Stability of coordination compounds of Co2+ and Ni2+ ions with maleic acid anion in aqueous isopropanol solutions

Composition and stability of coordination compounds of nickel(II) and cobalt(II) ions with maleic acid anion in aqueous isopropanol solutions (H 2 O-IPA) of composition χ IPA = 0–0.5 mole fraction was studied by potentiometric titration at ionic strength of 0.1 maintained with sodium perchlorate at 298.15 K. Monoligand complexes of Ni 2+ and Co 2+ ions with maleic acid anion become stronger when isopropanol content rises. In the solvent of the studied composition, Co 2+ ions form less stable complexes than Ni 2+ ions that corresponds to the Irving-Williams series established for aqueous solutions. Variations in complex stability are more expressed at small IPA content and differ within experimental error at χ IPA = 0.5 mole fraction. Obtained results were compared with literature data for akin compounds.