Synthesis, characterization, and electrochemistry of monophosphine-containing diiron propane-1,2-dithiolate complexes related to the active site of [FeFe]-hydrogenases

Five monophosphine-substituted diiron propane-1,2-dithiolate complexes as the active site models of [FeFe]-hydrogenases have been synthesized and characterized. Reactions of complex [Fe-2(CO)(6){mu-SCH2CH(CH3)S}] (1) with a monophosphine ligand tris(4-methylphenyl)phosphine, diphenyl-2-pyridylphosphine, tris(4-chlorophenyl)phosphine, triphenylphosphine, or tris(4-fluorophenyl)phosphine in the presence of the oxidative agent Me3NO center dot 2H(2)O gave the monophosphine-substituted diiron complexes [Fe-2(CO)(5)(L){mu-SCH2CH(CH3)S}] [L = P(4-C6H4CH3)(3), 2; Ph2P(2-C5H4N), 3; P(4-C6H4Cl)(3), 4; PPh3, 5; P(4-C6H4F)(3), 6] in 81%-94% yields. Complexes 2-6 have been characterized by elemental analysis, spectroscopy, and X-ray crystallography. In addition, electrochemical studies revealed that these complexes can catalyze the reduction of protons to H-2 in the presence of HOAc.