Solvent effect on complexation reactions

Abstract

The solvent nature plays a critical role in stabilizing the complexation process. Several models were used for describing the solvent–solute interactions in complex reactions. One form of such interactions is classical Lewis type donor–acceptor interactions. Another type of interactions is the so-called “soft–soft” interactions, where both partners can donate and accept electron pairs. This concept states that “hard’ acids prefer to associate with “hard” bases and “soft” acids with “soft” bases. In addition, the solvating ability of the solvent, as expressed by the Guttmann donocity scale (DN: donor number), plays a fundamental role in the complexation reaction. This scale is based on the enthalpy of the reaction between solvent and SbC15 in dilute 1,2-dichloroethane solution. Furthermore, the coordination power (CP), a measure of a solvent’s donor ability, is related to the Gibbs free energy change on the solvation of nickel (II) ion. Coordination power for a solvent is the difference in the stability constant between hexa (solvento)-nickel (II) ion and hexa (acetonitrile) nickel (II) ion and is subsequently related to the relative Gibbs free energy change for solvation of the nickel (II) ion. This Review is focused on the effect of solvent on the complex reactions and how these models can explain this behavior.