Electrochemical extraction of Cu(I) and Cu(II) ions assisted by 1,4,7,10-tetrathiacyclododecane

The ion-transfer characteristics of Cu(I) acid Cu(II) were studied at the p olarized water/1,2-dichloroethane interface. Both direct ion transfer and t ransfer assisted by a cyclic thioether were investigated by voltammetric me asurements. In the case of Cu(I)/Cu(II) mixture, the assisted transfer of b oth species was observed. Nevertheless, when only Cu(II) was present in the aqueous phase, we noted the formation of a Cu(I)-ligand complex in the org anic phase if a reducing agent such as tetrakis(4-chlorophenyl)borate was p resent. The Cu(II)-transfer mechanism was then assigned to be an assisted t ransfer followed by a reduction. In the experiments where Cu(I) was the spe cies initially present in the aqueous phase, Cu2+ ions were formed from the disproportionation of Cu+ in the aqueous phase and thus the assisted trans fer of the doubly charged species as well as this of Cu+ were observed. The stoichiometry of the complex [Cu(I) - TTCD] was calculated to be equal to 1:1, and the corresponding association constant was determined at log K-1(o ) = 8.5 in 1,2-dichloroethane.