Combining acid-base, redox and substrate binding functionalities to give a complete model for the [FeFe]-hydrogenase.

Some enzymes function by coupling substrate turnover with electron transfer from a redox cofactor such as ferredoxin. In the [FeFe]-hydrogenases, nature's fastest catalysts for the production and oxidation of H(2), the one-electron redox by a ferredoxin complements the one-electron redox by the diiron active site. In this Article, we replicate the function of the ferredoxins with the redox-active ligand CpFe(C(5)Me(4)CH(2)PEt(2)) (FcP). FcP* oxidizes at mild potentials, in contrast to most ferrocene-based ligands, which suggests that it might be a useful mimic of ferredoxin cofactors. The specific model is Fe(2)(SCH(2))(2)NBn(3)(FcP*)(dppv) (1), which contains the three functional components of the active site: a reactive diiron centre, an amine as a proton relay and, for the first time, a one-electron redox module. By virtue of the synthetic redox cofactor, 1 exhibits unique reactivity towards hydrogen and CO. In the presence of excess oxidant and base, H(2) oxidation by 1 is catalytic.