title: Methyl Transfer to Mercury Thiolates: Effects of Coordination Number and Ligand Dissociation.
abstract: The complexes [(CH(3))(4)N](2)[Hg(SC(6)H(5))(4)] and [(C(4)H(9))(4)N][Hg(SC(6)H(5))(3)] demethylate (CH(3)O)(3)PO as revealed by (1)H, (31)P{(1)H}, and (199)Hg{(1)H} NMR spectroscopy in DMSO-d(6) solution. The products of the [(CH(3))(4)N](2)[Hg(SC(6)H(5))(4)] reaction are CH(3)SC(6)H(5), (CH(3)O)(2)PO(2)(-), and [Hg(SC(6)H(5))(3)](-), whereas [Hg(SC(6)H(5))(3)](-) demethylates (CH(3)O)(3)PO to yield CH(3)SC(6)H(5) and {Hg(SC(6)H(5))(2)[(CH(3)O)(2)PO(2)]}(-). Kinetic and solution studies of [(CH(3))(4)N](2)[Hg(SC(6)H(5))(4)] reveal a rapid equilibrium between bound and free thiolate. The dissociated thiolate is the nucleophile active toward (CH(3)O)(3)PO. These results imply that the metal center of the inactive mercury derivative of the Escherichia coli Ada DNA alkylation repair protein may comprise a three-coordinate [Hg(S-cysteine)(3)](-) moiety and an unbound, protonated cysteine (HS-Cys69).
authors.affiliation: Departments of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Dartmouth College, Hanover, New Hampshire 03755.
authors.forename: Jonathan J.
authors.initials: JJ
authors.lastname: Wilker
authors.forename: Karen E.
authors.initials: KE
authors.lastname: Wetterhahn
authors.forename: Stephen J.
authors.initials: SJ
authors.lastname: Lippard