Electrochemical proton reduction catalysed by selenolato-manganese carbonyl complexes

Abstract

Four manganese selenolato carbonyl complexes [Mn(CO)₄(μ-SePh)]₂ 1, Mn₂(CO)₄(μ-CO)(μ-SePh)₂(PBu₃)₂ (2, PBu₃ = tri-n-butylphosphine), Mn(CO)₄(μ-SePh)₂Mn(CO)₃(Py)(3, Py = pyridine) and Mn(CO)₃(SePh)(DPPP) (4, DPPP = 1,3-bis(diphenylphosphino)propane) have been synthesized and structurally characterized by X-ray crystallography. Their electrocatalytic proton reduction properties have been measured with cyclic voltammetry in dichloromethane using CF₃COOH as the proton source. Overpotentials ranging from 0.79 V to 0.89 V were determined for these complexes. The presence of different ligands such as phosphine and pyridine only made moderate differences to the overpotential and efficiency of the proton reduction process. The first step in the proton reduction pathway occurs via electroreduction of the Mn complexes based on reactivity studies and cyclic voltammetry data.