Effect of Ligand Conformation on the Reactivity of Copper(II) Complexes of Lawsone and its Derivatives

摘要

To comprehend the reactivity of copper(II) chelates of hydroxynaphthoquinones towards their #x2018;redox#x2019; nature, the oxidation reactions are studied. The N-bromosuccinimide (NBS) in chloroform is used as oxidizing agent. The reaction products are analysed by elemental analyses, ir, nmr, electronic and esr spectral studies. The stereospecificity of ligand C-3 substituents in chelates of lawsone, phthiocol and their oximes, govern two reaction mechanisms for NBS reactant viz. electrophilic substitution SEand free radical. In chelates of phthiocol and its oxime, the #x2018;oxidative#x2019; addition occurs in a unique way, by oxidation of the equatorial semiquinone ligand to a quinone rather than metal, with simultaneous axial addition of bromine on metal.