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

Abstract

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.

Group 4 Metallocene Complexes of Tris(trimethylsilyl)silylacetylene and Related Alkynes

“…The rearrangement products derived from 1,1-bis(phenylethynyl)silanes give a distinct pattern for the former alkynyl carbons of resonances around 265, 210, 155, and 80 ppm for the Cp 2 Ti fragment and 255, 210, 160, and 100 ppm for Cp 2 Zr . Compounds 22 (Ti) and 24 (Zr) of this study also fall into these ranges.…”

“…The reactions of 1,1-bis(alkynyl)silanes with titanocene and zirconocene , fragments have been studied for several cases. The outcome of the reaction of 21 with titanocene is characterized by the formation of the silacyclobutene-annelated titanacyclobutene complex 22 (Scheme ).…”

Synthesis of Siloles (and Germoles) that Exhibit the AIE Effect

“…A novel twist on the reaction occurred when 0.5 equiv. of 'Cp 2 Zr' was reacted with R 2 Si(C À À À À À À CR 0 ) 2 (R¼ Ph, Me; R 0 ¼ Ph or alkyl; the same type of precursor used in both the Tamao and Wrackmeyer procedures) provided, after iodination, 1,4-diiodo-1,4-bis{(RC À À À À À À C) Me 2 Si} 2 -3,4-R 0 2 -butadiene [56]. Two reviews described butadiene building blocks and the synthetic applications of 1,4-dilithio-1,3-dienes [57a,b].…”

Formation of silacycles via metal-mediated or catalyzed Si-C bond cleavage

“…They also observed that the metal-to-diyne ratio played a key role in this zirconocene-mediated reaction of Si-tethered diynes. Upon increasing the ratio of Cp 2 ZrBu 2 : diyne from 2 : 1 to 1 : 1, reversible Si-C bond cleavage and formation was observed [54][55][56][57][58]. (10) According to their persistence, Xi and co-workers [59] developed the reaction of zirconacyclobutene-silacyclo butenes with nitriles into a versatile "tool-box" for preparation of various Si and N containing heterocycles.…”