Re(bipy-tBu)(CO)3Cl−improved Catalytic Activity for Reduction of Carbon Dioxide: IR-Spectroelectrochemical and Mechanistic Studies

• Published in: Inorganic chemistry 2010-10, Vol.49 (20), p.9283-9289
• Main Authors: Smieja, Jonathan M, Kubiak, Clifford P
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic1008363

Five Re(bipy)(CO)3Cl complexes were prepared and studied where bipy was 4,4′-dicarboxyl-2,2′-bipyridine (1), 2,2′-bipyridine (2), 4,4′-dimethyl-2,2′-bipyridine (3), 4,4′-di-tert-butyl-2,2′-bipyridine (4), and 4,4′-dimethoxy-2,2′-bipyridine (5). From this group, a significantly improved catalyst, Re(bipy-tBu)(CO)3Cl (4), for the reduction of carbon dioxide to carbon monoxide was found. The complex shows two one-electron reductions under argon, one reversible at −1445 mV (vs SCE), and one irreversible at −1830 mV. Under CO2 the second irreversible wave displays a large catalytic enhancement in current. Diffusion coefficients were determined using the Levich−Koutecky method (1.1 × 10−5 cm2/s for the neutral complex and 8.1 × 10−6 cm2/s for the singly reduced species), and a second order rate constant for the electrochemical reduction with CO2 of 1000 M−1 s−1 was measured. Bulk electrolysis studies were performed to measure Faradaic efficiencies for the primary gaseous products, ηCO = 99 ± 2% in acetonitrile.