XeOF 5 – and [(XeOF 4 ) 3 F] – anions

The XeOF5– and [(XeOF4)3F]– anions, which comprise a new class of xenon(VI) oxyfluoro-anion, have been synthesized as their caesium salts and their structures have been characterized for the first time using vibrational spectroscopy and X-ray powder diffraction; the XeOF5– anion displays a stereochemically active lone pair, and the polyanion [(XeOF4)3F]– consists of three equivalent XeOF4 groups bonded to an F– ion.