IX Table of Contents A. Historical Introduction (by 0. J. Scherer and M. Regitz) B. Bonding Properties of Low Coordinated Phosphorus Compounds (by W, W. Schoeller) 1. Introduction 5 5.5 Reactivity 18 2. Bonding in Higher Main Group 5.5.1 Carbenic Behaviour 18 Chemistry 6 5.5.2 Electron Demand in Diels-Alder 2.1 The Inert s-Pair Effect 6 Reactions 18 2.2 Hybridization, Nonhybridization . 7 5.5.3 Sulfur Addition to P(III) Double 2.3 Sizes of Atoms and Orbitals 7 Bonds 19 2.4 Polarizability 7 6. Phosphacumulenes 20 2.5 Stereochemical Activity of the 7. Allylic Systems 21 "Inert" s-Orbital 8 7.1 Phosphenium and Nitrenium 3. 7r-Bond Strengths between First Cations 21 and Second Long Period Elements . 10 7.2 2-Phosphaallylic Cations 21 4. Triple Bonds 11 8. Bis(ylene)phosphoranes 22 4.t Cyanide vs. Isocyanide Homo- 8.1 Structural Aspects 22 logues 11 8.2 Electrocyclic Ring Closure 23 4.2 Bridging Phenomena 12 9. Metaphosphates 24 5. Double Bonded Phosphorus 12 10. Phosphoranes 24 5.1 General Considerations 12 11. Phosphaaromatic Systems 25 5.2 Ionization Potentials, Redox 12. 7t-Bonding in Phosphinonitrene Potentials 13 and Phosphinocarbene 25 5.3 Iminophosphines 14 13. Ring Strain in Cyclophosphines ... 25 5.3.1 Phosphinonitrene Isomerization . 14 14. Metal Complexation of Phos­ 5.3.2 Structural Effects 15 phorus rc-Bonds 26 5.3.3 cw/;ro/j^-Isomerization at Nitrogen 16 14.1 ^'-versus ^2-Complexation 26 5.4 Diphosphenes 16 14.2 Sandwich Formation 26 5.4.1 Structural Effects 16 15. References 27 C. Phosphorus Compounds with Coordination Number 1 33 1. Phosphinidenes 33 1.1 In Situ Generated Phosphinidcncs (by F. Mathey) 33 1.1.1 Introduction 33 ff'J'-P —P 1.1.2 Syntheses 34 http://d-nb.info/901523712 X Table of Contents 1.1.3 Reactions 36 e) Cyclopentadienes and Cyclohexa- 1.1.4 Ligand Properties 38 dienes 82 1.1.4.1 General Remarks 38 f) 1,3-Butadienes and Hetero- 1.1.4.2 Synthesis of Terminal Phosphini- 1,3-dienes 83 dene Complexes . 38 2.4.2.5 Homo-Diels-Alder Reaction 85 1.1.4.3 Reactions of Terminal Phosphini- 2.4.2.6 1,2-Addition 86 dene Complexes 41 a) Halogen Compounds 86 1.1.5 Addendum 45 b) Organolithium Compounds .... 87 1.2 Binuclear Phosphinidene c) Enophiles 87 Compounds 2.4.3 Addendum 89 (by G. Huttner and H. Lang) 48 2.4.4 Acknowledgements 89 1.2.1 Introduction 48 2.5 The Behavior of a1,^-Phospha­ 1.2.2 Syntheses 48 alkynes in the Coordination 1.2.3 Bonding and Spectroscopy 50 Sphere of a Transition Metal 1.2.4 Reactivity 53 (by P. Binger) 90 1.3 References 55 2.5.1 Metal Complexes with (r',A3-Phosphaalkynes 90 2. Phosphaalkynes (Alkylidyne- 2.5.1.1 End-On Coordination 90 phosphines) 2.5.1.2 Side-On Coordination 90 (by M. Regitz) 58 2.5.2 Dimerization and Codimerization of <7',/l3-Phosphaalkynes 93 (71, A3-P P = C 2.5.2.1 Metal Complexes by Oxidative Coupling of Two Phosphaalkynes . 94 2.5.2.2 Metal Complexes by Oxidative 2.1 General Remarks 58 Coupling of One Phosphaalkyne 2.2 Physical Properties 58 with Another Unsaturated System . 98 2.3 Syntheses 59 2.5.3 Trimerization and Cotrimerization 2.3.1 Elimination Reactions 59 of a'.A'-Phosphaalkynes 101 2.3.1.1 Hydrogen Halide 59 2.5.3.1 Metal Complexes by Trimerization 2.3.1.2 Chlorotrimethylsilane 60 of cr1,A3-Phosphaalkynes 101 2.3.1.3 Hexamethyldisiloxane . 60 2.5.3.2 Metal Complexes by Cotrimeri­ 2.3.1.4 Lithium Trimethylsilanolate 62 zation of u'j/l'-Phosphaalkynes 2.3.2 Rearrangement Reactions 62 with Other Unsaturated Systems ... 103 2.3.3 Miscellaneous Syntheses 63 2.5.4 Low-Coordinated Organic Phos­ 2.4 Reactions 64 phorus Compounds by Substitution 2.4.1 Thermal Cyclooligomerizations: Reactions from Metal Complexes. 104 Tetraphosphacubane 64 2.5.5 Addendum 105 2.4.2 Cycloaddition Reactions 64 2.6 References 107 2.4.2.1 [2+l]Cycloaddition 64 a) Carbenes 64 3. Phosphorus Nitride and Polyphos- b) Silylenes and Germylenes 67 phorus Units c) Phosphinidenes 67 (by O. J. Scherer) 112 2.4.2.2 [2 + 2]Cycloaddition 67 2.4.2.3 [3 + 2]Cycloaddition 68 3 cr\A -P :P = N:, :P = P:, Px a) Diazo Compounds 68 b) Azides 72 c) Nitrile Ylides 73 3.1 Introduction 112 d) Nitrile Imines 74 3.2 Syntheses 112 e) Nitrile Oxides 74 3.3 Ligand Properties 112 f) Nitrile Sulfides 75 3.3.1 The PN Unit as Ligand in Complexes . 112 g) Mesoionic Compounds 75 3.3.2 The P; Unit as Ligand in Complexes . 112 h) Nitrones and Azomethinimines . 76 3.3.3 The P2 Unit as Ligand in Complexes . 113 i) Selenoxocarbenes 77 3.3.3.1 Complexes of the Tetrahedrane Type . 114 2.4.2.4 [4 + 2]Cycloaddition 77 3.3.3.2 Complexes of the Butterfly Type . 114 a) Cyclobutadienes 77 3.3.3.3 31P-NMR and X-Ray Data 114 b) Azetes 79 3.3.4 The P3 Unit as Ligand in Complexes . 117 c) l,3-As-Diphosphetes 80 3.3.4.1 Mononuclear Complexes with a d) Cyclopentadienones, Phosphole Cyclo-P3 Ligand 117 Sulfides, and a-Pyrones 80 3.3.4.2 Reactivity of the Cyclo-P3 Ligand . 117 Table of Contents XI 3.3.4.3 Dinuclear Complexes with 3.3.6 The Cyclo-P5 Unit as Ligand in Cyclo-P3 Ligands 119 Complexes 122 31 3.3.4.4 P-NMR and X-Ray Data 119 3.3.7 The Cyclo-P6 Unit as Ligand in 3.3.5 The P4 Unit as Ligand in Complexes 124 Complexes 119 3.4 Addendum 126 3.3.5.1 Two P2 Units 122 3.5 References 127 D. Phosphorus Compounds with ation Number 2 129 1. Phosphenium Cations 1.4.5 Reactions with Alkynes 139 (by M. Sanchez, M. R. Mazieres, 1.5 Coordination Chemistry 140 L. Lamande, and R. Wolf) 129 1.5.1 General Remarks 140 1.5.1.1 Metallophosphenium Ions 140 2 2 1.5.1.2 Phosphenium Ions as Ligands .... 141 a , A —P ^P: 1.5.2 Metallophosphenium Species 141 1.5.3 Phosphenium Cations as Two 1.1 Introduction 129 Electron Ligands 142 1.2 Syntheses 130 1.5.3.1 Preparation by Ligand Substitution . 142 1.2.1 From Halophosphines R2PX, RPX2 . 130 1.5.3.2 Preparation by Anionic 1.2.1.1 Phosphorus-Halogen Bond Abstraction in Complexes 143 Heterolysis 130 1.5.4 Crystal Structures by X-Ray 1.2.1.2 Condensation Reactions with Diffraction and 31P-NMR Trimethylsilyl Triflate . 131 Spectroscopy 144 1.2.2 Chlorophosphenium Cations 131 1.5.5 Chemical Properties 144 1.2.3 From Iminophosphincs 1.5.6 "Neutral Phosphenium Species" ... 145 R'-P= N-R2 131 1.6 References 146 1.3 Physical Properties 132 1.3.1 X-Ray Crystallography 132 2. 2-Phosphaallylic Cations 1.3.2 NMR Spectroscopy 132 (by A. Schmidpeter) 149 1.3.3 Theoretical Calculations 133 1.4 Chemical Properties 133 A2, A3-P X = P-X+ 1.4.1 Lewis Acidity 133 1.4.1.1 Reactions with Pyridine and Amines . 133 1.4.1.2 Reactions with Phosphines 134 2.1 Introduction 149 1.4.2 Insertion Reactions with C —H 2.2 Syntheses 150 and C —C Bonds 135 2.3 Spectral Properties 152 1.4.2.1 Oxidative Addition to a C —H Bond . 135 2.3.1 NMR Spectra 152 1.4.2.2 Insertion into a C —C Bond 136 2.3.2 UV/VIS Spectra 152 1.4.3 Reactions with Organic Species 2.4 Reactions 152 Possessing an X = N Bond 2.5 Structures 154 (X = N, C, P) 136 2.6 References 154 1.4.3.1 Reactions with Azides 136 1.4.3.2 Reactions with Amidines and 3. Phosphinylideneboranes and Isocyanidcs 137 Phosphinylideneborates a) Amidines 137 (by F. Bickelhaupt) 155 b) Isocyanides 137 1.4.3.3 Reactions with Iminophosphines: <T2,/L3-P —P= B —, -P= BC R1 —P = N —R2 137 1.4.4 Cycloadditions with Dienes and Cyclooctatetraene 138 3.1 Introduction 155 1.4.4.1 1,3-Dienes 138 3.2 Syntheses 155 1.4.4.2 1,4-Dienes 139 3.3 Structures 156 1.4.4.3 Cycloocta-1,5-diene and Cyclo- 3.4 Chemical Reactions 156 octatctraene 139 3.5 References 156 XII Table of Contents 4. Phosphaalkenes, Phosphacarba- 4.5.3.3 l,6-Diphosphahexa-l,5-Dienes by oligoenes, and Phosphaatlenes Cope Rearrangement from (by R. Appef) 157 3,4-Diphosphahexa-l,5-Dienes .... 177 4.5.3.4 Valence Isomerization of OF2A3-P -P=C(,-P=C=X=Y,-P=P-X=Y, 3,4-Diphospha-l,5-hexadiyne in to 3,4-Bis(phosphamethylene)- -P=C=E 1-cyclobutene 178 4.5.3.5 l,3-Diphosphahexa-l,5-Dienes .... 179 4.5.3.6 Monophosphahexadienes 179 4.1 Introduction and Historical a) Rearrangement of 3-Phos- Aspects 157 phahexa-l,5-Dienes to 1-Phos- 4.2 Formation of the P = C Double phahexa-l,5-Dienes 179 Bond 158 4.6 Cumulated Bond Systems with 4.2.1 By 1,2-Elimination 158 Participation of the P = C Double 4.2.2 By Condensation Reactions 158 Bond 181 4.2.3 By 1,3-Trimethylsilyl Migration ..