Lewis-acid properties of technetium(VII) dioxide trifluoride, TcO2F3:: Characterization by 19F, 17O, and 99Tc NMR spectroscopy and Raman spectroscopy, density functional theory calculations of TcO2F3, M+TcO2F4- [M = Li, Cs, N(CH3)4], and TcO2F3•CH3CN, and X-ray crystal structure of Li+TcO2F4-

被引:28
作者
Casteel, WJ
Dixon, DA
LeBlond, N
Mercier, HPA
Schrobilgen, GJ
机构
[1] McMaster Univ, Dept Chem, Hamilton, ON L8S 4M1, Canada
[2] Pacific NW Lab, William Wiley Environm Mol Sci Lab, Richland, WA 99352 USA
关键词
D O I
10.1021/ic9708935
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
Technetium(VII) dioxide trifluoride, TcO2F3, behaves as a Lewis acid toward the fluoride ion and acetonitrile forming M+TcO2F4- [M = Li, Cs, N(CH3)(4)] salts and TcO2F3 . CH3CN. Fluorine-19 NMR spectroscopy established that the TcO2F4- anion has a cis-dioxo geometry in CH3CN solution. Variable-temperature F-19 NMR studies of TcO2F4- and TcO2F3 . CH3CN in CH3CN revealed that the one-bond couplings between Tc-99 and the two fluorine environments exhibit widely different degrees of quadrupolar collapse. The O-17 NMR spectra of O-17-enriched TcO2F4- and TcO2F3 . CH2CN and the H-1 and C-13 NMR spectra of TcO2F3 . CH3CN indicated that chemical exchange occurs between TcO2F3 . CH3CN and CH3CN solvent. The TcO2F4- anion was characterized by X-rag crystallography as its lithium salt crystallizing in the tetragonal system, space group P (4) over bar 2(1)m, with a =14.706(1) Angstrom, c = 8.797(2) Angstrom, V = 194.8(1) Angstrom(3). and Z = 2. at 20 degrees C, Refinement converged with R = 0.0339 (R-w = 0.0320). The anion geometry is a distorted octahedron with the two oxygen ligands cis to each other and is closely related to the [TcO2F4] units in polymeric TcO2F3. The Raman spectra of M+TcO2F4- [M = Li, Cs, N(CH3)(4)] and TcO2F3 . CH3CN were assigned under C-2v and C-5 point symmetries, respectively. Density functional theory calculations at the local and nonlocal levels predict that monomeric TcO2F3 has a trigonal bipyramidal geometry (C-2v point symmetry) and confirm that the cis-dioxo isomers of TcO2F4- and TcO2F3 . CH3CN (CH3CN bonded trans to an oxygen) are the energy-minimized structures.
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页码:340 / 353
页数:14
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