Heterodinuclear nickel(ii)–iron(ii) azadithiolates as structural and functional models for the active site of [NiFe]-hydrogenases

To develop the biomimetic chemistry of [NiFe]-H(2)ases, the first azadithiolato-bridged NiFe model complexes [CpNi{(μ-SCH(2))(2)NR}Fe(CO)(diphos)]BF(4) (5, R = Ph, diphos = dppv; 6, 4-ClC(6)H(4), dppv; 7, 4-MeC(6)H(4), dppv; 8, CO(2)CH(2)Ph, dppe; 9, H, dppe) have been synthesized via well-designed synthetic routes. Thus, treatment of RN[CH(2)S(O)CMe](2) with t-BuONa followed by reaction of the resulting intermediates RN(CH(2)SNa)(2) with (dppv)Fe(CO)(2)Cl(2) or (dppe)Fe(CO)(2)Cl(2) gave the N-substituted azadithiolato-chelated Fe complexes [RN(CH(2)S)(2)]Fe(CO)(2)(diphos) (1, R = Ph, diphos = dppv; 2, 4-ClC(6)H(4), dppv; 3, 4-MeC(6)H(4), dppv; 4, CO(2)CH(2)Ph, dppe). Further treatment of 1–4 with nickelocene in the presence of HBF(4)·Et(2)O afforded the corresponding N-substituted azadithiolato-bridged NiFe model complexes 5–8, while treatment of 8 with HBF(4)·Et(2)O resulted in formation of the parent azadithiolato-bridged model complex 9. While all the new complexes 1–9 were characterized by elemental analysis and spectroscopy, the molecular structures of model complexes 6–8 were confirmed by X-ray crystallographic study. In addition, model complexes 7 and 9 were found to be catalysts for H(2) production with moderate i(cat)/i(p) and overpotential values from TFA under CV conditions.