Nickel-catalyzed cooperative B-H bond activation for hydroboration of N‑heteroarenes, ketones and imines

Abstract

We report two air-stable nickel(II) half-sandwich complexes, Cp*Ni(1,2-Cy2PC6H4O) (1) and Cp*Ni(1,2-Ph2PC6H4NH) (2), for cooperative B-H bond activation and their applications in catalytic hydroboration of unsaturated organic compounds. Both 1 and 2 react with HBpin by adding the B-H bond across the Ni−X bond (X = O or N), giving rise to the 18-electron Ni(II)−H active species, [H1(Bpin)] and [H2(Bpin)]. Subtle tuning of the Ni−X pair and the supporting ancillary phosphine have a significant effect on the reactivity and catalytic performance of Cp*Ni(1,2-R2PC6H4X). Unlike [H2(Bpin)], the activation of HBpin in [H1(Bpin)] is reversible, which enables the Ni−O complex to be an effective cooperative catalyst in the hydroboration of N-heteroarenes, and as well as ketones and imines.