Understanding Nickel Catalysis at the Molecular Level: Insights into C-O Functionalization and Electron Transfer Events

Chemists have developed innovative technologies for the functionalization of typically inert bonds which take advantage of the hard and electropositive nature of nickel to cleave C(sp²)-O bonds. Utilizing simple and readily available phenol-derived precursors in place of aryl halide electrophiles opens a range of untraditional electrophiles for the construction of molecular complexity. Additionally, the mild reduction potentials and ability of nickel complexes to exist as odd or even oxidation states have seen their significant use as catalysts for reductive coupling reactions. In line with our groups interests in Ni-catalyzed cross-coupling reactions, this thesis will focus on the mechanistic understanding and catalytic implications of key nickel catalyzed reactions in C(sp²)-O functionalization and reductive cross-coupling.

The first research chapter focuses on studying the mechanism of C(sp²)-O bond functionalization of aryl esters in combination with aryl zinc reagents. The following chapter then studies the effect of strong reductants on reductive coupling reactions employing redox active ligands in which the interaction between strongly reducing magnesium metal and polypyridine ligated nickel complexes is studied and a highly reduced bipyridine magnesium complex is isolated. The final chapter focuses on studying factors that contribute to electron transfer events such as comproportionation, disproportionation and reduction for polypyridine ligated nickel complexes. Together, these findings identified new fundamental organometallic reactivity and key organometallic intermediates that are relevant for the development of synthetic methodologies and for future mechanistic investigations.

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