Schiff base complexes of cobalt(II)

Abstract

Nickel(II)acetate reacts with 2-{ [ (3-hydroxypropyl)imino ]methyl} phenol in acetonitrile to give a tetranuclear complex, previously thought to be a trimer. Cobalt(II) sometimes gives complexes which are analogous to those of nickel(II). This thesis involved the synthesis of cobalt(II)complexes with 2-{[ (3-hydroxypropyl)imino ]methyl} phenol and derivatives (napthtol and dibromo derivatives) under the same conditions of the above mentioned reaction. Dimethylsalicylaldehyde was also synthesized in an attempt to produce the dimethyl substituted ligand. Products obtained from the reactions with cobalt(II) were analysed by IR, UV and when possible, NMR, and compared to those obtained for nickel(II) in previous studies, taking into consideration recent X-ray studies conducted on the nickel(II) complexes. The reaction was also carried out using copper(II) acetate to find out if this gives the same products. The effect of altering the reaction conditions was further investigated by changing the cobalt(II) salt and solvent. Thus, the reaction of cobalt(II)tetrafluoroborate and 2-{[(3 hydroxypropyl)imino]methyl}phenol in absolute ethanol was found to give different products, again interpreted with respect to the analogous reaction with nickel(II) salts. Research was carried out to find a column chromatographic method to separate multinuclear complexes formed during the reaction. NMR spectra of the complexes of nickel(II) and cobalt(II) acetate with 2-{[(3 hydroxypropyl)imino]methyl}phenol in acetonitrile were studied to separate the contact and pseudocontact contribution to the chemical shift. IR spectra indicated that the ligand was coordinated to the metal. UV spectra did not yield information about "d-d" transitions, because ligand transitions were much more intense and fell in the same region of absorption as did the "d-d" transitions. NMR spectra indicated the paramagnetic nature of the complexes, and strengthened the idea that mixtures were being produced in the reactions.