Allylmercury bromide

Hg. Allylmercury bromide and diallylmercury are both stable in water. They can allylate aldehydes in aqueous media but, in the case of allylmercury bromide, activation with tetrahexylammonium bromide was necessary.186 The allylation reaction is chemoselective towards aldehyde on the contrary, ketone compounds are unaffected. 

AUylations. This reagent or allylmercury bromide react with aldehydes in aqueous media. ... 

According to Bard and Merz [108], in MeCN containing TBAP, allyl bromide and allyl iodide interact chemically with a mercury electrode to form allylmercury halides. These allylmercury halides undergo reduction to yield diallylmercury, which is itself electroactive. Allyl bromide and allyl iodide are reduced at platinum in MeCN in a two-electron process to give the allyl anion, and the allyl radical is not involved as an intermediate. Reduction of allyl halides at platinum in DMF containing TEAOTs and in the presence of trimethylchlorosilane results in silylated compounds [100]. 

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