Oxidation processes at mercury electrodes for tetraphenyllead and related compounds in dichloromethane

Two oxidation waves are observed at mercury electrodes for tetraphenyllead in dichloromethane. The mechanisms of the oxidation processes have been investigated by dc and differential pulse polarography. The first wave is a broad two-electron step and represents the summation of a number of processes related to mercury exchange and halide abstraction. The exchange reactions are as follows: 2 Φ₄Pb + Hg→2Φ₃Pb⁺ + Φ₂Hg+2e^- 2 Φ₃Pb⁺ + Hg→2Φ₂Pb²⁺ + Φ₂Hg+2e^- Dichloroethane and HgCl₂ are identified as products of controlled potential electrolysis experiments as well as Φ₂Hg and Φ₂PbCl₂ implying that the coordinatively unsaturated Φ₃Pb⁺ and/or Φ₂Pb²⁺ react with the solvent dichloromethane and abstract chloride. The second oxidation process is the two electron step. Φ₂Hg+Hg→2 ΦHg⁺ + 2e^-. Tetraalkyllead compounds (tetramethyl, tetraethyl, tetrabutyl) also give rise to related electrode processes at mercury electrodes and polarographic techniques may form the basis of a method for their analytical determination if separated chromatographically prior to detection.