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

The reactions of the precursor complex [Fe-2(CO)(6)(-bdt)] F with PPh3, PPh2Me, PPh2H have been investigated. Treatment of F with the phosphine ligands yielded both mono- and disubstituted complexes [Fe-2(CO)(5)(-bdt)(PPh3)] (1), [Fe-2(CO)(4)(-bdt)(PPh3)(2)] (2), [Fe-2(CO)(5)(-bdt)(PPh2Me)] (3), [Fe-2(CO)(4)(-bdt)(PPh2Me)(2)] (4), [Fe-2(CO)(5)(-bdt)(PPh2H)] (5) and [Fe-2(CO)(4)(-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.