Lecture I

51 downloads 352 Views 631KB Size Report
(all lectures till from September 19 to October 17, 2012). MS-709 , TEL : 1511; email ... Nomenclature, Isomerism and valence bond theory 1. 2. CRYSTAL FIELD ...
CYL 120 (INORGANIC)

Prof. A. K. Ganguli AKG

Organic : Prof Nalin Pant Minor I & II

1+7 J D Singh AKG 2

(all lectures till from September 19 to October 17, 2012) MS-709 , TEL : 1511; email : [email protected] October 18 to Nov 16 : Prof J D Singh

Quiz ( october)

Major Exam : AKG & JDS (inorganic)

A K Ganguli (ashok@chemistry ([email protected]), iitd ac in) MS MS-709 709, Tel :1511 1. Transition metal complexes – REVISION of Nomenclature, Isomerism and valence bond theory 1

2.

CRYSTAL FIELD Theory

7

Magnetic / optical properties of complexes Structural distortion in metal complexes

3. Introduction to Inorganic Solids

2

Books Recommended 1 James 1. J E E. H HuHeey H Inorganic chemistry 2 F. 2. FA A. Cotton Cotton, G G. Willkinsion and P. P L. L Gaus Basic Inorganic Chemistry, J. Wiley and sons (1995) – Singapore 3. Shriver and Atkins : Inorganic Chemistry

( my part) Quiz

(10 marks; 30 min)

Major

(20 marks; 1 hr)

Why Study Inorganic Chemistry?? Intellectual Pursuit Practical Impact 1. Eight out top ten chemicals are Inorganic. (H2SO4) max tonnage 2. Inorganic Materials (Semi conductors, Light guides on linear optical materials, super conductors) d t ) G GaAs, A KT KTaO3, O3 LiNbO3, LiNbO3 YBa2Cu3O7 YB 2C 3O7

Dupont, Monsanto, Dow Chemicals, Hercules, Baeyer, Unilever – Top p Chemical Companies p

ATOMIC ORBITALS

p

s

d

f

Hψ ψ =Eψ

S h di Schrodinger,s equation ti

Ψ = R(r) Θ(θ, φ) n = 1, 2, 3, ………. l = 0 to n-1

Quantum numbers

For n = 1, l = 0

1s sub shell

For n = 2, l = 0, 1 l=0

2s sub shell

l=1

2p sub shell

Ml = -ll tto +l +l.

example Y−11(θ,Ԅ)=(1/2)(√3/√2π)(sinθ)e−iԄ. Ml =-1, l = 1

Transition Metal Complexes

Transition Metal? Elements having partial filled ‘d’ or ‘f’ shell in any of their commonly occurring oxidation states. Fe, Co, Ni, Cu, Ag, Au etc d - block transition metals. f -block block (inner) transition metals (Lanthanides and actinides)

Metals,, variable oxidation states,, hard,, high g melting g point p

Transition metal complexes / Coordination Compounds A central atom, ion surrounded by anions or neutral molecules, which are Lewis bases and may be monoatomic or polyatomic, neutral or anionic (ligands) are coordination compounds. Ligand: Lewis base bonded (coordinated) to a metal ion in a coordination compound.

L

L

Lewis acid

M

L Lewis base

Monodentate, bidentate

L

Coordination compounds p on dissolution give g rise to complex p ions (complexes) [Retains the identity in solution] [Cr(NH3)6]Cl3 Coordination compound

[Cr(NH3)6]3+ + 3ClComplex ion

How Complexes differ from Double salts??

Double salts on dissolution in water lose their identity Dissolve in water

K+, Al3+, SO2-

K2SO4.Al2(SO4)3.24H2O (Alum)

No complex ion

Complex ions don’t lose their identity on dissolution Dissolve in water

[Co(NH3)6]Cl3

[Co(NH3)6]3+ + 3ClComplex ion

S. M. Jorgensen (1837 – 1914) A. Werner

(1866 - 1919)

Synthesized y manyy transition metal complexes

1st Nobel prize in Inorganic chemistry

(1913) : Werner

CoCl3 – NH3 Complexes compound

Colour

Moles of AgCl

Werner’s formula

CoCl3. 6NH3

Yellow

3

[Co(NH3)6]Cl3

CoCl3. 5NH3

Purple

2

[Co(NH3)5Cl]Cl2

CoCl3. 4NH3

Green

1

[Co(NH3)4Cl2]Cl

W Werner’s ’ main i Study St d Primary Valencies [Co(NH3)6]Cl3 + 3AgNO3

3AgCl + Co(NH3)63+

Secondary Valencies Normally fixed for a particular ion and oxidation state.

[Mn(H2O)6]SO4 2+

H2O H2O H2O

Mn

Electrostatic interaction

SO42-

H2O Covalent bond

H2O H2O

Octahedral complex

Coordination number is 6 (secondary valency) Mn2+

Central metal ion (lewis acid)

H2O

Ligand (Lewis base)

Types of Ligands M Monodentate d t t ligands li d Donate one pair of electrons to a central metal ion. e g Cl-, Br-, I-, NH3, H2O e.g.

Bidentate ligands They have two donor atoms Ethylenediamine (en)

H2N – CH2 – CH2 – NH2

M Di th l glycol Dimethyl l l (glyme) ( l )

CH3O – CH2 – CH2 – OCH3

M COOM

Oxalate ion (oxalato) COO-

More Examples NH2 – CH2 – COO-

Glycinato (gly)

-OOC

bidentate

– CH2 – NH – CH2 – COO-

Iminodiacetato (imda) tridentate NH2 – CH2 – CH2 – NH – CH2

Triethylenetetramine (tren)

NH2 – CH2 – CH2 – NH – CH2 tetradentate -OOC

Ethylenediamine tetraacetate (edta)

– CH2

CH2 – COON – CH2 – CH2 - N

-OOC

– CH2

hexadentate

CH2 – COO-

Ambidentate Ligands O

O–N=O

N O

nitrito Nitro SCN-

thiocyanato

NCS

isothiocyanato

Organic Ligands

N

N 2, 2’-Bipyridine (bpy)

N

N

1,10 – Phenanthroline (phen)

Alkyl groups as ligands CH3 (methyl), CH3CH2 (ethyl), C6H5 (Phenyl)

Macrocyclic ligands

N

N

N

N

Porphyrin

tetradentate

Nomenclature of Transition metal Compounds A. Writing the name of the complex compound 1 Designation of ligands 1. (a) Anionic ligands end with ‘o’ NO2nitro, CNClchloro, NO3-

cyano nitrato

(b) Organic ligands retained their names Pyridine (py) or ethylenediamine (en) alkyl groups: methyl, phenyl (c ) Special names H2O (aqua), NO (nitrosyl), CO (carbonyl), NH3 (ammine)

2. Designation of metal (a) Cationic and neutral complexes end in the english name followed by the oxidation state of the metal in brackets. e.g. nickel(II) or iron(II).

(b) Anionic complexes have the latin name of the metal ferrate( ) ,

Stannate ( )

C Cuprate t (),

A Argentate t t ()

3. Numerical prefixes (a) For two similar ligands di or bis (b) three similar ligands tri or tris (c ) four similar ligands tetra or tetrakis etc.

3. Order of listing The ligands are to be written in alphabetical order (irrespective of charge) eg [CoCl2(NH4)]+ Cleg. dichlorotetraamminecobalt(III) chloride.

wrong

tetraamminedichlorocobalt(III) chloride.

right

A. Writing the formulae of the complex compound 1. First central metal atom , then anionic ligands and then neutral ligands (Cl-,NH NH3) [Co (NH3)4Cl2]Cl

wrong

[CoCl2(NH3)4]Cl

correct

Examples 1. [Co (NO2)6] Cl3 hexanitro cobalt (III) chloride

2. [Cu(NH3)4]SO4 tetra amminecopper(II)sulphate

3. [CuCl2(py)2] bis pyrridinedichlorocopper(II) py pp ( ) dichloro dipyridine copper (II) dichloro bis (py (pyridine)) copper pp ((II))

4. cis-[Pt(NH3)2Cl2] cis-diamminedichloroplatinum(II)

Geometry of complexes

C Cu

(linear)

Coordination No.2 [NC---Ag---CN]

[C (CN)2 [Cu(CN) CH3----Hg-----CH3

CN

]-

CN

Cu

Cu

Polymeric compound Coordination no. 4

(large ligands) (b) Tetra hedral

(a) Square planar Mainly d8 systems Cl

2-

Cl

Cl Pt

Cl

2-

Ni Cl

Cl Cl

Cl

Coordination no. 5

L

L L L

L M L

L L

M L

tbp

Sq. pyramidal

L

[Ni (CN)5]2- shows both structures (little energy differenc) [CuCl5]3+ NbCl5

TBP structure TBP structure

O2

Fe

Bi l i ll important Biologically i t t molecules l l Haemoglobin,

Oxomyoglobin

N

N

N

N

L

Coordination no. 6 ML6 octahedral complex M t important Most i t t from f d1 to t d9

L

L M

L

L

e. g. [Cr(NH3)6]3+ , [Fe(CN)6]3-

L

Higher coordination possible with large cations and small anions e.g. [ZrF7]3-, TaCl4(PR3)3 [Nd(OH2)9]3+, [ReH9]2-, [Ce(NO3)6]2-

Square q antiprism p icosahedron

Isomerism

Structural Isomerism

Stereoisomerism

Geometrical (Same frame work b t different but diff t spatial ti l arrangement of the ligands)

Optical (non-superimposable i images) i ) mirror

Ionization Hydrate y Coordination Linkage Pol meri ation Polymerization Ligand isomer

Geometrical Isomers (coordination no. 4) A B

A

B

A

M

M

M B

A

A

B

B

B

A

trans

cis

tetrahedral Square planar

All are optically inactive

Cis/ trans isomers can be isolated

Pt

2-

Cl

Cl

NH3

Pt Cl

Cl

Cl

NH3

E Excess NH3

NH3

Cl I NH3

NH3

Pt NH3

NH3

II

Geometrical Isomerism in Octahedral complexes

MA3B3

A

A

B

A

Facial

A RuCl3(H2O)3

B

MA2B4

B

B

B

B M

B

B

B

Meridonal

A

A

M

cis

B

Co(NO ( 2)3((NH3)3

B

A

A

A

M

B

M

B

e.g. [Co Cl2(NH3)4] +

trans

B A

Optical isomerism Optical isomers differ only in the direction in which they rotate the plane of the plane polarized light (enantiomers). -- -- ---- -

α

solution

plane polarized light

Absence of optical activity

(superimposable mirror images)

1. Presence of a mirror plane. 1 plane 2. Presence of a centre of symmetry. Cl NH3

Cl NH3

NH3 M

NH3

NH3 Cl Trans

+ dextro - laevo

Cl M

[CoCl2(NH3)4]+ Optically inactive

NH3

NH3

NH3 Cis

NH2

Cl

Cl

Co

Cl

Co

NH2

NH2

NH2

NH2 NH2

cis

NH2

Non superimposable mirror images. Cl NH2

NH2

(Optically active)

trans

Co Not optically active NH2

NH2 Cl

Cl

NH2 N

Bonding Concept

(Rationalise structure)

Bonding in coordination compounds Sidgwick (1927) ¾ Extended the Lewis theory ¾ Sharing of ‘e’ pair donated by an atom (donor). Effective atomic Number (EAN) M accepts electron pairs and converted into inert gas configuration. e.g.

[Co(NO2)6]3-

Co (Z = 27) Co3+ = 24e 6(NO2)- = 6*2e = 12e ----------------------

TOTAL = 36e Atomic no. of Krypton (Kr)

Chemical Bonding G N. G. N Lewis L i (1916) Sharing of e-’s

Bonding between atoms

H H

C

.. H H

H

Structure ??

N H H

Lewis diagram C Concept t off h hybridization b idi ti

Valence bond Theory (Pauling – Slater, 1930’s) Li Linus Pauling P li – N.L. N L (t (twice) i ) “ Nature of the chemical bond”

Bond angles ??

Valence bond Theory (Pauling)

Complexes

1. Metal ion must make available a number of orbitals equal to the coordination number for accommodating the electrons from the ligands. 2. Use of the hybrid orbitals by the metal ion. ¾ Maximum & fruitful overlap with ligand orbitals ¾ Directionality Note: Hybrid orbitals are not s, p or d orbitals but have a mixed character.

Why Hybridisation? CH4

F Four bonds b d

C

11s2 2 2s2 2p 2 2 Promotion of one s electron

x

1s2 2s2 2px1 2py1 2py1 Results in three mutually perpendicular bonds.

pX

H z

Hy

90 90

H

H x

But

H

109o

109o

C

CH4 is Tetrahedral

H

H H All

HCH are equal

Successes of V. B. T. 1. Simple structure and Magnetic properties are nicely explained. l i d 2. Accounts for low spin square planer and high tetrahedral complex. 3. Low spin inner – orbital and high spin orbital complexes. Failures [Cu(NH3)4]2+ 1. Cannot predict 4 – coordination ― square planer or tetrahedral VB T 2+ Cu : 3d9

3d

[Zn(NH3)4]2+

(planar) (tetrahedral)

both to be tetrahedral

4s

4p

3d

4s

4p

sp3 dsp2 But by experiments there is no evidence of unpaired e- in orbital: e. s. r spectroscopy

22. VBT does not predict any distortion in the symmetrical complexes. [ideal ― octahedra, tetrahedra] Au Cu(II) Au, Cu(II), Ti(III) complexes are distiorted among many more. more 3 VBT neglects 3. l t th the exited it d states t t off the th complexes. l ―no thermodynamic properties can be predicted 4. It does not explain the colour (spectra) of complexes. 5. Does not explain p the temperature p variation of magnetic g properties of complexes.