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

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.