Six diiron ethanedithiolate complexes containing benzoate ester have been synthesized and characterized. Treatment of the starting material [{μ-SCH 2 CH(CH 2 OH)S}Fe 2 (CO) 6 ] (1) with benzoic acid in the presence of N,N′dicyclohexylcarbodiimide and 4-dimethylaminopyridine afforded the benzoate ester-containing complex [{μ-SCH 2 CH(CH 2 O 2 CPh)S}Fe 2 (CO) 6 ] (2) in 97% yield. Carbonyl substitution of complex 2 with a monophosphine ligand, such as triphenylphosphine, tris(2-methoxyphenyl)phosphine, tris(4-fluorophenyl) phosphine, isopropyldiphenylphosphine or cyclohexyldiphenylphosphine, in the presence of Me 3 NO⋅2H 2 O gave the derivatives [{μ-SCH 2 CH(CH 2 O 2 CPh)S} Fe 2 (CO) 5 L] (L = PPh 3 , 3; P(C 6 H 4 OCH 3 -2) 3 , 4; P(C 6 H 4 F-4) 3 , 5; Ph 2 PCH(CH 3 ) 2 , 6; Ph 2 PC 6 H 11 , 7) in 66-95% yields. Complexes 2-7 were characterized using elemental analysis, spectroscopy and X-ray diffraction analysis. In addition, these complexes can catalyze the reduction of protons to H 2 in the presence of weak acid HOAc under electrochemical conditions.