Cleaving Mercury-Alkyl Bonds: A Functional Model for Mercury Detoxification by MerB

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Science  13 Jul 2007:
Vol. 317, Issue 5835, pp. 225-227
DOI: 10.1126/science.1144314

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The extreme toxicity of organomercury compounds that are found in the environment has focused attention on the mechanisms of action of bacterial remediating enzymes. We describe facile room-temperature protolytic cleavage by a thiol of the Hg-C bond in mercury-alkyl compounds that emulate the structure and function of the organomercurial lyase MerB. Specifically, the tris(2-mercapto-1-t-butylimidazolyl)hydroborato ligand [TmBut], which features three sulfur donors, has been used to synthesize [TmBut]HgR alkyl compounds (R = methyl or ethyl) that react with phenylthiol (PhSH) to yield [TmBut]HgSPh and RH. Although [TmBut]HgR compounds exist as linear two-coordinate complexes in the solid state, 1H nuclear magnetic resonance spectroscopy indicates that the complexes exist in rapid equilibrium with their higher-coordinate [κ2-TmBut]HgR and [κ3-TmBut]HgR isomers in solution. Facile access to a higher-coordinate species is proposed to account for the exceptional reactivity of [TmBut]HgR relative to that of other two-coordinate mercury-alkyl compounds.

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