EPR study of paramagnetic rhenium(I) complexes (bpy>>·>>−>>)Re(CO)3X relevant to the mechanism of electrocatalytic CO2 reduction †

In situ reduction of (bpy)Re(CO)3Cl, bpy = 2,2′-bipyridine, at a platinum cathode under CO2 atmosphere in acetonitrile or acetone has produced a series of distinct EPR spectra which are attributed to (bpy˙–) containing species and which invariably reveal the interaction of the unpaired electron with the metal nuclei (185,187Re, I = 5/2). The EPR investigation of various model complexes (bpy˙–)Re(CO)3X, generated by electrochemical reduction under argon of diamagnetic precursors (bpy)Re(CO)3X, X = Cl–, CF3SO3–, CH3O–, H–, tetrahydrofuran, CH3CN, CO, HCO2–, HCO3– and CH3C(O)– has been used to interpret the results from the reactions under CO2 atmosphere.