Synthesis and characterization of mixed-ligand nickel(II) chelates of beta-diones and alpha-diimines. Crystal and molecular structure of (Ni(ncup)(2)Etacet]ClO4

摘要

A series of new nickel(II) perchlorate complexes containing an alpha-diimine(enR) and the anion of a beta-dione (1,3-ketoenol or 1,3-ketoester, beta H) was prepared and characterized. The composition and the overall structure of the new chelates depend on ligand concentration, on steric and electronic effects induced by substituents within the ligands and the ability of the perchlorate group to coordinate. The IR and electronic excitation spectra of [Ni(enR)(2)beta]ClO4 and [Ni(enR)beta(O2ClO2)] indicate, in conjunction with other physicochemical measurements, bidentate coordination of the ligands and replacement of the (O,O') perchlorato group by basic solvents. The structure of the new chelates was further supported by an X-ray structure analysis of [Ni(ncup)(2)Etacet]ClO4, where ncup denotes neocuproine and Etacet the anion of the ethyl acetoacetate (orthorhombic, space group Pc2(1)n, a = 14.087(5), b = 14.713(5) and c = 15.952(5) Angstrom, Z = 4). The coordination sphere of nickel is a distorted octahedron, arised from the chromophore NiN4O2, in which the base is favored by three neocuproine nitrogens and one Etacet oxygen. The apical sites are occupied by the remaining oxygen and nitrogen atoms, one from Etacet and one from neocuproine respectively. [References: 46]