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 {μ-SCH 2 CH(CH 3 )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 Me 3 NO·2H 2 O gave the monophosphine-substituted diiron complexes [Fe 2 (CO) 5 (L){μ-SCH 2 CH(CH 3 )S}] [L = P(4-C 6 H 4 CH 3 ) 3 , 2 ; Ph 2 P(2-C 5 H 4 N), 3 ; P(4-C 6 H 4 Cl) 3 , 4 ; PPh 3 , 5 ; P(4-C 6 H 4 F) 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.