Synthesis and Crystal Structures of Diiron Dithiolate Complexes Containing Diphosphine Ligands

As the active site model of [FeFe]-hydrogenases, complexes [(μ-PDT)Fe2(CO)5]2(dppb) (PDT = SCH2CH2CH2S, dppb = Ph2PCH2CH2CH2CH2PPh2) (1) and [(μ-SCH2)2NCH2CO2Me]Fe2(CO)5(dppm) (dppm = Ph2PCH2PPh2) (2) were prepared by reactions of (μ-PDT)Fe2(CO)6 (A) or [(μ-SCH2)2NCH2CO2Me]Fe2(CO)6 (B) with dppb or dppm in the presence of the decarbonylating agent Me3NO∙2H2O in MeCN at room temperature. Complex 1 was characterized by elemental analysis, IR, and 1H (31P, 13C) NMR spectroscopic techniques. In addition, the molecular structures of 1 and 2 have been confirmed by single crystal X-ray diffraction analysis. In the crystal structure of 1, two phosphorus atoms of dppb reside in a basal position of the square-pyramidal coordination sphere of the Fe2 and Fe3 atoms. However, in the crystal structure of 2, P1 atom of dppm resides in an apical position of the square-pyramidal coordination sphere of the Fe2 atom.