Influence of ligands and cocatalyst on the activity in ethylene polymerization of soluble titanium complexes

Conti, Giuseppe; Arribas, Guillermo; Altomare, Angelina; Ciardelli, Francesco

doi:10.1016/0304-5102(93)e0290-w

Cited by 15 publications

(2 citation statements)

References 10 publications

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“…Recently, Group 4 transition metal complexes containing noncyclopentadiene ligands such as amidinate,1, 2 amido,3, 4 oxazolin,5 porphyrin,6 alkoxy,7 aryloxy,8–10 and ketonate11, 12 have been developed as catalyst precursors for olefin polymerization. Admittedly, as we know those complexes were found to have lower catalytic activity for ethylene polymerization relative to metallocene catalysts.…”

Section: Introductionmentioning

confidence: 99%

A kind of novel nonmetallocene catalysts for ethylene polymerization

Sheng

Huang

et al. 2007

J. Polym. Sci. A Polym. Chem.

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A kind of novel bridged nonmetallocene catalysts was synthesized by the treatment of N,N‐imidazole and N,N‐phenylimidazole with n‐BuLi, and MCl4 (M = Ti, Zr) in THF. Those catalysts were performed for ethylene polymerization after activated by methylaluminoxane (MAO). The effects of polymerization temperature, Al/M ratio, pressure of monomer, and concentration of catalysts on ethylene polymerization behaviors were investigated in detail. Those results revealed that the catalyst system was favorable for ethylene polymerization with high catalytic activity. The polymer was characterized by 13C NMR, WAXD, GPC, and DSC. The result confirmed that the obtained polyethylene featured broad molecular weight distribution around 20, linear structure, and relative low melting temperature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 33–37, 2008

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Section: Introductionmentioning

confidence: 99%

A kind of novel nonmetallocene catalysts for ethylene polymerization

Sheng

Huang

et al. 2007

J. Polym. Sci. A Polym. Chem.

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“…Among others, they are sensitive to both the electronic and steric surroundings of the active site. These factors can be regulated by careful manipulation of the ligands, and several reports show that the choice of ligands and the catalysts' performance are related. − For example, an increase in the electron-withdrawing ability of the substituents on the aromatic ligand lowers both the propagation rate 8,9 and the molecular weight 8 whereas the catalytic activity has been claimed to be inversely proportional to the steric demands of the ring systems . The main focus in these studies has been on the catalytic activity and the molecular weight as determined by size exclusion chromatography.…”

Section: Introductionmentioning

confidence: 99%

Ethene Polymerization Catalyzed by Monoalkyl-Substituted Zirconocenes. Possible Effects of Ligand−Metal Agostic Interaction

2000

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Polymerization of ethene catalyzed by nine different zirconocenes with the general formula (η 5 -C5H4R)2 ZrCl2 (R ) H, alkyl) activated by methylaluminoxane (MAO) has been performed. Kinetic data and mechanistic interpretations in terms of propagation, termination, and isomerization are presented. At T ) 50 °C, the time to reach maximum activity increases with the length of R, from 1 min with R ) H to about 20 min with the longest alkyl substituents. The propagation rate is analyzed by kinetic modeling. At T ) 50 °C, both the highest average activity and propagation rate are achieved with R ) n-propyl. At higher temperatures, no systematic differences can be observed between the different catalysts. Polymer unsaturation is studied by infrared spectroscopy. Alkyl substitution on the cyclopentadienyl ligand shifts the distribution from vinyl toward trans-vinylene. We rationalize this by a competition between termination and isomerization reactions where kinetics is the decisive factor. At T ) 50 °C, the highest trans-vinylene content is found for R ) n-propyl. Density functional calculations show that for R ) ethyl and longer an additional agostic interaction between the metal center and a hydrogen on the alkyl substituent may be important. We suggest that this has an impact on the kinetics and is responsible for several experimental observations.

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Metallocene Catalysts for Olefin Polymerization

Janiak¹

1998

Metallocenes

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Influence of ligands and cocatalyst on the activity in ethylene polymerization of soluble titanium complexes

Cited by 15 publications

References 10 publications

A kind of novel nonmetallocene catalysts for ethylene polymerization

A kind of novel nonmetallocene catalysts for ethylene polymerization

Ethene Polymerization Catalyzed by Monoalkyl-Substituted Zirconocenes. Possible Effects of Ligand−Metal Agostic Interaction

Metallocene Catalysts for Olefin Polymerization

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