Tellurium hexafluoride

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 Edit this at Wikidata
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
Density 0.0106 g/cm3 (-10 °C)
4.006 g/cm3 (-191 °C)
Melting point −38.9 °C (−38.0 °F; 234.2 K)[2]
Boiling point −37.6 °C (−35.7 °F; 235.6 K)[2]
decomposes
Vapor pressure >1 atm (20°C)[1]
−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)[1]
REL (Recommended)
 TWA 0.02 ppm (0.2 mg/m3)[1]
IDLH (Immediate danger)
 1 ppm[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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]

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.[citation needed]

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. ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0588". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ a b 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.
  3. ^ "Tellurium hexafluoride (as Te)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. ^ a b 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. 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.