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Facile and selective aliphatic c-h bond activation at ambient temperatures initiated by Cp*W(NO)(CH2CMe3)(eta(3)-CH2CHCHMe)

TitleFacile and selective aliphatic c-h bond activation at ambient temperatures initiated by Cp*W(NO)(CH2CMe3)(eta(3)-CH2CHCHMe)
Publication TypeJournal Article
Year of Publication2008
AuthorsTsang, JYK, Buschhaus, MSA, Graham, PM, Semiao, CJ, Semproni, SP, Kim, SJ, Legzdins, P
JournalJournal of the American Chemical Society
Volume130
Pagination3652-3663
Date PublishedMar
ISBN Number0002-7863
Abstract

Thermolysis of Cp*W(NO)(CH2CMe3)(eta(3)-CH2CHCHMe) (1) at ambient temperatures leads to the loss of neopentane and the formation of the eta(2)-diene intermediate, Cp*W(NO)(eta(2)-CH2C=CHCH=CH2) (A), which has been isolated as its 18e PMe3 adduct. In the presence of linear alkanes, A effects C-H activations of the hydrocarbons exclusively at their terminal carbons and forms 18e Cp*W(NO)(n-alkyl)-(eta(3)-CH2CHCHMe) complexes. Similarly, treatments of 1 with methylcyclohexane, chloropentane, diethyl ether, and triethylamine all lead to the corresponding terminal C-H activation products. Furthermore, a judicious choice of solvents permits the C-H activation of gaseous hydrocarbons (i.e., propane, ethane, and methane) at ambient temperatures under moderately elevated pressures. However, reactions between intermediate A and cyclohexene, acetone, 3-pentanone, and 2-butyne lead to coupling between the eta(2)-diene ligand and the site of unsaturation on the organic molecule. For example, Cp*W(NO)(eta(3),eta(1)-CH2-CHCHCH2C(CH2CH3)(2)O) is formed exclusively in 3-pentanone. When the site of unsaturation is sufficiently sterically hindered, as in the case of 2,3-dimethyl-2-butene, C-H activation again becomes dominant, and so the C-H activation product, Cp*W(NO)(eta(1)-CH2CMe=CMe2)(eta(3)-CH2CHCHMe), is formed exclusively from the alkene and 1. 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 X-ray crystallographic analyses. Finally, the newly formed alkyl ligands may be liberated from the tungsten centers in the product complexes by treatment with iodine. Thus, exposure of a CDCl3 solution of the n-pentyl allyl complex, Cp*W(NO)(n-C5H11)(eta(3)-CH2CHCHMe), to l(2) at -60 degrees C produces n-C(5)H(11)l in moderate yields.

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