Ligand rearrangement and oxidation during preparation of diiron hydrogenase active site models [(μ-SCH2)2NCH2CO2Me]Fe2(CO)5(Ph2PNHPy-4) and [(μ-SCH2)2NCH2CO2Me]Fe2(CO)5[Ph2PP(O)Ph2]

Reaction of [(μ-SCH2)2NCH2CO2Me]Fe2(CO)6 with 4-PyN(PPh2)2 (Py = C5H4N) in the presence of the decarbonylating agent Me3NO·2H2O afforded unexpected complexes [(μ-SCH2)2NCH2CO2Me]Fe2(CO)5(Ph2PNHPy-4) (1) and [(μ-SCH2)2NCH2CO2Me]Fe2(CO)5[Ph2PP(O)Ph2] (2) in 40% and 14% yields, respectively. The new complexes 1 and 2 have been characterized by elemental analysis, IR and 1H (31P, 13C) NMR spectroscopic techniques. In addition, their structures were determined by single-crystal X-ray diffraction analysis, indicating that the monophosphine ligands in complexes 1 and 2 both reside in an axial position of the square-pyramidal coordination sphere of the Fe atoms.