Homo- and heteroleptic cobalt(II) and nickel(II) complexes with nitrilotriacetic and dibasic carboxylic acids

Equilibria in binary and ternary systems containing cobalt(II) and nickel(II) salts, nitrilotriacetic acid, and dicarboxylates were studied by spectrophotometry with NaClO 4 as a supporting electrolyte (I = 0.1) at T = 20 ± 2°C. The molar and proton compositions of the 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 processed in terms of 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.