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Chemical compound From Wikipedia, the free encyclopedia
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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Identifiers | |||
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3D model (JSmol) |
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ECHA InfoCard | 100.029.115 | ||
EC Number |
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PubChem CID |
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UNII | |||
CompTox Dashboard (EPA) |
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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)[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 | |||
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)[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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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]
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.
Tellurium hexafluoride is much more chemically reactive than SF6.[6] For example, TeF6 slowly hydrolyzes to Te(OH)6:
Treatment of tellurium hexafluoride with tetramethylammonium fluoride (Me4NF) gives, sequentially, the hepta- and octafluorides:
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