Catalyst Speciation during ansa-Zirconocene-Catalyzed Polymerization of 1-Hexene Studied by UV-vis Spectroscopy-Formation and Partial Re-Activation of Zr-Allyl Intermediates Full article
| Journal |
Polymers
, E-ISSN: 2073-4360 |
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| Output data | Year: 2019, Volume: 11, Number: 6, Article number : 936, Pages count : 20 DOI: 10.3390/polym11060936 | ||||||||
| Tags | Catalyst speciation; De-activation; Polymerization catalysis; Re-activation; UV-vis spectroscopy; Zirconocene-allyl cations | ||||||||
| Authors |
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| Affiliations |
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Funding (2)
| 1 | Federal Agency for Scientific Organizations | 0303-2016-0009 |
| 2 | German Research Foundation | Br 510/15-1 |
Abstract:
Catalyst speciation during polymerization of 1-hexene in benzene or toluene solutions of the catalyst precursor SBIZr(μ-Me)2AlMe2+ B(C6F5)4- (SBI = rac-dimethylsilyl-bis(1-indenyl)) at 23 °C is studied by following the accompanying UV-vis-spectral changes. These indicate that the onset of polymerization catalysis is associated with the concurrent formation of two distinct zirconocene species. One of these is proposed to consist of SBIZr-σ-polyhexenyl cations arising from SBIZr-Me+ (formed from SBIZr(μ-Me)2AlMe2+ by release of AlMe3) by repeated olefin insertions, while the other one is proposed to consist of SBIZr-η3-allyl cations of composition SBIZr-η3-(1-R-C3H4)+ (R = n-propyl), formed by σ-bond metathesis between SBIZr-Me+ and 1-hexene under release of methane. At later reaction stages, all zirconocene-σ-polymeryl cations appear to decay to yet another SBIZr-allyl species, i.e., to cations of the type SBIZr- η3-(x-R-(3-x)-pol-C3H3)+ (pol = i-polyhexenyl, x = 1 or 2). Renewed addition of excess 1-hexene is proposed to convert these sterically encumbered Zr-allyl cations back to catalytically active SBIZr-σ-polymeryl cations within a few seconds, presumably by initial 1-hexene insertion into the η1- isomer, followed by repeated additional insertions, while the initially formed, less crowded allyl cations, SBIZr-η3-(1-R-C3H4)+ appear to remain unchanged. Implications of these results with regard to the kinetics of zirconocene-catalyzed olefin polymerization are discussed. © 2019 by the authors.
Cite:
Panchenko V.N.
, Babushkin D.E.
, Bercaw J.E.
, Brintzinger H.H.
Catalyst Speciation during ansa-Zirconocene-Catalyzed Polymerization of 1-Hexene Studied by UV-vis Spectroscopy-Formation and Partial Re-Activation of Zr-Allyl Intermediates
Polymers. 2019.
V.11. N6. 936
:1-20. DOI: 10.3390/polym11060936
WOS
Scopus
РИНЦ
ANCAN
PMID
OpenAlex
Catalyst Speciation during ansa-Zirconocene-Catalyzed Polymerization of 1-Hexene Studied by UV-vis Spectroscopy-Formation and Partial Re-Activation of Zr-Allyl Intermediates
Polymers. 2019.
V.11. N6. 936
:1-20. DOI: 10.3390/polym11060936
WOS
Scopus
РИНЦ
ANCAN
PMID
OpenAlex
Files:
Full text from publisher
Dates:
| Submitted: | Apr 26, 2019 |
| Accepted: | May 24, 2019 |
| Published online: | May 29, 2019 |
| Published print: | Jun 1, 2019 |
Identifiers:
| Web of science: | WOS:000473819100008 |
| Scopus: | 2-s2.0-85067336842 |
| Elibrary: | 41641868 |
| Chemical Abstracts: | 2019:1232441 |
| Chemical Abstracts (print): | 174:440073 |
| PMID: | 31146475 |
| OpenAlex: | W2946910387 |