Xenon hexafluoride
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Xenon hexafluoride, XeF6, is a colorless crystalline compound at room temperature. It melts at 49.25 °C (120.7 °F) and boils at 75.6 °C (168.1 °F).
Xenon fluorides are all exergonic and quite stable at normal temperatures. They do react readily with water (including moist air), so samples should be stored under anhydrous conditions.
For example, when xenon hexafluoride is exposed to water, a solution of xenon trioxide is rapidly formed:[1]
- XeF6(g) + 3H2O(l) → XeO3(s) + 6HF(aq)
[edit] Structure
Unlike xenon difluoride and xenon tetrafluoride, which have simple structures, XeF6 required several years for its structure to be elucidated. In the gas phase it adopts a slightly distorted octahedral geometry, but it lacks perfect octahedral symmetry, as predicted by VSEPR theory. According to Konrad Seppelt, then Associate Professor of Chemistry at the University of Heidelberg, "the structure is best described in terms of a mobile electron pair that moves over the faces and edges of the octahedron and thus distorts it in a dynamic manner.".[2] NMR spectra of 129Xe19F6 indicate that it is tetrameric: four equivalent xenon atoms are arranged in a tetrahedron surrounded by a fluctuating array of 24 fluorine atoms that interchange positions in a "cogwheel mechanism".[3]
[edit] References
- ^ Appelman, E. H., and J. G. Malm (June 1964). "Hydrolysis of Xenon Hexafluoride and the Aqueous Solution Chemistry of Xenon". Journal of the American Chemical Society 86 (11): 2141–2148. DOI:10.1021/ja01065a009.
- ^ Seppelt, Konrad (June 1979). "Recent Developments in the Chemistry of Some Electronegative Elements". Accounts of Chemical Research 12 (6): 211–216. DOI:10.1021/ar50138a004.
- ^ ibid.
