Electrocatalytic metal hydride generation using concerted proton electron transfer mediators

The electrochemical generation of metal hydride (M H) species remains one of the major hurdles for a wide range of catalytic reactions to be carried out electrochemically. We introduce here a new strategy for electrocatalytic M H generation using concerted proton electron transfer (CPET) mediators. We investigate the combination of a series of CPET mediators with the CO2 electroreduction catalyst [MnI(bpy)(CO)3Br] (bpy = 2,2’-bipyridine), probing the reversal of the product selectivity from CO to HCOOH to evaluate the efficiency of the M H generation step. We demonstrate the formation of the manganese-hydride by in-situ spectroscopic techniques and determine the thermodynamic boundary conditions for this mechanism to occur. A synthetic iron-sulfur cluster is identified as the best CPET-mediator for that system, enabling the preparation of a benchmark catalytic system for HCOOH generation.