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Metal Triflates as Precursor Compounds

Master’s Thesis Department of Chemistry Ludwig-Maximilians-Universität München

Cornelia Ritter

Metal Triflates as Precursor Compounds

Masterarbeit aus dem Fachgebiet Anorganische Chemie

von Cornelia Ursula Ritter Bachelor of Science

geboren am 13.11.1986 in München

für die Masterprüfung in Chemie an der Ludwig-Maximilians-Universität München

Datum der mündlichen Prüfung Beginn der Masterarbeit Masterarbeit beim Prüfungsausschuss eingereicht am

21.10.2011 09.01.2012 05.07.2012 II

Erklärung

Ich versichere, dass ich die vorgelegte Masterarbeit am Lehrstuhl für Bioanorganische Chemie und Koordinationschemie des Departments Chemie der Ludwig-Maximilians-Universität München unter der Anregung und Anleitung von Herrn Prof. Dr. Peter Klüfers selbstständig durchgeführt und keine anderen als die angegebenen Hilfsmittel und Quellen benutzt habe.

München, 05.07.2012

_____________________ Cornelia Ritter

Erstgutachter:

Prof. Dr. Peter Klüfers

Zweitgutachterin:

Prof. Dr. Sonja Herres-Pawlis III

Contents

Contents Contents ................................................................................................................ IV Index of Figures..................................................................................................... VII Index of Tables ..................................................................................................... VIII Acronyms ............................................................................................................... IX 1 Introduction ........................................................................................................ 1 1.1 Weakly Coordinating Ligands ......................................................................................... 1 1.2 Square-Planar Geometry in Coordination Compounds ................................................. 2 1.2.1 Square-Planar High Spin Iron(II) Compounds......................................................... 3 1.3 Nitrosyl Coordination Compounds ................................................................................. 4

2 Objective ............................................................................................................ 5 3 Results and Discussion ........................................................................................ 6 3.1 Experimental................................................................................................................... 6 3.1.1 Metal Triflates ........................................................................................................ 6 3.1.1.1 Iron(II) Triflate ................................................................................................ 6 3.1.1.2 Nickel(II) Triflate............................................................................................. 8 3.1.1.3 Cobalt(II) Triflate ............................................................................................ 9 3.1.2 Iron(II) Bis(diolato) Compounds ............................................................................. 9 3.1.2.1 Reaction of Iron(II) Triflate with Anhydroerythritol ...................................... 9 3.1.2.2 Reaction of Iron(II) Triflate with Perfluoropinacol ...................................... 10 3.1.2.3 Reaction of Iron(II) Triflate with other Diols and Sugars ............................. 11 3.1.3 Nickel(II) Bis(diolato) Compounds ........................................................................ 12 3.1.4 Cobalt(II) Bis(diolato) Compounds ....................................................................... 12 3.1.4.1 Reaction of Cobalt(II) Triflate with Anhydroerythritol ................................ 12 3.1.4.2 Reaction of Cobalt(II) Triflate with Perfluoropinacol................................... 13 3.1.5 Pentaqua Nitrosyl Iron(II) Triflate ........................................................................ 13 3.1.6 Pentaqua Nitrosyl Iron(II) Pentahalogenido Nitrosyl Ruthenates ....................... 14 3.1.6.1 Pentaqua Nitrosyl Iron(II) Pentachlorido Nitrosyl Ruthenate ..................... 15 3.1.6.2 Pentaqua Nitrosyl Iron(II) Pentafluorido Nitrosyl Ruthenate ...................... 15 3.2 Quantum Chemical Calculations .................................................................................. 17 IV

Contents 3.3 Concluding Remarks ..................................................................................................... 19 3.3.1 Choosing Suitable WCAs....................................................................................... 19 3.3.2 Solubility of the “Brown Ring” Complex............................................................... 20 3.3.3 Prediction of Solid State Structural Characteristics ............................................. 21

4 Summary and Future Prospects ......................................................................... 22 4.1 Metal triflates ............................................................................................................... 22 4.2 Square Planar Iron(II) Compounds ............................................................................... 22 4.3 “Brown Ring” Complex ................................................................................................. 22 4.4 Theoretical investigations ............................................................................................ 23

5 Experimental Section ........................................................................................ 24 5.1 General Procedures ...................................................................................................... 24 5.2 Equipment and Analysis Methods ................................................................................ 24 5.2.1 X-Ray Diffraction ................................................................................................... 24 5.2.2 Mass Spectrometry .............................................................................................. 26 5.2.3 Quantum Chemical Calculations .......................................................................... 26 5.2.4 Graph-Set Analysis................................................................................................ 28 5.3 Reagents and Solvents.................................................................................................. 28 5.4 Syntheses of Metal Triflates ......................................................................................... 29 5.4.1 Iron(II) Triflate from Water .................................................................................. 29 5.4.2 Iron(II) Triflate from Methanol ............................................................................. 30 5.4.3 Nickel(II) Triflate from Methanol ......................................................................... 31 5.4.4 Cobalt(II) Triflate from Methanol ......................................................................... 32 5.5 Syntheses of Bis(diolato) Compounds .......................................................................... 33 5.5.1 General Procedure for Iron(II) Bis(diolato) Compounds ...................................... 33 5.5.2 General Procedure for Nickel(II) Bis(diolato) Compounds ................................... 34 5.5.3 General Procedure for Cobalt(II) Bis(diolato) Compounds .................................. 34 5.6 Attempted Syntheses of Iron(II) Nitrosyl Compounds ................................................. 35 5.6.1 Pentaqua Nitrosyl Iron(II) Triflate ........................................................................ 35 5.6.2 Pentaqua Nitrosyl Iron(II) Pentachlorido Nitrosyl Ruthenate .............................. 36 5.6.3 Pentaqua Nitrosyl Iron(II) Pentafluorido Nitrosyl Ruthenate .............................. 36 5.7 Synthesis of Lithium Methanolate ............................................................................... 36 V

Contents

6 Appendix .......................................................................................................... 38 6.1 Reference...................................................................................................................... 38 6.2 Crystallographic Data ................................................................................................... 47 6.2.1 Iron(II) Triflate prepared from Methanol ............................................................. 47 6.3 Additional Information ................................................................................................. 49 6.3.1 Hydrogen Bonds in Hexaqua Complexes of Divalent Metals ............................... 49 6.3.2 Jahn-Teller Distortion in [Fe(H2O)6]2+-Ions ........................................................... 50

VI

Indexes

Index of Figures Figure 1-1: Examples of widely-used weakly coordinating anions (E = P, As, Sb, Si). ............. 1 Figure 1-2: a) The splitting of the metal d orbitals in a square-planar (left) and a tetrahedral field (right) in a [MIIF4]2− dianion;[5] b) Potential energy curves for the conversion of an [FeMe4]2− tetrahedron into a square in three different spin states.[6] ................................................................................................................. 2 Figure 1-3: Crystal structures of the two published square-planar FeII anions. ..................... 3 Figure 1-4: Reaction scheme of the synthesis of an iron(II) bis(diolato) compound. ............. 3 Figure 3-1: Mercury presentation of Fe(OTf)2 · 4 MeOH ........................................................ 7 Figure 3-2: Mercury presentation of contacts and packing in Fe(OTf)2 · 4 MeOH. ................ 8 Figure 3-3: The gradual red-to-blue colour shift of FeIIO4 chromophores on increasing distortion from planarity in terms of λmax over δ.[5]............................................ 10 Figure 3-4: Reagents tested for the formation of iron(II) bis(diolato) compounds. ............. 11 Figure 3-5: IR-Spectra of [Fe(H2O)5NO](OTf)2 in water (blue) and methanol (green). ......... 14 Figure 3-6: Pie chart of the H-bond/H ratio in the examined hexaqua compounds. ........... 14 Figure 3-7: IR-Spectrum of [Fe(H2O)5NO] [RuF5NO] in water. .............................................. 16 Figure 3-8: Origin plot of the two anion coordination scales, aTM against ν(NH) ................ 20 Figure 6-1: SCHAKAL packing diagram of iron(II) triflate prepared from methanol. ............ 47

VII

Indexes

Index of Tables Table 3-1: Distances [Å] and angles [°] of hydrogen bonds and weak contacts in Fe(OTf) 2 · 4 MeOH. ..................................................................................................................... 7 Table 3-2: Theoretical literature values for the geometry of Fe(H2O)5NO]2+. ....................... 17 Table 3-3: Comparison of calculations for the geometry of Fe(H2O)5NO]2+, averaged theoretical literature values against different methods. ................................................. 17 Table 3-4: Comparison of calculated ν(NO) stretching vibrations with experimental results . .............................................................................................................................. 18 Table 3-5: Coordinating ability of selected anions by their ∆ν(NH)[24] and aTM values .......... 19 Table 5-1: List of Chemicals. ................................................................................................... 28 Table 5-2: Overview of experiments regarding iron(II) bis(diolato) compounds. ................. 33 Table 5-3: Overview of experiments regarding nickel(II) bis(diolato) compounds................ 34 Table 5-4: Overview of experiments regarding cobalt(II) bis(diolato) compounds. .............. 35 Table 5-5: Overview of crystallisation experiments for pentaqua nitrosyl iron(II) triflate. ... 35 Table 6-1: Crystallographic table of iron(II) triflate prepared from methanol. ..................... 48 Table 6-2: Hydrogen bonds in hexaqua complexes of divalent metals as found in the literature. ............................................................................................................... 49 Table 6-3: Jahn-Teller distortion in hexaqua-iron(II) compounds as found in the literature, including differences in Fe-O bond length.. .......................................................... 50

VIII

Acronyms

Acronyms Abbreviation AnEryt AR c ca. Chxd eq Et ERI Fru Glyc h IR LFSE LR Me min MW NMR PfPin Pin Rib RT sln. THF WCA WCL

Subject 1,4-anhydroerythritol reagent grade concentration circa 1,2-cyclohexanediol equivalent(s) ethyl electron repulsion integrals fructose glycerol hour(s) infrared Ligand Field Stabilisation Energy laboratory grade methyl minutes molecular weight nuclear magnetic resonance perfluoropinacol pinacol ribose room temperature solution tetrahydrofuran weakly coordinating anion weakly coordinating ligand

IX

Introduction

Weakly Coordinating Ligands

1 Introduction

Coordination compounds have been subject to research ever since Alfred Werner successfully explained the composition and structure of several ammonium metal chlorides at the end of the 19th century.[1] He was the first to propose an octahedral environment for certain metal cations and to discriminate between different bonding modes, depending on the number of available ligands. Innumerable synthetic and natural substances have since been characterised, while the underlying principles of formation and geometry were studied. Metal complexes play important roles in nature (enzymes), medicine (drugs, diagnostics) and synthesis (catalysts), rendering fine-tuned synthesis and modification routes an important task.

1.1 Weakly Coordinating Ligands

Especially less stable compounds need a careful composition of reaction conditions, where the metal core is easily accessible and competing ligands are reduced to a minimum. The solvent choice, as well as the use of weakly coordinating ligands (WCLs) and anions (WCAs), are thus important factors for a successful synthesis. Some well-established examples for WCAs are shown in Figure 1-1.

F

F OS2+ OF Otriflate

O-O Cl3+ OOperchlorate

F F B- F F

Ph Ph B- Ph

tetrafluoroborate

tetraphenylborate

Ph

-

F

-F

Fn+

E

F-

FF-

hexafluoroanions

Figure 1-1: Examples of widely-used weakly coordinating anions (E = P, As, Sb, Si).

Non-coordinating anions were already regarded as a myth in the early seventies, at least by some scientists, such as Michael Rosenthal.[2] It was by Steven Strauss[3] who established the term “weakly coordinating anions” in 1993, which is still the most common way of referring to the matter. Ingo Krossing and Ines Raabe[4,5] later reviewed the ongoing progress in research and knowledge. They ultimately came to the conclusion that to reach noncoordination, the most suitable anion would have to be determined depending on the system of interest. 1

Introduction

Square-Planar Geometry in Coordination Compounds

1.2 Square-Planar Geometry in Coordination Compounds

Predicting the geometry of coordination compounds and tailoring them to a desired shape is an important ability for the directed synthesis of catalysts or new medical agents. The consideration of molecular orbitals and electronic influences helps in understanding the tendencies, but due to different possible spin or oxidation states, geometry is often difficult to predict. a)

b)

Figure 1-2: a) The splitting of the metal d orbitals in a square-planar (left) and a tetrahedral field (right) in an [MIIF4]2− dianion;[6,7] b) Potential energy curves for the conversion of an [FeMe4]2− tetrahedron into a square in three different spin states.[8]

An iron(II) d6 case (cf. Figure 1-2), for example, will usually not exists in its energetically unfavourable singlet spin state. Depending on the ligand strength, orbital splitting can be large enough to at least allow for triplet spin (S = 1), leaving the x2−y2 orbital empty and forcing the compound towards square-planar geometry. Nonetheless, the intermediate- and high-spin states are energetically very similar at the square-planar side of the plot, which is the reason for the recently published results described in the following chapter.

2

Introduction

Square-Planar Geometry in Coordination Compounds

1.2.1 Square-Planar High Spin Iron(II) Compounds

Xaver Wurzenberger et al. recently showed the first square-planar high-spin FeIIO4 centre in a molecular entity, by employing a bis(bidentate) diolato environment in a coordination compound (cf. Figure 1-3).[6,7] Stefanie a Cantalupo et al. were able to prepare a second compound, using perfluoropinacolate (PfPin) as diolato ligand.[9,10] Their conditions involved working in strongly alkaline solutions with a high excess of Anhydroerythritol, or an excess of a strong non-nucleophilic base in aprotic solvents for the pfp complex.

Figure 1-3: Crystal structures of the two published square-planar FeII anions. Left: [Fe(AnErytH-2)2]2(ellipsoids set at 60% probability)[6,7]; right: [Fe(PfPinH-2)2]2- (ellipsoids set at 50% probability).[9,10]

To permit a transfer to more sensitive systems like saccharide derivatives, a milder synthesis path is desirable. Sandra Albrecht[11] was able to improve these conditions and obtain the desired product in methanolic solutions by exchanging the iron precursor from iron(II) chloride to iron(II) perchlorate. The molar ratio metal:diol:base thus equaled 1:2:8 (instead of 1:12:24 in aqueous solution).

HO Fe2+

R

+ 2 HO

R

-

4 OMe MeOH, RT

R

2O

O

R

Fe R

O

O

R

Figure 1-4: Reaction scheme of the synthesis of an iron(II) bis(diolato) compound.

3

Introduction

Nitrosyl Coordination Compounds

1.3 Nitrosyl Coordination Compounds

Nitrosyl compounds are an interesting research topic, not only for their possible application in medicine, where NO donors are of use for the most various implications, including relaxation of vascular smooth muscle, the inhibition of platelet aggregation, immunoregulation or neurotransmission.[12] Among the applied drugs, a noteworthy number fall into the category of coordination compounds. But even though many nitrosyl complexes are known and characterised, it is still not a trivial task to understand their electronic structure. Enemark and Feltham developed an elegant notation, freeing researchers from the task of denoting oxidation states by giving a combined electron count for the NO-metal fragment:[13] {M(NO)x}n

(1)

where x is the number of NO molecules bound to the metal, and n is the sum of metal-d and NO-π* electrons. Some long-known systems have eluded the final determination of their electronic states to date. One of the best known ones is the “brown ring” reaction. It has been used in qualitative analysis for generations, detecting nitrate by adding a solution of iron(II) and underlaying it with concentrated sulphuric acid, so the following reaction can take place at the phase interface:[14] 3 Fe2+ + NO3− + 4 H+

→

3 Fe3+ + NO + 2 H2O

(2)

[Fe(H2O)6]2+ + NO

→

[Fe(H2O)5NO]2+ + H2O

(3)

The chromophore species is still a matter of discussion. The most recent theoretical publication by Radoń et al. calculated an intermediate oxidation state between FeII or FeIII closer to the lower one (CASSCF/CASPT2 level of theory).[15] Being able to examine this elusive compound in a solid could give a deeper basic understanding, while testing the quality of borderline theoretical predictions.

4

Objective

Nitrosyl Coordination Compounds

2 Objective

The perchlorate anion and various borate anions had already been tested as WCAs in this research group, so that now triflate—prepared from aqueous or methanolic solutions—will be used as a precursor in direct comparison. It will be investigated whether it can improve issues regarding both old and new problem sets, focusing on iron(II) cores: the “brown ring” reaction on one side (cf. Equation 1 and 2), and square planar bis(diolato) compounds on the other (cf. reaction shown in Figure 1-4). In the case of the former, the ultimate goal is crystallisation, but additional insights into the complex species dynamics would also be of advantage. For the latter, the achievement of stable compounds while working with stoichiometric ratios, especially regarding the base content of solutions, would be a welcome improvement, so that the field could be expanded to other diols and saccharides. If possible, further metal(II) triflates will likewise be examined as precursors. Theoretical investigations are a useful and, nowadays, widespread means of predicting, analyzing and explaining experimental data. Thus, calculations using the Turbomole suite[16] will be carried out and studied alongside of empirical results, especially regarding iron(II) nitrosyl compounds.

5

Results and Discussion

Experimental

3 Results and Discussion 3.1 Experimental

Synthesised substances were characterised—if possible—using IR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction. Unfortunately, analysis often proved difficult due to the instability of the compounds. Their paramagnetic nature prohibited the use of NMR spectroscopy.

3.1.1 Metal Triflates The first part of this thesis deals with the synthesis and characterisation of divalent metal triflates from methanolic triflic acid. For iron, only the hexahydrate and a tetra-acetonitrile compound had been structurally characterised[17], while for nickel and cobalt no crystal structures of the triflates existed at all. The synthesis from methanol lead to a product free of water, which could be extremely important if further steps include sensitive issues, where water is to be excluded.

3.1.1.1 Iron(II) Triflate This precursor compound was synthesised from iron powder and triflic acid in water or methanol, as vaguely described in the literature.[17] Reducing the solvent and cooling the solution at 5 °C afforded light green-blue crystals of plate-like shape. Drying in vacuo resulted in the loss of 4 – 5 eq of solvent in case of water and 2 eq in case of methanol, and yielded a greenish-white powder. Prepared from methanol, iron(II) triflate and four solvent molecules crystallised in the triclinic space group P — 1, with the unit cell containing one molecular unit of Ci-symmetry (cf. Figure 3-1). Iron(II) had a slightly distorted octahedral environment, consisting of two triflate ions in axial positions which coordinated via one sulfonate oxygen atom, and four methanol molecules in the equatorial plane.

6


Experimental

Figure 3-1: Mercury presentation of Fe(OTf)2 · 4 MeOH. Ellipsoids are drawn at 50 % probability level. Distances [Å] and angles [°]: Fe-O2 2.1016(2), Fe-O3 2.0898(3), Fe-O4 2.1413(2); O2-Fe-O3 93.46, O2Fe-O4 89.48, O3-Fe-O4 87.68.

Contacts between moieties are illustrated in Figure 3-2 and listed in Table 6-2. Two hydrogen bonds were formed between the polar methanol hydrogen atoms and the two noncoordinating sulfonate oxygen atoms, bridging the units in a chain-like manner along the a axis. The unary graph-set descriptor N1 for this pattern is given as C11(6) R22(12). Perpendicular to the chains, weak contacts of the type C-H···O aligned methyl and sulfonate groups, resulting in layers parallel to the ab plane which are bordered by trifluoromethyl groups.

Table 3-1: Distances [Å] and angles [°] of hydrogen bonds and weak contacts in Fe(OTf)2 · 4 MeOH. For atom numbering see Figure 3-1. D: donor, A: acceptor, x: difference of (H···A) and the sum of the van-der-Waals radii.[18] D O2 O3 C3

H H82 H83 H31

A O1 O5 O1

D···A 2.730(3) 2.741(3) 3.303(3)

D-H 0.77(4) 0.73(4) 0.98(4)

H···A 1.96(4) 2.02(4) 2.71(4)

x ∡D-H···A −0.76 178(4) −0.70 170(4) −0.01 120(4)

7


Experimental

_________________________________________________

Figure 3-2: Mercury presentation of contacts and packing in Fe(OTf)2 · 4 MeOH. Top: view along the b axis, including hydrogen bonds (turquoise dashed lines) between moieties forming chains along the a axis. Below: view along the chains (a axis), including C-H···O contacts (turquoise dashed lines).

3.1.1.2 Nickel(II) Triflate Nickel(II) triflate was prepared similarly to the corresponding iron compound, since no water-free synthesis route was described in the literature. A higher concentration and elevated temperature were used, to allow for the triflic acid to oxidise the metal and to speed up the reaction. From a dark green solution, delicate deep green crystals formed upon cooling. They were unstable in air and under paraffinic oil, making the collection of crystallographic data impossible. When dried in vacuo, the substance lost approximately two of its solvent molecules and the appearance changed to a greenish-white powder.

8


Experimental

3.1.1.3 Cobalt(II) Triflate Cobalt(II) triflate was prepared by Christine Neumann[19] accordingly to the corresponding iron compound, since no water free synthesis routes were described in the literature. An elevated temperature was used to speed up the reaction. From a purple solution, delicate pink crystals formed upon cooling, which again were not suitable for X-ray diffraction measurements. When dried in vacuo, the substance lost all but two of its solvent molecules and the appearance changed to a pinkish white powder.

3.1.2 Iron(II) Bis(diolato) Compounds With iron(II) triflate available in three different states of hydration—dry, monohydrate and hexahydrate—studies could be conducted on the influence of water on the formation on bis(diolato) complexes. Mass spectrometry and IR spectroscopy were not conducted on these compounds, since they are extremely unstable in air.

3.1.2.1 Reaction of Iron(II) Triflate with Anhydroerythritol The reaction of iron(II) triflate and anhydroerythritol in methanol was initiated by the addition of lithium methanolate, leading to a colour change from light yellow to deep purple. The stabilities of the resulting solutions vary: When prepared from the hexahydrate, the product completely decomposed within 16 h, leaving a yellow solution over a fine light-grey precipitate, which darkened over a few days to near black. The monohydrate led to a more stable solution, slowly forming the same precipitate but, instead of going back to yellow, the supernatant liquid slowly pales to light violet over the course of a few days. Reducing the overall concentration did not change most of this observation, but yielded a rather grey than violet solution. The best results were obtained by preparation via Fe(OTf)2 · 2 MeOH, which formed the same precipitate, but retained the colour of the supernate. Passing the solution through a syringe filter removed the precipitate. After some days precipitation started again and the liquor slowly turned grey.

9


Experimental

3.1.2.2 Reaction of Iron(II) Triflate with Perfluoropinacol The reaction of iron(II) triflate and perfluoropinacol in methanol was initiated by the addition of lithium methanolate, leading to a colour change from light yellow to deep blue. Since [K(DME)2]2 [Fe(PfPinH-2)2] is described as a purple compound in the literature [10], the identity of the blue species had to be determined. The deviating colour might merely be due to solvent influence (solvatochromism), but the possible coordination of the triflate anions could not be excluded without a crystal structure. Another possible reason that had to be taken into account is a known characteristic of the FeO4-chromophore: it shows conformation-dependent colour shift (cf. Figure 3-3).[6,7] gillespite (ca. 26 kbar, blue) sln. vs. DFT Li2[Fe(AnErytH-2)2] · 9 H2O gillespite (red) Li2[Fe(AnErytH-2)2] · 4 H2O

Figure 3-3: The gradual red-to-blue colour shift of FeIIO4 chromophores on increasing distortion from planarity in terms of λmax over δ.[6,7]

Square-planar [FeII(PfPinH-2)2]2- was reported to show a UV/vis signal in solution (THF) at 553 nm[9,10], while the signal for [FeII(AnErytH-2)2]2- appeared at 564 nm in water.[6,7] Given that the changed electronic structure did not seem to have a major impact on this transition, one could assume that the blue species was considerably distorted towards tetrahedral geometry. Regarding the stability and formation of the complex, various influences were studied: Even very low base concentrations (metal:PfPin:methanolate 1:2:2) sufficed for the formation of the complex, but stoichiometric addition (1:2:4) prevented precipitation and was necessary for stable solutions. Water content was another important factor: preparation from the monohydrate led to an immediate formation of small amounts of a fine white precipitate, which darkened over the course of approx. 16 h. When 6 eq of water were added to the methanolate solution before

10


Experimental

combining it with the reaction mixture, a slow precipitation of a dark solid was observed, with the supernatant liquid still bright blue and stable for weeks. Astonishing stability could be observed when Fe(OTf)2 · 2 MeOH was used as the precursor – the resulting solution did not show any signs of precipitation or deterioration over weeks. Attempts to promote crystallisation by cooling were unsuccessful, and the diffusion of isopropanol led to decomposition of the complex, indicated by a colour change to light yellow. To eliminate decomposition due to dilution, a different approach was tested: potassium hydroxide was used to bind methanol, thus reducing the solvent and increasing the concentration of the solution. Until the submission of this thesis, crystallisation had not been successful.

3.1.2.3 Reaction of Iron(II) Triflate with other Diols and Sugars Since it was possible to produce fairly stable solutions with anhydroerythritol and especially perfluoropinacol at stoichiometric base addition, the next step was the transfer of the method to sugars and other diols. The following reagents were tested for their ability to form similar bis(diolato) complexes with iron(II) triflate: F3C CF3 F3C CF3 HO OH perfluoropinacol HO HO

OH

pinacol

O OH HO

HO glycerol

OH OH

HO OH fructose

O HO OH anhydroerythritol HO

O

OH

HO OH ribose

HO

OH HO OH cistrans1,2-cyclohexanediol

Figure 3-4: Reagents tested for the formation of iron(II) bis(diolato) compounds.

Fructose and ribose are monosaccharides, which in their furanose form show similar structural features to anhydroerythritol, regardless of α or β configuration at the anomeric centre; trans- and cis-cyclohexanediol were used to determine the influence of the bite angle; the behaviour of pinacol was meant to give insights into electronic effects when compared to perfluoropinacol, and glycerol was tested as a ligand for the preparation of derived polynuclear complexes. 11


Experimental

Unfortunately, none of them showed signs of the permanent formation of the desired intensely coloured complex when treated according to the procedure established for anhydroerythritol and perfluoropinacol. Pinacol, glycerol and both of the cyclohexanediols formed flaky precipitates of greenishwhite colour immediately upon base addition. Fructose stayed in solution, but the desired colour change to a blue hue did not occur. Instead, the liquor turned a darker shade of yellow, then darkened to greenish black over the course of 4 h. Promising behaviour was seen only in ribose, where a colour change to purple was observed after addition of the first drops to the lithium methanolate solution. Upon further addition, however, the colour faded to grey, and darkened to greyish black over the course of 4 h. Varying the base content of the resulting solution might be able to change these results and stabilise the desired bis(diolato) compound.

3.1.3 Nickel(II) Bis(diolato) Compounds Using the same procedure as for the corresponding iron compounds, no formation of the expected brightly coloured compounds was observed. In the case of anhydroerythritol and perfluoropinacol, the formerly bright-green solutions turned yellow-brown and greenishblack, respectively, upon addition of base. Neither precipitation nor crystallisation occurred. Ribose and fructose, on the other hand, showed the immediate formation of a voluminous bright-grey precipitate.

3.1.4 Cobalt(II) Bis(diolato) Compounds Experiments discussed in this chapter were conducted by Cristine Neumann.[19]

3.1.4.1 Reaction of Cobalt(II) Triflate with Anhydroerythritol After the addition of the first few millilitres of metal/diol solution to the base, a deep blue solution resulted in all cases. Upon addition of the remaining amount, colour change to pinkish-purple took place. Unlike perchlorate reactions, where the dilute conditions led to stable 12


Experimental

solutions, all triflate tests started precipitation at some point, resulting in a voluminous, fine, solid and a nearly colourless, clear solution. In the case of lithium methanolate, the solid was of a purple/pink colour, with sodium methanolate more of a dirty purple/blue/grey. Both were insoluble precipitates, only dilute acid could dissolve them. Sometimes, but not repeatably, a colour change to green occurred after varying spans of time. To investigate this issue, the reaction was once conducted without using an inert gas atmosphere, the procedure otherwise unchanged. When the metal/diol solution was combined with the base, first the familiar colour change to blue occurred, before the solution turned to a rich, deep green, without showing signs of a purple species. Possible oxidation might, therefore, be the reason for the sudden colour changes.

3.1.4.2 Reaction of Cobalt(II) Triflate with Perfluoropinacol Reactions of cobalt(II) triflate with perfluoropinacol, following the same procedure, showed a lighter pink in the metal/diol solutions before tha addition of base. After the combination of the reagents, the colour intensified over the course of approx. 1 min to a deep magenta shade. Solutions were stable with both lithium methanolate and sodium methanolate as base. The complete evaporation of solvent yielded a light-purple powder, but crystallisation attempts had not been successful at the time of submission.

3.1.5 Pentaqua Nitrosyl Iron(II) Triflate Preparation of [Fe(H2O)5NO]2+ was accomplished by dissolving the hydrated triflate and passing nitric oxide over it while stirring. A colour change from light blue to dark brown occurred immediately, indicating the successful transformation. Resulting solutions were stable for months when stored under NO atmosphere, but numerous attempts to induce crystallisation—by varying the solvent or allowing a second, less polar one (precipitant) to diffuse into the solution—proved unsuccessful. After several months, IR ATR measurements were conducted on samples of the solution in water and methanol (cf. Figure 3-5). Both showed a distinct signal in the NO stretching vibration range at 1824 cm-1 and 1815 cm-1, respectively.

13


Experimental

The solutions showed a surprisingly slow decomposition when exposed to air, bleaching from dark brown to rusty orange over the course of several hours. This may have been an indicator for the formation of a different species, perhaps containing coordinated triflate. 100

90

80

70

%T 60

50

in water in methanol

40

30 4000

3500

3000

2500

2000

1500

1000

-1

wavenumber [cm ]

Figure 3-5: IR-Spectra of [Fe(H2O)5NO](OTf)2 in water (blue) and methanol (green).

3.1.6 Pentaqua Nitrosyl Iron(II) Pentahalogenido Nitrosyl Ruthenates A literature search for the closely related hexaqua complexes of divalent metals of the type [1M(H2O)6] [2MX6] (and similar anions) revealed the widespread existence of hydrogen acceptors in these structures. Details can be found in Table 6-2 in the additional information (Chapter 6.3.1, page 49). Closer examination showed that in only 6 of the 32 examined compounds the hydrogen bond per hydrogen ratio diverged from 1 (cf. Figure 3-6). 3 2

1

26

H-bond/H = 1 H-bond/H < 1 H-bond/H > 1 unknown

Figure 3-6: Pie chart of the H-bond/H ratio in the examined hexaqua compounds.

14


Experimental

This led to the hypothesis that a matched ratio could help promote crystallisation in the corresponding nitric oxide pentaqua complex. As a counterion which provides a stoichiometric number of hydrogen bond acceptors for the aqua ligands, pentachlorido- and pentafluorido nitrosyl ruthenates were employed.

3.1.6.1 Pentaqua Nitrosyl Iron(II) Pentachlorido Nitrosyl Ruthenate After adding a highly concentrated dark purple solution of pentachlorido nitrosyl ruthenate to the reaction solution, the mixture was kept at room temperature under NO atmosphere for a week without showing any signs of decomposition. The vessel was then stored at 5 °C for two months without any apparent change.

3.1.6.2 Pentaqua Nitrosyl Iron(II) Pentafluorido Nitrosyl Ruthenate Since the chloride compound did not easily lead to the desired formation of crystals, a sample of the fluoride, the synthesis of which is more demanding, was, thankfully, provided by Dominik Schaniel (Institut Jean Barriol, Nancy, France). The sample (140 mg) of dark purple crystals contained a considerable amount of impurities in the form of white to yellow crystals, which were suspected to be potassium hydrogen difluoride KHF2. Given that purification was no adequate measure for such a small amount of substance, it was used as-is, taking into account an estimated purity of 75% (or 1:1 ratio) for the calculation of the reaction partners. The procedure was exactly the same as for the chloride compound. After ca. 3 h, a fine light brown precipitate started forming. After two weeks, no signs of crystallisation were visible. After approx. one month of unchanged appearance, the reaction mixture was dried in vacuo, resulting in an amorphous reddish-brown solid. An IR measurement of the dried mixture is shown in Figure 3-7. The intense signal at 1896 cm-1 could be attributed to the NO stretching vibration of the anion when compared to the literature values of its heavy homologues, which ranged from 1900 to 1840 cm-1.[20] There were no signs of another nitrosyl signal, either from the potentially mono-nitrosylated cation (to be expected around 1820 cm-1) or for a dinitrosylated anion. The brown ring complex was thus

15


Experimental

not stable under the present conditions, and the reddish hue of the solid hinted at the possible oxidation of iron(II) during the drying process. 100 90 80 70 60

%T 50 40

[FeNO(H2O)5][RuF5NO]

30 20 4000

3500

3000

2500

2000

1500

1000

-1

wavenumber [cm ]

Figure 3-7: IR-Spectrum of the reaction mixture containing [RuF5NO]2− in water.

16


Quantum Chemical Calculations

3.2 Quantum Chemical Calculations The Turbomole suite[16] was used for calculations regarding hexaqua iron(II) and the “brown ring” complex. To simulate solvation, the conductor-like screening model (COSMO) was employed, while the use of a resolution of identity (ri) approximation reduced computational cost. In some cases dispersion correction according to Grimme[21] was applied. Multiple methods and functionals were tested, while maintaining the basis set at triple-ξ level (def2TZVP). The main focus lay on the calculation of the pentaqua nitrosyl iron(II) cation. Since an empirically determined crystal structure of the species is still unknown, geometry optimisation results could only be compared to an averaged value of the most recently published available theoretical results on the topic (cf. Table 3-2 and Table 3-3). Table 3-2: Theoretical literature values for the geometry of [Fe(H2O)5NO]2+ (Fe-O distances averaged over the molecule). Source:

[22]

[15,23]

[24]

Averaged Value 181 179.5 Fe-N [pm] 181 178 218.7 Fe-O [pm] 216 220 115 114.5 N-O [pm] 113 115 180 179.8 ∡Fe-N-O [°] 180 179.5 *Methods used (from left to right): DFT/uB3-LYP/6-311+G(d,p); DFT/BP86/def2-TZVP; DFT/OLYP/TZP; DFT/B3LYP/6-311++G(d,p). Table 3-3: Comparison of DFT calculations (def2-TZVP level of theory) for the geometry of [Fe(H2O)5NO]2+, averaged theoretical literature values against different methods. All calculations were performed using ri and COSMO (water). Fe-N Fe-O N-O ∡ Fe-N-O Deviation [%] [pm] [pm] [pm] [°] averaged literature value 179.5 218.7 114.5 179.8 bond angle total disp, B-LYP 176 216 115 178 0.97 1.18 1.02 179 212 114 180 1.26 -0.11 0.92 B3-LYP 171 1.04 4.89 2.00 B-LYP 176 215 115 disp, B-P 174 213 115 169 1.74 6.06 2.82 PBE 174 213 115 169 1.76 6.23 2.88 *only methods leading to converged structures are listed. Method*

Of the tested methods leading to converged structures, the exchange correlation functional B-LYP[25,26], a generalised gradient approximation, seemed to yield the most stable results in combination with dispersion correction, followed by the related three parameter hybrid 17


Quantum Chemical Calculations

functional B3-LYP.[27] Geometry optimisations using more sophisticated methods, such as MP2 or CC2, did not converge. For an absolute evaluation of successful calculations however, it is crucial to have an empirical structure for comparison. Follow-up computation of vibrational frequencies is not yet implemented with COSMO in Turbomole, unless they are calculated numerically (using the

NUMFORCE

command). Just

switching off COSMO yielded imaginary frequencies, even after recalculating the energy in a single point run, and, therefore, did not yield significant results. A comparison of the calculated wavenumbers of the NO stretching vibration with an average of empirically determined values (1815 cm−1, cf. Chapter 3.1.6, page 14) is given in Table 3-4. Table 3-4: Comparison of calculated ν(NO) stretching vibrations with experimental results. All calculations were performed numerically on geometries optimised under the same conditions, using ri and COSMO (water). ν(NO) ν(NO)exp −1 /ν(NO) [cm ] calc* 0.967 DFT + disp, b-lyp 1876 0.928 DFT, b3-lyp 1955 0.974 DFT, b-lyp 1863 0.953 DFT + disp, b-p 1905 0.952 DFT, pbe 1907 *ν(NH)exp averaged from at [Fe(H2O)5NO] (OTf)2 in water (1824 cm−1) and methanol (1815 cm−1), and [Fe(H2O)5NO]SO4 (1810 cm−1).[28] Method

All calculated values differed from the experimental ones, confirming a reason for the tedious but common practice of applying a linear correction factor to vibrational computations, in this case varying between approximately 93–97%. But again, B-LYP (with and without dispersion correction), afforded frequencies closest to the empirical values, and seemed, therefore, to be a good choice for the calculation of related systems.

18


Concluding Remarks

3.3 Concluding Remarks 3.3.1 Choosing Suitable WCAs Various approaches for scaling the coordinating ability of solvents and anions have been published: Christopher Reed et al. developed a reference system, where they used the IR frequency shift of the ν(NH) stretching vibration in tri-n-octylammonium salts of the evaluated anions as an indicator for interactions.[29] This empirical description of basicity, they argued, is closely correlated to the coordinating tendencies of the tested compounds. Rául Díaz-Torres and Santiago Alvarez, on the other hand, evaluated known crystal structures containing several anions and solvents for the presence of coordinative contacts.[30] To allow for second-order (“semi coordinating”) contacts to be included in the study, they not only assigned the percentage of structures containing coordination, but described a coordinating ability index toward transition metals: a TM

log

c s u

(4)

where c, s and u are the numbers of structures with the group coordinated, semi coordinated and uncoordinated, respectively. As an example, Table 3-5 shows both their results for the anions listed in Figure 1-1. It is immediately obvious that both scales did not yield the same ranking. After all, basicity and coordinating ability are related, but not to be used interchangeably. Table 3-5: Coordinating ability of selected anions by their ∆ν(NH)[29] and aTM values, as well as the percentage of structures in which they show coordination (%).[30] Anion

Chem. Formula

∆ν(NH)

aTM

%

Hexafluorosilicate Triflate Perchlorate Hexafluoroarsenate Hexafluorantimonate Tetrafluoroborate Hexafluorophosphate Perfluorotetraphenylborate Tetraphenylborate

SiF62− F3CSO3− ClO4− AsF6− SbF6− BF4PF6− B(C6F5)4− BPh4−

324 214 73 88 130 72 30 -

-0.3 -0.4 -0.6 -0.6 -0.9 -1.1 -1.6 -1.7 -1.8

31 31 19 18 10 8 3 2 2

19


Concluding Remarks

This fact emphasised even more Krossing and Raabe’s findings that the system in question has a non-negligible influence. Depending on the needs, either basicity or coordination can be more important, which will influence the ideal anion choice. Plotting the values of anions appearing in both scales against each other (cf. Figure 3-8) showed a rough correlation (indicated by the linear fit), but exceptions were clearly visible and might be an interesting approach to solving experimental problems. 1.5 −

Cl 1.0 0.5

a

TM

−

NO3

−

−

ReO4

CMeB11F11

0.0

2−

HSO4 -0.5 -1.0

−

AsF6

−

CF3SO3

−

ClO4

− SbF6 −

BF4

-1.5

−

PF6

− B(C6F5)4

-2.0 0

200

400

600

800

1000

-1

(NH) [cm ]

Figure 3-8: Origin plot of the two anion coordination scales, aTM against ν(NH) and linear fit (green).

For the “brown ring”, for example, a good hydrogen-bond acceptor with weak coordinating ability should be expected to be most suitable, making nitrate the best choice of the anions included in the graph. But further examination of different anions, and adding them to the data points, could lead to a considerable improvement of this estimate.

3.3.2 Solubility of the “Brown Ring” Complex Hexaqua nitrosyl iron(II) seemed to be highly soluble in polar solvents, with the cation and anion both solvent-separated. Possibly, the transition towards more apolar solvents lead to an aggregation of anion and cation, since separated charges would not be stabilised enough. This could lead to a ligand exchange of water in favour of the anion, ultimately resulting in

20


Concluding Remarks

tight ion pairs, which, again, might be soluble even in apolar solvents. This hypothesis could account for the fact that the compound eluded all attempts for crystallisation. An indication for this behaviour might be found by conducting a series of IR measurements: a continuous shift of the NO stretching vibration signal in different solvents could mirror a change of the bonding situation at the iron core, and thus be able to distinguish between different species.

3.3.3 Prediction of Solid State Structural Characteristics For a better evaluation of a possible Jahn-Teller (JT) distortion of the hexaqua iron(II) cation, a comparison of literature structures containing both inorganic and organic anions was conducted (Appendix, Chapter 6.3.2, Table 6-3). In most of these structures (78%), a significant JT effect occured. This could be an indication that distortion is to be expected, but can, in special cases, be obliterated by other factors. Bond lengths usually ranged from ca. 2.08–2.18 Å. In single cases, however, bonds were shorter than 2.05 Å, possibly indicating an actually higher oxidation state of the metal (i.e. FeIII). An apparent lengthening above 2.20 Å, on the other side, could be due to an unresolved disorder of the crystal or strong hydrogen bonding towards anions. In the case of [Fe(H2O)4(gly)2][Fe(H2O)6](SO4)2, where the axial Fe-O bond is as long as 2.377 Å, none of these factors was visible that could account for the extreme value. The large divergence present even in the average structure depended on the immediate environment and interactions in the solid structure, and could hardly be accurately calculated without including these factors. Thus, computation of solid-state structures is an important future task, but had not been pursued further in the course of this work.

21

Summary and Future Prospects

Metal triflates

4 Summary and Future Prospects 4.1 Metal triflates

Several metal triflates were successfully synthesised: the iron(II) compound was obtained in three different solvatisation states: as a hexahydrate, monohydrate and the substance containing four equivalents of methanol. The latter was newly characterised by single-crystal X−ray diffraction. The corresponding nickel(II) and cobalt(II) compounds were likewise prepared, but afforded crystals were not suitable for XRD measurements as of yet. They can further be employed as precursors for different problem sets. But in general, suitable anions need to be determined depending on the necessary balance of basicity or coordinating ability.

4.2 Square Planar Iron(II) Compounds

Iron(II) compounds of anhydroerythritol and perfluoropinacol were prepared in stoichiometrically composed solutions. In all cases the presence of water reduced the stability of the formed complexes, rendering the use of dried solvents necessary. The resulting perfluoropinacol-species was stable for weeks, but appeared blue instead of purple (as described in the literature). Until now, only assumptions for the underlying reasons had been possible, the most likely one a distortion from square-planar geometry towards a tetrahedron. A transfer of the synthesis to other diols and saccharides has not yet been successful. Most of the reactions showed immediate precipitation. Varying solvents, base types and concentrations are possible approaches for further investigations.

4.3 “Brown Ring” Complex

The compound was stable in solutions for months under NO atmosphere, using either triflate or pentahalogenido nitrosyl ruthenates as anions, but all crystallisation attempts were unsuccessful.

22

Summary and Future Prospects

Theoretical investigations

IR-ATR measurements in water and methanol showed a distinct signal in the NO stretching vibration range at 1824 cm-1 and 1815 cm-1, respectively. The solutions showed a surprisingly slow decomposition when exposed to air, possibly due to the formation of a different species containing coordinated triflate. Further investigations are necessary, possibly using the IR stretching vibration signal as an indicator. But if this proves true, different anions with less coordinating ability and high hydrogen-bond acceptor strength (e.g. nitrate) should be considered.

4.4 Theoretical investigations

Accompanying calculations concentrating on the “brown ring” complex were carried out using different methods and functionals on the def2-TZVP level of theory. Results of geometry optimisations were evaluated by comparison with various theoretical publications, due to the absence of empirical data on the issue. Computations of vibrational frequencies were carried out on the same levels, and directly compared to the experimentally obtained values, leaving the B-LYP functional plus dispersion correction as the most likely choice for the calculation of related systems. Apart from that, an extended literature search was performed, comparing hexaqua iron(II) compounds. This led to the result that bond distances and even the occurrence of JahnTeller distortion depend, to a great extent, on the solid-state structure of a compound. It is thus desirable to include the direct environment in calculations, which requires different software suites.

23

Experimental Section

General Procedures

5 Experimental Section 5.1 General Procedures

Syntheses were carried out at ambient temperature under inert nitrogen atmosphere, using Schlenk technique, unless specified otherwise. Reaction vessels were round-bottom flasks, Schlenk flasks or Schlenk tubes of various sizes, the latter baked and vacuum-dried under inert gas. A Schlenk-type vacuum gas manifold (minimal pressure 1·10−3 mbar) was used for this purpose and for drying obtained products. For crystallisation attempts of nitric oxide compounds, before starting the reaction, an open sample vial (10 mL) with the dissolved precursor mixture was placed inside a Schlenk tube containing the precipitant. After the reaction, the product was stored under NO atmosphere at room temperature for several weeks or until signs of decomposition were visible.

5.2 Equipment and Analysis Methods

X-ray crystallography

Nonius Kappa CCD with FR591 rotating anode Oxford Cryostream cooling system

Mass spectrometry

Thermo Finnigan LTQ FT Ultra IonMax ion source with ESI head

Crystal selection

Leica MZ6 microscope with polarisation equipment

Elemental analysis

Vario EL (C, H, N and S content)

IR spectroscopy

Jasco FT/IR-460Plus with ATR Diamond Plate

UV/Vis spectroscopy

Varian Cary 50

Centrifuge

Heraeus Instruments Labofuge 400e

5.2.1 X-Ray Diffraction Crystals suitable for X-ray diffraction were selected using a microscope (Leica MZ6 with polarisation filters), covered with liquid paraffin and mounted on the tip of a glass fibre with Lithelen® grease. The measurements were performed with the following diffractometers: Nonius Kappa-CCD with rotating anode or STOE-IPDS with imaging-plate technology and 24


Equipment and Analysis Methods

sealed-tube anode. Both are equipped with an Oxford Cryostream cooling system and graphite-monochromated Mo-Ka radiation. The structures were solved using direct methods with the program SIR-97[31]. SHELXL-97[32] was used to refine them by full-matrix least-squares refinement against Fo2

Fc2 . Distances and angles were calculated with the program

PLATON[33]. Intermolecular contacts were analyzed with the programs PLATON[33] and MERCURY[34]. Molecular graphics were performed with the programs ORTEP[35], SCHAKAL[36] and MERCURY[34]. Further details on the structures are listed in the Appendix, chapter 6.2, Table 6-1. The values given there are defined as follows:

Rint

Fo2

wR( F )

S

R(F)obs refers to reflctions with I

2

Fo2

(5)

Fo

R( F )obs

2

Fo

Fc Fo

w( Fo2

(6) Fc2 ) 2

w( Fo2 ) 2 w( Fo2 Fc2 ) 2 N hkl N parameter

(7)

(8)

2 (I); S is the goodness of fit; w is the weighting factor,

which is defined as follows:

w

2

1 ( F ) (xP) 2 2 o

where P

yP

2

1 ( F ) (0.02 P ) 2 2 o

max( Fo2 ,0) 2 Fc2 3

(9) (10)

the values of the parameters x and y were adopted to minimise the variance of w( Fc2 / Fo2 ) for several (intensity-ordered) groups of reflexes. Uiso and Uij values in crystallographic information files (CIFs) are defined via isotropic displacement parameters and anisotropic displacement tensors of the general form T = −(ln(f) − ln(fo)) where f are the atomic form-factors and fo describe atomic form-factors for resting atoms:

25


Equipment and Analysis Methods 3

Taniso

2

3

2

U ij ai a j ai* a *j i 1

and Tiso

(11)

j 1

2

8 U iso

sin 2 2

(12)

The coefficient Ueq is defined as a third of the trace of the orthogonalised tensor Uij: U eq

1 3

3

3

U ij ai a j ai* a *j i 1

j 1

(13)

The term shift/errormax specifies the maximal parameter shift divided by the standard deviation of the last refinement step.

5.2.2 Mass Spectrometry Electrospray ionisation (ESI) measurements were carried out on a Thermo Finnigan LTQ FT Ultra fitted with an IonMax ion source with ESI head. The voltage of the spray capillary amounted to 4 kV; the temperature of the heating capillary was 250 °C; nitrogen sheath-gas and sweep-gas flow were at 25 and 5 units, respectively. The resolution was set to 100.000 at m/z 400. Depending on the method, a mass range of 50 – 2000 u was covered in measurements.

5.2.3 Quantum Chemical Calculations Quantum chemical calculations were run on a Linux-based cluster with 64-bit or i686 architecture or on a workstation computer with Windows XP Professional (SP3) operating system, 32-bit architecture, Pentium dual core CPU E5500 @ 2.80 GHz and 3.00 GB memory. They were carried out using Turbomole[16] (v 6.3.1), either via define or TmoleX (v 3.2 or 3.3 beta), with varying methods, using the triple-zeta valence def2-TZVP[37,38] basis set by Weigend and Ahlrichs. The rather large segmented contracted basis set is defined for all atoms H–Rn, including transition metals, and should lead to a small error, especially for DFT methods. A resolution of the identity approach (RI−J) was employed for more efficient computing of the electronic Coulomb interaction. Calculation of the coulomb and HF exchange terms is 26


Equipment and Analysis Methods

based on four-centre two-electron repulsion integrals (ERIs). These terms are simplified to expressions involving three-centre ERIs only, by expanding the molecular electron density in a set of atom-centred auxiliary functions. The scaling behaviour of the exchange evaluation is thus reduced, leading to significant reduction of computational costs. [39] Single-point frequency calculations (employing the same method) were used to test optimised geometries for imaginary vibrational frequencies. In DFT calculations, exchange correlation functionals with different approaches were used: generalised gradient approximations were Becke’s B-LYP (B88[25] exchange and LYP[26] correlation), B-P86 (B88 exchange, VWN(V)[40] and Perdew’s 1986[41] correlation) and PBE[42] by Perdew, Burke, and Ernzerhof. Hybrid functionals, which take the Hartree-Fock exchange (HF) into account, were also evaluated; in this case the widely used three-parameter B3-LYP functional by Becke[27], with the form 0.8S + 0.72B88 + 0.2HF + 0.19VWN(V) + 0.81LYP

(14)

containing contributions from the Slater-Dirac (S)[43,44] and B88 exchange functionals as well as VWN(V) and LYP correlation functionals; and the 1996 PBE0 hybrid functional by Perdew, Burke, and Ernzerhof[45] with the form 0.75(S + PBE(X)) + 0.25HF + PW + PBE(C)

(15)

where PBE(X) and PBE(C) are the Perdew–Burke–Ernzerhof exchange and correlation functionals and PW is the Perdew–Wang[46] correlation functional. General empirical dispersion correction as proposed by Grimme was applied in some of the DFT calculations, using the revised parameters from 2006.[21,47] Where possible, the conductor-like screening model (COSMO) was employed to model the influence of solvation. It is based on a polarizable dielectric continuum with permittivity ε, surrounding a molecule-shaped cavity. The size is calculated relative to the atomic van der Waals radii. Partial atomic charges are taken into account, as well as the surface area exposed to the solvent, allowing a description of the electrostatic potential and the dispersion contribution, respectively.[48,49]

27


Reagents and Solvents

5.2.4 Graph-Set Analysis Graph-set analysis of hydrogen bonding patterns was performed using RPluto[50] (v. 5.26). Descriptors are given in the form Gad(n), with the pattern type G, the number of acceptors a and donors d, as well as the degree n of the pattern, correlating with the number of included atoms. Four basic structural elements are distinguished: infinite chains (C), intermolecular rings (R), intramolecular rings (S), and discrete, finite hydrogen bonding patterns (D).

5.3 Reagents and Solvents

Reagents not available from the house supply were purchased from Sigma, Aldrich, Fluka, SAFC, Merck, Acros, Supelco, Air Liquide and ABCR. Reactions demanding inert gas were carried out using nitrogen from the house pipe without further purification. Table 5-1 gives a list of all chemicals used. Table 5-1: List of Chemicals. chem. Formula acetone C3H6O anhydroerythritol C4H8O3 argon Ar carbon tetrachloride CCl4 Celite (calcined, purified) cis-1,2-cyclohexanediol C6H12O2 cobalt Co cobalt(II) triflate C2F6O6CoS2 12-crown-4 C8H16O4 15-crown-5 C10H20O5 dichloromethane CH2Cl2 diethyl ether C4H10O fructose C6H12O6 glycerol C3H8O3 hexane C6H14 iron powder Fe iron(II) triflate hydrate C2H2F6FeO7S2 isopropanol C3H8O K2[Ru(NO)Cl5] Cl5K2NORu K2[Ru(NO)F5] · H2O H2F5K2NO2Ru lithium Li methanol CH4O Name

MW /g mol-1 58.08 104.11 39.95 153.82 116.16 58.93 357.07 176.21 220.26 84.93 74.12 180.16 92.09 86.18 55.85 353.98 60.10 386.54 322.28 6.94 32.04

Hazard CAS-Nr.

Purity

Source

F, Xi

99.8% 95% 4.0 99% 99% 99.8% 97% 98% 99.9% 99.8% 99% 99.5% 99.5% 98% 99.8% 99% 99.8%

Acros Aldrich Air Liquide Acros Supelco Aldrich Aldrich lit. [17] Acros Aldrich Sigma Aldrich Fluka Fluka Fluka Fluka Grüssing lit. [17] Fluka lit. [20] group Merck Sigma-Aldrich

T, N Xn T+ Xn Xn F+, Xn F, Xn, FN C F F, C F, T

67-64-1 4358-64-9 7440-37-1 56-23-5 91053-39-3 1792-81-0 7440-48-4 58164-61-7 294-93-9 33100-27-5 75-09-2 60-29-7 57-48-7 56-81-5 110-54-3 7439-89-6 59163-91-6 67-63-0 172957-37-8 7439-93-2 67-56-1

28


Syntheses of Metal Triflates chem. Formula Ni C2F6NiO6S2 NO N2 C6H2F12O2 C6H14O2 C5H10O5 C4H8O C7H8 C6H12O2 CF3SO3H

Name nickel nickel(II) triflate nitric oxide nitrogen perfluoropinacol pinacol ribose THF toluene trans-1,2triflic acid cyclohexanediol water

MW /g mol-1 58.69 356.83 30.01 14.01 334.06 118.17 150.13 72.11 92.13 116.16 150.08

H2O

18.02

Hazard CAS-Nr. T Xn O, T+, -C Xn Xi F, Xi F+ C -

Purity

7440-02-0 99.99% 60871-84-3 10102-43-9 99.5% 7727-37-9 99.99% 918-21-8 76-09-5 98% 50-69-1 97% 109-99-9 99.8% 108-88-3 99.7% 1460-57-7 98% 1493-13-6 98% deion7732-18-5 ised

Source Aldrich lit. [17] Air Liquide house supply ABCR Fluka SAFC Merck Fluka Acros ABCR house supply

5.4 Syntheses of Metal Triflates 5.4.1 Iron(II) Triflate from Water Reactants:

Iron powder, triflic acid, water.

Literature:

K. S. Hagen, Inorganic Chemistry 2000, 39, 5867 – 5869.

Procedure: To a mixture of iron powder (5.58 g, 100 mmol) in 100 mL of water, triflic acid (31.5 g, 210 mmol, 18.4 mL) was carefully added, as the reaction is highly exothermic. The mixture was stirred overnight at room temperature and unreacted iron was removed by filtration through a Celite pad. Cooling the bright blue solution to 5 °C afforded light blue crystals of Fe(OTf)2 · 6 H2O, which were filtered and washed with ether (15.6 g, 33.8 mmol, 33.8%). When dried under a vacuum, four to five of the coordinated solvent molecules were lost, resulting in a fine, white, free-flowing powder. The filtrate was again cooled over night at 5 °C to precipitate a second crop of light-blue plates.

Elemental analysis (%): calcd. for C2F6FeO6S2 · 5.8 H2O:

C 5.24, H 2.55, S 13.99

found:

C 5.20, H 2.71, S 14.13

calcd. for C2F6FeO6S2 · 1.3 H2O:

C 6.37, H 0.69, S 16.99

found:

C 6.31, H 0.86, S 17.15 29


Syntheses of Metal Triflates

hr-MS (m/z) ESI−

148.9525 [OTf−], 315.9388

ESI+

327.9659, 311.9936, 329.0089

5.4.2 Iron(II) Triflate from Methanol Reactants:

Iron powder, triflic acid, dry methanol.

Literature:


Procedure: To a mixture of iron powder (5.58 g, 100 mmol) in 100 mL of dry methanol, triflic acid (31.5 g, 210 mmol, 18.4 mL) was carefully added, as the reaction is highly exothermic. The flask was fitted with a reflux condenser and, after the initial effervescence subsided (1 h), warmed to 60 °C. When the effervescence had stopped, the unreacted iron powder was removed by filtration through a Celite pad. The volume of the solution was condensed to approximately 60 mL under vacuum. Cooling the pale green solution to −25 °C (as in the literature) yielded a frozen solid, but cooling at 5 °C afforded very pale blue-green crystals. The product was filtered and washed with anhydrous ether (ca. 20 mL) and yielded very pale blue-green crystals of Fe(MeOH)4(OTf)2 (20.55 g, 43%). When dried under a vacuum, approx. two of the coordinated solvent molecules were lost, resulting in a fine, white, free-flowing powder (17.20 g, 41%). The ether washings were added to the filtrate and cooled to 5 °C to precipitate a second crop.

Elemental analysis (%): calcd. for C2F6FeO6S2 · 2.85 CH4O:

C 13.08, H 2.58, S 14.40

found:

C 12.54, H 2.94, S 13.80

hr-MS (m/z) ESI−

502.7908, 148.9525 [OTf−], 486.8185

ESI+

327.9659, 311.9936, 681.8046, 329.0089

30



5.4.3 Nickel(II) Triflate from Methanol Reactants:

Nickel powder, triflic acid, dry methanol.

Literature:


Procedure: The procedure for Fe(OTf)2 from the literature was used, but working at a higher concentration to enable the oxidation of nickel. To a mixture of finely divided Ni powder (5.87 g, 100 mmol) in 50 mL of dry methanol, triflic acid (31.5 g, 210 mmol, 18.4 mL) was carefully added. The flask was fitted with a reflux condenser and heated to reflux. Additional solvent was added when deep green crystals of Ni(OTf)2 formed on the surface. When the effervescence had stopped, heating was turned off, causing the product to crystallise. It was completely redissolved in dry methanol before the unreacted nickel powder was removed by filtration through a Celite pad. The volume of the solution was condensed to approximately 60 mL under vacuum. Cooling the deep green solution to 5 °C afforded green crystals. The product was filtered and washed with anhydrous ether (ca. 30 mL) to yield Ni(MeOH)4(OTf)2 (9.97 g, 21%) as deep green crystals, which de-composed out of solution due to a loss of solvent. When dried under a vacuum, approx. two of the coordinated solvent molecules were lost, resulting in a fine, light green, freeflowing powder (8.32 g, 20%). The ether washings were added to the filtrate and cooled to 5 °C to precipitate a second crop.

Elemental analysis (%): calcd. for C2F6NiO6S2 · 4.2 CH4O:

C 15.15, H 3.45, S 13.05

found:

C 14.84, H 3.81, S 12.70

calcd. for C2F6NiO6S2 · 2 CH4O:

C 6.37, H 0.69, S 16.99

found:

C 6.31, H 0.86, S 17.15

hr-MS (m/z) ESI−

148.9526 [OTf−], 504.7920

ESI+

329.9665, 311.9937, 331.9619

31



5.4.4 Cobalt(II) Triflate from Methanol Reactants:

Cobalt powder, triflic acid, dry methanol.

Literature:


Procedure: The synthesis was carried out by Christine Neumann, using the procedure for Fe(OTf)2 from the literature. To a mixture of finely divided cobalt powder (5.89 g, 100 mmol) in 100 mL of dry and degassed methanol in a Schlenk flask fitted with a reflux condenser, triflic acid (31.5 g, 210 mmol, 18.4 mL) was carefully added under vigorous stirring over 45min. The mixture was heated to 60 °C. When the effervescence had stopped, heating was turned off, and the mixture cooled overnight. Filtration through a Celite pad afforded a clear dark red solution. The volume of the solution was condensed to approximately a third of the original amount in vacuo. Cooling the now deep purple solution to 5 °C afforded few large translucent light pink crystals, which dissolved upon warming to room temperature. Further reduction of the solvent to approximately 50 mL afforded a light pink precipitate. The solution was filtrated again through a Celite pad, after decantation of the solid, to ensure the removal of contamination was complete. From the red filtrate, the same light pink solid started to precipitate. It was filtered, washed with ether (3 x 20 mL), and dried for 2 h in vacuo to a constant mass. Multiple crops were afforded and combined. After drying for 4 h in vacuo at 65 °C [Fe(OTf)2] ∙ 2 MeOH was isolated (22.19 g, 57.77 mmol). The mother liquor was cooled, and yielded large crystals, which were not suitable for XRD, yielding only bad reflections.

Elemental analysis (%): calcd. for C2F6CoO6S2 · 2 CH4O:

C 11.0, H 1.75, S 15.46

found:

C 10.59, H 2.07, S 15.32

32


Syntheses of Bis(diolato) Compounds

5.5 Syntheses of Bis(diolato) Compounds 5.5.1 General Procedure for Iron(II) Bis(diolato) Compounds Reactants:

Iron(II) triflate, diol, lithium methanolate.

General procedure: Iron(II) triflate (0.372 g, 1 mmol, 2 eq) and diol were dissolved in 1 mL or as little methanol as possible in a Schlenk tube. The solution was first dried over molecular sieve (3 Å) for 2 h before it was transferred to a second Schlenk tube containing lithium methanolate solution (c = 2.3 mol/L) while stirring. Observations are described in detail in chapter 3.1.2. Table 5-2 gives an overview of conducted experiments and ratios. Table 5-2: Overview of experiments regarding iron(II) bis(diolato) compounds. Triflate Fe(Otf)2 · 6 H2O Fe(Otf)2 · 6 H2O Fe(Otf)2 · 1 H2O Fe(Otf)2 · 1 H2O Fe(Otf)2 · 1 H2O Fe(Otf)2 · 1 H2O Fe(Otf)2 · 1 H2O Fe(Otf)2 · 2 MeOH Fe(Otf)2 · 2 MeOH Fe(Otf)2 · 2 MeOH Fe(Otf)2 · 2 MeOH Fe(Otf)2 · 2 MeOH Fe(Otf)2 · 2 MeOH Fe(Otf)2 · 2 MeOH Fe(Otf)2 · 2 MeOH Fe(Otf)2 · 2 MeOH Fe(Otf)2 · 2 MeOH Fe(Otf)2 · 2 MeOH

Diolate AnEryt AnEryt AnEryt AnEryt AnEryt PfPin PfPin AnEryt AnEryt PfPin PfPin PfPin Glyc Rib Fru cis-Chxd trans-Chxd PfPin

Fe : D : B1:2:4 1:4:4 1:2:4 1:4:4 1:4:4 1:2:2 1:2:4 1:4:4 1:2:4 1:2:2 1:2:4 1:2:4 1:1:3 1:2:4 1:2:4 1:2:4 1:2:4 1:2:4

Comments

extra solvent

+ 6 eq water

33


Syntheses of Bis(diolato) Compounds

5.5.2 General Procedure for Nickel(II) Bis(diolato) Compounds Reactants:

Nickel(II) triflate, diol, lithium methanolate.

General procedure: Nickel(II) triflate (0.421 g, 1 mmol, 2 eq) and diol were dissolved in 1 mL or as little methanol as possible in a Schlenk tube. The solution was first dried over mol sieve (3 Å) for 2 h before it was transferred to a second Schlenk tube containing lithium methanolate solution (c = 2.3 mol/L) while stirring. Observations are described in detail in chapter 3.1.3.Table 5-2 gives an overview of conducted experiments and ratios. Table 5-3: Overview of experiments regarding nickel(II) bis(diolato) compounds. Triflate Ni(Otf)2 · 2 MeOH Ni(Otf)2 · 2 MeOH Ni(Otf)2 · 2 MeOH Ni(Otf)2 · 2 MeOH

Diolate AnEryt PfPin Rib Fru

Fe : D : B1:2:4 1:2:4 1:2:4 1:2:4

Comments

5.5.3 General Procedure for Cobalt(II) Bis(diolato) Compounds Reactants:

Cobalt(II) triflate, diol, lithium methanolate.

General procedure: The reactions were carried out by Christine Neumann. Cobalt triflate (1 mmol) was dissolved in dry degassed MeOH (20 mL), before adding anhydroerythritol (0.208 mg, 0.164 mL, 2 mmol, 2 eq). The solution was then dried over molsieve (3 Å) for 12 h. 10 mL degassed dry methanol and a methanolic solution of the base (Lithium methanolate or Sodium methanolate, 4 mmol, 4 eq) were combined in a new Schlenk tube, and the metal/ligand mixture was rapidly added under vigorous stirring. Observations are described in detail in chapter 3.1.3. Table 5-4 gives an overview of conducted experiments.

34


Attempted Syntheses of Iron(II) Nitrosyl Compounds

Table 5-4: Overview of experiments regarding cobalt(II) bis(diolato) compounds. Triflate Co(Otf)2 · 2 MeOH Co(Otf)2 · 2 MeOH Co(Otf)2 · 2 MeOH Co(Otf)2 · 2 MeOH Co(Otf)2 · 2 MeOH

Diolate AnEryt AnEryt AnEryt PfPin PfPin

Base NaOMe LiOMe NaOMe NaOMe LiOMe

Comments

no inert atmosphere

5.6 Attempted Syntheses of Iron(II) Nitrosyl Compounds 5.6.1 Pentaqua Nitrosyl Iron(II) Triflate Reactants:

Iron(II) triflate, nitric oxide.

General procedure: Iron(II) triflate (1.848 g, 4 mmol) was dissolved in as little solvent as possible in a Schlenk tube, which was then flooded with inert gas (argon). Nitric oxide was passed through the reaction vessel for ca. 5–10 min while the solution was stirred. A colour change from light blue (in water) or light green (in methanol) to dark brown occurred. The mixture was then stored under NO atmosphere, with or without a second, less polar solvent to promote crystallisation by diffusion. Table 5-5 gives an overview of tested solvent combinations and relevant observations. Table 5-5: Overview of crystallisation experiments for pentaqua nitrosyl iron(II) triflate. First solvent water 25 mM HOTf in water 25 mM HOTf in water 25 mM HOTf in water methanol 25 mM HOTf in methanol 25 mM HOTf in methanol 25 mM HOTf in methanol 25 mM HOTf in methanol 25 mM HOTf in methanol 25 mM HOTf in methanol THF + 5 eq water THF + 5 eq water THF + 5 eq water

Second solvent

Observations

acetone isopropanol acetone dichloromethane diethyl ether toluene THF toluene n-hexane carbon tetrachloride

after few weeks a certain opacity shows fine red brown precipitate after ca. 1 month phase separation after ca. 1 month phase separation after ca. 1 month -

35


Synthesis of Lithium Methanolate

5.6.2 Pentaqua Nitrosyl Iron(II) Pentachlorido Nitrosyl Ruthenate Reactants:

Iron(II) triflate, nitric oxide, K2[RuCl5(NO)].

General procedure: Iron(II) triflate (0.372 g, 1 mmol, 1 eq) was dissolved in as little water as possible (ca. 0.1 mL). Nitric oxide was passed through the reaction vessel for ca. 5–10 min while the solution was stirred. A colour change from light blue to dark brown occurred. A dark purple solution of K2[RuCl5(NO)] (0.387 g, 1 mmol, 1 eq) in as little water as possible (ca. 3 mL) was added and the mixture was then stored under NO atmosphere for crystallisation, first at room temperature and after a week at 5 °C.

5.6.3 Pentaqua Nitrosyl Iron(II) Pentafluorido Nitrosyl Ruthenate Reactants:

Iron(II) triflate, nitric oxide, K2[RuF5(NO)].

General procedure: Iron(II) triflate (0.152 g, 0.33 mmol, 1 eq) was dissolved in as little water as possible (ca. 0.1 mL) in a Schlenk tube, which was then flooded with inert gas (argon). Nitric oxide was passed through the reaction vessel for 5 min while the solution was stirred. A colour change from light blue to dark brown occurred. A dark purple solution of K2[RuF5(NO)] (0.142 g, 0.33 mmol, 1 eq) in as little water as possible (ca. 3 mL) was added. A second vessel containing ethanol for diffusion was included, before the mixture was stored under NO atmosphere for crystallisation. After ca. 3 h, a fine, light brown precipitate began to form.

5.7 Synthesis of Lithium Methanolate

Reactants:

lithium, methanol.

Procedure: The reaction was carried out under inert argon atmosphere. To dry methanol (45 mL), granulated lithium (0.73 g, 105 mmol) was added in small portions under stirring. A rise in temperature and evolution of gas was observed. If necessary, the solvent loss due to evaporation was compensated for by adding extra methanol to the solu-

36


Synthesis of Lithium Methanolate

tion. After complete addition of lithium, the volume was adjusted to 45 mL, resulting in a concentration of 2.3 mol/L.

37

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Appendix

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[111] R. Hämäläinen, U. Turpeinen, Acta Chemica Scandinavica 1989, 43, 15–18. [112] S. Yoon, S. J. Lippard, Journal of the American Chemical Society 2004, 126, 16692– 16693. [113] T. L. Hatfield, R. J. Staples, D. T. Pierce, Inorganic chemistry 2010, 49, 9312–9320. [114] C. Jia, S.-X. Liu, C. Ambrus, G. Labat, A. Neels, S. Decurtins, Polyhedron 2006, 25, 1613– 1617. [115] R. Ahmad, M. J. Hardie, CrystEngComm 2002, 4, 227. [116] J. Do, X. Wang, A. J. Jacobson, Journal of Solid State Chemistry 1999, 143, 77–85. [117] R. M. Silva, C. Gwengo, S. V. Lindeman, M. D. Smith, G. J. Long, F. Grandjean, J. R. Gardinier, Inorganic chemistry 2008, 47, 7233–7242. [118] D. A. Jeremić, G. N. Kaluđerović, S. Gómez-Ruiz, I. Brčeski, B. Kasalica, V. M. Leovac, Crystal Growth & Design 2010, 10, 559–563. [119] Z. T. Zhang, X. L. Cheng, Y. He, Acta crystallographica Section C, Crystal structure communications 2006, 62, m484–m487. [120] Z.-T. Zhang, X.-L. Cheng, Acta crystallographica Section C, Crystal structure communications 2005, 61, m529–m531. [121] C. Wagner, K. Merzweiler, Zeitschrift für anorganische und allgemeine Chemie 2010, 636, 557–561. [122] K. Honda, H. Yamawaki, M. Matsukawa, M. Goto, T. Matsunaga, K. Aoki, M. Yoshida, S. Fujiwara, Acta Crystallographica Section C, Crystal Structure Communications 2003, 59, m319–m321. [123] H. L. Zhu, D. S. Xia, Q. F. Zeng, Z. G. Wang, D. Q. Wang, Acta Crystallographica Section E, Structure Reports Online 2003, 59, m1020–m1021.

46

Appendix

Crystallographic Data

6.2 Crystallographic Data 6.2.1 Iron(II) Triflate prepared from Methanol

0

Figure 6-1: SCHAKAL packing diagram of iron(II) triflate prepared from methanol, viewed along [−100]. Hydrogen bonds are indicated by cyan dashed lines. The symmetry elements of the space group P-1 are overlaid. Atoms: carbon (grey), hydrogen (white), sulphur (yellow), fluorine (green), oxygen (red), iron (orange).

47

Appendix

Crystallographic Data Table 6-1: Crystallographic table of iron(II) triflate prepared from methanol. Fe(CF3SO3)2 · 4 CH3OH empirical formula C6H16F6FeO10S2 Mr/g mol−1 482.153 crystal system triclinic space group P-1 a/Å 7.1298(10) b/Å 7.6573(6) c/Å 9.4984(13) α/° 68.723(8) β/° 80.245(5) γ/° 66.109(8) V/Å3 441.66(9) Z 1 ρ/g cm−3 1.8128(4) μ/mm−1 1.193 crystal size/mm 0.13 × 0.09 × 0.05 temperature/K 173(2) diffractometer KappaCCD radiation MoKα anode rotating anode rated input/kW 3.025 θ-range/° 3.47–27.50 reflections 1234 absorption correction none reflections measured 2937 observed reflections 1783 Rint 0.0260 mean σ(I)/I 0.0466 reflections with I ≥ σ(I)/I 1507 x, y (weighting scheme) 0.0352, 0.5004 parameters 125 R(Fobs) 0.0450 2 Rw(F ) 0.1002 S 1.084 shift/errormax 0.001 max. electron density/e Å−3 0.364 min. electron density/e Å−3 −0.465

48

Appendix

Additional Information

6.3 Additional Information 6.3.1 Hydrogen Bonds in Hexaqua Complexes of Divalent Metals Table 6-2: Hydrogen bonds in hexaqua complexes of divalent metals as found in the literature. Of 32 examined compounds, only 6 do not show a hydrogen bond per hydrogen ratio of exactly 1. Compound [Cd(H2O)6] [SnF3]2 [Co(H2O)6] [SnF3]2 [Co(H2O)6] [SnF6] [Co(H2O)6] [GeF6] [Co(H2O)6] [AlF5(H2O)] [Cu(H2O)6] [SiF6] [Cu(H2O)6] [SbF4]3 [Fe(H2O)6] [SnF6] [Fe(H2O)6] [SiF6] [Fe(H2O)6] [PtCl6] [Fe(H2O)6] [GeF6] [Mg(H2O)6] [TeCl6] [Mg(H2O)6] [SiF6] [Mg(H2O)6]2 [Ru2Cl10O] · 2 H2O [Mg(H2O)6] [MnCl6] [Mg(H2O)6] [GeF6] [Mg(H2O)6]2 [CdCl6] [Mn(H2O)6] [TiF6] [Mn(H2O)6] [SiF6] [Mn(H2O)6] [FeF5(H2O)] K2 [Ni(H2O)6] [ZrF6]2 [Ni(H2O)6] [SnF3]2 [Ni(H2O)6] [SnF6] [Ni(H2O)6] [SiF6] [Ni(H2O)6] [SbF4]2 [Ni(H2O)6] [GeF6] (NH4) [Ni(H2O)6] [AlF6] Cs2 [Zn(H2O)6] [ZrF6]2 [Zn(H2O)6] [TiF6] [Zn(H2O)6] [SiF6] (NH4) [Zn(H2O)6] [AlF6] [Zn(H2O)6] [AlF5(H2O)]

1

M Cd Co Co Co Co Cu Cu Fe Fe Fe Fe Mg Mg Mg Mg Mg Mg Mn Mn Mn Ni Ni Ni Ni Ni Ni Ni Zn Zn Zn Zn Zn

2

M Sn Sn Sn Ge Al Si Sb Sn Si Pt Ge Te Si Ru Mn Ge Cd Ti Si Fe Zr Sn Sn Si Sb Ge Al Zr Ti Si Al Al

X F F F F F F F F F Cl F Cl F Cl Cl F Cl F F F F F F F F F F F F F F F

Anion Type (MX3)2 (MX3)2 MX6 MX6 MX5(H2O) MX6 (MX4)3 MX6 MX6 MX6 MX6 MX6 MX6 M2X10O MX6 MX6 MX6 MX6 MX6 MX6 MX6 (MX3)2 MX6 MX6 (MX4)2 MX6 MX6 MX6 MX6 MX6 MX6 MX5(H2O)

HB / H 1 1 1 1 ) 1 1 1 ? 1 1 ) 1 1 1 1 1

H···X 191–214 166–175 184–189 171–218 181–210 185–200 161–163 182–199 244 196–202 191–214 225–282 225–229 186–194 192–212 190–212 177–211 182–197 170–177 186–188 202–208 163–187 196–202 178–188 181–205 177–220 194–221 178–193 194–200

O···X Lit 265–275 [51] 264–273 [52] 274–279 [53] [54] 278 265–270 [55] 269–299 [56] 269–281 [57] 173–174 [58] 272–284 [59] [60] 333 271–287 [54] 303–351 [61] 279–284 [62] 318–335 [63] 307–315 [64] 177–179 [65] 329–233 [66] 272–275 [67] 278–282 [68] 262–280 [55] 264–274 [69] 264–271 [70] 273–275 [53] 268–278 [71] 270–272 [57] 270–278 [54] 261–270 [72] 273–283 [73] 271–289 [74] 271–284 [75] 259–269 [72] 265–269 [72]

49

Appendix


6.3.2 Jahn-Teller Distortion in [Fe(H2O)6]2+-Ions Table 6-3: Jahn-Teller distortion in hexaqua-iron(II) compounds as found in the literature, including differences in Fe-O bond length. Only 12 of 55 compounds do not show a distorted octahedral environment, with many of them forming three dimensional networks of hydrogen bonds or weak contacts.

[Fe(H2O)6] [ClO4]2

X

Fe-O Bond Length [Å] eq. axial ∆ 2.123 0

[Fe(H2O)6] (OTf)2

X

2.103–2.105

Compound

[Fe(H2O)6] (OTs)2

[Fe(H2O)6] (MesSO3)2

FeSO4 · 7 H20

FeSO4 · 7 D2O [Fe(H2O)6] [GeF6] [Fe(H2O)6] [PtCl6] [Fe(H2O)6] [SnF6] [Fe(H2O)6] [FeBr3(CO)3]2 K2 [Fe(H2O)6] (SO4)2 K2 [Fe(H2O)6] (SO4)2, RT K2 [Fe(H2O)6] (SO4)2, (298 K) Tl2 [Fe(H2O)6](SO4)2 Rb2 [Fe(H2O)6] (SO4)2 (NH4)2 [Fe(H2O)6] (SO4)2 [C(NH2)3]2 [Fe(H2O)6] (SO4)2

JT?

2.116– 2.082 2.119 2.105– 2.114 (✔) 2.107 2.098– 2.126 ✔ 2.102 2.094, 2.098, asym 2x 2.120 2.100, 2.110 2.140– 2.093 ✔ 2.150 2.122– 2.181 ✔ 2.125 2.10– 2.18 ✔ 2.11 2.08– 2.18 ✔ 2.09 X 2.101 X 2.133 X 2.132 X 2.116 2.128– 2.098 ✔ 2.137 2.164 2.064 ✔ 2.166– 2.070 ✔ 2.171 2.140– 2.081 ✔ 2.183 2.144– 2.091 ✔ 2.155 2.155– 2.074 ✔ 2.159 2.136– 2.086 ✔ 2.156 2.100– 2.130 ✔ 2.105 ✔

0.002 0.034– 0.037 (0.007– 0.009) 0.024– 0.028

CCDC-ID/ Lit ICSD-Code 100372 [76] QEDCOR, [17] 280328 QUKQIW

[77]

-

[28]

34380

[78]

157296

[79]

63449 420080 163595 68452

[54]

260555

[81]

409984

[82]

162314

[83]

172062

[84]

710004

[85]

−0.081

409493

[86]

0.050– 0.070

14346

[87]

0.025

WAJKAU

[88]

0.047– 0.057 0.054– 0.059 0.07– 0.08 0.09– 0.10 0 0 0 0 0.030– 0.039 0.100 −0.099– 0.105 0.059– 0.102 0.053– 0.064

[60] [80] [58]

50

Appendix

Compound (bipy) [Fe(H2O)6] (SO4)2 · 2 H2O [Fe(na)2(H2O)4] [Fe(H2O)6] (SO4)2 · 2 H2O (piperazine) [Fe(H2O)6] (SO4)2 (20 °C)

(piperazine) [Fe(H2O)6] (SO4)2 (-173 °C)

(piperazinium) [Fe(H2O)6] (SO4)2

[Fe(H2O)4(ampyz)2] [Fe(H2O)6] (SO4)2 · 2 H2O [Co(H2O)4(ampyz)2] [Fe(H2O)6] (SO4)2 · 3 H2O [Fe(H2O)4(gly)2] [Fe(H2O)6] (SO4)2 [Fe(pd)3]2 [Fe(H2O)6] (ClO4)6 Cs [Fe(H2O)6] PO4 (x-ray, 273 K) Cs [Fe(H2O)6] PO4 (neutron, 50 K) [Fe(H2O)6] (12K4)6 (I3)2 [Fe(H2O)6] [Os(CO)3Cl3]2 [Fe(H2O)6] [RuCl3(CO)3]2 [Fe(H2O)6] [RuCl3(CO)3]2 · 2 H2O Polymorph I [Fe(H2O)6] [RuCl3(CO)3]2 · 2 H2O Polymorph II [Fe(H2O)6] [Ru(CO)3I3]2 · 2 H2O [Fe(H2O)6] [Fe(H2O)3(SO4)2]2 [Fe(H2O)6][Al2(PO4)2(OH)2(H2O)2] [Fe(H2O)6] [Fe(cit)(H2O)]2 (NH4)2 [Fe(H2O)6] [Ti(H2cit)3]2 · 6 H2O (NH4)5 [Fe(H2O)6] [Ti(H2cit)3(Hcit)3Ti] · 3 H2O

Additional Information Fe-O Bond Length [Å] eq. axial ∆ 2.104– 0.024– 2.131 ✔ 2.107 0.027 2.148– 0.062– 2.086 ✔ 2.171 0.085 2.109– (0.009– 2.124 (✔) 2.115 0.015) 2.101– 2.130– (0.012– ✔ 2.118 2.145 0.044) 2.110– 0.016– 2.138 ✔ 2.122 0.028 2.117– 0.019– 2.145 ✔ 2.126 0.028 2.093– 2.159– 0.053– ✔ 2.106 2.169 0.076 2.125– 0.035– 2.090 ✔ 2.128 0.038 2.129– 0.034– 2.095 ✔ 2.134 0.039 2.107– 0.038– 2.152 ✔ 2.114 0.045 2.090– 0.026– 2.138 ✔ 2.112 2.048 2.070– 2.377 0.300 ✔ 2.081 X 2.119–2.121 0 X 2.141 0 X 2.128 0 2.101– 0.035– 2.148 ✔ 2.115 0.047 2.076– 0.065– 2.141 ✔ 2.095 0.057 2.102– 0.042– 2.153 ✔ 2.111 0.051 2.101– 0.023– 2.128 ✔ 2.105 0.027 5x 0.043– asym 2.092– 1x 2.168 0.076 2.115 2.132– −0.055– 2.077 ✔ 2.141 0.064 2.118– 0.042– 2.076 ✔ 2.141 0.065 (X) 2.12–2.20 (0.08) 2.115– (0.010– ? 2.132 2.122 0.017) X 2.094 0 C32.133 2.056 0.077 axis JT?

CCDC-ID/ Lit ICSD-Code NATGEV

[89]

JEYPIN

[90]

JIZJIM

[91]

JIZJIM01

XAZLAM

[92]

XAZLAM01

[93]

WAHPEC [94]

WAHPIG GLYCFE

[95]

BACVOR

[96]

172377

[97]

YUPJOJ

[98]

DIJRUK

[99]

WEKXIU WEKXOA

[100]

WEKXOA01 DIJRIY

[99]

15207

[101]

24909

[102]

FEACIT

[103]

GINVOP

[104]

ICEJOQ

[105]

51

Appendix


Compound

JT?

[Fe(H2O)6] [Fe(dpto)3]2 · 12 H2O

X

[Fe(H2O)6] [Mo2(edta)O2(µ-O)2] · 5 H2O

?

(NH4)2 [Fe(H2O)6] [Fe(dipic)2]2 (H2dipic)2 · 4 H2O

✔

{[Fe(H2O)6] [Fe(ptc)(H2O)2]2 ·2 H2O}n

(✔)

[Fe(H2O)6] [Cu(2,4-pydca)2]

✔

[Fe(H2O)6] [Fe(sal-gly)2]2 · 2 H2O

? ✔

4F-Ph

[Fe(H2O)6] (O2CAr

)2 · 2 THF ✔

[Fe(H2O)6] [Fe(TCTA)]2 (TCN-DBTTF) [Fe(H2O)6] [FeBr4]3 [Fe(H2O)6] [(MeCN)(CTV)]4 [Co(C2B9H11)2]2 · 4 H2O [NMe4]2 [Fe(H2O)6] [Mo8O26] [Fe(H2O)6] [HB(mt-da)3]2 · 6 H2O [Fe(H2O)6] (campher)2 [Fe(H2O)6] (difs)2 · 4 H2O [Fe(H2O)6] (difs)2 · 8 H2O [Fe(H2O)6](Hsb)2 [Fe(H2O)6] (pic)2 · 2 H2O [Fe(H2O)6] (NO3)2 ·2 (hmta) · 4 H2O

C3axis

Fe-O Bond Length [Å] CCDC-ID/ Lit ICSD-Code eq. axial ∆ 2.136 0 CEYRIH [106] 2.105– 2.136– (0.001– UCETAX [107] 2.135 2.146 0.041) 2.094– 0.047– 2.161 ZILZID [108] 2.114 0.067 2.061– (0.012– 2.078 FEPPOG [109] 2.066 0.017) 2.099– 2.157– (0.011– FESRAX [110] 2.146 2.215 0.116) 2.121– (0.008– 2.113 DIMPOE10 [111] 2.124 0.011) 2.116– 0.025– 2.153 2.128 0.037 FEMTAT [112] 2.104– 0.042– 2.167 2.125 0.063 2.124

2.089– 2.106 dis- 2.21– ord. 2.38 2.128 ✔ 2.087– ✔ 2.091 2.118– ✔ 2.135 2.066– ✔ 2.116 2.138– ✔ 2.155 2.082– ✔ 2.113 2.078– ✔ 2.109 2.065– ✔ 2.066 ✔

2.149

0.025

AVISAA

[113]

2.14

0.034

YEKPAG

[114]

OGATOV

[115]

KABTOW

[116]

JOHCIT

[117]

PUQWOO

[118]

WEPQOY

[119]

DAYCUC

[120]

ONOTER

[121]

EJELIO

[122]

AMITAR

[123]

0.27– 0.45 2.011 −0.117 0.039– 2.130 0.043 2.081– 0.037– 2.092 0.043 0.041– 2.157 0.091 −0.095– 2.043 0.112 0.045– 2.158 0.076 0.055– 2.164 0.086 1.93

2.024

−0.041

(abbreviations: na = nicotinamide, cit = citrate, TCN-DBTTF = tetracyanodibenzotetrathiafulvalene, 2,4-pydca = 2,4-pyridinedicarboxylate, gly = glycinate, edta = ethylenediaminetetraacetate, dipic = dipicolinate, hmta = hexamethylenetetramine, pd = 1,10-phenanthroline-5,6-dione, dpto = 1,3dimethyl-2,4,5,6(1H,3H)-pyrimidinetetrone-5-oximate, difs = 4',7-dimethoxyisoflavone-3'-sulfonate, sal-gly = N-salicylideneglycinate, pic = picrate, O2CAr4F-Ph = 2,6-di-(p-fluorophenyl)benzoate, ptc = pyridine-2,4,6-tricarboxylate, bipy = 4,4’−bipyridyl, HB(mt-da)3 = tris(mercaptothiadiazolyl)borate, CTV = cyclotriveratrylene, Hsb = 4-carboxylbenzenesulfonate, ampyz = aminopyrazine, TCTA = 1,4,7triazacyclononane-N,N’,N’’-triacetate).

52