Dodecaallylhexasilacyclohexane 4, which would be a stable precursor for a variety of hexasilacyclohexane derivatives, was synthesized by the reaction of [pedeta·SiH 2 Cl] 2 [Si 6 Cl 12 ·2Cl] (1) with allylmagnesium bromide. In addition, an effective synthetic route of dodecachlorohexasilacyclohexane 3 from trichlorosilane was found. De-* Prof. Dr. Y. Mizuhata