Bidentate iron(II) dichloride complexes bearing substituted 8-(Benzimidazol-2-yl)quinolines: Synthesis, characterization, and ethylene polymerization behavior

Article abstract of DOI:10.1021/om200338b

The series of N-benzimidazolyl-substituted 2-alkyl-8-(benzimidazol-2-yl) quinolines (L1-L10) and 2-phenyl-8-(benzimidazol-2-yl)quinolines (L11-L14) and their respective bidentate iron(II) dichloride complexes (C1-C14) were synthesized and fully characterized. The molecular structures of a representative ligand (L5) and iron complexes (C2, C7) were determined by X-ray crystal structure analyses, and the distorted tetrahedral coordination geometry was observed around the iron center in both complexes C2 and C7. After activation of the iron complexes with methylaluminoxane, the iron catalysts showed activities up to 10⁶ ga€￠mol ^-1a€￠h^-1 in ethylene polymerization at elevated temperature (100 °C), yielding linear polyethylenes. The reaction parameters of the polymerization reactions were optimized, and the effect of the substituents of the different ligands on the catalytic activity and on the obtained polyethylene was discussed.

Full text of DOI:10.1021/om200338b

ARTICLE
pubs.acs.org/Organometallics
Bidentate Iron(II) Dichloride Complexes Bearing Substituted
8-(Benzimidazol-2-yl)quinolines: Synthesis, Characterization, and
Ethylene Polymerization Behavior
Tianpengfei Xiao,† Shu Zhang,† Gerald Kehr,‡ Xiang Hao,† Gerhard Erker,‡ and Wen-Hua Sun*,†,§
†Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry,
Chinese Academy of Science, Beijing 100190, China
‡Organisch-Chemisches Institut der Universit€at M€unster, Corrensstrasse 40, 48149 M€unster, Germany
§State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Science,
Lanzhou 730000, China
S Supporting Information
b
ABSTRACT: The series of N-benzimidazolyl-substituted 2-alkyl-8-(benzimidazol-2-yl)quinolines (L1ÀL10)
and 2-phenyl-8-(benzimidazol-2-yl)quinolines (L11ÀL14) and their respective bidentate iron(II) dichloride
complexes (C1ÀC14) were synthesized and fully characterized. The molecular structures of a representative
ligand (L5) and iron complexes (C2, C7) were determined by X-ray crystal structure analyses, and the
distorted tetrahedral coordination geometry was observed around the iron center in both complexes C2 and
C7. After activation of the iron complexes with methylaluminoxane, the iron catalysts showed activities up to
106 g molÀ1 hÀ1 in ethylene polymerization at elevated temperature (100 °C), yielding linear polyethylenes. The reaction
3
3
parameters of the polymerization reactions were optimized, and the effect of the substituents of the different ligands on the catalytic
activity and on the obtained polyethylene was discussed.
2-benzoxazolyl-6-iminopyridines,14 2-quinoxalinyl-6-iminopyridines,15
1. INTRODUCTION
2-methyl-2,4-bis(6- iminopyridin-2-yl)-1H-1,5-benzodiazepines,16
The market for polyolefins is in the tens of billions of dollars,
iminoquinolines,17 and 2,8-bis(imino)quinoline18 have been
indicating both the importance and interest of academic and
investigated in our group in Beijing, resulting in high activities
industrial views.1 The demand for advanced polyolefins has
in ethylene oligomerization and/or polymerization. Interestingly
resulted in new complex pro-catalysts,2 and the progress of late
the metal pro-catalysts bearing 2,8-bis(imino)quinolines pre-
transition metal catalysis has been witnessed in the past dozen
ferred ethylene polymerization at high temperature (100 °C).
Examining the molecular structures of 2,8-bis(imino)quinolyl
metal dichloride complexes (Chart 1) revealed a distorted
coordination geometry around the metal and indicated different
bonding interactions between the metal and the nitrogen
atoms.18 As a consequence, the quinoline derivatives acting as
bidentate ligands are promising for generating metal catalysts for
ethylene polymerization. Regarding the literature, although
bidentate iron pro-catalysts showed relatively lower activities
toward ethylene oligomerization and polymerization,13a,19 iron
complexes bearing bidentate ligands were good activators in
atom transfer radical polymerization.6c,20 As a consequence a
series of 2-alkyl/phenyl 8-(benzoimidazol-2-yl)quinoline deriva-
tives were prepared and used to form their iron complexes. Their
iron complexes (Chart 1) showed high catalytic activities toward
ethylene polymerization when the reaction temperature was
elevated above 60 °C. The syntheses and characterizations of
2-alkyl or 2-phenyl 8-(benzoimidazol-2-yl)quinoline derivatives
and their iron complexes are reported along with the catalytic
behaviors of iron complexes toward ethylene.
years,3 in which the pioneer works included diiminometal (Ni(II) or
Pd(II)) complexes4 and 2,6-bis(imino)pyridine metal (Fe(II) or
Co(II)) complexes.5 The iron-derived catalysts have drawn great
attention due to economic and environmental views in industry
and academic consideration of the formation of highly linear
ethylene oligomers and polymers. Efforts have been devoted to
modifying bis(imino)pyridyliron complexes6 and designing iron
complexes with alternative organic ligands.7 In addition, the
active species and the polymerization mechanism have been
explored focusing on the iron complexes bearing bis(imino)-
pyridine derivatives.8 In general, these late transition metal
catalysts maintained good catalytic activities in ethylene poly-
merization at relatively lower reaction temperature, but elevated
reaction temperatures resulted either in catalyst deactivation or
in producing low molecular weight polyethylenes or even oligo-
mers. As ethylene polymerization is a highly exothermic reaction
and industrial operating temperatures above 70 °C are preferable,
more bulky substituents9 and geometry-constrained ligands10 were
used in order to maintain good activity of their complex pro-
catalysts in ethylene polymerization at elevated reaction tem-
peratures. In addition, the iron pro-catalysts bearing new ligands
such as 2-imino-1,10-phenanthrolines,11 2-(benzimidazol-2-yl)-
1,10-phenanthrolines,12 2-benzimidazolyl-6-iminopyridines,13
Received: April 21, 2011
Published: June 20, 2011
r
2011 American Chemical Society
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Chart 1
Scheme 1. Synthesis of the Ligands (Ln) and Their Iron
Complexes (Cn)
Figure 1. Molecular structure of L5 with thermal ellipsoids at the 30%
probability level. Hydrogen atoms have been omitted for clarity.
Selected bond lengths (Å) and angles (deg): N1ÀC10 = 1.324(2),
N1ÀC16 = 1.390(3), N3ÀC10 = 1.369(2), N3ÀC11 = 1.379(2);
C10ÀN1ÀC16 = 104.42(16), C10ÀN3ÀC11 = 106.57(16).
Figure 2. Molecular structure of C2. Thermal ellipsoids are shown at
30% probability. Hydrogen atoms have been omitted for clarity. Selected
bond lengths (Å) and angles (deg): FeÀN1 = 2.027(7), FeÀN2 =
2.143(7), FeÀCl1 = 2.255(3), FeÀCl2 = 2.270(3), N1ÀC10 =
1.327(1), N3ÀC10 = 1.371(1); N1ÀFeÀN2 = 89.2(3), N1ÀFeÀ
Cl1 = 112.9(2), N1ÀFeÀCl2 = 110.1(2), N2ÀFeÀCl1 = 109.8(2),
N2ÀFeÀCl2 = 117.4(2), Cl1ÀMÀCl2 = 114.89(1).
2. RESULTS AND DISCUSSION
2.1. Synthesis of 2-R1-8-(1-R2-Benzoimidazol-2-yl)quino-
line Derivatives. As reported in the literature,21 the condensa-
tion reactions of 1,2-phenylenediamine with either 2-alkylquino-
line-8-carboxylic acid or 2-phenylquinoline-8-carboxylic acid in
the presence of polyphosphoric acid (PPA) gave the 2-alkyl/
phenyl 8-(1H-benzoimidazol-2-yl)quinoline derivatives (L1, L3,
L7, and L11, Scheme 1). The N-alkylation of L1, L3, L7, and
L11, respectively, was carried out using a straightforward pro-
cedure13a,22 to obtain the respective ligands in yields of 23% to
96% (Scheme 1). All organic compounds L1 to L14 were
selected bond lengths and angles. In the structure of L5, the
dihedral angle between the quinolinyl plane and the benzimid-
azole plane is 57.7°. The N1ÀC10 bond [1.324(2) Å] is longer
than the typical imino CdN bond [1.22À1.27 Å].13,23 The ethyl
group on the imidazole nitrogen atom N3 stretches to the inner
side because of the flexibility of the single C8ÀC10 bond.
Single crystals of the iron complexes C2 and C7 suitable for
single-crystal X-ray diffraction analysis were obtained by slow
diffusion of diethyl ether into a methanol solution of C2 and C7,
respectively, under a nitrogen atmosphere. The geometry at the
iron center in both complexes is best described as distorted
tetrahedral. The molecular structures of complexes C2 and C7
are shown in Figures 2 and 3 with their selected bond lengths and
angles.
characterized by elemental analysis, H NMR, 13C NMR, and
IR spectroscopy. In addition, compound L5 was confirmed by an
X-ray crystal structure analysis.
2.2. Synthesis of Iron Complexes. The reaction of FeCl2 4
H2O with one equivalent of the respective ligand (L1ÀL14) in
ethanol yielded the corresponding iron complexes (C1ÀC14) in
high yields (80% to 94%) as orange or yellow solids. All iron
complexes were characterized by elemental analyses and IR
spectroscopy. In addition, the structures of complexes C2 and
C7 were confirmed by X-ray crystal structure analysis.
2.3. X-ray Single-Crystal Structure Study. Single crystals of
compound L5 suitable for an X-ray crystal structure analysis were
obtained by slow evaporation of a solution of L5 in ethyl acetate.
The molecular structure of L5 is shown in Figure 1 along with its
1
3
In the structure of complex C2, the dihedral angle formed
by the planes Cl1ÀFeÀCl2 and N1ÀFeÀN2 is 86.02°. The two
FeÀCl bond lengths are similar; however, the FeÀN1 distance is
slightly shorter than the FeÀN2 length. The dihedral angle
between the quinoline and benzimidazole rings is 28.94°.
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Figure 4. GPC curves of PEs by C1 with various Al/Fe molar ratios at
100 °C (entries 4À8 in Table 1).
Table 2. Ethylene Polymerization by C1ÀC14/MAO at
100 °Ca
Figure 3. Molecular structure of C7. Thermal ellipsoids are shown at
30% probability. Hydrogen atoms have been omitted for clarity. Selected
bond lengths (Å) and angles (deg): FeÀN1 = 2.023(2), FeÀN2 =
2.112(2), FeÀCl1 = 2.3006(9), FeÀCl2 = 2.2306(9), N1ÀC10 =
1.331(3), N3ÀC10 = 1.357(3); N1ÀFeÀN2 = 91.11(8), N1ÀFeÀCl1 =
100.91(7), N1ÀFeÀCl2 = 113.48(7), N2ÀFeÀCl1 = 110.35(6),
N2ÀFeÀCl2 = 114.05(6), Cl1ÀMÀCl2 = 121.90(3).
R1
R2
activityb
Mwc(104)
Mw/Mn
c
entry
complex
1
C1
Me
Me
Et
H
6.11
6.81
1.73
1.83
1.64
1.31
2.41
2.46
1.92
1.85
2.56
3.63
2.16
1.94
16.4
21.0
15.4
26.1
28.1
35.5
30.4
31.7
35.2
51.1
32.0
32.7
37.7
64.6
3.9
6.1
5.3
17
20
13
10
24
25
28
5.6
13
23
28
2
C2
Me
H
3
C3
4
C4
Et
Me
Et
5
C5
Et
Table 1. Optimization of the Ethylene Polymerization
Parameters with C1/MAOa
6
C6
Et
iPr
H
7
C7
Pr
c
entry
Al/Fe
T/°C
activityb
Mwc(104)
Mw/Mn
8
C8
Pr
Me
Et
1
2
3
4
5
6
7
8
3000
3000
3000
3000
1000
2000
2500
3500
40
60
0.799
1.35
5.48
6.11
2.91
4.43
5.73
5.93
nd
nd
25
9
C9
Pr
98.1
45.2
16.4
25.3
23.5
18.1
14.5
10
11
12
13
14
C10
C11
C12
C13
C14
Pr
iPr
H
80
17
Ph
Ph
Ph
Ph
100
100
100
100
100
3.9
7.4
4.7
3.7
3.9
Me
Et
iPr
a Conditions: 2 μmol of Fe; 3000 equiv of MAO; 30 atm of ethylene;
30 min; 40 mL of toluene. b 106 g molÀ1(Fe) hÀ1. c Determined by GPC.
3
3
a Conditions: 2 μmol of Fe; 30 atm of ethylene; 30 min; 40 mL of
toluene. b 106 g molÀ1(Fe) hÀ1. c Determined by GPC.
3
3
of the thermally stable active species requires relatively high
temperature.
The atoms N2, C9, C8, C10, and N1 are almost coplanar, with
the largest deviation of C10 at 0.157 Å, and the deviation of the
iron atom from the plane is 0.578 Å.
As shown in Figure 3, the structure of C7 is slightly different
from that of C2 due to the difference of substituents. The
dihedral angle between the quinoline and benzimidazole rings
is 20.41°. Around the iron atom, there is no significant difference
in their bond lengths. However, a smaller deviation of the iron
atom forming the plane defined by N2, C9, C8, C10, and N1
atoms is observed (0.092 Å).
With variation of the Al/Fe molar ratios between 1000 and
3500 at 100 °C reaction temperature (entries 4À8 in Table 1),
the GPC measurements of the respective polyethylenes showed
wide or bimodal distributions (Figure 4). In addition, more
portions of polyethylenes with low molecular weights were
observed when the Al/Fe molar ratios were increased. In the
catalytic system, multiple active species were formed and trans-
formed into the active species producing polyethylenes with low
molecular weights, indicating the increase of chain transfer and
termination at higher Al/Fe molar ratios. The best activity was
obtained with the Al/Fe molar ratios of 3000.
2.4. Catalytic Behavior toward Ethylene Polymerization.
Methylaluminoxane (MAO) was found to be the best co-catalyst,
and a low activity was observed at ambient pressure and 10 atm of
ethylene; however, a good activity was obtained at 30 atm of
ethylene, attributable to the higher monomer concentration
around the active iron centers at higher pressure.5,6a The catalytic
system of C1/MAO was investigated with varying reaction
conditions including the molar ratio of Al/Fe and reaction
temperature. At room temperature, a low activity was ob-
served. When the reaction temperature was increased (Table 1),
the activities were significantly improved to the range of
106 g molÀ1(Fe) hÀ1. Therefore we assume that the formation
In the following, all iron pro-catalysts were investigated for
ethylene polymerization by using the reaction conditions opti-
mized for the activity of C1 (30 atm ethylene, Al/Fe = 3000,
100 °C) (Table 2). Their differences in catalytic activities were
considered as a function of the nature of the ligands with different
substituents R1 and R2.
The influence of the substituents R1 and R2 would be
interesting with fine-tuning ligands for adapting catalytic activ-
ities and properties of resultant polyethylenes. In the series of
pro-catalysts with R1 = Et (entries 3À6, Table 2), with the
exception of C3 with R2 = H, the activity order C4 > C5 > C6
3
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by C1 (R1 = Me) and C3 (R1 = Et) were observed. Therefore
synergic steric and electronic influences were considered with the
substituent R1 due to it being closer to the active iron center. This
fine-tuning of ligands could induce catalytic behaviors of their
iron pro-catalysts and new properties of resultant polyethylenes.
In addition, the representative polyethylenes (entries 3, 7, and
12, Table 2) were characterized by 13C{1H} NMR at 90 °C in
bromobenzene-d5 and approved as highly linear polyethylenes.
The NMR spectra are available in the Supporting Information.
3. CONCLUSIONS
The series of bidentate iron(II) complexes bearing 2-R1-8-
(1-R2-benzimidazol-2-yl)quinolines give highly active catalysts for
ethylene polymerizations upon activation with MAO at 100 °C.
The catalytic activities were achieved only at elevated reaction
temperature. Two substituents of R1 and R2 showed different
influences on the activities of the iron complexes; therefore fine-
tuning the ligands would potentially control the catalytic activities
of iron pro-catalysts and resultant polyethylenes.
Figure 5. GPC curves of PEs obtained by C11ÀC14 (R1 = Ph).
4. EXPERIMENTAL SECTION
4.1. General Considerations. All manipulations of air- and
moisture-sensitive compounds were performed in a nitrogen atmo-
sphere using standard Schlenk techniques. Toluene was refluxed over
sodium-benzophenone and distilled under argon prior to use. Methy-
laluminoxane (a 1.46 M solution in toluene) was purchased from Akzo
Nobel Corp. Other reagents were purchased from Aldrich or Acros
Chemicals. 1H and 13C NMR spectra were recorded on a Bruker DMX
300 MHz or a Bruker DMX 400 MHz instrument at ambient tempera-
ture using TMS as an internal standard. IR spectra were recorded on a
Perkin-Elmer System 2000 FT-IR spectrometer. Elemental analysis was
carried out using an HPMOD 1106 microanalyzer. A Midea PJ21B-A
microwave oven (800 W, 21 L) was used for microwave-assisted
condensation reactions. 13C{1H} NMR spectra of the PE samples were
recorded on a Bruker DMX 200 MHz instrument at 90 °C in
bromobenzene-d5.
4.2. Preparation of the Ligands. Synthesis of 8-(1H-benzimid-
azol-2-yl)-2-methylquinoline (L1). 2-Methylquinoline-8-carboxylic
acid (1.87 g, 10 mmol), o-phenylenediamine (1.08 g, 10 mmol), and
polyphosphoric acid (8 g) were mixed together and irradiated in the
microwave oven (450 W) three times for 1 min. The dark green solution
of the reactants was poured into an iceÀwater mixture, and a yellow solid
precipitated. A NH3 solution was added to adjust the mixture pH value
to 8À9, and the precipitate was filtrated. After drying, it was eluted with
petroleum ether/ethyl acetate (v/v = 1:1) on a silica column, and a white
powder (1.756 g, 6.77 mmol) was obtained. Yield: 68%. Mp: 172À
173 °C. IR (KBr; cmÀ1): 3188, 3053, 1613, 1598, 1572, 1501, 1422,
1402, 1319, 1278, 1128, 839, 797, 764, 729, 698. 1H NMR (300 MHz,
CDCl3): δ 13.55 (s, 1H, NH); 9.00 (d, J = 7.5 Hz, 1H), 7.96 (d, J =
8.0 Hz, 1H), 7.87 (br, 1H), 7.70 (d, J = 7.5 Hz, 1H), 7.64À7.48 (m, 2H),
7.34À7.16 (m, 3H), 2.74 (s, 3H, Me). 13C{1H} NMR (75 MHz,
CDCl3): δ 158.9 (C), 151.9 (C), 144.8 (C), 143.3 (C), 137.6 (CH),
134.1 (C), 130.2 (CH), 129.7 (CH), 127.0 (C), 125.9 (CH), 125.0 (C),
122.8 (CH), 122.3 (CH), 122.1 (CH), 119.4 (CH), 111.4 (CH), 25.8
(Me). Anal. Calcd for C17H13N3 (259.31): C, 78.74; H, 5.05; N, 16.20.
Found: C, 79.02; H, 5.27; N, 15.83.
Figure 6. GPC curves of PEs by iron pro-catalysts with R2 = H.
seems to be governed by the electronic influences of the ligands
with electron-donating features of alkyl substituents listed as R2 =
Me (C4) < Et (C5) < iPr (C6). This is consistent with the slow
insertion of ethylene on the electron-rich active species in late
transition metal catalytic systems.14a The same trend of catalytic
activities was also observed in the series of iron pro-catalysts with
R1 = Me, Pr, or Ph, respectively. Therefore the electronic effect
was a major issue caused by the substituent R2 because R2 is too
far removed from the active iron center. Broad molecular weight
distributions were obtained due to multimodal polymers ob-
served in the GPC traces,5 and multiactive species of iron pro-
catalysts were imaged along with the chain transfer to excessive
amounts of Al centers.8,24 Checking the influences of the ligand
environment on the properties of polyethylenes obtained with
fixing R1 = Ph (Figure 5), the molecular weights of the resultant
polyethylenes gradually increased with broader molecular weight
distributions, along with changing the R2 substituent from hydro-
gen to isopropyl, Mw (C11, R2 = H) < Mw (C12, R2 = Me) < Mw
(C13, R2 = Et) < Mw (C14, R2 = iPr).
Considering the influence of R1 substituents (closer to the
active iron center) on the catalytic performance of the iron pro-
catalysts, shown in the series of iron pro-catalysts with R2 = Me
(entries 2, 4, 8, and 12, Table 2), their catalytic activities were
ordered as R1 = Me (C2) > Ph (C12) > Pr (C8) > Et (C4).
Beyond the electronic influence on explaining the better activities
of C2 (Me) and C12 (Ph),14a more bulky substituents could
protect the active species as Ph (C12) > Pr (C8) > Et (C4).5,6
Other series of iron pro-catalysts with R2 = H, Et, or iPr also
exhibited the same trend in their catalytic activities.
Considering polyethylenes obtained by iron procatalysts with
R2 = H (entries 1, 3, 7, and 11, Table 2), their molecular weights
and molecular weight distributions were generally increased with
varying the R1 group with bulky alkyl and phenyl groups
(Figure 6), although similar molecular weights for polyethylenes
Synthesis of 2-Methyl-8-(1-methyl-benz[d]imidazol-2-yl)quinoline
(L2). Powdered potassium hydroxide (0.504 g, 9 mmol) was added to a
stirred solution of L1 (1.554 g, 6 mmol) in acetone. After 3 h, methyl
iodide (1.022 g, 7.2 mmol) was added to the reaction mixture with
vigorous stirring. After 6 h, the solvent was removed, the resulting solid
was eluted with petroleum ether/ethyl acetate (v/v = 1:1) on a silica
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column, and white crystals (1.1983 g, 4.39 mmol) were obtained in a
yield of 73%. Mp: 145À146 °C. IR (KBr; cmÀ1): 3060, 1615, 1600,
1498, 1464, 1440, 1425, 1389, 1320, 1281, 1240, 841, 761, 734. 1H NMR
(300 MHz, CDCl3): δ 8.11 (d, J = 8.3 Hz, 1H), 8.05 (d, J = 7.2 Hz, 1H),
7.94 (d, J = 7.9 Hz, 1H); 7.87 (d, J = 8.4 Hz, 1H), 7.61 (t, J = 7.6 Hz, 1H),
7.46 (d, J = 7.2 Hz, 1H), 7.37À7.30 (m, 3H), 3.64 (s, 3H, NMe), 2.63
(s, 3H, CMe). 13C{1H} NMR (75 MHz, CDCl3): δ 159.9 (C), 153.7
(C), 146.1 (C), 143.3 (C), 136.5 (C), 136.4 (CH), 133.1 (CH), 130.1
(CH), 129.5 (C), 126.5 (C), 125.5 (CH), 122.5 (CH), 122.4 (CH),
122.0 (CH), 119.9 (CH), 109.6 (CH), 31.9 (NMe), 25.6 (CMe). Anal.
Calcd for C18H15N3 (273.33): C, 79.10; H, 5.53; N, 15.37. Found: C,
78.83; H, 5.51; N, 14.99.
petroleum ether/ethyl acetate, 2:1). Mp: 104À106 °C. IR (KBr; cmÀ1):
1
3054, 2971, 1606, 1451, 1397, 1270, 1004, 847. H NMR (400 MHz,
CDCl3): δ 8.14 (d, J = 8.5 Hz, 1H), 7.99 (d, J = 7.1 Hz, 1H), 7.95 (d, J =
8.2 Hz, 1H), 7.88 (d, J = 7.1 Hz, 1H), 7.61 (t, J = 7.2 Hz, 1H), 7.51 (d, J =
7.8 Hz, 1H), 7.36À7.30 (m, 3H), 4.12 (q, J = 7.2 Hz, 2H, NEt), 2.88
(q, 2H, J = 7.6 Hz, CEt), 1.26 (t, J = 7.2 Hz, NEt), 1.24 (t, J = 7.6 Hz, CEt).
13C{1H} NMR (100 MHz, CDCl3): δ 164.6 (C), 153.1 (C), 146.2 (C),
143.7 (C), 136.4 (CH), 135.3 (C), 132.8 (CH), 130.2 (C), 129.9 (CH),
126.8 (C), 125.5 (CH), 122.3 (CH), 121.8 (CH), 121.5 (CH), 120.1
(CH), 110.0 (CH), 39.9 (NEt), 32.1 (CEt), 15.0 (NEt), 13.5 (CEt). Anal.
Calcd for C20H19N3 (301.38): C, 79.70; H, 6.35; N, 13.94. Found: C,
79.69; H, 6.53; N, 13.78.
Synthesis of 8-(1H-Benzimidazol-2-yl)-2-ethylquinoline (L3). 2-Ethyl-
quinoline-8-carboxylic acid (2.4 g, 12 mmol), o-phenylenediamine (1.56 g,
14.4 mmol), and phosphoric acid (15 mL) were mixed together and
reacted at 170À180 °C for 6 h. The dark green solution of the reactants
was poured into an iceÀwater mixture after cooling, and a green solid
precipitated. Aqueous ammonia was added to adjust thepHofthe mixture
to 8À9, and the precipitate was filtrated and washed with water. After
drying, it was eluted with petroleum ether/ethyl acetate (v/v = 4:1) on a
silica column, and a white powder (1.91 g, 6.99 mmol) was obtained.
Yield: 58.3%. Mp: 174À176 °C. IR (KBr; cmÀ1): 3045, 3013, 1633, 1614,
1524, 1499, 1435, 1278, 1186, 1143, 962, 851, 788, 672. 1H NMR
(400 MHz, CDCl3): δ 13.89 (s, 1H, NH); 9.11 (d, J = 7.4 Hz, 1H); 8.18
(d, J = 8.5 Hz, 1H); 7.89À7.85 (m, 2H); 7.66 (t, J = 7.7 Hz, 1H); 7.59
(br, 1H); 7.42 (d, J = 8.5 Hz, 1H); 7.31À7.28 (m, 2H); 3.21 (q, J = 7.5 Hz,
2H, Et); 1.60 (t, J = 7.5 Hz, 3H, Et). 13C{1H} NMR (100 MHz, CDCl3):
δ 163.4 (C), 152.0 (C), 144.8 (C), 143.4 (C), 137.7 (CH), 134.2 (C),
130.2 (CH), 129.7 (CH), 127.4 (C),126.1 (CH), 125.3 (C), 122.8 (CH),
122.3 (CH), 121.4 (CH), 119.5 (CH), 111.3 (CH), 32.0 (Et), 12.9 (Et).
Anal. Calcd for C18H15N3 (273.33): C, 79.10; H, 5.53; N, 15.37. Found:
C, 79.21; H, 5.32; N, 15.21.
Synthesis of 2-Ethyl-8-(1-methylbenzimidazol-2-yl)quinoline (L4).
A 1.5 equiv amount of powdered potassium hydroxide (0.2461 g, 4.4
mmol) was added to a solution of L3 (0.8 g, 2.93 mmol) in acetone. After
3 h, methyl iodide (0.4993 g, 3.52 mmol) was added to the reaction
mixture with vigorous stirring. After the mixture was stirred for 6 h,
aqueous ammonia was added to adjust the pH of the mixture to 7, and
the mixture was extracted with CH2Cl2. The desired ligand L4 (0.7649 g,
3.97 mmol) was obtained as a white solid in 90.3% yield after purification
by column chromatography (silica gel, petroleum ether/ethyl acetate,
4:1). Mp: 130À132 °C. IR (KBr; cmÀ1): 3051, 2928, 1594, 1496, 1443,
1423, 1387, 1319, 1282, 848, 770, 739, 659. 1H NMR (400 MHz,
CDCl3): δ 8.12 (d, J = 8.4 Hz, 1H), 8.06 (d, J = 7.0 Hz, 1H), 7.94 (d, J =
7.1 Hz, 1H), 7.87 (d, J = 7.4 Hz, 1H), 7.61 (t, J = 7.5 Hz, 1H), 7.46 (d, J =
7.4 Hz, 1H), 7.37À7.31 (m, 3H), 3.64 (s, 3H, Me), 2.89 (q, J = 7.5 Hz,
2H, Et), 1.26 (t, J = 7.5 Hz, 3H, Et). 13C{1H} NMR (100 MHz, CDCl3):
δ 164.5 (C), 153.9 (C), 146.1 (C), 143.4 (C), 136.6 (C), 136.5 (CH),
133.0 (CH), 130.1 (CH), 129.8 (C), 126.8 (C), 125.5 (CH), 122.5
(CH), 121.9 (CH), 121.5 (CH), 120.0 (CH), 109.5 (CH), 32.2 (Me),
31.8 (Et), 13.5 (Et). Anal. Calcd for C19H17N3 (287.36): C, 79.41; H,
5.96; N, 14.62. Found: C, 79.66; H, 5.93; N, 14.55.
Synthesis of 2-Ethyl-8-(1-isopropylbenzimidazol-2-yl)quinoline
(L6). A solution of L3 (0.8 mg, 2.93 mmol) in 20 mL of acetone was
refluxed with 1.5 equiv of KOH (0.2461 mg, 4.4 mmol) for 3 h. After the
mixture was cooled to room temperature, 2-iodopropane (0.5967 g, 3.51
mmol) was added to the reaction mixture, which was stirred for 24 h at
refluxing temperature. The solvent was evaporated at reduced pressure
before water (20 mL) was added, and aqueous ammonia was added to
adjust the pH of the mixture to 7. Then the aqueous phase was extracted
with CH2Cl2 (4 Â 15 mL). The combined extract was dried over
anhydrous Na2SO4 and filtered; the solvent was finally evaporated at
reduced pressure. The desired compound L6 (0.2331 g, 0.74 mmol) was
obtained as a white solid in 25.1% yield after purification by column
chromatography (silica gel, petroleum ether/ethyl acetate, 2:1). Mp:
114 À 116 °C. IR (KBr; cmÀ1): 2971, 2931, 1606, 1577, 1436, 1377,
1280, 1156, 841. 1H NMR (400 MHz, CDCl3): δ 8.13 (d, J = 8.5 Hz,
1H), 7.94À7.90 (m, 2H), 7.87 (br, 1H), 7.69 (br, 1H), 7.59 (t, J = 7.5
Hz, 1H), 7.34À7.28 (m, 3H), 4.34 (sept, J = 6.8 Hz, 1H, iPr), 2.87 (q, J =
7.7 Hz, 2H, Et), 1.75 (br, 3H, iPr), 1.58 (br, 3H, iPr), 1.23 (t, J = 7.7 Hz,
3H, Et). 13C{1H} NMR (100 MHz, CDCl3): δ 164.8 (C), 153.0 (C),
146.5 (C), 144.4 (C), 136.4 (CH), 133.5 (C), 132.7 (CH), 130.7 (C),
129.9 (CH) 126.7 (C), 125.4 (CH), 121.9 (CH), 121.5 (CH), 121.3
(CH), 120.4 (CH), 112.1 (CH), 49.4 (iPr), 32.2 (Et), 21.2 (br, iPr), 13.8
(Et). Anal. Calcd for C21H21N3 (315.97): C, 79.97; H, 6.71; N, 13.32.
Found: C, 80.03; H, 6.64; N, 13.33.
Synthesis of 8-(1H-Benzimidazol-2-yl)-2-propylquinoline (L7).
Using the same procedure as for the synthesis of L3, L7 was obtained as a
white powder in a yield of 42.6%. Mp: 174 À 176 °C. IR (KBr; cmÀ1):
3048, 2953, 1614, 1524, 1499, 1435, 1396, 1306, 1278, 1186, 1131, 850,
787, 727, 656. 1H NMR (400 MHz, CDCl3): δ 13.84 (br, 1H, NH); 9.10
(d, J = 7.4 Hz, 1H); 8.17 (d, J = 8.0 Hz, 1H); 7.90À7.84 (m, 2H); 7.65
(t, J = 7.6 Hz, 1H); 7.60 (br, 1H); 7.39 (d, J = 8.4 Hz, 1H); 7.30À7.29
(m, 2H); 3.14 (t, J = 7.5 Hz, 2H, Pr); 2.05 (sext, 2H, Pr), 1.15 (t, J =
7.3 Hz, 3H, Pr). 13C{1H} NMR (100 MHz, CDCl3): δ 162.6 (C), 152.0
(C), 144.9 (C), 143.4 (C), 137.7 (CH), 134.2 (C), 130.4 (CH), 129.7
(CH), 127.4 (C), 126.2 (CH), 125.3 (C), 122.8 (CH), 122.3 (CH),
121.8 (CH), 119.5 (CH), 111.3 (CH), 41.1 (Pr), 22.3 (Pr), 14.0 (Pr).
Anal. Calcd for C19H17N3 (287.36): C, 79.41; H, 5.96; N, 14.62. Found:
C, 79.21; H, 5.92; N, 14.61.
Synthesis of 2-Propyl-8-(1-methylbenzimidazol-2-yl)quinoline (L8).
Using the same procedure as for the synthesis of L4, L8 was obtained as a
white powder in a yield of 87.6%. Mp: 131À133 °C. IR (KBr; cmÀ1):
3045, 2961, 2854, 1605, 1441, 1419, 1384, 1325, 1279, 848, 768, 737,
Synthesis of 2-Ethyl-8-(1-ethylbenzimidazol-2-yl)quinoline (L5). A
solution of L3 (0.8 g, 2.93 mmol) in 20 mL of acetone was refluxed with
1.5 equiv of KOH (0.2461 g, 4.4 mmol) for 3 h. After the mixture was
cooled to room temperature, iodoethane (0.5475 g, 3.51 mmol) was
added to the reaction mixture, which was stirred for 24 h at 40 °C. The
solvent was evaporated at reduced pressure before water (20 mL) was
added, and aqueous ammonia was added to adjust the pH of the mixture
to 7. Then the aqueous phase was extracted with CH2Cl2 (4 Â 15 mL).
The combined extract was dried over anhydrous Na2SO4 and filtered,
and the solvent was finally evaporated at reduced pressure. The desired
compound L5 (0.6271 g, 2.08 mmol) was obtained as a white solid in
71.1% yield after purification by column chromatography (silica gel,
1
659. H NMR (400 MHz, CDCl3): δ 8.12 (d, J = 8.4 Hz, 1H), 8.05
(d, J = 7.0 Hz, 1H), 7.94 (d, J = 8.1 Hz, 1H), 7.87 (d, J = 7.4 Hz, 1H), 7.61
(t, J = 7.6 Hz, 1H), 7.46 (d, J = 7.6 Hz, 1H), 7.37À7.30 (m, 3H), 3.63 (s,
3H, Me), 2.83 (t, J = 7.5 Hz, 2H, Pr), 1.73 (sext, 2H, Pr), 0.92 (t, J =
7.3 Hz, 3H, Pr). 13C{1H} NMR (100 MHz, CDCl3): δ 163.6 (C), 153.9
(C), 146.2 (C), 143.4 (C), 136.6 (C), 136.3 (CH), 133.1 (CH), 130.1
(CH), 129.8 (C), 126.8 (C), 125.5 (CH), 122.4 (CH), 121.9 (2 Â CH),
120.0 (CH), 109.6 (CH), 41.2 (Pr), 31.8 (Me), 22.7 (Pr), 14.1 (Pr).
Anal. Calcd for C20H19N3 (301.38): C, 79.70; H, 6.35; N, 13.94. Found:
C, 79.66; H, 6.53; N, 14.14.
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ARTICLE
Synthesis of 2-Propyl-8-(1-ethylbenzimidazol-2-yl)quinoline (L9).
Using the same procedure as for the synthesis of L5, L9 was obtained as a
white powder in a yield of 41.1%. Mp: 106À108 °C. IR (KBr; cmÀ1):
2958, 1606, 1449, 1426, 1389, 1271, 848, 768, 737, 659. 1H NMR (400
MHz, CDCl3): δ 8.12 (d, J = 8.4 Hz, 1H), 7.97 (d, J = 7.1 Hz, 1H), 7.94
(d, J = 8.4 Hz, 1H), 7.87 (d, J = 7.2 Hz, 1H), 7.60 (t, J = 7.4 Hz, 1H), 7.50
(d, J = 7.4 Hz, 1H), 7.36À7.30 (m, 3H), 4.10 (q, J = 7.3 Hz, 2H, Et), 2.82
(t, J = 7.6 Hz, 2H, Pr), 1.71 (sext, 2H, Pr), 1.25 (t, J = 7.3 Hz, 3H, Et),
0.90 (t, J = 7.1 Hz, 3H, Pr). 13C{1H} NMR (100 MHz, CDCl3): δ 163.7
(C), 153.2 (C), 146.3 (C), 143.8 (C), 136.3 (CH), 135.3 (C), 132.8
(CH), 130.3 (C), 130.0 (CH), 126.8 (C), 125.4 (CH), 122.3 (CH),
122.0 (CH), 121.8 (CH), 120.1 (CH), 110.0 (CH), 41.1 (Pr), 39.9 (Et),
22.7 (Pr), 15.0 (Et), 14.1 (Pr). Anal. Calcd for C21H21N3 (315.41): C,
79.97; H, 6.71; N, 13.32. Found: C, 79.99; H, 6.73; N, 13.28.
3H, Et). 13C{1H} NMR (100 MHz, CDCl3): δ 157.1 (C), 153.0 (C), 146.4
(C), 143.9 (C), 138.7 (C), 137.2 (CH), 135.4 (C), 133.4 (CH), 131.0 (C),
130.0 (CH), 129.8 (CH), 128.9 (2 Â CH), 127.5 (2 Â CH), 127.3 (C),
126.2 (CH), 122.4 (CH), 121.9 (CH), 120.2 (CH), 119.0 (CH), 110.1
(CH),40.0(Et),15.0(Et). Anal. CalcdforC24H19N3 (349.43): C, 82.49; H,
5.48; N, 12.03. Found: C, 82.21; H, 5.65; N, 11.84.
Synthesis of 2-Phenyl-8-(1-isopropylbenzimidazol-2-yl)quinoline
(L14). Using the same procedure as for the synthesis of L6, L14 was
obtained as a white powder in a yield of 55.3%. Mp: 161À163 °C. IR
(KBr; cmÀ1): 2927, 1611, 1568, 1452, 1376, 1281, 1157, 837, 768, 743,
696. 1H NMR (400 MHz, CDCl3): δ 8.31 (d, J = 8.7 Hz, 1H);
8.02À7.96 (m, 5H); 7.93À7.88 (m, 1H); 7.71À7.66 (m, 1H); 7.65
(t, J = 7.7 Hz, 1H); 7.38À7.31 (m, 5H); 4.34 (sept, 1H, J = 6.9 Hz, iPr);
1.53 (br, 3H, iPr), 1.41 (br, 3H, iPr). 13C{1H} NMR (100 MHz,
CDCl3): δ 157.3 (C), 153.0 (C), 146.9 (C), 144.5 (C), 138.7 (C), 137.1
(CH), 133.6 (C), 133.2 (CH), 131.4 (C), 129.9 (CH), 129.7 (CH),
128.8 (2 Â CH), 127.7 (2 Â CH), 127.2 (C), 126.1 (CH), 122.0, (CH),
121.6 (CH), 120.5 (CH), 119.2 (CH), 112.3 (CH), 49,5 (iPr), 20.9 (br,
iPr). Anal. Calcd for C25H21N3 (363.45): C, 82.61; H, 5.82; N, 11.56.
Found: C, 82.63; H, 5.94; N, 11.41.
Synthesis of 2-Propyl-8-(1-isopropylbenzimidazol-2-yl)quinoline
(L10). Using the same procedure as for the synthesis of L6, L10 was
obtained as a white powder in a yield of 23.3%. Mp: 118À120 °C. IR
(KBr; cmÀ1): 2958, 2926, 1607, 1576, 1497, 1436, 1379, 1281, 848, 768,
1
737, 659. H NMR (400 MHz, CDCl3): δ 8.13 (d, J = 8.4 Hz, 1H),
7.95À7.90 (m, 2H), 7.86 (br, 1H), 7.70 (br, 1H), 7.59 (t, J = 7.4 Hz,
1H), 7.34À7.29 (m, 3H), 4.34 (sept, 1H, J = 8.4 Hz, iPr), 2.82 (t, J = 7.7
Hz, 2H, Pr), 1.81 (br, 3H, iPr) 1.69 (sext, 2H, Pr), 1.44 (br, 3H, iPr),
0.91 (t, J = 7.3 Hz, 3H, Pr). 13C{1H} NMR (100 MHz, CDCl3): δ 163.8
(C), 153.1 (C), 146.7 (C), 144.4 (C), 136.3 (CH), 133.6 (C), 132.8
(CH), 130.7 (C), 129.9 (CH), 126.7 (C), 125.4 (CH), 122.0 (CH),
121.8 (CH), 121.6 (CH), 120.4 (CH), 112.1 (CH), 49.4 (iPr), 41.3
(Pr), 23.0 (Pr), 21.4 (br, iPr), 14.2 (Pr). Anal. Calcd for C22H23N3
(329.44): C, 80.21; H, 7.04; N, 12.76. Found: C, 80.23; H, 7.36;
N, 12.42.
Synthesis of 8-(1H-Benzimidazol-2-yl)-2-phenylquinoline (L11).
Using the same procedure as for the synthesis of L3, L11 was obtained
as a white powder in a yield of 32.0%. Mp: 173À174 °C. IR
(KBr; cmÀ1): 3059, 2923, 1600, 1563, 1489, 1446, 1420, 1399, 1324,
1278, 1132, 843, 768, 739, 727, 665. 1H NMR (400 MHz, CDCl3): δ
13.72 (br, 1H, NH); 9.15 (d, J = 7.4 Hz, 1H); 8.36 (d, J = 8.5 Hz, 1H);
8.12 (d, J = 7.8 Hz, 2H); 7.98À7.91 (m, 2H); 7.90 (d, J = 7.4 Hz, 1H);
7.72 (t, J = 7.6 Hz, 1H); 7.66 (t, J = 7.5 Hz, 2H); 7.61 (d, J = 6.9 Hz, 1H);
7.56 (d, J = 7.3 Hz, 1H); 7.35À7.25 (m, 2H). 13C{1H} NMR (100 MHz,
CDCl3): δ 157.7 (C), 151.7 (C), 145.2 (C), 143.4 (C), 139.8 (C), 138.5
(CH), 134.2 (C), 130.8 (CH), 130.0 (CH), 129.7 (CH), 129.4 (2 Â
CH), 127.8 (2 Â CH), 127.7 (C), 126.8 (CH), 125.9 (C), 122.9 (CH),
122.4 (CH), 119.6 (CH), 119.5 (CH), 111.3 (CH). Anal. Calcd for
C22H15N3 (321.37): C, 82.22; H, 4.70; N, 13.08. Found: C, 82.09; H,
4.93; N, 12.65.
4.3. Synthesis of Iron Complexes C1ÀC14. The iron com-
plexes C1ÀC14 were synthesized by the reaction of FeCl2 4H2O with
3
the corresponding ligands in ethanol. A typical synthetic procedure for
C1 can be described as follows. To a mixture of ligand L1 (77.7 mg,
0.3 mmol) and FeCl2 4H2O (60.1 mg, 0.3 mmol) was added ethanol
3
(4 mL) at room temperature. The solution turned orange immediately.
The reaction mixture was stirred for 6 h, and absolute diethyl ether was
added. The resulting precipitate was filtered, washed with diethyl ether,
and dried in a vacuum to furnish the pure product as an orange powder
(108.3 mg, 0.281 mmol) in 94.3% yield. IR (KBr; cmÀ1): 3483, 3057,
1613, 1569, 1513, 1432, 1409, 843, 773, 741. Anal. Calcd for C17H13Cl2FeN3
(386.06): C, 52.89; H, 3.39; N, 10.88. Found: C, 52.95; H, 3.17; N, 10.66.
Complex C2 was obtained as an orange powder in 89.1% yield. IR
(KBr; cmÀ1): 3059, 1613, 1531, 1569, 1514, 1454, 1404, 850, 773, 749.
Anal. Calcd for C18H15Cl2FeN3 (400.08): C, 54.04; H, 3.78; N, 10.50.
Found: C, 54.33; H, 3.59; N, 10.36.
Complex C3 was obtained as an orange powder in 89.9% yield. IR
(KBr; cmÀ1): 3195, 2984, 1607, 1568, 1513, 1459, 1411, 1325, 1202,
1149, 846, 768, 741, 681. Anal. Calcd for C18H15Cl2FeN3 (400.08): C,
54.04; H, 3.78; N, 10.50. Found: C, 53.67; H, 3.71; N, 10.28.
Complex C4 was obtained as an orange powder in 83.6% yield. IR
(KBr; cmÀ1): 2969, 1607, 1579, 1477, 1445, 1398, 1331, 1208, 1049,
848, 755. Anal. Calcd for C19H17Cl2FeN3 (414.11): C, 55.11; H, 4.14;
N, 10.15. Found: C, 55.01; H, 4.04; N, 9.98.
Synthesis of 2-Phenyl-8-(1-methylbenzimidazol-2-yl)quinoline (L12).
Using the same procedure as for the synthesis of L4, L12 was obtained as a
white powder in a yield of 96.1%. Mp: 221À223 °C. IR (KBr; cmÀ1): 3048,
2930, 1612, 1588, 1570, 1482, 1455, 1423, 1387, 1324, 1280, 844, 766, 737,
661. 1H NMR (400 MHz, CDCl3): δ 8.32 (d, J = 8.6 Hz, 1H); 8.13 (d, J =
7.0 Hz, 1H); 8.08À7.98 (m, 4H); 7.91 (d, J = 7.2 Hz, 1H); 7.67 (t, J =
7.6 Hz, 1H); 7.49 (d, J = 7.4 Hz, 1H); 7.43À7.32 (m, 5H); 3.67 (s, 3H,
Me). 13C{1H} NMR (100 MHz, CDCl3): δ 157.0 (C), 153.7 (C), 146.3
(C), 143.6 (C), 138.8 (C), 137.3 (CH), 136.7 (C), 133.7 (CH), 130.5 (C),
130.1 (CH), 129.8 (CH), 129.0 (2 Â CH), 127.3 (2 Â CH), 127.1 (C),
126.3 (CH), 122.6 (CH), 122.1 (CH), 120.1 (CH), 118.8 (CH), 109.7
(CH), 32.0 (Me). Anal. Calcd for C23H17N3 (335.40): C, 82.36; H, 5.11;
N, 12.53. Found: C, 82.18; H, 5.23; N, 12.39.
Synthesis of 2-Phenyl-8-(1-ethylbenzimidazol-2-yl)quinoline (L13).
Using the same procedure as for the synthesis of L5, L13 was obtained as
a white powder in a yield of 88.3%. Mp: 131À133 °C. IR (KBr; cmÀ1):
3053, 2927, 1598, 1566, 1451, 1397, 1273, 1011, 842, 768, 741, 697. 1H
NMR (400 MHz, CDCl3): δ 8.31 (d, J = 8.7 Hz, 1H); 8.06À7.94 (m,
5H); 7.91 (br, 1H); 7.66 (t, J = 7.6 Hz, 1H); 7.53 (d, J = 8.0 Hz, 1H);
7.40À7.30 (m, 5H); 4.17 (q, J = 7.2 Hz, 2H, Et); 1.18 (t, J = 7.2 Hz,
Complex C5 was obtained as an orange powder in 81.2% yield. IR
(KBr; cmÀ1): 2973, 1583, 1498, 1448, 1421, 1334, 1230, 1203, 1052,
842, 750. Anal. Calcd for C20H19Cl2FeN3 (428.14): C, 56.11; H, 4.47;
N, 9.81. Found: C, 56.17; H, 4.41; N, 9.65.
Complex C6 was obtained as an orange powder in 80.9% yield. IR
(KBr; cmÀ1): 2969, 1607, 1579, 1477, 1445, 1398, 1331, 1208, 1149,
846, 768, 741, 681. Anal. Calcd for C21H21Cl2FeN3 (442.16): C, 57.04;
H, 4.79; N, 9.50. Found: C, 57.40; H, 4.61; N, 9.12.
Complex C7 was obtained as an orange powder in 81.6% yield. IR
(KBr; cmÀ1): 2960, 1607, 1570, 1512, 1458, 1408, 1327, 1148, 839, 808,
750, 680. Anal. Calcd for C19H17Cl2FeN3 (414.11): C, 55.11; H, 4.14;
N, 10.15. Found: C, 54.96; H, 4.15; N, 9.87.
Complex C8 was obtained as a pink powder in 80.3% yield. IR
(KBr; cmÀ1): 2952, 1601, 1569, 1501, 1461, 1391, 1329, 1103, 855, 781,
752, 680. Anal. Calcd for C20H19Cl2FeN3 1/3H2O: C, 55.33; H, 4.57;
3
N, 9.68. Found: C, 55.57; H, 4.41; N, 9.64.
Complex C9 was obtained as a yellow powder in 88.7% yield. IR
(KBr; cmÀ1): 2960, 1604, 1574, 1500, 1416, 1336, 1088, 844, 781, 749,
661. Anal. Calcd for C21H21Cl2FeN3 (442.16): C, 57.04; H, 4.79; N,
9.50. Found: C, 57.43; H, 4.61; N, 9.33.
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Table 3. Crystal Data and Structure Refinement for L5, C2, and C7
L5
C2
C7
empirical formula
fw
C
20H19N3
C18H15Cl2FeN3
400.08
C19H17Cl2FeN3
414.11
301.38
cryst color
temperature (K)
wavelength (Å)
cryst syst
space group
a (Å)
colorless
orange
yellow
173(2)
173(2)
173(2)
0.71073
0.71073
0.71073
monoclinic
C2/c
orthorhombic
P2(1)2(1)2(1)
6.8148(14)
11.667(2)
monoclinic
P21/n
7.2193(1)
14.916(3)
15.255(3)
15.909(3)
94.98(3)
3606.5(13)
8
b (Å)
17.200(3)
c (Å)
20.822(4)
13.681(3)
β (deg)
volume (Å3)
90
101.78(3)
1655.5(6)
1663.0(6)
Z
4
4
Dcalc (Mg mÀ3
)
1.209
1.598
1.525
μ (mmÀ1
)
0.073
1.232
1.139
F(000)
640
816
1696
cryst size (mm)
θ range (deg)
limiting indices
0.80 Â 0.80 Â 30
2.62À27.48
À8 e h e 8,
À12 e k e 15,
À26 e l e 27
99.6 (θ = 27.48)
0.0373
0.30 Â 0.25 Â 0.20
2.81À25.01
À8 e h e 8,
À20 e k e 20,
À16 e l e 16
96.9 (θ = 25.01)
0.0651
0.18 Â 0.0.08 Â 0.07
1.91À30.03
À17 e h e 20,
À21 e k e 21,
À22 e l e 21
99.0 (θ = 30.03)
0.0449
completeness to θ (%)
R(int)
absorp corr
empirical
empirical
empirical
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and hole (e ÅÀ3
3786/32/227
1.131
2850/0/217
1.277
5211/0/230
1.156
R1 = 0.0560, wR2 = 0.1376
R1 = 0.0590, wR2 = 0.1400
0.165 and À0.225
R1 = 0.1143, wR2 = 0.1937
R1 = 0.1579, wR2 = 0.2096
0.543 and À0.446
R1 = 0.0568, wR2 = 0.1102
R1 = 0.0643, wR2 = 0.1142
0.476 and À0.401
)
Complex C10 was obtained as a yellow powder in 79.9% yield. IR
(KBr; cmÀ1): 2961, 1607, 1512, 1408, 1327, 1148, 1079, 841, 748, 681.
Anal. Calcd for C22H23Cl2FeN3 (456.19): C, 57.92; H, 5.08; N, 9.21.
Found: C, 57.93; H, 5.01; N,9.09 .
Complex C11 was obtained as a yellow powder in 92.3% yield. IR
(KBr; cmÀ1): 3060, 1590, 1449, 1405, 1283, 1180, 1052, 850, 767, 748,
689. Anal. Calcd for C22H15Cl2FeN3 (448.13): C, 58.96; H, 3.37; N,
9.38. Found: C, 58.76; H, 3.71; N, 9.58.
Complex C12 was obtained as a yellow powder in 92.1% yield. IR
(KBr; cmÀ1): 3060, 1595, 1475, 1451, 1401, 1292, 843, 749, 696, 665.
Anal. Calcd for C23H17Cl2FeN3 (462.15): C, 59.77; H, 3.71; N, 9.09.
Found: C, 59.61; H, 3.90; N, 9.23.
Complex C13 was obtained as a yellow powder in 90.2% yield. IR
(KBr; cmÀ1): 3057, 2980, 2932, 1599, 1472, 1451, 1415, 1280, 1245
1017, 847, 769, 736, 695, 665. Anal. Calcd for C24H19Cl2FeN3 (476.18):
C, 60.54; H, 4.02; N, 8.82. Found: C, 60.76; H, 4.31; N, 9.05.
Complex C14 was obtained as a yellow powder in 86.3% yield. IR
(KBr; cmÀ1): 3052, 2964, 1603, 1490, 1421, 1326, 952, 842, 759, 729,
692, 657. Anal. Calcd for C25H21Cl2FeN3 (490.21): C, 61.25; H, 4.32;
N, 8.57. Found: C, 61.21; H, 4.01; N, 8.92.
mixture was magnetically stirred for 30 min, the ethylene remaining was
purged after the reaction, and the mixture was cooled to room
temperature. Then the residual reaction solution was quenched with
5% hydrochloric acid ethanol. The precipitated polymer was collected by
filtration, adequately washed with ethanol and water, and then dried in a
vacuum until constant weight.
4.5. X-ray Crystallographic Studies. Single-crystal X-ray dif-
fraction studies for L5, C2, and C7 were carried out on a Rigaku RAXIS
Rapid IP diffractometer with graphite-monochromated Mo KR radia-
tion (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 non-hydrogen atoms were refined anisotropi-
cally. The H atom on the N atom of benzoimidazole in C7 was calculated
from a difference Fourier diagram. Other hydrogen atoms were placed in
calculated positions. Structure solution and refinement were performed
by using the SHELXL-97 package.25 Crystal data and processing
parameters for L5, C2, and C7 are summarized in Table 3.
4.4. Procedure for Ethylene Polymerization. Ethylene poly-
merization was performed in a stainless steel autoclave (100 mL scale). A
typical reaction procedure was as follows. Catalyst (2 μmol), toluene
(40 mL), and the required amount of MAO (1.46 mol/L solution in
toluene) were added into the autoclave in the drybox. The reactor was
sealed and moved out of the drybox. At the reaction temperature, the
reaction apparatus was then immediately pressurized to 30 atm. The
’ ASSOCIATED CONTENT
S
Supporting Information. Crystal data and processing
b
parameters for compound L5 and complexes C2 and C7, a
CIF file giving X-ray crystal structural data, and NMR sprectra of
three representative polyethylenes. This material is available free
of charge via the Internet at http://pubs.acs.org.
3664
dx.doi.org/10.1021/om200338b |Organometallics 2011, 30, 3658–3665

Organometallics
ARTICLE
’ AUTHOR INFORMATION
Organometallics 2009, 28, 5889. (k) Raucoules, R.; Bruin, T.; Raybaud,
P.; Adamo, C. Organometallics 2009, 28, 5358. (l) Bryliakov, K. P.; Talsi,
E. P.; Semikolenova, N. V.; Zakharov, V. A. Organometallics 2009,
28, 3225. (m) Bowman, A. C.; Milsmann, C.; Atienza, C. C. H.;
Lobkovsky, E.; Wieghardt, K.; Chirik, P. J. J. Am. Chem. Soc. 2010,
132, 1676. (n) Bowman, A. C.; Milsmann, C.; Bill, E.; Lobkovsky, E.;
Weyherm€uller, T.; Wieghardt, K.; Chirik, P. J. Inorg. Chem. 2010,
49, 6110. (o) Tondreau, A. M.; Milsmann, C.; Patrick, A. D.; Hoyt,
H. M.; Lobkovsky, E.; Wieghardt, K.; Chirik, P. J. J. Am. Chem. Soc. 2010,
132, 15046. (p) Atienza, C. C. H.; Bowman, A. C.; Lobkovsky, E.; Chirik,
P. J. J. Am. Chem. Soc. 2010, 132, 16343.
Corresponding Author
*Tel: +86-10-62557955. Fax: +86-10-62618239. E-mail: whsun@
iccas.ac.cn.
’ ACKNOWLEDGMENT
This work is supported by MOST 863 program No.
2009AA033601.
(9) (a) Yu, J.; Liu, H.; Zhang, W.; Hao, X.; Sun, W.-H. Chem.
Commun. 2011, 47, 3257. (b) Liu, F.-S.; Hu, H.-B.; Xu, Y.; Guo, L.-H.;
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Macromolecules 2009, 42, 7789. (c) Guo, L.-H.; Gao, H.-Y.; Zhang, L.;
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