Sekiguchi Akira, Fukawa Tomohide, Nakamoto Masaaki, Lee Vladimir Ya, Ichinohe Masaaki
Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
J Am Chem Soc. 2002 Aug 21;124(33):9865-9. doi: 10.1021/ja0126780.
The one-electron oxidation reaction of tris[di-tert-butyl(methyl)silyl]silyl and -germyl anions with dichlorogermylene-dioxane complex results in the formation of stable tris[di-tert-butyl(methyl)silyl]silyl and -germyl radicals 1 and 2, representing the first isolable radical species of heavier Group 14 elements lacking stabilization by conjugation with pi-bonds. The crystal structures of both silyl and germyl radicals 1 and 2 showed a completely planar geometry around the radical centers. The ESR spectra of 1 and 2 showed strong signals with characteristic satellites due to the coupling with the 29Si and 73Ge nuclei. The small values of the hyperfine coupling constants a(29Si) and a(73Ge) clearly indicate the pi-character of both radicals, corresponding to a planar geometry and sp2 hybridization of the radical centers. Both 1 and 2 easily undergo halogenation reactions with carbon tetrachloride, 1,2-dibromoethane, and benzyl bromide to form the corresponding halosilanes and halogermanes.
三[二叔丁基（甲基）甲硅烷基]甲硅烷基和锗烷基阴离子与二氯锗烯 - 二氧六环配合物的单电子氧化反应生成了稳定的三[二叔丁基（甲基）甲硅烷基]甲硅烷基和锗烷基自由基1和2，这代表了第14主族较重元素的首个可分离的自由基物种，其缺乏通过与π键共轭来实现的稳定化。甲硅烷基和锗烷基自由基1和2的晶体结构显示在自由基中心周围具有完全平面的几何形状。1和2的电子自旋共振（ESR）光谱显示出强信号以及由于与29Si和73Ge核耦合而产生的特征性卫星峰。超精细耦合常数a(29Si)和a(73Ge)的小值清楚地表明了这两个自由基的π特性，这与自由基中心的平面几何形状和sp2杂化相对应。1和2都很容易与四氯化碳、1,2 - 二溴乙烷和苄基溴发生卤化反应，形成相应的卤代硅烷和卤代锗烷。
