ELECTROCHEMICAL STUDY OF THE ADSORPTION OF 2 ISOMERIC CHROMIUM(III) COMPLEXES ON MERCURY-ELECTRODES - THIOETHER AS AN ANCHORING GROUP

Cyclic voltammetry and chronocoulometry were utilized to examine the electrochemistry and adsorption on mercury of two isomeric complexes of Cr(III) with a multidentate ligand bearing a thioether group, thiobis(ethylenenitrilo) tetraacetic acid, S[CH2CH2N(CH2COOH)2]2. One isomer contains a sulfur-chromium bond and is exceedingly strongly adsorbed. The second isomer lacks this bond and is adsorbed much less strongly. Back-bonding from chromium to sulfur is argued to play an important role in the adsorption of the first isomer. Upon reduction, both isomers yield the same Cr(II) product. A dimeric form of the second isomer in which the two Cr(III) centers are bridged by an acetate group is proposed to form at certain pH values. The different coordination environments of the two Cr(III) centers in the dimer cause them to be reduced at different potentials. © 1979 Elsevier Sequoia S.A.