Protolytic Cleavage of Hg–C Bonds Induced by 1‑Methyl-1,3-dihydro‑2H‑benzimidazole-2-selone: Synthesis and Structural Characterization of Mercury Complexes

Multinuclear (¹H, ⁷⁷Se, and ¹⁹⁹Hg) NMR spectroscopy demonstrates that 1-methyl-1,3-dihydro-2H-benz­imid­azole-2-selone, H­(sebenz­im^Me), a structural analogue of the seleno­amino acid, selenoneine, binds rapidly and reversibly to the mercury centers of HgX₂ (X = Cl, Br, I), while X-ray diffraction studies provide evidence for the existence of adducts of composition [H­(sebenz­im^Me)]_xHgX₂ (X = Cl, x = 2, 3, 4; X = I, x = 2) in the solid state. H­(sebenz­im^Me) also reacts with methyl­mercury halides, but the reaction is accompanied by elimination of methane resulting from protolytic cleavage of the Hg–C bond, an observation that is of relevance to the report that selenoneine demethylates CysHgMe, thereby providing a mechanism for mercury detoxification. Interestingly, the structures of [H­(sebenz­im^Me)]_xHgX₂ exhibit a variety of different hydrogen bonding patterns resulting from the ability of the N–H groups to form hydrogen bonds with chlorine, iodine, and selenium.