- Di- and trinuclear iron/titanium and iron/zirconium complexes with heterocyclic ligands as catalysts for ethylene polymerization
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The properties of polyolefin resins depend very much on their molecular weights, the amount of side chain branchings and molecular weight distributions. One way to obtain such tailored products in only one reaction step consists in the application of dissymmetric multi nuclear catalysts with different active sites. Since every active site is producing its own polymer, a “molecular blending” is the result. In order to reach this goal, a variety of mono, di- and trinuclear complexes of iron, titanium and zirconium, containing 2,6-bis(aryliminoethyl)pyridine and phenoxyimine building blocks have been synthesized and characterized. The reaction of iodo functionalized 2,6-bis(arylimino-ethyl)pyridine derivatives with alkyne functionalized phenoxyimine compounds via Sonogashira cross-coupling reactions results in ligand precursors that can provide coordination sites for two different metals. Trinuclear complexes with the combinations Ti/Fe and Zr/Fe, each molecule containing two iron atoms in two 2,6-bis(aryliminoethyl)pyridine units, gave the best ethylene polymerization results. Due to fast ligand exchange reactions, dinuclear iron/titanium complexes could not be isolated from reactions of mono(phenoxyimine) titanium complexes and the coupled bis(chelate) ligand precursor. Since the metal centers show their best performances at different polymerization temperatures, the compositions (and, therefore, the molecular weight distributions) of the desired polyethylenes may be adjusted by a simple change of the reaction temperature.
- G?rl, Christian,Betthausen, Eva,Alt, Helmut G.
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- Trialkylaluminums: Efficient cocatalysts for bis(phenoxy-imine)zirconium complexes in ethylene polymerization
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Trialkylaluminums as cocatalysts for bis(phenoxy-imine)Zr complexes, bis[N-(3-tert-butylsalicylidene)-anilinato]zirconium dichloride (1) and bis[N-(3-tert-butylsalicylidene)-cyclohexylaminato]zirconium dichloride (2), are investigated for ethylene polymer
- Liu, Dongbing,Wang, Shibo,Wang, Hongtao,Chen, Wei
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- Ethylene polymerization activity under practical conditions displayed by zirconium complexes having two phenoxy-imine chelate ligands
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Ethylene polymerization using zirconium complexes having two phenoxy-imine chelate ligands was investigated at 50 and 75°C at 0.9 MPa ethylene pressure. The activity of the proto-catalyst, N-[(3-t-butylsalicylidene)anilinato]zirconium(IV)-dichloride (1), decreased by increasing the polymerization temperature (50°C: 1192kg-PE/mmol-Zr·h, 75°C: 209kg-PE/mmol-Zr·h). The introduction of an electron donating group, such as an n-hexyl and a methoxy group, on the imine nitrogen or at the para-position of phenoxy oxygen in a benzene ring suppressed the activity decrease, however, the activity at 75°C was still lower than that at 50°C. The combination of an n-hexyl or a cyclohexyl group on the imine nitrogen and a methoxy group at the para-position of the phenoxy oxygen enhanced activity at 75°C. Thus, N-[(3-t-butyl-5-methoxysalicylidene)-n-hexylaminato]zirconium(IV)dichloride (5) and N-[(3-t-butyl-5-methoxysalicylidene)cyclohexylaminato]zirconium(IV)dichloride (6) displayed activities of greater than 1000 kg-PE/mmol-Zrh. Moreover, the introduction of an adamantyl or a cumyl group at the position adjacent to the phenoxy oxygen further increased the activity. N-[(3-Adamantyl-5-methoxysalicylidene)cyclohexylaminato]zirconium(IV) dichloride (7), N-[(3-cumyl-5-methoxysalicylidene)-n-hexylaminato]zirconium(IV)dichloride (8), and N-[(3-cumyl-5-methoxysalicylidene)cyclohexylaminato]zirconium(IV)dichloride (9) displayed exceptionally high activity (7: 3052kg-PE/mmol-Zr·h, 8: 7078 kg-PE/mmol-Zr·h, 9: 7224kg-PE/mmol-Zr·h).
- Matsukawa, Naoto,Matsui, Shigekazu,Mitani, Makoto,Saito, Junji,Tsuru, Kazutaka,Kashiwa, Norio,Fujita, Terunori
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- Post-metallocenes: Catalytic perfomance of new bis(salicylaldiminato) zirconium complexes for ethylene polymerization
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New bis(salicylaldiminato) zirconium complexes were synthesized and investigated as ethylene polymerization catalysts. As a result, we demonstrated that high molecular weight (Mw: 71.6 × 104) and super high activity (2096 kg-PE/mmol-Zr-h) were accomplished by changing the ligand structure.
- Matsui, Shigekazu,Mitani, Makoto,Saito, Junji,Matsukawa, Naoto,Tanaka, Hidetsugu,Nakano, Takashi,Fujita, Terunori
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p. 554 - 555
(2007/10/03)
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