Synthesis, structure and reactivity of sterically demanding oligosilanylmagnesium compounds

A sterically demanding TBS-substituted oligosilane was stepwisely formed by reactions of oligosilanyl potassium compound and the corresponding chlorosilane. However, the similar reaction using SiX4 (X = Cl, Br) could not afford the ring closure product. The silyl anion was then transformed to silyl Grignard compound 5, which can be used to react with SiX4 to give the dihalocyclopentasilanes (6, X = Cl 7, X = Br) successfully. The molecular structures of 3-7 have been confirmed by X-ray single-crystal analyses.52