Thermal Chemistry of a Tungsten Trimethylsilylallyl Complex in Benzene and Fluorobenzenes

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• 作者：Catherine Chow ; Brian O. Patrick ; Peter Legzdins
• 刊名：Organometallics
• 出版年：2012
• 出版时间：December 10, 2012
• 年：2012
• 卷：31
• 期：23
• 页码：8159-8171
• 全文大小：603K
• 年卷期：v.31,no.23(December 10, 2012)
• ISSN：1520-6041

文摘

The thermolysis of Cp*W(NO)(Npt)(畏³-CH₂CHCHSiMe₃) (1; Cp* = 畏⁵-C₅Me₅; Npt = CH₂CMe₃) in benzene at 55 掳C generates three isomeric products having the composition Cp*W(NO)(H)(畏³-Me₃SiCHCHCHPh) (2). These are isomers of the expected Cp*W(NO)(Ph)(畏³-Me₃SiCHCHCH₂) compound and result from an intramolecular Ph/allyl H exchange. Thermolysis of 2 in the presence of pyridine produces the 畏²-olefin pyridine adduct Cp*W(NO)(畏²-Me₃SiCH₂CH鈺怌HPh)(C₅H₅N) (3). However, when the same reaction is carried out in deuterobenzene with 10 equiv of pyridine, NMR spectroscopic data suggest that the meso hydrogen of the allyl ligand is exchanged for a deuterium atom before pyridine trapping occurs. The activation of fluorobenzenes (i.e., pentafluorobenzene, p-difluorobenzene, and o-difluorobenzene) by Cp*W(NO)(Npt)(畏³-CH₂CHCHSiMe₃) has also been studied, and for these substrates, C鈥揌 bond activation occurs exclusively. Selectivity for the activation of these C鈥揌 bonds appears to be determined by sterics. Intramolecular migration of the newly formed fluoroaryl ligands onto the allyl ligands does not occur when there is a fluorine atom in the position ortho to the newly formed W鈥揅 bond. This behavior is probably a manifestation of the fact that metal鈥?i>o-fluoroaryl bonds tend to be stronger than metal鈥揳ryl linkages. 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.