Gas-phase fluorine migration reactions in the radical cations of pentafluorosulfanylbenzene (Aryl-SF₅) and benzenesulfonyl fluoride (Aryl-SO₂F) derivatives and in the 2,5-xylylfluoroiodonium ion.

The gas-phase reactions of Aryl-SF5(·+) and Aryl-SO2F(·+) have been studied with the electron ionization tandem mass spectrometry. Such reactions involve F-atom migration from the S-atom to the aryl group affording the product ion Aryl-F(·+) by subsequent expulsion of SF4 or SO2, respectively. Especially, the 4-pentafluorosulfanylphenyl cation 4-SF5C6H4(+) (m/z 203) from 4-NO2C6H4SF5(·+) by loss of ·NO2 could occur multiple F-atom migration reactions to the product ion C6H4F3(+) (m/z 133) by loss of SF2 in the MS/MS process. The gas-phase reactions of 2,5-xylylfluoroiodonium (pXyl-I(+)F, m/z 251) have also been studied using the electrospray tandem mass spectrometry, which involve a similar F-atom migration process from the I-atom to the aryl group giving the radical cation of 2-fluoro-p-xylene (or its isomer 4-fluoro-m-xylene, m/z 124) by reductive elimination of an iodine atom. All these gas-phase F-atom migration reactions from the heteroatom to the aryl group led to the aryl-F coupling product ions with a new formed C(Aryl)-F bond. Density functional theory calculations were performed to shed light on the mechanisms of these reactions.