HYPERFLUORINATION OF [60]FULLERENE BY KRYPTON DIFLUORIDE

Mass spectroscopy of the product of [60]fullerene fluorination by KrF2 in HF, shows the most abundant species present to be C60F44 and C60F46; cage-opened compounds with molecular formulae up to C60F78 are also present. Despite long exposure of the samples td air prior to analysis, oxygenated derivatives (containing one or two oxygen atoms) are present in low concentration only. The ubiquitous oxygen content of fluorofullerenes does not therefore appear to arise substantially from atmospheric contamination. The EI mass spectrum differs from that obtained with F-2-fluorinated [60]fullerene in showing a greater concentration of fragmentation ions, including species of even mass; these latter may arise from cage-opened species. The F-19 NMR spectrum of the product (tetrahydrofuran solution) is similar to that found with F-2-fluorinated material, and in particular shows the sharp singlet at ca. 151 ppm, attributed previously to a symmetrical species such as C60F60. With aqueous methanol, significant reaction does not occur, in marked contrast to the behaviour of fluorine-gas fluorinated [60]fullerene; possible reasons for this difference are considered.