Cleavage of Hg-C Bonds of Organomercurials Induced by Im OH Se via Two Distinct Pathways.

We show that the N-methylimidazole-based selone ImOH Se having an N-CH2 CH2 OH substituent has the remarkable ability to degrade methylmercury by two distinct pathways. Under basic conditions, ImOH Se converts MeHgCl into biologically inert HgSe nanoparticles and Me2 Hg via the formation of an unstable intermediate (MeHg)2 Se (pathway I). However, under neutral conditions, in the absence of any base, ImOH Se facilitates the cleavage of the Hg-C bond of MeHgCl at room temperature (23 °C), leading to the formation of a stable cleaved product, the tetracoordinated mononuclear mercury compound (ImOH Se)2 HgCl2 and Me2 Hg (pathway II). The initial rate of Hg-C bond cleavage of MeHgCl induced by ImOH Se is almost 2-fold higher than the initial rate observed by ImMe Se. Moreover, we show that ImY Se (Y = OH, Me) has an excellent ability to dealkylate Me2 Hg at room temperature. Under acidic conditions, in the presence of excess ImY Se, the volatile and toxic Me2 Hg further decomposes to the tetracoordinated mononuclear mercury compound [(ImY Se)4 Hg]2+ . In addition, the treatment of ImOH Se with MeHgCys or MeHgSG in phosphate buffer (pH 8.5) afforded water-soluble Hg(SeS) nanoparticles via unusual ligand exchange reactions, whereas its derivative ImOMe Se or ImMe Se, lacking the N-CH2 CH2 OH substituent, failed to produce Hg(SeS) nanoparticles under identical reaction conditions.