Polymerization of olefins with titanium and zirconium complexes containing hydrotris(pyrazolyl)borate or hydrotris(3,5-dimethylpyrazolyl)borate

✍ Scribed by Hiroshi Nakazawa; Shigeru Ikai; Kouji Imaoka; Yoshiyuki Kai; Takefumi Yano

• Book ID: 104423608
• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 123 KB
• Volume: 132
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/s1381-1169(97)00234-3

✦ Synopsis

Ž

. Ž . Ž . Zirconium and titanium complexes containing hydrotris pyrazolyl borate Tp or hydrotris 3,5-dimethylpyrazolyl borate Ž ) . 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 Ž . TpMCl M s Zr, Ti than for the corresponding mono-cyclopentadienyl analogue, CpMCl . Dimethyl substitution on the 3 3

. pyrazolyl groups enhances the activity for the Zr complex Tp ZrCl , but not for the Ti complex Tp TiCl . Complete 3 3 substitution of O t Bu or OPh groups for Cl ligands in Tp ) ZrCl greatly decreases the activity. Mono substitution of an OPh 3 group for one Cl ligand in Tp ) TiCl does not affect the activity. The addition of propylene comonomer reduces the catalytic 3 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.