NHC-Stabilized Silicon–Carbon Mixed Cumulene

The NHC-stabilized
silicon–carbon mixed cumulene (Me3Si)2CSi­(IPr)Si­(IPr)C­(SiMe3)2 (3, IPr = 1,3-diisopropyl-4,5-dimethyl-imidazol-2-ylidene)
has been prepared by reaction of Ar­(SiMe3)­NK with the NHC-stabilized
silene (Me3Si)2CSi­(SiMe3)­Cl­(IPr)
(2) in toluene at low temperature via the elimination
of trimethylsilyl and chloride groups from 2. X-ray crystal
analysis of 3 indicated the formal CSiSiC
cumulene skeleton with the short Si–Si double bond distance
of 2.1896(10) Å. DFT calculations disclosed its zwitterionic
character. Reaction of 3 with diphenylacetylene resulted
in the formation of a silatriafulvene with an exocyclic NHC-stabilized
silene moiety.

本研究通过低温甲苯溶剂中，由Ar(SiMe3)NK与经氮杂环卡宾（N-heterocyclic carbene, NHC）稳定的硅烯化合物(Me3Si)2C=Si(SiMe3)Cl(IPr)（化合物2）发生消除反应，脱除三甲基硅基与氯基团后，成功制备得到NHC稳定的硅碳混合累积多烯烃：(Me3Si)2C=Si(IPr)=Si(IPr)=C(SiMe3)2（化合物3，其中IPr=1,3-二异丙基-4,5-二甲基咪唑-2-叶立德）。对化合物3的X射线晶体衍射分析结果表明，其骨架为形式上的C=Si=Si=C累积双键体系，Si-Si双键键长为2.1896(10) Å。密度泛函理论（Density Functional Theory, DFT）计算显示该化合物具有两性离子特性。化合物3与二苯乙炔发生反应，可生成带有环外NHC稳定硅烯结构单元的硅杂三富烯产物。