Tellurium tetrafluoride
# Tellurium tetrafluoride

Tellurium tetrafluoride, $TeF_4,$ is a stable, white, hygroscopic crystalline solid and is one of two fluorides of tellurium. The other binary fluoride is tellurium hexafluoride. The widely reported $Te_2F_{10}$ has been shown to be $F_5TeOTeF_5$ There are other tellurium compounds that contain fluorine, but only the two mentioned contain solely tellurium and fluorine. Tellurium difluoride, $TeF_2,$ and ditellurium difluoride, $Te_2F_2$ are not known.

## Preparation

Tellurium tetrafluoride can be prepared by the following reaction:

    $TeO_2$ + $2SF_4$ → $TeF_4$ + $2SOF_2$

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 $TeCl_2$ or $TeBr_2$ to form $TeF_4.$ $PbF_2$ will also fluorinate tellurium to $TeF_4.$

## 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 $SbF_5$ and will precipitate out the complex $TeF_4SbF_5.$

## 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 $TeF_3F_{2/2}$ in an octahedral geometry. A lone pair of electrons occupies the sixth position.

