Philippe Schollhammer

Two complexes, related to the active site of [FeFe]-hydrogenases, [Fe2(CO)4(κ2-pma)(µ-bdt)] (1) and [Fe2(CO)4(κ2-pma)(µ-pdt)] (2) (bdt = benzene-1,2-dithiolate, pdt = propane-1,2-dithiolate) featuring the diaza chelate ligand trans-N-(2-pyridylmethylene)aniline (pma) were prepared, in order to study the influence of such a redox ligand, potentially non-innocent, on their redox behaviours. Both complexes were synthesized by photolysis in moderate yields, and they were characterized by IR, 1H and 13C{1H} NMR spectroscopies, elemental analyses and X-ray diffraction. Their electrochemical study by cyclic voltammetry, in the presence and in the absence of protons, revealed different behaviours depending on the aliphatic or aromatic nature of the dithiolate bridge. Density functional theory (DFT) calculations showed the role of the pma ligand as an electron reservoir, allowing the rationalization of the proton reduction process of complex 1.

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.