The Exchange of Metal Ions with Quadridentate Complexes. I. The Effects of Metal Salts and Solvents

Abstract

The rate of replacement of nickel by copper ions from NN'-ethylenebis(salicylideneiminato)nickel(II) has been found to depend on the copper salt used in the reaction, the rate decreasing in the order Cu(ClO₄)₂ > CuCl₂ > Cu(CH₃C00)₂ in 2-methoxyethanol at 70°. The position of equilibrium also varies with the salt used, the percentage exchange decreasing Cu(ClO₄)₂ > Cu(CH₃OO)₂ > CuCl₂. The rate data are explained by assuming a bimolecular reaction step involving copper ions reacting with a partly dissociated nickel complex. The positions of equilibrium are related to the competition for copper and nickel ions by anions in solution as well as the quadridentate ligand. The rate of reaction is also dependent on the solvent used, increasing with increase in dielectric constant. This is taken as evidence that a preliminary dissociation of at least one nickel-ligand bond is of importance in the overall exchange process.