803739-31-3Relevant articles and documents
The first structurally authenticated organomercury(1+) thioether complexes - Mercury-carbon bond activation related to the mechanism of the bacterial enzyme organomercurial lyase
Wilhelm, Michaela,Deeken, Stefan,Berssen, Era,Saak, Wolfgang,Luetzen, Arne,Koch, Rainer,Strasdeit, Henry
, p. 2301 - 2312 (2004)
The new compounds [MeHg([9]aneS3)](BF4) (1), [MeHg([12]aneS3)](BF4) (2), and [(MeHg) 2([14]aneS4)](BF4)2 (3) have been prepared and their crystal structures determined. In 1, the thioether acts as a tridentate ligand [Hg-S 2.611(2)-2.768(2) A] and thus the metal atom is tetrahedrally coordinated, which is rare in organomercury chemistry. Temperature-dependent 1H and 13C NMR spectra showed that this coordination is retained in acetonitrile solution. In crystalline 2 and 3, linear-coordinated HgII occurs with Hg-S bond lengths of 2.441(4) and 2.425(2) A. [MeHg([9]aneS3)]+ was found to be stable towards ligand substitution by CF3SO3- in dimethyl sulfoxide, whereas the thioether was partly displaced by CF 3CO2- and completely by CH3CO 2-. Protonolysis by the very strong Bronsted acid CF 3SO3H in [D3]nitromethane transformed the methanido ligand into methane. The degree of Hg-C bond cleavage was ca. 25% for the four-coordinate [MeHg([9]aneS3)]+ after 1 h, whereas no reaction was observed for two-coordinate [MeHg(SEt2)]+ or MeHgCl under similar conditions even after 24 h. The product Hg2+ was trapped as [Hg([9]aneS3)2]2+, which is a six-coordinate complex, as shown by a crystal structure analysis of [Hg([9]aneS3)2](BF4)2·2 CH3CN. Quantum chemical calculations [MP2/SDD + SDD ECP Hg, 6-31+G(d,p) other elements] confirmed that hydrogen transfer activation barriers are significantly lower for high -coordinate (CN > 2) complexes. Hg-C bond activation by the enzyme organomercurial lyase is possibly also based on multiple (cysteinyl) sulfur ligation. We propose a hypothetical reaction mechanism that involves an OH-containing amino acid side chain or a water molecule simultaneously serving as a proton acceptor (from Cys-SH) and donor (to R- of RHg+). This mechanism is supported by quantum chemical calculations on a model system. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
