This document is downloaded from DR‑NTU (https://dr.ntu.edu.sg) Nanyang Technological University, Singapore. Aryl‑NHC group 13 trimethyl complexes : structural, stability and bonding insights Wu, Melissa Meiyi 2017 Wu, M. M. (2017). Aryl‑NHC group 13 trimethyl complexes : structural, stability and bonding insights. Doctoral thesis, Nanyang Technological University, Singapore. http://hdl.handle.net/10356/70204 https://doi.org/10.32657/10356/70204 Downloaded on 28 Sep 2021 13:14:06 SGT ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library. NANYANG TECHNOLOGICAL UNIVERSITY DIVISION OF CHEMISTRY AND BIOLOGICAL CHEMISTRY SCHOOL OF PHYSICAL & MATHEMATICAL SCIENCES Aryl-NHC Group 13 Trimethyl Complexes: Structural, Stability and Bonding Insights Wu Meiyi Melissa G1102527F Supervisor: Asst Prof Felipe Garcia Contents Acknowledgements .............................................................................................................. iv Abbreviations ....................................................................................................................... v Abstract.............................................................................................................................. viii 1. Introduction 1.1. N-Heterocyclic Carbenes (NHC) ................................................................................. 1 1.1.1. Electronic Properties ............................................................................................ 1 1.1.2. Steric Properties ................................................................................................. 4 1.2. Group 13 Elements .................................................................................................... 6 1.3. Group 13 Metal Carbene Complexes ......................................................................... 6 1.3.1. Aluminium Carbene Complexes 1.3.1a AlH3•NHC ..................................................................................................... 7 1.3.1b AlMe3•NHC ................................................................................................... 9 1.3.1c AlR3•NHC ................................................................................................... 12 1.3.1d AlX3•NHC ................................................................................................... 15 1.3.1e AlXnH3-n•NHC (n = 1 or 2) ............................................................................ 15 1.3.1f Chelating NHC Al Complexes ...................................................................... 17 1.3.1. Gallium Carbene Complexes 1.3.1a GaH3•NHC, GaXnH3-n•NHC (n = 1 or 2) and GaHnR3-n•NHC (n = 0, 1) ......... 20 1.3.1b GaMe3•NHC and GaXnMe3-n•NHC (n = 1) .................................................... 22 1.3.1c GaX3•NHC .................................................................................................. 23 1.3.1d Chelating NHC Ga Complexes ................................................................... 28 1.3.1. Indium Carbene Complexes 1.3.1a InH3•NHC, InXnH3-n•NHC (n = 1 or 2) ........................................................... 29 1.3.1b InXnMe3-n•NHC (n = 1 or 2) .......................................................................... 30 1.3.1c InX3•NHC and Chelating NHC In halide complexes .................................... 31 1.3.1. Thallium Carbene Complexes .......................................................................... 37 2. Trimethylaluminium NHC Species Summary ........................................................................................................................ 38 2.1. Introduction .............................................................................................................. 39 2.2. Results and Discussion 2.2.1. Synthesis of Trimethylaluminium Complexes .................................................... 40 2.2.2. Spectroscopic Studies of Trimethylaluminium Complexes ................................ 41 2.2.3. Crystallographic Studies of Trimethylaluminium Complexes ............................. 42 2.2.4. Lewis acid-base Properties of Trimethylaluminium Complexes ........................ 44 2.2.5. Stability Studies of Trimethylaluminium Complexes .......................................... 46 i 2.2.6. By-product obtained from SIPr•AlMe3 (125) ...................................................... 52 2.2.7. Reactivity Studies on Complexes ..................................................................... 53 2.3. Conclusions ............................................................................................................. 60 3. Trimethylgallium and Indium NHC Species Summary ........................................................................................................................ 61 3.1. Introduction .............................................................................................................. 62 3.2. Results and Discussion 3.2.1. Synthesis of Trimethylgallium and Indium complexes ....................................... 63 3.2.2. Spectroscopic Studies of Trimethylgallium and Indium complexes ................... 64 3.2.3. Crystallographic studies of Trimethylgallium and Indium complexes ................. 64 3.2.4. Lewis acid-base properties of Trimethylgallium and Indium complexes ............ 68 3.2.5. Stability Studies of Trimethylgallium and Indium complexes ............................. 70 3.2.6. Bonding Studies of NHCs Group 13 Complexes ............................................... 73 3.2.7. By-product obtained from SIPr•InMe3 (152) ....................................................... 77 3.3. Conclusions ............................................................................................................. 79 4. Mechanochemical Methodologies in NHC Main Group Complexes Summary ........................................................................................................................ 80 4.1. Introduction .............................................................................................................. 81 4.2. Results and Discussion 4.2.1. Attempted solvent-based synthesis of Group 13 complexes ............................. 83 4.2.2. Mechanochemical synthesis of Group 13 complexes ....................................... 85 4.2.3. Spectroscopic studies of mechanochemical synthesized complexes ................ 86 4.2.4. Crystallographic studies of mechanochemical synthesized complexes ............. 87 4.3. Reversible reaction being observed through mechanochemical synthesis ............... 89 4.4. Synthesis of chelating Group 13 complexes utilising mechanochemistry ................. 90 4.5. Conclusions ............................................................................................................. 92 5. Experimental Section 5.1. Inert Atmosphere Techniques ................................................................................... 93 5.1.1. Vacuum and Schlenk Line ................................................................................. 93 5.1.2. Glovebox ........................................................................................................... 93 5.1.3. Starting Material and Solvent ............................................................................ 94 5.2. Analytical Instruments and Procedures ..................................................................... 94 5.2.1. NMR Spectroscopy ........................................................................................... 94 5.2.2. Melting Point Determination .............................................................................. 95 5.2.3. Infrared Spectroscopy ....................................................................................... 95 5.2.4. High-Resolution Mass Spectroscopy ................................................................. 95 ii 5.2.5. Single Crystal X-ray Diffraction Studies ............................................................. 95 5.3. Preparation of Starting Materials .............................................................................. 97 5.4. Synthesis of New Compounds 5.4.1. Synthesis of New Trimethylaluminium Compounds ......................................... 102 5.4.2. Synthesis of Trimethylaluminium By-products ................................................. 106 5.4.3. Synthesis of New Trimethylgallium Compounds .............................................. 111 5.4.4. Synthesis of New Trimethylindium Compounds .............................................. 115 5.4.5. Synthesis of Trimethylindium By-product ......................................................... 119 5.5. Mechanochemical Synthesis of Compounds 5.5.1. Synthesis of IMes→MCl3 .................................................................................. 121 5.5.2. Synthesis of Bidentate Ligands for Mechanochemical Synthesis .................... 124 6. References.................................................................................................................. 126 7. Appendices Appendix 1 %VBur and Topographic Steric Maps ........................................................ 132 Appendix 2 Solid State Structures for New Compounds ............................................. 140 Appendix 3 Structures of Labelled Compounds .......................................................... 148 iii Acknowledgements First and foremost, I will like to thank my boss, Dr Felipe García, for his relentless