Octahedral bis(phenolate) ether group IV metal complexes for polymerization and copolymerization of alpha-olefins
Abstract/Contents
- Abstract
- Octahedral group IV bis(phenolate) ether complexes, activated by methylaluminoxane, are highly active and stereospecific [alpha]-olefin polymerization catalysts. X-ray crystallographic analysis reveals the Zr and Hf complexes to be closely isostructural; the bond lengths of the Hf complex are slightly shorter, but the maximum deviation is only 0.062 Å. Despite the structural similarity of the Hf and Zr complexes, the Hf complexes generate more highly stereoselective catalysts. In addition to the influence of the transition metal, the structure of the ligand has a large influence on the stereospecificity. Bis-t-Butyl phenyl substituted complexes of Hf and Zr, when activated by MAO at 50 - 80 °C, generate high molecular weight polypropylene (Mn = 130,000 - 360,000 g/mol) with isotacticities [mmmm] > 0.97 and melting points as high as 165°C. Octahedral group IV bisphenolate ether complexes, activated by methylaluminoxane, were also tested in propylene polymerization in the presence diethyl zinc. Although the Hf and Zr complexes are structurally similar, propylene polymerization behavior of the two catalysts differs significantly in terms of productivity, isospecificity and propensity to incorporate specific regioerrors. 13C-NMR analysis revealed that the type and the number of regioerrors being incorporated into the polymer chain are strongly dependent on the identity of the ligand and the metal. Low molecular weight polypropylene oligomers (Mn = 1700 - 9900 g/mol), generated in the presence of diethyl zinc facilitated end group analysis, which revealed the presence of isobutyl and 2-methylbutyl groups. Octahedral bis(phenolate) catalysts are highly active catalysts for the isospecific polymerization of 1-hexene and the production of high molecular weight ethylene/1-hexene copolymers. These catalysts are active for the production of high molecular weight copolymers even at high temperatures. The reactivity ratios for these complexes were determined; all of the bis(phenolate) complexes tested showed reasonable 1-hexene incorporations. The complexes prepared from the more sterically demanding ligands showed higher incorporations of comonomers than those prepared from the less sterically demanding ligands. Complexes of the type Cp*TiX2(ONR'R'') (Cp* = [Eta]5-C5Me5, X = Me, Cl; R = Et, TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl); X = R' = Me, R'' = tBu) were synthesized by several routes. Upon activation with [Ph3C]+[B(C6F5)4]- and AliBu3, these complexes generate highly active catalysts for propylene polymerization, although significant catalyst deactivation was observed. Activation with B(C6F5)3/AliBu3 or methylaluminoxane (MAO) resulted in reduced polymerization activity; the latter leading to increased catalyst lifetime. Reaction of Cp*Ti(Me)2(ONEt2) and Cp*Ti(Me)2(ONtBu(Me)) with B(C6F5)3 resulted in clean formation of the zwitterionic contact ion pairs, [Cp*Ti(Me)([Eta]2-ONEt2)]+[MeB(C6F5)3]- and [Cp*Ti(Me)([Eta]2-ONtBu(Me))]+[MeB(C6F5)3]- respectively whereas reaction of Cp*Ti(Me)2([Eta]2-ONtBu(Me)) with [Ph3C]+[B(C6F5)4]- resulted in the clean formation of the solvent-separated ion pair [Cp*Ti(Me)([Eta]2-ONtBu(Me))]+[B(C6F5)4]-. Addition of AliBu3 or AlMe3 to the cationic [Cp*Ti(Me)(ONtBu(Me))]+[B(C6F5)4]- resulted in decomposition of the cations.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Copyright date | 2011 |
| Publication date | 2010, c2011; 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Kiesewetter, Elizabeth Tanzini |
|---|---|
| Associated with | Stanford University, Department of Chemistry |
| Primary advisor | Waymouth, Robert M |
| Thesis advisor | Waymouth, Robert M |
| Thesis advisor | Stack, T. (T. Daniel P.), 1959- |
| Thesis advisor | Wender, Paul A |
| Advisor | Stack, T. (T. Daniel P.), 1959- |
| Advisor | Wender, Paul A |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Elizabeth Tanzini Kiesewetter. |
|---|---|
| Note | Submitted to the Department of Chemistry. |
| Thesis | Ph.D. Stanford University 2011 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Elizabeth Tanzini Kiesewetter
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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