Solvent effect on the ligand exchange between bis(diethyldithiocarbamato)copper(II) and bis(diethyldiselenocarbamato)copper(II)

Abstract

EPR study on the products of ligand exchange taking place on mixing bis(diethyldiseleno-carbamato)copper(II), Cu(dsc) 2, and bis(diethyldithiocarbamato)copper(II), Cu(dtc) 2, solutions is reported. EPR spectra monitored at room temperature for 1 month period reveal a stable equilibrium among the parents (chromophores CuS 4 and CuSe 4) and the obtained mixed-chelate Cu(dtc)(dsc) complex (chromophore CuS 2Se 2) in heptane, hexane, benzene, toluene, acetone, DMFA, DMSO and dichloromethane. In CCl 4 and CHCl 3, two new additional EPR spectra appear attributed to the mixed-chelate complexes with chromophores Cu(SSe 3)S and Cu(S 3Se)S. The intensities of all five EPR spectra slowly decrease with the time in CHCl 3 after 1 month monitoring at room temperature, or one week at 60 °C whereas in CCl 4 only the spectrum of Cu(dtc) 2 remains at room temperature on keeping the sample solution for 1 week after mixing or 1 h at 60 °C. The reaction mechanism of formation of both additional complexes with chromophores Cu(SSe 3) and Cu(S 3Se) is discussed. It is assumed that the new mixed-chelates observed in CCl 4 and CHCl 3 are obtained in a reaction of Cu(dtc)(dsc) or Cu(dtc) 2 with the ester of diselenocarbamic acid which is formed in a parallel reaction of Cu(dsc) 2 with CCl 4 or CHCl 3.