Disilene R~*XSi=SiXR~* (R~* = SitBu_30 mit siliciumgebundenen H-und Hal-Atomen X: Bildung, Isomerisierung, Reaktionen

摘要

Dehalogenations of 1,2-disupersilyldisilanes R~*H2Si-SiHaIHR~*, R~*HHalSi-SiHalHR~*, R~*HHalSi-SiHaI2R~* and R~*HaI2Si-SiHaI2R~* in THF with equimolar amounts of supersilyl sodium NaR~* (R~* = SitBu3 = Supersilyl) lead slowly at room temperature (Hal = CI) or fast even at -78°C (Hal = Br, I) under exchange of one halogen Hal for sodium Na to yellow-orange disilanides R~*H2Si-SiNaHR~*, R~*HHaISi-SiNaHR~*, R~*HHaISi-SiNaHaIR~* and R~*HaI2Si-SiNaHalR~* (identification by proto- nation, methylation, silylation). These then, in the latter three cases, eliminate NaHal under formation of trans-l ,2-disupersilyl- disilenes R~*XSi=SiXR~* with silicon-bound H and Hal atoms as X. Actually produced are R~*HSi=SiHR~*, R~ *HSi=SiBrR~*, R~*CISi=SiCIR ., R~*BrSi=SiBrR~* and R~*ISi=SiIR~ * .The intermediate existence of the disilenes could be proved by trapping them with diphenylacetylene (formation of [2 + lfcycloadducts), with anthracene (formation of [4 + 2] cycloadducts), with benzophe- none (formation of [2 + 2] cycloadducts), and/or with 2,3-dimethylbutadiene (formation of (2 + 2] and [4 + 2] cycloadducts as well as ene reaction products). Obviously, isomerization of the disilenes R~*HalSi=SiHalR~* to silylenes R~*HaI2Si-SiR~* is possible, the latter of which may be trapp~d by Et_3SiH. In the absence of the mentioned traps, R~*HSi=SiHR~* thermolizes under formation of cyclotrisilanes RrSi_3B_3 and RrSi_3fJ_2R with R = SiH2R~* as well as cyclotetrasilanes R:Si4_H_4, whereas R~*HSi=SiBrR~* and R~*BrSi=SiBrR~* react to an unidentified mixture of substances. The disilene R~*ClSi=SiCIR~* forms in the presence of its source R~*CISi=SiNaCIR~* cyclotetrasilanes R:Si4C~ obviously by way of insertion into the SiNa bond of the latter followed by elimination of NaCl. Finally, R~*ISi=SiIR~* goes over into the cyclotrisilane R_~*Si_3I_2R with R = SiI_2R~*, the formation of which i could take place by way of [2 + 1] cycloaddition of the mentioned disilene and its isomer R~*I_2Si-Si~*.In the presence of NaR~*, the disilene R~*HSi=SiBrR~* forms endo,exo- and endo,endo-bicyclotetrasilanes R_4~*Si_4H_2. Thereby, at room temperature the pure endo,endo isomer slowly transforms into an equilibrium mixture of the endo.endo and the endo,exo isomer in the mole ratio of 1:9 (the reactions of R_4~*Si_4H_2 with 12 lead to cyclotrisilanes RjSi3HIR with R = SiHIR~* and cyclotetrasilanes R_4~8Si_4H_2I_2). On the other hand, the disilenes R~*HaISi=SiHilIR~* (Hal = Cl, Br, I) in the presence of NaR~* quantitatively transform, possibly via the ldisilenides R~*HalSi=SiNaR~* and cyclotetrasilenes R_4~8Si_4NaI_2' into the tetrahedrotetrasilane R_4~*Si4 (the tetrahedrane reacts with O_2, I_2, Na under formation of R_4~*Si_4O_2, R_4~*Si_4_2, R_4~*Si_4Na_2). X-ray structure analyses are presented for cis,cis,trans-R_4~8Si_4H_2I_2 as well as cis,trans,cis-R:Si4CI4 and the [2 + 2] cycloadducts of R~*BrSi=SiBrR~* with Ph2C=O and of R~*ClSi=SiCIR~* with CH_2=CMe-CMe=CH_2.