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Abstract
The complexes of divalent manganese, cobalt, nickel, copper, zinc and the ligand pyridoxalisonicotinoyl hydrazone (PIH) are discussed in order to illustrate the behaviour of the ligand towards the metal ions in acidic and neutral media. The complexes [M(PIH-2H)(H2O)3] (M = Mn, Co and Zn), [Cu(PIH-2H)(H2O)2]2, [Cu(PIH)Cl(H2O)]2 2+ and [Ni(PIH)Cl2(H2O)] have distorted octahedral structures. The isostructural crystalline complexes, [M(PIH)C12]2 (M = Mn, Co and Zn) are isolated from hot solutions. The electronic spectral data of cobalt in conjunction with infrared, NMR and magnetic measurements enables the assignment of the formula [M(PIH)2][MCI4] to these complexes. The anion is tetra-hedral while the cation has an octahedral chromophore. Characterization data indicates that [Ni(PIH-2H)H2O] has a four-coordinated square-planar chromophore. The IR, 1H and 13C NMR spectral data indicate that PIH behaves as a neutral tridentate ligand in the chloro complexes and as a dinegative, tridentate species in the deprotonated complexes.
