Homogeneous Electrochemical Reduction of CO to CO by a Cobalt Pyridine Thiolate Complex.

The chemical and electrochemical reduction of CO to value added chemicals entails the development of efficient and selective catalysts. Synthesis, characterization and electrochemical CO reduction activity of a air-stable cobalt(III) diphenylphosphenethano-bis(2-pyridinethiolate)chloride [{Co(dppe)(2-PyS)}Cl, ] complex is divulged. The complex reduces CO under homogeneous electrocatalytic conditions to produce CO with high Faradaic efficiency (FE > 92%) and selectivity in the presence of water. Through detailed electrochemical investigations, product analysis, and mechanistic investigations supported by theoretical calculations, it is established that complex reduces CO in its Co(I) state. A reductive cleavage leads to a dangling protonated pyridine arm which enables facile CO binding through a H-bond donation and facilitates the C-O bond cleavage via a directed protonation. A systematic benchmarking of this catalyst indicates that it has a modest overpotential (∼180 mV) and a TOF of ∼20 s for selective reduction of CO to CO with HO as a proton source.