Cleavage of Hg-C Bonds of Organomercurials Induced by ImSe via Two Distinct Pathways.

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