Chemistry Reference
In-Depth Information
N
N
Br
Ni
Br
N
Fe
This catalyst was reported to yield 2.66 kg of polyethylene per one minimol of nickel.
Subsequent research efforts have been focused on discovering more efficient catalytic processes
benefiting from cooperative effects between active centers in multinuclear complexes. The idea is to
ultimately mimic the advantageous enzyme characteristics. Thus, for instance, Li, Stern, and Marks
[
303
] reported that in their earlier work they demonstrated that the constrained geometry of binuclear
catalyst + binuclear co catalyst combination
F
F
Ph
3
C
N
Zr
Si
(C
6
H
5
)
3
B
B(C
6
H
5
)
3
Ph
3
C
F
F
Si
Zr
N
affords, via the modification of chain transfer pathway kinetics, significantly enhanced branching in
ethylene homopolymerization and enhanced comonomer incorporation, as well as ethylene plus
1-hexene copolymerization. Such catalysts, however typically produce unacceptably low molecular
weight polyolefins. Earlier, they reported preliminary results that showed that metal-metal proximity
and cocatalyst structure have significant impact in terms of product molecular weight and comonomer
enchainment selectivity. Following that they reported in the subject publication the synthesis of single
methylene-bridged (
-CH
2
-3,3
0
){(
5
-indenyl)[1-Me
2
Si(
t
BuN)](ZrMe
2
)}
2
Zr based catalyst:
m
Z
N
SiMe
2
Me
2
Zr
Me
2
Si
ZrMe
2
N
