Methyl Transfer to Mercury Thiolates: Effects of Coordination Number and Ligand Dissociation.

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.

Chromium(VI) Forms Thiolate Complexes with gamma-Glutamylcysteine, N-Acetylcysteine, Cysteine, and the Methyl Ester of N-Acetylcysteine.

Reaction of potassium dichromate with gamma-glutamylcysteine, N-acetylcysteine, and cysteine in aqueous solution resulted in the formation of 1:1 complexes of Cr(VI) with the cysteinyl thiolate ligand. The brownish red Cr(VI)-amino acid/peptide complexes exhibited differential stability in aqueous solutions at 4 degrees C and ionic strength = 1.5 M, decreasing in stability in the order: gamma-glutamylcysteine > N-acetylcysteine > cysteine.