A Molecular Ruthenium Electrocatalyst for the Reduction of Carbon Dioxide to CO and Formate

The use of a bulky bipyridine ligand, 6,6′-dimesityl-2,2′-bipyridine (mesbpy), to enable the reduction of carbon dioxide by a Ru-based molecular electrocatalyst is reported. Under catalytic conditions, this compound exhibits turnover frequencies of 1300 s–1 and 95% Faradaic efficiency for the production of CO and H2O from CO2 in the presence of Brønsted acids. Mechanistic electrochemical and spectroelectrochemical studies, supplemented by the direct synthesis of relevant intermediates, indicate that this behavior is the result of the cooperative redox response of the bipyridine ligand and Ru metal center at negative potentials, as well as the inhibition of Ru–Ru bond formation through steric interactions.