New Titanium Complexes Having Two Pyrrolide-Imine Chelate Ligands: Syntheses, Structures, and Ethylene Polymerization Behavior

详细信息    查看全文

• 作者：Yasunori Yoshida ; Shigekazu Matsui ; Yukihiro Takagi ; Makoto Mitani ; Takashi Nakano ; Hidetsugu Tanaka ; Norio Kashiwa ; and Terunori Fujita
• 刊名：Organometallics
• 出版年：2001
• 出版时间：November 12, 2001
• 年：2001
• 卷：20
• 期：23
• 页码：4793 - 4799
• 全文大小：94K
• 年卷期：v.20,no.23(November 12, 2001)
• ISSN：1520-6041

文摘

New titanium complexes 1-4 having two nonsymmetric bidentate pyrrolide-imine chelateligands, [2-(RNCH)C₄H₃N]₂TiCl₂ (1, R = Ph; 2, R = Et; 3, R = n-hexyl; 4, R = cyclohexyl),are prepared in good yields from the lithium salt of the corresponding ligands and TiCl₄.Complex 1 is suggested by DFT calculations to adopt a distorted-octahedral structure inwhich the two pyrrolide-N atoms are situated in trans positions, while the two imine-Natoms and the two Cl atoms are located cis to one another. The spatial disposition elucidatedby X-ray crystallographic analysis of complex 1 is consistent with the preferred structurepredicted by DFT calculations. The molecular structures of complexes 2 and 4 establishedby X-ray analyses are very similar to that of complex 1. DFT calculations suggest that anactive species derived from complex 1, for ethylene polymerization, possesses cis-locatedactive sites trans to the imine-N atoms. These complexes were investigated as ethylenepolymerization catalysts. Using methylalumoxane (MAO) as a cocatalyst, these complexesdisplay very high activities and produce high-molecular-weight polyethylenes. Among them,complex 4 exhibits the highest activity (14 100 kg of polymer/((mol of Ti) h) comparable tothat of Cp₂TiCl₂ with a very high molecular weight (M_v) value of 2 601 000. Alternatively,using Ph₃CB(C₆F₅)₄/i-Bu₃Al as a cocatalyst, these complexes produce ultrahigh-molecular-weight polyethylenes (M_v > 4 000 000) with high activities (1500-2000 kg of polymer/((molof Ti)/h).