Structural Methods in Molecular Inorganic Chemistry

Preface xiii
CompanionWebsite xv
Acknowledgements xvii
Biographies xix
1. Determining Structures - How and Why 1
1.1 Structural chemistry - where did it come from? 1
1.2 Asking questions about structure 4
1.3 Answering questions about structure 5
1.4 Plan of the book 7
1.5 Supplementary information 8
2. Tools and Concepts 9
2.1 Introduction 9
2.2 How structural chemistry techniques work 10
2.3 Symmetry 11
2.4 Electron density 21
2.5 Potential-energy surfaces 21
2.6 Timescales 24
2.7 Structural definitions 26
2.8 Sample preparation 27
2.9 Quantitative measurements 30
2.10 Instrumentation 32
2.11 Data analysis 36
3. Theoretical Methods 45
3.1 Introduction 45
3.2 Approximating the multi-electron Schrodinger equation 46
3.3 Exploring the potential-energy surface 52
3.4 Extending the computational model to the solid state 56
3.5 Calculating thermodynamic properties 61
3.6 Calculating properties of chemical bonding 63
3.7 Comparing theory with experiment: geometry 65
3.8 Comparing theory with experiment: molecular properties 68
3.9 Combining theory and experiment 74
4. Nuclear Magnetic Resonance Spectroscopy 79
4.1 Introduction 79
4.2 The nuclear magnetic resonance phenomenon 79
4.3 Experimental set-up 83
4.4 The pulse technique 86
4.5 Information from chemical shifts 92
4.6 Information from NMR signal intensities. 100
4.7 Simple splitting patterns due to coupling between nuclear spins 101
4.8 Information from coupling constants 112
4.9 Not-so-simple spectra 116
4.10 The multi-nuclear approach 120
4.11 Multiple resonance 121
4.12 Multi-pulse methods 126
4.13 Two-dimensional NMR spectroscopy 129
4.14 Gases 140
4.15 Liquid crystals 140
4.16 Solids 141
4.17 Monitoring dynamic phenomena and reactions 147
4.18 Paramagnetic compounds 154
5. Electron Paramagnetic Resonance Spectroscopy 169
5.1 The electron paramagnetic resonance experiment 169
5.2 Hyperfine coupling in isotropic systems 171
5.3 Anisotropic systems 175
5.4 Transition-metal complexes 179
5.5 Multiple resonance 182
6. Mossbauer Spectroscopy 189
6.1 Introduction 189
6.2 The Mossbauer effect 189
6.3 Experimental arrangements 192
6.4 Information from Mossbauer spectroscopy 194
6.5 Compound identification 204
6.6 Temperature- and time-dependent effects 208
6.7 Common difficulties encountered in Mossbauer spectroscopy 212
6.8 Further possibilities in Mossbauer spectroscopy 213
7. Rotational Spectra and Rotational Structure 219
7.1 Introduction 219
7.2 The rotation of molecules 219
7.3 Rotational selection rules 224
7.4 Instrumentation 228
7.5 Using the information in a spectrum 229
7.6 Using rotation constants to define molecular structures 232
8. Vibrational Spectroscopy 237
8.1 Introduction 237
8.2 The physical basis; molecular vibrations 237
8.3 Observing molecular vibrations 239
8.4 Effects of phase on spectra 245
8.5 Vibrational spectra and symmetry 248
8.6 Assignment of bands to vibrations 254
8.7 Complete empirical assignment of vibrational spectra 262
8.8 Information from vibrational spectra 263
8.9 Normal coordinate analysis 272
9. Electronic Characterization Techniques 277
9.1 Introduction 277
9.2 Electron energy levels in molecules 278
9.3 Symmetry and molecular orbitals 279
9.4 Photoelectron spectroscopy 281
9.5 Valence excitation spectroscopy 286
9.6 Electronic energy levels and transitions in transition-metal complexes 289
9.7 Circular dichroism 298
10. Diffraction Methods 303
10.1 Introduction 303
10.2 Diffraction of electrons, neutrons and X-rays 304
10.3 Diffraction by gases 308
10.4 Diffraction by liquids 321
10.5 Diffraction by single crystals; symmetry 323
10.6 Diffraction by single crystals; the theoretical basis 329
10.7 Diffraction by single crystals; the experiment. 333
10.8 Diffraction by single crystals; interpretation of results 341
10.9 Diffraction by single crystals; electron density determination 349
10.10 Topological features of the electron density 352
10.11 Phase dependence of molecular structures 363
10.12 Diffraction of neutrons by crystals 365
10.13 Diffraction by powders 368
10.14 High-pressure crystallography 368
10.15 Extended X-ray absorption fine structure 371
11. Mass Spectrometry 383
11.1 Introduction 383
11.2 Experimental arrangements 383
11.3 Data analysis 387
11.4 Combined mass spectrometry methods 392
12. Case Histories 399
12.1 Introduction 399
12.2 Xenon compounds 400
12.3 The structure of N2O3 407
12.4 Bismuthine 409
12.5 Tetrahydroborates 410
12.6 Is beryllocene a sandwich compound? 415
12.7 Silylium cations - free at last 418
12.8 True phosphinous acids 422
12.9 Dihydrogen and dihydride complexes 425
12.10 Agostic interactions: alkyl hydrogen atoms binding to metal atoms 428
12.11 Lower symmetry than expected in some phosphines and phosphoranes 430
12.12 Three-membered rings with dative bonds? 432
12.13 Stable radicals 436
12.14 Induced proton transfer in an adduct of squaric acid and bipyridine 441
12.15 High-pressure studies of metal organic framework materials 443
12.16 Mistaken identity: mono-coordinate copper(I) and silver(I) complexes 446
12.17 Oxidation states in a palladium-tin complex 447
12.18 Structural and spectroscopic consequences of a chemical change in an iron complex 450
12.19 Some metalloproteins 454
12.20 Atoms inside fullerene cages 459
12.21 Structural chemistry - where is it going? 463
Discussion problem 464
References 464
Index 467