UBC Theses and Dissertations
Amidate and ureate complexes of nickel : harnessing ligand design to understand the mecha(Ni)sm of C-H bond activation Beattie, Douglas Dawson
This thesis examines the use of hemi-labile amidate and ureate ligands on nickel metal centers in their (+1) and (+2) oxidation states. These 1,3-N,O-chelating ligands were studied both for their coordination chemistry on nickel and their propensity to undergo bond activations, specifically with carbon-hydrogen bonds. In Chapter 1 we discuss the mechanisms of C-H bond activation for nickel centers of different oxidation states. We highlight important works for each oxidation state, with a focus on computational and mechanistic work. The Chapter is broken down by oxidation state. In Chapter 2, we investigate the mechanism of Ni(II) C(sp³)-H bond activation. Using ureas as model substrates, we map the rates of C-H bond activation at Ni(II). We also characterize the nickellated products and investigate the role of additives on the rates of reaction. Comparisons to computational data from the literature are made where appropriate. In Chapter 3 we discuss amides as ligands for low-coordinate Ni(I) organometallics. Using a variety of ligands, we show that substitution of the ligand at both the nitrogen and the carbon backbone dramatically affects the binding mode at Ni(I). We also discuss reactivity with radical species and investigate the mechanism of disproportionation of these complexes. In Chapter 4 we discuss a new method for nickel catalyzed cyanation of aryl chlorides using a simple protocol. The reaction runs at room temperature and is among the mildest conditions to date. We show that XantPhos ligands are the best ligands to this end.
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