Tellurium tetrafluoride

Tellurium tetrafluoride, TeF₄, is a stable, white, hygroscopic crystalline solid and is one of three fluorides of tellurium. The other two binary fluorides are tellurium hexafluoride and ditellurium decafluoride^{[citation needed]}. There are other tellurium compounds that contain fluorine, but only the three mentioned contain solely tellurium and fluorine. Tellurium difluoride is not known.

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Preparation

Tellurium tetrafluoride can be prepared by the following reaction:

TeO₂ + 2SF₄ → TeF₄ + 2SOF₂

It is also prepared by reacting nitryl fluoride with tellurium or from the elements at 0 °C or by reacting selenium tetrafluoride with tellurium dioxide at 80 °C.
Fluorine in nitrogen can react with TeCl₂ or TeBr₂ to form TeF₄. PbF₂ will also fluorinate tellurium to TeF₄.

Reactivity

Tellurium tetrafluoride will react with water or silica and forms tellurium oxides. Copper, silver, gold or nickel will react with tellurium tetrafluoride at 185 °C. It does not react with platinum. It is soluble in SbF₅ and will precipitate out the complex TeF₄SbF₅.

Properties

Tellurium tetrafluoride melts at 130 °C and decomposes to tellurium hexafluoride at 194 °C. In the solid phase it consists of infinite chains of TeF₃F_2/2 in an octahedral geometry. A lone pair of electrons occupies the sixth position.

References

• R.B. King; Inorganic Chemistry of Main Group Elements, VCH Publishers, New York, 1995.
• W.C. Cooper; Tellurium, VanNostrand Reinhold Company, New York, 1971.