Chemistry Reference
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Tab. 2.5
Polymerization experiments with nickel dibromo complexes.
10
6
M
w
a)
[g mol
-1
]
N
b)
T
m
c)
[
C]
Run
Catalyst n (Cat.)
[
mol]
Time
[min]
Activity
[kg(PE)
[mol(Ni) h]
-1
]
D
1
6d
20
15
4000
3.98
2.3
55
92
2
9b
40
60
1200
>4.0
-
22
112
3
9c
40
60
400
>4.0
-
38
105
4
6c
20
15
6500
>4.0
-
0
130
p
(Ethene): 10 bar.
a)
Measured in 1,2,4-trichlorobenzene at 135
C; all molecular weights relative to narrow polystyrene
standards; molecular weights of more than 4.0
10
6
are outside of the range of the used GPC set-
up.
b)
Methyl groups/1000 carbon atoms (predominantly methyl branches).
c)
Determined by DSC measurements.
2.4.2
Ethene Oligomerization Reactions
Different P
N ligands were applied in olefin polymerization as well as in olefin/
CO copolymerization [9, 43, 47]. Complex
11a
was tested for ethene polymeriza-
tion in CH
2
Cl
2
after activation of the complex with sodium tetrakis(3,5-bis(tri-
fluoromethyl)phenyl)borate (NaBAF) in diethyl ether. The reaction products were
characterized by GC/MS which was calibrated using commercially available
-ole-
fins (1-octene, 1-decene and 1-dodecene) as standards. Oligomers with molecular
weights between 112 g mol
-1
(C
8
) and 448 g mol
-1
(C
32
) were detected. As ex-
pected, only signals for olefins with an even number of carbon atoms were ob-
served. In the GC/MS spectra for each C
n
-fraction (C
8
-C
32
) one intense as well as
several less intense signals were detected. We attribute the main signal to the lin-
ear
-olefin (in accordance with our linear standards used for calibration). An in-
fluence of the polymerization pressure on the isomer distribution could not be de-
termined as was also found for other palladium catalysts [39a]. At 10 and 60 bar
the content of 1-octene within the C
8
-fraction was 94 and 98%. Comparison of the
results of runs 1 and 2 suggests that at higher ethene pressure the formation of
higher molecular weight oligomers is favored, as expected. The catalyst system
11a
/NaBAF, as well as the corresponding palladium systems containing the P
P
ligand 1,3-bis((bis(2-methylphenyl)phosphino)propane ((2-Me)
2
P
P(2-Me)
2
)) or
the (py)N
N(im) ligand (pyridine and 2,6-diisopropylphenyl substituted imine)
oligomerize ethene to an isomeric mixture of olefins [39d, 42a]. The contents of
the linear olefins is significantly higher for the catalyst system
11 c
/NaBAF (94%)
than for the system containing the (2-Me)
2
P
P(2-Me)
2
ligand (
-olefins <5%). Be-
sides, the maximum chain length obtained with
11c
(C
32
) is significantly higher
than with the (2-Me)
2
P
P(2-Me)
2
(C
16
) system. In polymerization experiments
with (py)N
N(im) several isomers of the C
n
fraction were obtained (for example
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