Infoscience

Journal article

Sterically crowded supersilyl compounds. 113. Silicon compounds 13. Donor-free and donor-containing supersilyl alkali metal tBu3SiM: Synthesis, characterization, structure

Supersilyl alk. metals (alkali supersilanides) tBu3SiM without or with donors (Do) like ethers, amines, arom. hydrocarbons are easily obtained by the action of alk. metals M on supersilyl halides tBu3SiX above room temp. in alkanes or donor-solvents like THF, benzene: tBu3SiX + 2M -> tBu3SiM + MX; tBu3SiM + nDo -> tBu3SiM(Do). Ethers as donors can be exchanged by stronger donors like PMDTA, 18-crown-6, cryptand-222. In particular the following extremely water and air sensitive compds. are prepd.: yellow tBu3SiLi (as to x-ray structure anal. dimeric with Si...Li...Si contacts), orange yellow tBu3SiNa (as to x-ray structure anal. dimeric with Si...Na...Si contacts), light-yellow tBu3SiK (as to its insoly. in alkanes polymeric), tBu3SiM (M = Rb, Cs; insol. in alkanes), light-yellow to colorless tBu3SiLi(THF)2 (probably monomeric), light-yellow tBu3SiNa(THF)2 (as to x-ray structure anal. dimeric with CH3...Na contacts), light-yellow tBu3SiNa(OBu2)2 (probably analogously structured as the THF adduct), yellow tBu3SiK(THF)n (loses THF; stable only in THF), light-yellow tBu3SiNa(PMDTA) (as to x-ray structure anal. monomeric), orange-red tBu3SiK(Benzene)3 (as to x-ray structure anal. monomeric), orange-yellow tBu3SiNa(18-C-6) (unstable as to its tendency to deprotonate 18-crown-6), tBu3SiM(C222) (M = Na, K; not isolable as to its tendency to deprotonate cryptand-222). Because of the high tendency of the anionic part tBu3Si- of the compds. mentioned for delivering electrons, the supersilyl alk. metals act as strong bases which deprotonate even weak bases such as THF or benzene under formation of supersilane tBu3SiH. Over and above that, they work as good nucleophiles and reducing agents which for example react with Me3SiX under formation of trimethylsilylsupersilane Me3Si-SitBu3 and with Ag+NO3- under formation of superdisilane tBu3Si-SitBu3. As the supersilyl alk. metals may even be oxidized by supersilyl halides in alkanes at 100 Deg by way of tBu3SiM + tBu3SiX -> tBu3Si. + MX + tBu3Si., and tBu3Si. + RH -> tBu3SiH + R., and 2tBu3Si..dblarw.(tBu3Si)2, the formation of tBu3SiM from tBu3SiI and K, Rb, Cs at elevated temps. in satd. hydrocarbons is accompanied by the formation of supersilane, superdisilane and secondary products of R.. [on SciFinder (R)]

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