Electrosynthesis at a sacrificial cathode

The electrolysis of halogen-containing organic compounds at a sacrificial cathode commonly produces homoleptic organometallic compounds. For example, the electrolysis of aqueous solutions of iodopropionitrile at a tin, lead, or mercury cathode yields respectively [Sn(CH2CH2CN)4], [Pb(CH2CH2CN)4l, or [Hg(CH2CH2CN)2]. The electrolysis of ethyl chloride or ethyl bromide at a lead cathode has been proposed as a mefiiod for ttie preparation of tetraethyllead.  

Organometallic compounds are formed during the electrochemical reduction of ketones in aqueous solution at a lead or mercury cathode. For example, [Hg(i-Pr)2] is formed by the reduction of the carbonyl group of acetone at a mercury cathode, Eq. 7.28  

There are few reports of the formation of metal complexes by the electrochemical reduction of aldehydes. Tedoradze has shown that the electrolysis of benzaldehyde at a mercury electrode produces 

Attempts to carry out similar reactions with a range of different aldehydes were unsuccessful. 

Organometallic compounds also may be formed by the dissolution of a metal cathode during the reduction of unsaturated organic compounds. Tomilov and Kaabak 04,105 have studied the reduction of acrylonitrile, H2C=CHCN, at a tin cathode in aqueous alkaline solution. Electrolysis produced [Sn(CH2CH2CN 4]. Other reactions that take place at sacrificial cathodes have been reviewed. Despite the long history of reactions that involve sacrificial cathodes, current ideas about the mechanisms of these reactions do not explain all aspects of the chemistry involved and have little predictive power. 

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