Reaction of a Disilyne with Internal Alkynes: Reversible [1 + 2] Cycloaddition and Formation of Strained Unsaturated Silacycles.

The reactions of NHB-stabilized disilyne (NHB)Si≡Si(NHB) ( 1 , NHB = [ArN(CMe) 2 NAr]B, Ar = 2,6- i Pr 2 C 6 H 3 ) with internal alkynes were described. Reaction of disilyne 1 with one equivalent of bis(trimethylsilyl)acetylene led to a reversible [1 + 2] cycloaddition of one of the Si atoms with the alkyne and the insertion of the other Si into one of Ar rings with the formation of a silirenyl-silepin 2 , whereas reaction of 1 with two equivalents of Me 3 SiCCSiMe 3 resulted in the formal addition of the C sp -Si bond to the Si≡Si triple bond to give disilene (NHB)(Me 3 Si)Si=Si(CCSiMe 3 )(NHB). Reaction of 1 with 1,3-diyne Me 3 SiCCCCSiMe 3 yielded a 1,2-disilacyclobut-3-ene via cycloaddition, ring expansion, and NHB 1,2-shift sequence. The initial [1 + 2] cycloaddition of one of the silicon atoms with an alkyne was strongly supported by DFT calculations. The results demonstrated the significant bis(silylene) character and rich synthetic potential of bis(boryl) disilyne 1 .