Catalytic Behavior of Bis(Pyrrolide-Imine) and Bis(Phenoxy-Imine) Titanium Complexes for the Copolymerization of Ethylene with Propylene, 1-Hexene,or Norbornene |
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Authors: | Yasunori Yoshida Takashi Nakano Hidetsugu Tanaka Terunori Fujita |
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Affiliation: | R&D Center, Mitsui Chemicals, Inc., 580-32 Nagaura, Sodegaura-City, Chiba 299-0265, Japan |
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Abstract: | This contribution reports the catalytic behavior of bis(pyrrolide-imine)Ti complexes 1 and 2 , [2-(RNCH)-C4H3N]2TiCl2 ( 1 , R = Ph; 2 , R = cyclohexyl), and bis(phenoxy-imine)Ti complex 3 , [2-(Ph-NCH)-3-t Bu-C6H3O]2TiCl2 for the copolymerization of ethylene with propylene, 1-hexene, or norbornene. An inspection of the X-ray structures of complexes 1–3 suggested that complexes 1 and 2 with pyrrolide-imine ligands would provide more space for olefin polymerization than complex 3 with phenoxy-imine ligands. In addition, DFT calculations also showed that active species derived from complexes 1 and 2 possess higher electrophilicity of the Ti center compared to that from complex 3 . Complexes 1 and 2 on activation with methylalumoxane (MAO) had higher affinity for propylene and 1-hexene and incorporated higher amounts of propylene ( 1 ; 30.5 mol%, 2 ; 23.4 mol%) and 1-hexene ( 1 ; 1.9 mol%, 2 ; 1.7 mol%) than complex 3 (propylene; 4.5 mol%, 1-hexene; 0.4 mol%). The incorporation levels of propylene and 1-hexene displayed by complexes 1 and 2 were lower than those for Cp2TiCl2 (propylene; 41.6 mol%, 1-hexene; 5.1 mol%) under identical conditions. In contrast, complexes 1 and 2 exhibited higher incorporation ability for norbornene and produced copolymers with much higher norbornene contents ( 1 ; 32.0 mol%, 2 ; 26.5 mol%) than Cp2TiCl2 (1.2 mol%) under the same conditions. Additionally, complex 3 also promoted higher norbornene incorporation (4.3 mol%) than Cp2TiCl2 and provided a copolymer with extremely narrow molecular weight distribution (Mw/Mn 1.14). A correlation exists between electrophilicity of the Ti center in active species and norbornene incorporation. |
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