Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
Chemistry. 2011 Oct 10;17(42):11797-804. doi: 10.1002/chem.201101484. Epub 2011 Sep 7.
Elusive perchloropyracylene has been obtained during conventional fullerene synthesis in a chlorine-containing atmosphere by using the radio-frequency furnace technique. In contrast to its hydrocarbon analogue, the title compound was found to be unexpectedly stable. Although the high stability of perchloropyracylene impedes its direct addition to C(60) fullerene, the corresponding adduct was found in the synthesis products extracted from the raw soot. Both new species were separated and unambiguously characterized by single-crystal X-ray analysis. According to experimental observations and quantum chemical calculations, the addition of perchloropyracylene to the C(60) fullerene can only be realized by involving highly reactive species such as C(14) clusters displaying the pyracylene connectivity. Such a viable mechanism includes capturing of free or partially chlorinated C(14) clusters with pyracylene-type connectivity by the fullerene molecule and subsequent stabilization through chlorine addition. The data obtained provide experimental evidence for the presence of pyracylene-like C(14) clusters in the gas phase, which have evolved during the graphite vaporization process. According to the pentagon road mechanism, such clusters are regarded as crucial intermediates in fullerene formation.
在含氯气氛中使用射频炉技术进行常规富勒烯合成时，得到了难以捉摸的全氯吡咯并[3,4-c]吡咯。与碳氢化合物类似物相比，标题化合物出人意料地稳定。尽管全氯吡咯并[3,4-c]吡咯的高稳定性阻碍了其直接加成到 C(60)富勒烯上，但在从原始烟尘中提取的合成产物中发现了相应的加合物。这两种新物质都通过单晶 X 射线分析得到了分离和明确的表征。根据实验观察和量子化学计算，只有涉及具有吡咯并连接性的高反应性物质（如显示吡咯并连接性的 C(14)簇），才能将全氯吡咯并[3,4-c]吡咯加成到 C(60)富勒烯上。这种可行的机制包括富勒烯分子捕获自由或部分氯化的 C(14)簇，并通过氯加成稳定。所获得的数据为气相中存在吡咯并[3,4-c]吡咯类似的 C(14)簇提供了实验证据，这些簇在石墨蒸发过程中演变而来。根据五元环路径机制，此类簇被认为是富勒烯形成的关键中间体。
