Electrocatalytic potentialities of silver as a cathode for organic halide reductions

The peculiar halide affinity for silver results in an extraordinary electrocatalytic activity for the redn. of halides (either glycosyl halides or, more generally, aryl and alkyl halides). The most striking features are: (a) a redn. potential shift in the pos. direction of ∼1000 mV with respect to glassy carbon and 500 mV with respect to mercury; (b) a cage effect, evidenced in previous synthetic work concerning bromosugars, promoted by the halide acting as a bridge between the electrode surface and the reacting substrate, which mainly results in dimerization and/or addn. products. The above electrocatalytic effect is here studied by a systematic reactivity study on Ag, Hg and glassy carbon cathodes, with a variety of substrates. The effect of the supporting electrolyte is also analyzed in detail, providing a 1st inspection on specific halide/silver interactions in acetonitrile media.