Gaseous ethylenexenonium ions (C2H4Xe+) and ethylenefluoroxenonium ions (C2H4XeF+): A joint mass spectrometric and theoretical study

Mass spectrometric experiments and density functional theory (DFT) calculat ions were performed in order to prepare and characterize gas eous ethylenex enonium ions, The model ion, C2H4Xe+ (1), prepared from XeF+ and ethylene, was experimentally and theoretically characterized as a bridged radical cat ion structurally reminescent of cyclic halonium ions such as C2H4I+. The et hylenefluoroxenonium ion, C2H4XeF+ (2), prepared from Xe2F+ or XeF2+ and C2 H4, is also a cyclic complex in which the XeF+ group is bound to the pi-ele ctron system. Strong evidence was obtained for the intermediacy of 2 in the formation of 1 from XeF+ and C2H4; this provides a mechanistic link betwee n the gas-phase results and the reactions of unsaturated compounds with XeF + salts, utilized in solution as stereoselective fluorinating agents.