Cyclopentadienyl Titanium Imido Compounds and Their Ethylene Polymerization Capability: Control of Molecular Weight Distributions by Imido N-Substituents
Identifieur interne : 001408 ( Main/Exploration ); précédent : 001407; suivant : 001409Cyclopentadienyl Titanium Imido Compounds and Their Ethylene Polymerization Capability: Control of Molecular Weight Distributions by Imido N-Substituents
Auteurs : Christopher T. Owen [Royaume-Uni] ; Paul D. Bolton [Royaume-Uni] ; Andrew R. Cowley [Royaume-Uni] ; Philip Mountford [Royaume-Uni]Source :
- Organometallics [ 0276-7333 ] ; 2006.
Abstract
Reaction of the previously reported Cp*Ti(NtBu)Cl(py) (1) with bulky ortho-substituted anilines ArNH2 afforded the corresponding aryl imido derivatives Cp*Ti(NAr)Cl(py) (Ar = 2,6-C6H3iPr2 (2), 2,6-C6H3Br2 (3), 2-C6H4tBu (4), and 2-C6H4iPr (5)). Reaction of 2 with B(C6F5)3 in C6D6 or heating in vacuo at 200 °C afforded the imido-bridged dimer Cp*2Ti2(μ-N-2,6-C6H3iPr2)2Cl2 (8). Activation of 1−5 with MAO gave moderately active catalyst systems for the polymerization of ethylene in contrast to the previously reported, highly active titanium imido systems Ti(Me3[9]aneN3)(NR)Cl2/MAO and Ti{HC(Me2pz)3}(NR)Cl2/MAO, which are isolobal and isoelectronic with 1−5. The Cp*-supported precatalyst productivities were sensitive to both the imido N-substituents and initial precatalyst/cocatalyst concentrations. Depending upon the imido N-substituents and initial precatalyst/cocatalyst concentrations, polyethylene with unimodal (either rather low or very high molecular weight) or bimodal molecular weight distributions can be obtained. Excess AlMe3 suppresses catalyst productivity but does not affect the overall molecular weight distribution in the system evaluated (1/MAO). Both chain transfer to aluminum and β-hydrogen transfer appear to be active pathways for formation of the low molecular weight fractions of the polymers formed with 1−5/MAO. Under otherwise identical polymerization conditions the catalyst systems 2/MAO and 8/MAO had comparable productivities and gave polyethylene with very similar molecular weight and molecular weight distributions, suggesting a potential role for binuclear species in the catalyst systems 1−5/MAO.
New cyclopentadienyl titanium imido compounds Cp*Ti(NR)Cl(py) were prepared and their ethylene polymerization capability was determined. The graphic shows the molecular structure of one of the new precatalysts and the GPC analyses of the PEs formed with different N-substituted catalysts.
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DOI: 10.1021/om0608556
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Polymerization Capability: Control of Molecular Weight
Distributions by Imido N-Substituents</title><author><name sortKey="Owen, Christopher T" sort="Owen, Christopher T" uniqKey="Owen C" first="Christopher T." last="Owen">Christopher T. Owen</name><affiliation wicri:level="4"><country xml:lang="fr">Royaume-Uni</country><wicri:regionArea>Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA</wicri:regionArea><orgName type="university">Université d'Oxford</orgName><placeName><settlement type="city">Oxford</settlement><region type="nation">Angleterre</region><region type="région" nuts="1">Oxfordshire</region></placeName></affiliation></author><author><name sortKey="Bolton, Paul D" sort="Bolton, Paul D" uniqKey="Bolton P" first="Paul D." last="Bolton">Paul D. Bolton</name><affiliation wicri:level="4"><country xml:lang="fr">Royaume-Uni</country><wicri:regionArea>Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA</wicri:regionArea><orgName type="university">Université d'Oxford</orgName><placeName><settlement type="city">Oxford</settlement><region type="nation">Angleterre</region><region type="région" nuts="1">Oxfordshire</region></placeName></affiliation></author><author><name sortKey="Cowley, Andrew R" sort="Cowley, Andrew R" uniqKey="Cowley A" first="Andrew R." last="Cowley">Andrew R. Cowley</name><affiliation wicri:level="4"><country xml:lang="fr">Royaume-Uni</country><wicri:regionArea>Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA</wicri:regionArea><orgName type="university">Université d'Oxford</orgName><placeName><settlement type="city">Oxford</settlement><region type="nation">Angleterre</region><region type="région" nuts="1">Oxfordshire</region></placeName></affiliation></author><author><name sortKey="Mountford, Philip" sort="Mountford, Philip" uniqKey="Mountford P" first="Philip" last="Mountford">Philip Mountford</name><affiliation wicri:level="4"><country xml:lang="fr">Royaume-Uni</country><wicri:regionArea>Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA</wicri:regionArea><orgName type="university">Université d'Oxford</orgName><placeName><settlement type="city">Oxford</settlement><region type="nation">Angleterre</region><region type="région" nuts="1">Oxfordshire</region></placeName></affiliation><affiliation wicri:level="1"><country wicri:rule="url">Royaume-Uni</country></affiliation></author></analytic><monogr></monogr><series><title level="j" type="main">Organometallics</title><title level="j" type="abbrev">Organometallics</title><idno type="ISSN">0276-7333</idno><idno type="eISSN">1520-6041</idno><imprint><publisher>American Chemical Society</publisher><date type="e-published" when="2006-11-29">2006</date><date when="2007-01-01">2007</date><biblScope unit="vol">26</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="83">83</biblScope><biblScope unit="page" to="92">92</biblScope></imprint><idno type="ISSN">0276-7333</idno></series></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0276-7333</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract">Reaction of the previously reported Cp*Ti(NtBu)Cl(py) (1) with bulky ortho-substituted anilines ArNH2 afforded the corresponding aryl imido derivatives Cp*Ti(NAr)Cl(py) (Ar = 2,6-C6H3iPr2 (2), 2,6-C6H3Br2 (3), 2-C6H4tBu (4), and 2-C6H4iPr (5)). Reaction of 2 with B(C6F5)3 in C6D6 or heating in vacuo at 200 °C afforded the imido-bridged dimer Cp*2Ti2(μ-N-2,6-C6H3iPr2)2Cl2 (8). Activation of 1−5 with MAO gave moderately active catalyst systems for the polymerization of ethylene in contrast to the previously reported, highly active titanium imido systems Ti(Me3[9]aneN3)(NR)Cl2/MAO and Ti{HC(Me2pz)3}(NR)Cl2/MAO, which are isolobal and isoelectronic with 1−5. The Cp*-supported precatalyst productivities were sensitive to both the imido N-substituents and initial precatalyst/cocatalyst concentrations. Depending upon the imido N-substituents and initial precatalyst/cocatalyst concentrations, polyethylene with unimodal (either rather low or very high molecular weight) or bimodal molecular weight distributions can be obtained. Excess AlMe3 suppresses catalyst productivity but does not affect the overall molecular weight distribution in the system evaluated (1/MAO). Both chain transfer to aluminum and β-hydrogen transfer appear to be active pathways for formation of the low molecular weight fractions of the polymers formed with 1−5/MAO. Under otherwise identical polymerization conditions the catalyst systems 2/MAO and 8/MAO had comparable productivities and gave polyethylene with very similar molecular weight and molecular weight distributions, suggesting a potential role for binuclear species in the catalyst systems 1−5/MAO.</div><div type="abstract">New cyclopentadienyl titanium imido compounds Cp*Ti(NR)Cl(py) were prepared and their ethylene polymerization capability was determined. The graphic shows the molecular structure of one of the new precatalysts and the GPC analyses of the PEs formed with different N-substituted catalysts.</div></front></TEI><affiliations><list><country><li>Royaume-Uni</li></country><region><li>Angleterre</li><li>Oxfordshire</li></region><settlement><li>Oxford</li></settlement><orgName><li>Université d'Oxford</li></orgName></list><tree><country name="Royaume-Uni"><region name="Angleterre"><name sortKey="Owen, Christopher T" sort="Owen, Christopher T" uniqKey="Owen C" first="Christopher T." last="Owen">Christopher T. Owen</name></region><name sortKey="Bolton, Paul D" sort="Bolton, Paul D" uniqKey="Bolton P" first="Paul D." last="Bolton">Paul D. Bolton</name><name sortKey="Cowley, Andrew R" sort="Cowley, Andrew R" uniqKey="Cowley A" first="Andrew R." last="Cowley">Andrew R. Cowley</name><name sortKey="Mountford, Philip" sort="Mountford, Philip" uniqKey="Mountford P" first="Philip" last="Mountford">Philip Mountford</name><name sortKey="Mountford, Philip" sort="Mountford, Philip" uniqKey="Mountford P" first="Philip" last="Mountford">Philip Mountford</name></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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