Synthesis, characterization and electrochemical properties of aminophosphine monodentate, ‐chelate, and ‐bridge diiron bis(monothiolate) carbonyls

To develop the biomimetic chemistry of [FeFe]‐H2ases, three new aminophosphine substituted diiron bis(monothiolate) carbonyls were synthesized by reactions of [Fe2(μ‐SBn)2(CO)6] (Bn=CH2C6H5) with aryl‐substituted aminodiphosphine (PNP) ligand (Ph2P)2NC6H4‐4‐C≡CH under two different conditions. Treatment of them in the presence of Me3NO ⋅ 2H2O at room temperature gave PNP‐chelated complex [Fe2(μ‐SBn)2(CO)4{(κ2‐Ph2P)2N(C6H4‐4‐C≡CH)}] (2) together with unexpected aminophosphine monosubstituted complex [Fe2(μ‐SBn)2(CO)5{κ1‐Ph2PNH(NC6H4‐4‐C≡CH)}](1), while treatment of them in refluxing toluene gave PNP‐bridged complex [Fe2(μ‐SBn)2(CO)4{(μ‐Ph2P)2N(C6H4‐4‐C≡CH)}] (3) as the major product. Complex 1 has two isomers (1‐anti and 1‐syn), and chelate complex 2 is the isomer of bridge complex 3. The more interesting finding is that 1‐anti and 2 can be converted into 1‐syn and 3, respectively. Complexes 1–3 were well characterized by elemental analysis, FT‐IR, NMR spectroscopy, and X‐ray diffraction analyses. In addition, electrochemical and electrocatalytic properties of 1–3 were studied by cyclic voltammetry (CV).