Silicon-Carbon bond cleavage reactions of Ansa tungstenocene compounds: The [Me₂Si] bridge as a site for metallocene functionalization

• Published in: Proceedings of the National Academy of Sciences - PNAS 2008-08, Vol.105 (32), p.11060-11065
• Main Authors: Zachmanoglou, Cary E, Lee, Hyosun, Jang, Seung Ho, Pang, Keliang, Parkin, Gerard
• Format: Article
• Language: English
• Subjects: Ansae; Atoms; Carbon; Carbon - chemistry; Chemical bonding; Chemical bonds; Chemical compounds; Chemical reactions; Hydrides; Isomers; Ligands; Metals - chemistry; Molecular structure; Pentanes; Physical Sciences; Silicon; Silicon - chemistry; Silicon Compounds - chemical synthesis; Silicon Compounds - chemistry; X ray diffraction
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0803089105

[Me₂Si(CpMe²)₂]W(H)Cl is obtained via reaction of WCl₆ with a mixture of [Me₂Si(CpMe²)₂]Li₂ and NaBH₄, from which the dichloride [Me₂Si(CpMe²)₂]WCl₂ is obtained via treatment with CHCl₃. [Me₂Si(CpMe²)₂]WCl₂ provides a means to access other ansa tungstenocene compounds, such as [Me₂Si(CpMe²)₂]WH₂, [Me₂Si(CpMe²)₂]WMe₂, and [Me₂Si(CpMe²)₂]WCO. Of most interest, the reactions of [Me₂Si(CpMe²)₂]W(H)Cl with organolithium reagents do not yield simple ansa tungstenocene derivatives. Specifically, the reactions of [Me₂Si(CpMe²)₂]W(H)Cl with MeLi, BunLi, or PhLi result in the formation of mixed-ring tungstenocene compounds resulting from C-Si cleavage and functionalization of the ansa bridge, namely (CpMe²)(η⁵,κ¹-C₅H₂Me₂SiMe₂CH₂)WH, (CpMe²)[η⁵,κ¹-C₅H₂Me₂Si(Me)(Bun)CH₂]WH, and (CpMe²)[η⁵,κ¹-C₅H₂Me₂SiMe₂(C₆H₄)]WH, respectively. In contrast to the C-Si cleavage achieved by MeLi, BunLi, and PhLi, the ansa bridge of [Me₂Si(CpMe²)₂]W(H)Cl is inert to ButLi and the product obtained is the fulvene ("tuck-in") complex [Me₂Si(CpMe²)(η⁶-C₅MeH₂CH₂)]WH derived from dehydrohalogenation.