Electrochemical study of the assisted transfer of silver ion by 1,5-cyclooctadiene at the 1,6-dichlorohexane/water interface

The transfer of Ag+ ion across a polarized 1,6-dichlorohexane/water interface assisted by an alkene or olefin ligand, 1,5-cyclooctadiene (COD), was studied by cyclic voltammetry. Even if COD was absent from the organic phase, Ag+ ion gave a reversible voltammetric wave, and the formal potential of the non-assisted ion-transfer at the 1,6-dichlorohexane/water interface was determined from the reversible half-wave potential. By the addition of COD to the organic phase, the reversible half-wave potential shifted to more negative potentials with increasing concentration of COD. The concentration dependence of the half-wave potential revealed that the transfer of Ag+ ion is assisted by the formation of 1:1 and 1:2 Ag+-COD pi-complexes in 1,6-dichlorohexane with overall formation constants of (2.1 +/- 0.2) x 10(3) M(-1) and (7.8 +/- 1.0) x 10(3) M(-2), respectively. The formal potential and the formation constants coincide well with those obtained by the potentiometry of Ag+ ion in aqueous and organic media with a Ag electrode.