A NEW METHOD FOR THE SYNTHESIS OF BRANCHED POLYSILANE ANIONS

Citation
Y. Apeloig et al., A NEW METHOD FOR THE SYNTHESIS OF BRANCHED POLYSILANE ANIONS, Organometallics, 16(6), 1997, pp. 1265-1269
Citations number
25
Categorie Soggetti
Chemistry Inorganic & Nuclear","Chemistry Inorganic & Nuclear
Journal title
ISSN journal
02767333
Volume
16
Issue
6
Year of publication
1997
Pages
1265 - 1269
Database
ISI
SICI code
0276-7333(1997)16:6<1265:ANMFTS>2.0.ZU;2-6
Abstract
Lithiation by MeLi of three families of branched polysilanes (Me(3)Si) (3)Si-X {(1) X = SiMe(2)H, t-BuMe(2)Si, SiMe(2)SiMe(3), t-BuSiMe(2)SiM e(2); (2) X = SiMe(SiMe(3))(2), Si(SiMe(3))(3), SiMe(2)Si(SiMe(3))(3), SiMeHSi(SiMe(3))(3); (3) X = Si(SiMe(3))(2)Cl, Si[Si(SiMe(3))(3)]MeCl , Si[Si(SiMe(3))(3)]HCl} yields, depending on X, one of the following: (a) novel branched polysilyllithium compounds; (b) the known (Me(3)Si )(3)SiLi; (c) various mixtures. The cleavage of family 1 can be unders tood in terms of steric effects, i.e., assuming that MeLi attacks pref erentially the sterically less hindered Si atom leading to the formati on of new polysilyllithium compounds, e.g., t-BuMe(2)Si(Me(3)Si)(2)SiL i . 3THF and t-BuMe(2)SiSiMe(2)(Me(3)Si)(2)SiLi . 3THF, which were iso lated in a crystalline form. The X-ray structure of the former is pres ented. In contrast to 1 the lithiation of the branched polysilanes 2 l eads exclusively (mostly with (Me(3)Si)(3)SiSiMe(SiMe(3))(2)) to the k nown (Me(3)Si)(3)SiLi. Lithiation of 3 leads to a number of novel poly silyllithium compounds. We tentatively propose that the lithiation of 3 proceeds by a two step reaction in which a disilene is formed as an intermediate, and this is followed by fast addition of a second molecu le of MeLi to produce the final silyllithium product.