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Catalytic Behavior of Bis(Pyrrolide‐Imine) and Bis(Phenoxy‐Imine) Titanium Complexes for the Copolymerization of Ethylene with Propylene, 1‐Hexene, or Norbornene
Author(s) -
Yoshida Yasunori,
Nakano Takashi,
Tanaka Hidetsugu,
Fujita Terunori
Publication year - 2003
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1560/3el3-4vvk-erav-62nf
Subject(s) - norbornene , chemistry , imine , 1 hexene , hexene , copolymer , ethylene , polymer chemistry , catalysis , medicinal chemistry , organic chemistry , polymer
This contribution reports the catalytic behavior of bis(pyrrolide‐imine)Ti complexes 1 and 2 , [2‐(RNCH)‐C 4 H 3 N] 2 TiCl 2 ( 1 , R = Ph; 2 , R = cyclohexyl), and bis(phenoxy‐imine)Ti complex 3 , [2‐(Ph‐NCH)‐3‐ t Bu‐C 6 H 3 O] 2 TiCl 2 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 Cp 2 TiCl 2 (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 Cp 2 TiCl 2 (1.2 mol%) under the same conditions. Additionally, complex 3 also promoted higher norbornene incorporation (4.3 mol%) than Cp 2 TiCl 2 and provided a copolymer with extremely narrow molecular weight distribution ( M w / M n 1.14). A correlation exists between electrophilicity of the Ti center in active species and norbornene incorporation.