[FeFe]-hydrogenase H-cluster mimics mediated by mixed (S, Se) and (S, Te) bridging moieties: Insight into molecular structures and electrochemical characteristics

Two synthetic models of the active site of [FeFe]-hydrogenase containing mixed (S, Se) and (S, Te) bridges have been synthesized and characterized. These complexes [Fe-2(CO)(6){mu-S(CH2)(4)E-mu)}] (E = Se (1), Te (2)) are obtained in moderate yields from the reaction of Fe-3(CO)(12) with 1,2-thiaselenane or 1,2-thiatellurane. They have been characterized by spectroscopic techniques (IR, H-1-, C-13{H-1}-, Se-77{H-1}-, Te-125{H-1}-NMR, and MS) and elemental analysis. The structures of [Fe-2(CO)(6){mu-S(CH2)(4)Se-mu)}] and [Fe-2(CO)(6){mu-S(CH2)(4)Te-mu)}] are determined by X-ray structure determination and show the expected butterfly geometry. Moreover, the influence of the mixed chalcogen atoms on the redox properties and the catalytic behavior of 1 and 2 are studied using cyclic voltammetry.