt-Rh/Ba/Al2O3, NSR model catalyst, a 226 + SCR catalyst, a 226 NOx abatement, a 226 PtSn2, selective hydrogenation, a 50 Catalysts, Platinum Complexes, activation of alkynes 86 amphiphilic resin-dispersion of Pt nanoparticles, a 175


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Page Catalysts, Rhodium, Ba-K/Pt-Rh/A-ZT, NOx storage and reduction 164 Ba-K/Pt-Rh/AZT, NOx storage and reduction 164 exhaust gas reforming 221 11 Pt-Rh/Al2O3, partial oxidation of CH4 Pt-Rh/Ba/Al2O3, NSR model catalyst, a 226 + SCR catalyst, a 226 NOx abatement, a 226 reforming, in fuel processing 172 Rh/Al2O3, selective hydrogenation 11 Rh/C, dissociative H2 chemisorption 135 hydrogenation of oximes 203 Rh/CexZr1–xO2, syngas production 11 Rh/cordierite monolithic honeycomb, reforming, a 175 Rh nanoparticles/zeolite, lean NOx–CO–H2, a 175 RhOx nanoparticles/zeolite, lean NOx–CO–H2, a 175 RhSn2, selective hydrogenation, a 50 Catalysts, Rhodium Complexes, H2 from alcohols 78 Rh BINAP, [2 + 2 + 2] cycloadditions, for preparation of axial chiral aromatic compounds 203 Rh(CO)2(acac) + DiazaPhos-SPE, hydroformylation 203 Rh(dppe)]ClO4, addition of aldehydes across multiple C–C, + C–H activation and C–C formation 86 Rh H8-BINAP, [2 + 2 + 2] cycloadditions, for preparation of axial chiral aromatic compounds 203 Rh MandyPhosTM, asymmetric hydrogenation 203 Rh Me-BoPhozTM, reduction of α,β-enoic acids 203 Rh MonoPhosTM, asymmetric hydrogenation 203 preparation of Aliskiren 203 Rh(nbd)2, P,N-complex; P,P-complex, asymmetric reduction of (Z)-acetamidocinnamic acid methyl ester 203 Rh(III) quinolyl-functionalised Cp, hydrogenation, a 50 Rh SEGPHOS®, [2 + 2 + 2] cycloadditions, for preparation of axial chiral aromatic compounds 203 Rh TangPhos, reduction of dehydroamino acids 203 reduction of enamides 203 reduction of itaconates 203 Rh–Xyl-PhanePhos, reduction of α,β-enoic acids 203 Catalysts, Ruthenium, electrocatalysts, PdRu nanoparticles, anodes, for DMFC 147 PtRu, anodes, for DMFC 147 Pt-Ru, anodes, for PEFC 147 for PEM fuel cells 219 Pt-Ru/C, anodes, for DMFC 147 electrodes, for DEFC 147 Pt-Ru/Vulcan XC-72 C, anodes, for PEFCs 58 Ru/C, ammonia synthesis 135 RuSn2, selective hydrogenation, a 50 Catalysts, Ruthenium Complexes, asymmetric transfer hydrogenation of ketones 203 bis(η5-2,4-dimethylpentadienyl)ruthenium(II) + MandyPhosTM, asymmetric hydrogenation 203 generation of H2, from alcohols 78 5 – + [HNEt3] [(Ru{η -C5H5}{PPh3}2)2(PW12O40)] 221 ‘hydrogen borrowing’, for formation of C–C, C–N 86 monomeric, secondary alcohol racemisation 203 [RuCl2(P-Phos)(DMF)n], reduction of α,β-enoic acids 203 reduction of γ,δ-enoic acids 203 RuCl2[(R)-P-Phos][(S)-DAIPEN], aryl ketone reduction 203 RuCl2[(S)-xyl-P-Phos][(S)-DAIPEN], in synthesis of imidazol[1,2-a]pyridine BYK-311319 203 RuCl3, dihydroxylation, in synthesis of Tamiflu®, a 226 Ru–diamine, reduction of esters 203 ® Ru–DM-SEGPHOS , synthesis of sitagliptin 203 Ru MonoPhosTM, reduction of carbonyl groups 203 Shvo catalyst, secondary alcohol racemisation 203 Ceramic Fusion Technique, PdAlRu alloys 189 Chemistry, a 52, 106, 176, 227 Chemotherapy Agents, for cancer, Pt salts 35 Chlorinated Ethenes, hydrodechlorination, a 105 Chloroarenes, hydrodechlorination, a 175 Chorine, corrosion of Pt, a 176 Cisplatin 35 Citral, vapour-phase selective hydrogenation, a 50


Page Colloids, Pd-Sn, inkjet printing, a Combustion, catalytic CH4 in fuel processing Composites, Pt nanoparticle–graphene, a Conferences, 32nd Annual Conference of Precious Metals, U.S.A., 2008 Fuel Cells Science and Technology 2008, Denmark Hydrogen Fuel Cells: For a Low Carbon Future, U.K., 2008 5th International Conference on Environmental Catalysis, Northern Ireland, 2008 18th International Solvent Extraction Conference, U.S.A., 2008 Metals in Synthesis 2008, U.K. Novel Chiral Chemistries Japan 2009 SAE 2008 World Congress, U.S.A. 22nd Santa Fe Symposium®, U.S.A., 2008 23rd Santa Fe Symposium®, U.S.A., 2009 The Taylor Conference 2009, U.K. Corrosion, Pt, Cl2-induced, a Coupling Reactions, C–C C–heteroatom palladacycle catalysts Creep, Pt86:Al10:Z4, Z = Cr, Ir, Ru CVD, precursors, Pd β-ketoiminates, a Cyanation Cycloaddition, [2 + 2 + 2], preparation of axial chiral aromatic compounds 1,5,9-Cyclododecatriene, selective hydrogenation, a Cyclododecene, from 1,5,9-cyclododecatriene, a

106 11 11 172 51 40 147 78 164 100 86 203 37 21 198 221 176 183 183 67 2 227 183 203 50 50

Defect Structure, polycrystalline Ir 138 Deformation, plastic, polycrystalline Ir 138 Dendrimers, G4.5-COOCH3 PAMAM, + Pd2+, a 176 Dental, alloys, Pd-Ag-based 21 Pd74.0-In5.0-Cu14.5Ga1.6Sn4.9 21 Deuterium, permeation, Pd81Pt19 membrane, a 51 Diatomic Molecules, PtC, PtH, PtN, PtO, properties 123 Diesel, emissions control 27, 37, 164, 174, 179, 226 engines 179 exhaust gas mixtures, a 105 particulate matter, emissions, control 27 Diesel Oxidation Catalysts 27, 37, 105, 174, 179, 226 Diesel Particulate Filters 27, 37, 179 Dihydroxylation, olefins, a 50 ® in synthesis of Tamiflu , a 226 DMSO, solvent, a 176 Dynamic Kinetic Resolution, secondary alcohols 203 Elastic Constants, higher-order, Os, Ru 91 Electrical and Electronics, a 52, 106 Electrochemistry, a 106 preparation, of Pd nanorods, with high-index facets, a 106 Electrodeposition, CoPt nanowires, a 51 Electrodes, bottom, Ru, in DRAM capacitors, a 106 in Fuel Cells Pd, EtOH oxidation, a 105 Pt, in dye sensitised solar cells 216 Electroless Plating, Cu, using a Pd-Sn catalyst, a 106 Pd films, on 316L stainless steel, a 52 Electroplating, Pd films, on 316L stainless steel, a 52 Emissions Control, a 50, 105, 175, 226 CO2 179 diesel 27, 37, 164, 174, 179, 226 gasoline 164, 179 motor vehicles, legislation, in Russia 98 vehicle 221 Engineering Stress-Strain Curve, Pd alloys 189 Engines, diesel 179 gasoline 179 α,β β-Enoic Acids, reduction 203 γ,δδ-Enoic Acids, reduction 203 Enthalpy, PtC, PtH, PtN, PtO 123 Entropy, PtC, PtH, PtN, PtO 123

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Page Esters, α-arylation reduction α-vinylation Ethane, steam reforming, a Ethylene, adsorption, Pd-promoted zeolite scavenger, Pd-promoted zeolite 1-Ethynyl-1-cyclohexanol, hydrogenation, a Extraction, metals, conference

183 203 183 175 112 112 50 100

Films, FePt, oxidation behaviour, a 227 Pd, on 316L stainless steel, a 52 ‘Final Analysis’ 55, 109, 179 175 Flame Spray Pyrolysis, one-step, nano-Pd/SiO2, a Flame Synthesis, supported pgms 11 Formic Acid, electrooxidation, a 175, 227 fuel, for PEFC 58 generation of H2 78 oxidation 58 Four-Way Catalysts 27, 164 Fracture Strain, Pd alloys 189 PtRuGa 189 Fruit, climacteric, control of ethylene-induced ripening 112 Fuel Cells, a 51, 105, 175, 226–227 book reviews 172, 219 buildings 78 catalyst layers 219 catalysts, PtZn nanoparticles, a 227 cathodes, Pt, Pt alloys, DFT 147 conferences 78, 147 DEFC, electrocatalysts, a 51 electrodes, reaction mechanism, structural changes 147 DFAFC, anode catalysts, deactivation, reactivation, a 175 DMFC, anode catalysts 147 passive monopolar mini-stacks 147 portable electric power sources 147 vapour-fed 147 electrocatalysts 219 Pt-Au, surface characterisation, by XPS 55, 109 in Europe 78 fuel, processing 172 “Fuel Cell Today Industry Review 2009” 104 fuels 58, 78, 147, 172 membrane electrode assemblies 58 durability 147 MFC, anodes, cathodes, membranes 147 PEFC, anodes, electrocatalysts, a 51 Pt-Ru/Vulcan XC-72 C 58 cathodes, Pt/Vulcan XC-72 C 58 fuels, acetaldehyde, ethylene glycol, EtOH, formaldehyde, formic acid, glycerol, MeOH, 1-propanol, 2-propanol 58 influence of NaCl vapour 147 liquid fuels 58 low pressure operation, using CO contaminated gas 147 MEAs, preparation 58 PEMFC, anodes 147 buildings 78 canal boat 78 catalyst layer degradation, XPS characterisation, a 175 catalyst layers 219 catalysts 147 cathode catalysts, using modelling aproach 147 CO-tolerant catalysts 219 electrocatalysts 219 electrodes 147 FlowCathTM technology 147 H2 contamination, by Hg 147 high temperature 147 MEAs, by sieve printing method, a 226 by spray printing method, a 226 durability 147 reversal-tolerant catalyst layers 219 pgms, importance 40 SOFC, cathode, constant phase element, a 226 transport 78


Page Fuels, acetaldehyde C-based diesel ethylene glycol EtOH formaldehyde formic acid gasoline glycerol H2, for fuel cells MeOH processing 1-propanol 2-propanol

58 172 179 58 58 58 58 179 58 58, 78, 147, 172 58 172 58 58

Gasoline, emissions control 164, 179 engines, downsized 179 Gibbs Energy, PtC, PtH, PtN, PtO 123 Glass, making, Pt equipment 40 Gluconic Acid, from glucose, a 50 Glucose, biosensor, a 227 selective oxidation, a 50 Grinding, Pt(5dpb)Cl, luminescence colour change, a 106 Hardness, Pd alloys 21, 189, 198 Pt 155, 198 Pt alloys 21, 155, 198 Heck Reactions, palladacycle catalysts 67 Pd/sepiolite, a 105 1-Heptyne, hydrogenation, a 175 1-Hexane, hydrogenation, a 50 High Temperature, Pt-based alloys 2, 69, 155 History, cisplatin, cancer drug 35 melting of Pt 209 Hydroacylation, alkenes, alkynes 86 Hydrocarbons, emissions, diesel 179 oxidation, in diesel exhaust, a 226 oxidative steam reforming 147 selective catalytic reduction 164 Hydrodechlorination, chlorinated ethenes, a 105 chloroarenes, in H2O, a 175 Hydroformylation, asymmetric 203 Hydrogen, absorption, Pd-Au nanoparticles, a 227 activation, Pd/C, Pt/C 135 borrowing, for formation of C–C, C–N 86 by exhaust gas reforming 221 by oxidative steam reforming 147 by photogeneration 45 + CO, reduction of NOx, lean conditions, a 175 contamination, by Hg, for PEMFC 147 dissociative chemisorption, Pd/C, Pt/C, Rh/C 135 fuel, for fuel cells 58, 78, 147, 172 fuelling station requirements 78 generation 58, 78, 147 164 + NO, + H2 photocatalysis 45 production 40 purification, Pd membranes 40 reduction, of NOx, on lean NOx traps, a 50 reduction of NOx, in O2-rich exhaust, a 175 sensors 147 storage 78 as NH3 147 uptake, Pd/activated C, a 176 vehicles 78 Hydrogen Peroxide, direct synthesis 221 Hydrogenation, alkenes, a 105 asymmetric 203 preparation of phenylalanines 203 in synthesis of sitagliptin 203 unsaturated C–C multiple bonds 203 asymmetric transfer, ketones 203 C5 olefin 221 catalyst additives 221 enantioselective, flame-made catalysts 11

236

Hydrogenation, (cont.) 1-ethynyl-1-cyclohexanol, a flame-made catalysts in H2O, a 1-heptyne, a 1-hexane, a natural rubber latex, a oximes selective vapour-phase, citral, a transfer Hydrometallurgy, conference Hydroprocessing, C supported catalysts Imines, formation reduction Inkjet Printing, Pd-Sn colloids, a Ionic Liquids, catalyst preparation, a solvent, a in solvent extraction Iridium, arc melting electron beam melting melting polycrystalline, defect structure high purity plastic deformation single crystals Iridium Alloys, Pt-Al-Ir, high temperature Pt-10%Ir, investment casting with Re and Ru Iridium Complexes, dye sensitised solar cells Ir(III), octahedral, photophysical properties spectroscopic properties OLEDs Ir(III) fluorenone-ppy, electrophosphorescence, a Ir(III) phenylpyridines, solar cells, a Iridium Compounds, IrB1.35, hard, hardness, a

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50 11 226 175 50 105 203 11, 50 50 78 100 135

Melting, (cont.) arc melting, electron beam heating, induction heating 209 Membranes, Pd, H2 purification 40 51 Pd81Pt19, D2 permeation, a Metallurgy and Materials, a 51, 105–106, 176, 227 Metals Extraction, conference 100 Methane, + NO2 164 combustion 11 internal reforming 147 partial oxidation 11 steam reforming, a 175 Microwaves, synthesis of Pd-Pt/C, for PEMFC 147 Mokume Gane, jewellery 198

86 203 106 105 176 100 209 209 209 138 138 138 138 2 21 138 216 45 45 45 176 52 176

Jewellery, CAD/CAM 21, 198 mokume gane 198 Pd 198 Pd alloys 21, 189, 198 Pt, bench-scale repair, using blowpipes 209 lasers, manufacture, repair 21 manufacture 21, 198 Pt alloys 21, 189, 198 Johnson Matthey, autocatalyst production, Russia 98 catalysts 183, 203 ethylene scavanger 112 melting of Pt 209 “Platinum 2008 Interim Review” 48 “Platinum 2009” 174 β-Keto Esters, reduction Ketones, aryl, reduction asymmetric transfer hydrogenation α-vinylation

203 203 203 183

Lasers, Pt jewellery, manufacture, repair 21 Lattice Misfits, Pt86Al10Z4, Z = Cr, Ir, Ru, Ta, Ti 69 Leaching, catalysts, for new catalytic reactions, a 105 Lean NOx Traps 37, 164 regeneration with H2, a 50 Liquid Crystals, palladacycles 67 Luminescence, colour change, grinding, Pt(5dpb)Cl, a 106 Pt octaethylporphyrin, a 51 Magnetism, CoPt nanowires, a FePt-γ-CD, a Markets, precious metals MEAs, durability, in PEM fuel cells preparation Mechanical Properties, Pt-based ternary alloys Melting, PdGaIn, arc melting, under Ar pgms, history


51 226 40 147 58 2 198 209

Nanocomposites, Pt nanoparticles/C MWNTs, a 227 Nanoflakes, Pd–PdO core–shell, on Pt, a 105 Nanoflowers, Pt, a 227 Nanoparticles, Corich core-Ptrich shell, a 175 FePt, a 226, 227 nano-Pd/SiO2, a 175 particulate matter 27 patchy, CdS/PdxCdyS/CdS, PdSx/Co9S8, a 106 Pd 50, 67, 105, 175, 176 PVP-protected, a 227 Pd on Au, a 105 Pd-Au, a 227 Pd-polymer (DNA) hybrid 147 PdRu 147 Pt, a 51, 175, 227 PtZn, a 227 Rh, a 175 RhOx, a 175 Nanorods, Pd, a 106 Nanowires, CoPt, a 51 Natural Gas, steam reforming, a 175 Nitrogen Oxides, NO, + H2, + O2 164 oxidation, in diesel exhaust, a 226 NO2, + CH4 164 NOx, control catalysts 27 emissions, diesel 164, 179 lean, reduction, by CO, H2, a 175 traps 37 regeneration with H2, a 50 reduction 50, 164 by H2, in O2-rich exhaust, a 175 removal, a 50 from diesel exhaust 221 under a lean/rich atmosphere, a 226 selective catalytic reduction 27, 179 storage 164 catalysts, model 164 storage-reduction 11 traps, diesel 179 lean 164 catalysts, S removal 164 thermal ageing 164 31 106 NMR, P, Pd(OAc)2 + dppf, a NOx Storage and Reduction 164, 226 OLEDs, Ir(III), Os(II), Pt(II) complexes Olefins, C5, hydrogenation dihydroxylation, a Osmium, higher-order elastic constants sound velocity ultrasonic attenuation coefficients ultrasonic velocity Osmium Complexes, Os(II), OLEDs [Os(L–L)2(N–N)]2+, phosphorescence, a [Os(N–N)2(L–L)]2+, phosphorescence, a photoinduced electron-transfer photoinduced energy-transfer Oxidation, aerobic, alcohols, in H2O, a by flame-made catalysts CO, in diesel exhaust, a electro-, EtOH, a

45 221 50 91 91 91 91 45 106 106 45 45 175 11 226 106

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Page Oxidation, (cont.) formic acid, a MeOH, a EtOH FePt nanoparticles, a formic acid HC, in diesel exhaust, a isothermal, Pt-Al-Z, Z = Cr, Ir, Re, Ru, Ta, Ti Pt86:Al10:Z4, Z = Cr, Ir, Ru, Ti MeOH, a NO, in diesel exhaust, a partial, CH4 particulate matter Pt-based ternary alloys selective, CO glucose, a Oximes, hydrogenation Oxygen, + CO reduction reaction, a sensors, a

175, 227 227 58, 105 227 58 226 2 2 227 226 11 27 2 11 50 203 221 175 51

Palladacycles, anticancer 67 applications 67 catalysts, for cross-coupling reactions 67 characterisation 67 Hermann’s 67 liquid crystals 67 photophysical properties 67 synthesis 67 thermal stability 67 Palladium, electrodes, EtOH oxidation, a 105 films, electroless plated, on 316L stainless steel, a 52 electroplated, on 316L stainless steel, a 52 high temperature interface reaction, SiC, TiC, TiN, a 105 jewellery 198 melting 209 membranes, H2 purification 40 nanocrystalline, H2 uptake, a 176 nanoparticles 50, 67, 105 PVP-protected, a 227 nanorods, electrochemical preparation, a 106 with high-index facets, a 106 particles, dispersed over zeolite 112 Pd/activated C fibre, H2 uptake, a 176 Pd-on-Au nanoparticles, a 105 Pd nanoparticles/microporous activated C, H2 uptake, a 176 Pd–PdO core–shell nanoflakes, on Pt, a 105 Pd-polymer (DNA) hybrid nanoparticles, H2 sensors 147 Pd-promoted zeolite, ethylene adsorption 112 ethylene scavenger 112 Pd-Sn colloids, catalyst, electroless Cu metallisation, a 106 inkjet printing, a 106 Palladium Alloys, 950, burnishing, hardness, surface 198 investment casting 198 for jewellery 21, 189, 198 mokume gane 198 AuPdCu, fracture strain 189 hardness 189 tensile strength 189 yield strength 189 fusion of coloured ceramic overlays 189 hardness 21, 189, 198 investment casting 21, 198 jewellery 21, 189, 198 MgPd, from Mg6Pd, a 176 Mg6Pd, preparation, hydriding, a 176 Pd950G, Pd-Ga-Ag-In, casting 21 scrap, recycling 21 Pd-Ag-based, dental 21 950 Pd-Ag-Ga-Cu, casting 21 Pd95.5Al1.9Mg2.6, hardness 189 Pd95.5Al3.8Mg0.7, hardness 189 PdAlRu, mechanical behaviour 189 Pd95.5Al0.9Ru3.6, annealed, eng. stress-strain curves 189 XRD pattern 189


Page Palladium Alloys, (cont.) colour 189 density 189 fracture strain 189 hardness 189 Poisson’s ratio 189 ultimate tensile strength 189 workability 189 yield strength 189 Young’s modulus 189 189 Pd95.5Al2.8Ru1.7, annealed, eng. stress-strain curves colour 189 density 189 fracture strain 189 hardness 189 Poisson’s ratio 189 ultimate tensile strength 189 workability 189 yield strength 189 Young’s modulus 189 Pd95.5Al0.4Ti4.1, hardness 189 Pd95.5Al1.3Ti3.2, hardness 189 Pd-Au nanoparticles, H2 absorption, a 227 PdCu, hardness 189 PdGa, hardness 189 PdGaIn, arc melting, under Ar 198 investment casting 198 Pd-In, thermochemistry, a 51 Pd74.0-In5.0-Cu14.5Ga1.6Sn4.9, dental 21 950 Pd-Nb-Ga 21 Pd81Pt19 membrane, D2 permeation, a 51 PdRu, fracture strain 189 hardness 189 tensile strength 189 yield strength 189 950 Pd-Ru-Ga, casting 21 Pd-Sn, thermochemistry, a 51 Pd-Zn, thermochemistry, a 51 watchmaking 189 Palladium Complexes, PCP-pincer Pd hydride– K-Selectride®, a 52 (PCP)i-PrPdCl + K-Selectride®, a 52 Pd(II), recovery, from HCl, in presence of Pt(IV), using S-containing monoamide, diamide 100 solvent extraction, pyridine carboxamide and phosphonium ionic liquid systems 100 copolymers, N-isopropylacrylamide and thioethers 100 Pd(II) chloro, solvent extraction, tren polyamines 100 [Pd(dppf)(OAc)2], 31P NMR, a 106 Pd(II) fluorinated benzoporphyrins, phosphorescence, a 106 Pd(II)-functionalised diphosphines, H2O soluble, a 176 176 Pd2+ + G4.5-COOCH3 PAMAM dendrimers, a Pd β-ketoiminates, CVD precursors, a 227 31 Pd(OAc)2 + dppf, P NMR, a 106 Pd(OAc)2 + functionalised diphosphine, a 176 Pd(PPh3)2Cl2/ethylene-bridged dithiosemicarbazones, a 227 /phenylene-bridged dithiosemicarbazones, a 227 Pd(II) salicylaldimine dithiosemicarbazones, a 227 solvent extraction, using hydroxyoxime LIX 84I 100 using malonamide DMDOHEMA 100 tetrakis(triphenylphosphine)palladium, precusor, a 50 Palladium Compounds, MgD2, by hydrogentation, a 176 nanoparticles, patchy, CdS/PdxCdyS/CdS, PdSx/Co9S8, a 106 palladacycles, see Palladacycles Pd–PdO core–shell nanoflakes, on Pt, a 105 PdHx, destabilisation, a 176 Particles, nanosized, Zn2PtO4, a 51 Pd, dispersed over zeolite 112 Particulate Matter, emissions, diesel 27, 179 Patents 53–54, 107–108, 177–178, 228–229 Permeation, D2, Pd81Pt19 membrane, a 51 Phase Diagrams, Pt-Al-Co, Pt-Ni-Ru 155 Phenylalanines, by asymmetric hydrogenation 203 Phosphines, pgm complexes, in catalysis 203 Phosphorescence, electro-, Ir(III) fluorenone-ppy, a 176

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Phosphorescence, (cont.) Pt(II) fluorenone-ppy, a 176 NIR, Pd(II) with fluorinated benzoporphyrins, a 106 Pt(II) with fluorinated benzoporphyrins, a 106 2+ 2+ 106 [Os(L–L)2(N–N)] , [Os(N–N)2(L–L)] , a Photocatalysis 11 Ru complexes 45 sterilisation of Escherichia coli, a 226 Photochemistry, pgm complexes 45 Photoconversion, a 52, 106, 176 Photophysical Properties, palladacycles 67 Photophysics, pgm complexes 45 Photoproperties, pgm complexes 45 Photosynthesis, ‘artificial’, Ru complexes 45 Platinum, arc melting 209 availability 40 coating, Si AFM probes, a 52 corrosion, Cl2-induced, a 176 electrodes, in dye sensitised solar cells 216 electron beam heating 209 equipment, glass industry 40 FePt film, oxidation behaviour, a 227 FePt nanoparticles, oxidation behaviour, a 227 hardness 155, 198 induction heating 209 industrial casting 209 jewellery, lasers, manufacture, repair 21 manufacture 21, 198 melting 209 nanoflowers, a 227 nanoparticles, a 51 Pd–PdO core–shell nanoflakes, on Pt, a 105 Pt nanoparticle–graphene composite, a 51 Pt nanoparticles/C MWNTs, glucose biosensor, a 227 segregation, in FePt nanoparticles, a 227 stress-rupture curve 2 thin films, on SiO2 particles, by barrel sputtering, a 52 ZGS, stress-rupture curve 2 Platinum Alloys, 950, burnishing, hardness, surface 198 investment casting 198 jewellery 21, 198 casting, effect of CAD/CAM-derived materials 21 colour 189 CoPt nanowires, electrodeposition, a 51 magnetic properties, microstructural properties, a 51 hardness 21, 155, 189 investment casting 21, 198 jewellery 21, 189, 198 Pd81Pt19 membrane, D2 permeation, a 51 Pt-Al, high temperature 2 Pt85:Al15, in situ high temperature TEM 69 69 Pt86Al14, Pt3Al precipitate, TEM Pt-Al-Co, hardness 155 phase diagram 155 Pt-Al-Co-Cr-Ru, hardness 155 Pt-Al-Cr, high temperature 2 Pt86:Al10:Cr4, tensile testing 155 Pt79.5:Al10.5:Cr5.5:Ru4.5, Vickers hardness 155 Pt80:Al14:Cr3:Ru3 155 Pt80.5:Al12.5:Cr4.5:Ru2.5, Vickers hardness 155 Pt81.5:Al11.5:Cr4.5:Ru2.5, Vickers hardness 155 Pt83:Al11:Cr3.5:Ru2.5, Vickers hardness 155 Pt84:Al11:Cr3:Ru2, oxidation resistance 155 tensile testing 155 Pt84:Al11.5:Cr2.5:Ru2, Vickers hardness 155 Pt85:Al11:Cr2:Ru2, Vickers hardness 155 Pt-Al-Ir, high temperature 2 Pt86:Al10:Ir4, in situ high temperature TEM 69 stable precipitates 69 Pt-Al-Ru, high temperature 2 Pt86:Al10:Ru4, tensile testing 155 Pt-Al-Z, Z = Cr, Ir, Mo, Ni, Re, Ru, Ta, Ti, W 2 Pt-Al-Z, Z = Cr, Ir, Re, Ru, Ta, Ti, isothermal oxidation 2 Pt-Al-Z, Z = Cr, Ir, Ru, Ta, Ti, Pt3Al precipitate, TEM 69 TEM 69

Platinum Alloys, (cont.) Pt86:Al10:Z4, Z = Cr, Ir, Ru, stress-rupture curves 2 Pt86Al10Z4, Z = Cr, Ir, Ru, Ta, Ti, dislocation interactions 69 lattice misfits 69 precipitates 69 Pt-10%Ir, investment casting 21 Pt-Nb-Ru 2 Pt-Ni-Ru, phase diagram 155 Pt-Rh, stress-rupture curve 2 PtRu, colour 189 PtRuGa, fracture strain 189 hardness 189 tensile strength 189 yield strength 189 Pt-Ta-Re 2 Pt-Ta-Ru 2 Pt-Ti-Re 2 Pt-Ti-Ru 2 ternary, mechanical properties 2 oxidation 2 Platinum Complexes, in a chloride matrix, solvent extraction, using Amberlite LA-2 100 [(COD)PtCl2] + LiN(SiMe3)2, a 52 [COD]PtClN(SiMe3)2, for PXP Pt pincer complexes, a 52 dye sensitised solar cells 216 Pt(II), OLEDs 45 square-planar, OLEDs 45 photochemistry 45 photophysics 45 Pt(IV), in HCl 100 Pt(II) chloro, solvent extraction, tren polyamines 100 2– [PtCl6] , solvent extraction, using tripodal amido and urea group-based anion-binding ligands 100 Pt–DNA adducts, a 227 Pt(dpb)Cl, luminescence colour change, grinding, a 106 Pt(5dpb)Cl, luminescence colour change, grinding, a 106 [Pt(dpma)Cl]+, substitution reaction with thioacetate, a 176 Pt(II) fluorenone-ppy, electrophosphorescence, a 176 Pt(II) fluorinated benzoporphyrins, phosphorescence, a 106 Pt octaethylporphyrin, luminescence, a 51 O2-sensitive, a 51 [2(trenH4)4+·(PdCl4)2–·4Cl–·H2O], isolation 100 Platinum Compounds, antitumour, a 227 cisplatin, anticancer drug 35 platinum salts, chemotherapy agents, for cancer 35 PtC, PtH, PtN, PtO, thermodynamic properties 123 PtCl4, from interaction of Cl2 with Pt(110), a 176 Pt silicide, formation, on Pt-coated Si AFM probes, a 52 Zn2PtO4, nanosized, a 51 ® Platinum Group Metals, analysis, using Analig 40 demand, in autocatalysts, effect of CO2 legislation 179 melting 209 recycling 40 refining 40 Poisson’s Ratio, PdAlRu alloys 189 Precious Metals, conference: analysis, economics, markets, process technologies, recovery, refining, regulations, sampling 40 Propane, steam reforming, a 175


Racemisation, secondary alcohols 203 Recovery, Pd(II), from HCl, in presence of Pt(IV) 100 precious metals, from catalysts, plasma heater reactors 40 from combustible waste, using ‘The Ox’ 40 ® from refinery catalysts, by treatment in PlasmaEnvi 40 Recycling, autocatalysts 40 Pd jewellery alloys 21 Reduction, aryl ketones 203 asymmetric, (Z)-acetamidocinnamic acid methyl ester 203 unfunctionalised alkenes 203 dehydroamino acids 203 enamides 203 α,β-, γ,δ-enoic acids 203 esters 203 imines 203

239

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Reduction, (cont.) itaconates 203 β-keto esters 203 NOx 164 50 with H2, a Refining, JSC Krastsvetmet 40 Refining and Recovery, pgms 100 precious metals 40 Reforming, autothermal, C-based fuels 172 C-based fuels 172 exhaust gas 221 internal, CH4 147 oxidative steam, hydrocarbons 147 pre-, C-based fuels 172 steam, butane, a 175 C-based fuels 172 ethane, a 175 methane, a 175 natural gas, a 175 propane, a 175 Regulations, precious metals 40 Rhodium, arc melting 209 assaying 40 electron beam melting 209 high temperature interface reaction, SiC, TiC, TiN, a 105 melting 209 Rhodium Alloys, Pt-Rh, stress-rupture curve 2 Rhodium Complexes, photophysics 45 [(PNP)Rh(CN)] + EtI, a 52 [(PNP)Rh(CN)] + MeI, a 52 [(PNP)Rh(CN)(CH3)][I], reactions, a 52 Rh(III) bipyridines, photoproperties 45 Rh(III) chloro, solvent extraction, tren polyamines 100 Rh(III) cyclometallates, photoproperties 45 Rh(III) polypyridines, photoproperties 45 Rh(III) terpyridines, photoproperties 45 Rhodium Compounds, RhB1.1, hard, hardness, a 176 Rubber, natural latex, hydrogenation, a 105 Russia, new autocatalyst production facility 98 Ruthenium, bottom electrodes, in DRAM capacitors, a 106 chemical mechanical planarisation slurry, a 106 higher-order elastic constants 91 sound velocity 91 ultrasonic attenuation coefficients 91 ultrasonic velocity 91 Ruthenium Alloys, with Ir and Re 138 with Pd, see Palladium Alloys with Pt, see Platinum Alloys Ruthenium Complexes, ‘artificial photosynthesis’ 45 black dye, dye sensitised solar cells 216 CYC-B1, with an alkyl bithiophene group, solar cells, a 52 dendrimeric 45 dye sensitised solar cells 45, 216 K20 dye, dye sensitised solar cells 216 modified dyes, dye sensitised solar cells 216 multinuclear 45 N3 dye, dye sensitised solar cells 216 N719 dye, dye sensitised solar cells 216 photocatalysis 45 photogeneration, of H2 45 polymeric 45 Ru(III) chloro, solvent extraction, tren polyamines 100 Ru(II) polypyridines, basic properties 45 supramolecular assemblies 45 Ruthenium Compounds, RuO2·2H2O, RuO4, in Ru chemical mechanical planarisation, a 106

Sensors, (cont.) supported pgms, by flame synthesis 11 combustible gases 40 147 H2 O 2, a 51 Single Crystals, iridium 138 Solar Cells, dye sensitised, Ir complexes 52, 216 Pt complexes 216 Ru complexes 45, 52, 216 Solvent Extraction, Pd, using hydroxyoxime LIX 84I 100 using malonamide DMDOHEMA 100 Pd(II), pyridine carboxamide and phosphonium ionic liquid systems 100 copolymers of N-isopropylacrylamide and thioethers 100 Pd(II) chloro, using tren polyamines 100 Pt, in a chloride matrix, using Amberlite LA-2 100 2– [PtCl6] , using tripodal amido and urea group-based anion-binding ligands 100 Pt(II) chloro, using tren polyamines 100 Rh(III) chloro, using tren polyamines 100 Ru(III) chloro, using tren polyamines 100 Sonogashira Couplings, palladacycle catalysts 67 Soot, removal, a 50 Sound Velocity, Os 91 Ru 91 Specific Heat Capacity, PtC, PtH, PtN, PtO 123 Sputtering, barrel, Pt thin films, on SiO2 particles, a 52 reactive, of PdO, on Pt, a 105 Stress-Rupture, Pt 2 Pt86:Al10:Z4, Z = Cr, Ir, Ru 2 Pt-Rh 2 ZGS Pt 2 Sulfur, effect of, on diesel oxidation catalysts, a 105 removal, from lean NOx trap 164 Sulfuric Acid, production 40 Surface Coatings, a 52 Suzuki Couplings, palladacycle catalysts 67 sterically bulky aryl bromides 183 Syngas, production 11

Scavenger, Pd-promoted zeolite, of ethylene Selective Catalytic Reduction, catalysts CO hydrocarbons NH3 NOx Sensors, bio-, glucose, a catalytic, precious metals


112 37 164 164 164 27, 179 227 40

Tamiflu®, synthesis, a 226 Thermochemistry, Pd-In, a 51 Pd-Sn, a 51 Pd-Zn, a 51 Thermodynamic Properties, PtC, PtH, PtN, PtO 123 Thin Films, Pt, on SiO2 particles, by barrel sputtering, a 52 Three-Way Catalysts 11, 27 Ultimate Tensile Strength, PdAlRu alloys Ultrasonic Attenuation Coefficients, Os Ru Ultrasonic Velocity, Os Ru

189 91 91 91 91

Vinyl Selenides, cyclic, synthesis, a Vinyl Sulfides, cyclic, synthesis, a α-Vinylation, carbonyl compounds esters ketones

105 105 183 183 183

Watchmaking, Pd alloys Water, remediation, hydrodechlorination, a solvent, a

189 105 175, 176, 226

XPS, catalyst layer, PEM fuel cells, a surface characterisation, heterogeneous catalysts Pt-Au fuel cell catalyst qualification of elements Yield Strength, Pd alloys PtRuGa Young’s Modulus, PdAlRu alloys

175 55, 109 55, 109 109 189 189 189

240

EDITORIAL TEAM Editor David Jollie Assistant Editor Sara Coles Editorial Assistant Margery Ryan Senior Information Scientist Keith White E-mail: [email protected] Platinum Metals Review is the quarterly E-journal supporting research on the science and technology of the platinum group metals and developments in their application in industry http://www.platinummetalsreview.com/

Platinum Metals Review Johnson Matthey Plc, Precious Metals Marketing, Orchard Road, Royston, Hertfordshire SG8 5HE, U.K. E-mail: [email protected] http://www.platinummetalsreview.com/