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Dalton Trans. 2013 Mar 21;42(11):3843-53. doi: 10.1039/c2dt32457a. Epub 2013 Jan 11.

Biomimetic model for [FeFe]-hydrogenase: asymmetrically disubstituted diiron complex with a redox-active 2,2'-bipyridyl ligand.

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  • 1Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ, USA.

Abstract

[FeFe]-hydrogenases feature a unique active site in which the primary catalytic unit is directly coordinated via a bridging cysteine thiolate to a secondary, redox active [4Fe4S] unit. The goal of this study was to evaluate the impact of a bidentate, redox non-innocent ligand on the electrocatalytic properties of the (μ-S(CH(2))(3)S)Fe(2)(CO)(4)L(2) family of [FeFe]-hydrogenase models as a proxy for the iron-sulfur cluster. Reaction of the redox non-innocent ligand 2,2'-bipyridyl (bpy) with (μ-S(CH(2))(3)S)Fe(2)(CO)(6) leads to substitution of two carbonyls to form the asymmetric complex (μ-S(CH(2))(3)S)Fe(2)(CO)(4)(κ(2)-bpy) which was structurally characterized by single crystal X-ray crystallography. This complex can be protonated by HBF(4)·OEt(2) to form a bridging hydride. Furthermore, electrochemical investigation shows that, at slow scan rates, the complex undergoes a two electron reduction at -2.06 V vs. Fc(+)/Fc that likely involves reduction of both the bpy ligand and the metal. Electrocatalytic reduction of protons is observed in the presence of three distinct acids of varying strengths: HBF(4)·OEt(2), AcOH, and p-TsOH. The catalytic mechanism depends on the strength of the acid.

PMID:
23307026
[PubMed - indexed for MEDLINE]
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