Probing the characteristics of mono- or bimetallic (iron or cobalt) complexes bearing 2,4-bis(6-iminopyridin-2-yl)-3 H-benzazepines: Synthesis, characterization, and ethylene reactivity

Article abstract of DOI:10.1021/om301086p

A series of 2,4-bis(6-iminopyridin-2-yl)-3H-benzazepines and the mono- or bimetallic (Fe²⁺ or Co²⁺) complexes thereof were synthesized and characterized. All title complexes, when activated by MAO or MMAO, exhibited high activities of up to 4.0 × 10⁷ g (mol of Fe)^-1 h^-1 for ethylene oligomerization and polymerization. The iron(II) precatalysts generally showed higher activities and produced a wider distribution of products (including oligomers and polyethylene) than did their corresponding cobalt(II) analogues. The bimetallic precatalysts exhibited higher (almost twice) activities in comparison to their monometallic analogues. The distribution of the resulting oligomers closely resembled the Schultz-Flory rule.

Full text of DOI:10.1021/om301086p

Article
pubs.acs.org/Organometallics
Probing the Characteristics of Mono- or Bimetallic (Iron or Cobalt)
Complexes Bearing 2,4-Bis(6-iminopyridin-2-yl)‑3H‑benzazepines:
Synthesis, Characterization, and Ethylene Reactivity
Wen-Hua Sun,*,†,‡ Qifeng Xing,† Jiangang Yu,† Elena Novikova,† Weizhen Zhao,† Xiubo Tang,†
Tongling Liang,† and Carl Redshaw*,§
†Key laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, People’s Republic of China
‡State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of
Sciences, Lanzhou 730000, People’s Republic of China
§Department of Chemistry, University of Hull, Hull HU6 7RX, U.K.
S
* Supporting Information
ABSTRACT: A series of 2,4-bis(6-iminopyridin-2-yl)-3H-benzazepines
and the mono- or bimetallic (Fe2+ or Co2+) complexes thereof were
synthesized and characterized. All title complexes, when activated by
MAO or MMAO, exhibited high activities of up to 4.0 × 107 g (mol of
Fe)−1 h−1 for ethylene oligomerization and polymerization. The iron(II)
precatalysts generally showed higher activities and produced a wider
distribution of products (including oligomers and polyethylene) than did
their corresponding cobalt(II) analogues. The bimetallic precatalysts
exhibited higher (almost twice) activities in comparison to their
monometallic analogues. The distribution of the resulting oligomers
closely resembled the Schultz−Flory rule.
utilizes solely sp2 N ligands and contains both N∧N∧N and
INTRODUCTION
■
N∧N coordination environments. The centrally fused ring is
Binuclear complexes in catalysis are of interest due to potential
constructed from the 3H-benzazepine motif instead of the
synergistic effects.1 Some attention has been paid to bimetallic
benzodiazepine within 2,4-bis(6-ketiminopyridin-2-yl)-1H-1,5-
complex precatalysts for ethylene reactivity,2 and recently this
benzodiazepines, and thus the 2,4-bis(6-acetylpyridin-2-yl)-3H-
was discussed in a review article.3 For reported group IVB
benzazepine ligand set was successfully prepared. The resultant
bimetallic complexes in olefin polymerization, their use has
mono- and bimetallic iron(II)/cobalt(II) complexes, upon
commonly produced polymers of lower molecular weight and
activation with MAO, revealed high activities toward ethylene
broader polydispersity than are observed for their monometallic
oligomerization and polymerization. Herein, the synthesis and
analogues.2a,4 Other approaches have involved the combination
characterization of the organic compounds and their metal
of early and late transition metals for dual functions during
complexes are reported, and the catalytic behavior of the metal
ethylene oligomerization and copolymerization.5 Probably due
complexes in ethylene oligomerization and polymerization is
to the relative stabilities of the bimetallic complexes, there are
discussed.
more examples of late-transition-metal systems,2h,j,l,6 partic-
ularly of nickel and palladium binuclear complexes,2f,i,l,6c−g,7
RESULTS AND DISCUSSION
Synthesis and Characterization of the Organic
Compounds and Their Metal (Iron or Cobalt) Com-
■
which tend to produce branched polyethylenes. In contrast,
iron and cobalt complex precatalysts commonly polymerize
ethylene, resulting in highly linear products,8 including high-
density polyethylene and polyethylene waxes.9 A limited
plexes. The reaction of 2,6-diacetylpyridine and 2-fluoroben-
zenamine resulted in the formation of a benzazepinyl ring,11
number of binuclear iron or cobalt complex precatalysts have
been developed,2h,j,k and model ligand sets using benzodiaze-
which was exploited for connecting two acetylpyridines to
afford a novel 2,4-bis(6-acetylpyridin-2-yl)-3H-benzazepine (1).
pine to fuse the bis(imino)pyridyl and mono(imino)pyridyl
frameworks provided highly efficient precatalysts,2j,k in which
This new ligand set was fully characterized, and its structure
was confirmed by single-crystal X-ray diffraction. With use of
the two acetyl groups of 1, further reaction with two anilines
the sp3 N of the benzodiazepine was not coordinated to the
metal center. However, we recently developed a number of
bidentate N∧N ligands for iron and cobalt complexes, which
revealed good activity for ethylene polymerization at elevated
Received: November 13, 2012
Published: April 4, 2013
pressure of ethylene.10 Subsequently, our new target model
© 2013 American Chemical Society
2309
dx.doi.org/10.1021/om301086p | Organometallics 2013, 32, 2309−2318

Organometallics
Article
Scheme 1. Synthetic Procedure
afforded the corresponding compounds 2,4-bis(6-(1-
aryliminoethyl)pyridin-2-yl)-3H-benzazepines (Ln; Scheme
1), all of which were fully characterized by elemental analysis
1
and H and 13C NMR and FT-IR spectroscopy.
With multiple coordination sites potentially available for
hosting two metal ions, these compounds (Ln) were reacted
with MCl2 (M = Fe, Co), and depending on the molar ratio of
metal chlorides employed, the stepwise formation of the
corresponding monometallic (M1-n) and bimetallic complexes
(M2-n) (Scheme 1) proved possible. In their IR spectra, the
νCN stretching frequencies upon coordination shifted to lower
values (1620−1632 cm−1) in comparison to those of the free
ligands (1639−1650 cm−1). Notably, there are two peaks
assigned to the νCN stretching frequencies for each
monometallic complex, due to the presence of the two different
CN groups: viz., one coordinated to the metal and the other
free. In contrast, only one peak is assigned to the νCN
stretching frequency when both CN groups are coordinated
to ions of the same metal. The metal complexes of both the
monometallic LMCl2 (M1-n) and bimetallic L(MCl2)2 (M2-n)
forms were consistent with their elemental analytic data. In
addition, the unambiguous structure of a representative
monocobalt complex, Co1-1, was confirmed by single-crystal
X-ray diffraction.
X-ray Crystallographic Studies. Single crystals of 2,4-
bis(6-acetylpyridin-2-yl)-3H-benzazepine and 2,4-bis(6-(1-(2,6-
diisopropylphenylimino)ethyl)pyridin-2-yl)-3H-benzazepine
(L3) were grown from their respective dichloromethane
solutions, while single crystals of the cobalt complex Co1-1
were obtained by laying n-pentane onto its tetrahydrofuran
(THF) solution at room temperature. The molecular structures
were confirmed by single-crystal X-ray diffraction and are
shown in Figure 1 (2,4-bis(6-acetylpyridin-2-yl)-3H-benzaze-
pine (1)), Figure 2 (2,4-bis(6-(1-(2,6-diisopropylphenylimino)-
ethyl)pyridin-2-yl)-3H-benzazepine (L3)) and Figure 3 (the
monocobalt complex Co1-1); selected bond lengths and angles
are given in Table 1.
Figure 1. ORTEP drawing of 2,4-bis(6-acetylpyridin-2-yl)-3H-
benzazepine (1). Thermal ellipsoids are shown at the 30% probability
level. Hydrogen atoms have been omitted for clarity.
1.296(3) (L3), and 1.291(7) Å (Co1-1), indicative of
double-bond character. As shown in Figure 3, the monocobalt
complex Co1-1 possesses a pentacoordinate pseudo-square-
pyramidal geometry at cobalt constructed from the three
nitrogen atoms N(1), N(2), and N(4) and two chlorine atoms;
the chlorides Cl(1) and Cl(2) are bonded as observed for the
bis(imino)pyridylmetal chlorides.12 The cobalt atom is almost
planar to the chelating plane (N1−N2−N4) with a ca. 0.043 Å
̂
∧
∧
̂
deviation, which is much less than for other N N N tridentate
iron/cobalt complexes.13 The chlorides (Cl1 and Cl2) are
located in trans positions relative to the chelate plane. The
chelate plane and the iminophenyl plane (C18−C23) are
nearly perpendicular with a dihedral angle of ca. 88.40°. Thus,
the substituent R1 will protect the active site efficiently and this
is also why the steric bulk of R1 affected the catalytic
performance (vide infra). However, the phenyl plane (C1−
C6) from the other arm of the pyridine was not as
perpendicular with the chelated plane (with a dihedral angle
of ca. 55.37°). This dramatically decreases the protecting effect
and thus leads to the production of oligomers rather than
polymeric products. The availability of N3 and N5 for
coordination of another metal can also be clearly seen from
As shown in Figures 1−3, the seven-membered rings are each
constructed by C8, C9, C14−C17, and N2, individually. The
C(15)−C(16) bonds have typical double-bond character with
lengths of 1.334(3) (1), 1.322(3) (L3), and 1.378(8) Å (Co1-
1), while the C(16)−C(17) bond lengths are typical of single
bonds at 1.498(3) (1), 1.494(3) (L3), and 1.507(8) Å (Co1-
1). The bond lengths of N(2)−C(8) are 1.296(2) (1),
2310
dx.doi.org/10.1021/om301086p | Organometallics 2013, 32, 2309−2318

Organometallics
Article
Table 1. Selected Bond Lengths and Angles for Compounds
1, L3, and Co1-1
1
L3
Co1-1
Bond Lengths (Å)
N(2)−C(8)
C(15)−C(16)
C(16)−C(17)
O(1)−C(2)
O(2)−C(23)
N(4)−C(2)
N(5)−C(23)
Co−N(1)
1.296(2)
1.334(3)
1.498(3)
1.213(2)
1.221(3)
1.296(3)
1.322(3)
1.494(3)
1.291(7)
1.378(8)
1.507(8)
1.271(3)
1.268(2)
1.261(8)
1.233(8)
1.967(5)
2.172(5)
2.165(5)
Co−N(2)
Co−N(4)
Bond Angles (deg)
C(3)−N(1)−C(7)
C(8)−N(2)−C(9)
N(1)−C(3)−C(2)
N(1)−C(7)−C(8)
O(1)−C(2)−C(3)
O(2)−C(23)−C(22)
C(23)−N(5)−C(33)
C(2)−N(4)−C(25)
N(1)−Co−N(4)
117.31(15)
122.02(17)
116.89(17)
115.91(16)
120.1(2)
118.28(19)
123.3(5)
122.2(5)
114.8(6)
113.2(5)
122.0(2)
115.88(19)
116.21(18)
119.4(2)
Figure 2. O R T E P d r a w i n g o f 2 , 4 - b i s ( 6 -( 1 - ( 2 , 6 -
diisopropylphenylimino)ethyl)pyridin-2-yl)-3H-benzazepine (L3).
Thermal ellipsoids are shown at the 30% probability level. Hydrogen
atoms have been omitted for clarity.
120.44(17)
122.1(2)
121.8(6)
120.5(5)
77.67(19)
78.05(19)
155.65(18)
128.22(7)
N(1)−Co−N(2)
N(4)−Co−N(2)
Cl(1)−Co−Cl(2)
(catalytic results for the dicobalt complexes), and 5
(comparison of the catalytic behavior between monocobalt
complexes and dicobalt complexes).
Ethylene Oligomerization/Polymerization Promoted
by Iron Complexes. MAO and MMAO were initially used to
activate complex Fe2-1 for ethylene reactivity at room
temperature (entries 1 and 2, Table 2). The catalytic system
activated by MMAO showed much higher activities for ethylene
oligometization and polymerization with higher K values than
when MAO was employed. Therefore, further catalytic studies
were conducted via activation with MMAO and are given in
Table 2.
Effects of Al/Fe Molar Ratio and Reaction Temper-
ature on Catalyst Behavior. In the catalytic system Fe2-1/
MMAO, the molar radio of Al/Fe plays a significant role in the
activity for ethylene oligomerization/polymerization. When the
Al/Fe molar ratio was increased over the range 500−2000
(entries 2−5, Table 2), the best activity was observed with the
optimized Al/Fe molar ratio of 1000. However, the K value was
not affected as much and fluctuated near a value of 0.51. With
the Al/Fe molar ratio fixed at 1000, the reaction temperature
was varied from 0 to 80 °C (entries 2 and 6−9, Table 2).
Similar to the case for other iron catalytic systems, the activity
for ethylene oligomerization/polymerization decreased on
increasing the reaction temperature. This is because of the
instability of the active species (decomposition), together with
low ethylene solubility in the reaction solution at higher
temperature.15 Thus, the highest activity, as high as 2.36 × 106
g (mol of Fe)−1 h−1 for ethylene oligomerization and 0.41 ×
106 g (mol of Fe)−1 h−1 for ethylene polymerization, was
obtained at the reaction temperature of 0 °C (entry 6, Table 2).
Moreover, a higher reaction temperature always led to a higher
percentage of butene and a lower K value. This indicated that
chain termination is facile at elevated temperatures.16 Notably,
Figure 3. ORTEP drawing of the monocobalt complex Co1-1.
Thermal ellipsoids are shown at the 30% probability level. Hydrogen
atoms have been omitted for clarity.
the molecular structure. Despite our ability to obtain crystalline
products, these compounds proved not to be suitable for single-
crystal X-ray diffraction.
Catalytic Behavior toward Ethylene. The mono-/
bimetallic Fe/Co complexes were systematically investigated
for ethylene oligo-/polymerization. MAO and MMAO were
evaluated as suitable cocatalysts to activate the title complexes
for ethylene oligomerization/polymerization reactions. The
results are summarized in Tables 2 (catalytic results for the
diiron complexes), 3 (comparison of the catalytic behavior
between monoiron complexes and diiron complexes), 4
2311
dx.doi.org/10.1021/om301086p | Organometallics 2013, 32, 2309−2318

Organometallics
Article
a
Table 2. Catalytic Results of Ethylene Oligomerization/Polymerization
b
oligomer
c
d
d
d
d
e
c
f
entry
t (min)
Al/Fe
T (°C)
activity
∑C4/∑C
∑C6/∑C
∑C8/∑C
α-C/∑C
K
polymer activity
polymer (wt %)
g
1
30
30
30
30
30
30
30
30
30
5
1000
1000
500
20
20
20
20
20
0
1.06
1.95
0.95
1.58
1.34
2.36
1.32
0.81
0.46
5.41
4.33
3.60
3.43
1.78
1.19
60.6
55.7
58.8
55.1
54.8
49.8
60.1
61.0
61.7
56
21.1
24.8
22.9
24.5
24.7
23.8
22.1
21.0
20.8
19.9
21.1
21.6
22.8
24.1
24.7
8.23
10.5
9.82
10.8
11.1
11.6
10.5
10.1
10.0
10
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
0.47
0.51
0.52
0.51
0.50
0.56
0.52
0.50
0.48
0.61
0.59
0.60
0.56
0.57
0.58
0.13
0.44
0.31
0.37
0.34
0.41
0.31
0.25
0.12
1.49
1.14
0.89
0.81
0.41
10.9
18.4
24.6
19.0
20.2
14.8
19.0
23.6
20.7
21.6
20.8
19.8
19.1
18.7
2
3
4
1500
2000
1000
1000
1000
1000
1000
1000
1000
1000
1000
1000
5
6
7
40
60
80
0
8
9
10
11
12
13
14
15
10
15
20
40
60
0
54.9
52
10.9
11.1
11.4
11.9
12.7
0
0
51.1
48
0
0
47
0.27
18.5
a
b
c
General conditions: cat., 1.0 μmol of Fe2-1; ethylene pressure, 1 atm; solvent, toluene (30 mL); cocatalyst, MMAO. Determined by GC. In units
d
e
of 106 g (mol of Fe)−1 h−1. ∑C4, ∑C6, ∑C8, and ∑C denote the total amounts of butene, hexene, octene, and oligomers in mol %, respectively. K
= (rate of propagation)/[(rate of propagation) + (rate of chain transfer)] = (mol of C14)/(mol of C12).14 The percentage of polyethylene waxes.
f
g
The cocatalyst is MAO.
a
Table 3. Catalytic Results Based on Various Iron Complexes
b
oligomer
d
f
g
P
∑C4/∑C (mol
∑C6/
d
∑C8/
d
α-C/
d
polymer
c
PE (wt
Tm
M /
wh
c
e
h
entry
cat.
(atm) activity
%)
∑C
∑C
∑C
K
activity
%)
(°C)
Mw
Mn
1
Fe1-1
Fe2-1
Fe1-2
Fe2-2
Fe1-3
Fe2-3
Fe1-4
Fe2-4
Fe1-5
Fe2-5
Fe1-1
Fe2-1
Fe1-2
Fe2-2
Fe1-3
Fe2-3
Fe1-4
Fe2-4
Fe1-5
Fe2-5
1
1
1.51
2.36
1.41
2.12
1.05
2.10
1.61
2.40
1.55
2.32
51.2
49.8
50.1
49.1
50.5
52.7
55.8
51.4
58.2
52.5
57.8
51.5
51.2
47.1
53.8
46.7
56.3
54.1
61.5
55.3
25.0
23.8
23.1
24.1
22.9
19.7
18.7
19.5
15.6
17.7
23.8
24.8
25.5
27.9
24.0
25.6
15.4
16.6
15.2
20.6
10.6
11.6
11.3
11.7
11.2
9.98
10.3
12.2
9.51
10.6
9.35
10.8
13.4
15.1
11.9
14.9
11.1
11.9
8.23
15.8
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
0.56
0.59
0.54
0.57
0.53
0.56
0.60
0.63
0.58
0.61
0.53
0.56
0.51
0.52
0.49
0.49
0.56
0.60
0.55
0.58
0.33
0.41
0.28
0.38
0.19
0.47
0.36
0.49
0.31
0.46
3.5
18.0
14.8
16.7
15.1
15.3
18.4
18.4
16.9
16.9
16.5
10.5
9.9
2
3
1
4
1
5
1
6
1
7
1
8
1
9
1
10
11
12
13
14
15
16
17
18
19
20
1
10
10
10
10
10
10
10
10
10
10
29.8
69.0
73.3
898
3145
1.47
1.74
4.3
34.1
27.1
33.9
23.1
29.8
31.1
35.1
30.1
34.5
3.77
4.00
5.85
3.31
4.90
4.70
4.97
2.79
3.33
12.9
14.7
12.5
14.1
13.1
12.4
8.5
129.3
130.0
130.2
126.3
124.4
124.6
80.9
17700
21800
14198
22554
1916
6.3
2.97
8.9
1.66
1.83
2.07
1.48
14766
1365
8.8
92.3
7417
a
General conditions: 2.0 μmol Fe; solvent, toluene (30 mL for 1 atm and 100 mL for 10 atm); cocatalyst, MMAO (Al/Fe = 1000); reaction
b
c
d
temperature, 0 °C; reaction time, 30 min. Determined by GC. In units of 106 g (mol of Fe)−1 h−1. ∑C4, ∑C6, ∑C8, and ∑C denote the total
e
amounts of butene, hexene, octene, and oligomers in mol %, respectively. K = (rate of propagation)/[(rate of propagation) + (rate of chain
transfer)] = (mol of C14)/(mol of C12).14 Percentage of polyethylene. Determined by DSC. Determined by GPC.
f
g
h
all complex precatalysts produced α-olefins with a high
selectivity of over 99% (α-C/∑C).
produced. This indicates that the active catalytic species were
deactivated in the first 30 min. However, the butene content
and the K value were not as affected and proved to be quite
stable over time.
Comparison of Catalytic Behavior between the Iron
Complex Precatalysts Fe1-n and Fe2-n (n = 1−5). The
catalytic activities of the diiron complexes are significantly
affected by the bulkiness of the substituents at the imino-N aryl
ring as well as by the coordination number of the metal. The
Lifetime of the Catalytic System. The diiron complexes
were found to deactivate over a relatively short time even at low
temperature. As an example, the relationship between time and
activity was studied for Fe2-1/MMAO, and the activity was
found to be almost reduced by half when lengthening the
reaction time from 5 to 30 min (entries 6 and 10, Table 2).
After 30 min, very few oligomers and/or polymers were
2312
dx.doi.org/10.1021/om301086p | Organometallics 2013, 32, 2309−2318

Organometallics
Article
catalytic tests of Fe1-n and Fe2-n (n = 1−5) were conducted at
both 1 and 10 atm, and the results are given in Table 3. When
the steric bulk of the substituent R1 was increased, the activities
decreased slightly for both the diiron and the monoiron
complexes at 1 atm (entries 1−6, Table 3) and 10 atm (entries
11−16, Table 3). This is probably due to the bulky substituent
inhibiting the insertion of the monomer.17 Moreover, the
addition of a methyl group at the para position of the N-aryl
ring also leads to a slight increase of the catalytic activity at both
1 atm (entries 1−4 and 7−10, Table 3) and 10 atm (entries
11−14 and 17−20, Table 3).
Notably, the diiron complexes are always much more active
for ethylene oligomerization/polymerization with a higher K
value than the corresponding monoiron complexes. An example
of a comparison of the product distribution is illustrated in
Figure 4. It clearly shows that the diiron complexes tend to
Ethylene Oligomerization Promoted by Cobalt Com-
plexes. In contrast to the iron catalysts, the cobalt complexes
exhibited much higher activity for ethylene oligomerization/
polymerization in the presence of MAO than in the presence of
MMAO (entries 1 and 2, Table 4); however, the product
distribution (C4/∑C, C6/∑C, C8/∑C, and α-C/∑C) and K
values were quite similar between the catalytic systems Co2-1/
MAO (entry 2, Table 4) and Co2-1/MMAO (entry 1, Table
4). Thus, further catalytic studies were conducted via activation
with MAO, as given in Table 4.
Using MAO as the cocatalyst, the precatalyst Co2-1 showed
trends with regard to the reaction temperature, time, and Al/
Co molar ratio (entries 2−15 in Table 4) similar to those of the
iron complexes. The optimized reaction conditions were found
to be 20 °C and an Al/Co molar ratio of 1500 (entry 4, Table
4), for which the activity and K value were 1.19 × 106 g (mol of
Co)−1 h−1 and 0.67, respectively. However, different from the
iron complexes, which are active for both ethylene polymer-
ization and oligomerization, the cobalt complexes only
exhibited activity for ethylene oligomerization and no polymer
was detected. Moreover, the selectivity for butene of the cobalt
complexes (about 80%) was much higher than that of the iron
complexes (about 50%). In all cases, there was a tendency for
the iron complexes to create longer-chain products than the
cobalt complexes.
The relationship between the catalytic performance of Co2-
1/MAO and the reaction time was also conducted, and the
results are shown in Table 4 (entries 6 and 10−15). The
activity was maintained at a relatively high value (about 1.5 ×
106 g (mol of Co)−1 h−1) over the first 20 min (entries 10−13),
after which the activity declined linearly (entries 6, 14, and 15).
Comparison of the Catalytic Behavior between Co1-n
and Co2-n (n = 1−5). The catalytic activities of mono-/
dicobalt complexes were also greatly affected by the sterics of
the ligand set (Table 5). Interestingly, the steric bulk effect of
the ligand on the activity of the monocobalt complexes versus
the dicobalt complexes produced diametrically opposite trends.
At both 1 and 10 atm, the activity declined slowly on increasing
the bulkiness of R1 for the monocobalt complexes (entries 1, 3,
5, 11, 13, and 15, Table 5). In contrast, complexes with bulkier
R1 substituents showed higher activity for the dicobalt catalysts
(entries 2, 4, 6, 12, 14, and 16, Table 5). However, the addition
of a methyl group at the para position of the N-aryl ring also
led to an increase of the catalytic activity, at both 1 atm (entries
1−4 and 7−10, Table 5) and 10 atm (entries 11−14 and 17−
20, Table 5), similar to the case for the iron complexes. The
dicobalt complexes always exhibited much higher activity than
Figure 4. Comparison of the distribution of oligomers produced by
Fe1-1 and Fe2-1 (Table 3, entries 11 and 12).
produce longer-chain oligomers than do the corresponding
monoiron complexes; this is attributed to the existence of
synergistic effects from the dimetal complexes.
Moreover, the polyethylene samples obtained at 10 atm were
evaluated (entries 11−20, Table 3), which revealed that the
diiron complex precatalysts produce polyethylene with higher
molecular weights and wider polydispersity than do the
corresponding monoiron analogues. Higher melting points
were observed for polyethylene, indicating high linearity, which
was confirmed by 13C NMR spectroscopic measurements (in
Figure 5) for the polyethylene obtained in entry 14 of Table 3.
Figure 5. 13C NMR spectrum of polyethylene (entry 14, Table 3).
2313
dx.doi.org/10.1021/om301086p | Organometallics 2013, 32, 2309−2318

Organometallics
Article
a
Table 4. Catalytic Results Based on Co2-1/MAO
b
oligomer
c
d
d
d
d
e
entry
t (min)
Al/Co
T (°C)
activity
C4/∑C
C6/∑C
C8/∑C
α-C/∑C
K
f
1
30
30
30
30
30
30
30
30
30
5
1000
1000
1250
1500
1750
2000
1500
1500
1500
1500
1500
1500
1500
1500
1500
20
20
20
20
20
20
0
0.34
0.84
0.99
1.19
1.00
0.99
0.93
0.68
0.32
1.81
1.77
1.65
1.51
0.90
0.63
77
14.1
13.2
12.6
11.9
13.2
13.2
12.6
11.4
9.13
12.4
12.0
11.8
11.7
12.0
11.3
4.1
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
0.61
0.59
0.64
0.67
0.60
0.55
0.58
0.59
0.57
0.64
0.59
0.54
0.56
0.50
0.49
2
80.0
82.0
83.7
80.6
80.1
81.3
84.1
86.2
80.6
81.1
82.0
82.0
83.6
83.8
3.83
3.05
2.61
3.58
3.45
3.59
3.01
2.54
4.86
4.46
3.76
3.01
2.65
2.75
3
4
5
6
7
8
40
60
20
20
20
20
20
20
9
10
11
12
13
14
15
10
15
20
40
60
a
b
c
General conditions: cat., 1.0 μmol of Co2-1; ethylene pressure, 1 atm; solvent, toluene (30 mL); cocatalyst, MAO. Determined by GC. In units of
d
e
106 g (mol of Co)−1 h−1. ∑C4, ∑C6, ∑C8, and ∑C denote the total amounts of butene, hexene, octene and oligomers in mol %, respectively. K =
(rate of propagation)/[(rate of propagation) + (rate of chain transfer)] = (mol of C14)/(mol of C12).14 The cocatalyst is MMAO.
f
a
Table 5. Catalytic Results Based on Cobalt Complexes
b
oligomer
c
d
d
d
d
e
entry
cat.
P (atm)
activity
∑C4/∑C
∑C6/∑C
∑C8/∑C
α-C/∑C
K
1
Co1-1
Co2-1
Co1-2
Co2-2
Co1-3
Co2-3
Co1-4
Co2-4
Co1-5
Co2-5
Co1-1
Co2-1
Co1-2
Co2-2
Co1-3
Co2-3
Co1-4
Co2-4
Co1-5
Co2-5
1
1
0.61
1.19
0.65
0.98
0.74
0.89
1.25
1.33
1.12
1.48
9.70
14.9
11.3
13.7
12.5
13.1
13.9
17.4
14.9
16.6
88.1
83.7
92.0
85.7
79.4
70.1
87.0
80.0
92.0
81.7
77.1
71.1
80.1
78.9
82.1
74.1
65.3
64.9
67.1
60.1
8.90
11.9
5.30
10.2
13.5
17.4
10.0
14.1
5.30
14.0
10.1
11.5
6.65
7.12
6.70
9.12
11.0
11.2
10.1
12.1
2.04
2.61
1.53
2.33
4.22
6.87
2.00
4.23
1.53
4.11
3.01
3.53
2.54
2.78
2.58
3.19
3.82
3.71
3.85
4.01
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
0.40
0.67
0.49
0.64
0.52
0.57
0.56
0.58
0.49
0.61
0.49
0.51
0.47
0.52
0.49
0.56
0.57
0.58
0.52
0.57
2
3
1
4
1
5
1
6
1
7
1
8
1
9
1
10
11
12
13
14
15
16
17
18
19
20
1
10
10
10
10
10
10
10
10
10
10
a
General conditions: cat., 2.0 μmol of Co; solvent, toluene (30 mL for 1 atm and 100 mL for 10 atm); cocatalyst, MMAO (Al/Co = 1000); reaction
b
c
d
temperature, 0 °C; reaction time, 30 min. Determined by GC. In units of 106 g (mol of Co)−1 h−1. ∑C4, ∑C6, ∑C8, and ∑C denote the total
e
amounts of butene, hexene, octene, and oligomers in mol %, respectively. K = (rate of propagation)/[(rate of propagation) + (rate of chain
transfer)] = (mol of C14)/(mol of C12).14
the corresponding monocobalt complexes for ethylene
oligomerization, which is attributed to synergistic effects.
the monometal complexes. Elemental analysis of these
complexes can be used to further confirm the mono- or
bimetallic nature of the complexes. All complexes have been
evaluated as catalysts for ethylene oligomerization/polymer-
ization, and the results showed that the dimetallic (both Fe and
Co) complexes always exhibited much higher activity than did
the corresponding monometallic complexes. Additionally, the
iron complexes always showed much higher activities and
higher K values for ethylene oligomerization than did the cobalt
complexes. The activity obtained by the diiron complexes can
be as high as 4.0 × 107 g (mol of Fe)−1 h−1 with high α-olefin
CONCLUSION
■
A new series of iron/cobalt complexes ligated by 2,4-bis(6-
iminopyridin-2-yl)-3H-benzazepines have been synthesized and
fully characterized. Reaction of the 2,4-bis(6-iminopyridin-2-
yl)-3H-benzazepines with iron/cobalt dichloride in 1/1 and 1/2
molar ratios afforded monometal and dimetal complexes,
respectively. The free νCN bond stretching frequency was
clearly detected by FT-IR spectroscopy (around 1640 cm−1) in
2314
dx.doi.org/10.1021/om301086p | Organometallics 2013, 32, 2309−2318

Organometallics
Article
CH3), 1.99 (s, 6H, 2 × CH3), 1.95 (s, 6H, 2 × CH3). 13C NMR (100
MHz, CDCl3): δ 167.5, 167.1, 158.8, 155.8, 155.6, 155.4, 154.1, 148.9,
148.8, 147.3, 137.2, 137.1, 135.3, 131.2, 129.8, 129.4, 128.3, 128.1,
128.0, 127.7, 125.5, 124.8, 124.7, 123.3, 123.2, 122.2, 119.8, 29.4, 18.1,
18.0, 16.7, 16.6. Anal. Calcd for C40H37N5 (588): C, 81.74; H, 6.35; N,
11.92. Found: C, 81.37; H, 6.15; N, 11.56.
selectivity (>99%). Furthermore, the substituents on the N-aryl
rings had an obvious influence on the catalytic activity as well as
the distribution of products.
EXPERIMENTAL SECTION
■
2,4-Bis{6-[1-(2,6-diethylphenylimino)ethyl]pyridin-2-yl}-3H-ben-
zazepine (L2). In a manner similar to that described for L1, L2 was
also prepared in 49% yield as a yellow solid. Mp: 141−142 °C. FT-IR
(KBr disk, cm−1): 3057, 2963, 2931, 1872, 1638 (νCN), 1566, 1452,
General Considerations. All manipulations of air- and/or
moisture-sensitive compounds were carried out under a nitrogen
atmosphere using standard Schlenk techniques. Toluene was refluxed
over sodium benzophenone and distilled under nitrogen prior to use.
Methylaluminoxane (MAO, 1.46 M solution in toluene) and modified
methylaluminoxane (MMAO, 1.93 M in heptane, 3A) were purchased
from Akzo Nobel Corp. High-purity ethylene was purchased from
Beijing Yansan 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 MHz instrument at
ambient temperature using TMS as an internal standard. FT-IR
spectra were recorded on a Perkin-Elmer System 2000 FT-IR
spectrometer. Elemental analysis was carried out using an HPMOD
1106 microanalyzer. GC analysis was performed with a Agilent
Technologies 7890A gas chromatograph equipped with a flame
ionization detector and a 30 m column (0.2 mm i.d., 0.25 mm film
thickness). MALDI-TOF spectroscopy was conducted on a Bruker
Autoflex III instrument, using CCA as the substrate. Molecular weights
(Mw) and molecular weight distributions (Mw/Mn) of polyethylenes
were determined by a PL-GPC220 instrument at 150 °C with three
PLgel 10 μm MIXED-B columns and 1,2,4-trichlorobenzene as the
solvent. Melting points of polyethylenes were obtained from the
second scanning run on a Q2000 DSC-7 instrument at a heating rate
of 10 °C min−1 to 150 °C.
1
1362, 1318, 1238, 1196, 1114, 1069, 820, 805, 762. H NMR (400
MHz, CDCl3): δ 8.41 (d, J = 7.8 Hz, 1H, Py Hm), 8.37 (d, J = 7.6 Hz,
1H, Py Hm), 7.93−7.84 (m, 2H, Py Hm + Py Hp), 7.77−7.70 (m, 2H,
Py Hp + CH), 7.65 (d, J = 8.1 Hz, 1H, Ar H), 7.60 (d, J = 7.7 Hz, 2H,
Ar H), 7.47 (d, J = 7.5 Hz, 1H, Ar H), 7.30 (d, J = 7.4 Hz, 1H, Ar H),
7.10 (t, J = 8.2 Hz, 4H, Ar H), 7.07−7.00 (m, 2H, Ar H); 4.00 (s, 2H),
2.42−2.22 (m, 8H, CH2), 2.21 (s, 3H, CH3), 2.06 (s, 3H, CH3), 1.10
(t, 6H, J = 7.6, 2 × CH3), 1.03 (t, 6H, J = 7.6, 2 × CH3). 13C NMR
(100 MHz, CDCl3): δ 167.0, 166.6, 158.6, 155.6, 155.5, 155.3, 154.0,
147.8, 147.7, 147.1, 137.1, 136.9, 135.2, 131.1, 129.6, 129.3, 128.1,
127.5, 126.1, 136.0, 124.7, 124.5, 123.5, 123.3, 122.1, 119.6, 50.9, 29.3,
24.6, 1.8, 13.7. Anal. Calcd for C44H45N5 (647): C, 82.08; H, 7.04; N,
10.88. Found: C, 82.07; H, 7.15; N, 11.06.
2,4-Bis{6-[1-(2,6-biisopropylphenylimino)ethyl]pyridin-2-yl}-3H-
benzazepine (L3). In a manner similar to that described for L1, L3
was also prepared in 52% yield as a yellow solid. Mp: 234−235 °C.
FT-IR (KBr disk, cm−1): 3061, 2960, 2927, 2876, 1645 (νCN), 1566,
1453, 1381, 1364, 1317, 1260, 1238, 1191, 110, 1023, 868, 800, 767.
1H NMR (400 MHz, CDCl3): δ 8.41 (d, J = 7.7 Hz, 1H, Py Hm), 8.34
(d, J = 7.7 Hz, 1H, Py Hm), 8.25 (d, J = 7.8, 1H, Py Hm), 7.89−7.78
(m, 2H, Py Hm + Py Hp), 7.69 (m, 2H, Py Hp + CH), 7.62 (d, J = 8.0
Hz, 1H, Ar H), 7.7 (d, J = 7.7 Hz, 1H, Ar H), 7.43 (t, J = 7.5 Hz, 1H,
Ar H), 7.26 (t, J = 7.4 Hz, 1H, Ar H), 7.12 (t, J = 6.2 Hz, 4H, Ar H),
7.09 (m, 2H, Ar H), 3.98 (s, 2H, CH2), 2.73−2.50 (m, 4H, 4 × CH),
2.21 (s, 3H, CH3), 2.06 (s, 3H, CH3), 1.16−0.92 (m, 24H, 4 × CH3).
13C NMR (100 MHz, CDCl3): δ 166.4, 166.1, 160.0, 155.2, 154.8,
153.5, 146.6, 145.9, 136.6, 136.4, 135.2, 134.9, 130.6, 129.1, 128.8,
127.6, 127.1, 124.2, 124.1, 123.3, 123.1, 122.7, 122.5, 121.7, 119.2,
27.8, 22.7, 16.6. Anal. Calcd for C48H53N5 (700): C, 82.36; H, 7.63; N,
10.01. Found: C, 82.15; H, 7.36; N, 9.81.
Synthesis and Characterization of 2,4-Bis(6-acetylpyridin-2-
yl)-3H-benzazepine. A solution of 1 equiv of 2,6-diacetylbrydine
(8.15 g, 50 mmol), 1.5 equiv of o-fluoroaniline (8.32 g, 75 mmol), and
a catalytic amount of p-toluenesulfonic acid (0.5 g) in toluene (200
mL) was refluxed for 8 h. The solvent was evaporated at reduced
pressure, and the residue was then purified by column chromatography
(silica gel, petroleum ether/ethyl acetate 5/1 v/v) to afford the desired
compound (yellow solid, 2.00 g, 21% yield). Mp: 138−139 °C. FT-IR
(KBr disk, cm−1): 1693 (νCO), 1575, 1560, 1450, 1361, 1310, 1240,
1
1111, 1069, 954, 896, 823, 759. H NMR (400 MHz, CDCl3): δ 8.50
2,4-Bis{6-[1-(2,4,6-trimethylphenylimino)ethyl]pyridin-2-yl}-3H-
benzazepine (L4). In a manner similar to that described for L1, L4
was also prepared in 34% yield as a yellow solid. Mp: 178−179 °C.
FT-IR (KBr disk, cm−1): 3051, 2963, 2941, 2913, 2855, 1642 (νCN),
1615, 1569, 1476, 1454, 1436, 1364, 1339, 1313, 1261, 1216, 1147,
1112, 1076, 1031, 1016, 852, 808, 756. 1H NMR (400 MHz, CDCl3):
δ 8.39 (d, J = 8.0 Hz, 1H, Py Hm), 8.36 (d, J = 7.8 Hz, 1H, Py Hm),
8.25 (d, J = 7.8 Hz, 1H, Py Hm), 7.90 (d, J = 7.6 Hz, 1H, Py Hm), 7.86
(t, J = 7.9 Hz, 1H, Py Hp), 7.76−7.69 (m, 2H, Py Hp + CH), 7.64 (d, J
= 8.0 Hz, 1H, Ar H), 7.60 (d, J = 7.6 Hz, 1H, Ar H), 7.47 (t, J = 7.6
Hz, 1H, Ar H), 7.30 (t, J = 7.4 Hz, 1H, Ar H), 6.89 (s, 2H, Ar H), 6.87
(s, 2H, Ar H), 3.99 (s, 2H, CH2), 2.31 (s, 3H, CH3), 2.29 (s, 3H,
CH3), 2.20 (s, 3H, CH3), 2.05 (s, 3H, CH3), 1.95 (s, 6H, 2 × CH3),
1.92 (s, 6H, 2 × CH3). 13C NMR (100 MHz, CDCl3): δ 167.8, 167.5,
158.8, 155.9, 155.5, 154.1, 147.3, 146.4, 146.3, 137.7, 137.2, 137.0,
135.3, 132.5, 132.4, 131.2, 129.8, 129.3, 128.8, 128.3, 127.7, 125.4,
125.3, 124.8, 125.7, 122.2, 121.8, 119.8, 29.4, 20.9, 18.0, 16.6. Anal.
Calcd for C42H41N5 (616): C, 81.92; H, 6.71; N, 11.37. Found: C,
82.11; H, 7.10; N, 10.99.
2,4-Bis{6-[1-(2,6-diethyl-4-methylphenylimino)ethyl]pyridin-2-yl}-
3H-benzazepine (L5). In a manner similar to that described for L1, L5
was also prepared in 39% yield as a yellow solid. Mp: 188−189 °C.
FT-IR (KBr disk, cm−1): 3052, 2965, 2928, 2868, 2643 (νCN), 1566,
1458, 1364, 1334, 1247, 1211, 1145, 1115, 1074, 1033, 883, 813, 747,
622. 1H NMR (400 MHz, CDCl3): δ 8.42 (d, J = 7.7 Hz, 1H, Py Hm),
8.37 (d, J = 7.7 Hz, 1H, Py Hm), 8.27 (d, J = 7.8 Hz, 1H, Py Hm), 7.90
(d, J = 7.7 Hz, 1H, Py Hm), 7.87 (t, J = 7.8 Hz, 1H, Py Hp), 7.76−7.69
(m, 2H, Py Hp + CH), 7.65 (d, J = 8.0 Hz, 1H, Ar H), 7.61 (d, J = 7.7
Hz, 1H, Ar H), 7.47 (t, J = 7.3 Hz, 1H, Ar H), 7.31 (t, J = 7.4 Hz, 1H,
Ar H), 6.93 (s, 2H, Ar H); 6.91 (s, 2H, Ar H), 4.00 (s, 2H, CH2), 2.36
(d, J = 7.9 Hz, 1H, Py Hm), 8.05 (d, J = 7.6 Hz, 1H, Py Hm), 7.83 (d, J
= 7.8, 1H, Py Hm), 7.94 (d, J = 7.6 Hz, 1H, Py Hm), 7.89 (t, J = 7.8 Hz,
1H, Py Hp), 7.83 (t, J = 7.8 Hz, 1H, Py Hp), 7.73 (s, 1H, CH), 7.62 (t,
J = 9.2 Hz, 2H, Ar H), 7.49 (t, J = 7.6 Hz, 1H, Ar H), 7.33 (t, J = 7.5
Hz, 1H, Ar H), 3.99 (s, 2H, CH2), 2.77 (s, 3H, CH3), 2.60 (s, 3H,
CH3). 13C NMR (100 MHz, CDCl3): δ 200.4, 199.5, 157.9, 155.9,
154.4, 153.3, 152.6, 147.1, 137.7, 134.3, 131.2, 130.0, 129.5, 128.3,
128.0, 125.1, 124.2, 122.6, 120.1, 28.9, 25.7. Anal. Calcd for
C24H19N3O2 (381): C, 75.57; H, 5.02; N, 11.02. Found: C, 75.27;
H, 5.15; N, 11.36.
Syntheses and Characterizations of 2,4-Bis[6-(1-
aryliminoethyl)pyridin-2-yl]-3H-benzazepines L1−L5. A repre-
sentative synthesis is as follows: a solution of 2,4-bis(6-acetylpyridin-2-
yl)-3H-benzazepine (0.38 g, 1.0 mmol), 2,6-dimethylaniline (0.27 g,
2.2 mmol), and a catalytic amount of p-toluenesulfonic acid (0.03 g)
were refluxed in toluene (25 mL) for 6 h. Molecular sieves (4 Å, 2 g)
were added to remove water. After filtration and solvent evaporation,
the crude product was purified by column chromatography (silica gel,
petroleum ether/ethyl acetate 30/1 v/v). 2,4-Bis{6-[1-(2,6-
dimethylphenylimino)ethyl]pyridin-2-yl}-3H-benzazepine (L1) was
collected and concentrated, giving a yellow solid (0.29 g, 43%
yield). Mp: 140−141 °C. FT-IR (KBr disk, cm−1): 3017, 2940, 2851,
1644 (νCN), 1616, 1593, 1566, 1468, 1455, 1436, 1364, 1338, 1317,
1206, 1113, 1093, 810, 761. 1H NMR (400 MHz, CDCl3): δ 8.41 (d, J
= 7.9 Hz, 1H, Py Hm), 8.38 (d, J = 7.7 Hz, 1H, Py Hm), 8.27 (d, J = 7.8
Hz, 1H, Py Hm), 7.91 (d, J = 7.7 Hz, 1H, Py Hm), 7.87 (t, J = 7.8 Hz,
1H, Py Hp), 7.77 −7.70 (m, 2H, Py Hp + CH), 7.65 (d, J = 8.0 Hz, 1H,
Ar H), 7.61 (d, J = 7.7 Hz, 1H, Ar H), 7.47 (t, J = 7.1 Hz, 1H, Ar H),
7.31 (t, J = 7.1 Hz, 1H, Ar H), 7.06 (t, J = 8.0 Hz, 4H, Ar H), 6.99−
6.90 (m, 2H, Ar H), 4.01 (s, 2H); 2.21 (s, 3H, CH3), 2.06 (s, 3H,
2315
dx.doi.org/10.1021/om301086p | Organometallics 2013, 32, 2309−2318

Organometallics
Article
(d, J = 9.0 Hz, 3H, CH3), 2.34 (s, 3H, CH3), 2.33−2.24 (m, 8H, 4 ×
CH2), 2.22 (s, 3H, CH3), 2.07 (s, 3H, CH3), 1.09 (t, J = 7.5 Hz, 6H, 2
× CH3), 1.03 (t, J = 7.5 Hz, 6H, 2 × CH3). 13C NMR (100 MHz,
CDCl3): δ 167.2, 167.0, 156.0, 155.6, 154.1, 147.3, 145.3, 137.2, 137.0,
135.4, 132.7, 132.5, 131.2, 129.8, 129.3, 128.3, 127.6, 126.9, 126.8,
124.8, 124.6, 122.2, 122.1, 119.8, 29.4, 24.7, 21.2, 16.8, 14.0, 13.9. Anal.
Calcd for C46H49N5 (672): C, 82.23; H, 7.35; N, 10.42. Found: C,
82.11; H, 7.19; N, 10.11.
Synthesis of Complexes. Mononuclear Cobalt Complexes
(Co1-n, n = 1−5). A representative synthesis of Co1-1 is as follows:
a mixture of 2,4-bis{6-[1-(2,6-dimethylphenylimino)ethyl]pyridin-2-
yl}-3H-benzazepine (L1); 0.10 mmol) and CoCl2 (0.10 mmol) in
THF (5 mL) was stirred for 8 h at room temperature. The precipitate
was collected by filtration, washed with diethyl ether (3 × 5 mL), and
then dried under vacuum to give Co1-1: yellow solid, 66.5% yield. FT-
IR (KBr disk, cm−1): 3422, 3065, 3018, 2960, 2915, 1646 (νCN),
1624 (νCN), 1582, 1466, 1366, 1268, 1208, 1166, 1094, 1030, 809,
770, 644. Anal. Calcd for C40H37Cl2CoN5 (716): C, 66.95; H, 5.20; N,
9.76. Found: C, 66.89; H, 5.47; N, 9.41. MS (MALDI-TOF, m/z):
calcd 716.18, found 646.6 [M − 2Cl]+.
(875): C, 57.62; H, 4.72; N, 8.00. Found: C, 57.59; H, 4.64; N, 8.08.
MS (MALDI-TOF, m/z): calcd 875.08, found 862.7 [M − 12]+.
Co2-5: blue solid, 44.7% yield. FT-IR (KBr disk, cm−1): 3414, 3076,
2967, 2929, 2874, 1623 (νCN), 1584, 1460, 1429, 1371, 1256, 1212,
1059, 1029, 859, 814, 744, 666. Anal. Calcd for C46H49Cl4Co2N5
(931): C, 59.31; H, 5.30; N, 7.52. Found: C, 59.23; H, 5.19; N, 7.61.
MS (MALDI-TOF, m/z): calcd 931.14, found 918.8 [M − 12]+, 765.7
[M − 12 − CCA + Cl]+, 730.7 [M − 12 − CCA]+.
Mononuclear Iron Complexes Fe1-n (n = 1−5). A representative
synthesis of complex Fe1-1 is as follows: a mixture of 2,4-bis{6-[1-
(2,6-dimethylphenylimino)ethyl]pyridin-2-yl}-3H-benzazepine (L1;
0.10 mmol) and FeCl2·4H2O (0.10 mmol) in THF (5 mL) was
stirred for 8 h at room temperature. The precipitate was collected by
filtration, washed with diethyl ether (3 × 5 mL), and then dried under
vacuum to afford Fe1-1: gray solid, 58.1% yield. FT-IR (KBr disk,
cm−1): 3381, 3061, 3018, 2958, 2916, 2854, 1645 (νCN), 1638
(νCN), 1580, 1469, 1362, 1316, 1258, 1207, 1092, 1032, 808, 766,
664. Anal. Calcd for C40H37Cl2FeN5 (713): C, 67.24; H, 5.22; N, 9.80.
Found: C, 67.11; H, 5.01; N, 9.90. MS (MALDI-TOF, m/z): calcd
713.18, found m/z 703.0 [M − 10]+, 891.2 [M − 10 + CCA]+.
Fe1-2: gray solid, 64.9% yield. FT-IR (KBr disk, cm−1): 3399, 3067,
2929, 2868, 1641 (νCN), 1627 (νCN), 1585, 1463, 1284, 1175,
1102, 803, 760. Anal. Calcd for C44H45Cl2FeN5 (769): C, 68.58; H,
5.89; N, 9.09. Found: C, 68.33; H, 5.60; N, 9.42. MS (MALDI-TOF,
m/z): calcd 769.24, found 887.8 [M − 2Cl + CCA]+, m/z 734.7 [M −
Cl]+, 699.7 [M − 2Cl]+.
Co1-2: yellow solid, 70.3% yield. FT-IR (KBr disk, cm−1): 3445,
3066, 2965, 2929, 2873, 1640 (νCN), 1626 (νCN), 1580, 1453,
1367, 1261, 1103, 806, 769, 665. Anal. Calcd for C44H45Cl2CoN5
(772): C, 68.30; H, 5.86; N, 9.05. Found: C, 67.94; H, 5.57; N, 9.09.
MS (MALDI-TOF, m/z): calcd 772.24, found 702.6 [M − 2Cl]+.
Co1-3: yellow solid, 65.5% yield. FT-IR (KBr disk, cm−1): 3061,
2962, 2926, 2868, 1643 (νCN), 1631 (νCN), 1583, 1455, 1365,
1318, 1258, 1207, 1110, 800, 769, 664. Anal. Calcd for
C48H53Cl2CoN5 (828): C, 69.48; H, 6.44; N, 8.44. Found: C, 65.45;
H, 6.61; N, 8.21. MS (MALDI-TOF, m/z): calcd 828.30, found: 758.7
[M − 2Cl]+, 793.7 [M − Cl]+, 946.8 [M − 2Cl + CCA]+.
Fe1-3: gray solid, 65.3% yield. FT-IR (KBr disk, cm−1): 3443, 3061,
2962, 2926, 2868, 1645 (νCN), 1629 (νCN), 1581, 1456, 1366, 665.
Anal. Calcd for C48H53Cl2FeN5 (825): C, 69.74; H, 6.46; N, 8.47.
Found: C, 70.03; H, 6.51; N, 8.59. MS (MALDI-TOF, m/z): calcd
825.30, found 790.7 [M − Cl]+.
Co1-4: yellow solid, 65.1% yield. FT-IR (KBr disk, cm−1): 3438,
2960, 2917, 2858, 1694, 1641 (νCN), 1630 (νCN), 1581, 1472,
1454, 1365, 1216, 1105, 1029, 855, 805, 664. Anal. Calcd for
C42H41Cl2CoN5 (744): C, 67.65; H, 5.54; N, 9.39. Found: C, 67.23;
H, 5.12; N, 9.50. MS (MALDI-TOF, m/z): calcd 744.21, found 674.7
[M − 2Cl]+.
Fe1-4: gray solid, 66.7% yield. FT-IR (KBr disk, cm−1): 3389, 1704,
1644 (νCN), 1627 (νCN), 1586, 1470, 1287, 1179, 1093, 808, 773.
Anal. Calcd for C42H41Cl2FeN5 (741): C, 67.93; H, 5.57; N, 9.43.
Found: C, 67.68; H, 5.51; N, 9.59. MS (MALDI-TOF, m/z): calcd
741.21, found 705.7 [M − Cl]+, 894.8 [M − Cl + CCA]+.
Fe1-5: gray solid, 60.0% yield. FT-IR (KBr disk, cm−1): 3389, 3074,
2916, 1707, 1641 (νCN), 1626 (νCN), 1583, 1474, 1282, 1200,
1166, 1025, 853, 806, 748. Anal. Calcd for C46H49Cl2FeN5 (797): C,
69.18; H, 6.18; N, 8.77. Found: C, 68.93; H, 6.23; N, 9.01. MS
(MALDI-TOF, m/z): calcd 797.27, found 761.8 [M − Cl]+, 951.7 [M
− Cl + CCA]+.
Co1-5: yellow solid, 47.6% yield. FT-IR (KBr disk, cm−1): 3443,
3057, 2965, 2928, 2873, 1644 (νCN), 1630 (νCN), 1582, 1458,
1367, 1259, 1211, 1108, 859, 808, 738, 665. Anal. Calcd. for
C46H49Cl2CoN5 (800): C, 68.91; H, 6.16; N, 8.74. Found: C, 68.56;
H, 6.08; N, 8.09. MS (MALDI-TOF, m/z): calcd 800.27, found 730.8
[M − 2Cl]+, 918.9 [M − 2Cl + CCA]+.
Dinuclear Iron Complexes Fe2-n (n = 1−5). A representative
synthesis of complex Fe2-1 is as follows: a mixture of 2,4-bis{6-[1-
(2,6-dimethylphenylimino)ethyl]pyridin-2-yl}-3H-benzazepine (L1;
0.10 mmol) and 2 equiv of FeCl2 (0.20 mmol) in THF (7 mL) was
stirred for 8 h at room temperature. The precipitate was collected by
filtration, washed with diethyl ether (3 × 5 mL), and then dried under
vacuum to afford Fe2-1: blue solid, 45.6% yield. FT-IR (KBr disk,
cm−1): 3417, 3069, 2959, 2919, 1623 (νCN), 1585, 1466, 1367, 1257,
1208, 1096, 1031, 806, 773, 664. Anal. Calcd for C40H37Cl4Fe2N5
(841): C, 57.11; H, 4.43; N, 8.32. Found: C, 56.89; H, 4.23; N, 8.50.
MS (MALDI-TOF, m/z): 841.05, found 831.7 [M − 10]+, 678.5 [M
− 163(C9H9NO2)]+.
Dinuclear Cobalt Complexes Co2-n (n = 1−5). A representative
synthesis of complex Co2-1 is as follows: a mixture of 2,4-bis{6-[1-
(2,6-dimethylphenylimino)ethyl]pyridin-2-yl}-3H-benzazepine (L1;
0.10 mmol) and 2 equiv of CoCl2 (0.20 mmol) in THF (7 mL)
was stirred for 8 h. The precipitate was collected by filtration, washed
with diethyl ether (3 × 5 mL), and then dried under vacuum to afford
Co2-1: blue solid, 51.5% yield. FT-IR (KBr disk, cm−1): 3394, 2915,
1623 (νCN), 1584, 1465, 1560, 1465, 1428, 1365, 1256, 1207, 1097,
1028, 803, 777, 742. Anal. Calcd for C40H37Cl4Co2N5 (847): C, 56.69;
H, 4.40; N, 8.26. Found: C, 56.35; H, 4.45; N, 8.44. MS (MALDI-
TOF, m/z): calcd 847.04, found 834.7 [M − 12]+, 681.5 [M − 12 −
CCA + Cl]+, 646.6 [M − 12 − CCA]+.
Fe2-2: blue solid, 47.6% yield. FT-IR (KBr disk, cm−1): 3389, 3069,
2966, 1706, 1627 (νCN), 1585, 1460, 1333, 1174, 1099, 809, 771.
Anal. Calcd for C44H45Cl4Fe2N5 (897): C, 58.89; H, 5.05; N, 7.80.
Found: C, 59.01; H, 5.40; N, 7.64. MS (MALDI-TOF, m/z): calcd
897.11, found 887.7 [M − 10]+, 734.6 [M − 163(C9H9NO2)]+.
Fe2-3: blue solid, 44.4% yield. FT-IR (KBr disk, cm−1): 3399, 3064,
2963, 2926, 2867, 1620 (νCN), 1583, 1461, 1366, 1320, 1257, 1200,
1108, 1151, 803, 770, 665. Anal. Calcd for C48H53Cl4Fe2N5 (953): C,
60.46; H, 5.60; N, 7.35. Found: C, 60.16; H, 5.55; N, 7.71. MS
(MALDI-TOF, m/z): calcd 953.17, found 943.8 [M − 10]+, 790.7 [M
− 163(C9H9NO2)]+.
Co2-2: blue solid, 60.3% yield). FT-IR (KBr disk, cm−1): 3417,
3077, 2966, 2928, 2874, 1623 (νCN), 1584, 1560, 1460, 1429, 1371,
1257, 1212, 1110, 1060, 1030, 859, 813, 743, 663. Anal. Calcd for
C44H45Cl4Co2N5 (903): C, 57.62; H, 4.72; N, 8.00. Found: C, 57.43;
H, 4.50; N, 7.75. MS (MALDI-TOF, m/z): calcd 903.11, found 891.2
[M − 12]+, 703.0 [M − 12 − CCA]+.
Co2-3: blue solid, 51.1% yield. FT-IR (KBr disk, cm−1): 3421, 3065,
2964, 2925, 2866, 1621 (νCN), 1584, 1463, 1367, 1321, 1158, 1321,
1258, 1201, 1106, 801, 770, 664. Anal. Calcd for C48H53Cl4Co2N5
(959): C, 60.08; H, 5.57; N, 7.30. Found: C, 59.90; H, 5.45; N, 7.55.
MS (MALDI-TOF, m/z): calcd 959.17, found m/z 946.8 [M − 12]+,
793.7 [M − 12 − CCA + Cl]+, 758.7 [M − 12 − CCA]+.
Fe2-4: blue solid, 50.0% yield. FT-IR (KBr disk, cm−1): 3389, 3074,
2916, 1707, 1626 (νCN), 1583, 1474, 1282, 1200, 1166, 1025, 853,
806, 748. Anal. Calcd for C42H41Cl4Fe2N5 (869): C, 58.03; H, 4.75; N,
8.06. Found: C, 58.10; H, 5.01; N, 7.83. MS (MALDI-TOF, m/z):
calcd 869.08, found m/z 858.7 [M − 10]+, 670.5 [M − 10 − CCA]+.
Co2-4: blue solid, 56.0% yield. FT-IR (KBr disk, cm−1): 3421, 3079,
3019, 2954, 2918, 2856, 1621 (νCN), 1585, 1460, 1366, 1255, 1217,
1107, 1024, 855, 806, 743, 667. Anal. Calcd for C42H41Cl4Co2N5
2316
dx.doi.org/10.1021/om301086p | Organometallics 2013, 32, 2309−2318

Organometallics
Article
Fe2-5: blue solid, 46.9% yield. FT-IR (KBr disk, cm−1): 3389, 1705,
1626 (νCN), 1582, 1453, 1388, 1266, 1167, 1104, 1033, 811, 771.
Anal. Calcd for C46H49Cl4Fe2N5 (925): C, 59.70; H, 5.34; N, 7.57.
Found: C, 60.09; H, 5.40; N, 7.65. MS (MALDI-TOF, m/z): calcd
925.14, found 915.0 [M − 10]+, 762.0 [M − 163(C9H9NO2)]+.
General Procedure for Ethylene Oligomerization. Ethylene
Oligomerization at Ambient Pressure. The precatalyst was dissolved
in toluene using standard Schlenk techniques, and the reaction
solution was stirred with a magnetic stir bar under an ethylene
atmosphere (1 atm) with a steam bath for controlling the desired
temperature. Finally, the required amount of cocatalyst (MAO,
MMAO) was added by a syringe. After the reaction was carried out
for the required period, a small amount of the reaction solution was
collected and terminated by the addition of 10% aqueous hydrogen
chloride immediately. The organic layer was analyzed by gas
chromatography (GC) for monitoring the oligomers formed; the
precipitated polymer was collected, washed with water and ethanol,
and finally dried.
Ethylene Oligomerization at Elevated Pressure (10 atm). A 300
mL stainless steel autoclave, equipped with a mechanical stirrer and a
temperature controller, was employed for the reaction. First, 50 mL of
toluene (freshly distilled) was injected into the clave, which was full of
ethylene. When the required temperature was reached, another 30 mL
of toluene, in which the complex (2.0 μmol of metal) was previously
dissolved, the required amount of cocatalyst (MAO, MMAO), and
residual toluene were added by syringe successively. The reaction
mixture was intensely stirred for the desired time under the
corresponding pressure of ethylene through the entire experiment.
The reaction was terminated and analyzed using the same procedure
as for ethylene oligomerization and polymerization.
REFERENCES
■
(1) (a) Guo, N.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 2008,
130, 2246. (b) Gahan, L. R.; Smith, S. J.; Neves, A.; Schenk, G. Eur. J.
Inorg. Chem. 2009, 2009, 2745. (c) Gavrilova, A. L.; Bosnich, B. Chem.
Rev. 2004, 104, 349. (d) Szuromi, E.; Shen, H.; Goodall, B. L.; Jordan,
R. F. Organometallics 2008, 27, 402. (e) Bahuleyan, B. K.; Kim, J. H.;
Seo, H. S.; Oh, J. M.; Ahn, I. Y.; Ha, C. S.; Park, D. W.; Kim, I. Catal.
Lett. 2008, 126, 371. (f) Guo, Y.; Ai, P.; Han, L.; Chen, L.; Li, B.-G.;
Jie, S. J. Organomet. Chem. 2012, 716, 222.
(2) (a) Mi, P. K.; Xu, S.; Qu, L. D.; Zhang, D. S.; Chen, Q. A.; Wang,
S. H. J. Appl. Polym. Sci. 2011, 121, 21. (b) Budagumpi, S.; Liu, Y.; Suh,
H.; Kim, I. J. Organomet. Chem. 2011, 696, 1887. (c) Gurubasayaraj, P.
M.; Nomura, K. Organometallics 2010, 29, 3500. (d) Salata, M. R.;
Marks, T. J. Macromolecules 2009, 42, 1920. (e) Rodriguez, B. A.;
Delferro, M.; Marks, T. J. J. Am. Chem. Soc. 2009, 131, 5902. (f) Noda,
D.; Tanabiki, M.; Tsuchiya, K.; Sunada, Y.; Nagashima, H. Polyhedron
2009, 28, 3935. (g) Ivancheva, N. I.; Kostrova, A. Y.; Oleinik, I. I.;
Tolstikov, G. A.; Ivanchev, S. S. Dokl. Phys. Chem. 2009, 424, 17.
(h) Wang, L. C.; Sun, J. Q. Inorg. Chim. Acta 2008, 361, 1843.
(i) Pelletier, J. D. A.; Fawcett, J.; Singh, K.; Solan, G. A. J. Organomet.
Chem. 2008, 693, 2723. (j) Zhang, S.; Vystorop, I.; Tang, Z. H.; Sun,
W. H. Organometallics 2007, 26, 2456. (k) Zhang, S.; Sun, W. H.;
Kuang, X. F.; Vystorop, I.; Yi, J. J. J. Organomet. Chem. 2007, 692,
5307. (l) Jie, S. Y.; Zhang, D. H.; Zhang, T. Z.; Sun, W. H.; Chen, J.
T.; Ren, Q.; Liu, D. B.; Zheng, G.; Chen, W. J. Organomet. Chem.
2005, 690, 1739.
(3) Delferro, M.; Marks, T. J. Chem. Rev. 2011, 111, 2450.
(4) (a) Xiao, X. H.; Sun, J. Q.; Li, X.; Li, H. F.; Wang, Y. G. J. Mol.
Catal. A: Chem. 2007, 267, 86. (b) Xu, S.; Feng, Z. F.; Huang, J. L. J.
Mol. Catal. A: Chem. 2006, 250, 35.
(5) Kuwabara, J.; Takeuchi, D.; Osakada, K. Chem. Commun. 2006,
3815.
X-ray Crystallographic Studies. Single crystals of compounds 1
and L3 suitable for X-ray diffraction analysis were recrystallized from
their dichloromethane solutions, respectively; meanwhile, single
crystals of complex Co1-1 suitable for X-ray diffraction analysis were
obtained by layering n-pentane on its THF (tetrahydrofuran) solution
at room temperature. With graphite-monochromated Mo Kα radiation
(6) (a) Zhang, D.; Jin, G. X. Organometallics 2003, 22, 2851.
(b) Weng, Z. Q.; Teo, S.; Liu, Z. P.; Hor, T. S. A. Organometallics
2007, 26, 2950. (c) Zhang, D.; Jin, G. X. Inorg. Chem. Commun. 2006,
9, 1322. (d) Wang, W. H.; Jin, G. X. Inorg. Chem. Commun. 2006, 9,
548. (e) Na, S. J.; Joe, D. J.; Sujith, S.; Han, W. S.; Kang, S. O.; Lee, B.
Y. J. Organomet. Chem. 2006, 691, 611. (f) Sujith, S.; Joe, D. J.; Na, S.
J.; Park, Y. W.; Chow, C. H.; Lee, B. Y. Macromolecules 2005, 38,
10027. (g) Hu, T.; Tang, L. M.; Li, X. F.; Li, Y. S.; Hu, N. H.
Organometallics 2005, 24, 2628. (h) Bianchini, C.; Gonsalvi, L.;
Oberhauser, W.; Semeril, D.; Bruggeller, P.; Gutmann, R. Dalton Trans
2003, 3869.
(7) (a) Caris, R.; Peoples, B. C.; Valderrama, M.; Wu, G.; Rojas, R. J.
Organomet. Chem. 2009, 694, 1795. (b) Rodriguez, B. A.; Delferro, M.;
Marks, T. J. Organometallics 2008, 27, 2166. (c) Tanabiki, M.;
Tsuchiya, K.; Motoyama, Y.; Nagashima, H. Chem. Commun. 2005,
3409.
́
(λ = 0.71073 Å), the single-crystal X-ray diffraction for compound 1
was performed on a Bruker SMART 1000 CCD at 273(2) K, and the
single-crystal X-ray diffractions for compounds L3 at 273(2) K and
Co1-1 at 173(2) K were carried out on a Rigaku Saturn724+ CCD (λ
́
= 0.71073 Å). 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 SHELXTL-97 package.18
Crystal data and refinement details are given in the Supporting
Information.
ASSOCIATED CONTENT
* Supporting Information
■
S
(8) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. Rev. 2000, 100,
1169.
A table giving crystal data and processing parameters for
compounds 1, L3, and Co1-1 and CIF files giving X-ray crystal
structure data. This material is available free of charge via the
Internet at http://pubs.acs.org.
(9) (a) Zhao, W.; Yu, J.; Song, S.; Yang, W.; Liu, H.; Hao, X.;
Redshaw, C.; Sun, W.-H. Polymer 2012, 53, 130. (b) Cao, X.; He, F.;
Zhao, W.; Cai, Z.; Hao, X.; Shiono, T.; Redshaw, C.; Sun, W.-H.
Polymer 2012, 53, 1870. (c) Yu, J.; Huang, W.; Wang, L.; Redshaw, C.;
Sun, W.-H. Dalton Trans. 2011, 40, 10209.
(10) (a) Xiao, T.; Zhang, S.; Kehr, G.; Hao, X.; Erker, G.; Sun, W.-H.
Organometallics 2011, 30, 3658. (b) Xiao, T.; Hao, P.; Kehr, G.; Hao,
X.; Erker, G.; Sun, W.-H. Organometallics 2011, 30, 4847.
(11) (a) Ramig, K.; Alli, S.; Cheng, M.; Leung, R.; Razi, R.;
Washington, M.; Kudzma, L. V. Synlett 2007, 18, 2868. (b) Brooke, G.
M.; Matthews, R. S. J. Fluorine Chem. 1988, 40, 109.
(12) (a) Gibson, V. C.; Redshaw, C.; Solan, G. A. Chem. Rev. 2007,
107, 1745. (b) Zhang, W.; Sun, W.-H.; Redshaw, C. Dalton Trans.
2013, DOI: 10.1039/C2DT32337K.
(13) (a) Small, B. L.; Brookhart, M.; Bennett, A. M. A. J. Am. Chem.
Soc. 1998, 120, 4049. (b) Britovsek, G. J. P.; Gibson, V. C.; Kimberley,
B. S.; Maddox, P. J.; McTavish, S. J.; Solan, G. A.; White, A. J. P.;
Williams, D. J. Chem. Commun. 1998, 849.
AUTHOR INFORMATION
Corresponding Author
■
*W.-H.S.: tel, +86-10-62557955; fax, +86-10-62618239; e-mail,
whsun@iccas.ac.cn. C.R.: tel, +44 1482 465219; fax, +44 1482
466410; e-mail, c.redshaw@hull.ac.uk.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by NSFC No. 20904059 and MOST
863 program No. 2009AA033601. The EPSRC is thanked for
the awarded of a travel grant (to C.R.).
2317
dx.doi.org/10.1021/om301086p | Organometallics 2013, 32, 2309−2318

Organometallics
Article
(14) (a) Schulz, G. V. Z. Phys. Chem. B 1935, 30, 379. (b) Schulz, G.
V. Z. Phys. Chem. B 1939, 43, 25. (c) Flory, P. J. J. Am. Chem. Soc.
1940, 62, 1561.
(15) (a) Wang, D.; Liu, S.; Zeng, Y.; Sun, W.-H.; Redshaw, C.
Organometallics 2011, 30, 3001. (b) Britovsek, G. J. P.; Bruce, M.;
Gibson, V. C.; Kimberley, B. S.; Maddox, P. J.; Mastroianni, S.;
McTavish, S. J.; Redshaw, C.; Solan, G. A.; Stromberg, S.; White, A. J.
P.; Williams, D. J. J. Am. Chem. Soc. 1999, 121, 8728. (c) Britovsek, G.
J. P.; Mastroianni, S.; Solan, G. A.; Baugh, S. P. D.; Redshaw, C.;
Gibson, V. C.; White, A. J. P.; Williams, D. J.; Elsegood, M. R. J. Chem.
Eur. J. 2000, 6, 2221. (d) Atiqullah, M.; Hammawa, H.; Hamid, H. Eur.
Polym. J. 1998, 34, 1511.
(16) Chen, Y. F.; Qian, C. T.; Sun, J. Organometallics 2003, 22, 1231.
(17) (a) Yu, J.; Liu, H.; Zhang, W.; Hao, X.; Sun, W.-H. Chem.
Commun. 2011, 47, 3257. (b) Sun, W.-H.; Zhao, W.; Yu, J.; Zhang, W.;
Hao, X.; Redshaw, C. Macromol. Chem. Phys. 2012, 1266. (c) Wang, S.;
Li, B.; Liang, T.; Redshaw, C.; Li, Y.; Sun, W.-H. Dalton Trans 2013,
42 DOI: 10.1039/C3DT00011G.
(18) Sheldrick, G. M. SHELXL-97; University of Gottingen,
̈
Gottingen, Germany, 1997.
̈
2318
dx.doi.org/10.1021/om301086p | Organometallics 2013, 32, 2309−2318