A Novel Nickel(II) Complex with 1,4-Dithia-8,11-diazacyclotetradecane Derivative as a Structural Model of the Nickel Site in [FeNi]-Hydrogenases

抄録

A new Ni(II) complex with 8-(2-pylidylmethyl)-1,4-dithia-8,11-diazacyclotetradecane ligand (P[14]aneN₂S₂), [NiP[14]aneN₂S₂(H₂O)](ClO₄)₂ (1), was prepared as a structural model of [FeNi] hydrogenase active site. The X-ray crystal structure analysis of the complex, in which the coordinated water molecule was replaced by Br^-, revealed an octahedral geometry coordinated with P[14]aneN₂S₂ and Br^-. The cyclic voltammograms of complex 1 gave only a reversible wave of Ni^2+/+ couple at E_1/2 = -920 mV vs. SCE in MeOH and two reversible waves of Ni^2+/+ and Ni^3+/2+couples at E_1/2 = -970 and 1350 mV vs. SCE in MeCN, respectively, indicating that complex 1 can take a wide range of oxidation states of nickel ion. The reduction of complex 1 with NaBH₄ in MeOH at -20 ℃ gave the Ni(I) complex with a hydride ion at the axial position, which was demonstrated by ESR spectroscopy.