Zur Erzeugung von Silaethenen des Typus R2Si=CH(SiR3 ) und R2Si=CH2 durch thermische Salzeliminierung sowie zur Kenntnis von R2Si=CH(SitBu3) (R = Me, tBu ) / On the Generation of Silaethenes of the Types R2Si=CH(SiR3) and R2Si=CH2 by Thermal Salt Elimination and on the Knowledge of R2Si=CH(SitBu3) (R = Me, tBu)

Abstract

The generation of silaethenes Me2Si=CH(SiMe3) (1), Me2Si=CH(SitBu3) (2), tBuMeSi=CH(SitBu3) (3), and tBu2Si=CH2 (4) from metal organyls >SiX-CM< (X = Br, F; M = Na, Li) by elimination of MX is investigated. The metal organyls are prepared from >SiX-CBr< and RM (R = tBu3Si, nBu, Ph) by Br/M exchange (for preparation of >SiX-CBr< cf. Scheme 1). Only the sterically overcrowded silaethenes 2 and 3. generated from Me2SiF-CHNa(SitBu3) and tBuMeSiF-CHNa(SitBu3), have been identified by trapping with isobutene and dimethylbutadiene under formation of ene and Diels-Alder adducts. Analogous products are not found from Me2SiBr-CHNa(SiMe3) and tBu2-SiBr-CH2-Li. In the absence of trapping agents, compounds 1, 2, and 3 form cyclodimers. A reaction intermediate of the formation of 1 × 1 has been isolated and the structures of 2 × 2 and 3 × 3 have been solved by X-ray analysis. No dimer is observed for 4. In this case compounds are formed which may be interpreted as insertion products of 4 into the CLi bond of the precursor.