Diiron Complexes [Fe2(CO)5(μ‐pdt/Mebdt)(L)] Containing a Chelating Diphosphine Ligand L=(Oxydi‐2,1‐phenylene)bis(diphenylphosphine): Bioinspired [FeFe] Hydrogenase Model Complexes

Abstract Diiron carbonyl complexes [Fe2(CO)5(μ‐pdt)(κ1‐L)] 1 and [Fe2(CO)5(μ‐Mebdt)(κ1‐L)] 3 were obtained in moderate yields from the parent complexes [Fe2(CO)6(μ‐pdt)] and [Fe2(CO)6(μ‐Mebdt)] and the chelating diphosphine ligand, L=(Oxydi‐2, 1‐phenylene)bis(diphenylphosphine). In addition, complexes [Fe2(CO)5(μ‐pdt)(κ1‐LO)] 2 and [Fe2(CO)5(μ‐Mebdt)(κ1‐LO)] 4 containing oxidized phosphine (P=O) were obtained as side products of the reaction. In all the four complexes only one phosphorus site of the diphosphine ligand was found to coordinate to the metal center. X‐ray crystal structures have been reported for complexes 1, 3 and 4. Complexes 1, 3 and 4 were investigated for electrocatalytic proton reduction in the presence of acetic and trifluoroacetic acid. Complexes 3 and 4 showed higher acid‐induced currents than 1 when investigated with both the acids. The over potentials for the three complexes were however, on the higher side. Moreover, complex [Fe2(CO)5(μ‐Mebdt)(κ1‐LO)] 4 with oxidized phosphine was catalytically more efficienct than [Fe2(CO)5(μ‐Mebdt)(κ1‐L)] 3 without oxidized phosphine.