The pentafluorophenylxenon( II ) cation: [C 6 F 5 Xe] + ; the first stable system with a xenon–carbon bond

Pentafluorophenylxenon(II) pentafluorophenyltrifluoroborate, [C6F5Xe]+[C6F5BF3]–, can be prepared analogously to pentafluorophenylhalogen(III) and (V) fluorides, C6F5HalF2 and C6F5HalF4(with Hal = Br or I), by nucleophilic displacement of fluorine in XeF2 using B(C6F5)3 as an aryl-transfer reagent; the resulting colourless solid with a stable xenon–carbon bond is characterised in solution by 129Xe and 19F n.m.r. and chemically as an electrophilic transfer reagent for pentafluorophenyl groups.