The Solvation of the Mercury(II) Ion - a ¹⁹⁹Hg NMR Study

The solvation of the mercury(II) ion in solvents with different solvation properties, water, dimethylsulfoxide, N,N-dimethylthioformamide and liquid ammonia, has been studied by means of 199Hg NMR. The 199Hg chemical shift shows a pronounced dependence on the coordination number of the mercury(II) ion in the solvates resulting in over 1200 ppm difference between basically tetrahedral and octahedral species. The chemical shifts can be furthermore associated with electron-pair donor properties of the solvents. The spin-lattice relaxation times of the 199Hg nucleus in the solvates have been measured at different applied magnetic fields, concentrations, temperatures and isotope substitutions. Possible mechanisms for the 199Hg relaxation are proposed and the chemical shielding anisotropy in the solvates has been estimated. The 199Hg relaxation rates and the anisotropy are correlated with the structure of the solvate complexes in solution obtained from recent LAXS and EXAFS studies