Vitamin B12 Research Today is a free monthly online journal that collates and summarizes the latest research about Vitamin B12, including details on cyanocobalamin, benefits, supplements, deficiency, side-effects, sources.

Proton electroreduction catalyzed by cobaloximes: functional models for hydrogenases.

Razavet M, Artero V, Fontecave M

Laboratoire de Chimie et Biochimie des Centres Rédox Biologiques, UMR 5047 CEA/CNRS/Université Joseph Fourier, CEA-Grenoble, DRDC/CB, Bat K', 17 rue des Martyrs, 38054 Grenoble Cedex 09, France.

Cobaloximes have been examined as electrocatalysts for proton reduction in nonaqueous solvent in the presence of triethylammonium chloride. [Co(III)(dmgH)2pyCl], working at moderate potentials (-0.90 V/(Ag/AgCl/3 mol x L(-1) NaCl) and in neutral conditions, is a promising catalyst as compared to other first-row transition metal complexes which generally function at more negative potentials and/or at lower pH. More than 100 turnovers can be achieved during controlled-potential electrolysis without detectable degradation of the catalyst. Cyclic voltammograms simulation is consistent with a heterolytic catalytic mechanism and allowed us to extract related kinetic parameters. Introduction of an electron-donating (electron-withdrawing) substituent in the axial pyridine ligand significantly increases (decreases) the rate constant of the catalytic cycle determining step. This effect linearly correlates with the Hammet coefficients of the introduced substituents. The influence of the equatorial glyoxime ligand was also investigated and the capability of the stabilized BF2-bridged species [Co(dmgBF2)2(OH2)2] for electrocatalyzed hydrogen evolution confirmed.

Published 20 June 2005 in Inorg Chem, 44(13): 4786-95.
Full-text of this article is available online (may require subscription).

© 2004-2008 Vitamin B12 Research Today. All Rights Reserved.