Formate oxidationvia β-deprotonation in [Ni(PR2NR′2)2(CH3CN)]2+ complexes

Abstract

Recent studies from our laboratories have shown that the [Ni(P^R₂N^R′₂)₂(CH₃CN)]²⁺ complexes originally developed as artificial hydrogenases are also active electrocatalysts for formate oxidation (TOF ∼16 s⁻¹). The focus of the current work is to develop a detailed understanding of the catalytic mechanism, which would aid in the design of improved catalysts for the interconversion of CO₂ and formate. Based on electrochemical and spectroscopic experiments, including data for a new [Ni(P^Cy₂N^PhOMe₂)₂(CH₃CN)]²⁺ complex, we propose a mechanism in which the rate-determining step is a proton transfer from the Ni–O₂CH β-H to the ligand pendant base coupled with a 2e⁻ transfer to Ni(II), circumventing direct hydride transfer to the metal.