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Structural and Kinetic Study of Rhodium Complexes of N-Aryl-N-Nitrosohydroxylamines and Related Complexes

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Structural and Kinetic Study of Rhodium Complexes of N-Aryl-N-Nitrosohydroxylamines and Related Complexes Structural and kinetic study of rhodium complexes of N-aryl-N-nitrosohydroxylamines and related complexes J.A. Venter Structural and kinetic study of rhodium complexes of N-aryl-N-nitrosohydroxylamines and related complexes A thesis submitted to meet the requirements for the degree of Philosophiae Doctor in the Department of Chemistry Faculty of Natural and Agricultural Sciences at the University of the Free State by Johan Andries Venter Promotor Prof. S.S. Basson Co-promotor Prof. W. Purcell December 2006 2 Voorwoord Hiermee wens ek my opregte dank en waardering uit te spreek teenoor Prof Steve Basson vir sy bekwame leiding met beide my M.Sc. en Ph.D. studies. Behalwe vir sy wye kennis van die vak het ek bewondering vir die aangename gesindheid waarmee hy met sy personeel en studente omgaan. Hy was altyd bereid om tyd vir my in te ruim, soos ook nou met die finalisering van hierdie tesis gedurende sy verloftyd. Sy invloed op my ontwikkeling reik so ver terug as die tyd toe ek as eerstejaarstudent in sy klas gesit het. Groot dank ook aan Walter Purcell, my medepromotor, vir sy insette en ondersteuning wat ook verder as Chemie strek. André Roodt het ’n belangrike bydrae, veral tot die kristallografiese ondersoeke gelewer waarvoor ek groot waardering het. Ander personeel by die Departement Chemie het ook op verskillende maniere ’n bydrae gelewer waarvoor ek my dank uitspreek. Veral Alet van Rooyen, Jeanet Conradie, Ina du Plessis en Michael Coetzee verdien vermelding. ’n Spesiale woord van dank aan my gesin, ouers, skoonouers, broer en suster vir hulle liefde, begrip, opoffering, aanmoediging en ondersteuning gedurende my studiejare. Ek waardeer dit baie, ook hulle insette met hierdie tesis. In besonder wil ek my ouers wat met hul opvoeding sedert my kinderjare die grondslag gelê het, asook Elizabeth, Gerhard en Ilse wat van ons huis ’n lewensoase maak en veral die laaste ruk baie moes opoffer, grootliks bedank. Pappa is klaar met die boek! Met erkenning aan Koos du Plessis moet ek ook sê “wat ek is, is net genade, wat ek het is net geleen”. Die Here het voorsien. Aan Hom al die eer. Front page of a 1708 German alchemical work.1 The poem says: What would torches, light and glasses help while everyone is acting according to his own will, and struggle anxiously with the Chemistry, till his heart goes faint in his body. He struggles from one extreme to the other only to find nothing. And if he relies on all the glasses while acting according to his own will, that way he will not find the truth and be pleased. Have faith and read it with intellect and do not fumble blindly towards the wall. Use torches, light and glasses the right way and God will fulfil your wishes. 1 Jackson, R., The alchemists, Weidenfeld & Nicolson, London (1997). 2 Contents List of abbreviations………………………………………………………………v 1. Introduction 1.1 Strategic rhodium and the historical development of organometallic chemistry ....................................................................................................... 1 1.2 Background and aim of this study ............................................................... 12 2. Fundamental aspects 2.1 Prominent ligands and their bonding characteristics ................................... 17 2.1.1 Introduction .......................................................................................... 17 2.1.2 The carbonyl ligand .............................................................................. 18 2.1.3 Trivalent phosphorous ligands ............................................................. 21 2.1.3.1 Electronic and steric involvement of phosphorous ligands ............... 29 2.1.3.2 Electronic effects .............................................................................. 30 2.1.3.3 Steric effects ..................................................................................... 32 2.1.3.4 Separation of steric and electronic effects ........................................ 36 2.1.4 Cis- and trans-influence of coordinated ligands ................................... 39 2.1.5 Trans-influence of bidentate ligands .................................................... 43 2.2 Important reactions ..................................................................................... 46 2.2.1 Oxidative addition reactions ................................................................. 46 2.2.1.1 Introduction....................................................................................... 46 2.2.1.2 Requirements for oxidative addition, ................................................. 47 2.2.1.3 Stereochemistry of oxidative addition ............................................... 49 2.2.1.4 Mechanisms of oxidative addition ..................................................... 52 2.2.1.5 Factors influencing oxidative addition ............................................... 67 2.2.2 Insertion reactions ................................................................................ 87 2.2.2.1 Introduction....................................................................................... 87 2.2.2.2 Carbonyl insertion reactions ............................................................. 88 Contents 2.2.2.3 The mechanism of carbonyl insertion reactions ............................... 90 2.2.2.4 Factors that influence the rate of carbonyl insertion reactions ......... 94 3. Synthesis of complexes 3.1 Introduction ............................................................................................... 103 3.2 Synthesis of the complexes ...................................................................... 104 3.2.1 The acac complexes .......................................................................... 104 3.2.1.1 Synthesis of [Rh(acac)(CO)(PX3)] .................................................. 104 3.2.1.2 Synthesis of [Rh(acac)(CO)(CH3)(I)(PX3)] ...................................... 105 3.2.2 The cupferrate and neocupferrate complexes ................................... 106 3.2.2.1 Synthesis of [Rh(cupf)(CO)(PPh3)] and [Rh(neocupf)(CO)(PX3)] ... 106 3.2.2.2 Synthesis of [Rh(cupf)(CO)(CH3)(I)(PX3)] and [Rh(neocupf)(CO)(CH3)(I)(PPh3)] ................................................... 106 3.2.2.3 Synthesis of [Rh(cupf)(CO){P(OCH2)3CCH3}] ................................. 107 3.2.3 The Sacac complexes ........................................................................ 108 3.2.3.1 Synthesis of [Rh(Sacac)(CO)2] ....................................................... 108 3.2.3.2 Synthesis of [Rh(Sacac)(CO)(PPh3)] .............................................. 108 4. X-ray crystallography 4.1 Introduction ............................................................................................... 109 4.2 Experimental ............................................................................................. 113 4.2.1 Preparation of crystals of [Rh(cupf)(CO)(CH3)(I)(PPh3)] .................... 114 4.2.2 Preparation of crystals of [Rh(cupf)(CO)(PPh3)2] ............................... 114 4.2.3 Preparation of crystals of [Rh(neocupf)(CO)(PPh3)]·CH3COCH3 ....... 115 4.2.4 Preparation of crystals of [Rh(neocupf)(CO)(CH3)(I)(PPh3)]·C5H12 .... 115 4.2.5 Preparation of crystals of [Rh(cupf)(CO){P(OCH2)3CCH3}] ................ 116 4.2.6 Preparation of crystals of [Rh(cupf)(COCH3)(I){P(OCH2)3CCH3}]2 ..... 116 4.2.7 Preparation of crystals of trans-[Rh(CO)(Cl)(PCy3)2 .......................... 117 4.3 Crystal structure determinations ............................................................... 117 4.3.1 Crystal structure of [Rh(cupf)(CO)(CH3)(I)(PPh3)] .............................. 117 4.3.2 Crystal structure of [Rh(cupf)(CO)(PPh3)2] ......................................... 120 4.3.3 Crystal structure of [Rh(neocupf)(CO)(PPh3)]·CH3COCH3 ................ 123 ii Contents 4.3.4 Crystal structure of [Rh(neocupf)(CO)(CH3)(I)(PPh3)]·C5H12 ............. 126 4.3.5 Crystal structure of [Rh(cupf)(CO){P(OCH2)3CCH3}] .......................... 130 4.3.6 Crystal structure of [Rh(cupf)(COCH3)(I){P(OCH2)3CCH3}]2 .............. 132 4.3.7 Crystal structure of trans-[Rh(CO)(Cl)(PCy3)2] ................................... 136 4.4 Discussion ................................................................................................. 139 4.4.1 The cupferrate and neocupferrate structures ..................................... 139 4.4.1.1 The square planar coordination sphere .......................................... 139 4.4.1.2 The octahedral coordination sphere ............................................... 141 4.4.1.3 The trigonal bipyramidal coordination sphere ................................. 146 4.4.1.4 The phosphorous ligand ................................................................. 147 4.4.1.5 The chelate ring .............................................................................. 153 4.4.1.6 The carbonyl ligand ........................................................................ 155 4.4.1.7 The iodide ligand ............................................................................ 157 4.4.1.8 The methyl ligand ........................................................................... 157 4.4.1.9 The acyl ligand. .............................................................................. 158 4.4.1.10 Interactions ..................................................................................... 160 4.4.2 The structure of trans-[Rh(CO)(Cl)(PCy3)2] ........................................ 161 5. Reaction kinetics 5.1 Introduction ..............................................................................................
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