Reductive Disproportionation of Carbon Dioxide by an Alkyl-Functionalized Pyridine Monoimine Re(I) fac-Tricarbonyl Electrocatalyst

A Re­(I) fac-tricarbonyl complex with a 2-(2-cyclohexyl-1-methyl)-methylimino-pyridine ligand is found to electrocatalyze the reductive disproportionation of two equivalents of CO2 to CO and CO32–. Electrochemical and spectroelectrochemical experiments, supplemented by stoichiometric reactions with chemically reduced species, indicate that this reaction is catalyzed via a process that is first-order in [Re]. These findings show that the decreased aromaticity of pyridine monoimine ligands (relative to that of previously studied bipyridine systems) has mechanistic implications for the electrocatalytic reduction of CO2 with Re complexes. NMR experiments indicate that this is also manifested in a competing pathway where CO2 undergoes a reductive insertion reaction into the monoamine ligand.