15N, 13C and 1H NMR spectra of the 2:1 cobalt(III) complexes of some azo dyes

The 15N, 13C and 1H NMR spectra of 2:1 cobalt(III) complexes of azo dyes and their 15N isotopomers, derived from substituted 2‐hydroxyaniline azo coupling products with acetoacetanilide, were measured. It was found that, in contrast to precursors existing fully in their hydrazone forms, 2:1 cobalt(III) complexes exist in (E)‐azo configurations, cobalt being bound to oxygens which originate in hydroxy and amide groups and nitrogen from substituted anilines as starting material.