Tellurium hexafluoride

Tellurium hexafluoride is the oldest known fluoride of tellurium. It is a colorless and highly toxic gas that has a horrible smell.

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Preparation

Tellurium hexafluoride is most commonly prepared by passing fluorine gas over tellurium metal 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.

Reactivity

Unlike the sulfur analog, tellurium hexafluoride is not chemically inert. This can be attributed to the greater availability of the d orbitals and perhaps the availability of the f orbitals which neither sulfur or selenium have access to. TeF₆ is hydrolyzed in water to H₆TeO₆ and reacts with Te below 200 °C.

Health Hazards

People exposed to tellurium compounds exhibit "tellurium breath", which has a garlic-like odour. This garlic odour is also present in sweat and urine. Other symptoms of tellurium exposure include headache, dyspnea, weakness, bluish-black markings on fingers, neck, face and gums, metallic taste in the mouth and skin rash. Death may occur from pulmonary edema. People exposed to tellurium compounds should be removed from the area and seek medical attention.

Reasons for "Tellurium-Breath"

The garlic odour that is associated with human intake of tellurium compounds is caused from the tellurium being metabolized by the body. When the body metabolizes tellurium in any oxidation state, the tellurium gets converted into dimethyl telluride. Dimethyl telluride is volatile and produces^{[citation needed]} the garlic-like smell.

Suppliers

Tellurium hexafluoride is not a very common chemical and can be found at only a few select suppilers (see below). It costs approximately 2000 USD for 50 grams.

• Pfaltz and Bauer
• Fox Chemicals

See also

• Tellurium

References

• 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.