Tellurium hexafluoride

Tellurium hexafluoride

Structure and dimensions of the molecule Ball-and-stick model of the molelcule
Identifiers
CAS Number	7783-80-4 Y
EC Number	232-027-0
Jmol 3D model	Interactive image
PubChem	24559
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 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)
Boiling point	−37.6 °C (−35.7 °F; 235.6 K)
Solubility in water	decomposes
Vapor pressure	>1 atm (20°C)
Refractive index (nD)	1.0009
Structure
Crystal structure	Orthorhombic, oP28
Space group	Pnma, No. 62
Coordination geometry	octahedral (Oh)
Dipole moment	0
Thermochemistry
Specific heat capacity (C)	117.6 J/(mol K)
Std enthalpy of formation (ΔfHo298)	-1318 kJ/mol
Vapor pressure	{{{value}}}
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

Tellurium hexafluoride is a chemical compound of tellurium and fluorine with the chemical formula TeF₆. It is a colorless, highly toxic gas with an extremely unpleasant smell.

Preparation

Tellurium hexafluoride is most commonly prepared by passing fluorine gas over tellurium at 150 °C. Below this temperature a mixture of lower fluorides form, including tellurium tetrafluoride and ditellurium decafluoride. It can also be prepared by passing fluorine gas over TeO₃ or indirectly by reacting TeO₂ with SeF₄ to produce TeF₄ and then heating TeF₄ in excess of 200 °C to make TeF₆ and Te.

Properties

Tellurium hexafluoride is a highly symmetric octahedral molecule. Its physical properties resemble the sulfur and selenium analogs. It is less volatile, however, due to the increase in molecular weight. 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

Unlike the sulfur analog, tellurium hexafluoride is not chemically inert. This can be attributed to the larger atomic radius which can co-ordinate a maximum of eight atoms rather than six for sulfur and selenium which allows for nucleophilic attack. TeF₆ is hydrolyzed in water to Te(OH)₆ and reacts with Te below 200 °C.

Literature

• 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.
• N.N. Greenwood and A. Earnshaw; Chemistry of the Elements, 2nd edition, Butterworth, UK, 1997.
• 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.

External links

• Web Elements
• OSHA
• CDC - NIOSH Pocket Guide to Chemical Hazards