Xenon tetrafluoride, XeF₄ is :

Xenon tetrafluoride, ${\mathrm{XeF}}_4$ is a chemical compound consisting of one xenon atom and four fluorine atoms, and it has a square planar geometry. In this geometry, the four fluorine atoms occupy the corners of a square around the central xenon atom.

${\mathrm{XeF}}_4$ is known to act as a fluoride donor in the presence of compounds such as ${\mathrm{PF}}_5$, which is also a fluoride acceptor. When ${\mathrm{XeF}}_4$ reacts with ${\mathrm{PF}}_5$, the following reaction takes place:

${\mathrm{XeF}}_4 + {\mathrm{PF}}_5 \to \left[{\mathrm{XeF}}_3^{+}\right]\left[{\mathrm{PF}}_6^{-}\right]$

In this reaction, XeF₄ donates a fluoride ion to PF₅, forming $\left[{\mathrm{PF}}_6^{-}\right]$ ion and a $\left[{\mathrm{XeF}}_3^{+}\right]$ cation. The $\left[{\mathrm{XeF}}_3^{+}\right]$ cation is a Lewis acid and can further react with other fluoride donors to form other fluoride complexes.

Overall, ${\mathrm{XeF}}_4$ ability to act as a fluoride donor is due to its high electron density on the xenon atom, which allows it to easily donate a fluoride ion to fluoride acceptors such as ${\mathrm{PF}}_5$.