Download Transition Metal Chemistry

Malcolm Gerloch, Edwin C. Constable
Transition Metal
Chemistry
The Valence Shell in d-Block Chemistry
Weinheim • New York
Basel • Cambridge • Tokyo
Contents
Preface
1
An Introduction to Transition-Metal Chemistry
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
What is a Transition Element?
Complexes and Coordination Compounds
The Coordinate Bond
Ligand Types
Coordination Number
Geometrical Types and Isomers
Oxidation State
Electroneutrality Principle
Rationalization of Complex Geometries
Review of Properties of Transition-Metal Compounds
1
3
5
5
8
9
12
14
15
17
2
Focus on the d" Configuration
21
2.1
2.2
2.3
Spectral Features
The Valence Shell
The Roles of d Electrons
21
23
26
3
Crystal-Field Splittings
27
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11
3.12
The Crystal-Field Premise
Splitting of d Orbitals in Octahedral Symmetry
Splitting of d Orbitals in Tetrahedral and Other Symmetries
Holes: dl and d9
More Transitions for d2
Atomic Orbitals and Terms
Crystal-Field Splitting of Free-Ion D Terms
Crystal-Field Splitting of Free-Ion F terms
Free-ion S and P Terms in Crystal Fields
Splitting Patterns for d" Ground terms
Orgel Diagrams
Concluding Remarks
27
28
32
34
36
40
44
46
48
52
56
58
X
Contents
4
The Intensities of 'd-d' Spectra
61
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
Transition Moments
Selection Rules
'Violation' of the Selection Rules
Intensity 'Stealing'
'Two-Electron Jumps'
'Spin-Flip' Transitions
The Effects of Temperature Change
Summarizing Remarks
61
62
64
69
71
72
74
76
5
Spin and Magnetism
77
5.1
5.2
5.3
5.4
5.5
5.6
77
79
88
90
93
5.7
High-Spin and Low-Spin Configurations
The Qualitative Origin of Paramagnetism
'Orbital Quenching' and the 'Spin-Only' Formula
Orbital Contributions
Orbital Contributions at the Strong-Field limit
The Chemical Relevance of Departures from
the Spin-Only Formula
Summary
6
Ligand Fields, Bonding and the Valence Shell
97
6.1
6.2
6.3
6.3.1
6.3.2
6.3.3
6.3.4
95
96
The Nephelauxetic Effect
The Spectrochemical Series
Bonding in Octahedral Complexes
Molecular Orbitals in Diatomic Molecules
Molecular Orbitals in Polyatomic Molecules
Molecular Orbitals for the Water Molecule
The Molecular Orbital Diagram for Octahedral Complexes:
Local M - L a Bonding
6.3.5 Charge-Transfer Transitions
6.3.6 Metal-Ligand it Bonding
6.4 Ligand-Field Theory
6.5 Synergic Back-Bonding
6.6 Valence Shells in High and Low Oxidation States
6.7 Electroneutrality and the Elasticity of the d Shell
6.8 The Bonding Contributions of d Orbitals
97
99
102
102
104
104
7
Steric Effects of Open d Shells
129
7.1
7.2
7.3
7.4
Bond Lengths in Octahedral Complexes
Planar Coordination in ds Complexes
Trigonal Bipyramidal Coordination
The Jahn-Teller Effect
129
131
135
137
108
114
114
117
121
124
126
127
Contents
XI
8
Complex Stability and Energetics
145
8.1
8.2
8.2.1
8.2.2
8.2.3
8.3
8.4
8.4.1
8.4.2
8.4.3
8.5
The Thermodynamic Stability of Complexes
The Chelate Effect and Polydentate Ligands
Thermodynamic Origins of the Chelate Effect
Contributions to the Chelate Effect - The Enthalpy
Contributions to the Chelate Effect - The Entropy
Ligand-Field Stabilization Energies
Energy and Structural Consequences in Real Systems
Hydration Energies of Transition-Metal(n) Ions
Lattice Energies of MC12 Species
The Spinels
The Irving-Williams Series
145
146
147
148
149
149
152
152
158
159
161
9
Chemical Consequences of the rf-Electron Configuration
167
9.1
9.2
9.2.1
9.3
9.4
9.4.1
9.4.2
9.4.3
9.4.4
9.4.5
9.4.6
Introduction
Coordination Number and Geometry
Coordination Numbers in Low Oxidation State Complexes
Ligand types - The Concept of Hard and Soft
The Stabilization of Oxidation States, and Reduction Potentials
Reduction Potentials and Thermodynamics
Intermediate Oxidation States
The Electroneutrality Principle - A Reprise
Protic Equilibria Involving Coordinated Ligands
The Stabilization of High Oxidation States
d Orbitals, Covalent Character and Variable Oxidation States A Summary
9.5
Consequences of the d-Electron Configuration
upon Reaction Rates
9.5.1 Kinetically Inert and Labile Complexes
9.5.2 Ligand Substitution Reactions
9.5.3 Rates of Electron Transfer Reactions
167
167
172
173
176
176
176
179
181
184
10
The Lanthanoid Series
197
10.1
10.2
10.3
10.4
The Lanthanoid Contraction
The Core-Like Behavior of / Electrons
Magnetic Properties in the / Block
Spectral Features
197
198
199
203
Index
184
186
186
186
189