title: Electrochemical insights into the mechanisms of proton reduction by [Fe2(CO)6{micro-SCH2N(R)CH2S}] complexes related to the [2Fe](H) subsite of [FeFe]hydrogenase.
abstract: Electrochemical investigations on a structural analogue of the [2Fe](H) subsite of [FeFe]H(2)ases, namely, [Fe(2)(CO)(6){micro-SCH(2)N(CH(2)CH(2)- OCH(3))CH(2)S}] (1), were conducted in MeCN/NBu(4)PF(6) in the presence of HBF(4)/Et(2)O or HOTs. Two different catalytic proton reduction processes operate, depending on the strength and the concentration of the acid used. The first process, which takes place around -1.2 V for both HBF(4)/Et(2)O and HOTs, is limited by the slow release of H(2) from the product of the {2 H(+)/2 e} pathway, 1-2H. The second catalytic process, which occurs at higher acid concentrations, takes place at different potentials depending on the acid present. We propose that this second mechanism is initiated by protonation of 1-2H when HBF(4)/Et(2)O is used, whereas the reduction of 1-2H is the initial step in the presence of the weaker acid HOTs. The potential of the second process, which occurs around -1.4 V (reduction potential of 1-3H(+)) or around -1.6 V (the reduction potential of 1-2H) is thus dependent on the strength of the available proton source.
authors: UMR CNRS 6521 Chimie, Electrochimie Moléculaires et Chimie Analytique, Université de Bretagne Occidentale, 6 Av. V. Le Gorgeu, 29285 Brest Cedex, France.
authors: Jean-François
authors: JF
authors: Capon
authors: Salah
authors: S
authors: Ezzaher
authors: Frédéric
authors: F
authors: Gloaguen
authors: François Y
authors: FY
authors: Pétillon
authors: Philippe
authors: P
authors: Schollhammer
authors: Jean
authors: J
authors: Talarmin
mesh_terms: D004563:Electrochemistry / Q000379:methods*; D006864:Hydrogenase / Q000378:metabolism*; D058085:Iron Compounds / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D011522:Protons
chemical_list: D058085:Iron Compounds; D007506:Iron-Sulfur Proteins; D011522:Protons; C118830:iron hydrogenase; D006864:Hydrogenase