Tellurium hexafluoride

Tellurium hexafluoride is the inorganic compound of tellurium and fluorine with the chemical formula TeF6. It is a colorless, highly toxic gas with an unpleasant odor.[4]

Tellurium hexafluoride
Structure and dimensions of the molecule
Structure and dimensions of the molecule
Ball-and-stick model of the molelcule
Ball-and-stick model of the molelcule
Identifiers
3D model (JSmol)
ECHA InfoCard 100.029.115
EC Number
  • 232-027-0
UNII
  • InChI=1S/F6Te/c1-7(2,3,4,5)6
  • F[Te](F)(F)(F)(F)F
Properties
TeF6
Molar mass 241.590 g/mol
Appearance colorless gas
Odor repulsive odor
Density 0.0106 g/cm3 (-10 °C)
4.006 g/cm3 (-191 °C)
Melting point −38.9 °C (−38.0 °F; 234.2 K)[1]
Boiling point −37.6 °C (−35.7 °F; 235.6 K)[1]
decomposes
Vapor pressure >1 atm (20°C)[2]
−66.0·10−6 cm3/mol
1.0009
Structure
Orthorhombic, oP28
Pnma, No. 62
octahedral (Oh)
0
Thermochemistry
117.6 J/(mol K)
-1318 kJ/mol
Hazards
Lethal dose or concentration (LD, LC):
5 ppm (rat, 4 hr)
5 ppm (mouse, 1 hr)
5 ppm (rabbit, 4 hr)
5 ppm (guinea pig, 4 hr)[3]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 0.02 ppm (0.2 mg/m3)[2]
REL (Recommended)
 TWA 0.02 ppm (0.2 mg/m3)[2]
IDLH (Immediate danger)
 1 ppm[2]
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

Preparation

Tellurium hexafluoride can be prepared by treating tellurium with fluorine gas at 150 °C.[4][5] It can also be prepared by fluorination of TeO3 with bromine trifluoride. Upon heating, TeF4 disproportionates to give TeF6 and Te.

Properties

Tellurium hexafluoride is a highly symmetric octahedral molecule. Its physical properties resemble those of the hexafluorides of sulfur and selenium. It is less volatile, however, due to the increase in polarizability. At temperatures below −38 °C, tellurium hexafluoride condenses to a volatile white solid.

  • Ball-and-stick model of the crystal structure
    Ball-and-stick model of the crystal structure
  • Space-filling model of the crystal structure
    Space-filling model of the crystal structure

Reactivity

Tellurium hexafluoride is much more chemically reactive than SF6.[6] For example, TeF6 slowly hydrolyzes to Te(OH)6:

TeF6 + 6 H2O → Te(OH)6 + 6 HF

Treatment of tellurium hexafluoride with tetramethylammonium fluoride (Me4NF) gives, sequentially, the hepta- and octafluorides:

TeF6 + Me4NF → Me4NTeF7
Me4NTeF7 + Me4NF → (Me4N)2TeF8

Further sources
  • W.C. Cooper, Tellurium, Van Nostrand Reinhold Company, New York, USA, 1971.
  • K.W. Bagnall, The Chemistry of Selenium, Tellurium and Polonium, Elsevier Publishing, New York, 1966.
  • R.T. Sanderson, Chemical Periodicity, Reinhold, New York, USA, 1960.
  • F. A. Cotton, G. Wilkinson, C.A. Murillo, and M. Bochmann; Advanced Inorganic Chemistry, John Wiley & Sons, 1999.
  • G.J. Hathaway, N.H. Proctor, Chemical Hazards of the Workplace, 5th edition, Wiley-Interscience, New Jersey, 2004.

References
  1. CRC Handbook of Chemistry and Physics, 90. Auflage, CRC Press, Boca Raton, Florida, 2009, ISBN 978-1-4200-9084-0, Section 4, Physical Constants of Inorganic Compounds, p. 4-95.
  2. NIOSH Pocket Guide to Chemical Hazards. "#0588". National Institute for Occupational Safety and Health (NIOSH).
  3. "Tellurium hexafluoride (as Te)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. W. Kwasnik (1963). "Tellurium Hexafluoride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY, NY: Academic Press. p. 180.
  5. Yost, Don M. (2007) [1939]. "Sulfur, Selenium, and Tellurium Hexafluorides". Inorganic Syntheses. Inorganic Syntheses. Vol. 1. pp. 121–122. doi:10.1002/9780470132326.ch44. ISBN 978-0-470-13232-6.
  6. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
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