A Diferrous Dithiolate as a Model of the Elusive H ox inact State of the [FeFe] Hydrogenases: An Electrochemical and Theoretical Dissection of Its Redox Chemistry

Abstract : The reduction of the Fe(II)Fe(II) complex [Fe2(CO)2{P(OMe)3}2(κ2-IMe-CH2-IMe)(μ-CO)(μ-pdt)]2+ (2P2+; pdt = S(CH2)3S), which is a synthetic model of the H cluster of the [FeFe] hydrogenases in its inactive state, has been investigated electrochemically and theoretically (by density functional theory, DFT) in order to determine the mechanisms, intermediates, and products of the related processes. The electrochemical reduction of 2P2+ occurs according to an ECE-type reaction where the intervening chemical step is the loss of one P(OMe)3 ligand. This outcome, which is based on cyclic voltammetric experiments, is strongly supported by DFT calculations that provide additional information on the intermediates and the energetics of the reactions involved. The electrochemical reoxidation of the neutral product of the reduction follows an EEC process where the chemical step is the binding of P(OMe)3 to a dicationic intermediate. DFT calculations reveal that this intermediate has an unusual geometry wherein one of the two C–H bonds of a side methylene from the pdt group forms an agostic interaction with one Fe center. This interaction is crucial to stabilize the 32e− diferrous center and concomitantly to preserve Fe(II) from binding of weakly coordinating species. Nonetheless, it could be displaced by a relatively stronger electron donor such as H2, which could be relevant for the design of new oxidation catalysts.
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Inorganic Chemistry, American Chemical Society, 2015, 54 (1), pp.299 - 311. 〈http://pubs.acs.org/doi/abs/10.1021/ic5024746〉. 〈10.1021/ic5024746〉
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Soumis le : mardi 13 juin 2017 - 16:56:27
Dernière modification le : mercredi 11 avril 2018 - 10:56:01

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Dounia Chouffai, Jean-François Capon, Luca De Gioia, François Y. Pétillon, Philippe Schollhammer, et al.. A Diferrous Dithiolate as a Model of the Elusive H ox inact State of the [FeFe] Hydrogenases: An Electrochemical and Theoretical Dissection of Its Redox Chemistry. Inorganic Chemistry, American Chemical Society, 2015, 54 (1), pp.299 - 311. 〈http://pubs.acs.org/doi/abs/10.1021/ic5024746〉. 〈10.1021/ic5024746〉. 〈hal-01538585〉

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