Xenon Fluoride (VI)

Xenon fluoride
Xenon fluoride
Are common
Systematic ; name	Xenon Fluoride (VI)
Chem. formula	XeF 6
Physical properties
condition	colorless crystals
Molar mass	245 g / mol
Density	3.56 g / cm³
Thermal properties
T. melt.	49.25 ° C
T. bale.	75.6 ° C
Classification
Reg. CAS number	13693-09-9
PubChem
Smiles
Inchi
ChemSpider

Xenon hexafluoride is a compound of xenon with fluorine , which is colorless crystals at room temperature. It has an extremely high chemical activity, aggressiveness.

Content

Physico-chemical properties

Property	Value
Dielectric constant (at 55 ° C)	4.1
Enthalpy of formation (298K, in the gas phase)	−277.2 kJ / mol
Entropy of formation (298K, in the gas phase)	387.242 J / (mol · K)
Heat capacity (298K, in the gas phase)	131.168 J / (molK)
Enthalpy of melting	5.74 kJ / mol
Sublimation Enthalpy	60.8 kJ / mol

Getting

Typically, hexafluoride is obtained by prolonged heating of xenon difluoride (XeF ₂ ) at 300 ° C under a pressure of 60 atm (nickel fluoride is used as a catalyst):

{\mathsf {3XeF_{2}\rightarrow 2Xe+XeF_{6}}}

{\ displaystyle {\ mathsf {3XeF_ {2} \ rightarrow 2Xe + XeF_ {6}}}}

However, the famous Soviet scientist Academician Legasov for the first time in the world carried out the catalytic synthesis of xenon hexafluoride from simple substances:

{\mathsf {Xe+3F_{2}\rightarrow XeF_{6}}}

{\ displaystyle {\ mathsf {Xe + 3F_ {2} \ rightarrow XeF_ {6}}}}

Building

The study of the crystal structure of xenon hexafluoride took many years. However, as a result of applying modern physicochemical research methods, six different crystalline modifications were identified. For example, when studying the isotopically enriched ¹²⁹ Xe ¹⁹ F ₆ compound by ¹⁹ F- NMR spectroscopy, it was found that under standard conditions, four xenon atoms are in the same electronic environment of 24 fluorine atoms. ^[one]

3 crystalline structures of the substance are well studied:

No.	Transition temperature ° C	Structure
one	> 10	Monoclinic, 8 XeF ₆ per cell
2	10 ÷ -25	Orthorhombic, 16 XeF ₆ per cell
3	−25	Monoclinic, 64 XeF ₆ in a double cell ^[2]

Chemical Properties

Water is rapidly hydrolyzed to xenon trioxide and hydrofluoric acid in three stages. All intermediate hydrolysis products are isolated in an individual state:

{\mathsf {XeF_{6}+H_{2}O\rightarrow XeOF_{4}+2HF}}

{\ displaystyle {\ mathsf {XeF_ {6} + H_ {2} O \ rightarrow XeOF_ {4} + 2HF}}}

{\mathsf {XeOF_{4}+H_{2}O\rightarrow XeO_{2}F_{2}+2HF}}

{\ displaystyle {\ mathsf {XeOF_ {4} + H_ {2} O \ rightarrow XeO_ {2} F_ {2} + 2HF}}}

{\mathsf {XeO_{2}F_{2}+H_{2}O\rightarrow XeO_{3}+2HF}}

{\ displaystyle {\ mathsf {XeO_ {2} F_ {2} + H_ {2} O \ rightarrow XeO_ {3} + 2HF}}}

When dissolved in liquid hydrogen fluoride , partial dissociation occurs:

{\mathsf {XeF_{6}+HF\rightleftarrows XeF_{5}^{+}+HF_{2}^{-}}}

{\ displaystyle {\ mathsf {XeF_ {6} + HF \ rightleftarrows XeF_ {5} ^ {+} + HF_ {2} ^ {-}}}}

Xenon hexafluoride is a fairly strong Lewis acid . In the presence of fluoride ions, the following reactions are possible:

{\mathsf {XeF_{6}+F^{-}\rightarrow [XeF_{7}]^{-}}}

{\ displaystyle {\ mathsf {XeF_ {6} + F ^ {-} \ rightarrow [XeF_ {7}] ^ {-}}}}

{\mathsf {[XeF_{7}]^{-}+F^{-}\rightarrow [XeF_{8}]^{2-}}}

{\ displaystyle {\ mathsf {[XeF_ {7}] ^ {-} + F ^ {-} \ rightarrow [XeF_ {8}] ^ {2-}}}}

For example, the substance readily reacts with alkali metal fluorides (except LiF ):

{\mathsf {XeF_{6}+RbF\rightarrow Rb[XeF_{7}]}}

{\ displaystyle {\ mathsf {XeF_ {6} + RbF \ rightarrow Rb [XeF_ {7}]}}}

However, when such salts are heated above 50 ° C, decomposition occurs:

{\mathsf {2RbXeF_{7}\rightarrow XeF_{6}+Rb_{2}[XeF_{8}]}}

{\ displaystyle {\ mathsf {2RbXeF_ {7} \ rightarrow XeF_ {6} + Rb_ {2} [XeF_ {8}]}}}

Compounds of M ₂ XeF _{8 are} fairly stable. For example, the sodium derivative is stable up to 100 ° C, and the cesium derivative is stable up to 400 ° C.

With fluorides of less active elements, xenon hexafluoride forms double salts ^[3] , which were first obtained in 1967 . For example, 4XeF ₆ · GeF ₄ , 2XeF ₆ · GeF ₄ and XeF ₆ · GeF ₄ were obtained, but it was not possible to obtain a similar compound with silicon fluoride due to the weak basic function of SiF ₄ . The substance also interacts with BF ₃ and AsF ₅ in a 1: 1 ratio. In this case, white stable crystals are formed, weakly volatile at room temperature (vapor pressure is about 1 mmHg). XeF ₆ · BF ₃ melts at 80 ° C to form a yellow viscous liquid. ^[four]

There have also been reports of the receipt of higher XeF ₈ fluoride from XeF ₆ and F ₂ , but this data has not been confirmed. The existence of xenon octafluoride is not possible due to the size of the xenon atom: the fluorine atoms would be very close to each other, and the repulsive force of the same charges would be greater than the Xe-F binding energy.

Application

Xenon hexafluoride is a powerful fluorinating agent.
Possible use as an oxidizer of rocket fuel .

Notes

Literature

Holleman AF, Wiberg E. Inorganic Chemistry. Academic Press: San Diego, 2001. ISBN 0-12-352651-5 .
Nekrasov B.V. Fundamentals of General Chemistry. In 2 volumes., M .: Chemistry, 1973

[1] The structure of xenon hexafluoride in the solid state. Journal of Fluorine Chemistry Volume 127, Issue 10, Pages 1415-1422

[2] Xenon Hexafluoride: Structural Crystallography of Tetrameric Phases RD Burbank, GR Jones. Science vol. 171. No. 3970, pp. 485–487

[3] Study of the XeF ₆ -GeF ₄ and XeF ₆ -SiF ₄ systems

[4] Xenon Hexafluoride Complexes. Science. Vol. 144. no. 3618, p. 537