Foreword to the First Edition ............................. xiii
Preface to the Second Edition ............................... xv
Preface to the First Edition .............................. xvii
1 Introduction: General Aspects ................................ 1
1.1 Aims and Objectives ..................................... 1
1.2 Some Definitions ........................................ 2
1.3 Structures of Some Typical Hypercarbon Systems .......... 5
1.4 The Three-Center Bond Concept: Types of Three-Center
Bonds .................................................. 10
1.5 The Bonding in More Highly Delocalized Systems ......... 21
1.6 Reactions Involving Hypercarbon Intermediates .......... 26
References .................................................. 31
2 Carbon-Bridged (Associated) Metal Alkyls .................... 37
2.1 Introduction ........................................... 37
2.2 Bridged Organoaluminum Compounds ....................... 41
2.3 Beryllium and Magnesium Compounds ...................... 50
2.4 Organolithium Compounds ................................ 53
2.5 Organocopper, Silver, and Gold Compounds ............... 58
2.6 Scandium, Yttrium, and Lanthanide Compounds ............ 62
2.7 Titanium, Zirconium, and Hafnium Compounds ............. 64
2.8 Manganese Compounds .................................... 66
2.9 Other Metal Compounds with Bridging Alkyl Groups ....... 68
2.10 Agostic Systems Containing Carbon-Hydrogen-Metal
3c-2e Bonds ............................................ 70
2.11 Conclusions ............................................ 76
References .................................................. 77
3 Carboranes and Metallacarboranes ............................ 85
3.1 Introduction ........................................... 85
3.2 Carborane Structures and Skeletal Electron Numbers ..... 87
3.2.1 Closo Carboranes ................................ 88
3.2.2 Nido and Arachno Carboranes ..................... 89
3.2.3 Carbon Sites in Carboranes; Skeletal
Connectivities к ................................ 97
3.2.4 Skeletal Bond Orders in Boranes and Carboranes .. 98
3.3 Localized Bond Schemes for Closo Boranes and
Carboranes ............................................. 98
3.3.1 Lipscomb's Styx Rules and Williams' Stx Rules ... 98
3.3.2 Bond Orders and Skeletal Connectivities ........ 100
3.3.3 Bond Networks and Skeletal Connectivities ...... 101
3.3.4 Calculated Charge Distributions and Edge Bond
Orders ......................................... 102
3.4 MO Treatments of Closo Boranes and Carboranes ......... 104
3.5 The Bonding in Nido and Arachno Carboranes ............ 107
3.5.1 Localized Bond Schemes ......................... 107
3.5.2 MO Treatments of Nido and Arachno Boranes and
Carboranes ..................................... 108
3.5.3 Some Boron-Free Nido and Arachno Systems ....... 110
3.6 Methods of Synthesis and Interconversion Reactions .... 111
3.7 Some Carbon-Derivatized Carboranes .................... 114
3.7.1 Carboranyl C-H—X Hydrogen-Bonded Systems ....... 114
3.7.2 Carboranyl-Metal Systems ....................... 114
3.7.3 Some Aryl-Carboranes ........................... 116
3.8 Boron-Derivatized Carboranes: Weakly Basic Anions
[СВ11Н6Х6]- ........................................... 122
3.9 Metallacarboranes ..................................... 123
3.9.1 Structural Types, Electron Counts, and
Isolobal Units ................................. 123
3.9.2 Predicting Structures from Formulae ............ 126
3.9.3 Metal Complexes of CxBy Ring Systems ........... 130
3.10 Supraicosahedral Carborane Systems .................... 133
3.11 Conclusions ........................................... 137
References ............................................ 137
4 Mixed Metal-Carbon Clusters and Metal Carbides ............. 149
4.1 Introduction .......................................... 149
4.2 Complexes of CnHn Ring Systems with a Metal Atom:
Mdo-Shaped MCn Clusters ............................... 150
4.3 Metal Complexes of Acyclic Unsaturated Ligands,
CnHn+2 ................................................ 157
4.4 Complexes of Unsaturated Organic Ligands with Two or
More Metal Atoms: Mixed Metal-Carbon Clusters ......... 160
4.5 Metal Clusters Incorporating Core Hypercarbon Atoms ... 162
4.6 Bulk Metal Carbides ................................... 173
4.7 Metallated Carbocations ............................... 176
4.8 Conclusions ........................................... 176
References ................................................. 177
5 Hypercoordinate Carbocations and Their Borane Analogs ...... 185
5.1 General Concept of Carbocations: Carbenium Versus
Carbonium Ions ........................................ 185
5.1.1 Trivalent-Tricoordinate (Classical) Carbenium
Ions ........................................... 186
5.1.2 Hypercoordinate (Nonclassical) Carbonium Ions .. 187
5.2 Methods of Generating Hypercoordinate Carbocations .... 188
5.3 Methods Used to Study Hypercoordinate Carbocations .... 189
5.3.1 NMR Spectroscopy in Solution ................... 189
5.3.2 13C NMR Chemical Shift Additivity .............. 192
5.3.3 Isotopic Perturbation Method ................... 192
5.3.4 Solid-State 13C NMR at Extremely Low
Temperature .................................... 193
5.3.5 X-Ray Diffraction .............................. 193
5.3.6 Tool of Increasing Electron Demand ............. 194
5.3.7 ESCA ........................................... 194
5.3.8 Low Temperature Solution Calorimetry ........... 195
5.3.9 Quantum Mechanical Calculations ................ 195
5.4 Methonium Ion (CH5+) and Its Analogs .................. 195
5.4.1 Alkonium Ions Incorporating Bridging
Hydrogens (Protonated Alkanes, СnН2n+3+) ....... 195
5.4.2 Hypercoordinate Carbocations Containing 3c-2e
С—С—С Bonds .................................... 223
5.5 Homoaromatic Cations .................................. 247
5.5.1 Monohomoaromatic Cations ....................... 247
5.5.2 Bishomoaromatic Cations ........................ 249
5.5.3 Trishomoaromatic Cations ....................... 256
5.5.4 Three-Dimensional Homoaromaticity .............. 258
5.5.5 Mцbius Homoaromaticity ......................... 259
5.6 Hypercoordinate (Nonclassical) Pyramidal
Carbocations .......................................... 260
5.6.1 (CH)5+-Type Cations ............................ 260
5.6.2 (CH)62+-Type Dications ......................... 264
5.7 Hypercoordinate Heterocations ......................... 266
5.7.1 Introduction ................................... 266
5.7.2 Hydrogen-Bridged Silyl Cations ................. 266
5.7.3 Homoaromatic Heterocations ..................... 267
5.8 Carbocation-Borane Analogs ............................ 268
5.8.1 Introduction ................................... 268
5.8.2 Hypercoordinate Methonium and Boronium Ions .... 272
5.8.3 Cage Systems ................................... 272
5.8.4 Hypercoordinate Onium-Carbonium Dications and
Isoelectronic Onium-Boronium Cations ........... 274
5.9 Conclusions ........................................... 276
References ................................................. 277
6 Reactions Involving Hypercarbon Intermediates .............. 295
6.1 Introduction .......................................... 295
6.2 Reactions of Electrophiles with C-H and C-C Single
Bonds ................................................. 298
6.2.1 Acid-Catalyzed Reactions and Rearrangements
of Alkanes, Cycloalkanes, and Related
Compounds ...................................... 298
6.2.2 Nitration and Nitrosation ...................... 325
6.2.3 Halogenation ................................... 328
6.2.4 Carbonylation .................................. 331
6.2.5 Oxyfunctionalization ........................... 332
6.2.6 Sulfuration .................................... 339
6.2.7 Reactions of Coordinatively Unsaturated Metal
Compounds and Fragments with C-H and C-C о
Bonds .......................................... 340
6.2.8 Reactions of Singlet Carbenes, Nitrenes, and
Heavy Carbene Analogs with C-H and C-C Bonds ... 371
6.2.9 Rearrangement to Electron-Deficient Metal,
Nitrogen, and Oxygen Centers ................... 377
6.3 Electrophilic Reactions of π-Donor Systems ............ 383
6.4 Bridging Hypercoordinate Species with Donor Atom
Participation ......................................... 388
6.4.1 Carbocations with 3c-2e Bond ................... 388
6.4.2 Five-Coordinate SN2 Reaction Transition
States and Claimed Intermediates ............... 389
6.4.3 Six-Coordinate Hypervalent Compounds ........... 393
6.5 Conclusions ........................................... 394
References ................................................. 394
Conclusions and Outlook .................................... 417
Index ...................................................... 419
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