Tetramethylammonium pentafluoroxenate

Tetramethylammonium pentafluoroxenate is the chemical compound with the formula N(CH₃)₄XeF₅. The XeF−
5 ion it contains was the first example of a planar pentagonal AX₅E₂ species. It was prepared by the reaction of N(CH₃)₄F with xenon tetrafluoride, N(CH₃)₄F being chosen because it can be prepared in anhydrous form and is readily soluble in organic solvents. 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°). Other salts have been prepared with sodium, caesium and rubidium, and vibrational spectra shows that these contain the same planar ion. The isolated anion has the unusual point group of D_5d.