Highly Selective Acetone Electroreduction by Molecular Iron Catalysts: Role of Cobaltocene as Electrochemical Mediator.

Electrocatalytic carbonyl reduction provides an approach to store renewable energy in liquid fuels. However, competing hydrogen evolution from protonation of molecular transition metal hydride catalysts and direct acid reduction at the electrode both limit the Faradaic efficiency for carbonyl electrohydrogenation. We report a series of iron cyclopentadienone transfer hydrogenation catalysts adapted to acetone electroreduction to isopropanol in neat substrate. With cobaltocene as a net-hydride transfer mediator, we show that the tandem catalytic system is highly selective for acetone reduction to iPrOH without the release of gaseous hydrogen. This demonstrates the generalizability of cobaltocene as an electrochemically regenerable proton coupled electron transfer (PCET) mediator for improving overpotential and Faradaic efficiency of electrocatalytic carbonyl reduction.