Diiron Benzenedithiolate Complexes Relevant to the [FeFe] Hydrogenase Active Site

The reactions of the precursor complex [Fe2(CO)6(μ-bdt)] F with PPh3, PPh2Me, PPh2H have been investigated. Treatment of F with the phosphine ligands yielded both mono- and disubstituted complexes [Fe2(CO)5(μ-bdt)(PPh3)] (1), [Fe2(CO)4(μ-bdt)(PPh3)2] (2), [Fe2(CO)5(μ-bdt)(PPh2Me)] (3), [Fe2(CO)4(μ-bdt)(PPh2Me)2] (4), [Fe2(CO)5(μ-bdt)(PPh2H)] (5) and [Fe2(CO)4(μ-bdt)(PPh2H)2] (6). Crystal structures have been reported for complexes 1–3. Complexes 1, 3 and 5 participate in electrocatalytic proton reduction in the presence of two distinct acids of varying strengths: HClO4 and CF3CO2H.