Dinuclear and Mononuclear Iron(II)−Thiolate Complexes with Mixed CO/CN- Ligands: Synthetic Advances for Iron Sites of [Fe]-Only Hydrogenases

Abstract

The pentacoordinate, 16-electron FeII complex [PPN][Fe(CO)2(CN)(S,NH-C6H4)] (1), stabilized by strong S, N π-donation of chelating [S,NH-C6H4]2- ligand, was prepared by the reaction of 2-aminophenyl disulfide and [PPN][Fe(CO)4(CN)]. Protonation of complex 1 by electrophiles (2-mercaptopyrimidine and 2-aminophenylthiol) yielded hexacoordinate iron(II)−thiolate cyanocarbonyl complexes [PPN][Fe(CO)(CN)(S-C4H3N2)2] (5) and [PPN][Fe(CO)2(CN)(S-C6H4NH2)(S,NH2-C6H4)] (3), respectively. The IR spectrum of complex 5 in the aprotic solvent CH3CN displayed a weak ν(CN) band at 2090 cm-1 and a strong ν(CO) band at 1945 cm-1. Chemical oxidation of complex 5 in CH3CN at − 20 °C with [Cp2Fe][PF6] displayed absorption bands at 2096 and 1962 cm-1 which were assigned to the ν(CN) and ν(CO) vibrational frequencies respectively of the thermally unstable neutral FeIII(CO)(CN)(S-C4H3N2)2. Complex 5 was reobtained upon addition of [PPN][BH4] to FeIII(CO)(CN)(S-C4H3N2)2 in CH3CN at −20 °C. The first dinuclear Fe(II)−thiolate cya...