Nakamoto Masaaki, Fukawa Tomohide, Lee Vladimir Ya, Sekiguchi Akira
Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
J Am Chem Soc. 2002 Dec 25;124(51):15160-1. doi: 10.1021/ja021142r.
Pale-yellow crystals of the nonsolvated monomeric silyl- and germyllithiums, tris[di-tert-butyl(methyl)silyl]silyllithium 2a and tris[di-tert-butyl(methyl)silyl]germyllithium 2b, were obtained by one-electron reduction of the corresponding silyl and germyl radicals with lithium in hexane. The crystal structure analysis of both 2a and 2b showed almost planar geometry around the anionic centers, due to both intramolecular CH-Li agostic interactions and steric reasons. However, the free anions [(tBu2MeSi)3Si-][Li+(THF)4] 3a and [(tBu2MeSi)3Ge-][Li+(THF)n] (n = 3, 4) 3b no longer showed a planar geometry, because of the absence of the intramolecular CH-Li agostic interaction. A temperature-dependent 1H NMR study of 2a showed that the CH-Li interaction is weak.
通过在己烷中用锂对相应的甲硅烷基和锗烷基自由基进行单电子还原，得到了非溶剂化单体甲硅烷基锂和锗烷基锂的淡黄色晶体，即三[二叔丁基（甲基）甲硅烷基]甲硅烷基锂2a和三[二叔丁基（甲基）甲硅烷基]锗烷基锂2b。对2a和2b的晶体结构分析表明，由于分子内CH-Li（邻位）相互作用和空间位阻原因，阴离子中心周围几乎呈平面几何构型。然而，游离阴离子[(tBu2MeSi)3Si-][Li+(THF)4] 3a和[(tBu2MeSi)3Ge-][Li+(THF)n]（n = 3, 4）3b不再呈现平面几何构型，因为不存在分子内CH-Li（邻位）相互作用。对2a的变温1H NMR研究表明，CH-Li相互作用较弱。
