Cleavage of Hg–C Bonds of Organomercurials Induced by Im^OHSe via Two Distinct Pathways

We show that the N-methylimidazole-based selone Im^OHSe having an N–CH₂CH₂OH substituent has the remarkable ability to degrade methylmercury by two distinct pathways. Under basic conditions, Im^OHSe converts MeHgCl into biologically inert HgSe nanoparticles and Me₂Hg via the formation of an unstable intermediate (MeHg)₂Se (pathway I). However, under neutral conditions, in the absence of any base, Im^OHSe 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 (Im^OHSe)₂HgCl₂ and Me₂Hg (pathway II). The initial rate of Hg–C bond cleavage of MeHgCl induced by Im^OHSe is almost 2-fold higher than the initial rate observed by Im^MeSe. Moreover, we show that Im^YSe (Y = OH, Me) has an excellent ability to dealkylate Me₂Hg at room temperature. Under acidic conditions, in the presence of excess Im^YSe, the volatile and toxic Me₂Hg further decomposes to the tetracoordinated mononuclear mercury compound [(Im^YSe)₄Hg]²⁺. In addition, the treatment of Im^OHSe with MeHgCys or MeHgSG in phosphate buffer (pH 8.5) afforded water-soluble Hg­(SeS) nanoparticles via unusual ligand exchange reactions, whereas its derivative Im^OMeSe or Im^MeSe, lacking the N–CH₂CH₂OH substituent, failed to produce Hg­(SeS) nanoparticles under identical reaction conditions.