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New bis(amidate) Titanium-bis(amido) complexes as hydroamination precatalysts : synthetic and mechanistic investigations Li, Chunyu
Abstract
This thesis focuses on the exploration of a new titanium complex for the hydroamination of alkynes/alkenes. A new pentafluoro amide proligand, [HNC4H9CO( CeF5)] 5, and two related bis(amidate)titanium-bis(amido) complexes (8 and 9) were designed, prepared and fully characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analysis and X-ray crystallography. Both intramolecular and intermolecular hydroamination of alkynes were investigated using the bis(amidate)titanium-bis(amido) complexes as catalysts. Preliminary results were obtained from NMR tube scale reaction monitored by ' H NMR spectroscopy using an internal standard. Larger scale intermolecular hydroamination reactions followed by LAH/THF reduction were carried out to give corresponding isolated amines in yields comparable to that of the NMR tube scale reaction. Hydroamination of.alkenes using these precatalysts was unsuccessful. Compared with other reported titanium complexes, our precatalysts demonstrated better or comparable hydroamination reactivity. Based on literature reports, a mechanism was proposed for the bis(amidate)titanium complex-catalyzed hydroamination which was further verified by preparation of catalytically active intermediates. Stoichiometric reactions of precatalysts with bulky primary amines indicated formation of a titanium imido complex, the active species for hydroamination. Titanium imido complexes or pyridine-trapped imido complexes were isolated and characterized by multinuclear NMR spectroscopy and mass spectrometry. In one case a pyridine-trapped imido complex shows higher reactivity than the corresponding bis(amidate) precatalyst. However, the stoichiometric reaction between precatalysts and less bulky amines form titanium imido dimers, explaining This thesis focuses on the exploration of a new titanium complex for the hydroamination of alkynes/alkenes. A new pentafluoro amide proligand, [HNC4H9CO( CeF5)] 5, and two related bis(amidate)titanium-bis(amido) complexes (8 and 9) were designed, prepared and fully characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analysis and X-ray crystallography. Both intramolecular and intermolecular hydroamination of alkynes were investigated using the bis(amidate)titanium-bis(amido) complexes as catalysts. Preliminary results were obtained from NMR tube scale reaction monitored by ' H NMR spectroscopy using an internal standard. Larger scale intermolecular hydroamination reactions followed by LAH/THF reduction were carried out to give corresponding isolated amines in yields comparable to that of the NMR tube scale reaction. Hydroamination of.alkenes using these precatalysts was unsuccessful. Compared with other reported titanium complexes, our precatalysts demonstrated better or comparable hydroamination reactivity. Based on literature reports, a mechanism was proposed for the bis(amidate)titanium complex-catalyzed hydroamination which was further verified by preparation of catalytically active intermediates. Stoichiometric reactions of precatalysts with bulky primary amines indicated formation of a titanium imido complex, the active species for hydroamination. Titanium imido complexes or pyridine-trapped imido complexes were isolated and characterized by multinuclear NMR spectroscopy and mass spectrometry. In one case a pyridine-trapped imido complex shows higher reactivity than the corresponding bis(amidate) precatalyst. However, the stoichiometric reaction between precatalysts and less bulky amines form titanium imido dimers, explaining
Item Metadata
Title |
New bis(amidate) Titanium-bis(amido) complexes as hydroamination precatalysts : synthetic and mechanistic investigations
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2003
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Description |
This thesis focuses on the exploration of a new titanium complex for the
hydroamination of alkynes/alkenes. A new pentafluoro amide proligand, [HNC4H9CO(
CeF5)] 5, and two related bis(amidate)titanium-bis(amido) complexes (8 and
9) were designed, prepared and fully characterized by multinuclear NMR
spectroscopy, mass spectrometry, elemental analysis and X-ray crystallography.
Both intramolecular and intermolecular hydroamination of alkynes were
investigated using the bis(amidate)titanium-bis(amido) complexes as catalysts.
Preliminary results were obtained from NMR tube scale reaction monitored by ' H
NMR spectroscopy using an internal standard. Larger scale intermolecular
hydroamination reactions followed by LAH/THF reduction were carried out to give
corresponding isolated amines in yields comparable to that of the NMR tube scale
reaction. Hydroamination of.alkenes using these precatalysts was unsuccessful.
Compared with other reported titanium complexes, our precatalysts demonstrated
better or comparable hydroamination reactivity.
Based on literature reports, a mechanism was proposed for the bis(amidate)titanium
complex-catalyzed hydroamination which was further verified by preparation of
catalytically active intermediates. Stoichiometric reactions of precatalysts with bulky
primary amines indicated formation of a titanium imido complex, the active species
for hydroamination. Titanium imido complexes or pyridine-trapped imido complexes
were isolated and characterized by multinuclear NMR spectroscopy and mass
spectrometry. In one case a pyridine-trapped imido complex shows higher reactivity
than the corresponding bis(amidate) precatalyst. However, the stoichiometric reaction
between precatalysts and less bulky amines form titanium imido dimers, explaining This thesis focuses on the exploration of a new titanium complex for the
hydroamination of alkynes/alkenes. A new pentafluoro amide proligand, [HNC4H9CO(
CeF5)] 5, and two related bis(amidate)titanium-bis(amido) complexes (8 and
9) were designed, prepared and fully characterized by multinuclear NMR
spectroscopy, mass spectrometry, elemental analysis and X-ray crystallography.
Both intramolecular and intermolecular hydroamination of alkynes were
investigated using the bis(amidate)titanium-bis(amido) complexes as catalysts.
Preliminary results were obtained from NMR tube scale reaction monitored by ' H
NMR spectroscopy using an internal standard. Larger scale intermolecular
hydroamination reactions followed by LAH/THF reduction were carried out to give
corresponding isolated amines in yields comparable to that of the NMR tube scale
reaction. Hydroamination of.alkenes using these precatalysts was unsuccessful.
Compared with other reported titanium complexes, our precatalysts demonstrated
better or comparable hydroamination reactivity.
Based on literature reports, a mechanism was proposed for the bis(amidate)titanium
complex-catalyzed hydroamination which was further verified by preparation of
catalytically active intermediates. Stoichiometric reactions of precatalysts with bulky
primary amines indicated formation of a titanium imido complex, the active species
for hydroamination. Titanium imido complexes or pyridine-trapped imido complexes
were isolated and characterized by multinuclear NMR spectroscopy and mass
spectrometry. In one case a pyridine-trapped imido complex shows higher reactivity
than the corresponding bis(amidate) precatalyst. However, the stoichiometric reaction
between precatalysts and less bulky amines form titanium imido dimers, explaining
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Extent |
4113351 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-11-17
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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 |
10.14288/1.0061222
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2004-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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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.