Organometallic Ni pincer complexes for the electrocatalytic production of hydrogen

Nonplatinum metals are needed to perform cost-effective water reduction electrocatalysis to enable technological implementation of a proposed hydrogen economy. We describe electrocatalytic proton reduction and H(2) production by two organometallic nickel complexes with tridentate pincer ligands. The kinetics of H(2) production from voltammetry is consistent with an overall third order rate law: the reaction is second order in acid and first order in catalyst. Hydrogen production with 90-95% Faradaic yields was confirmed by gas analysis, and UV-vis spectroscopy suggests that the ligand remains bound to the catalyst over the course of the reaction. A computational study provides mechanistic insights into the proposed catalytic cycle. Furthermore, two proposed intermediates in the proton reduction cycle were isolated in a representative system and show a catalytic response akin to the parent compound.