basic organometallic chemistry : concepts, syntheses, … · basic organometallic chemistry...
TRANSCRIPT
Basic
OrganometallicChemistryConcepts, Syntheses and Applications of
Transition Metals
B D GuptaProfessor, Department of Chemistry, NT Kanpur
A J EliasProfessor, Department of Chemistry, I IT" Delhi
*¥>Universities Press
CRC PressTaylor & Francis GroupBoca Raton London NewYork
CRC Is an Imprint of the Taylor 6c Francis Group,an Informa business
Contents
Foreword v
Preface vii
List ofabbreviations ix
Chapter i Introduction l
1.1 What is organometallic chemistry? 1
1.2 A briefhistory oforganometallic chemistry 2
1.3 Importance of organometallic compounds 7
1.3.1 Organometallic compounds as reagents 7
1.3.2 Organometallic compounds as additives 10
1.3.3 Organometallic compounds as catalysts 14
Supplementary reading 15
Chapter 2 The 18 Valence Electron Rule 16
2.1 Introduction 16
2.2 The 18 electron rule 16
2.3 Counting of electrons and finding metal-metal bonds 17
Problems and exercises 21
Supplementary reading 25
Chapter 3 Metal Carbonyls 26
3.1 Structure, Tt-bonding and infrared spectroscopy 27
3.2 Bonding modes of CO 31
3.3 Symmetry ofmetal carbonyls 32
3.4 Syntheses of metal carbonyls 32
3.4.1 Direct carbonylation 33
3.4.2 Reductive carbonylation 33
3.5 Reactions ofmetal carbonyls 35
3.5.1 Activation of metal carbonyls 35
3.5.2 Disproportionation 36
3.5.3 Nucleophilic addition to CO 36
3.5.4 Electrophilic addition to the carbonyl oxygen 36
3.5.5 Carbonyl anions, cations and hydrides 37
3.5.6 Collman's reagent 38
3.5.7 Migratory insertion ofcarbonyls 38
3.5.8 Oxidative decarbonylation 39
3.5.9 Photochemical substitution 39
3.5.10 Microwave assisted substitution 40
3.6 Metal nitrosyls 40
Problems and exercises 41
Supplementary reading 44
Chapter 4 NeutralSpectator Ligands: Phosphines and 46
n-heterocyclic carbenes
4.1 Phosphines: steric and electronic parameters 46
4.2 Basicity of phosphines 48
4.3 Monodentate phosphines 50
4.4 Multidentate phosphines 51
4.5 N-Heterocyclic carbenes 53
Problems and exercises 56
Supplementary reading 58
Chapter 5 Alkenes and Alkynes as Ligands 60
5.1 Models ofethylene-metal bonding 60
5.2 Synthesis ofmetal-alkene complexes 63
5.3 Reactions of metal bound alkenes: The concept ofUmpolung 65
5.4 Alkynes: modes of bonding to metals 66
5.5 Reactions ofmetal complexes of alkenes and alkynes 68
5.5.1 Pauson-Khand reaction 71
Problems and exercises 72
Supplementary reading 74
Chapter 6 Carbenes and Carbynes: Complexes withMetal- 76
Carbon Doubleand Triple Bonds
6.1 Metal Carbenes 76
6.1.1 Synthesis of Fischer carbene complexes 76
6.1.2 Synthesis of Schrock carbene complexes 77
6.1.3 Tebbe's reagent 80
6.1.4 Carbenes that are intermediate between 81
the Fischer and Schrock types
6.2 Metal Carbynes 83
6.2.1 Synthesis of metal-carbyne complexes 83
6.2.2 Reactions of metal-carbyne complexes 84
Problems and exercises 85
Supplementary reading 89
Chapter 7 Alkyl, Aryl and Ligands with Higher Hapticity 90
7.1 o bonded alkyl groups as ligands 90
7.1.1 Synthesis of metal-alkyl compounds 90
7.1.2 (3-Hydride elimination 91
7.1.3 a bonded n1 -aryl ligands 92
7.2 Cyclic and acyclic polyenyl rx bonded ligands 92
7.2.1 Cyclopentadienyl (Cp~) 92
7.2.2 Synthesis ofCp based sandwich compounds 93
7.2.3 Structure and properties ofMCp2 complexes 94
7.2.4 Ferrocene: The first metal-sandwich compound 97
7.2.5 Reactions of metal-sandwich compounds 99
7.2.6 Bent sandwich compounds 100
7.2.7 Schwartz's reagent and hydrozirconation 101
7.2.8 Chemistry of Cp* 101
7.2.9 Chemistry of arene sandwich compounds 102
7.2.10 Allyl groups as ligands 104
7.2.11 1,3-Butadiene complexes 106
7.2.12 Cyclobutadiene complexes 108
7.2.13 Cycloheptatriene and cyclooctatetraene as 111
ligands7.3 Davies-Green-Mingos (DGM) rules 111
Problems and exercises 112
Supplementary reading 116
Chapter 8 Unique Reactions in Organometallic Chemistry 117
8.1 Oxidative addition and oxidative coupling 117
8.1.1 Intramolecular oxidative addition: 120
C-H activation and cyclometallation8.1.2 Oxidative coupling 120
8.2 Reductive elimination 121
8.2.1 Mononuclear systems 122
8.2.2 Binuclear systems 125
8.3 Migratory insertion reactions 127
8.3.1 Lewis acid acceleration 128
8.3.2 Redox acceleration 129
8.3.3 Migration versus insertion 129
8.3.4 Insertion of alkenes 132
8.3.5 (3-Hydrogen elimination versus reductive 133
elimination
Problems and exercises 135
Supplementary reading 140
Chapter 9 Ligand Substitution Reactions and Fluxionality in 142
Organometallic Compounds
9.1 Types of ligand substitution reactions 142
9.1.1 Activation entropy and activation volume 143
9.1.2 Factors affecting substitution reactions 144
9.2 Associative substitutions 146
9.2.1 Hapticity change in mulitdentate ligands 147
9.3 Dissociative substitutions 149
9.4 Interchange mechanisms 150
9.4.1 Associative interchange 151
9.4.2 Dissociative interchange 151
9.5 Stereochemical non-rigidity in organometallic compounds 151
9.5.1 Ring whizzing in n'-Cp complexes 153
9.5.2 Interchange of r\l- and rf-Cp rings 155
9.5.3 Allyl complexes 157
9.5.4 Allene complexes 158
9.5.5 Scrambling of carbonyl groups in metal carbonyls 159
Problems and exercises 162
Supplementary reading 164
Chapter 10 Metal Clusters 166
10.1 Introduction 166
10.2 Dinuclear clusters 167
10.2.1 A five fold bonded organometallic compound 169
10.3 Multinuclear carbonyl clusters 170
10.3.1 Low nuclearity carbonyl clusters 170
10.3.2 High nuclearity carbonyl clusters (HNCC) 171
10.3.3 Electron counting schemes for high nuclearity clusters 172
10.3.4 Capping rules 174
10.3.5 Limitations and exceptions 175
10.3.6 Polyhedral skeletal electron pair approach or 176
Mingo's rules
10.3.7 Carbide clusters 179
10.4 The isolobal analogy 180
10.4.1 Clusters having interstitial main group elements 186
10.5 Synthesis of metal carbonyl clusters 187
10.6 Reactions of metal carbonyl clusters 189
Problems and exercises 192
Supplementary reading 194
Chapter ii Homogeneous Catalysis Using Organometallic 196
Compounds
11.1 Catalysis 196
11.2 Terminology in catalysis 198
11.2.1 Turnover 198
11.2.2 Turnover number (TON) 199
11.2.3 Turnover frequency (TOF) or turnover rate 199
11.3 Sequences involved in a catalysed reaction 204
11.4 Other important terminology used in catalysis 205
11.5 Asymmetric synthesis using a catalyst 205
11.6 Heterogeneous catalysis 206
11.6.1 Catalytic converters in automobiles 207
11.7 Feedstock for the chemical industry 208
Problems and exercises 209
Supplementary reading 210
Chapter 12 Catalytic Hydrogenation of Alkenes and Related 211
Reactions
12.1 Hydrogenation catalysts . 211
12.1.1 Classification of hydrogenation catalysts 211
12.1.2 Catalytic cycle ofWilkinson's catalyst 213
12.1.3 Catalytic cycles ofiridium and ruthenium based 214
catalysts12.1.4 Directing effects in catalytic hydrogenation 217
12.1.5 Hydrogenation by lanthanide organometallic 217
compounds12.2 Catalytic asymmetric synthesis 218
12.2.1 The first industrial catalytic asymmetric 219
hydrogenation12.2.2 The mechanism of asymmetric hydrogenation using 220
a chiral catalyst12.2.3 Asymmetric hydrogenation of ketones and 221
isomerisation
12.2.4 Asymmetric hydrogen transfer 224
12.3 Hydrocyanation ofalkenes 226
12.4 Hydrosilylation of alkenes 228
Problems and exercises 231
Supplementary reading 233
Chapter 13 Hydroformylation 235
13.1 Importance of hydroformylation 235
13.2 Cobalt catalysts for hydroformylation 236
13.3 Phosphine modified cobalt catalysts 238
13.4 Rhodium-phosphine catalysts 239
13.5 Factors affecting the n/iso ratio of hydroformylation 241
products13.6 Enantioselective hydroformylation 243
13.7 Carboalkoxylation of olefins 244
Problems and exercises 246
Supplementary reading 248
Chapter 14 Methanol Carbonylation and Olefin Oxidation: 249
Monsanto, Cativa and Wacker Processes
14.1 History of methanol carbonylation 249
14.2 The Monsanto process 250
14.2.1 Problems with the Monsato process 251
14.3 Celanese process using Lil modified rhodium catalyst 251
14.4 Tennessee Eastman acetic anhydride process 252
14.5 British Petroleum's Cativa process 252
14.6 The Wacker process 254
Problems and exercises 257
Supplementary reading 258
Chapter 15 OlefinMetathesis 259
15.1 Olefin metathesis as a synthetic tool 259
15.2 Well known olefin metathesis catalysts and their 260
properties15.3 Synthesis of Grubbs'and Schrock catalysts 260
15.4 Mechanism of olefin metathesis 266
15.4.1 Ring opening metathesis (ROM) 267
15.4.2 Cross metathesis (CM) 267
15.4.3 Ring closing metathesis (RCM) 269
15.4.4 Ring opening metathesis polymerisation (ROMP) 271
15.4.5 Acyclic diene metathesis polymerisation (ADMET) 272
15.4.6 Enyne metathesis (EM) 274
15.5 Comparison of catalysts 275
15.6 Metathesis of hindered olefins 278
15.7 Applications of catalytic olefin metathesis 279
Problems and exercises 281
Supplementary reading 284
Chapter 16 Palladium Catalysed C-C and C-N Cross Coupling 286
Reactions
16.1 Discovery of palladium based cross coupling reactions 286
16.2 Industrial applications of cross coupling reactions 287
16.3 The cross coupling catalyst 288
16.4 The Heck reaction 288
16.5 Suzuki-Miyaura coupling 291
16.6 Sonogashira coupling 295
16.7 Stille coupling 297
16.8 Kumada coupling 298
16.9 Negishi coupling 300
16.10 Hiyama coupling 302
16.11 Buchwald-Hartwig C-N cross coupling 303
16.12 Cross coupling reactions in aqueous media with functional 305
group tolerance
Problems and exercises 309
Supplementary reading 312
Chapter 17 Olefin Polymerisation and Oligomerisation 315
Reactions
17.1 Catalysts for olefin polymerisation 316
17.2 Types of polyethylene and polypropylene 316
17.2.1 Polyethylene 316
17.2.2 Polypropylene 316
17.3 The Ziegler-Natta catalyst 319
17.4 Site control and chain end control mechanisms 320
17.5 Metallocene based catalysts 322
17.5.1 Polypropylenes using metallocenes 322
17.5.2 The mechanism of propylene polymerisation 323
by metallocenes
17.5.3 Polypropylene and stereochemistry 325
17.5.4 Stereo-block polypropylene 326
17.5.5 Constrained geometry catalysts 328
17.6 Post-metallocene catalysts 329
17.6.1 The Brookhart catalysts 329
17.6.2 Fenokishi Imin (FI) and related ligand based 332
metal catalysts17.7 Olefin oligomerisation reactions 335
17.7.1 Shell's higher olefin process 335
Problems and exercises 338
Supplementary reading 342
Chapter 18 Ferrocene: Structure, Bonding and Reactions 344
18.1 Structure and bonding of ferrocene 344
18.2 The reactions of ferrocene and its derivatives 345
18.2.1 Basic chemical reactions offerrocene 347
18.2.2 Reactions of acetyl ferrocene and formyl ferrocene 348
18.2.3 Lithiated ferrocenes and their reactions 350
18.2.4 (Dimethylaminomethyl)ferrocene and 353
its methiodide salt
18.2.5 Ferrocene boronic acid and haloferrocenes 354
18.3 Ferrocene derivatives in asymmetric catalysis 355
18.3.1 Chirality in ferrocene derivatives 355
18.3.2 Synthesis of chiral ferrocene based compounds 358
Problems and exercises 363
Supplementary reading 365
Chapter 19 Organometallic Polymers 369
19.1 Polymers with organometallic moieties as pendant groups 369
19.2 Polymers with organometallic moieties in the main chain 371
19.2.1 Ferrocene based condensation polymers 371
19.2.2 Condensation polymers based on rigid rod polyynes 372
19.2.3 Polymers prepared by ring opening polymerisation 379
process
19.3 Organometallic dendrimers 387
19.3.1 Synthesis of dendrimers: Divergent and 388
convergent methods
Problems and exercises 395
Supplementary reading 399
Chapter 20 Bioorganometallic Chemistry 401
20.1 Introduction 401
20.2 Organometallic enzymes and coenzymes 402
20.2.1 Vitamin B12 coenzyme: 'Nature's most beautiful 402
cofactor'
20.2.2 Nomenclature and structure 403
20.2.3 Correnoid dependant enzymatic reactions 403
20.2.4 Vitamin B12 model compounds 409
20.3 Role of organometallics in heavy metal poisoning 411
20.3.1 Heavy metal toxicity: Mercury related cases 411
20.3.2 Arsenic poisoning 414
20.4 Organometallic compounds as drugs 418
20.4.1 q6-Aryl-ruthenium compounds as general 418
anticancer drugs20.4.2 Ferroquine as antimalarial drug 41920.4.3 Ferrocifen as breast cancer drug 421
20.5 Organometallics as radiopharmaceuticals, tracers, 423
ionophores and sensors
20.5.1 Radiopharmaceuticals 423
20.5.2 Organometallic tracers 424
20.5.3 Organometallics as ionophores 424
20.5.4 Organometallic compounds as sensors 426
Problems and exercises 427
Supplementary reading 429
Appendix 1: Solutions to problems and exercises 431
Appendix 2: Quick revision questions 505
Appendix 3: Atomic weights of the elements 516
Index 520