Heteroleptic cobalt(II) and nickel(II) complexes with iminodiacetic and dicarboxylic acids in aqueous solution

Equilibria in binary and ternary systems containing cobalt(II) and nickel(II) salts, iminodiacetic acid, and dicarboxylates were studied by spectrophotometry at I = 0.1 (NaClO₄) and T = 20 ± 2°C. The molar and proton compositions of the resulting complexes and the pH ranges of their existence were determined. The stability constants of the homo- and heteroleptic complexes were calculated. The pH-distribution of the detected complexes was obtained. The experimental data were analyzed using the mathematical models that predict the existence of a wide spectrum of complex species in solution and allow ignoring those species that are negligible for accurate reproduction of the observed pattern.