Paul Ashley Lummis
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Earth-Abundant Transition Metal Hydride Complexes for Dehydrocoupling and Hydrosilylation Catalysis by Paul Ashley Lummis A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Chemistry University of Alberta © Paul Ashley Lummis, 2015 Abstract The work described within this thesis details explorations into the realm of transition metal hydride chemistry, in particular for compounds of zirconium and zinc, plus additional ligand design and synthesis. Chapter 2 features complexes of zirconium bearing sterically hindered bis(amido)silyl ligands, and the functionalisation thereof. In addition, some of the challenges associated with these complexes are described, in particular the installation of these ligands onto Zr, and the functionalisation of the Zr following ligand binding. Additionally, the catalytic activity of these complexes towards dehydrocoupling of amine-boranes is investigated. Chapter 3 details the synthesis of a new bis(amido)silyl “umbrella” ligand precursor, and the utlisation of 1,1,3,3-tetramethylguanidine towards new bis(imine) ligands tethered by silyl, disilyl and disiloxane linkeages. Chapter 4 we covers the preparation of neutral and cationic zinc hydride adducts bearing N-hetercyclic carbene ligands, and their use in the catalytic hydrosilylation and hydroboration of ketones. In chapter 5 the ability of these compounds to be utilised as single-source precursors for materials chemistry is described, as well as the design of compounds towards the synthesis of an elusive zinc carbonyl complex. ii Dedicated to the memory of Kenneth Finch and Harald Neumann “Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire world, and all there ever will be to know and understand.” - Albert Einstein iii Acknowledgements First of all, I must thank my advisor Professor Eric Rivard for all of his help and support since he graciously allowed me to join his research group. I benefitted immensely from his guidance, and very much appreciated the fact that he allowed me as much creative freedom as was possible and never once said that I had asked a stupid question, despite proffering many. It was a long and rewarding journey, during which I have grown immensely as a person, a chemist, and perhaps most importantly, as a glove-box/solvent purification system technician. I would also like to thank Prof. Steven Bergens, Prof. Frederick West, Prof. Jon Veinot, Prof. Rylan Lundgren, Prof. Frédéric- Georges Fontaine and Prof. John Davis for serving on my supervisory/examination committee, and for always forcing me to work harder, and to think outside of the box. I would be remiss also to not thank Dr. Terry Kee at the University of Leeds, who advised my earlier studies and began the process of making me a chemist of at least somewhat reasonable ability. Next, I must thank my amazing wife Erika, without whom this entire process would not have been possible. Simple words cannot express how grateful I am that you have been by my side during these past five years, and I look forward to an exciting future together; I even promise to (try to) get a “real” job soon! In addition to Erika, I am grateful for the support of my family; my brother Ian, Parents Julia and Eric, and grandparents Edith & Kenneth, and Eric Sr. I would also like to thank my mother and father in law, Sigrid and Harry Neumann who welcomed me warmly into their family, and into their home upon my initial move from England to Canada, as well as the iv extended Neumann, Knox and Wrona families for the warm welcome to your country and your family. None of what follows would not have been possible without the amazing staff at the University of Alberta, and to them I offer my sincere thanks, in particular to Dr. Bob McDonald, Dr. Michael Ferguson, Dr. Jason Cooke, Ryan Lewis, Mark Miskolzie, Nupar Dabral, Wayne Moffat, Prof. Alex Brown, the wonderful staff of the machine, electronic and glass shops, and to everybody else that has made my stay so enjoyable. I must also thank all the previous members of the Rivard lab (in somewhat chronological order); Dr. Ibrahim Al-Rafia, Adam Malcolm, Le Kang, Kelsey Deutsch, Kyle Sabourin, William Ramsay, Marcel Schreier, Christopher Berger, James Goettel, Jason Brandt, Leah Miedema, Sean Liew, Sean MacDonald, Dr. Gang He, Alyona Shynkaruk, William Torres Delgardo, Melanie Lui, Anindya Swarnakar, David Xu, Cieran Tran, Piotr Hubacek, Janelle Smiley-Wiens, Devon Schatz, Laura Lee, Kate Powers, Koichi Nagata, Paul Choi, Fatemeh Shahin, Brandon Furlong, Matthew Roy, Sarah Parke, Dr. Christian Hering-Junghans, Dr. Mike Boone, Derek Zomerman and Nathan Paisley. Thank you to all of the above for your ideas, support, discussion, and most of all for enduring my music. If I was to list individually every person who has made this journey so enjoyable the result would be a document at least double the size of the one that follows, however I must reserve some special thanks to a few people by name, and offer a sincere apology to anybody that I might miss; I’ll buy the beer next time. With that in mind, I’d like to offer my sincere gratitude to the v following for your support and continued friendship: Dr. Matthew Zamora, Dr. Avena Ross, Christopher Sadek, Dr. Lindsay “The Hounje” Hounjet, Dr. Mike Slaney, Dr. Tiffany MacDougall, Dr. Jeremy Gauthier, Kirsten Tomlin, Devin Reaugh, Dr. Mita Dasog, Christina Gonzalez, Sarah Regli, Dr. Melanie Hoffman, Dr. Brenna Brown, Dr. Christian Merten, Lindsay Shearer, Greg Kaufmann, Dr. Brent Rudyk, Dr. Sonja Francis, Dr. Jeremy John, Dr. Teague McGinitie, Dr. Elizabeth McGinitie, Justin Thuss, Colin Diner, and Dr. Katie Nizio. I must also offer my thanks to my friends back in the UK, in particular Rich Jarvis, Scott Greenfield, Steve Haywood, Ross Ballinger, Sean Dunn, Rob Tagg, Danny Middleton, Matt Lane, Steven Collins, Matt Fairbrother, Ian Frost, Chris Kendrick, Liz LeQuelenec, and many, many more. Even though I’ve been gone from the UK for many years now I can still chat with you as though a day has never been lost, and for that I’m forever grateful. vi Abstract ii Acknowledgements iv Table of Contents vii List of Tables xi List of Figures xii List of Schemes xvii List of Symbols, Abbreviations and Nomenclature xx Chapter 1: Introduction 1 1.1 Why transition metal chemistry? 2 1.2 Metal hydrides: an overview 4 1.2.1 Binary metal hydrides 4 1.2.2 Ternary metal hydrides 5 1.2.3 Synthesis of metal hydride complexes 6 1.3 Introduction to specific catalytic processes of 10 relevance to this thesis 1.3.1 Dehydrocoupling catalysis 10 1.3.2 Dehydrocoupling of amine-borane adducts 11 1.4 Recent developments in zinc coordination chemistry 25 and applications 1.4.1 Introduction to zinc chemistry 25 1.4.2 The chemistry of Zn(I) complexes 25 1.4.3 The chemistry of Zn(II) complexes 31 1.5 Acknowledgement of collaborators 40 vii 1.6 References 42 Chapter 2: Synthesis, characterization and dehydro- coupling 47 coupling catalysis reactivity of zirconium complexes bearing hindered bis(amido)silyl ligands 2.1 Abstract 48 2.2 Introduction 49 2.3 Results and discussion 52 2.3.1 Synthesis of bis(amido)silyl zirconium 52 complexes 2.3.2 Dehydrocoupling chemistry mediated by 72 bis(amido)silyl zirconium complexes 2.3.3 Synthesis and reactivity of a zirconium 78 complex featuring a bis(amido)silyl “umbrella” ligand 2.4 Conclusions 80 2.5 Experimental procedures 81 2.6 References 105 Chapter 3: The design and synthesis of new 110 bis(amido)silyl bis(guanidine) ligands for use in main group and transition metal chemistry 3.1 Abstract 111 3.2 Introduction 112 3.3 Results and discussion 115 3.3.1 Synthesis of new “umbrella” ligands 115 featuring tris(3,5-dialkylphenyl)- silylamine groups viii 3.3.2 Synthesis and reactivity of bis(guanidine) 117 ligands with silyl, disilyl and disiloxane spacers 3.4 Conclusion 123 3.5 Experimental procedures 124 3.6 References 143 Chapter 4: Accessing soluble complexes of zinc dihydride, and 146 cationic zinc hydride species via N-heterocyclic carbene stabilisation 4.1 Abstract 147 4.2 Introduction 148 4.3 Results and discussion 151 4.3.1 Carbene complexes of group 12 element 151 dihalides 4.3.2 Attempted synthesis of new group 12 157 hydride complexes using Li[BH4] and Li[HBEt3] as hydride sources 4.3.3 Synthesis of soluble zinc hydride complexes 159 s using K[HB Bu3] as a hydride source, and generation of stable zinc hydride cations. 4.3.4 Catalytic activity of IPr•Zn(H)OTf•THF 175 4.3.5 Zinc halide complexes featuring non-carbene 178 ligands and attempted formation of zinc(II) hydrides 4.4 Conclusions 181 4.5 Experimental procedures 182 4.6 References 206 ix Chapter 5: Towards thermally stable carbonyl complexes of 217 zinc and the utilisation of carbene-stabilised zinc complexes for the deposition of crystalline zinc metal 5.1 Abstract 218 5.2 Introduction 219 5.3 Results and discussion 225 5.3.1 Evidence for the formation of a zinc carbonyl 225 complex 5.3.2 The use of N-heterocyclic carbene complexes 233 of zinc as precursors to crystalline zinc for materials applications 5.4 Conclusions 242 5.5 Experimental procedures 243 5.6 References 256 Chapter 6: Summary and future work 259 x List of Tables Table 2.1 Crystallographic data for 2a and 3 101 Table 2.2 Crystallographic data for 4 and 5 102 Table 2.3 Crystallographic data for 7 and 9•0.5THF 103 Table 2.4 Crystallographic data for 10 and 12•0.5THF 104 Table 3.1 Crystallographic data for 10 and 11 133