Syntheses of Trisila Analogues of Allyl Chlorides and Their Transformations to Chlorocyclotrisilanes, Cyclotrisilanides, and a Trisilaindane

The rearrangements of (chlorosilyl)disilenes R2(Cl)Si−(Tip)SiSiTip2 (5a,b:  Tip = 2,4,6-iPr3C6H2,
a:  R = Me, b:  R = Ph) quantitatively yield the isomeric chlorocyclotrisilanes (6a,b). The disilene precursors
5a,b are, in turn, accessible from the reactions of the disilenide Tip2SiSi(Tip)Li (1), that is, a disila analogue
to vinyl anions, with dichlorosilanes R2SiCl2. This novel approach to cyclotrisilanes potentially allows for
the facile variation of the substitution pattern and grants access to the first anionic derivatives; while the
rearrangement of 5a,b to 6a,b is slow at room temperature and additionally requires the presence of THF
or other n-donors, reduction of 5b with lithium instantly yields the corresponding cyclotrisilanide (7b) without
detection of any open-chained isomer. Heating of a neat sample of 5b to 150 °C provides a completely
characterized 1,2,3-trisilaindane derivative (13), strongly supporting the intermediacy of a disilanyl silylene
species that inserts into an ortho-CH bond of the phenyl substituents. The X-ray diffraction studies on
single crystals of 6a,b and 7b reveal that the Si−Si bond distance in cyclotrisilanes depends significantly
on the electronegativity of the opposing silicon atom's substituents, which is rationalized by density functional
theory (DFT) calculations on model systems.

（氯硅基）二硅烯 ((chlorosilyl)disilenes) 类化合物R₂(Cl)Si−(Tip)Si=SiTip₂（5a,b：其中Tip为2,4,6-三异丙基苯基（Tip, 2,4,6-iPr₃C₆H₂）；a中R为甲基（Me），b中R为苯基（Ph））可发生重排反应，定量生成对应的异构体氯代环三硅烷（6a,b）。作为反应前体的二硅烯5a,b，可通过二硅烯负离子（disilenide）Tip₂Si=Si(Tip)Li（1，即与乙烯基负离子类似的二硅杂乙烯基负离子）与二氯硅烷（dichlorosilanes）R₂SiCl₂的反应制备得到。这种合成环三硅烷（cyclotrisilanes）的新方法，可便捷调控取代模式，且首次实现了其阴离子衍生物（anionic derivatives）的制备；尽管5a,b向6a,b的重排反应在室温下速率较慢，且需要四氢呋喃（THF）或其他氮给体（n-donors）参与，但用金属锂还原5b可瞬时得到对应的环三硅烷负离子（7b），且未检测到任何开链异构体副产物。将纯态的5b样品加热至150℃，可得到经全面表征的1,2,3-三硅杂茚衍生物（13），该结果有力证实了反应中间体为二硅烷基硅烯物种，其可插入苯环取代基的邻位C-H键中。对6a,b和7b的单晶开展X射线衍射分析后发现，环三硅烷中的Si-Si键长显著取决于相连硅原子取代基的电负性，该实验结果可通过模型体系的密度泛函理论（DFT）计算得到合理解释。