Due to the much less effective sp-hybridization of silicon atom in comparison with carbon atom, the silicon-containing π systems with consecutive double bonds have been much less studied. Prof. Chunming Cui' group has recently reported  the synthesis and structure of the isolable crystalline NHC-stabilized 2,3-disilabutatriene derivativecontaining a formal R₂C═Si═Si═CR₂ cumulene skeleton stabilized by complexation of the two silicon atoms with 1,3-diisopropyl-4,5-dimethyl-imidazol-2-ylidene.

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. 

Link: http://pubs.acs.org/doi/full/10.1021/jacs.6b06960.