Xenon hexafluoride
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3D model (Jmol)
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PubChem CID
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| Properties | |||
| XeF6 | |||
| Molar mass | 245.28 g mol−1 | ||
| Density | 3.56 g cm−3 | ||
| Melting point | 49.25 °C (120.65 °F; 322.40 K) | ||
| Boiling point | 75.6 °C (168.1 °F; 348.8 K) | ||
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Std enthalpy of
formation (ΔfH |
−294 kJ·mol−1 | ||
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Xenon hexafluoride is a noble gas compound with the formula XeF6 and the highest of the three known binary fluorides of xenon, the other two being XeF2 and XeF4. All known are exergonic and stable at normal temperatures. XeF6 is the strongest fluorinating agent of the series. At room temperature, it is a colorless solid that readily sublimes into intensely yellow vapors.
Xenon hexafluoride can be prepared by long-term heating of XeF2 at about 300 °C and pressure 6 MPa (60 atmospheres).
With NiF
2 as catalyst, however, this reaction can proceed at 120 °C even in xenon-fluorine molar ratios as low as 1:5.
The structure of XeF6 required several years to establish in contrast to the cases of XeF
2 and XeF
4. In the gas phase the compound is monomeric. VSEPR theory predicts that due to the presence of six fluoride ligands and one lone pair of electrons the structure lacks perfect octahedral symmetry, and indeed electron diffraction combined with high-level calculations indicate that the compound's point group is C3v. Oh is only insignificantly higher, indicating that the minimum on the energy surface is very shallow. Konrad Seppelt, an authority on noble gas and fluorine chemistry, says, "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."
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