Pichaandi Kothanda Rama, Mague Joel T, Fink Mark J
Department of Chemistry, Tulane University, New Orleans, LA 70118, USA.
Acta Crystallogr E Crystallogr Commun. 2017 Feb 28;73(Pt 3):448-452. doi: 10.1107/S2056989017002602. eCollection 2017 Mar 1.
In the three sterically congested silanes, CHSi () (1,1,2,2-tetra-isopropyl-1,2-di-phenyl-disilane), CHBr4Si () [1,1,2,2-tetra-kis-(2-bromo-propan-2-yl)-1,2-di-phenyl-disilane] and CHSi () (1,2-di--butyl-1,1,2,2-tetra-phenyl-disilane), the Si-Si bond length is shortest in () and longest in (), with () having an inter-mediate value, which parallels the increasing steric congestion. A comparison of the two isopropyl derivatives, ( and ), shows a significant increase in the Si-C() distance with the introduction of bromine. Also, in the brominated compound , attractive inter-molecular Br⋯Br inter-actions exist with Br⋯Br separations 0.52 Å shorter than the sum of the van der Waals radii. In compound , one of the bromo-isopropyl groups is rotationally disordered in an 0.8812 (9):0.1188 (9) ratio. Compound exhibits 'whole mol-ecule' disorder in a 0.9645 (7):0.0355 (7) ratio with the Si-Si bonds in the two components making an angle of 66°.
在三种空间位阻较大的硅烷中，即CHSi（）（1,1,2,2 - 四异丙基 - 1,2 - 二苯基二硅烷）、CHBr₄Si（）[1,1,2,2 - 四 - （2 - 溴 - 丙 - 2 - 基）- 1,2 - 二苯基二硅烷]和CHSi（）（1,2 - 二 - 叔丁基 - 1,1,2,2 - 四苯基二硅烷）中，Si - Si键长在（）中最短，在（）中最长，（）具有中间值，这与空间位阻的增加情况平行。两种异丙基衍生物（和）的比较表明，引入溴后Si - C（）距离显著增加。此外，在溴化化合物中，存在有吸引力的分子间Br⋯Br相互作用，Br⋯Br间距比范德华半径之和短0.52 Å。在化合物中，其中一个溴代异丙基以0.8812（9）:0.1188（9）的比例呈旋转无序状态。化合物以0.9645（7）:0.0355（7）的比例呈现“整个分子”无序，两种组分中的Si - Si键夹角为66°。
