A Bioinspired Nickel(bis-dithiolene) Complex as a Homogeneous Catalyst for Carbon Dioxide Electroreduction

Inspired by the metal active sites of formate dehydrogenase and CO-dehydrogenase, a nickel complex containing a NiS4 motif with two dithiolene ligands mimicking molybdopterin has been prepared and structurally characterized. During electroreduction, it converts to a good catalyst for the reduction of CO2 into formate as the major product, together with minor amounts of carbon monoxide and hydrogen, with reasonable overpotential requirement, good faradaic yield, and notable stability. Catalysis operates on a mercury electrode and dramatically less on a carbon electrode, as observed in the case of [Ni(cyclam)](2+) complexes. Density functional theory (DFT) computations indicate the key role of a Ni(III)-hydride intermediate and provide insights into the different reaction pathways leading to HCOOH, CO, and H-2. This study opens the route toward a new, yet unexplored, class of mononuclear sulfur-coordinated Ni catalysts for CO2 reduction.