Monday, May 14, 2007
Inorganic Chemistry - updated to May 2007
Michelle A. M. Forgeron, Roderick E. Wasylishen, Michael Gerken, and Gary J. Schrobilgen. (2007).
"Solid-State 129Xe and 131Xe NMR Study of the Perxenate Anion XeO64-."
Inorg. Chem. 46(9): 3585-3592.
Abstract: Results of the first solid-state 131Xe NMR study of xenon-containing compounds are presented. The two NMR-active isotopes of xenon, 129Xe (I = 1/2) and 131Xe (I = 3/2), are exploited to characterize the xenon magnetic shielding and quadrupolar interactions for two sodium perxenate salts, Na4XeO6·xH2O (x = 0, 2), at an applied magnetic field strength of 11.75 T. Solid-state 129/131Xe NMR line shapes indicate that the local xenon environment in anhydrous Na4XeO6 adopts octahedral symmetry, but upon hydration, the XeO64- anion becomes noticeably distorted from octahedral symmetry. For stationary, anhydrous samples of Na4XeO6, the heteronuclear 129/131Xe-23Na dipolar interaction is the principal contributor to the breadth of the 129/131Xe NMR lines. For stationary and slow magic-angle-spinning samples of Na4XeO6·2H2O, the anisotropic xenon shielding interaction dominates the 129Xe NMR line shape, whereas the 131Xe NMR line shape is completely dominated by the nuclear quadrupolar interaction. The xenon shielding tensor is approximately axially symmetric, with a skew of -0.7 ± 0.3, an isotropic xenon chemical shift of -725.6 ± 1.0 ppm, and a span of 95 ± 5 ppm. The 131Xe quadrupolar coupling constant, 10.8 ± 0.5 MHz, is large for a nucleus at a site of approximate Oh symmetry, and the quadrupolar asymmetry parameter indicates a lack of axial symmetry. This study demonstrates the extreme sensitivity of the 131Xe nuclear quadrupolar interaction to changes in the local xenon environment.
Ling-I Hung, Sue-Lein Wang, Hsien-Ming Kao, and Kwang-Hwa Lii. (2007).
"Flux Synthesis, Crystal Structures, and Solid-State NMR Spectroscopy of Two Indium Silicates Containing Varied In-O Coordination Geometries."
Inorg. Chem. 46(8): 3301-3305.
Abstract: Two novel indium silicates, K5In3Si7O21 (1) and K4In2Si8O21 (2), have been synthesized by a flux-growth method and characterized by single-crystal X-ray diffraction. The structure of 1 consists of siebener single chains of corner-sharing SiO4 tetrahedra running along the b axis linked via corner-sharing by In2O9 face-sharing octahedral dimers and InO5 trigonal bipyramids to form a 3D framework. The structure of 2 consists of a 3D silicate framework containing 6- and 14-ring channels. InO5 square pyramids are located within the 14-ring channels sharing corners with the silicate framework. The solid-state 29Si MAS NMR spectrum of compound 1 was recorded; it shows the influence of the indium atoms in the second coordination sphere of the silicon on the chemical shift. Crystal data: 1, orthorhombic, Pna21 (No. 33), a = 12.4914(3) Å, b = 16.8849(3) Å, c = 10.2275(2) Å, V = 2157.1(1) Å3 and Z = 4; 2, monoclinic, P21/n (No. 14), a = 8.4041(3) Å, b = 11.4919(4) Å, c = 10.4841(3) Å, = 90.478(2), V = 1012.5(1) Å3 and Z = 2.