Novel reactions of homodinuclear Ni2 complexes [Ni(RNPyS4)]2 with Fe3(CO)12 to give heterotrinuclear NiFe2 and mononuclear Fe complexes relevant to [NiFe]- and [Fe]-hydrogenases

Abstract

The homodinuclear complexes [Ni(RN_PyS₄)]₂ (1a–1e; RN_PyS₄ = 2,6-bis(2-mercaptophenylthiomethyl)-4-R-pyridine; R = H, MeO, Cl, Br, i-Pr) were found to be prepared by reactions of the in situ generated Li₂[Ni(1,2-S₂C₆H₄)₂] with 2,6-bis[(tosyloxy)methyl]pyridine and its substituted derivatives 2,6-bis[(tosyloxy)methyl]-4-R-pyridine. Further reactions of 1a–1e with Fe₃(CO)₁₂ gave both heterotrinuclear complexes NiFe₂(RN_PyS₄)(CO)₅ (2a–2e) and mononuclear complexes Fe(RN_PyS₄)(CO) (3a–3e), unexpectedly. Interestingly, complexes 2a–2e and 3a–3e could be regarded as models for the active sites of [NiFe]- and [Fe]-hydrogenases, respectively. All the prepared complexes were characterized by elemental analysis, spectroscopy, and particularly for some of them, by X-ray crystallography. In addition, the electrochemical properties of 2a–2e and 3a–3e as well as the electrocatalytic H₂ production catalyzed by 2a–2e and 3a–3e were investigated by CV techniques.