Metal complex formazans. Part I. The reaction of copper and cobalt salts with certain bi- and tri-dentate 1,3,5-triarylformazans

Abstract

The bidentate 1,3,5-triphenylformazan and the tridentate 1-(2-carboxyphenyl)-3,5-diphenyl- and 1-(2-hydroxyphenyl)-3,5-diphenyl-formazans are stoicheiometrically oxidised to the corresponding tetrazolium salts by cupric chloride in methanol. In the presence of air the oxidation of the bidentate formazan is catalytic. The latter compound is also oxidised by cupric acetate in methanol but the tridentate formazans react with this reagent to give copper(II) complexes having 1 : 1 stoicheiometry. 1,3,5-Triphenylformazan reacts with cobalt chloride in acetone to give a mixture of a novel cobalt(II) complex of the formazan and a tetrazolium salt. Under comparable conditions the tridentate formazans give cobalt(II) complexes having 2 : 1 stoicheiometry but again a proportion of the formazan is oxidised to tetrazolium salt. The significance of the results is discussed.