Oxidative Dehydrogenation of Cu(II) Complexes with N-Aryl-N-2-hydroxybenzyl- and N-Aryl-N-2-hydroxynaphthylmethyleneamine Derivatives

The reactions of Cu²⁺, Co²⁺, and Ni²⁺ ions with N-phenyl-N-2-hydroxybenzyl- and N-phenyl-N-2-hydroxynaphthylmethyleneamine derivatives (HL ⁿ , n = 1–8) produced from the derivatives of aniline and aromatic -hydroxyaldehydes are studied. Among the ions studied, only Cu²⁺ forms stable complexes Cu(L ⁿ )₂ · 2H₂O. 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 · 2H₂O complexes are very small and range within 0.43–1.19 _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(L³)₂ · 2H₂O 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 HL ⁿ are shown to undergo oxidative dehydrogenation to form the corresponding metal salicyl-aldiminates. This reaction can occur on heating in the absence of oxygen and is accompanied by the Cu²⁺ Cu⁺ transition.