This salt consists of tetramethylammonium cations [N(CH3)4]+ and pentafluoroxenate(IV) anions [XeF5]−.

The [XeF5]− ion was the first example of a pentagonal planar molecular geometry AX5E2 species.

[1] It was prepared by the reaction of [N(CH3)4]F with xenon tetrafluoride, [N(CH3)4]F being chosen because it can be prepared in anhydrous form and is readily soluble in organic solvents.

[1] The anion is planar, with the fluorine atoms in a slightly distorted pentagonal coordination (Xe–F bond lengths 197.9–203.4 pm, and F–X–F bond angles 71.5°–72.3°).

[1] Other salts have been prepared with sodium, caesium and rubidium, and vibrational spectra show that these contain the same planar ion.