Solid-State 199Hg and 113Cd NMR Studies of Mercury- and Cadmium-Thiolate Complexes. Spectroscopic Models for [Hg(SCys)n] Centers in the Bacterial Mercury Resistance Proteins

Rodolfo A. Santos, Eric S. Gruff, Stephen A. Koch, Gerard S. Harbison

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Abstract

199Hg CP/MAS-NMR spectra have been measured for representative examples of the major coordination geometries available to monomeric mercury thiolate complexes: [Hg(SR)2], [Hg(SR)3], and [Hg(SR)4]2−. Solid-state 113Cd NMR spectra have been measured for related [Cd(SR)3]1− compounds. [(n-Bu)4N] [Cd(S-2,4,6-i-Pr3C6H2)3] and [Ph4P][Hg(S-2,3,5,6-Me4C6H)3] were structurally characterized by X-ray crystallography. The metal ions in both compounds are three-coordinate with distorted Y-shaped, planar [MS3] units. These structures are discussed in relationship to a second conformational isomer, the symmetric C3h [M(SR)3]1− anion. The shielding tensor, isotropic chemical shift (σiso), the chemical shielding anistropy (Δσ), and the asymmetry parameter (η) vary in a systematic manner as a function of coordination number and coordination geometry. 199Hg and 113Cd CP/MAS-NMR data for selected compounds (σiso, Δσ, η) are as follows: [Hg(S-2,4,6-i-Pr3C6H2)2] (−1015, 4256, 0.16); [Ph4P][Hg(S-2,4,6-i-Pr3C6H2)3] (−267, 1408, 0.30), [(n-Bu)4N][Hg(SPh)3] (−341, 1273, 0.97), [Et4N]2[Hg(S-2-PhC6H4)4] (−433, 86.5,0.86), and [Ph4P] [Cd(S-2,4,6-i-Pr3C6H2)3] (668, 483, 0.24). The implications of this study to solution and solid-state 119Hg and 113Cd NMR studies of Hg- and Cd-cysteine proteins are discussed.

Original languageEnglish (US)
Pages (from-to)469-475
Number of pages7
JournalJournal of the American Chemical Society
Volume113
Issue number2
DOIs
Publication statusPublished - Jan 1 1991

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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