Exploring Small Molecule Reactivity with Low-Valent Nickel and Cobalt Complexes Supported by Lewis Acidic Metalloligands

Abstract

This thesis details/describes the synthesis and characterization of heterobimetallic complexes that utilize a bifunctional amido-phosphine ligand to stabilize bonds between a Lewis acid (aluminum, gallium, or indium) and a late transition metal center (cobalt, nickel, or copper). Ultimately, the ability to tune the electronic properties of the transition metal center is utilized to design new catalysts for small molecule conversions. General characterization of these species includes single crystal x-ray diffraction, electronic structure calculations, nuclear magnetic resonance studies, cyclic voltammetry, and electron paramagnetic resonance spectroscopy. In the first chapter, a Lewis acid-cobalt interaction is utilized to stabilize sub-valent cobalt species that bind dihydrogen in a side on fashion with moderate activation. In the second chapter, these cobalt dihydrogen complexes are studied by high-pressure NMR spectroscopy and studies reveal that they catalyze the room temperature hydrogenation of carbon dioxide. These catalysts operate via a unique mechanism and produce formate with high turnover frequencies and numbers in the presence of organic bases. The third chapter focuses on the electronic structure of related nickel species, specifically towards understanding the role of 4p orbitals in the nickel-metal bond. The last chapter details thermodynamic parameters and small molecules reactivity of a unique class of metal hydride complexes supported by direct Lewis acid- metal interactions.