title: Cobaloximes as functional models for hydrogenases. 2. Proton electroreduction catalyzed by difluoroborylbis(dimethylglyoximato)cobalt(II) complexes in organic media.
abstract: Cobaloximes are effective electrocatalysts for hydrogen evolution and thus functional models for hydrogenases. Among them, difluoroboryl-bridged complexes appear both to mediate proton electroreduction with low overpotentials and to be quite stable in acidic conditions. We report here a mechanistic study of [Co(dmgBF2)2L] (dmg2- = dimethylglyoximato dianion; L = CH3CN or N,N-dimethylformamide) catalyzed proton electroreduction in organic solvents. Depending on the applied potential and the strength of the acid used, three different pathways for hydrogen production were identified and a unified mechanistic scheme involving cobalt(II) or cobalt(III) hydride species is proposed. As far as working potential and turnover frequency are concerned, [Co(dmgBF2)2(CH3CN)2], in the presence of p-cyanoanilinium cation in acetonitrile, is one of the best synthetic catalysts of the first-row transition-metal series for hydrogen evolution.
authors.affiliation: Laboratoire de Chimie et Biologie des Métaux, Université Joseph Fourier, CNRS, UMR 5249, and CEA, DSV/iRT SV/LCBM, 38054 Grenoble, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Baffert
authors.forename: Vincent
authors.initials: V
authors.lastname: Artero
authors.forename: Marc
authors.initials: M
authors.lastname: Fontecave
mesh_terms: D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D004563:Electrochemistry; D006859:Hydrogen / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006864:Hydrogenase / Q000737:chemistry*; D008024:Ligands; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010091:Oximes / Q000737:chemistry*; D011522:Protons; D012997:Solvents / Q000737:chemistry
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D010091:Oximes; D011522:Protons; D012997:Solvents; D003035:Cobalt; D006859:Hydrogen; D006864:Hydrogenase