2-(1-(Arylimino)ethyl)-8-arylimino-5,6,7-trihydroquinoline iron(II) chloride complexes: Synthesis, characterization, and ethylene polymerization behavior

Article abstract of DOI:10.1021/om300388m

The series of 2-(1-(arylimino)ethyl)-8-arylimino-5,6,7-trihydroquinolines was synthesized and fully characterized, for which data indicated two isomer forms of each due to the migration of a double bond. The corresponding iron dichloride complexes were prepared and were found to adopt distorted bipyramidal coordination geometry at iron by single-crystal X-ray diffraction studies. Upon treatment with either MAO or MMAO, all iron complex precatalysts exhibited high activities (up to 2.4 × 10⁷ gPE?mol^-1(Fe) ?h^-1) toward ethylene polymerization. The influence of the nature of the ligands and reaction parameters upon the catalytic activities and properties of the polyethylene obtained has been studied.

Full text of DOI:10.1021/om300388m

Article
pubs.acs.org/Organometallics
2-(1-(Arylimino)ethyl)-8-arylimino-5,6,7-trihydroquinoline Iron(II)
Chloride Complexes: Synthesis, Characterization, and Ethylene
Polymerization Behavior
Wenjuan Zhang,† Wenbin Chai,†,‡ Wen-Hua Sun,*,† Xinquan Hu,*,‡ Carl Redshaw,*,§ and Xiang Hao†
†Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, China
‡College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014, China
§School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, U.K.
S
* Supporting Information
ABSTRACT: The series of 2-(1-(arylimino)ethyl)-8-arylimino-5,6,7-
trihydroquinolines was synthesized and fully characterized, for which
data indicated two isomer forms of each due to the migration of a
double bond. The corresponding iron dichloride complexes were
prepared and were found to adopt distorted bipyramidal coordination
geometry at iron by single-crystal X-ray diffraction studies. Upon
treatment with either MAO or MMAO, all iron complex precatalysts
exhibited high activities (up to 2.4 × 107 gPE·mol−1(Fe)·h−1) toward
ethylene polymerization. The influence of the nature of the ligands and reaction parameters upon the catalytic activities and
properties of the polyethylene obtained has been studied.
producing highly linear products is of industrial interest
whether they are from the oligomerization of α-olefins or
from polymerization, i.e., linear (density) polyethylenes
(HDPE).
INTRODUCTION
■
The discovery of bis(arylimino)pyridylmetal (Fe or Co)
dihalides1 as highly active precatalysts for ethylene polymer-
ization heralded a new era in late transition metal based
catalysis research and led to extensive studies into the catalytic
behavior of analogous systems,2 catalytic intermediates/active
species,3 and reaction mechanisms.4 The progress in this area
has been reported in a number of comprehensive review
articles.5 In order to fine-tune the catalytic behavior of such
metal complex precatalysts, it was recognized that the different
sizes of the ligand sets employed played an important role,1,2
and extensive variations of both the sterics6,7 and electronic
effects,8 including the synthesis of unsymmetrical diiminopyr-
idine ligands, were conducted.1,6b,7 Moreover, the exploration
for alternative models for iron complex precatalysts, beyond
those of the original bis(imino)pyridine framework, has been
attracting great attention. In particular, efficient precatalysts
have been designed using new multidentate frameworks
(Scheme 1) including those based on 2-imino-1,10-phenan-
throlines (A),9 2-(benzimidazol-2-yl)-1,10-phenanthrolines
(B),10 2-(pyrid-2-yl)-1,10-phenanthrolines (C),11 2-(benzimi-
dazol-2-yl)-6-iminopyridines (D),12 2-(benzoxazol-2-yl)-6-imi-
nopyridines (E),13 2-(benzothiazol-2-yl)-6-iminopyridines
(F),14 2-quinoxalinyl-6-iminopyridines (G),15 2-(pyrid-2-yl)-6-
iminopyridines (H),16 2-methyl-2,4-bis(6-iminopyridin-2-yl)-
1H-1,5-benzodiazepines (I),17 iminoquinolines (J),18 2,8-bis-
(imino)quinolines (K),19 8-(benzimidazol-2-yl)-2-iminoquino-
lines (L),20 and more recently 8-(benzimidazol-2-yl)quinolines
(M)21 and 1,8-diimino-2,3,4,5,6,7-hexahydroacridines (N).22
For the iron-based catalytic systems, the advantage of
Consideration of both the ligand models of 1,8-diimino-
2,3,4,5,6,7-hexahydroacridine (N)22 and diiminopyridine1,2
suggests that the hybrid ligand model comprising 2,8-
bis(arylimino)-5,6,7-trihydroquinoline would be worthy of
consideration. Recently, a new nickel precatalyst model has
been successfully designed by employing the fused cyclo-
ketonylpyridine of 5,6,7-trihydroquinolin-8-one derivatives23
instead of using 2-acetylpyridine24 for their iminopyridylnickel
precatalysts, and the resulting new nickel precatalysts exhibited
higher catalytic activity, selectively forming only one kind of
product, either polyethylenes or oligomers.23 For the 2,8-
bis(arylimino)-5,6,7-trihydroquinolines, the synthetic proce-
dure using 2-acetyl-5,6,7-trihydroquinolin-8-one was success-
fully achieved, and a series of 2,8-bis(arylimino)-5,6,7-
trihydroquinolines was prepared. The corresponding 2,8-
bis(arylimino)-5,6,7-trihydroquinolyliron dichlorides were
found to exhibit high activity toward ethylene polymerization.
Herein, the synthesis and characterization of the 2,8-bis-
(arylimino)-5,6,7-trihydroquinolines and their iron complexes
are reported, and the catalytic behavior of the iron complexes in
ethylene polymerization has been studied.
Received: May 9, 2012
Published: July 9, 2012
© 2012 American Chemical Society
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Scheme 1. Ligand Frameworks for Late Transition Metal Precatalysts
RESULTS AND DISCUSSION
Scheme 2. Synthetic Procedure for Ligands L1−L5 and Iron
Complexes Fe1−Fe5
■
1. Synthesis of 2-Acetyl-5,6,7-trihydroquinolin-8-one
(4). In order to access the desired ligand set, the initial problem
was how to synthesize 2-acetyl-5,6,7-trihydroquinolin-8-one.
The starting compound is 2-chloro-5,6,7-trihydroquinolin-8-ol
(1), which was prepared according to the literature
procedure.25 It was necessary to transform the hydroxyl
group into an ether function, and this was accomplished as
follows: compound 1 was reacted with an excess amount of
NaH (2 molar equiv) in dichloromethane, then 1.2 equiv of 4-
methoxybenzylchloride (PMBCl) was added, and stirring was
continued at 5 °C for 12 h. 2-Chloro-8-(4-methoxybenzyloxy)-
5,6,7-trihydroquinoline (2) was isolated in good yield. To
transform the chloroarene into acetylarene, the Stille coupling
reaction26 was employed for the reaction of compound 2 with
tributyl(1-ethoxyvinyl)tin (Bu3SnCH(Me)OEt) in the presence
of a catalytic amount of Pd(dppf)Cl2, and then hydrolysis
(addition of hydrochloric acid) preceded to form the 2-acetyl-8-
(4-methoxybenzyloxy)-5,6,7-trihydroquinoline (3) in high
yield. Using the DDQ/TBN/O2 catalytic oxidation,27 com-
pound 3 was transformed into the expected 2-acetyl-5,6,7-
trihydroquinolin-8-one (4) in a reasonable yield. The synthetic
procedure is illustrated in Scheme 2. All new organic
compounds were characterized by FT-IR and NMR spectros-
copy and by elemental analysis.
2. Synthesis and Characterization of Ligands and
Complexes. The condensation reaction of 2-acetyl-5,6,7-
trihydroquinolin-8-one (4) with the requisite aniline was
conducted in n-butanol to afford the corresponding 2,8-
dimino-5,6,7-trihydroquinoline derivatives (L1−L5) in reason-
able isolated yield (43−63%, indicating two isomers in Scheme
2); reactions using the solvents toluene or ethanol produced
the desired ligands in much lower yields (<10%). The H
NMR spectra of L1−L5 were consistent with the existence of
two isomers, namely, the imine (L) and amine (L′), which are
formed due to double-bond migration in and out of the cyclic
ring; the major form is the amine (L′). Similar phenomena were
observed in other analogous compounds.23a,28
for each compound) with 1 equiv of FeCl2·4H2O in freshly
distilled ethanol formed the corresponding iron complexes
bis(imino)-5,6,7-trihydroquinolyliron(II) dichlorides (Fe1−
Fe5, Scheme 2). According to the IR spectra, the signal
around 3360 cm−1 (νN−H), shown for the form L′ of the ligands,
had disappeared for all the iron complexes, indicating no N−H
bond was present within the iron complexes. Only sp2-N−Fe
bonds were exhibited, which excluded the presence of amine
isomers (L′); thus the transformation of L′ into L had occurred
upon coordination with iron chloride, consistent with our
previous observations.23a Elemental analysis data were con-
sistent with the formula LFeCl2. To confirm their unambiguous
1
1
Reaction of the corresponding 2,8-dimino5,6,7-trihydroqui-
noline derivatives (L1−L5 including the amine isomer L1′−L5′
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molecular structures, single crystals of complexes Fe1 and Fe2
were obtained, and the solid-state structures were determined
by single-crystal X-ray diffraction studies. Selected bond lengths
and angles are summarized in Table 1, and the molecular
structures are shown in Figures 1 and 2.
Table 1. Selected Bond Lengths and Angles for Fe1 and Fe2
Fe1
Fe2
Bond Lengths (Å)
2.106(3)
Fe(1)−N(1)
Fe(1)−N(3)
Fe(1)−N(2)
Fe(1)−Cl(1)
Fe(1)−Cl(2)
N(2)−C(11)
N(3)−C(2)
2.069(3)
2.215(3)
2.230(3)
2.2550(13)
2.3318(12)
1.292(5)
1.285(4)
2.243(3)
2.277(3)
2.2940(12)
2.3008(12)
1.293(5)
1.286(5)
Figure 2. Molecular structure of complex Fe2 with thermal ellipsoids
at 30% probability. Hydrogen atoms have been omitted for clarity.
Bond Angles (deg)
N(1)−Fe(1)−N(3)
N(1)−Fe(1)−N(2)
N(3)−Fe(1)−N(2)
N(1)−Fe(1)−Cl(1)
N(3)−Fe(1)−Cl(1)
N(2)−Fe(1)−Cl(1)
N(1)−Fe(1)−Cl(2)
N(3)−Fe(1)−Cl(2)
N(2)−Fe(1)−Cl(2)
Cl(1)−Fe(1)−Cl(2)
C(11)−N(2)−Fe(1)
C(12)−N(2)−Fe(1)
73.13(12)
73.25(11)
146.16(12)
120.35(9)
101.14(9)
98.96(9)
128.95(9)
99.43(9)
98.54(9)
110.68(5)
115.1(2)
125.7(2)
73.20(11)
73.88(11)
141.28(11)
147.03(9)
99.56(8)
97.01(8)
94.48(9)
101.89(9)
100.44(8)
118.46(5)
114.4(2)
125.8(2)
Å) compared to the Fe−Nimino (2.243(3) and 2.277(3) Å); the
differing lengths of the two Fe−Nimino bonds are attributed to
the unsymmetrical framework.
The geometry shown in Figure 2 for complex C2 can be
better described as distorted square pyramidal around the iron
center. Three coordinating nitrogen atoms and one chloride
(Cl1) form the basal plane with deviations of 0.04 Å for the
chloride (Cl1) and 0.583 Å for the iron atom on the different
sides of the basal plane. Similar to the molecular structure of
complex C1, the Fe−Npyridyl (2.069(3) Å) is shorter than that
for the Fe−Nimino (2.215(3) and 2.230(3) Å). Both the
distorted trigonal-bipyramidal geometry for complex C1 and
distorted square-pyramidal geometry for complex C2 have
previously been observed for unsymmetrically bound tridentate
metal complexes.7,12−15
3. Ethylene Polymerization. 3.1. Ethylene Polymer-
ization Results for Fe1−Fe5/MAO Systems. The selection of
suitable cocatalysts was extensively investigated, and both
methylaluminoxane (MAO) and modified methylaluminoxane
(MMAO, 1.93 M in n-heptane) were found to be effective
cocatalysts in activating the iron catalytic system for ethylene
polymerization. The catalytic system of Fe3/MAO was typically
investigated with varying reaction conditions including the
molar ratio of Al/Fe and reaction temperature (Table 2). On
increasing the Al/Fe ratio from 1000 to 2500 (runs 1−4, Table
2), the best catalytic activity (up to 3.27 × 105
gPE·mol−1(Fe)·h−1·atm−1) was achieved at an Al/Fe ratio of
2000, but the molecular weight (Mw) decreased substantially
from 203.4 to 78.9 kg·mol−1; the molecular weight distribution
became particularly broad when the Al/Fe ratio was over 1500
(runs 1−4, Table 2), from 3.4 to 35.9. The GPC traces (Figure
3) further showed this trend, viz., unimodal distribution at Al/
Fe ratios of 1000 and 1500 and multipeak distribution when the
Al/Fe ratio is over 1500. Another observation from the GPC
curves was that the low molecular weight fractions became the
bigger components of the obtained polymers on increasing the
Al/Fe ratio. These results demonstrated that chain transfer to
aluminum played an important role in the formation of a low
Mw fraction.2a
Figure 1. Molecular structure of complex Fe1 with thermal ellipsoids
at 30% probability. Hydrogen atoms have been omitted for clarity.
The molecular structure of Fe1 (Figure 1) reveals a distorted
trigonal-bipyramidal geometry at the metal, in which three
nitrogen atoms and the iron form a coordination plane with a
deviation of 0.40 Å for the iron atom. The coordination plane is
almost perpendicular, with a dihedral angle of 89.55° to the
equatorial plane constructed by the Npyridyl atom and two
chlorides, with N(1)−Fe(1)−Cl(1) = 120.35(9)° and N(3)−
Fe(1)−Cl(1) = 101.14(9)°. Moreover, two phenyl rings (of
2,6-dimethylphenyl) linked to the imino groups are similarly
perpendicular to the coordination plane with dihedral angles of
86.81° and 86.86°, respectively. The Fe−N bond lengths are
slightly different, with a relatively short Fe−Npyridyl (2.106(3)
The polymerization temperature also affected the observed
catalytic activities. Elevating the temperature from 30 to 50 °C
led to an obvious increase of activity (runs 3, 5, 6, Table 2)
from 3.27 to 8.80 × 105 gPE·mol−1(Fe)·h−1·atm−1, while
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a
Table 2. Polymerization Results for Fe1−Fe5/MAO at 10 atm Ethylene Pressure
b
c
c
run
precatalyst
T (°C)
Al/Fe
polymer (g)
activity
Tm (°C)
Mw /kg·mol−1
Mw/Mn
1
Fe3
Fe3
Fe3
Fe3
Fe3
Fe3
Fe3
Fe3
Fe1
Fe2
Fe4
Fe5
30
30
30
30
40
50
60
80
50
50
50
50
1000
1500
2000
2500
2000
2000
2000
2000
2000
2000
2000
2000
2.45
3.12
4.90
3.79
5.95
13.2
11.0
10.2
8.41
23.4
8.34
12.4
1.63
2.08
3.27
2.53
3.97
8.80
7.34
6.81
5.61
15.6
5.56
135.5
133.3
130.6
128.8
128.3
130.7
128.1
127.6
128.7
129.9
128.6
129.8
203.4
132.9
174. 5
78.9
3.4
8.5
2
3
32.5
35.9
23.5
13.9
2.8
4
5
77.0
6
121.6
13.3
7
8
18.5
4.3
9
22.8
4.7
10
11
12
22.7
6.3
31.5
7.2
8.25
29.7
5.3
a
b
c
General conditions: 3 μmol of Fe, 30 min, 100 mL of toluene for 10 atm ethylene. 105 gPE·mol−1(Fe)·h−1·atm−1. Determined by GPC.
Figure 3. GPC curves of the polyethylenes (runs 1−4, Table 2).
Figure 4. GPC curves of polyethylene obtained at different
temperatures (runs 3, 5−8, Table 2).
further increases of the temperature to 80 °C decreased, albeit
slightly, the polymerization activity from 8.80 to 6.81 × 105
gPE·mol−1(Fe)·h−1·atm−1 (runs 6−8, Table 2), indicating that
the active species can withstand high temperatures. In contrast,
the polymerization activity for 1,8-diimino-2,3,4,5,6,7-hexahy-
droacridine iron complexes was found to decrease on elevating
the temperature from 30 to 70 °C,22 and the typical
bis(imino)pyridyl iron precatalysts showed a huge deactivation
in activity along with elevating the reaction temperature in this
range,2a while 2,8-bis(1-aryliminoethyl)quinoline iron com-
plexes showed high activity only at temperatures above 80 °C.19
These results suggested that the backbone of the ligand can
significantly affect the catalytic properties. Generally, the
molecular weight of the resultant polymer decreased rapidly
on increasing the temperature and the molecular distribution
became much broader by an iron precatalyst for ethylene
polymerization. Here, the molecular weight decrease trend is
similar, which is due to the facilitated chain-transfer reaction at
elevated temperatures, but the molecular distribution became
narrower from 32.5 to 2.8 (runs 2, 5−8, Table 2). GPC curves
of the resultant polyethylene in Figure 4 clearly show that the
polymers obtained at 30, 40, and 50 °C have multisite
characteristics, while polymers obtained at 60 and 80 °C
possess a unimodal distribution, suggesting that a single-site
active species probably operates in the catalytic system at these
higher temperatures.
their metal complex precatalysts; better activities were achieved
by employing less bulky substituents.1,22 In the current work,
however, the precatalyst Fe2, containing an ethyl group (R1 =
Et), showed higher activity than its analogues Fe1 (R1 = Me)
and Fe3 (R1 = iPr), and Fe5 (R1 = Et, R2 = Me) was better than
Fe4 (R1 = Me, R2 = Me). The precatalysts Fe4 and Fe5, having
an additional R2 (methyl) group, exhibited slightly lower
activities than did the analogues Fe1 and Fe2, indicating a
negative effect of the electron-donating methyl group on the
para-position of the N-aryl ring.7d,22
Under the same conditions, it was also found that the
i
resultant polymer obtained using Fe3 (R1= Pr) possessed a
much higher molecular weight (Mw: 121.6 kg·mol−1) than that
(22.7−31.5 kg·mol−1) from the use of the analogues Fe1, Fe2,
Fe4, and Fe5, which was consistent with previous observa-
tions.7b,d,22 The Mw usually depends on the size of the ortho-
substituent, and bulky substituents usually result in higher
molecular weight polymers. Interestingly, the molecular weights
of resultant polyethylenes were not significantly affected by the
precatalysts bearing different substituents such as the methyl-
substituted (Fe1, Fe4) and ethyl-substituted analogues (Fe2,
Fe5). All resultant polymers had similar Tm values above 128.9
°C, suggesting a highly linear HDPE; moreover, the 13C NMR
measurements of several representative polyethylenes also
confirmed their high linearity, which agreed with previous
reports.7,29
Using the optimum reaction conditions of Al/Fe 2000 at 50
°C for 30 min, all iron precatalysts Fe1−Fe5 were evaluated for
their ethylene polymerization behavior (runs 9−11, Table 2).
The substituents on the N-aryl ring affected the activities of
3.2. Ethylene Polymerization by Fe1−Fe5/MMAO Systems.
All the iron precatalysts were investigated using MMAO as the
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a
Table 3. Polymerization Results by Fe1−Fe5/MMAO at 10 atm Ethylene Pressure
b
c
c
run
precat
T (°C)
30
Al/Fe
1000
polymer (g)
activity
Tm (°C)
123.6
Mw /kg·mol−1
Mw/Mn
1
Fe3
Fe3
Fe3
Fe3
Fe3
Fe3
Fe3
Fe3
Fe1
Fe2
Fe4
Fe5
Fe3
Fe3
2.91
4.72
6.49
6.00
7.04
22.3
18.9
17.3
22.5
14.7
23.0
20.3
18.0
28.0
1.94
37.8
19.2
13.0
8.1
28.0
12.8
9.3
5.7
9.1
8.9
8.9
4.5
4.0
5.1
6.0
5.8
2.7
11.1
2
30
30
30
40
50
60
70
50
50
50
50
50
50
1500
2000
2500
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
3.14
4.33
4.00
4.69
123.2
123.5
120.5
123.1
128.2
127.7
127.2
126.3
125.2
127.4
126.7
127.5
3
4
5
17.4
32.7
29.9
15.1
11.7
12.9
14.8
12.8
9.8
6
14.8
7
12.6
11.5
14.8
8
9
10
11
12
9.81
15.4
13.5
24.0
12.5
d
13
e
14
128.9
46.2
a
b
c
General conditions: 3 μmol of Fe, Al/Fe: 2000; 100 mL of toluene for 10 atm ethylene, 30 min. 105 gPE·mol−1(Fe)·h−1·atm−1. Determined by
d
e
GPC. 15 min. 40 min.
cocatalyst, and the polymerization results are collected in Table
3. Generally, this catalytic system also exhibited very good
activity for ethylene polymerization without the formation of
any oligomers. First, the Fe3/MMAO catalytic system was
employed for optimizing the conditions. Increasing the Al/Fe
molar ratio from 1000 to 2500, an optimum activity of 4.33 ×
105 gPE·mol−1(Fe)·h−1·atm−1 was achieved at an Al/Fe ratio of
2000, the same ratio as with MAO. The results also showed
that the molecular weights of the polymer (37.8−8.2 kg·mol−1,
runs 1−4 in Table 3) formed by this system were much lower
than those (78.9−203.4 kg·mol−1, runs 1−4 in Table 2) by
MAO under the same conditions, indicating more chain
transfer to the aluminum center in the catalytic process
containing MMAO. On increasing the Al/Fe ratio, the
molecular weight of the resultant polymers decreased
significantly from 37.8 to 8.1 kg·mol−1 (runs 1−4, Table 3),
also suggesting the importance of chain transfer to aluminum in
the polymerization process. In addition, another difference was
that the molecular weight distribution became narrower (28.0
to 5.7) at higher Al/Fe ratios, which is the reverse trend of that
observed using MAO. The GPC traces exhibited unimodal
characteristics.
The influence of temperature was also investigated, and the
optimum temperature was found to be 50 °C (runs 3, 5−8 in
Table 3). On elevating the temperature from 30 to 40 °C, the
activity initially gradually increased, but then rapidly increased
on going from 40 to 50 °C; further elevating the temperature
led to a gradual decrease of the activity. The activity was about
1.48 × 106 gPE·mol−1(Fe)·h−1·atm−1 at 50 °C (run 6, Table 3),
which is slightly higher than that by MAO under the same
conditions. The molecular weight of the resultant polymers had
no obvious trend, and the highest molecular weight was
achieved at 50 °C; however, there were no significant changes
in either the molecular weight or molecular distribution. The
GPC traces (Figure 5) showed a bimodal distribution at lower
Al/Fe ratios and a unimodal distribution at higher Al/Fe ratios,
which is different from that by the iron complexes/MAO
system, probably due to a different active species operating.
Employing the optimum conditions of Al/Fe 2000 at 50 °C
over 30 min, all the iron precatalysts were evaluated for
ethylene polymerization, and results are shown in Table 3. The
iron precatalysts Fe1−Fe5/MMAO system showed very high
activities ((9.81−15.4) × 105 gPE·mol−1(Fe)·h−1·atm−1) for
Figure 5. GPC curves of the polyethylenes (runs 1−4, Table 3).
ethylene polymerization (runs 9−12, Table 3). On comparison
with the systems employing MAO, the Fe/MMAO system
exhibited better activity for ethylene polymerization, but with
lower molecular weight products obtained, which may be due
to increased chain transfer to MMAO.30 Precatalysts Fe4 and
Fe5, bearing electron-donating methyl groups at the para-
position of the aryl ring, performed with slightly higher
activities than did Fe1 and Fe2, indicating the positive effect of
an addition methyl group, which is different from that by MAO
catalytic systems. However, in contrast to the MAO system,
precatalysts Fe2 and Fe5, bearing ethyl substituents at the ortho
positions of aryl ring, exhibited lower activity than did
corresponding Fe1 and Fe4, with methyl substituents. In
these catalytic systems, it was found that polyethylenes
i
obtained using Fe3 (R1 = Pr) possessed a much higher
molecular weight (32.7 kg·mol−1, run 6 in Table 3) than those
(11.7−14.8 kg·mol−1, runs 9−12 in Table 3) from the other
analogues under the same conditions, as was seen for the MAO
system, indicating the efficient inhibition of chain transfer by
the bulky substituent in the polymerization process.
We investigated the effect of the polymerization time on
catalytic activity and polymer properties by employing Fe3/
MMAO under the conditions of 10 atm ethylene, Al/Fe 2000
at 50 °C. Over 15 min, very high activity, up to 2.4 × 106
gPE·mol−1(Fe)·h−1·atm−1, was observed, and the resultant
polymer possessed narrow distribution (PDI = 2.7), character-
istic of single-site catalysis. On prolonging the polymerization
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time (30 and 40 min), the activity decreased rapidly, while the
molecular weight increased and the molecular weight
distribution became much broader (from 2.7 to 8.9, 11.1).
These results suggested that there was partial deactivation of
the active species over time and that multisite active species
then played a major role in the polymerization process.
Table 4. Crystal Data and Structure Refinement for Fe1 and
Fe2
Fe1
Fe2
cryst color
empirical formula
fw
purple
Blue
C27H29Cl2FeN3
522.28
C31H37Cl2FeN3
578.39
T (K)
173 (2)
0.71073
monoclinic
P2(1)/n
13.258(3)
15.273(3)
14.915(3)
90
173(2)
0.71073
monoclinic
P2(1)/c
18.586(4)
8.6751(17)
18.151(4)
90
CONCLUSION
■
wavelength (Å)
cryst syst
space group
a (Å)
A series of 2,8-bis(arylimino)-5,6,7-trihydroquinoline iron
complexes has been synthesized and fully characterized.
Molecular structures of the representative iron complexes Fe1
and Fe2 showed distorted trigonal-bipyramidal geometry or
distorted square-pyramidal geometry at the metal, respectively.
Upon treatment with either MAO or MMAO, all precatalysts
Fe1−Fe5 showed very high activities for ethylene polymer-
ization at 50 °C under 10 atm ethylene, up to 2.4 × 106
gPE·mol−1(Fe)·h−1·atm−1. In particular, using MMAO as the
cocatalyst, this system performed with better activities than
when using MAO, but produced lower molecular weight
polymer. Ethylene activation by the precatalysts and the
properties of the resultant polyethylenes could be controlled
by modifying the reaction parameters and varying the
substituents of the ligands.
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
106.07(3)
90
99.69(3)
90
2902.2(10)
4
2884.8(10)
4
Z
Dcalcd (mgm−3
)
1.195
1.332
μ (mm−1
)
0.721
0.733
F(000)
1088
1216
cryst size (mm)
θ range (deg)
limiting indices
0.17 × 0.13 × 0.07 0.30 × 0.26 × 0.22
2.08−27.49
−9 ≤ h ≤ 17
−18 ≤ k ≤ 19
−19 ≤ l ≤ 17
12 793
1.11−27.51
−24 ≤ h ≤ 24
−7 ≤ k ≤ 11
−23 ≤ l ≤ 22
14 377
EXPERIMENTAL SECTION
■
General Considerations. All air- and/or moisture-sensitive
operations were carried out in an atmosphere of nitrogen using
standard Schlenk techniques. The solvents were purified and dried
under nitrogen by conventional methods prior to use unless otherwise
stated. Methylaluminoxane (1.46 M solution in toluene) and modified
methylaluminoxane (MMAO, 1.93 M in n-heptane) were purchased
from Akzo Nobel Corp. High-purity ethylene was purchased from
Beijing Yanshan Petrochemical Co. and used as received. Other
reagents were purchased from Aldrich, Acros, or local suppliers. NMR
spectra were recorded on a Bruker DMX 400/500/600 MHz
instrument at ambient temperature using TMS as an internal standard.
Due to the two isomers coexisting in the ligand L1/L1′-L5/L5′ and
low content of L1-L5, only the detailed 1H NMR analysis data for the
major products of L1′−L5′ are listed here. IR spectra were recorded on
a Perkin-Elmer System 2000 FT-IR spectrometer. Elemental analysis
was carried out using a Flash EA 1112 microanalyzer. Molecular
weights and molecular weight distribution of polyethylenes were
determined by a PL-GPC220 at 150 °C, with 1,2,4-trichlorobenzene as
the solvent. DSC traces and melting points of polyethylene were
obtained from the second scanning run on a Perkin-Elmer DSC-7 at a
heating rate of 10 °C/min.
no. of rflns collected
no. unique rflns [R(int)]
completeness to θ (%)
goodness of fit on F2
final R indices [I > 2σ(I)]
6586 (0.0410)
98.8 (θ = 27.49)
1.060
6584 (0.0442)
99.2 (θ = 27.51)
1.151
R1 = 0.0735
wR2 = 0.2040
R1 = 0.0899
wR2 = 0.2188
0.804 and −0.561
R1 = 0.0734
wR2 = 0.1756
R1 = 0.0863
wR2 = 0.1892
1.422 and −0.473
R indices (all data)
largest diff peak and hole (e Å−3
)
mL of 1,4-dioxane were added to a 500 mL three-necked jacketed
flask. The mixture was refluxed for 12 h under N2, and after cooling to
room temperature, the reaction mixture was washed with KF solution
(0.3 M, 100 mL × 3) and treated with 100 mL of 10% aqueous HCl.
The resulting mixture was neutralized by aqua ammonia. The organic
layer was dried over anhydrous Na2SO4 and concentrated in vacuo to
afford the crude product. The solvents were removed under reduced
pressure. The residue was purified by silica gel chromatography to
1
afford 3 (29.7 g, yield 95.4%) as a colorless oil. H NMR (500 MHz,
Synthesis of 2-Chloro-8-(4-methoxybenzyloxy)-5,6,7,8-tet-
rahydroquinoline (2). To a 500 mL three-necked jacketed flask were
added 2-chloro-5,6,7,8-tetrahydroquinolin-8-ol 1 (0.2 mol, 36.7 g) and
250 mL of CH2Cl2. When the mixture was cooled to 0 °C, NaH (0.4
mol, 16.0 g) was slowly added, and after stirring for 2 h, 4-
methoxybenzyl chloride (0.24 mol, 37.6 g) was added dropwise. The
resulting reaction mixture was stirred overnight; then 100 mL of water
was added to quench the reaction. The organic layer was separated and
washed with water (200 mL × 2). The crude product after removal of
the solvent under reduced pressure was purified by silica gel
chromatography to afford white solid 2, 44.3 g (73% yield). Mp:
CDCl3): δ 7.90 (d, J = 8.0 Hz, 1H, Py-H), 7.55 (d, 1H, J = 8.0 Hz, Py-
H), 7.38 (d, 2H, J = 8.4 Hz, Ar-H), 6.89 (d, 2H, J = 8.5 Hz, Ar-H),
4.84 (s, 2H, OCH2), 4.58 (t, 1H, J = 5.4 Hz, CH), 3.81 (s, 3H,
OCH3), 2.93 (m, 1H, CH2), 2.79 (m, 1H, CH2), 2.77 (s, 3H, CH3),
2.26 (m, 1H, CH2), 2.11 (m, 1H, CH2), 1.90 (m, 1H, CH2), 1.81 (m,
1H, CH2). 13C NMR (125 MHz; CDCl3; TMS): 200.3, 159.1, 155.4,
151.2, 137.8, 137.4, 131.0, 129.4, 120.5, 113.7, 74.4, 71.0, 55.3, 29.0,
28.7, 25.7, 17.7.
Synthesis of 2-Acetyl-6,7-dihydro-5H-quinolin-8-one (4). To
a Teflon-lined 316 L stainless steel autoclave (300 mL) was added 15.6
g (50 mmol) of 3, 290 μL (290 mg, 2.5 mmol, 5 mol %) of tert-butyl
nitrite (TBN), 0.57 g of 2,3-dichloro-5,6-dicyanobenzoquinone
(DDQ), and 60 mL of CH2ClCH2Cl. The autoclave was then closed
and charged with oxygen to 0.30 MPa. The autoclave was placed into
an oil bath, which was preheated to 90 °C. When the barometer
dropped to 0.20 MPa, it was charged with oxygen to 0.30 MPa again.
The procedure was repeated until the barometer was constant to
indicate that the reaction had finished. The autoclave was taken out
from the heating bath, cooled to room temperature, and carefully
depressurized. The mixture was diluted with CH2Cl2 and transferred
1
91−93 °C. H NMR (500 MHz, CDCl3): δ 7.40 (d, 1H, J = 8.0 Hz,
Py-H), 7.36 (d, 2H, J = 9.0 Hz, Ar-H), 7.18 (d, 1H, J = 8.5 Hz, Py-H),
6.89 (d, 2H, J = 7.0 Hz, Ar-H), 4,77 (m, 2H, OCH2), 4.52 (t, 1H, J =
3.5 Hz, CH), 3.81 (s, 3H, OCH3), 2.85 (m, 1H, CH2), 2.81 (m, 1H,
CH2), 2.69 (m, 2H, CH2), 2.23 (m, 1H, CH2), 2.01 (m, 1H, CH2),
1.78 (m, 2H, CH2).
Synthesis of 1-[8-(4-Methoxybenzyloxy)-5,6,7,8-tetrahydro-
quinolin-2-yl]ethanone (3). 2-Chloro-8-(4-methoxybenzyloxy)-
5,6,7,8-tetrahydroquinoline (2) (0.1 mol, 30.3 g), tributyl(1-ethox-
yvinyl)tin (0.11 mol, 40.0 g), Pd(dppf)Cl2 (3 mmol, 2.22 g), and 250
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Organometallics
Article
to a separation funnel, then washed with water (100 mL × 2) and
brine (100 mL) and dried over anhydrous Na2SO4. The solvents were
removed under reduced pressure. The residue was purified by silica gel
chromatography to afford a light yellow solid, 4 (6.3 g, yield 66.3%).
Mp: 122−123 °C. 1H NMR (500 MHz, CDCl3): δ 8.13 (d, 1H, J = 8.0
Hz, Py-H), 7.80 (d, 1H, J = 7.9 Hz, Py-H), 3.12 (t, 2H, J = 6.1 Hz,
CH2), 2.87 (t, 2H, J = 6.2 Hz, CH2), 2.82 (s, 3H, CH3), 2.25 (m, 2H,
CH2). 13C NMR (125 MHz, CDCl3; TMS): δ 199.9, 195.9, 152.9,
147.4, 144.3, 124.5, 39.9, 29.5, 25.7, 22.4. FT-IR (KBr, cm−1): 2941,
2876, 2360, 1707, 1689, 1580, 1458, 1403, 1355, 1296, 1256, 1215,
1187, 1122, 1086, 1032, 907, 898, 831, 713. Anal. Calcd for
C11H11NO2: C, 69.77, H, 6.00, N, 7.23. Found: C, 69.83, H, 5.86,
N, 7.40.
ethyl)-5,6-dihydroquinolin-8-amine (L3′). Using the same proce-
dure as for the synthesis of L1/L1′, L3/L3′ was obtained as a yellow
powder (0.30 g, 61%) with a crude molar ratio of L3:L3′ = 0.3:1
1
(detected by H NMR). Mp: 183−184 °C. FT-IR (KBr, cm−1): 3370
(νN−H), 2960, 2867, 2361, 1641, 1580, 1460, 1357, 1311, 1188, 1106,
1050, 1018, 799, 764, 696. Anal. Calcd for C35H45N3: C, 82.79, H,
8.93, N, 8.28. Found: C, 82.38, H, 8.78, N, 7.92. 13C NMR (100 MHz;
CDCl3; TMS): δ 166.7, 153.0, 148.5, 146.9, 140.0, 136.8, 135.9, 135.7,
135.4, 134.1, 126.5, 123.5, 123.0, 119.7, 98.3, 28.3, 28.0, 23.2, 22.9,
21.5, 17.3. 2-(1-(2,6-Diisopropylphenylimino)ethyl)-8-(2,6-diisopro-
1
pylphenylimino)-5,6,7-trihydroquinoline (L3): H NMR (400 MHz;
CDCl3; TMS): δ 8.42 (d, J = 7.7 Hz, Py-H), 7.69 (d, J = 7.8 Hz, Py-
H), 7.16 (t, Ar-H), 7.00 (t, J = 7.9 Hz, Ar-H), 3.03 (t, J = 6.4 Hz,
−CH2−), 2.82 (m, CH), 2.46 (t, J = 6.0 Hz, −CH2), 2.30 (s, −CH3),
2.0 (m, −CH2), 1.16 (m, CH3). N-(2,6-Diisopropylphenyl)-2-(1-(2,6-
diisopropylphenylimino)ethyl)-5,6-dihydroquinolin-8-amine (L3′):
8.23 (d, 1H, J = 7.7 Hz, Py-H), 7.61 (d, 1H, J = 7.7 Hz, Py-H),
7.16 (t, 2H, Ar-H), 7.11 (d, 3H, J = 7.4, Ar-H), 7.00 (t, 1H, J = 7.9 Hz,
Ar-H), 6.75 (s, 1H, −NH), 4.61 (t, 1H, J = 4.5 Hz, CH), 3.27 (m,
2H, −CH−), 2.92 (t, 2H, J = 7.7 Hz, −CH2−), 2.32 (t, 2H, J = 7.8 Hz,
−CH2−), 2.24 (s, 3H, NCCH3), 1.20 (d, 12 H, J = 6.4 Hz, CH3),
1.16 (m, 12H, CH3).
Synthesis of 2-(1-(2,4,6-Trimethylphenylimino)ethyl)-8-
(2,4,6-trimethylphenylimino)-5,6,7-trihydroquinoline (L4) and
N-(2,4,6-Trimethylphenyl)-2-(1-(2,4,6-trimethylphenylimino)-
ethyl)-5,6-dihydroquinolin-8-amine (L4′). Using the same proce-
dure as for the synthesis of L1/L1′, L4/L4′ was obtained as a yellow oil
(0.18 g, 43%) with a crude molar ratio of L4:L4′ = 0.15:1 (detected by
1H NMR). FT-IR (KBr, cm−1): 3366 (νN−H), 2922, 1640, 1572, 1477,
Synthesis of 2-(1-(2,6-Dimethylphenylimino)ethyl)-8-(2,6-
dimethylphenylimino)-5,6,7-trihydroquinoline (L1) and N-
(2,6-Dimethylphenyl)-2-(1-(2,6-dimethylphenylimino)ethyl)-
5,6-dihydroquinolin-8-amine (L1′). 2,6-Dimethylaniline (0.30 mg,
2.5 mmol) was added to a solution of 2-acetyl-6,7-dihydro-5H-
quinolin-8-one (4) (0.19 g, 1.0 mmol) with a catalytic amount of p-
toluenesulfonic acid (20.0 mg, 0.1 mmol) in 30 mL of n-butanol. The
mixture was stirred at reflux temperature for 8 h. The solvent was
evaporated under reduced pressure, and the residue was subsequently
purified by silica gel chromatography to afford 0.25 g (yield 63.3%) of
a yellow oil with crude molar ratio of L1:L1′ = 0.19:1 (detected by 1H
NMR). FT-IR (KBr, cm−1): 3362 (νN−H), 2932, 1644, 1593, 1469,
1446, 1363, 1315, 1199, 1110, 1094, 844, 764, 666. Anal. Calcd for
C27H29N3: C, 81.99; H, 7.39; N, 10.62. Found: C, 81.61; H, 7.46; N,
10.48. 13C NMR (100 MHz; CDCl3; TMS): δ 168.3, 154.2, 150.2,
150.0, 140.8, 138.8, 136.7, 135.5, 129.7, 129.3, 127.0, 126.8, 126.7,
124.3, 121.0, 99.7, 54.8, 29.3, 22.8, 19.7, 19.5, 19.3, 18.2, 17.9. 2-(1-
(2,6-Dimethylphenylimino)ethyl)-8-(2,6-dimethylphenylimino)-5,6,7-
1442, 1397, 1360, 1313, 1204, 1148, 1106, 1017, 852, 789, 671. Anal.
Calcd for C29H33N3: C, 82.23, H, 7.85, N, 9.92. Found: C, 82.12, H,
8.04, N, 9.77. 13C NMR (100 MHz; CDCl3; TMS): δ 168.5, 154.3,
150.0, 147.7, 139.1, 138, 2, 136.6, 136.1, 135.4, 133.4, 130.4, 129.9,
126.8, 120.9, 99.4, 29.3, 22.8, 22.3, 22.1, 19.6, 19.5, 19.3, 17.9. 2-(1-
(2,4,6-Trimethylphenylimino)ethyl)-8-(2,4,6-trimethylphenylimino)-
1
trihydroquinoline (L1): H NMR (400 MHz, CDCl3): δ 8.45 (d, J =
8.1 HZ, Py-H), 7.70 (d, J = 8.1 HZ, Py-H), 7.07 (m, Ar-H), 6.94 (t, J =
7.5 HZ, Ar-H), 3.02 (t, J = 6.1 HZ, −CH2−), 2.38 (m, −CH2−), 2.31
(s, CH3), 2.29 (s, CH3), 2.10 (s, CH3), 2.00 (m, CH2). N-(2,6-
Dimethylphenyl)-2-(1-(2,6-dimethylphenylimino)ethyl)-5,6-dihydro-
quinolin-8-amine (L1′): 8.27 (d, 1H, J = 7.8 HZ, Py-H), 7.61 (d, 1H, J
= 7.9 HZ, Py-H), 7.14 (d, 2H, J = 7.3 HZ, Ar-H), 7.07 (m, 3H, Ar-H),
6.94 (t, 1H, J = 7.5 HZ, Ar-H), 6.83 (s, 1H, −NH−), 4.63 (t, 1H, J =
4.6, −CH), 2.94 (t, 2H, J = 7.8 HZ, −CH2−), 2.36 (m, 2H,
−CH2−), 2.33 (s, 6H, CH3), 2.24 (s, 3H, NCCH3), 2.06 (s, 6H,
CH3).
1
5,6,7-trihydroquinoline (L4): H NMR (400 MHz; CDCl3; TMS): δ
8.43 (d, J = 8.1 Hz, Py-H), 7.68 (d, J = 8.1 Hz, Py-H), 6.88 (s, Ar-H),
3.02 (t, J = 7.2 Hz, −CH2), 2.41 (t, J = 6.6 Hz, −CH2), 2.31 (s,
−CH3), 2.28 (s, −CH3), 2.24 (s, −CH3), 2.06 (s, −CH3), 2.02 (m,
− C H 2 − ) . N - ( 2 , 4 , 6 - T r i m e t h y l p h e n y l ) - 2 - ( 1 - ( 2 , 4 , 6 -
trimethylphenylimino)ethyl)-5,6-dihydroquinolin-8-amine (L4′): 1H
NMR (400 MHz, CDCl3): 8.25 (d, 1H, J = 7.7 Hz, Py-H), 7.59 (d,
1H, J = 7.8 Hz, Py-H), 6.95 (s, 2H, Ar-H), 6.89 (s, 2H, Ar-H), 6.74 (s,
1H, −NH), 4.61 (t, J = 4.1 Hz, 1H, CH), 2.92 (t, J = 7.9 Hz, 2H,
−CH2−), 2.35 (t, 2H, J = 7.5 Hz, −CH2), 2.31 (s, 6H, −CH3), 2.28 (s,
6H, CH3), 2.22 (s, 3H, NCCH3), 2.06 (s, 6H, −CH3).
Synthesis of 2-(1-(2,6-Diethylphenylimino)ethyl)-8-(2,6-di-
ethylphenylimino)-5,6,7-trihydroquinoline (L2) and N-(2,6-
Diethylphenyl)-2-(1-(2,6-diethylphenylimino)ethyl)-5,6-dihy-
droquinolin-8-amine (L2′). Using the same procedure as for the
synthesis of L1/L1′, L2/L2′ was obtained as a yellow powder (0.24 g,
53%) with crude molar ratio of L2:L2′ = 0.33:1 (detected by 1H
NMR). Mp: 138−139 °C. FT-IR (KBr, cm−1): 3353 (νN−H), 2964,
2931, 2867, 2821, 2361, 2335, 1643, 1580, 1484, 1455, 1359, 1315,
1194, 1101, 1016, 875, 764, 698. Anal. Calcd for C31H37N3: C, 82.44,
H, 8.26, N, 9.30. Found: C, 82.44, H, 8.32, N, 9.15. 13C NMR (100
MHz; CDCl3; TMS): δ 166.8, 164.3, 153.1, 148.8, 148.1, 142.0, 138.9,
138.5, 135.6, 135.4, 134.3, 131.5, 131.4, 126.7, 126.2, 125.9, 123.4,
119.8, 98.4, 28.2, 25.1, 24.9, 21.7, 17.2, 15.4, 14.0. 13.7. 2-(1-(2,6-
Diethylphenylimino)ethyl)-8-(2,6-diethylphenylimino)-5,6,7-trihydro-
Synthesis of 2-(1-(2,6-Diethyl-4-methylphenylimino)ethyl)-
8-(2,6-diethyl-4-methylphenylimino)-5,6,7-drihydroquinoline
(L5) and N-(2,6-Diethyl-4-methylphenyl)-2-(1-(2,6-diethyl-4-
methylphenylimino)ethyl)-5,6-dihydroquinolin-8-amine (L5′).
Using the same procedure as for the synthesis of L1/L1′, L5/L5′ was
obtained as a yellow powder (0.22 g, 47%) with a crude molar ratio of
L5:L5′ = 0.23:1 (detected by 1H NMR). Mp: 98−99 °C. FT-IR (KBr,
cm−1): 3369 (νN−H), 2965, 2929, 2869, 2828, 1639, 1570, 1460, 1359,
1313, 1203, 1148, 1106, 1018, 883, 857, 793, 773, 702, 671. Anal.
Calcd for C33H41N3: C, 82.63, H, 8.61, N, 8.76. Found: C, 82.56, H,
8.47, N, 8.46. 13C NMR (100 MHz; CDCl3; TMS): 166.8, 152.9,
145.286, 141.545, 138.9, 135.5, 135.3, 133.9, 132.2, 131.2, 130.1,
127.2, 126.7, 126.6, 99.3, 24.7, 24.6, 24.5, 24.3, 21.4, 21.1, 20.9, 16.9,
15.2, 13.8. 2-(1-(2,6-Diethyl-4-methylphenylimino)ethyl)-8-(2,6-dieth-
yl-4-methylphenylimino)-5,6,7-drihydroquinoline (L5): 1H NMR
(400 MHz; CDCl3; TMS): 8.42 (d, J = 8.1 Hz, Py-H), 7.68 (d, J =
8.1 Hz, Py-H), 6.93 (s, Ar-H), 3.01 (t, J = 6.2 Hz, −CH2−), 2.45 (m,
2H, −CH2−), 2.40 (m, −CH2−), 2.35 (s, 3H, −CH3), 2.34 (s, 3H,
−CH3), 2.31 (m, CH2), 1.21 (t, J = 7.6 Hz, 6H, −CH3), 1.17 (m,
CH3). N-(2,6-Diethyl-4-methylphenyl)-2-(1-(2,6-diethyl-4-
methylphenylimino)ethyl)-5,6-dihydroquinolin-8-amine (L5′): 8.23
(d, 1H, J = 7.8 Hz, Py-H), 7.59 (d, 1H, J = 7.8 Hz, Py-H), 6.98 (s,
2H, Ar-H), 6.93 (s, 2H, Ar-H), 6.76 (s, 1H, −NH−), 4.60 (t, J = 4.5
Hz, 1H, CH), 2.91 (t, J = 7.7 Hz, 2H, −CH2−), 2.64 (m, 4H,
1
quinoline (L2): H NMR (400 MHz; CDCl3): δ 8.42 (d, J = 8.1 Hz,
Py-H), 7.68 (d, J = 8.1 Hz, Py-H), 7.11 (d, J = 7.4, Ar-H), 7.00 (t, J =
7.9 Hz, Ar-H), 3.02 (t, J = 6.2, −CH2−), 2.52 (m, −CH2−), 2.35 (m,
CH2), 2.29 (s, CH3), 1.98 (m, CH2), 1.18 (m, CH3), 1.13 (m, CH3).
N-(2,6-Diethylphenyl)-2-(1-(2,6-diethylphenylimino)ethyl)-5,6-dihy-
droquinolin-8-amine (L2′): 8.24 (d, 1H, J = 7.8 Hz, Py-H), 7.60 (d,
1H, J = 7.8 Hz, Py-H), 7.16 (s, 3H, Ar-H), 7.11 (d, 2H, J = 7.4, Ar-H),
7.00 (t, 1H, J = 7.9 Hz, Ar-H), 6.84 (s, 1H, −NH), 4.60 (t, J = 4.6 Hz,
1H, CH), 2.91 (t, 2H, J = 7.7 Hz, −CH2−), 2.67 (m, 4H, −CH2−),
2.44 (m, 4H, −CH2−), 2.33 (m, 2H, −CH2−), 2.23 (s, 3H, N
CCH3), 1.21 (t, 6H, J = 7.9 Hz, −CH3), 1.14 (t, 6H, J = 7.4 Hz,
−CH3).
Synthesis of 2-(1-(2,6-Diisopropylphenylimino)ethyl)-8-(2,6-
diisopropylphenylimino)-5,6,7-trihydroquinoline (L3) and N-
(2,6-Diisopropylphenyl)-2-(1-(2,6-diisopropylphenylimino)-
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Organometallics
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−CH2), 2.40 (m, 2H, −CH2−), 2.35 (s, 3H, −CH3), 2.34 (s, 3H,
−CH3), 2.31 (m, 4H, CH2), 1.21 (t, 6H, J = 7.6 Hz, CH3), 1.14 (t, 6H,
J = 7.5 Hz, CH3).
Procedure for Ethylene Polymerization. Ethylene polymer-
ization was carried out in a stainless steel autoclave (250 mL capacity)
equipped with an ethylene pressure control system, a mechanical
stirrer, and a temperature controller. When the desired reaction
temperature was reached, under ethylene atmosphere, toluene, the
desired amount of cocatalyst, and a toluene solution of the catalytic
precursor (the total volume was 100 mL) were injected into the
reactor using syringes in this order, and then the ethylene pressure was
increased to 10 atm and maintained at this level by constant feeding of
ethylene. After the desired reaction period, the reactor was cooled with
an ice−water bath and the excess ethylene was vented. The resultant
mixture was poured into 10% HCl−ethanol solution, and the polymer
was collected and washed with ethanol several times and dried under
vacuum to constant weight.
X-ray Crystallographic Studies. Single crystals of the iron
complexes Fe1 and Fe2 suitable for X-ray diffraction analysis were
obtained by slow diffusion of diethyl ether into their dichloromethane
solutions under nitrogen atmosphere at room temperature, respec-
tively. Data collection for Fe1 was carried out on a Rigaku MM007-HF
Saturn 724 + CCD diffractometer with confocal mirror monochro-
mated Mo Kα radiation (λ = 0.71073 Å), while that for Fe2 was
carried out on a Rigaku Saturn 724 + CCD diffractometer with
graphite-monochromated Mo Kα radiation (λ = 0.71073 Å). Cell
parameters were obtained by global refinement of the positions of all
collected reflections. Intensities were corrected for Lorentz and
polarization effects and empirical absorption. The structures were
solved by direct methods and refined by full-matrix least-squares on F2.
All hydrogen atoms were placed in calculated positions. Structure
solution and refinement were performed by using the SHELXL-97
package.31 Details of the X-ray structure determinations and
refinements are provided in Table 4.
Synthesis of 2-(1-(2,6-Dimethylphenylimino)ethyl)-8-(2,6-
dimethylphenylimino)-5,6,7-trihydroquinoline iron(II) dichlor-
ide (Fe1). The ligand L1/L1′ (0.15 g, 0.38 mmol) and the metal salt
FeCl2·4H2O (0.070 g, 0.35 mmol) were added together in a Schlenk
tube, 5 mL of degassed freshly distilled ethanol was injected into this
tube, and the mixture was rapidly stirred at room temperature for 10 h.
Then Et2O was added to the reaction to precipitate the complex Fe1.
After filtering, the precipitate was washed with diethyl ether (3 × 5
mL) and dried under vacuum to give the product as a purple powder
1
(0.16 g, 76.2%). H NMR (CD2Cl2, 600 MHz): 83.1 (s, 1H, Py Hm),
24.0 (s, 1H, Py-Hp), 17.6 (s, 2H, Ar-Hm), 16.9 (s, 2H, Ar-Hm), 14.2 (s,
3H, CH3), 13.8 (s, 3H, CH3), 10.4 (s, 3H, CH3), 7.1 (s, 3H, CH3), 3.7
(s, 2H, CH2), 1.3 (s, 2H, CH2), −10.0 (s, 1H, Ar−Hp), −10.6 (s, 1H,
Ar−Hp), −14.4 (s, 3H, NCCH3), −34.9 (s, 2H, NCCH2). FT-IR
(KBr, cm−1): 2951, 2914, 2324, 1621, 1586, 1468, 1428, 1369, 1264,
1242, 1195, 1092, 1038, 923, 835, 766. Anal. Calcd for
C27H29Cl2FeN3: C, 62.09, H, 5.60, N, 8.05. Found: C, 62.13, H,
5.47, N, 7.67.
Synthesis of 2-(1-(2,6-Diethylphenylimino)ethyl)-8-(2,6-di-
ethylphenylimino)-5,6,7-trihydroquinolineiron(II) Dichloride
(Fe2). By the above procedure, Fe2 was isolated as a blue powder
1
in 71.4% yield. H NMR (CDCl3, 600 MHz): 77.6 (s, 1H, Py-Hm),
42.3 (s, 1H, Py-Hp), 21.7 (s, 2H, CH2), 16.1 (s, 2H, Ar-Hm), 15.1 (s,
2H, Ar-Hm), 9.3 (s, 2H, CH2), 8.5 (s, 2H, CH2), 6.0 (s, 2H, CH2), 4.2
(s, 2H, CH2), 2.1 (s, 3H, CH3), 1.5 (s, 2H, CH2), 1.3 (s, 3H, CH3),
−3.1, −3.2 (s, 6H, CH3), −10.1 (s, 1H, Ar-Hp), −10.7 (s, 1H, Ar-Hp),
−22.8 (s, 3H, NCCH3), −45.1 (s, 2H, NCCH2). FT-IR (KBr,
cm−1): 2967, 2940, 2874, 2359, 1608, 1578, 1551, 1446, 1421, 1372,
1270, 1246, 1188, 1111, 1039, 867, 808, 777. Anal. Calcd for
C31H37Cl2FeN3: C, 64.37, H, 6.45, N, 7.26. Found: C, 64.22, H, 6.24,
N, 7.02.
Synthesis of 2-(1-(2,6-Diisopropylphenylimino)ethyl)-8-(2,6-
diisopropylphenylimino)-5,6,7-trihydroquinolineiron(II) Di-
chloride (Fe3). By the above procedure, Fe3 was isolated as a blue
powder in 59.1% yield. 1H NMR (CDCl3, 600 MHz): 86.8 (s, 1H, Py
Hm), 79.9 (s, 1H, Py-Hp), 45.5 (s, 2H, CH2), 15.3 (s, 2H, Ar-Hm), 14.5
(s, 2H, Ar-Hm), 6.2 (s, 2H, CH2), 5.4 (s, 1H, CH), 1.2 (s, 1H, CH),
1.1, (s, 6H, CH3), 0.9 (s, 6H, CH3), −4.0 (s, 1H, CH), −5.0 (s, 1H,
CH), −5.7 (s, 6H, CH3), −5.9 (s, 6H, CH3), −10.5 (s, 1H, Ar-Hp),
10.8 (s, 1H, Ar-Hp), −21.3 (d, 3H, NCCH3), −39.0 (s, 2H, N
CCH2). FT-IR (KBr, cm−1): 2964, 1864, 2360, 2341, 1602, 1577,
1554, 1461, 1441, 1364, 1324, 1270, 1247, 1186, 1103, 1042, 924, 831,
801, 777. Anal. Calcd for C35H45Cl2FeN3: C, 66.25, H, 7.15, N, 6.62.
Found: C, 66.24, H, 7.02, N, 6.48.
ASSOCIATED CONTENT
* Supporting Information
■
S
CIF file giving X-ray crystal structural data of of Fe1 and Fe2.
This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
■
*Tel: +86-10-62557955. Fax: +86-10-62618239. E-mail:
whsun@iccas.ac.cn (W.H.S.). Tel: +44 (0)1603 593137. Fax:
+44 (0)1603 592003. E-mail: carl.redshaw@uea.ac.uk (C.R.).
Notes
The authors declare no competing financial interest.
Synthesis of 2-(1-(2,4,6-Trimethylphenylimino)ethyl)-8-
(2,4,6-trimethylphenylimino)-5,6,7-trihydroquinolineiron(II)
Dichloride (Fe4). By the above procedure, Fe4 was isolated as a
ACKNOWLEDGMENTS
■
1
green powder in 55.5% yield. H NMR (CD2Cl2, 600 MHz): 82.7 (s,
This work was supported by MOST 863 Program No.
2009AA034601. C.R. wishes to thank the EPSRC for an
overseas travel grant (EP/H031855/1).
1H, Py-Hm), 28.0 (s, 1H, Py-Hp), 21.4 (s, 2H, Ar-Hm), 20.9 (s, 2H, Ar-
Hm), 16.4 (s, 3H, CH3), 15.3 (s, 3H, CH3), 14.3 (s, 3H, CH3), 14.0 (s,
3H, CH3), 11.8 (s, 3H, CH3), 6.9 (s, 3H, CH3), 3.8 (s, 2H, CH2), 1.3
(s, 2H, CH2), −16.4 (s, 3H, NCCH3), −37.6 (s, 2H, NCCH2).
FT-IR (KBr, cm−1): 2948, 2913, 1359, 1618, 1581, 1479, 1416, 1368,
1278, 1230, 1153, 1036, 906, 862, 829, 761. Anal. Calcd for
C29H33Cl2FeN3: C, 63.29, H, 6.04, N, 7.64. Found: C, 63.11, H,
7.16, N, 6.48.
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