Intermolecular C鈥揌 Activations of Hydrocarbons Initiated by a Tungsten Trimethylsilylallyl Complex

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• 作者：Catherine Chow ; Brian O. Patrick ; Peter Legzdins
• 刊名：Organometallics
• 出版年：2012
• 出版时间：November 12, 2012
• 年：2012
• 卷：31
• 期：21
• 页码：7453-7466
• 全文大小：731K
• 年卷期：v.31,no.21(November 12, 2012)
• ISSN：1520-6041

文摘

Thermolysis of Cp*W(NO)(Npt)(畏³-CH₂CHCHSiMe₃) [Cp* = 畏⁵-C₅Me₅; Npt = CH₂CMe₃] at 55 掳C leads to the loss of neopentane and the formation of the 16-electron 畏²-allene intermediate Cp*W(NO)(畏²-CH₂鈺怌鈺怌HSiMe₃), which activates hydrocarbons at their methyl groups. In the case of linear alkanes, only terminal C鈥揌 activation occurs. This selectivity persists in the presence of an ether functionality, but not with other oxygen-containing substrates such as aldehydes and alcohols. With these latter substrates, the organometallic complex is oxidized to Cp*W(O)₂(Npt). The existence of the allene intermediate has been confirmed by its reaction with PMe₃ to form the 18-electron adduct and by its diagnostic reaction with cyclohexene. Carbonylation of Cp*W(NO)(Npt)(畏³-CH₂CHCHSiMe₃) with CO (550 psig) at room temperature results in the clean formation of the corresponding Cp*W(NO)(畏¹-C(鈺怬)Npt)(畏³-CH₂CHCHSiMe₃) complex, which exists as a mixture of two interconverting isomers differing in their modes of attachment of the (畏³-CH₂CHCHSiMe₃) ligands to the tungsten centers. The congeneric molybdenum complex, Cp*Mo(NO)(Npt)(畏³-CH₂CHCHSiMe₃), has also been synthesized, and although it generates the requisite 畏²-allene intermediate upon thermolysis, its preferred mode of reactivity is coupling of the allyl and alkyl ligands. Consequently, the molybdenum complex is inferior to the tungsten system for effecting C鈥揌 activations. All new complexes have been characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of most of them have been established by single-crystal X-ray crystallographic analyses.