Organomercury compounds. XXVI. Thermal decomposition of mercuric 2,6-disubstituted benzoates

The main thermal decomposition path for mercuric 2,6-disubstituted benzoates, (RCO₂)₂Hg (R = 2,6-X₂C₆H₃; X = F, Cl, Br, or Me), can be varied considerably. In boiling dimethyl sulphoxide, decarboxylation occurs giving the corresponding diarylmercurial (X = F or Cl) or RHgO₂CR derivative (X = Me or Br). There is considerable competition from reaction of the mercuric salt with the solvent in the last three cases. With boiling pyridine as medium, the 2,6-difluorobenzoate yields a mixture of R₂Hg and RHgO₂CR derivatives, but the 2,6-dichlorobenzoate only gives (RCO₂)₂Hg(py)₂. Thermal decomposition of the mercuric benzoates under vacuum yields the carboxylic acids and complex mercuration products, mainly based on 3-mercurated 2,6-disubstituted benzoates, with partial additional mercuration and/or decarboxylation. Pyrolysis of mercuric 2,6-dichlorobenzoate at atmospheric pressure results in both mercuration and decarboxylation, giving m-dichlorobenzene as the main volatile product and a complex mercurial with 1,3-dimercurated-2,6-dichlorobenzene repeating units and 2,6-dichlorophenyl terminal groups.