Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
J Am Chem Soc. 2013 Jun 19;135(24):8794-7. doi: 10.1021/ja403173e. Epub 2013 Jun 5.
Pyramidane is an elusive but highly desirable target for synthetic chemists that has attracted a great deal of attention because of its nonclassical structure and unusual bonding features. Although well studied on theoretical grounds, neither the parent all-carbon pyramidane nor its derivatives containing heavier group 14 elements have ever been isolated and characterized. In this Communication, we report on the synthesis and structural elucidation of the first stable representatives of this class of highly strained polyhedral compounds: germa- and stannapyramidanes Ge[C4(SiMe3)4] and Sn[C4(SiMe3)4]. The peculiar structural and bonding features of these compounds are verified by combined experimental and computational analyses, showing these derivatives to be nonclassical neutral compounds with a very large contribution of ionic character.
笼烷是合成化学家梦寐以求的目标，但由于其非经典结构和不寻常的成键特征，一直难以捉摸。尽管在理论上已经进行了很好的研究，但无论是原始的全碳笼烷还是含有较重的第 14 族元素的衍生物都从未被分离和表征过。在本通讯中，我们报告了第一个稳定的此类高度应变多面体化合物的合成和结构阐明：锗[C4(SiMe3)4]和锡[C4(SiMe3)4]笼烷。通过综合实验和计算分析验证了这些化合物的特殊结构和成键特征，表明这些衍生物是非经典的中性化合物，具有很大的离子特性贡献。
