LIGAND BRIDGING BY HALIDE IN ELECTROCHEMICAL OXIDATION OF CHROMIUM(2) AT MERCURY ELECTRODES

A variety of electrochemical techniques was employed to investigate the mechanism of oxidation of chromium(II) at mercury electrodes in the presence of chloride, bromide, and iodide. The results show that halide catalyzes the reaction and leads to halide-containing Cr(III) products according to X- + Cr(II) ⟶ CrX2+ + e-. In the case of chloride and bromide at least, the homogeneous complexation reaction to form CrX- does not precede the electrode reaction. A variety of data on the potential dependence of the reaction products strongly suggests that, when it is adsorbed on the electrode, halide can act as an electron bridge and facilitate the oxidation. We conclude that the halide-catalyzed pathway is best represented by the scheme [formula ommitted]. © 1969, American Chemical Society. All rights reserved.