Molar gibbs (free) energies of transfer for barium(II) and mercury(II) from acetonitrile into nonaqueous solvents

Abstract

Molar Gibbs energies of transfer for Ba 2+ and Hg 2+ were calculated from electrochemical data on the basis of the bis(biphenyl)chromium assumption for 21 solvents. The transfer data obtained for these cations could be separated into two groups according to the HSAB principle. One group consisted of systems, where both cation and solvent were capable of undergoing soft-soft interactions, the other group of systems where either the solvent or the cation or both lacked the ability for soft interactions. Within each of these two groups it was found that the Gibbs energies of transfer for Ba 2+ and Hg 2+ depended on each other as well as on the Gibbs energies of transfer of Ag +. A variety of solvent parameters were evaluated with respect to their ability to account for the Gibbs energies of transfer for Ba 2+ and Hg 2+ into hard and soft solvents. For solvent systems, which exclude soft-soft interactions, the Gibbs energies of transfer for Ba 2+ and Hg 2+ can be correlated with traditional solvent parameters such as the donor number, the B and the β parameter. Soft-soft interactions between cations and solvents can be represented by the SP parameter. A linear correlation between the Gibbs energies of transfer of the soft Hg 2+ ion and the shifts in the HgBr stretching frequencies ( D s parameter) was observed for all solvents.