Effect of ketimide ligand for ethylene polymerization and ethylene/norbornene copolymerization catalyzed by (cyclopentadienyl)(ketimide)titanium complexes-MAO catalyst systems: Structural analysis for CpTiCl2(NCPh2) |
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Authors: | Kotohiro Nomura Junji Yamada Wei Wang Jingyu Liu |
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Institution: | Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0101, Japan |
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Abstract: | Ligand effects on the catalytic activity and norbornene (NBE) incorporation] for both ethylene polymerization and ethylene/NBE copolymerization using half-titanocenes (titanium half-sandwich complexes) containing ketimide ligand of type Cp′TiCl2NC(R1)R2] Cp′ = Cp (1), C5Me5 (Cp∗, 2); R1,R2 = tBu,tBu (a), tBu,Ph (b), Ph,Ph (c)]-methylaluminoxane (MAO) catalyst systems have been investigated. CpTiCl2NC(tBu)Ph] (1b) CpTiCl2(NCPh2) (1c), and Cp∗TiCl2(NCPh2) (2c) were prepared and identified; the structure of Cp∗TiCl2(NCPh2) (2c) was determined by X-ray crystallography. The catalytic activity for ethylene polymerization increased in the order: 1a > 1b > 1c, suggesting that an electronic nature of the ketimide ligand affects the activity. However, molecular weight distributions for resultant (co)polymers prepared by 1b,c and by 2c-MAO catalyst systems were bi- or multi-modal, suggesting that the ketimide substituent plays a key role in order for these (co)polymerizations to proceed with single catalytically-active species. CpTiCl2(NCtBu2) (1a) exhibited both remarkable catalytic activity and efficient NBE incorporation for ethylene/NBE copolymerization. |
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Keywords: | Titanium Polymerization Homogeneous catalysis Ethylene Norbornene Copolymerization |
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