Steric and Electronic Contrd of Low-Coordinate Pnictogen Bonding Charles L-B- Macdonald Submitîed in partial fiiifilnieut of the requirements for the degree of Doctor of Philosophy Dalhousie University Halifax, Nova Scotia May 1998 8 Copyright by Charles L.B. Macdonald, 1998 -Libtary Biimtheque nationale du Canada Acquûitions and Acquisitions et wogfapk Services services bibliographiques The author has granted a non- L'auteur a accordé une licence non exclusive licence aIlowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, Loan, distribide or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forne de microfiche/nIm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright m this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fkom it Ni la thèse ni des extraits substantieIs may be printed or otherwise de celle-ci ne doivent être hprimés reproduced -out the author's ou autrement reproduits sans son permission. autorisation. Canada For Mom and Dad Table of Contents Tableofcontents .............................................. v List of Figures ................................................. ix List of Tables ................................................ xv List of Abbreviatioas and Symbols .................................. xix Acknowledgements ............................................ xxii Chapter 1 . Introduction to the Thesis............................... 1 1.1 Generd Introduction ................................. 1 1.2 Group 15 Elernents ."'Mctogens" ........................ 2 1.2.1 Generai Properties .............................. 2 1.2.2 Characterization of Compounds ..................... 3 1.2.3 OxidationStates ............................... 4 1.2.4 BondinginGrouplS ............................ 5 1.3 LowCoordinaîe and Electron Deficient Booding Environments ..... 5 1.4 Stericdy Dernanding Substituents ........................ 6 1.5 Thesis Overview .................................... 15 Chapter 2. Pnictogenium Cations 0:The Synthetic and Theoreticai Examination of the Structure and Bonding of Phosphenium and Arsenium Cations ................................... 17 2.1 Introduction ....................................... 17 2.2 Ctdorodiazarsenane and Diazamnanium Tetmchlorogallate ........ 19 2.3 Theoretical Assesment of Phosphenium and Arsenium Cations ..... 25 2.3.1 Introduction .................................. 25 2.3.2 Theoretid Methods and Results .................... 26 2.3.3 Muitiplicity of the Ground State for Diazaphosphenium and Diazaarsenium cations ........................... 27 2.3-4 Dimerization of Pnictogenium Cations ................. 35 2.4 Conclusions ....................................... 40 Chapter 3 . Riictogeniurn Cations 0:Synthetic and Theoretical Investigation of the Unprecedenwl Arsenium Cycloaddition Reactivity ......... 41 3.1 Introduction ....................................... 41 3.2 Diazarsenium-Butadiene Cycloaddition ..................... 42 3.3 Theoretical Assessment of Pnictogenium-Buradiene Cycloaddition Reactions ......................................... 47 3.4 Conclusions ....................................... 54 Chapter 4. Evaluation of the 2A6-Tris(trifluoromethyl)phenylas a Stabilizing Ligand for Riictogenium Cations ......................... 55 4.1 Introduction ....................................... 55 4.2 FmeszPnCl Derivatives ................................ 65 4.3 Fmesp] Derivatives . 73 4.4 Conclusions . 77 Chapter 5. Steric Control of Low Coordinate Bonding Environments (I): The Steric Sade for Iminoarninopnictines, Diaminopnictazanes and Trisaminopnictines . .. 80 5.1 Introduction . 80 5.2 Synthesis and structure of Pn(N(H)Mes*):, (Pn = Sb and Bi) and 5.3 Structure Defined by Stenc Strain for [N-Ri-NI Species . 85 5-4 Conclusions . 90 Chapter 6. Steric Control of Law Coordinate Bonding Envimnments (II): Investigations of the Iminophosphme-Diazadiphosphetidine DirneRzation and the Observation of 'Won-Le Chateliei' Behaviour Introduction . Synthesis and Structures of Iminophosphines and Diazadiphosphetidines . 93 Vibrational Spectra of hinophosphines and Diazadiphosphetidines . Variable-Temperature Solution NMR of Mixtures of 6.3 and 6.4 . Solidatate 31~NMR of Mixtures of 6.3 and 6.4 . Interpretation of Obsentations - Steric Inhibition of Le Chatelier's Principle? ....................................... Conclusions ...................................... Chapter 7. The Nascent Chernistry of the m*N=As] Moiety ............ 1 18 7.1 Introduction ...................................... 118 7.1.1 DiazoniumCations ............................ 118 7.1 -2 Phosphazonium Cation and Phosphaallcynes ........... 121 7.1.3 Heavier Isovalent Analogues ...................... 125 7.1 .4 Mass Spectrometric Identification of m*N=Eh] ....... 126 7.2 Synthesis of Potential Imlnoarsine Precurson ................ 128 7.2.1 Mes*N(TMS)PnC$ (Pn = P. As . Sb) ................ 128 7.2.2 Mes*N(H)AsCl, .............................. 134 7.3 Mes*N=As€l .................................... 135 7.4 Synmetic Utility of Mes*N(TMS)Asq ................... 138 7.5 Conclusions ...................................... 147 Chapter 8 . Experimental Rocedures .............................. 150 8.1 The Handling of Air Sensitive Reagents .................... 150 8.2 GeneraI Procedures ................................. 153 8.3 Recrystallization Methods ............................. 155 8.4 Specific Procedures ................................. 156 Endnotes (References) ......................................... 195 Appendix A. Ab Inilio Calculation Data. ............................. 231 List of Figares Figure 1.1. Figure 1.2. Schernatic reaction energy diagram........................ 10 Figure 1.3. Qualitative reaction energy diagrams as a fiinction of substituent size ............................................. 12 Figure 1.4. Reaction of diselenides with iodine........................ 13 Figure 2.1. Preparation of pnictogenium cation by halide abstraction .......... 19 Figure 2.2. Molecular structure of 2.5C1. ........................... 21 Molecular stmcture of 2.6C1. ........................... 21 Figure 2.4. Molecular structure of 2.6[GaC14]. ....................... 22 Figure 2.5. Figure 2.6. Cornparison of experimental (left) and theoretical (right) structures. ~ondlengths in A. and angles in degrees .................... 29 Figure 2.7. Plots of energy versus N-Ri-N angle for wyclic pnictogenium cations 6N.Ri.NH.J ................................ 32 Figure 2.8. Cyclo-dimerization reaction of multiply-bonded compounds ........ 36 Figure 3.1. Molecular structure of 3.2BD[GaCI J ...................... 44 Figure 3.2. ('H. i3~)COSY spectrurn of 3.3BD[GaC14] ................. 44 Figure 3.3. Qualitative frontier MO analysis for a pnictogenium cation and cis- 13.butadiene ....................................... 47 Figure 3.4. Cornparison of experimental and theoretical structural parameters for 3-2BD and3.8'. ................................... 49 Figure 3.5 . Schematic representation of the cycloaddition reaction energies (kJ/mol) for the reaction of pnictogenium cation with mm-1. 3. butadiene ......................................... 49 Figure 3.6 . Qualitative depiction of calculated molecular orbitals in 3-1' and 3.2'. Energy spacings and orbital sizes are not to scale.......... 51 Figure 3.7. Pnictogenium LUMO .butadiene HOMO cheletropic interaction..... 53 Figure 3.8. PRictogenium LUMO .butadiene HOMO Diels-Alder interaction.... 53 Figure 4.1. Synthesis of FMesLi .................................. 57 Figure 4.2. Drawing of Li] coordination in FmesLieOEt,. ................. 58 Figure 4.3. Synthesis of ligands containing Fms....................... 59 Figure 4.4. Synthesis of Fmes,E .................................. 60 Figure 4.5. Synthesis of cornpounds containing the [Fmes-Ri] fragment ....... 62 Figure 4.6. Synthesis of FmeszPnOTf compounds...................... 64 Figure 4.7. Molecuiar structtm of Fmes2AsCl......................... 67 Figure 4.8. Molecular structure of Fmes,SbCI. ......................... 67 Figure 4.9. IR spectra of Fmes2PnCl compounds. Top: Pn = P; Middle. Pn= As; Bottom. Pn = Sb .................................. 71 Figure 4.10. Raman spectra of Fmes,h Ci compounds. Top: Pn = P; Middle. Pn= As; Bottom. Pn = Sb.............................. 72 Figure 4.1 1 . Molecular structure of Fmes2SbOTf........................ 75 Figure 5.1. Molecdar structure of Sb[N(H)Mes*I3..................... 82 Figure 5.2. Molecular structure of pipN(H)SbNDip], ................... 83 Figure 5.3. Schematic representation of the steric control of N-Ri-N bonding .... 89 Figure 6.1. Molecuiar structure of Mes*N=P.OTf ...................... 95 Figure 6.2. Molecular structure of [Mes*N=P.OTfl, .................... 96 Figure 6.3. Packing diagram of wes*N=P.OTfl, ..................... 96 Figure 6.4. Molecuiar structure of [DipN=P.C1I2 ....................... 99 Figure 6.5. Molenilar structure of pipN=P.OTfl, ..................... 103 Figure 6.6. Molecular structure of CLP(pNDip),P.OTf ................. 104 Figure 6.7. Molecular structure of D~PN(PC$)~-...................... 105 Figure 6.8. Solid-state 3L~CP/MAS NMR spectrum of the crystallization mixture of 6.3 and 6.4. .............................. 108 Figure 6.9. The eqdibrium of A and