Chemistry Reference
In-Depth Information
3.3.4
Salicylimine Ni Complexes
Polymerizations with nickel salicylaldimine complexes
87
-
101
were performed in
a 1 L steel autoclave at 40 bar and 30
C. The nickel complexes (0.09 mmol) were
activated with equimolar amounts of Ni(COD)
2
in toluene solutions for 30 min
after which the autoclave was pressurized with ethene. The reaction was termi-
nated after 1.5 h by venting the ethene and the formed polymer powder was iso-
lated. Details are summarized in Tab. 3.9. For comparison, complex
134
, a nickel
salicylaldimine complex with a 2,6-(diisopropyl)phenyl
imine substituent, was
screened under the same conditions.
Nearly all complexes with an unsubstituted phenyl group in the ligand back bone
(
87
,
91
,
92
,
134
) show a rather poor polymerization activity. The activity was signifi-
cantly higher with complexes (
95
,
96
,
99
,
100
) where the phenyl group bears two
tert
-
butyl substituents. In addition, the polymers obtained with the latter have a narrow
molecular weight distribution while the former display a broad distribution or a low
molecular weight. No clear trend arises from the data regarding a structure-activity
relationship. In marked contrast to the diimine catalyst systems described above,
structural changes in the ligand backbone of nickel salicylaldimine complexes did
not impact the polymerization behavior to a major extent.
3.3.5
Hydroxyimine Ni Complexes
The 2-hydroxyimine nickel system was screened for polymerization activity in a
six-chamber autoclave (Fig. 3.13) operated at 15 bar and using toluene as solvent.
It was found that both types of complexes - NiPh(PPh
3
) and NiMe(ylid) - were
polymerization inactive and needed a coreagent.
Tab. 3.9
Polymerizations with Ni salicylaldimine complexes.
a)
[dL g
-1
]
M
w
b)
[g mol
-1
]
M
n
b)
[g mol
-1
]
M
w
/M
n
b)
Total CH
3
c)
[CH
3
/1000C]
Catalyst
Activity [gPE
[(mmol · h · cat.)
-1
]
87
96.5
2.27
275,400
12,700
21.6
29.0
91
31.6
0.38
n.d.
n.d.
n.d.
40.6
92
7.3
1.50
102,900
3,900
26.4
34.5
95
125.0
0.57
14,400
8,000
1.8
39.7
96
272.0
0.97
33,200
10,900
3.0
26.1
99
138.2
0.38
12,700
6,900
1.9
35.0
100
287.4
0.10
n.d.
n.d.
n.d.
82.0
134
5.4
0.47
n.d.
n.d.
n.d.
23.7
a)
Viscosity, determined in decalin at 180
C.
b)
Determined by GPC.
c)
Determined by IR. n.d.: not determined.
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