Studies of the Hydrides of the Heavier Group 14 Elements
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Studies of the Hydrides of the Heavier Group 14 Elements Daniel Hugh Brown A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the University of Edinburgh 1998 Declaration This thesis has been composed by myself and it has not been submitted in any previous application for a degree. The work reported within was executed by myself, unless otherwise stated. May 1998 1 Abstract The chemistry of some simple tin hydrides (CH3)4_ SnH (x = 1-4) has been investigated with particular reference to their reactivity towards the reagents NaH, KH, alkyl lithium compounds, and the ylids Me 3P C H2 and Ph3PCH2 . It has been found that the reaction between the stannanes and alkali metal hydrides or the ylids produces salts containing the respective stannyl anions, [Sn(CHa)sH] (x = 0-3). These salts have been characterised by low tem- perature infrared spectroscopy, the results of which are in good agreement with the results of ab initio calculations. In contrast, reactions involving alkyl lithium compounds proceed by transmetallation with elimination of LiH and alkylation of the tin centre. The technique of in situ crystal growth at low temperatures has been used to obtain X-ray crystal structures of Me 3P C H2 , Me2Sn H2 and Me3Sn H. The structure of the ylid in the solid phase has been shown to resemble the calculated structure of a transition state involving rotation of the CH 2 group about the P-C aids. The reaction between monochlorostannane and sodium metal produced small quantities of Sn 2H6, detected by mass spectrometry. Attempts to increase the scale of this preparation were unsuccessful. Gas phase electron diffraction data were recorded for monochlorostannane but subsequent refinement showed that some decomposition of the sample had occurred giving rise to SnH 2C12 . The structure of Me3PbH was investigated by powder neutron diffraction and gas phase electron diffraction. Rietveld refinement of the neutron diffraction data based on an extant single crystal structure of Me3PbH was unsuccessful owing to inconsistencies between the two data sets, most probably stemming from the different temperatures at which they were collected. The gas phase experiment was partially successful, but data collected at the short camera distance, and crucial to an accurate structural determination, could not reasonably be refined in conjunction with that collected at the long camera distance. No reliable gas phase structure of Me3 PbH has yet been determined. To Mum and Dad Acknowledgments I should like to thank the following for their contributions to this thesis, and all that lead up to it, My supervisor, Dr. Cohn Pulham, for his advice, wisdom, and willingness to let me follow my own route through the wilds of this doctorate. Professor David Rice and Dr. Elizabeth Page for their hospitality in Reading. Drs. Bruce Smart, Paul Brain, and Simon Parsons for their patient guidance through the worlds of ab initio calculation, electron diffraction, and X-ray crys- tallography. Members past and present of the Pulham and Rankin groups, for being there, just in case. This thesis was written and typeset using J5frjC2e on an Acorn RiscPC running NetBSD 1.2, RiscOS 3.7, and Windows 3.11. Notes 1 Torr = lmmHg = 133.3 Pa 1 atmosphere = 101325 Pa 1 Hartree, EH 4.36 x 10_ 11 J The following abbreviations are used in the text: Me: Methyl, -CH3 Et: Ethyl, -CH2CH3 Pr: Isopropyl, —CH(CH 3)2 Bu: Butyl, -CH2CH2CH2CFI3 Ph: Phenyl, -C6H5 Bz: Benzyl, -CFI 2C6H5 TMEDA: Tetramethylethylenediamine, (Me2NCH2)2 PMDETA: Pentamethyltriethylenediamine, (Me 2NCH2CH2)2NMe 2,2,2-crypt: The cryptand, N(CH2CH2NHCH2CH 2NHCH2CH2)3N NMR: Nuclear Magnetic Resonance ESR: Electron Spin Resonance GED: Gas-phase Electron Diffraction NMR data are expressed in accordance with the chemical shift convention out- lined by IUPAC, i.e. a positive chemical shift denotes a positive frequency and vice versa with respect to the designated reference substance, 1 H, 13C NMR spectra referenced to tetramethylsilane 31 p NMR spectra referenced to 85% H 3PO4 "9Sn NMR spectra referenced to Me 4Sn The following abbreviations are used in the tabulation of spectra 5: strong, m: medium, w: weak, v: very, br: broad. sh: shoulder, ii: stretching mode, 5: deformation mode, p: rocking mode. Contents 1 Introduction 1 1.1. Stannanes ...............................1 1.2 The Methyistannanes .........................3 1.3 Stannylmetallic Compounds .....................4 1.4 The Methyiplumbanes ........................5 1.5 Aims of the Present Research ....................7 2 Experimental Techniques 8 2.1 The Manipulation of Air Sensitive and Temperature Sensitive Com- pounds ................................. 8 2.2 Analytical and Theoretical Techniques . . . . 12 2.2.1 Infra-red Spectroscopy .................... 12 2.2.2 Ultra-violet/Visible Spectroscopy .............. 12 2.2.3 Nuclear Magnetic Resonance Measurements ........ 15 2.2.4 Mass Spectrometry ...................... 15 2.2.5 Theoretical Calculations ................... 15 2.3 The Preparation and Purification of Essential Reagents and Solvents 16 3 The Synthesis and Characterisation of Organostannyl Anions 21 3.1 Introduction ..............................21 3.2 The Reaction between Stannane and NH 3 .............23 3.2.1 Experimental .........................23 3.2.2 Interpretation .........................24 3.3 The Reaction between Stannane and the Alkali Metal Hydrides. 24 3.3.1 Stannane and Sodium Hydride . 24 1 CONTENTS 11 3.3.2 Stannane and Potassium Hydride . . . . . . . 25 3.4 The Reaction between Stannanes and Alkyl Lithium Reagents. 27 3.4.1 Introduction .......................... 27 3.4.2 The Reactions between Me 2 SnH2 or Me3SnH and Alkyl Lithium Reagents ....................... 28 3.4.3 The Reaction between Methyistannane and Alkyl Lithium Reagents ............................ 30 3.4.4 The Reaction between Stannane and Alkyl Lithium Reagents 31 3.5 The Reaction between Stannanes and Phosphorus Ylids ...... 33 3.5.1 Introduction .......................... 33 3.5.2 Low Temperature Infra-red Studies ............. 34 3.5.3 The Reaction between Stannanes and Me 3PCH2 in Solution 52 3.5.4 The Reaction between Stannanes and Triphenyiphospho- nium Methylid ........................ 63 3.6 Summary and Suggestions for Further Work ............ 68 4 The Chemistry of Monochlorostannane 69 4.1 Introduction .............................. 69 4.1.1 Preparation ......................... 69 4.1.2 Structural Characterisation ................. 70 4.1.3 SnH31 in solution . . . . . . . . . . . . . . . . . . . . . . 72 4.1.4 Aims of the Present Research ................ 73 4.2 The Chemistry of Monochlorostannane ............... 73 4.2.1 Synthesis ........................... 73 4.2.2 The Synthesis of Distannane, Sn2H5 ............. 74 4.3 The Structure of SnH3C1 as Determined by Gas Phase Electron Diffraction ............................... 84 4.3.1 Introduction .......................... 84 4.3.2 Experimental ......................... 84 4.3.3 Structure Refinement ..................... 85 4.4 Summary ............................... 91 CONTENTS iii 5 Crystal Structures of Low Melting Compounds 92 5.1 Introduction .............................. 92 5.2 Experimental ............................. 93 5.2.1 The Growth of Single Crystals at the Diffractometer. . 93 5.3 The Solid State Structures of Me 2SnH2 and Me3SnH........ 96 5.3.1 Me2SnH2 ............................ 96 5.3.2 Me3SnH ............................ 99 5.4 The Solid State Structure of Me3PCH2 ................ 102 5.4.1 Introduction .......................... 102 5.4.2 Results and Discussion .................... 102 6 The Structure of Trimethyllead Hydride 110 6.1 Introduction .............................. 110 6.2 Experimental Techniques ....................... 110 6.2.1 Synthesis of Trimethyllead Hydride ............. 110 6.2.2 Synthesis of (CD3 ) 3 PbD ................... 112 6.2.3 Powder Neutron Diffraction at ISIS ............. 112 6.3 The Structure of Me3PbH by Neutron Powder Diffraction ..... 119 6.3.1 Structure Refinement ..................... 119 6.3.2 Refinement using an Unrestrained Model .......... 119 6.3.3 Refinement using a Constrained Model ........... 125 6.3.4 Refinement using the Difference Fourier Method . . 135 6.3.5 Summary, and Suggestions for Further Work . . 140 6.4 The Gas Phase Structure of Me 3PbH . . 141 6.4.1 Experimental ......................... 141 6.4.2 Data Analysis ......................... 144 A Crystal Structure Refinements 147 A.1 Trimethylphosphonium methylid ................... 147 A.2 Dimethylstannane ........................... 151 A.3 Thmethylstannane .......................... 155 A.4 Me3PbH ................................ 158 References 161 List of Figures 2.1 A High Vacuum line for the Handling of Air Sensitive, and Tem- perature Sensitive Compounds . 10 2.2 Young's Tap Ampoules for High Vacuum Line Manipulations 11 2.3 Apparatus for Low Temperature IR Spectroscopy .........13 2.4 Apparatus for Low Temperature UV/Visible Spectroscopy . 14 3.1 Infra-red Spectra of Me 3PCH2 and Me4PBr ............ 35 3.2 Infra-red Spectra of SnH4 and Me3PCH2 in situ .......... 37 3.3 Infra-red Spectra of SnD 4 and Me3PCH2 in situ .......... 39 3.4 Infra-red Spectra of MeSnH 3 and Me 3PCH 2 in situ ........ 43 3.5 Infra-red Spectra of Me 2SnH 2 and Me 3PCH 2 in situ ....... 46 3.6 Infra-red Spectra of Me 3SnH and Me 3PCH 2 in situ ....... 48 3.7 The hlI NMR Spectrum of a Solution of Me 3PCH2 and Me3SnH•.