ChemInform Abstract: COMPLEX FORMATION AND SOLVATION OF (CUCLN)(2‐N)+ IN ACETONITRILE AND IN N,N‐DIMETHYLFORMAMIDE

Abstract

Complex formation equilibria between copper(II) and chloride ions have been studied by calorimetry and spectrophotometry in acetonitrile(AN) containing 0.1 mol dm−3 (C2H5)4NClO4 as a constant ionic medium at 25 °C. Both calorimetric and spectrophotometric titration curves could be well explained in terms of formation of a series of four mononuclear complexes, [CuCln](2−n)+ (n=1–4), and formation constants, enthalpies and entropies of formation of the complexes were determined. Stepwise enthalpies ΔHn° (n=1–4) were all negative, the ΔH4° value being especially largely negative. On the other hand, the stepwise entropy ΔSn° was largely positive for n=1–3, but largely negative for n=4. The result suggested that solvation of the [CuCl3]− complex was extremely weak in AN and that release of solvent molecules from [CuCl3]− was not so significant that the enthalpy and entropy of formation of [CuCl4]2− were mainly attributable to those of desolvation of Cl− followed by a bond formation between the [CuCl3]− complex...