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Oxidative dehydrogenation of N-(2-hydroxy-3,5-R1,R2-benzyl)-4-aminoantipyrines in the complexation reaction

Research paper by A. A. Medzhidov, P. A. Fatullaeva, S. M. Peng, R. G. Ismaiylov, G. H. Lee, S. R. Garaeva

Indexed on: 15 Feb '12Published on: 15 Feb '12Published in: Russian Journal of Coordination Chemistry



Abstract

Reactions of N-(2-hydroxy-3,5-R1,R2-benzyl)-4-aminoantipyrines with copper acetate in ethanol gave complexes with Schiff bases (SBs) rather than the expected complexes with reduced SBs; i.e., the starting ligands undergo oxidative dehydrogenation during the complexation reaction. The corresponding complexes with reduced SBs were obtained from sodium salts of the ligands and cupric sulfate in aqueous solutions. Kinetic measurements showed that oxidative dehydrogenation occurs in the heteroleptic complexes Cu(Li)(CH3COO)(X) (LiH are derivatives of N-(2-hydroxy-3,5-R1,R2-benzyl)-4-aminoantipyrines; i = 6–10; X = H2O, CH3OH, CH3CH2OH) but does not occur in the complexes CH3OH, CH3CH2OH. The absence of oxidative dehydrogenation of the ligands in Cu(Li)2 · H2O can be explained by the octahedral environment of the Cu2+ ion and, accordingly, the absence of the coordination site for molecular oxygen. The molecular structures of two Cu(II) complexes with SBs were determined by X-ray diffraction.