Synthetic and structural studies on new diiron azadithiolate (ADT)-type model compounds for active site of [FeFe]hydrogenases

A series of new diiron azadithiolate (ADT) complexes (1–8), which could be regarded as the active site models of [FeFe]hydrogenases, have been synthesized starting from parent complex [(μ-SCH2)2NCH2CH2OH]Fe2(CO)6 (A). Treatment of A with ethyl malonyl chloride or malonyl dichloride in the presence of pyridine afforded the malonyl-containing complexes [(μ-SCH2)2NCH2CH2O2CCH2CO2Et]Fe2(CO)6 (1) and [Fe2(CO)6(μ-SCH2)2NCH2CH2O2C]2CH2 (2). Further treatment of 1 and 2 with PPh3 under different conditions produced the PPh3-substituted complexes [(μ-SCH2)2NCH2CH2O2CCH2CO2Et]Fe2(CO)5(PPh3) (3), [(μ-SCH2)2NCH2CH2O2CCH2CO2Et]Fe2(CO)4(PPh3)2 (4), and [Fe2(CO)5(PPh3)(μ-SCH2)2NCH2CH2O2C]2CH2 (5). More interestingly, complexes 1–3 could react with C60 in the presence of CBr4 and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) via Bingel–Hirsch reaction to give the C60-containing complexes [(μ-SCH2)2NCH2CH2O2CC(C60)CO2Et]Fe2(CO)6 (6), [Fe2(CO)6(μ-SCH2)2NCH2CH2O2C]2C(C60) (7), and [(μ-SCH2)2NCH2CH2O2CC(C60)CO2Et]Fe2(CO)5(PPh3) (8). The new ADT-type models 1–8 were characterized by elemental analysis and spectroscopy, whereas 2–4 were further studied by X-ray crystallography and 6–8 investigated in detail by DFT methods.