The catalyst iPr[3-Me-Cp][Flu] ZrCl 2 (first line in the box), with a methyl group
at the Cp ring, shows hemiisotactic behavior at 10
C with a mmmm pentad of
13.4%, and increases the isotactic pentad to 26.9% with rising temperature up to
70
C. The catalyst iPr[3-Et-Cp][Flu] ZrCl 2 , with the bulkier ethyl group at the
Cp ring, further increases the isotacticity with rising temperature from 11.3% at
10
C to 31% at 70
C. The catalyst iPr[3-iPr-Cp][Flu] ZrCl 2 , with the even more
bulky isopropyl group at the Cp ring, again further increases the isotacticity
from 15.4% to 44% with rising temperatures, i.e., by nearly a factor of three.
The catalyst iPr[3-tBu-Cp][Flu] ZrCl 2 , with the most sterically demanding tertiary
butyl group at the Cp ring, shows highly isotactic behavior, with scarcely any
alteration with rising temperature (only from 83.5% to 87.8%).
Fig. 22 Stereospecific propylene polymerization: the rotation effect
Contributions to the Ziegler–Natta Catalysis: An Anthology
25
at the Cp ring, shows hemiisotactic behavior at 10
C with a mmmm pentad of
13.4%, and increases the isotactic pentad to 26.9% with rising temperature up to
70
C. The catalyst iPr[3-Et-Cp][Flu] ZrCl 2 , with the bulkier ethyl group at the
Cp ring, further increases the isotacticity with rising temperature from 11.3% at
10
C to 31% at 70
C. The catalyst iPr[3-iPr-Cp][Flu] ZrCl 2 , with the even more
bulky isopropyl group at the Cp ring, again further increases the isotacticity
from 15.4% to 44% with rising temperatures, i.e., by nearly a factor of three.
The catalyst iPr[3-tBu-Cp][Flu] ZrCl 2 , with the most sterically demanding tertiary
butyl group at the Cp ring, shows highly isotactic behavior, with scarcely any
alteration with rising temperature (only from 83.5% to 87.8%).
Fig. 22 Stereospecific propylene polymerization: the rotation effect
Contributions to the Ziegler–Natta Catalysis: An Anthology
25