List of Contributors ........................................... xv
1.1 Theory and Concepts in Main-Croup Cluster Chemistry ......... 1
R. Bruce King and Paul v. R. Schleyer
Introduction ................................................ 1
1.1.1 Three-center Bonding in Boranes: Lipscomb's
Equations of Balance .................................. 4
1.1.2 Polyhedral Skeletal Electron Pair Theory: The
Wade-Mingos Rules ..................................... 6
1.1.3 Aromaticity in Three-dimensional Clusters ............. 8
1.1.3.1 From Polygonal Aromatics to Deltahedral
Boranes ....................................... 8
1.1.3.2 Interstitial Polygonal Aromatic-Deltahedral
Borane Relationships ......................... 11
1.1.3.3 Aromaticity Evaluations of Three-
dimensional Structures: Nucleus-
Independent Chemical Shift (NICS) ............ 12
1.1.3.4 Spherical Aromaticity ........................ 16
1.1.4 Bare Ionic Post-transition Metal Clusters: The Zintl
Phases ............................................... 17
1.1.5 Clusters of the Heavier Group 13 Metals .............. 21
1.1.5.1 Apparently Hypoelectronic Deltahedra in
Bare Clusters of Indium and Thallium:
Polyhedra with Flattened Vertices ............ 21
1.1.5.2 Organometallic Deltahedral Clusters of
the Heavier Group 13 Metals and More
Complicated Structures Derived from
Deltahedra ................................... 23
1.1.5.3 Giant Aluminum Clusters with Shell
Structures Consisting of Nested
Polyhedra: Pieces of Icosahedral
Quasicrystals ................................ 28
1.1.6 Conclusion and Outlook ............................... 29
References ................................................. 30
2.1 Homonuclear Boron Clusters ................................. 34
H. Noth
2.1.1 Introduction ......................................... 34
2.1.2 General Principles and Systematic Naming ............. 35
2.1.2.1 Structures and Bonding ....................... 36
2.1.3 Synthetic Methods .................................... 45
2.1.3.1 Diborane Pyrolysis ........................... 46
2.1.3.2 The Anionic Route ............................ 47
2.1.3.3 Platinum-catalyzed Dehydrocoupling ........... 50
2.1.3.4 Cluster Expansion and Cluster Contraction
Reactions .................................... 52
2.1.4 Chemistry of Selected Polyboranes .................... 52
2.1.4.1 Chemistry of Triborane B3H7 .................. 52
2.1.4.2 Chemistry of Tetraboranes .................... 54
2.1.4.2.1 arachno-Tetraborane(lO) ............ 54
2.1.4.2.2 Derivatives of mdo-Tetraborane(8),
B4H8, and closo-Tetraborane(6),
B4H7 ............................... 57
2.1.4.3 Chemistry of Pentaborane(9) .................. 60
2.1.4.4 Chemistry of Decaborane(14) .................. 63
2.1.5 Chemistry of Selected nido- and closo-Polyborane
Anions ............................................... 67
2.1.5.1 Chemistry of closo-B6H62- .................... 68
2.1.5.2 Chemistry of the Nonahydro-closo-
nonaborate(2-) ............................... 71
2.1.5.3 Reaction of Decahydro-closo-decaborate(2-) ... 72
2.1.5.4 Chemistry of the nitro-Decaborate B10H13 ..... 73
2.1.5.5 Chemistry of Undecahydro-closo-undecaborate
B11H112- ...................................... 73
2.1.5.6 Chemistry of the Dodecahydro-closo-
dodecaborate ................................. 77
2.1.5.6.1 Protonation and Alkylation
of B12H122- ......................... 77
2.1.5.6.2 Halogeno-. Hydroxo-,
Alkoxo-and Amine closo-
dodecaborates ....................... 77
2.1.5.7 Chemistry of B20H182- Anions .................. 80
2.1.6 Substituted Neutral Polyboranes of Type ByXy ......... 84
2.1.6.1 Overview ..................................... 84
2.1.6.2 Structures ................................... 84
2.1.6.3 Synthesis .................................... 85
2.1.6.4 Reactions .................................... 89
References ................................................. 90
2.2 Boron Clusters in Medical Applications ..................... 95
Detlef Cabel and Yasuyuki Endo
2.2.1 Introduction ......................................... 95
2.2.2 Dicarba-closo-dodecaborane, C2B10H12,
and Derivatives ...................................... 99
2.2.2.1 Preparation and Reactions of C2В10 Cage
Compounds .................................... 99
2.2.2.2 Design and Classification of BNCT Reagents
Containing C2B10 Cages ...................... 100
2.2.2.3 Amino Acids ................................. 100
2.2.2.4 Nucleic Acid Precursors ..................... 101
2.2.2.5 DNA Binders ................................. 103
2.2.2.6 Porphyrins .................................. 104
2.2.2.7 Combination of C2В10 and
Gadolinium-containing Species ............... 105
2.2.3 Derivatives of the nido-carborane C2B9H122- ......... 106
2.2.4 Application of C2В10 for Drug Design ................ 108
2.2.4.1 Properties of С2В10 for Drug Design ......... 108
2.2.4.2 Nuclear Receptor Ligands Bearing C2Bio
Cages ....................................... 110
2.2.5 cbso-Boranes ........................................ 113
2.2.5.1 B12H122- .................................... 114
2.2.5.1.1 Introduction of Heteroatoms as
Substituents of B12H122- .......... 114
2.2.5.1.2 Reactivity of B12H11SH2- .......... 115
2.2.5.1.3 Reactivity of B12H11SH2- .......... 116
2.2.5.1.4 Reactivity of B12H11SH2- .......... 116
2.2.5.1.5 Analytical and Chromatographic
Properties ........................ 117
2.2.5.1.6 Compounds for BNCT Derived from
the B12H122- Cluster .............. 117
2.2.5.2 Azanonaboranes .............................. 118
2.2.6 Testing of Compounds for BNCT ....................... 119
References ................................................ 122
2.3 Clusters of the Heavier Croup 13 Elements ................. 126
G. Linti, H. Schnockel, W. Uhl and N. Wiberg
2.3.1 Introduction ........................................ 126
2.3.2 The Metal-Metal Bond ................................ 127
2.3.3 Boron Analogous Clusters of the Type [EnRn]x-
(x = 0,1,2) ......................................... 129
2.3.3.1 Tetrahedral Cluster Compounds E4R4 .......... 130
2.3.3.1.1 Syntheses ......................... 130
2.3.3.1.2 Bonding ........................... 134
2.3.3.1.3 Structures ........................ 136
2.3.3.1.4 Physical Properties ............... 137
2.3.3.1.5 Reactivity ........................ 138
2.3.3.2 Miscellaneous (Neutral and Anionic)
Cluster Compounds E6R6,
E8R8, E9R9 E12R12 ............................. 141
2.3.4 Metalloid (Neutral and Anionic) Clusters EnRm < n .... 144
2.3.4.1 Metalloid Clusters AlnRm < n ................ 145
2.3.4.1.1 Al7- Al12- and In12 Clusters ....... 145
2.3.4.1.2 Al14 Cluster ...................... 146
2.3.4.1.3 Al69 and AI77 Clusters ............ 146
2.3.4.1.4 Hypothetical β-Aluminum ........... 148
2.3.4.2 Metalloid Gallium Clusters
GanRm < n and Related Indium
Clusters .................................... 150
2.3.4.2.1 The Modifications of
Elemental Ga ...................... 150
2.3.4.2.2 Ga6 Cluster ....................... 152
2.3.4.2.3 Ga9 and Related In
Clusters .......................... 152
2.3.4.2.4 Ga12 Clusters ..................... 154
2.3.4.2.5 Ga10 Ga13 and
Ga19 Clusters ..................... 155
2.3.4.2.6 Ga18, Ga26 and Ga26 Clusters ....... 158
2.3.4.2.7 The Ga84 Cluster .................. 160
2.3.5 Summary and Outlook ................................. 162
References ................................................ 163
2.4 Discrete and Extended Metal Clusters in Alloys
With Mercury and Other Croup 12 Elements .................. 169
Hans-Jörg Deiseroth
2.4.1 Introduction ........................................ 169
2.4.2 Mercuride Clusters in Amalgams - Conflicts With
Zintl's Concept? .................................... 170
2.4.2.1 General ..................................... 170
2.4.2.2 Small Mercuride Clusters .................... 173
2.4.2.3 Single "Mercuride" Ions? .................... 176
2.4.2.4 Extended Anionic Partial Structures of
Mercury ..................................... 178
2.4.2.5 MHgn Clusters With High Coordination
Numbers ..................................... 181
2.4.2.6 NaK29Hg48 A Complex Ternary
Amalgam With Mercury Acting as a Pseudo
Group 13 Element [9] ........................ 183
2.4.2.7 Electric and Magnetic Properties of
Amalgams .................................... 185
2.4.3 Conclusions ......................................... 185
Acknowledgements .......................................... 186
References ................................................ 186
2.5 Molecular Cages and Clusters of the Heavier
Croup 14 Elements (E = Si, Ce, Sn or Pb)
of Formula EnRm (n ≥ m) ................................... 188
Nils Wiberg and Philip P. Power
2.5.1 Introduction ........................................ 188
2.5.2 Silicon Species of Formula SinRm(n ≥ m) ............. 189
2.5.2.1 Dimers and Trimers .......................... 189
2.5.2.2 Tetramers ................................... 189
2.5.2.3 Hexamers and Octamers ....................... 191
2.5.3 Germanium Cages and Clusters GenRm (n < m) .......... 193
2.5.3.1 Dimers ...................................... 193
2.5.3.2 Germanium Trimers ........................... 194
2.5.3.3 Germanium Tetramers ......................... 196
2.5.3.4 Germanium Hexamers, Octamers and
Decamers .................................... 197
2.5.4 Tin Cages and Clusters and SnnRw (n ≥ m) ............ 199
2.5.4.1 Dimers. Trimers and Tetramers ............... 199
2.5.4.2 Hexamers, Octamers and Decamers ............. 201
2.5.5 Lead Clusters PbnRn ................................. 205
2.5.6 Conclusion .......................................... 206
References ................................................ 206
2.6 Homoatomic Cages and Clusters of the Heavier Group 15
Elements: Neutral Species and Cations ..................... 209
Ingo Krossing
2.6.1 Introduction ........................................ 209
2.6.2 Neutral Homonuclear Pnicogen Clusters ............... 211
2.6.2.1 Structures of the Tetrahedral E4 Cages ...... 211
2.6.2.2 Bonding in P4 ............................... 211
2.6.2.3 Larger Pn Cages (n < 4) ..................... 214
2.6.3 Cationic Homonuclear Pnicogen Clusters .............. 216
2.6.3.1 Overview .................................... 216
2.6.3.2 Reaction Media and Environment for Bi
Cluster Syntheses ........................... 217
2.6.3.3 Structurally Characterized Bi
Cations [42] ........................ 217
2.6.3.1 What About Gaseous Pn+ and Asn+ Cations? .... 221
2.6.3.5 The Stability of Hypothetical Pn+ and Asn+
Cations in Condensed Phases ................. 223
2.6.4 Outlook ............................................. 225
Acknowledgement ........................................... 225
References ................................................ 226
2.7 Cages and Clusters of the Chalcogens ...................... 230
William S. Sheldrick
2.7.1 The Elements ........................................ 230
2.7.2 Homopolyatomic Cations .............................. 232
2.7.2.1 The вп Aromatic Cations E42+ ................ 233
2.7.2.2 Bonding in Hexanuclear Te64+ and Te62+ ....... 234
2.7.2.3 Molecular Structures of Te84+ and E82+ ....... 237
2.7.2.4 Larger Polycations and Polymers ............. 238
2.7.2.3 Polychalcogenide Anions ..................... 240
2.7.3.1 Polytelluride Anions With Cluster-like
Building Units .............................. 241
2.7.4 Summary and Outlook ................................. 243
References ................................................ 244
3.1 Alkali and Alkaline Earth Metal Suboxides
and Subnitrides ........................................... 246
Arndt Simon
3.1.1 Introduction ........................................ 246
3.1.2 Alkali Metal Suboxides .............................. 247
3.1.3 Barium Suboxides .................................... 254
3.1.4 Alkaline Earth Metal Subnitrides .................... 255
3.1.5 Chemical Bonding and Physical Properties ............ 261
References ................................................ 264
3.2 Carboranes: From Small Organoboranes to Clusters .......... 267
Armin Berndt, Matthias Hofmann, Walter Siebert and
Bernd Wrackmeyer
3.2.1 Introduction and Background ......................... 267
3.2.2 Monocarbaboranes .................................... 273
3.2.2.1 Non-classical Diboriranes ................... 273
3.2.2.2 Non-classical Triboretanes .................. 276
3.2.2.3 Non-classical Bicyclo[1.1.0]triboretanes .... 278
3.2.2.4 Derivatives of 1-Carba-doso-oligoborate
Ions [CH(BH)n] .............................. 279
3.2.2.5 Carba-nido-tetraboranes(7) .................. 280
3.2.2.6 l-Carba-arachno-pentaboranes(lO) ............ 281
3.2.3 Dicarbaboranes ...................................... 282
3.2.3.1 Non-classical 1.3-Dihydro-l,3-diboretes ..... 283
3.2.3.2 Non-classical 1.2-Diboretanylidenes
(Boriranylideneboranes) ..................... 283
3.2.3.3 Non-classical 1.2-Diboretanes ............... 284
3.2.3.4 Dicarba-doso-pentaboranes ................... 285
3.2.3.5 Dicarba-arachno-pentaborane-dianions ........ 287
3.2.3.6 Dicarba-nido-hexaboranes and
Dicarba-doso-boranes ........................ 288
3.2.4 Tricarbahexaborane .................................. 289
3.2.4.1 2.3.5-Tricarba-nido-hexaboranes(7) ......... 289
3.2.4.2 Dianions of 2.4,6-Tricarba-hypho-
hexaborane .................................. 291
3.2.5 Tetracarba-mdo-boranes .............................. 292
3.2.5.1 Tetracarba-nido-hexaboranes ................. 292
3.2.5.2 Tetracarba-nido-octaboranes ................. 294
3.2.5.3 Tetracarba-nido-decaboranes ................. 296
3.2.6 Pentacarba-mdo-hexaboranes .......................... 296
3.2.7 Hexacarbaboranes .................................... 297
3.2.8 Heterocarboranes .................................... 298
3.2.8.1 2.4.5-Azadicarba-nido-hexaboranes .......... 299
3.2.8.2 2.4.5-Thiadicarba-nido-hexaborane .......... 299
3.2.8.3 Nido- and Hypho-lithiacarboranes ............ 300
3.2.9 Conclusions ......................................... 303
References ................................................ 306
3.3 Heteropolyboranes With the Heavier Group 14 Elements ...... 320
Lars Wesemann and Narayan S. Hosmane
3.3.1 Introduction ........................................ 310
3.3.2 Syntheses of Heteropolyboranes With Heavier
Group 14 Elements ................................... 311
3.3.2.1 Twelve Vertex Cfoso-
heteroboranes ....................... 312
3.3.2.2 Eleven Vertex Nido-heteroboranes .... 314
3.3.2.3 Smaller Heteropolyboranes ........... 317
3.3.3 Adducts of Disila-doso-dodecaborane ................. 318
References ................................................ 320
3.4 Borane Clusters with Group 15 and Group 16 Heteroatoms:
Survey of Compounds and Structures ......................... 322
Peter Paetzold
3.4.1 Introduction ........................................ 322
3.4.2 Closo-Clusters ...................................... 323
3.4.2.1 The cl-5 to cl-9 Families ................... 323
3.4.2.2 The cl-10 Family ............................ 325
3.4.2.3 The cl-11 Family ............................ 326
3.4.2.4 The cl-12 Family ............................ 326
3.4.2.4.1 Theoretical Results ............... 326
3.4.2.4.2 Group 16 Heteroatoms .............. 326
3.4.2.4.3 Group 15 Heteroatoms .............. 327
3.4.2.5 The cl-13 Family ............................ 328
3.4.3 Nuio-Clusters ....................................... 329
3.4.3.1 The ni-4 and ni-5 Family .................... 329
3.4.3.2 The ni-6 Family ............................. 329
3.4.3.3 The ni-7 Family ............................. 331
3.4.3.4 The ni-8 Family ............................. 332
3.4.3.1 The ni-9 Family ............................. 333
3.4.3.6 The ni-10 Family ............................ 333
3.4.3.7 The ni-11 Family ............................ 335
3.4.3.8 The ni-12 Family ............................ 337
3.4.4 Arachno-Clusters .................................... 338
3.4.4.1 The ar-5 Family ............................. 338
3.4.4.2 The ar-6. ar-7 and ar-8 Families ............ 339
3.4.4.3 The ar-9 Family ............................. 339
3.4.4.4 The ar-10 Family ............................ 341
3.4.4.5 The ar-11 Family ............................ 343
3.4.5 Hypho-Clusters ...................................... 346
References ................................................ 348
3.5 Heteropolyalanes, -gallanes, -indanes and -thallanes ...... 357
Werner Uhl and Herbert W. Roesky
3.5.1 Clusters Including Carbon and Silicon Atoms ......... 357
3.5.1.1 Aluminum and Gallium Clusters Containing
Silicon ..................................... 357
3.5.1.2 Carbaalanes ................................. 359
3.5.2 Clusters and Cages Including Pnicogen Atoms ......... 366
3.5.2.1 Compounds Derived from Homonuclear
Clusters .................................... 366
3.5.2.2 Amino and Imino Alanes, Gallanes and
Indanes ..................................... 369
3.5.3 Clusters and Cages Including Chalcogen Atoms ........ 375
3.5.3.1 Compounds Derived from Homonuclear
Clusters .................................... 375
3.5.3.2 Oxygen Compounds of Aluminum, Gallium
and Indium .................................. 377
3.5.4 Clusters Including Halogen Atoms .................... 381
3.5.5 Clusters Including Hydrogen Atoms ................... 385
References ................................................ 387
3.6 Cluster Crowing Through Ionic Aggregation: Synthesis
and Structural Principles of Main Croup Metal-Nitrogen,
Phosphorus and Arsenic Rich Clusters ...................... 391
Matthias Driess, Robert E. Mulvey, Matthias
Westerhausen
3.6.1 Fundamental Aspects of Main Group Metal-Group 15
Element Clustering .................................. 391
3.6.2 Common Cluster Motifs in Group 1 Metal- and
Group 2 Metal-Organonitrogen Chemistry .............. 394
3.6.3 Templation and Inverse Crown Chemistry .............. 398
3.6.4 Alkali Metal-Phosphorus and Alkali Metal-Arsenic
Clusters ............................................ 403
3.6.4.1 Introduction ................................ 403
3.6.4.2 Mono- and Dimetalated Phosphane and Arsane
Clusters ..................................... 404
3.6.5 Alkaline-earth Metal- and Tin(+2)-Phosphorus
and -Arsenic Clusters ............................... 412
References .................................................... 421
Index ......................................................... 425
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