Polymerization of cyclopentene using metallocene catalysts: Competitive cis- and trans-1,3 insertion mechanisms

Macromolecules

Volumn 30, Issue 11, 1997, Pages 3151-3158

  Kelly, W Mark ^a   Wang, Shaotian ^a   Collins, Scott ^a  

^a UNIVERSITY OF WATERLOO   (Canada)

Author keywords

[No Author keywords available]

Indexed keywords

CATALYSTS; COPOLYMERIZATION; OLEFINS; OLIGOMERS; ORGANOMETALLICS; POLYMERIZATION;

CYCLOPENTENE; METALLOCENE; POLYCYCLOPENTENE; STEREOCHEMISTRY; TRANSINSERTION MECHANISM;

ORGANIC COMPOUNDS;

EID: 0031548252     PISSN: 00249297     EISSN: None     Source Type: Journal    
DOI: 10.1021/ma961724r     Document Type: Article

References (41)

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15. The rate of disappearance of monomer with time is also consistent with a mechanism in which propagation is first order in monomer and catalyst concentration, but there is a catalyst deactivation process that is second order in catalyst concentration and independent of monomer concentration. However, experiments at higher monomer concentration (and model but were consistent with second-order kinetics (Figure 1). For a discussion of triggered insertions in propylene polymerization, see: Ystenes, M. J. Mol. Catal. 1991, 129, 383.
16. 0 zirconocene complexes, the arrangement depicted in eq 1, seems more plausible. For a review, see: Jordan, R. F. Adv. Organomet. Chem. 1991, 32, 352 and references therein.
17. 13 was reduced and the amount of low MW material formed is greatly diminished, making isolation and characterization of the various fractions formed experimentally demanding: Kelly, W. M. Ph.D. Thesis, University of Waterloo, Waterloo, Ontario, Canada, 1994.
18. 1 in the starting material.
19. Control experiments revealed that the dimer was not homopolymerized by catalyst 2.
20. 2H NMR spectrum (Figure 3b). The formation of these isomers must arise from further isomerization of the intermediates leading to 10t and 10c (Scheme 2) prior to cyclopentene insertion. equation presented
21. 2) ppm. For detailed studies, consult: Kelly, W. M. Ph.D. Thesis, University of Waterloo, Waterloo, Ontario, Canada, 1994.
22. 13C NMR spectroscopy under conditions where trans-1,3 insertion of cyclopentene is facile (e.g., 25 °C).
23. 8) were copolymerized with cyclopentene (5.0 mL), the ether-soluble portion was found to contain ca. 92% of the total deuterium added; very little was incorporated into higher MW polymer, as would be expected for a reversible chain-transfer mechanism. Kelly, W. M. Ph.D. Thesis, University of Waterloo, Waterloo, Ontario, Canada, 1994.
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29. This assumption does not change the overall conclusions regarding isotopic perturbation of stereochemistry. This is because the isotope effects associated with these competing insertion/propagation processes are expected to largely cancel out. However, the absolute magnitude of the observed isotope effect is probably not that meaningful from a mechanistic perspective.
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