EPR spectroscopy was chosen to investigate the ligand exchange reactions between copper(II) bis(dithiocarbamate), Cu(dtc)(2), and copper(H) salts which proceeds with the formation of mixed-ligand complexes of the type Cu(dtc)X, where X = Cl, NO3, ClO4. Large concentrations of 1:1 mixed-ligand complexes of this type are obtained as indicated by the EPR spectra of acetone, CHCl3/EtOH, CHCl3/i-PrOH, CCl4/EtOH and CCl4/i-PrOH, solutions of Cu(dtc)(2) and the appropriate copper(IT) salt CuCl2, Cu(NO3)(2) or Cu(ClO4), Double integration of Cu(dtc)(2) EPR signals obtained at temperatures between 240 and 310 K affords the calculation of the equilibrium constant (K) of the reaction: Cu(dtc)(2) + CuX2 reversible arrow 2 Cu(dtc)X in all solvents as a function of T. From the values of K the stability constant beta of the mixed-ligand complexes has been derived. The error associated with the calculated stability constant is +/- 10%. Thermodynamic parameters (DeltaH(0), DeltaG(0) and DeltaS(0)) are determined from the temperature dependence of K as measured by EPR spectroscopy. (C) 2002 Elsevier Science B.V. All rights reserved.
