Silver as a powerful electrocatalyst for organic halide reduction: the critical role of molecular structure

The remarkable electrocatalytic properties of silver for organic halide red uctions, related to its strong specific interactions with halide ions, and therefore modulated by the surface state and by the nature of the supportin g electrolyte, have been shown by us recently. The key role played by the m olecular structure is now described together with its effect on the reactio n pathway, in terms of not only the intrinsic (RX)-X-... reactivity modific ation but also of elements connected to the heterogeneous nature of the pro cess, including the accessibility of the leaving group and the possible pre sence of adsorption auxiliary groups stabilizing the postulated (RXMe)-X-.. .-Me-... intermediate. The present discussion is supported by: (a) cyclovol tammetric investigations on a wide set of aliphatic and aromatic halides pe rformed on silver, mercury and glassy carbon; and (b) a systematic program of preparative electroreductions carried out on variously configurated halo adamantanes in different operating conditions. The haloadamantane case, yie lding a mixture of adamantane and dimers in a ratio heavily affected by the operating conditions, is very appropriate for an elucidation of the factor s favouring monoelectronic dimerisation versus bielectronic halogen replace ment by hydrogen. (C) 2001 Elsevier Science Ltd. All rights reserved.