Benzothiazolylazo derivatives of some β-dicarbonyl compounds and their Cu(II), Ni(II) and Zn(II) complexes

Abstract

The coupling of diazotized 2-aminobenzothiazole with 1,3-dicarbonyl compounds (benzoylacetone, methyl acetoacetate and acetoacetanilide) yielded a new series of tridentate ligand systems (HL). Analytical, IR, 1H-NMR, 13C-NMR and mass spectral data indicated that the compounds exist in the intramolecularly hydrogen bonded azo-enol tautomeric form in which one of the carbonyl groups of the dicarbonyl moiety had enolised and hydrogen bonded to one of the azo nitrogen atoms. The compounds formed stable complexes with Ni(II), Cu(II) and Zn(II) ions. The Cu(II) complexes conform to [CuL(OAc)] stoichiometry while the Ni(II) and Zn(II) complexes are in agreement with [ML2] stoichiometry. Analytical, IR, 1H-NMR, 13C-NMR and mass spectral data of the complexes are consistent with the replacement of the chelated enol proton of the ligand with a metal ion, thus leading to a stable six-membered chelate ring involving a cyclic nitrogen, one of the azo nitrogens and the enolate oxygen. The Zn(II) chelates are diamagnetic while Cu(II) and Ni(II) complexes showed a normal paramagnetic moment.