Mobilities and outer-sphere association with the perchlorate anion of some DMSO-solvated divalent transition metal cations

Abstract

Concentration dependences of the molar conductivity have been determined for Mn(ClO₄)₂, Co(ClO₄)₂, Ni(ClO₄)₂, Cu(ClO₄)₂ and Zn(ClO₄)₂ in dimethyl sulphoxide (DMSO), as well as in DMSO + benzene (mole fraction 0.3) mixtures, at 25 °C. Auxiliary absorption spectra determinations of the coloured metal perchlorates show that the metal cations in both media exist exclusively as M(DMSO)²⁺₆-type solvent complexes. The close similarity of the molar conductivity curves indicates that the same is also true for the other metal perchlorates. The limiting molar conductivities and the first step association constants are derived and are found to vary slightly within the Mn to Zn series of metals.