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Mechanistic Insights into the Catalysis of Electrochemical Proton Reduction by a Diiron Azadithiolate Complex

Abstract : Cyclic voltammetry experiments and DFT calculations allowed us to establish a complete mechanism of the catalysis of electrochemical proton reduction by [Fe2(μ-SCH2N(H)CH2S)(CO)6] (Fe–adt) in acetonitrile. The proposed mechanism is fully consistent with the observed dependence of the voltammetric responses on the strength of the acid used as a proton source. Addition of moderately strong acids, such as CCl3CO2H (pKa = 10.7) or HOTs·H2O (pKa = 8.6), triggers the occurrence of new reduction events at potentials less negative than the reduction of Fe–adt, therefore ascribed to reduction of the protonated forms of the complex. Reduction of the N-protonated form seems to favor a tautomerization reaction leading to a Fe–H intermediate. On the other hand, addition of weak acids, such as ClCH2CO2H (pKa = 15.3), leads to direct protonation on the diiron site subsequently to reduction of the catalyst. A better understanding of the mechanism of proton reduction by the biologically relevant Fe–adt derivative could impact the design of improved catalysts inspired by FeFe–hydrogenase.
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https://hal.univ-brest.fr/hal-01535888
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Submitted on : Friday, June 9, 2017 - 4:20:33 PM
Last modification on : Wednesday, September 11, 2019 - 2:14:07 PM

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Marc Bourrez, Romain Steinmetz, Frederic Gloaguen. Mechanistic Insights into the Catalysis of Electrochemical Proton Reduction by a Diiron Azadithiolate Complex. Inorganic Chemistry, American Chemical Society, 2014, 53 (19), pp.10667 - 10673. ⟨10.1021/ic501815m⟩. ⟨hal-01535888⟩

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