Tellurium hexafluoride

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

Tellurium hexafluoride

Structure and dimensions of the molecule Ball-and-stick model of the molelcule
Identifiers
CAS Number	7783-80-4 Y
3D model (JSmol)	Interactive image
ECHA InfoCard	100.029.115
EC Number	232-027-0
PubChem CID	24559
UNII	JWI7143IXR Y
CompTox Dashboard (EPA)	DTXSID20893077
InChI InChI=1S/F6Te/c1-7(2,3,4,5)6
SMILES F[Te](F)(F)(F)(F)F
Properties
Chemical formula	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)[1]
Boiling point	−37.6 °C (−35.7 °F; 235.6 K)[1]
Solubility in water	decomposes
Vapor pressure	>1 atm (20°C)[2]
Magnetic susceptibility (χ)	−66.0·10−6 cm3/mol
Refractive index (nD)	1.0009
Structure
Crystal structure	Orthorhombic, oP28
Space group	Pnma, No. 62
Coordination geometry	octahedral (Oh)
Dipole moment	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). Y verify (what is YN ?) 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.^{[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.