Reversible oxidation processes in dichloromethane for triethyl-, diethyl-, trimethyl-, and dimethyllead compounds at mercury electrodes

A. M. Bond, N. M. McLachlan

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Abstract

Chemically reversible electrochemical oxidation processes have been observed at mercury electrodes in dichloromethane in the presence of Et3PbOAc (OAc- = acetate), Et3PbCl, Et2PbCl2, Me3PbOAc, Me3PbCl and Me2PbCl2. The trialkyl derivatives R3PbX (R Et, Me; X- OAc-, Cl-) give rise to a reversible oxidation process involving transfer of one electron, exchange of alkyl groups and X- and formation of a mercury-lead complex, which in its simplest form can be represented as [R3PbHgPbR3]2+. The oxidation process is therefore described by the equation 2 R3PbX + 2 Hg ⇌ [R3PbHgPbR3]2+ + HgX2 + 2 e- On the longer time scale of controlled potential electrolysis, HgX2 can react with R3PbX and presumably [R3PbHgR3Pb]2+ to produce RHgX, inorganic lead(II) and electroactive R2PbX2. The dialkyl complexes R2PbX2 exhibit analogous oxidation processes of the kind 2 R2PbX2 + 2 Hg ⇌ [R2XPbHgPbXR2]2+ + HgX2 + 2 e- with short time domain experiments. However HgX2 reacts with [R2XPbHgPbXR2]2+ and R2PbX2 on longer time domain experiments such as controlled potential electrolysis or dc polarography to generate inorganic lead(II) and RHgX. The existence of reversible polarographic processes implies that it may be possible to develop extremely sensitive analytical methods for the determination of these toxic and environmentally significant compounds based on procedures incorporating (i) extraction into non-polar solvents, (ii) high performance liquid chromatography and (iii) electrochemical oxidative detection without the need to remove oxygen as is required when using previously described reduction processes.

Original languageEnglish
Pages (from-to)197-211
Number of pages15
JournalJournal of Electroanalytical Chemistry
Volume218
Issue number1-2
DOIs
Publication statusPublished - 25 Feb 1987

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