Oxidative dehydrogenation of Cu(II) complexes with N-aryl-N-2-hydroxybenzyl- and N-aryl-N-2-hydroxynaphthylmethyleneamine derivatives

Abstract

The reactions of Cu2+ Cu2+, and Ni2+ ions with N-phenyl-N-2-hydroxybenzyl- and N-phenyl-N-2-hydroxynaphthylmethyleneamine derivatives (HLn, n = 1-8) produced from the derivatives of aniline and aromatic o-hydroxyaldehydes are studied. Among the ions studied, only Cu2+ forms stable complexes Cu(L-n)2 . 2H(2)O. The structures of the synthesized compounds are studied by IR, UV, and EPR spectroscopies and differential thermal analysis. The magnetic moments of the Cu(L-n)(2) . 2H(2)O complexes are very small and range within 0.43-1.19 mu(B), depending on the ligand structure, which indicates a strong antiferromagnetic interaction between the Cu2+ ions. The temperature dependence of the magnetic susceptibility measured for the Cu(L-3)(2) . 2H(2)O complex (where HL3 is N-4-methoxyphenyl-N-2-hydroxybenzylamine) is closest to the theoretical curve calculated for the binuclear Cu(II) complexes connected by the intermolecular exchange interaction. The Cu(II) complexes with HLn are shown to undergo oxidative dehydrogenation to form the corresponding metal salicylaldiminates. This reaction can occur on heating in the absence of oxygen and is accompanied by the Cu2+ --> Cu+ transition.