Spectrophotometric investigations of the complexation between Ni(II) and thiocyanate in aqueous methanol

Abstract Ni(II) adds up to three thiocyanate ligands per cation in water and aqueous methanol. All three of the observed complexes are green, the color characteristic of free Ni(II) perchlorate, consistent with the absence of any geometry change occurring upon complexation. Equilibrium constants were obtained as a function of temperature and solvent composition. Because the magnitude of the third complex was significantly lower than for the first two species, the Benesi–Hildebrand method was used to measure the third complexation constant.