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 Cp*Fe(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](CO) 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] ²⁺ exhibits unique reactivity towards hydrogen and CO. In the presence of excess oxidant and base, H ₂ oxidation by [1] ²⁺ is catalytic.