The First Bicyclic System with σ(Si–Si)-π Conjugation. Synthesis of Bicyclo[6.6.0]-1,8-diisopropyl-4,4,5,5,11,11,12,12-octamethyl-1,4,5,8,11,12-hexasila-2,6,9,13-tetrayne
cis- and trans-Dibenzo[c,h]-1,6-diisopropyl-1,6-disilabicyclo[4.4.0]deca-3,8-dienes were prepared. Strong σ-π conjugation was found to operate in both isomers, which was shown in UV spectra, cyclic voltammetry, and charge-transfer spectra with TCNE.
The title ladder polysilane was synthesized by the cross-coupling of all-trans-[(t-Bu)ClSi]4 and Cl(i-Pr)2SiSi(i-Pr)2Cl with lithium in 40% yield. X-ray crystallographic analysis of the ladder polysilane shows a highly strained silicon skeleton; the Si-Si bond lengths vary from 2.412(3) to 2.481(2) Å and the Si-Si-Si bond angles of the Si4 rings range from 87.9(1) to 90.5(1)°. By comparison of the structure and UV-visible spectra of this compound with those of the perisopropyl analog, we found that the structures and properties of ladder polysilanes are strongly affected by the substituents.
通过全反式-[(t-Bu)ClSi]4 和 Cl(i-Pr)2SiSi(i-Pr)2Cl 与锂的交叉偶联合成标题梯形聚硅烷,产率 40%。梯形聚硅烷的 X 射线晶体分析显示出高度应变的硅骨架; Si-Si键长为2.412(3)至2.481(2) Å,Si4环的Si-Si-Si键角为87.9(1)至90.5(1)°。通过将该化合物与过异丙基类似物的结构和紫外可见光谱进行比较,我们发现梯形聚硅烷的结构和性能受取代基的强烈影响。
The first bicyclo[2.2.0]hexasilane system: synthesis of decaisopropylhexasilabicyclo[2.2.0]hexane
The first bicyclo[2.2.0]hexasilane, decaisopropylhexasilabicyclo[2.2.0]hexane was synthesized by the co-condensation of 1,1,2,2-tetrachlorodi-isopropyldisilane and 1,2-dichlorotetraisopropyldisilane with lithium in tetrahydrofuran.
The X-ray analysis disclosed that the title compound has a cis-fused structure. The bicyclic skeleton is twisted and has C2 symetry; the puckering of each four-membered ring is 21.8°. The central Si–Si bond distance, 239.6 pm, is comparable to those found for the peripheral Si–Si bonds, which range from 238.5 to 242.6 pm.
Synthesis, structures, and oxidation of the ladder oligosilanes, such as bicyclo[2.2.0]hexasilane, tricyclo-[4.2.0.02,5]octasilane, tetracyclo[4.4.0.02,5.07,10]decasilane, and pentacyclo[6.4.0.02,7.03,6.09,12]dodecasilane, are reported.