The di-iron carbonyl dithiolene bridged complex [Fe2(CO)6(µ-S2C2(CO2Me)2)] (1) reacts with 1 equivalent of phosphane PR3 (R = Ph, OMe) to give, as major products, monosubstituted derivatives [Fe2(CO)5L(µ-S2C2(CO2Me)2)] (L = PPh3 (2), P(OMe)3 (3)). In the presence of an excess (3–4 equiv.) of P(OMe)3, the cleavage of 1 arises partly and a mixture of the mononuclear species [Fe(CO)(P(OMe)3)2(κ2-S2C2(CO2Me)2)] (4) and 3 is obtained. The compounds 2–4 were analyzed by IR and 1H, 31P{1H} NMR spectroscopies. Their structures in solid state were determined by X-ray diffraction analyses, which accord with their spectroscopic characteristics.