Isolation and Synthetic Applications of 2,5-Bis(alkynylsilyl) Zirconacyclopentadienes

2,5-Bis(alkynylsilyl)-1-zirconacyclopentadienes 3 were formed highly regio- and chemoselectively in excellent yield by the homocoupling reaction of 2 equiv of bis(alkynyl)silanes 1 mediated by a low-valent zirconocene species (Negishi reagent) generated in situ from Cp2ZrBu2. Single-crystal X-ray structural analysis of 2,5-bis(phenylalkynyldimethylsilyl)-1-zirconacyclopentadiene (3a) revealed a sandwich-type conformation. Hydrolysis or halogenation of these zirconacyclopentadienes 3 afforded multisubstituted stereodefined Si-bridged conjugated systems. Skeletal rearrangement of these 2,5-bis(alkynylsilyl)-1-zirconacyclopentadienes with aromatic substituents afforded zirconacyclohexadiene−silacyclobutene fused ring compounds 4. Using these zirconacyclopentadienes 3 as starting reactive organometallic reagents, interesting cyclic compounds such as bis(alkynylsilyl)benzene derivatives and bis(alkynylsilyl)thiophene derivatives could be prepared in high yield. Further applications of these alkynylsilyl-substituted compounds for more complicated products and functional materials can be expected.