Using Xenon Difluoride and 2 Li[Al{OC(CF3)3}4] as an Oxidant: From Organoxenonium Intermediates to (Fluoro-)Biphenyl Radical Cations

Abstract

The feasibility of employing the XeF2/2Li[Al(ORF)4] (ORF = OC(CF3)3) system as a deelectronator, formally generating Xe(g) + 2 LiF(s) + 2 ▢+, was investigated. While this proved successful for substrates like ferrocene and 9,10-dichlorooctafluoroanthracene, the system was found to react with the solvents benzene, fluorobenzene (FB) and 1,2-difluoro¬benzene (2FB). The reaction led to the formation of biphenyl radical cations as arene coupling products. In contrast, the reaction with 1,2,3-trifluorobenzene (3FB) allowed the observation of a persistent organoxenonium ion. Low-temperature NMR control reactions and quantum chemical calculations suggest a xenonium-mediated coupling reaction with organoxenonium ions as inter¬mediates. As a reference for the organoxenonium ions proposed, the perfluorinated tight ion-pair (C6F5)Xe-F-Al(ORF)3 and the salt [C6F5Xe][F{Al(ORF)3}2] were synthesized to assess their stability in combination with the alkoxyaluminate anions used in this work. Oxidation studies showed pronounced solvent effects, with strong oxidation observed in pentafluorobenzene, while in MeCN ferrocene was found to be oxidized already by XeF2 alone. These findings not only expand the synthetic utility of XeF₂-based oxidation systems but also provide new insight into the reactivity of organoxenonium ions, contributing to the growing understanding of the role of xenon chemistry in selective oxidative transformations.