Stable Silenolates and Brook-Type Silenes with Exocyclic Structures

The
first silenolates with exocyclic structures [(Me3Si)2Si­(Si2Me4)2SiC­(R)­O]−K+ (2a: R = 1-adamantyl; 2b:
mesityl; 2c: o-tolyl) were
synthesized by the reaction of the corresponding acylcyclohexasilanes 1a–c with KOtBu. NMR
spectroscopy and single-crystal X-ray diffraction analysis suggest
that the aryl-substituted silenolates 2b,c exhibit increased character of functionalized silenes as compared
to the alkyl-substituted derivative 2a due to the different
coordination of the K+ counterion to the SiC­(R)O moiety. 2b,c, thus, reacted with ClSiiPr3 to give the exocyclic silenes (Me3Si)2Si­(Si2Me4)2SiC­(OSiiPr3)­R (3b: R = Mes; 3c: o-Tol), while 2a afforded the Si-silylated
acylcyclohexasilane 1d. The thermally remarkably stable
compound 3b, which is the first isolated silene with
the sp2 silicon atom incorporated into a cyclopolysilane
framework, could be fully characterized structurally and spectroscopically.

本研究合成了首例具有环外结构的硅烯醇盐（silenolates）类化合物，其通式为[(Me₃Si)₂Si(Si₂Me₄)₂SiC(R)O]⁻K⁺，具体包括2a（R=1-金刚烷基）、2b（R=均三甲苯基（mesityl））、2c（R=邻甲苯基（o-tolyl））；该类化合物由相应的酰基环己硅烷（acylcyclohexasilanes）1a–c与叔丁醇钾（KOtBu）反应制得。核磁共振波谱（NMR spectroscopy）与单晶X射线衍射（single-crystal X-ray diffraction）分析结果显示，相较于烷基取代的衍生物2a，芳基取代的硅烯醇盐2b、2c因K⁺抗衡离子与SiC(R)O基团的配位模式存在差异，表现出更显著的官能化硅烯特征。因此，2b与2c可与三异丙基氯硅烷（ClSiiPr₃）反应，生成环外硅烯类化合物(Me₃Si)₂Si(Si₂Me₄)₂Si=C(OSiiPr₃)R（3b：R=均三甲苯基（Mes）；3c：R=邻甲苯基（o-Tol)）；而2a则生成了硅基化的酰基环己硅烷1d。热稳定性极为优异的化合物3b是首个成功分离得到的、将sp²杂化硅原子嵌入环聚硅烷（cyclopolysilane）骨架的硅烯，可通过结构与光谱手段完成全面表征。