Synthesis and structural characterization of diiron azadithiolate complexes relevant to the active site of [FeFe] hydrogenases

摘要

Two N-functionally substituted diiron azadithiolate complexes, [(μ-SCH_2)_2NCH_2CH_2OC(O) C_6H_4I-p]Fe_2(CO)_6 (1) and {[(μ-SCH_2)_2NCH_2CH_2OC(O)C_6H_4I-p]Fe_2(CO)_5Ph_2PCH}_2 (2) as models for the active site of [FeFe] hydrogenases, have been prepared and fully characterized. Complex 1 was prepared by the reaction of [(u-SCH_2)_2NCH_2CH_2OH]Fe_2(CO)_6 with p-iodobenzoic acid in the presence of 4-dimethylaminopyridine (DMAP) and N,N'-dicyclohexylcarbodiimide (DCC) in 78% yield. Further treatment of 1 with 1 equiv. of Me_3NO.2H_2O followed by 0.5 equiv. of trans-1,2-bis(diphenyIphosphino)ethylene (dppe) affords 2 in 60% yield. The new complexes 1 and 2 were characterized by IR and ~1H (~(13)C, ~(31)P) NMR spectroscopic techniques and their molecular structures were confirmed by X-ray diffraction analysis. The molecular structure of 1 has two conformational isomers, in one isomer its N-functional substituent is axial to its bridged nitrogen and in the other isomer its N-functional substituent is equatorial. The crystal structure of 2 revealed that its N-functional substituents are equatorial to its nitrogens and dppe occupies the two apical positions of the square-pyramidal irons.