Pentafluorophenylxenon(ii) pentafluorophenyltrifluoroborate, [C6F5Xe]+ [c6F56F3]-, can be prepared analogously to pentafluorophenylhalogen(iii) and (v) fluorides, C6F5kialF2 and C6F5HatF4 (with Hal = Br or I), by nucleophilic displacement of fluorine in XeF2 using B(C&)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.

The title compound containing a xenon‐carbon bond can be prepared by fluorine‐aryl substitution in XeF2 and crystallization from acetonitrile solution. The XeC bond has been characterized for the first time by a structure analysis : it is 2.092(8) Å long. Not shown in the picture on the right is the MeCN molecule coordinated to xenon.

Laser flash photolysis of 1 in solution leads to the formation of a short-lived triplet ( = 13.3 ns in acetonitrile) which decays via hydrogen abstraction from the remote hydroxy group. The resulting 1,13-biradical has a lifetime of 118 ns in acetonitrile and decays almost exclusively by back-hydrogen-transfer in a process that appears to be controlled by intersystem crossing. The valeryl analogue 2 is nonreactive with respect to Norrish II fragmentation in fluid solution ( < 0.001), presumably as a result of a shortened triplet lifetime due to efficient intramolecular phenolic quenching.

Durch Fluor‐Aryl‐Substitution an XeF2 und Kristallisation aus Acetonitril‐Lösung läßt sich die Titelverbindung mit einer Xenon‐Kohlenstoff‐Bindung herstellen. Erstmals konnte die Xe–C‐Bindung strukturanalytisch charakterisiert werden: Sie ist 2.092(8) Å lang. Nicht gezeigt im Bild rechts ist das an Xenon koordinierte MeCN‐Molekül.

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