This is, indeed, the case as shown in Fig. 9. Unlike complex 1 whose electrochemical behaviours showed great sensitivity towards the presence of CO ( Fig. 2 and Fig. 3), there was no significant improvement in electrochemical reversibility when working atmosphere was switched from Ar to CO. Thus, we assumed that monoanion 2− reacts with the ligand and loses one CO to form 2L− which undergoes radical exchange reaction with the parent complex 2 to produce a pentcarbonyl product and regenerate the catalyst 2−. An overall mechanism for the catalytic substitution reactions is delineated in Scheme 2.