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UBC Theses and Dissertations
C-H bond activation of hydrocarbons by a tungsten allene complex Stephen H. K., Ng
Abstract
Gentle thermolysis of the 18e alkyl-allyl complex, Cp*W(NO)(CH₂CMe₃)(η³-1,1-Me₂C₃H₃) (1.1), generates a reactive 16e allene intermediate, Cp*W(NO)(η²-H₂C=C=CMe₂) (A), by a first-order process with concomitant evolution of neopentane via hydrogen abstraction from the dimethylallyl ligand. Intermediate A has been structurally characterized as its PMe₃ adduct, and is capable of effecting both single and multiple intermolecular C-H bond activations of hydrocarbon solvents to form alkyl-allyl and allyl-hydrido complexes. The products of reactions of A with methyl-substituted arenes (i.e. sp² C-H vs sp³ C-H) indicate an inherent preference for the activation of stronger arene C-H bonds, however steric effects are also relevant as indicated by the exclusive formation of benzylic C-H activation products in mesitylene. Thermolyses of 1.1 in alkane solvents generate products resulting from three successive C-H bond-activation reactions. Preliminary studies suggest that allyl-hydrido complexes are formed along with an organic product; for example, in cyclohexane, 1,1- dimethylpropylcyclohexane results from coupling of a solvent molecule and a fragment derived from the precursor dimethylallyl ligand. The allyl-hydrido complexes have potential synthetic utility, since studies conducted on structurally and electronically related CpMo complexes show that they may be capable of ultimately producing homoallylic alcohols.
Item Metadata
Title |
C-H bond activation of hydrocarbons by a tungsten allene complex
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2002
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Description |
Gentle thermolysis of the 18e alkyl-allyl complex, Cp*W(NO)(CH₂CMe₃)(η³-1,1-Me₂C₃H₃) (1.1), generates a reactive 16e allene intermediate, Cp*W(NO)(η²-H₂C=C=CMe₂) (A), by a first-order process with concomitant evolution of neopentane via hydrogen abstraction from the dimethylallyl ligand. Intermediate A has been structurally characterized as its PMe₃ adduct, and is capable of effecting both single and multiple intermolecular C-H bond activations of hydrocarbon solvents to form alkyl-allyl and allyl-hydrido complexes. The products of reactions of A with methyl-substituted arenes (i.e. sp² C-H vs sp³ C-H) indicate an inherent preference for the activation of stronger arene C-H bonds, however steric effects are also relevant as indicated by the exclusive formation of benzylic C-H activation products in mesitylene. Thermolyses of 1.1 in alkane solvents generate products resulting from three successive C-H bond-activation reactions. Preliminary studies suggest that allyl-hydrido complexes are formed along with an organic product; for example, in cyclohexane, 1,1- dimethylpropylcyclohexane results from coupling of a solvent molecule and a fragment derived from the precursor dimethylallyl ligand. The allyl-hydrido complexes have potential synthetic utility, since studies conducted on structurally and electronically related CpMo complexes show that they may be capable of ultimately producing homoallylic alcohols.
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Extent |
4974132 bytes
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Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-09-30
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0061252
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2002-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.