Supersilylsilane R*SiX3: Conversion into disilanes R*X2Si-SiX2R*, silylenes R*XSi, cyclosilanes (R*XSi)(n), disilenes R*XSi=SiXR*, tetrasupersilyl-tetrahedro-tetrasilane [German]

摘要

Supersilylmonohalosilanes R*RSiHCl (R* = Supersilyl = SitBu(3)) react with Na in C6H6 at 65 degrees C or with NaC10H8 in THF at -78 degrees C with formation of disupersilyldisilanes R*RWSi-SiHRR* in quantitative (R = H, Me) or moderate yields (R = Ph). In the latter case, R*PhSiH2 is obtained additionally at 65 degrees C (exclusively with Na in THF at 65 degrees C). Obviously the supersilylsilanides NaSiHRR* are generated as intermediates which react with cducts R*RSiHCl with NaCl elimination and formation of R*RHSi-SiHRR* (R = H, Me) or R*RSiH2 and R*RSi (R = Ph). The silylene intermediate R*PhSi inserts into the SiH-bonds of the educt R*PhSiHCl and of the product R*PhSiH2 with formation of the disupersilyldisilanes R*PhSiH-SiClPhR* and R*PhSiH-SiHPhR* which are reduced by Na at 65 degrees C to R*PhSiH2 (and by NaC10H8 at low temperatures to give R*PhSiH-SiHPhR*). The addition of NaR* to R*RSiWCl in THF at low temperatures leads with NaCl elimination to R*2RSiH (R = H, Me) or to R*RHSi-SiHRR* (R = Me) besides R*Cl, or to R*RHSi-SiClRR* (R = Ph) besides R*H and NaR. whereas the addition of R*PhSiHCl to NaR* in TIFF at low temperatures results in the formation of NaSiPhR*(2) besides R*H and NaCl. In the latter cases (R = Ph), NaR* react with R*PhSiHCl to release the silylene R*PhSi, the: transistory existence of which could be proven by trapping it with Et3SiH (formation of R*Ph(Et3Si)-SiH). Subsequently, R*PhSi inserts into the SiH bond of R*PhSiHCl (addition of NaR* to R*PhSiHCl) or into the NaSi bond of NaR* (addition of R*PhSiHCl to NaR*). - Surpersilyldihalosilanes R*SiHCl2 are converted by Mg in C6H6 at 65 degrees C into cyclosilanes (R*SiH)(n) (n = 3, 4) and R*PhSiBrCl by Na at low temperatures - via the silylene R*PhSi - into the disilene R*PhSi=SiPhR*. which is reduced by excess Na to an anion radical. - Supersilyldihalosilanes R*SiBr2Cl2 R*SiBr3 and R*SiI3 react with Na, NaC10H8 or NaR* in THF with formation of tetrasupersilyl-tetrahedro-tetrasilane (R*Si)(4) in quantitative yields, whereas the reactions of C*SiCl3 with LiC10H8 in THF at 45 degrees C lead to (R*Si)(4) only in moderate yields. Obviously, the tetrahedrane is formed from R*SiHal(3) via R*SiHal(2)Na and R*NalSi=SiHalR* as reaction intermediates. The results lead to the following conclusions: (i) Silylenes play a role in dehalogenation of "sterically overloaded" supersilylhalosilanes R*R3-n-SiPHal(n). - (ii) A straight-forward procedure for a high-yield synthesis of (R*Si)(4) from easily available educts consists in supersilanidation of SiH2Cl2 with NaR*, bromination of the formed supersilylsilane R*SiH2Cl with Br-2 and dehalogenation of the bromination product R*SiBr2Cl with Na. [References: 25]