Living Polymerization of Ethylene Catalyzed by Titanium Complexes Having Fluorine-Containing Phenoxy-Imine Chelate Ligands
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- 作者：Makoto Mitani ; Jun-ichi Mohri ; Yasunori Yoshida ; Junji Saito ; Seiichi Ishii ; Kazutaka Tsuru ; Shigekazu Matsui ; Rieko Furuyama ; Takashi Nakano ; Hidetsugu Tanaka ; Shin-ichi Kojoh ; Tomoaki Matsugi ; Norio
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：April 3, 2002
- 年：2002
- 卷：124
- 期：13
- 页码：3327 - 3336
- 全文大小：160K
- 年卷期：v.124,no.13(April 3, 2002)
- ISSN：1520-5126
文摘
Seven titanium complexes bearing fluorine-containing phenoxy-imine chelate ligands, TiCl2{
2-1-[C(H)=NR]-2-O-3-tBu-C6H3}2 [R = 2,3,4,5,6-pentafluorophenyl (1), R = 2,4,6-trifluorophenyl (2), R= 2,6-difluorophenyl (3), R = 2-fluorophenyl (4), R = 3,4,5-trifluorophenyl (5), R = 3,5-difluorophenyl (6),R = 4-fluorophenyl (7)], were synthesized from the lithium salt of the requisite ligand and TiCl4 in goodyields (22%-76%). X-ray analysis revealed that the complexes 1 and 3 adopt a distorted octahedral structurein which the two phenoxy oxygens are situated in the trans-position while the two imine nitrogens and thetwo chlorine atoms are located cis to one another, the same spatial disposition as that for the correspondingnonfluorinated complex. Although the Ti-O, Ti-N, and Ti-Cl bond distances for complexes 1 and 3 arevery similar to those for the nonfluorinated complex, the bond angles between the ligands (e.g., O-Ti-O,N-Ti-N, and Cl-Ti-Cl) and the Ti-N-C-C torsion angles involving the phenyl on the imine nitrogenare different from those for the nonfluorinated complex, as a result of the introduction of fluorine atoms.Complex 1/methylalumoxane (MAO) catalyst system promoted living ethylene polymerization to producehigh molecular weight polyethylenes (Mn > 400 000) with extremely narrow polydispersities (Mw/Mn < 1.20).Very high activities (TOF > 20 000 min-1 atm-1) were observed that are comparable to those of Cp2ZrCl2/MAO at high polymerization temperatures (25, 50 
C). Complexes 2-4, which have a fluorine atom adjacentto the imine nitrogen, behaved as living ethylene polymerization catalysts at 50 C, whereas complexes5-7, possessing no fluorine adjacent to the imine nitrogen, produced polyethylenes having Mw/Mn valuesof ca. 2 with 
-hydrogen transfer as the main termination pathway. These results together with DFTcalculations suggested that the presence of a fluorine atom adjacent to the imine nitrogen is a requirementfor the high-temperature living polymerization, and the fluorine of the active species for ethylenepolymerization interacts with a -hydrogen of a polymer chain, resulting in the prevention of -hydrogentransfer. This catalyst system was used for the synthesis of a number of unique block copolymers such aspolyethylene-b-poly(ethylene-co-propylene) diblock copolymer and polyethylene-b-poly(ethylene-co-propylene)-b-syndiotactic polypropylene triblock copolymer from ethylene and propylene.
2-1-[C(H)=NR]-2-O-3-tBu-C6H3}2 [R = 2,3,4,5,6-pentafluorophenyl (1), R = 2,4,6-trifluorophenyl (2), R= 2,6-difluorophenyl (3), R = 2-fluorophenyl (4), R = 3,4,5-trifluorophenyl (5), R = 3,5-difluorophenyl (6),R = 4-fluorophenyl (7)], were synthesized from the lithium salt of the requisite ligand and TiCl4 in goodyields (22%-76%). X-ray analysis revealed that the complexes 1 and 3 adopt a distorted octahedral structurein which the two phenoxy oxygens are situated in the trans-position while the two imine nitrogens and thetwo chlorine atoms are located cis to one another, the same spatial disposition as that for the correspondingnonfluorinated complex. Although the Ti-O, Ti-N, and Ti-Cl bond distances for complexes 1 and 3 arevery similar to those for the nonfluorinated complex, the bond angles between the ligands (e.g., O-Ti-O,N-Ti-N, and Cl-Ti-Cl) and the Ti-N-C-C torsion angles involving the phenyl on the imine nitrogenare different from those for the nonfluorinated complex, as a result of the introduction of fluorine atoms.Complex 1/methylalumoxane (MAO) catalyst system promoted living ethylene polymerization to producehigh molecular weight polyethylenes (Mn > 400 000) with extremely narrow polydispersities (Mw/Mn < 1.20).Very high activities (TOF > 20 000 min-1 atm-1) were observed that are comparable to those of Cp2ZrCl2/MAO at high polymerization temperatures (25, 50 C). Complexes 2-4, which have a fluorine atom adjacentto the imine nitrogen, behaved as living ethylene polymerization catalysts at 50 C, whereas complexes5-7, possessing no fluorine adjacent to the imine nitrogen, produced polyethylenes having Mw/Mn valuesof ca. 2 with -hydrogen transfer as the main termination pathway. These results together with DFTcalculations suggested that the presence of a fluorine atom adjacent to the imine nitrogen is a requirementfor the high-temperature living polymerization, and the fluorine of the active species for ethylenepolymerization interacts with a -hydrogen of a polymer chain, resulting in the prevention of -hydrogentransfer. This catalyst system was used for the synthesis of a number of unique block copolymers such aspolyethylene-b-poly(ethylene-co-propylene) diblock copolymer and polyethylene-b-poly(ethylene-co-propylene)-b-syndiotactic polypropylene triblock copolymer from ethylene and propylene.