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

The reactions of the precursor complex [Fe 2 (CO) 6 (μ‐bdt)] F with PPh 3 , PPh 2 Me, PPh 2 H have been investigated. Treatment of F with the phosphine ligands yielded both mono‐ and disubstituted complexes [Fe 2 (CO) 5 (μ‐bdt)(PPh 3 )] ( 1 ), [Fe 2 (CO) 4 (μ‐bdt)(PPh 3 ) 2 ] ( 2 ), [Fe 2 (CO) 5 (μ‐bdt)(PPh 2 Me)] ( 3 ), [Fe 2 (CO) 4 (μ‐bdt)(PPh 2 Me) 2 ] ( 4 ), [Fe 2 (CO) 5 (μ‐bdt)(PPh 2 H)] ( 5 ) and [Fe 2 (CO) 4 (μ‐bdt)(PPh 2 H) 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: HClO 4 and CF 3 CO 2 H.