Reactions of dinuclear Ni2 complexes [Ni(RNPyS4)]2 (RNPyS4 = 2,6-bis(2-mercaptophenylthiomethyl)-4-R-pyridine) with Fe(CO)3(BDA) (BDA = benzylidene acetone) leading to heterodinuclear NiFe and mononuclear Fe complexes related to the active sites of [NiFe]- and [Fe]-hydrogenases

Abstract

While the parent Ni₂ complex [Ni(RN_PyS₄)]₂ (1a, R = H; RN_PyS₄ = 2,6-bis(2-mercaptophenylthiomethyl)-4-R-pyridine) cannot react with Fe(CO)₃(BDA) in THF at room temperature, its substituted derivatives (1b, R = MeO; 1c, Cl; 1d, Br; 1e, i-Pr; 1f, BzO; 1g, MeS) have been found to react with Fe(CO)₃(BDA) under the same conditions to give the first [RN_PyS₄] ligand-containing heterodinuclear [NiFe]-hydrogenase model complexes NiFe(RN_PyS₄)(CO)₃ (2b, R = MeO; 2c, Cl; 2d, Br; 2e, i-Pr; 2f, BzO; 2g, MeS) along with the mononuclear [Fe]-hydrogenase model complexes Fe(RN_PyS₄)(CO) (3b, R = MeO; 3c, Cl; 3d, Br; 3e, i-Pr; 3f, BzO; 3g, MeS). However, when Ni₂ complexes 1a–1g react with Fe(CO)₃(BDA) in THF at the higher temperature of 40 °C, only the mononuclear complexes 3a–3g are obtained without the corresponding dinuclear complexes 2a–2g being isolated. While all the new complexes are characterized by elemental analysis and spectroscopy, the molecular structures of 1f, 2c, 3f and 3g have been further confirmed by X-ray crystallography. In addition, a possible pathway for the formation of 2a–2g and 3a–3g is suggested, which has been proved by monitoring the reaction course of dinuclear Ni₂ complex 1e with Fe(CO)₃(BDA) using in situ IR spectroscopy.