Stability Constants of Nickel(II) Complexes with [2.2.2]Cryptand in Aqueous Ethanol Solutions

Abstract

The stability constants of nickel(II) complexes with [2.2.2]cryptand in aqueous ethanol solutions with a variable concentration of the organic co-solvent were determined by potentiometry at Т = 298 K and µ → 0. It was found that mononuclear, binuclear, and protonated nickel(II) cryptates can form in solution, whose stability increases with the ethanol content. The Gibbs energies of nickel(II) ion transfer from water to the aqueous ethanol solvent were calculated using published data. The contributions of resolvation of reagents in water–ethanol mixtures to the change in the stability of nickel(II) complexes with [2.2.2]cryptand were evaluated.