Hydrofunctionalization of Olefins with Diimine and Bis(imino)pyridine Nickel Catalysts

Abstract

Chemical transformations catalyzed by transition metals often rely on the use of economically and environmentally costly precious metals. Catalysis using Earth-abundant base metals coupled with redox non-innocent ligands show promise to make transition metal mediated reactions more sustainable and less costly. Hydrofunctionalization, specifically hydroboration and hydrosilylation, remains a sector of catalysis dominated by precious metal catalysts. Previous research has demonstrated the synthetic utility of iron and cobalt centered catalysts for hydrosilylation and hydroboration, but little research has been conducted on nickel mediated hydrofunctionalization for synthetically relevant catalysis. The screening of numerous redox non-innocent ligands with cheaply attainable nickel carboxylates has demonstrated diimine and bis(imino)pyridine ligands as effective hydroboration and hydrosilylation in-situ generated catalysts, generated from air-stable precursors. Subsequent studies on the substrate scope of each catalytic system revealed that the diimine ligand (iPrDI) exhibited favorable reactivity only with otherwise aliphatic olefins for hydroboration and hydrosilylation. Using the bis(imino)pyridine ligand, tfAPDI, this catalytic system demonstrated additional tolerance for dienes for hydroboration. Studies on various isolated catalysts were also conducted alongside EPR spectroscopic characterization of the in-situ generated catalysts.