Selenium hexafluoride

Selenium hexafluoride

Names
IUPAC name Selenium hexafluoride
Other names Selenium(VI) fluoride, Selenium fluoride
Identifiers
CAS Number	7783-79-1 Y
ChemSpider	22964
Jmol 3D model	Interactive image
PubChem	24558
RTECS number	VS9450000
InChI InChI=1S/F6Se/c1-7(2,3,4,5)6 Key: LMDVZDMBPZVAIV-UHFFFAOYSA-N InChI=1S/F6Se/c1-7(2,3,4,5)6 Key: LMDVZDMBPZVAIV-UHFFFAOYAP
SMILES F[Se](F)(F)(F)(F)F
Properties
Chemical formula	SeF6
Molar mass	192.9534 g/mol
Appearance	colourless gas
Density	7.887 g/cm3
Melting point	−34.6 °C (−30.3 °F; 238.6 K)
Boiling point	−46.6 °C (−51.9 °F; 226.6 K) sublimes
Solubility in water	insoluble
Vapor pressure	>1 atm (20°C)
Refractive index (nD)	1.895
Structure
Crystal structure	Orthorhombic, oP28
Space group	Pnma, No. 62
Coordination geometry	octahedral (Oh)
Dipole moment	0
Thermochemistry
Std enthalpy of formation (ΔfHo298)	1030 kJ/mol
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Selenium hexafluoride is the inorganic compound with the formula SeF₆. It is a colourless gas described as having a "repulsive" odor. It is not widely encountered and has no commercial applications.

Structure, preparation, and reactions

Like many compounds of selenium, SeF₆ is hypervalent. The compound has octahedral molecular geometry with Se-F bond length 168.8 pm.

SeF₆ can be prepared from the elements or by the reaction of bromine trifluoride (BrF₃) with selenium dioxide. The crude product is purified by sublimation.

The relative reactivity of the hexafluorides of S, Se, and Te follows the order TeF₆ > SeF₆ > SF₆, the latter being completely inert toward hydrolysis until high temperatures. SeF₆ also resists hydrolysis. The gas can be passed through 10% NaOH or KOH without change, but reacts with gaseous ammonia at 200 °C.

Safety

Although selenium hexafluoride is quite inert and slow to hydrolyze, it is toxic even at low concentrations, especially by longer exposure. In the U.S., OSHA and ACGIH standards for selenium hexafluoride exposure is an upper limit of 0.05 ppm in air averaged over an eight-hour work shift. Additionally, selenium hexafluoride is designated as IDLH chemical with a maximum allowed exposure limit of 2 ppm.

External links

• ATSDR ToxFAQs - Selenium Hexafluoride U.S. Department of Health and Human Services
• CDC - NIOSH Pocket Guide to Chemical Hazards U.S. Department of Health and Human Services
• WebBook page for SeF₆