Distinct reactivities of cis- and trans-RFCF=CFBF2 towards XeF2 and the first synthesis of a [trans-RFCF=CFXe]+ salt

University of Duisburg-Essen, Essen, North Rhine-Westphalia, Germany
Mendeleev Communications (Impact Factor: 1.34). 05/2007; 17(3):137–138. DOI: 10.1016/j.mencom.2007.05.001


The competitive reaction of C4F9CF=CFBF2 (Cis: trans = 1.2: 1) with XeF2 demonstrated for the first time a remarkably lower reaction rate of the trans isomer with respect to the cis isomer in the xenodeborylation reaction (formation of the [C4F9CF=CFXe](+) cation with a cis: trans ratio of 2.5 to 4:1) and allowed us to develop reaction conditions for the syntheses of [trans-C4F9CF=CFXe](+) salts.

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    ABSTRACT: The replacement of xenon(+) by iodine in reactions of alkenylxenonium(II) salts [RCF=CFXe]Y (R = cis-C2F5, trans-H) and alkynylxenonium(II) salt [C3F7C≡CXe][BF4] with NaI in anhydrous HF (aHF) occurred regiospecifically. At −60 °C the substitution of xenon(+) by bromine in the perfluorinated salts [cis-CF3CF=CFXe]Y and [trans-C4F9CF=CFXe]Y proceeded regio- and stereospecifically with NaBr in aHF, but at a higher temperature and after a longer time the treatment of [cis-C2F5CF=CFXe]Y with NaBr, KBr, or [NBu4]Br in aHF gave mixtures of cisand trans-perfluorobut-1-enyl bromides. The reaction of [C3F7C≡CXe][BF4] with NaBr in aHF at −65 °C gave only 48 %, of C3F7C≡CBr and was accompanied by a mixture of bromine-containing related olefins. Reaction pathways to the main product are discussed.
    No preview · Article · Aug 2007 · Zeitschrift für anorganische Chemie
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    ABSTRACT: New examples of [C6F5Xe]+ salts of the weakly coordinating anions [B(CF3)4]-, [B(C6F5)4]-, [B(CN)4]-, and [B(OTeF5)4]- have been synthesized by metathesis reactions of [C6F5Xe][BF4] with the corresponding MI[BY4] salts (MI = K or Cs; Y = CF3, C6F5, CN, or OTeF5). The salts were characterized in solution by multi-NMR spectroscopy. Their stabilities in prototypic solvents (CH3CN and CH2Cl2) and decomposition products are reported. The influence of the coordinating nature of [BY4]- on the decomposition rate of [C6F5Xe]+ as well as the presence of the weakly nucleophilic [BF4]- ion has been studied. The electrophilic pentafluorophenylation of C6H5F by [C6F5Xe][BY4] in solvents of different coordinating abilities (CH3CN and CH2Cl2) and the effects of stronger nucleophiles (fluoride and water) on the pentafluorophenylation process have been investigated. Simulations of the 19F and 129Xe NMR spectra of [C6F5Xe]+ have provided the complete set of aryl 19F-19F and 129Xe-19F coupling constants and their relative signs. The 19F NMR parameters of the [C6F5Xe]+ cation in the present series of salts are shown to reflect the relative degrees of cation-solvent interactions.
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    ABSTRACT: The reaction of alkynyldifluoroboranes RC≡CBF2 (R = (CH3)3C, CF3, (CF3)2CF) with organyliodine difluoride R′IF2 bearing electron-withdrawing polyfluoroorganyl groups R′ = C6F5, (CF3)2CFCF=CF, C4F9, and CF3CH2 leads to the corresponding alkynyl(organyl)iodonium salts [(RC≡C)(R′)I][BF4]. This approach uses a widely applicable method as demonstrated for a representative series of polyfluorinated aryl-, alkenyl-, and alkyliodine difluorides. Generally, these syntheses proceed with good yields and deliver pure iodonium salts. The distinct electrophilic nature of their [(RC≡C)(R′)I]+ cations is deduced from multinuclear magnetic resonance data. Within the series of new iodonium salts [CF3C≡C(C4F9)I][BF4] is an intrinsic unstable one and decomposed forming CF3C≡CI and C4F10.
    No preview · Article · Jan 2008 · Zeitschrift für anorganische Chemie
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