CHARACTERIZATION OF COPPER(II), NICKEL(II), COBALT(II) AND PALLADIUM(II) COMPLEXES OF VICINAL OXIME-IMINE LIGANDS - INDUCED CHELATE ISOMERISM IN THE SAME MOLECULE OF THE NICKEL(II) COMPLEX

Metal complexes of the title ligands were characterized in order to determine the factors influencing the stability of chelate isomerism in the same molecule. The ligands were prepared by 1:1 condensation of isonitrosoacetylacetone (Hiso) with either o-aminophenol (H(2)isoaph), p-aminophenol (H(2)isopph), or aniline (Hisoanil). The following complexes have been synthesized: [(isoaph)Cu](4), (Hisoaph)(2)Co, (Hisopph)(2)M . H2O (M = Ni(II), N = 2; M = Pd(II), n = 0; M = Co(II), n = 2), [(isopph) Cu . H2O](2), and (isoanil)(2)M (M = Ni(II), Cu(II), Co(II), or Pd(II)). Both chelate rings in these metal complexes are five-membered. Transimination of one -C=N-C6H5 group to -C=NH in (isoanil)(2)Ni produced a six-membered chelate ring in (isoim)Ni(isoanil). The induced chelate isomerism is ascribed to intermolecular hydrogen bonding of the imino-hydrogen and the basic nitrogen of the same six-membered chelate ring of an adjacent square planar molecule. Other types of hydrogen bondings with the oximato oxygen (intra- or intermolecular) favour the formation of five-membered chelate rings. Analytical, spectroscopic, and magnetic moment data are in accordance with the suggested formulations.