Electrocatalytic reduction of carbon dioxide with Mn(terpyridine) carbonyl complexes.

The behavior of a series of Manganese (Mn) carbonyl compounds with 2,2':6',2''-terpyridine (tpy) in κ2-N,N' and κ3-N,N',N'' coordination modes under electrochemically reducing conditions is reported. In the presence of carbon dioxide (CO2) and Brønsted acid (phenol), two-electron reduction to carbon monoxide (CO) and water (H2O) is observed. Based on data obtained from cyclic voltammetry and infrared spectroelectrochemistry, the active state of the catalyst in the proposed mechanism for all cases is [Mn(κ3-N,N',N''-tpy)(CO)2]-. Under these conditions, competing decomposition reactions limit the overall Faradaic efficiency. These results suggest the possibility of developing new tridentate ligand frameworks suitable for catalytic systems with Mn carbonyl cores.