Xenon hexafluoride

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Xenon hexafluoride
Structural formula Xenon hexafluoride.svg
Structural formula
Space-filling model Xenon-hexafluoride-3D-SF.png
Space-filling model
Identifiers
3D model (JSmol)
ChemSpider
PubChem CID
UNII
  • InChI=1S/F6Xe/c1-7(2,3,4,5)6 Yes check.svgY
    Key: ARUUTJKURHLAMI-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/F6Xe/c1-7(2,3,4,5)6
    Key: ARUUTJKURHLAMI-UHFFFAOYAF
  • F[Xe](F)(F)(F)(F)F
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)
reacts
Thermochemistry
−294 kJ·mol−1 [1]
Related compounds
Related compounds
Krypton hexafluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Xenon hexafluoride is a noble gas compound with the formula XeF6. It is one of the three binary fluorides of xenon that have been studied experimentally, 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. It is a colorless solid that readily sublimes into intensely yellow vapors.

Contents

Preparation

Xenon hexafluoride can be prepared by heating of XeF2 at about 300 °C under 6 MPa (60 atmospheres) of fluorine. With NiF
2
as catalyst, however, this reaction can proceed at 120 °C even in xenon-fluorine molar ratios as low as 1:5. [2] [3]

Structure

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 . It is a fluxional molecule. Oh is only insignificantly higher, indicating that the minimum on the energy surface is very shallow. [4]

129Xe and 19F NMR spectroscopy indicates that in solution the compound assumes a tetrameric structure: 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".

Six polymorphs of XeF
6
are known. [5] including one that contains XeF+
5
ions with bridging F
ions. [6]

Reactions

Hydrolysis

Xenon hexafluoride hydrolyzes, ultimately affording xenon trioxide: [7]

XeF6 + H2O → XeOF4 + 2 HF
XeOF4 + H2O → XeO2F2 + 2 HF
XeO2F2 + H2O → XeO3 + 2 HF
XeF6 + 3 H2O → XeO3 + 6 HF

XeF6 is a Lewis acid, binding one and two fluoride anions:

XeF6 + F → XeF
7
XeF
7
+ F → XeF2−
8

Octafluoroxenates

Salts of the octafluoroxenate(VI) anion (XeF2
8
)
are very stable, decomposing only above 400 °C. [8] [9] [10] This anion has been shown to have square antiprismatic geometry, based on single-crystal X-ray counter analysis of its nitrosonium salt, (NO)
2
XeF
8
. [11] The sodium and potassium salts are formed directly from sodium fluoride and potassium fluoride: [10]

2 NaF + XeF
6
Na
2
XeF
8
2 KF + XeF
6
K
2
XeF
8

These are thermally less stable than the caesium and rubidium salts, which are synthesized by first forming the heptafluoroxenate salts:

CsF + XeF
6
CsXeF
7
RbF + XeF
6
RbXeF
7

which are then pyrolysed at 50 °C and 20 °C, respectively, to form the yellow [12] octafluoroxenate salts: [8] [9] [10]

2 CsXeF
7
Cs
2
XeF
8
+ XeF
6
2 RbXeF
7
Rb
2
XeF
8
+ XeF
6

These salts are hydrolysed by water, yielding various products containing xenon and oxygen. [10]

The two other binary fluorides of xenon do not form such stable adducts with fluoride.

With fluoride acceptors

XeF
6
reacts with strong fluoride acceptors such as RuF
5
[6] and BrF
3
·AuF
3
[13] to form the XeF+
5
cation:

XeF
6
+ RuF
5
→ XeF+
5
RuF
6
XeF
6
+ BrF
3
·AuF
3
→ XeF+
5
AuF
4
+ BrF
3

Related Research Articles

<span class="mw-page-title-main">Xenon hexafluoroplatinate</span> Chemical compound

Xenon hexafluoroplatinate is the product of the reaction of platinum hexafluoride with xenon, in an experiment that proved the chemical reactivity of the noble gases. This experiment was performed by Neil Bartlett at the University of British Columbia, who formulated the product as "Xe+[PtF6]", although subsequent work suggests that Bartlett's product was probably a salt mixture and did not in fact contain this specific salt.

In chemistry, noble gas compounds are chemical compounds that include an element from the noble gases, group 18 of the periodic table. Although the noble gases are generally unreactive elements, many such compounds have been observed, particularly involving the element xenon.

Xenon tetroxide is a chemical compound of xenon and oxygen with molecular formula XeO4, remarkable for being a relatively stable compound of a noble gas. It is a yellow crystalline solid that is stable below −35.9 °C; above that temperature it is very prone to exploding and decomposing into elemental xenon and oxygen (O2).

<span class="mw-page-title-main">Xenon tetrafluoride</span> Chemical compound

Xenon tetrafluoride is a chemical compound with chemical formula XeF
4
. It was the first discovered binary compound of a noble gas. It is produced by the chemical reaction of xenon with fluorine:

<span class="mw-page-title-main">Teflic acid</span> Chemical compound

Teflic acid is a chemical compound with the formula HOTeF5. This strong acid is related to orthotelluric acid, Te(OH)6. Teflic acid has a slightly distorted octahedral molecular geometry.

<span class="mw-page-title-main">Xenon trioxide</span> Chemical compound

Xenon trioxide is an unstable compound of xenon in its +6 oxidation state. It is a very powerful oxidizing agent, and liberates oxygen from water slowly, accelerated by exposure to sunlight. It is dangerously explosive upon contact with organic materials. When it detonates, it releases xenon and oxygen gas.

<span class="mw-page-title-main">Xenon difluoride</span> Chemical compound

Xenon difluoride is a powerful fluorinating agent with the chemical formula XeF
2
, and one of the most stable xenon compounds. Like most covalent inorganic fluorides it is moisture-sensitive. It decomposes on contact with water vapor, but is otherwise stable in storage. Xenon difluoride is a dense, colourless crystalline solid.

Xenon compounds are compounds containing the element xenon (Xe). After Neil Bartlett's discovery in 1962 that xenon can form chemical compounds, a large number of xenon compounds have been discovered and described. Almost all known xenon compounds contain the electronegative atoms fluorine or oxygen. The chemistry of xenon in each oxidation state is analogous to that of the neighboring element iodine in the immediately lower oxidation state.

<span class="mw-page-title-main">Xenon oxytetrafluoride</span> Chemical compound

Xenon oxytetrafluoride is an inorganic chemical compound. It is an unstable colorless liquid with a melting point of −46.2 °C that can be synthesized by partial hydrolysis of XeF
6
, or the reaction of XeF
6
with silica or NaNO
3
:

<span class="mw-page-title-main">Dioxygenyl</span> Chemical compound

The dioxygenyl ion, O+
2
, is a rarely-encountered oxycation in which both oxygen atoms have a formal oxidation state of +1/2. It is formally derived from oxygen by the removal of an electron:

<span class="mw-page-title-main">Rhenium heptafluoride</span> Chemical compound

Rhenium heptafluoride is the compound with the formula ReF7. It is a yellow low melting solid and is the only thermally stable metal heptafluoride. It has a distorted pentagonal bipyramidal structure similar to IF7, which was confirmed by neutron diffraction at 1.5 K. The structure is non-rigid, as evidenced by electron diffraction studies.

A hexafluoride is a chemical compound with the general formula QXnF6, QXnF6m−, or QXnF6m+. Many molecules fit this formula. An important hexafluoride is hexafluorosilicic acid (H2SiF6), which is a byproduct of the mining of phosphate rock. In the nuclear industry, uranium hexafluoride (UF6) is an important intermediate in the purification of this element.

<span class="mw-page-title-main">Nitrosonium octafluoroxenate(VI)</span> Chemical compound

Nitrosonium octafluoroxenate(VI) is a chemical compound of xenon with nitrogen, oxygen, and fluorine, having formula (NO)
2
XeF
8
. It is an ionic compound containing well-separated nitrosonium cations (NO+) and octafluoroxenate(VI) anions (XeF2−
8
). The molecular geometry of the octafluoroxenate(VI) ion is square antiprismatic, having Xe–F bond lengths of 1.971 Å, 1.946 Å, 1.958 Å, 2.052 Å, and 2.099 Å.

<span class="mw-page-title-main">Chromyl fluoride</span> Chemical compound

Chromyl fluoride is an inorganic compound with the formula CrO2F2. It is a violet-red colored crystalline solid that melts to an orange-red liquid.

<span class="mw-page-title-main">Square antiprismatic molecular geometry</span>

In chemistry, the square antiprismatic molecular geometry describes the shape of compounds where eight atoms, groups of atoms, or ligands are arranged around a central atom, defining the vertices of a square antiprism. This shape has D4d symmetry and is one of the three common shapes for octacoordinate transition metal complexes, along with the dodecahedron and the bicapped trigonal prism.

<span class="mw-page-title-main">Neptunium(VI) fluoride</span> Chemical compound

Neptunium(VI) fluoride (NpF6) is the highest fluoride of neptunium, it is also one of seventeen known binary hexafluorides. It is an orange volatile crystalline solid. It is relatively hard to handle, being very corrosive, volatile and radioactive. Neptunium hexafluoride is stable in dry air but reacts vigorously with water.

Fluorine forms a great variety of chemical compounds, within which it always adopts an oxidation state of −1. With other atoms, fluorine forms either polar covalent bonds or ionic bonds. Most frequently, covalent bonds involving fluorine atoms are single bonds, although at least two examples of a higher order bond exist. Fluoride may act as a bridging ligand between two metals in some complex molecules. Molecules containing fluorine may also exhibit hydrogen bonding. Fluorine's chemistry includes inorganic compounds formed with hydrogen, metals, nonmetals, and even noble gases; as well as a diverse set of organic compounds. For many elements the highest known oxidation state can be achieved in a fluoride. For some elements this is achieved exclusively in a fluoride, for others exclusively in an oxide; and for still others the highest oxidation states of oxides and fluorides are always equal.

<span class="mw-page-title-main">Xenon oxydifluoride</span> Chemical compound

Xenon oxydifluoride is an inorganic compound with the molecular formula XeOF2. The first definitive isolation of the compound was published on 3 March 2007, producing it by the previously-examined route of partial hydrolysis of xenon tetrafluoride.

<span class="mw-page-title-main">Radon compounds</span>

Radon compounds are chemical compounds formed by the element radon (Rn). Radon is a noble gas, i.e. a zero-valence element, and is chemically not very reactive. The 3.8-day half-life of radon-222 makes it useful in physical sciences as a natural tracer. Because radon is a gas under normal circumstances, and its decay-chain parents are not, it can readily be extracted from them for research.

Caesium heptafluoroxenate is an inorganic compound of caesium, and fluorine, and xenon with the chemical formula CsXeF7.

References

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