Competitive ArC-H and ArC-X (X = Cl, Br) activation in halobenzenes at cationic titanium centers

Journal of the American Chemical Society
Kuangbiao MaMasood Parvez

Abstract

The titanium methyl cation [Cp*((tBu3P=N)TiCH3]+ [B(C6F5)4]- reacts rapidly with H2 to give the analogous cationic hydride [Cp*((tBu3P=N)TiH(THF)n]+ [B(C6F5)4]- (n = 0, 1), which can be trapped and isolated as its THF adduct 1 x THF (n = 1). When generated in the presence of chloro or bromobenzene, 1 undergoes C-X activation or ortho-C-H activation, depending on the amount of dihydrogen present in the reaction medium. At approximately 4 atm of H2, C-X activation is preferred, giving the halocations [Cp*((tBu3P= N)TiX]+ [B(C6F5)4]- (2X) and C6H6/biphenyl mixtures. At lower pressures of H2 (>1 atm), the beta-halophenyl cations [Cp*((tBu3P=N)Ti(2-X-C6H4)]+ [B(C6F5)4]- (3X) are the products isolated. In the absence of H2, these compounds are quite thermally stable, but undergo beta-halogen elimination upon moderate heating, to give 2X (approximately 20%) and compounds 4X which are the result of reaction between 2X and benzyne via addition of the benzyne C-C triple bond across the Ti-N bond of the phosphinimide ligand. Thus, three separate bond activation processes are operative in this system: direct C-X activation, ortho-C-H activation, and indirect C-X activation via beta-halogen elimination. Mechanistic studies on all three proc...Continue Reading

References

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Jul 18, 2002·Journal of the American Chemical Society·Bradley M Kraft, William D Jones
Jan 16, 2003·Journal of the American Chemical Society·Robert A StocklandRichard F Jordan
May 6, 2004·Journal of the American Chemical Society·Kuangbiao MaMasood Parvez
Nov 26, 2004·Journal of the American Chemical Society·Fan WuRichard F Jordan
Jan 6, 2005·Journal of the American Chemical Society·Laurent MaronRichard A Andersen
May 12, 2005·Journal of the American Chemical Society·Fabiola Barrios-Landeros, John F Hartwig
Oct 13, 2005·Journal of the American Chemical Society·Marco W BouwkampBart Hessen
Dec 1, 2005·Journal of the American Chemical Society·Lei FanOleg V Ozerov

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Citations

May 7, 2011·Chemical Reviews·Mar Gómez-Gallego, Miguel A Sierra
Feb 24, 2015·Dalton Transactions : an International Journal of Inorganic Chemistry·Thomas P RobinsonAndrew L Johnson
Mar 18, 2009·Dalton Transactions : an International Journal of Inorganic Chemistry·Ignacio FernándezFernando López Ortiz
Feb 20, 2008·Dalton Transactions : an International Journal of Inorganic Chemistry·Raquel BielsaEsteban P Urriolabeitia
Feb 14, 2020·Dalton Transactions : an International Journal of Inorganic Chemistry·David DunlopMartin Lamač
Jan 14, 2010·Chemical Reviews·David BalcellsOdile Eisenstein
Jan 9, 2009·Journal of the American Chemical Society·Kozo FukumotoHiroshi Nakazawa

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