| Autor: |
Kouji Imaoka, Takefumi Yano, Shigeru Ikai, Kai Yoshiyuki, Hiroshi Nakazawa |
| Rok vydání: |
1998 |
| Předmět: |
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| Zdroj: |
Journal of Molecular Catalysis A: Chemical. 132:33-41 |
| ISSN: |
1381-1169 |
| DOI: |
10.1016/s1381-1169(97)00234-3 |
| Popis: |
Zirconium and titanium complexes containing hydrotris(pyrazolyl)borate (Tp) or hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) as a ligand have been examined as polymerization precatalysts for ethylene, propylene and styrene. Activation of the group 4 transition-metal complexes by methylaluminoxane exhibits a greater catalytic activity in ethylene polymerization for TpMCl3 (M=Zr, Ti) than for the corresponding mono-cyclopentadienyl analogue, CpMCl3. Dimethyl substitution on the pyrazolyl groups enhances the activity for the Zr complex (Tp*ZrCl3), but not for the Ti complex (Tp*TiCl3). Complete substitution of OtBu or OPh groups for Cl ligands in Tp*ZrCl3 greatly decreases the activity. Mono substitution of an OPh group for one Cl ligand in Tp*TiCl3 does not affect the activity. The addition of propylene comonomer reduces the catalytic activity of Zr complexes containing Tp or Tp* to a considerable degree. The Tp and Tp* complexes of Zr and Ti produce atactic polymers from styrene. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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Full Text from ScienceDirect