Synthesis and Reactivity of Group 12 Β-Diketiminate Coordination Complexes
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Synthesis and Reactivity of Group 12 β-Diketiminate Coordination Complexes By Dylan Webb A thesis Submitted to Victoria University of Wellington in fulfilment of the requirements for the degree of Masters of Science In Chemistry Victoria University of Wellington 2016 Abstract The variable β-diketiminate ligand poses as a suitable chemical environment to explore unknown reactivity and functionality of metal centres. Variants on the β-diketiminate ligand can provide appropriate steric and electronic stabilization to synthesize a range of β-diketiminate group 12 metal complexes. This project aimed to explore various β-diketiminate ligands as appropriate ancillary ligands to derivatise group 12 element complexes and investigate their reactivity. i A β-diketiminato-mercury(II) chloride, [o-C6H4{C(CH3)=N-2,6- Pr2C6H3}{NH(2,6- i i Pr2C6H3)}]HgCl, was synthesized by addition of [o-C6H4{C(CH3)=N-2,6- Pr2C6H3}{NH(2,6- i Pr2C6H3)}]Li to mercury dichloride. Attempts to derivatise the β-diketiminato-mercury(II) chloride using salt metathesis reactions were unsuccessful with only β-diketiminate ligand degradation products being observed in the 1H NMR. i A β-diketiminato-cadmium chloride, [CH{(CH3)CN-2,6- Pr2C6H3}2]CdCl, was derivatized to a i β-diketiminato-cadmium phosphanide, [CH{(CH3)CN-2,6- Pr2C6H3}2]Cd P(C6H11)2, via a lithium dicyclohexyl phosphanide and a novel β-diketiminato-cadmium hydride, [CH{(CH3)CN-2,6- i Pr2C6H3}2]CdH, via Super Hydride. Initial reactivity studies of the novel cadmium hydride with various carbodiimides yielded a β-diketiminato-homonuclear cadmium-cadmium i dimer, [CH{(CH3)CN-2,6- Pr2C6H3}2Cd]2, which formed via catalytic reduction of the cadmium hydride. Attempts to synthesize an amidinate insertion product via a salt metathesis reaction or a ligand exchange reaction proved unsuccessful but a novel cadmium amidinate, [{CH(N-C6H11)2}2{CH(N-C6H11)(N(H)-C6H11)}Cd], was synthesized from addition of dicyclohexyl formamidine to bis-hexamethyldisilazane cadmium. i i A β-diketiminato-zinc(II) bromide, [o-C6H4{C(CH3)=N-2,6- Pr2C6H3}{NH(2,6- Pr2C6H3)}]ZnBr, i i was synthesized by addition of [o-C6H4{C(CH3)=N-2,6- Pr2C6H3}{NH(2,6- Pr2C6H3)}]Li to zinc dibromide. The β-diketiminato-zinc(II) bromide was derivatized to a variety of complexes (including amides and phosphanides) by a salt metathesis reaction. Chalcogen addition i reactions were performed from [o-C6H4{C(CH3)=N-2,6- Pr2C6H3}{NH(2,6- i Pr2C6H3)}ZnP(C6H11)2] to produce double addition products from sulfur, selenium and ii i tellurium. Chalcogen addition reactions from [o-C6H4{C(CH3)=N-2,6- Pr2C6H3}{NH(2,6- i Pr2C6H3)}ZnP(C6H5)2] produced a double addition product for selenium and a i β-diketiminato-zinc(II) tellunoite bridged dimer, [o-C6H4{C(CH3)=N-2,6- Pr2C6H3}{NH(2,6- i Pr2C6H3)}Zn]Te, from tellurium. A total of 14 compounds were characterized via X-ray diffraction. Photoluminescence studies of the β-diketiminato-zinc(II) compounds were conducted where it was proposed that an electron transfer from the lone pair on the hetero-atom influenced the quantum yield and fluorescence intensities. iii Acknowledgements Firstly, I would like to express my gratitude to my supervisor Dr. Robin Fulton for her continuous support of my research, her patience and consistent motivation. She constantly allowed this thesis to be my own work, but always steered me in the right the direction. I would like to acknowledge the other academics who contributed to my research: Assoc Prof. Martyn Coles for his aid in crystallography and “unnecessary” input and technicians Jackie King and Ian Vorster for their patience with me and their machines. I thank my fellow co-workers Struan, Putri, Loc, Grace, Peter, Cara and Ryan for the “stimulating” discussions, all the fun we have had in the last two years and for being my surrogate siblings, for better and for worse. A special thanks to Bradley White for his work during his undergraduate studies towards some of this research. Over the past two years I have received funding from the Curtis-Gordon Research Scholarship in Chemistry for which I could not thank enough. Last but not least, I must thank my parents for their constant support and words of encouragement, my loving girlfriend Danielle and the friends I have had the pleasure spending time with; in particular my flatmate Daniel, the other Masters students Jaime, Sarah and Matt and close friends Emma and Christoph. iv Table of Contents Abstract ...................................................................................................................................... ii Acknowledgements ................................................................................................................... iv Glossary of Terms and Abbreviations ...................................................................................... vii Nomenclature ........................................................................................................................... ix List of Figures ............................................................................................................................ xi List of Schemes........................................................................................................................ xiii List of Tables ........................................................................................................................... xiv Structural List of Newly Synthesized Compounds ................................................................... xv 1 Background and Literature ................................................................................................. 1 1.1 Introduction................................................................................................................. 1 1.1.1 Group 12 Elements .............................................................................................. 1 1.1.2 The β-Diketiminate Ligand ................................................................................... 2 1.2 Project Aims ................................................................................................................ 4 1.3 Important Chemical Reactions .................................................................................... 4 1.4 Mercury Compounds ................................................................................................... 8 1.4.1 Background .......................................................................................................... 8 1.4.2 Coordination Chemistry ....................................................................................... 9 1.5 Cadmium Compounds ............................................................................................... 14 1.5.1 Background ........................................................................................................ 14 1.5.2 Coordination Chemistry ..................................................................................... 15 1.6 Zinc Compounds ........................................................................................................ 20 1.6.1 Background ........................................................................................................ 20 1.6.2 Coordination Chemistry ..................................................................................... 21 1.6.1 Research from 2014 ........................................................................................... 25 1.7 Pre-Thesis Research Motive ...................................................................................... 37 1.7.1 Synthesis of [Ar-BDIDipp-H] ................................................................................. 37 2 Results and Discussion ...................................................................................................... 38 2.1 Mercury ..................................................................................................................... 38 2.1.1 Synthesis of β-Diketiminato-mercury Chloride ................................................. 38 2.2 Cadmium ................................................................................................................... 41 2.2.1 Alternative Synthesis of β-Diketiminato-cadmium Chloride ............................. 41 2.2.2 Derivatization of β-Diketiminato-cadmium Chloride ........................................ 41 v 2.2.3 Reactivity of β-Diketiminato-cadmium Hydride ................................................ 45 2.3 Zinc ............................................................................................................................ 52 2.3.1 Synthesis of a Novel β-Diketiminato-zinc Bromide ........................................... 52 2.3.2 Derivatization of a Novel β-Diketiminato-zinc Bromide .................................... 55 2.3.3 Photoluminescence of β-Diketiminato-zinc Complexes .................................... 73 2.4 Summary of Results ................................................................................................... 78 3 Experimental ..................................................................................................................... 80 4 Appendices ....................................................................................................................... 96 4.1 Appendix A: NMR Spectra of Novel Compounds ...................................................... 96 4.2 Appendix B: Crystal Data Tables ............................................................................