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 ranging from 197.9 - 203.4 pm and Xe-F bond angles ranging from 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.
^ abcdChriste K. O., Curtis E. C., Dixon D. A., Mercier H. P.,. Sanders J. C. P, Schrobilgen G. J. (1991). "The pentafluoroxenate(IV) anion, XeF5−: the first example of a pentagonal planar AX5 species". J. Am. Chem. Soc.113 (9): 3351–3361. doi:10.1021/ja00009a021.