Bis(perfluoroorganyl)bromonium salts [(RF)2Br]Y (RF = aryl, alkenyl, and alkynyl)

Bromonium salts [(RF)2Br]Y with perfluorinated groups RFC6F5, CF3CFCF, C2F5CFCF, and CF3C≡C were isolated from reactions of BrF3 with RFBF2 in weakly coordinating solvents (wcs) like CF3CH2CHF2 (PFP) or CF3CH2CF2CH3 (PFB) in 30–90% yields. C6F5BF2 formed independent of the stoichiometry only [(C6F5)2Br][BF4]. 1:2 reactions of BrF3 and silanes C6F5SiY3 (Y = F, Me) ended with different products – C6F5BrF2 or [(C6F5)2Br][SiF5] – as pure individuals, depending on Y and on the reaction temperature (Y = F). With C6F5SiF3 at ≥−30 °C [(C6F5)2Br][SiF5] resulted in 92% yield whereas the reaction with less Lewis acidic C6F5SiMe3 only led to C6F5BrF2 (58%). The interaction of K[C6F5BF3] with BrF3 or [BrF2][SbF6] in anhydrous HF gave [(C6F5)2Br][SbF6]. Attempts to obtain a bis(perfluoroalkyl)bromonium salt by reactions of C6F13BF2 with BrF3 or of K[C6F13BF3] with [BrF2][SbF6] failed. The 3:2 reactions of BrF3 with (C6F5)3B in CH2Cl2 gave [(C6F5)2Br][(C6F5)nBF4−n] salts (n = 0–3). The mixture of anions could be converted to pure [BF4]− salts by treatment with BF3·base.

Systematic investigation of the substitution of fluorine by perfluoroorganyl groups RF in BrF3 and [BrF2]+ salts. Preparative access to bromonium salts [(RF)2Br]Y (Y = [BF4]−, [RFBF3]−) by reactions of BrF3 with RFBF2 (RFC6F5, CF3C≡C, trans-CF3CFCF, cis-C2F5CFCF).Figure optionsDownload as PowerPoint slide