CONTRIBUTIONS TO THE CHEMISTRY OF BROMINE TRIFLUORIDE - PART 3 - ELECTRONIC INFLUENCES ON THE FLUORINE-ARYL SUBSTITUTION-REACTION OF BROMINE TRIFLUORIDE WITH MONOSUBSTITUTED PHENYLTRIFLUOROSILANES

BrF3 reacts with monosubstituted phenyltrifluorosilanes X-C6H4SiF3 (X = H, p-Me, p-MeO, m-F, p-F, m-CF3, p-CF3) in equimolar reactions (CH2C l2/MeCN solution, optimised reaction temperature) with three different patterns of products. Electron-rich aryl groups (X = H, p-Me, p-MeO) are only fluorinated, brominated and oxidised by BrF3. Monofluorinated phenyltrifluorosilanes behave mainly like the electron-rich silanes, but additionally, in smaller amounts, (ca. 10%) disubstitution takes p lace on BrF3 with formation of [(X-C6H4)(2)Br][SiF5]. After metathesis the bromonium salts can be isolated as tetrafluoroborates or hexafluo rophosphates. When X = m-CF3 and p-CF3, monosubstitution becomes the m ain reaction and X-C6H4BrF2 can be isolated in good yields as first ex amples of hydrogen-containing phenylbromine difluorides. Their oxidati on potential is high enough to oxidise I-2 to IF5. Attempts to synthes ise p-CF3C6H4BrCl2 were not successful. (C) 1998 Elsevier Science S.A. All rights reserved.