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]
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3D model (JSmol) | |||
| ECHA InfoCard | 100.029.115 | ||
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| 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)[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 | |||
Refractive index (nD) | 1.0009 | ||
| Structure | |||
| Orthorhombic, oP28 | |||
| Pnma, No. 62 | |||
| octahedral (Oh) | |||
| 0 | |||
| Thermochemistry | |||
Heat capacity (C) | 117.6 J/(mol K) | ||
Std enthalpy of formation (ΔfH⦵298) | -1318 kJ/mol | ||
| Hazards | |||
| Lethal dose or concentration (LD, LC): | |||
LCLo (lowest published) | 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). | |||
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
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.