The one-electron cleavage and reductive homo-coupling of alkyl bromides at silver–palladium cathodes

Abstract

We have previously demonstrated that ‘‘palladized” silver electrodes obtained by displacement reaction, thanks to an immersion in acidic PdII-based solutions, display quite interesting capabilities in the cleavage of alkyl halides. Such chemically modified surfaces by an Ag–Pd alloy lead to large potential shifts compared to the use of glassy carbon or smooth silver cathodes as well. The present article now gives preliminary results focused on the particular electrochemical activity of primary and secondary alkyl bromides. Experimental data show that such electrodes may behave quite differently from smooth silver, especially, when acetonitrile and dimethylformamide are used as solvent. While smooth silver cathodes generally entail two-electron cleavage reactions, palladized silver interfaces always yield catalytic cleavages of C–Br bonds according to single one-electron reactions. The homo-coupling processes may generally occur with a rather high efficiency.