Synthesis and Catalytic Activity of Group 4 Metallocene Containing Silsesquioxanes Bearing Functionalized Silyl Groups

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• 作者：Kenji Wada ; Naohiko Itayama ; Naoki Watanabe ; Masaki Bundo ; Teruyuki Kondo ; and Take-aki Mitsudo
• 刊名：Organometallics
• 出版年：2004
• 出版时间：November 22, 2004
• 年：2004
• 卷：23
• 期：24
• 页码：5824 - 5832
• 全文大小：224K
• 年卷期：v.23,no.24(November 22, 2004)
• ISSN：1520-6041

文摘

A series of metallocene-containing silsesquioxanes with alkenylsilyl and trimethylsilylgroups, Cp'₂M[(c-C₅H₉)₇Si₇O₁₁](OSiMe₂R) (2b-d, 3b-d, 4d, 5d: Cp' = Cp (cyclopentadienyl),Cp* (pentamethylcyclopentadienyl); M = Ti, Zr, Hf, R = methyl, vinyl, allyl), have beensynthesized. The structures of the complexes Cp₂M[(c-C₅H₉)₇Si₇O₁₁](OSiMe₂CH₂CH=CH₂)(M = Zr (3d), Hf (5d)) have been unambiguously established by single-crystal X-raydiffraction analyses. Silylation or germylation of the zirconocene-containing silsesquioxanemonosilanol Cp₂Zr[(c-C₅H₉)₇Si₇O₁₁](OH) (3a) or its hafnocene derivative Cp₂Hf[(c-C₅H₉)₇Si₇O₁₁](OH) (5a), which can be prepared by the careful reaction of the silsesquioxane trisilanol(c-C₅H₉)₇Si₇O₉(OH)₃ (1a) with zirconocene dichloride or hafnocene dichloride, yields the newseries of metallocene-containing silsesquioxanes Cp₂Zr[(c-C₅H₉)₇Si₇O₁₁](OSiMe₂H) (3e), Cp₂Zr[(c-C₅H₉)₇Si₇O₁₁](OGeMe₃) (3f), and Cp₂Hf[(c-C₅H₉)₇Si₇O₁₁](OSiMe₂H) (5e). The reactionof 3e with 2 equiv of hydrogen chloride results in the formation of the dimethylsilyl-containingsilsesquioxane disilanol (c-C₅H₉)₇Si₇O₉(OH)₂(OSiMe₂H) (1e), indicating the applicability ofmetallocene moieties as protecting groups of two adjacent silanol groups. Silsesquioxanesbearing alkenylsilyl groups can be easily converted to derivatives with ethoxysilyl groups,Cp₂M[(c-C₅H₉)₇Si₇O₁₁][OSiMe₂(CH₂)₃SiMe₂(OEt)] (M = Ti (2g), Zr (3g)), by the hydrosilylativereaction. The preliminary examination of the catalytic activity of these metallocene-containingsilsesquioxanes toward the epoxidation of cyclohexene by tert-butyl hydroperoxide revealedthat titanocene-containing silsesquioxanes (2b-d) show modest catalytic activity. Thepresence of alkenylsilyl groups has been found to accelerate the reactions, especially in thecase of titanium-bridged silsesquioxanes.