An EXAFS spectroscopic, large-angle X-ray scattering, and crystallographic study of hexahydrated, dimethyl sulfoxide and pyridine 1-oxide hexasolvated mercury(II) ions.
The structure of the solvated mercury(II) ion in water and dimethyl sulfoxide has been studied by means of large-angle X-ray scattering (LAXS) and extended X-ray absorption fine structure (EXAFS) techniques. The distribution of the Hg-O distances is unusually wide and asymmetric in both solvents. In aqueous solution, hexahydrated [Hg(OH(2))(6)](2+) ions in a distorted octahedral configuration, with the centroid of the Hg-O distance at 2.38(1) A, are surrounded by a diffuse second hydration sphere with HgO(II) distances of 4.20(2) A. In dimethyl sulfoxide, the six Hg-O and HgS distances of the hexasolvated [Hg{OS(CH(3))(2)}(6)](2+) complex are centered around 2.38(1) and 3.45(2) A, respectively. The crystal structure of hexakis(pyridine 1-oxide)mercury(II) perchlorate has been redetermined. The space group R(-)3 implies six equal Hg-O distances of 2.3416(7) A for the [Hg(ONC(5)H(5))(6)](2+) complex at 100 K. However, EXAFS studies of this compound, and of the solids hexaaquamercury(II) perchlorate and hexakis(dimethyl sulfoxide)mercury(II) trifluoromethanesulfonate, also with six equidistant Hg-O bonds according to crystallographic results, reveal in all cases strongly asymmetric Hg-O distance distributions. Vibronic coupling of valence states in a so-called pseudo-Jahn-Teller effect probably induces the distorted configurations.
Department of Chemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden. Ingmar.Persson@kemi.slu.se
Ingmar
I
Persson
Lars
L
Eriksson
Patric
P
Lindqvist-Reis
Per
P
Persson
Magnus
M
Sandström
D018360:Crystallography, X-Ray; D004121:Dimethyl Sulfoxide / Q000737:chemistry*; D005583:Fourier Analysis; D008628:Mercury / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D012542:Scattering, Radiation; D013057:Spectrum Analysis / Q000379:methods*
D011725:Pyridines; C013229:pyridine N-oxide; D008628:Mercury; D004121:Dimethyl Sulfoxide