Iron(II) and cobalt(II) complexes bearing 8-(1-aryliminoethylidene) quinaldines: Synthesis, characterization and ethylene dimerization behavior

Article abstract of DOI:10.1016/j.jorganchem.2011.03.039

The series of bidentate N^N iron(II) and cobalt(II) complexes containing 8-(1-aryliminoethylidene) quinaldine derived ligands, 8-[2,6-(R ¹)₂-4-R²-C₆H₂NC (Me)]-2-Me-C₁₀H₅N, were synthesized and characterized by elemental and spectroscopic techniques. The molecular structures of Co1 (R ¹ = Me, R² = H), Co3 (R¹ = ⁱPr, R² = H) and Co4 (R¹ = R² = Me) were confirmed as the distorted tetrahedral by single crystal X-ray diffraction. On treatment with modified methylaluminoxane (MMAO), these complexes exhibited good catalytic activities of up to 5.71 × 10⁵ g mol^-1(Fe) h ^-1 for the ethylene dimerization at 30 °C under 10 atm of ethylene, in which iron pre-catalysts produced butenes with a high selectivity for α-butene. The correlation between metal complexes, catalytic activities and the product formed were investigated under various reaction parameters.

Full text of DOI:10.1016/j.jorganchem.2011.03.039

Journal of Organometallic Chemistry 696 (2011) 2594e2599
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Iron(II) and cobalt(II) complexes bearing 8-(1-aryliminoethylidene) quinaldines:
Synthesis, characterization and ethylene dimerization behavior
,
a
a
a,c,
Shengju Song a, Tianpengfei Xiao a, Carl Redshaw b , Xiang Hao , Fosong Wang , Wen-Hua Sun
*
**
a Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
b School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
c State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
The series of bidentate N^N iron(II) and cobalt(II) complexes containing 8-(1-aryliminoethylidene)
quinaldine derived ligands, 8-[2,6-(R1)2-4-R2-C6H2N]C (Me)]-2-Me-C10H5N, were synthesized and
characterized by elemental and spectroscopic techniques. The molecular structures of Co1
(R1 ¼ Me, R2 ¼ H), Co3 (R1 ¼ iPr, R2 ¼ H) and Co4 (R1 ¼ R2 ¼ Me) were confirmed as the distorted
tetrahedral by single crystal X-ray diffraction. On treatment with modified methylaluminoxane (MMAO),
these complexes exhibited good catalytic activities of up to 5.71 ꢀ 105 g molꢁ1(Fe) hꢁ1 for the ethylene
dimerization at 30 ꢂC under 10 atm of ethylene, in which iron pre-catalysts produced butenes with a high
Received 15 February 2011
Received in revised form
20 March 2011
Accepted 29 March 2011
Keywords:
8-(1-Aryliminoethylidene)quinaldine
Iron(II) complexes
Cobalt(II) complexes
Ethylene dimerization
selectivity for
a-butene. The correlation between metal complexes, catalytic activities and the product
formed were investigated under various reaction parameters.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
activities for ethylene polymerization and oligomerization. These
systems utilize newly developed ligands (Scheme 1) such as
2-imino-1,10-phenanthrolines (B) [23e30], 2-(benzoimidazolyl)-
6-iminopyridines (C) [31,32], 2-quinoxalinyl-6-iminopyridines (D)
[33,34], 2-(benzimidazol-2-yl)-1,10- phenanthrolines (E) [35,36],
2-methyl-2,4-bis(6-iminopyridin-2-yl)-1H-1,5- benzodiazepines
(F) [37,38], N-((pyridin-2-yl)methylene)-quinolin-8-amine (G) [39],
2-benzoxazolyl-6-[1-(arylimino)ethyl]pyridines (H) [40], 2-oxazo-
line- or benzoxazole-1,10-phenanthrolines (I) [41], 2-(1-arylimi-
nopropylidene)quinolines (J) [42], 2,8-bis(imino)quinolines (K)
[43] and 2-[1-(2,6-dibenzhydryl-4-methylphenylimino)ethyl]-
6-[1-(arylimino)ethyl]pyridines [44]. Moreover, a number of the
Fe(II) and Co(II) catalysts were capable of ethylene oligomerization
As major industrial reactants, a-olefins are widely used in the
preparation of detergents, lubricants, plasticizers, oil-field chem-
icals, and monomers for co-polymerizations. The ever increasing
demand of the
on year, and as a consequence, there is increasing interest in
developing new catalysts and processes to produce -olefins in
a-olefin industry has been growing at about 5% year
a
both academic and industrial settings. In the past decade, signifi-
cant progress has been made in the development of late transition
metal catalysts for the oligomerization of ethylene. Since the
discovery that 2,6-bis(arylimino)pyridine ligands (A in Scheme 1)
can impart late transition metals, and in particular iron, with high
activities for ethylene oligomerization and polymerization [1e5],
a great deal of interest has focused on catalyst modification and
design [6e16]. In devising late-transition metal complexes as
catalysts for ethylene polymerization and oligomerization, a few
models of iron and cobalt catalysts were reported [17e22]. Our
group has recently reported a series of complexes with good to high
with high activities and high selectivity of a-olefins, and can thus be
considered as promising catalysts for industrial consideration. As
a consequence, derivatives have been synthesized and further
investigations conducted to evaluate for better performance,
primarily via controlling steric and electronic influences of the
ligand substituents. On the whole, those existing catalytic models
of Fe(II) and Co(II) complexes have been coordinated with ligands
centered via an N-heteroaromatic ring. We have now turned our
attention to ligands containing a Schiff-base moiety at the center in
combination with N-heteroaromatic rings.
A series of 8-(1-aryliminoethylidene) quinaldinylnickel dihalides
were synthesized and found to perform with high catalytic activity
for the oligomerization of ethylene [45]. Following on from this, the
Fe(II) and Co(II) analogs were synthesized and characterized. The
* Corresponding author. Tel.: þ44 1603 593137; fax: þ44 1603 592003.
** Corresponding author. Key Laboratory of Engineering Plastics and Beijing
National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, China. Tel.: þ86 10 62557955; fax: þ86
1062618239.
E-mail addresses: carl.redshaw@uea.ac.uk (C. Redshaw), whsun@iccas.ac.cn
(W.-H. Sun).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.03.039

S. Song et al. / Journal of Organometallic Chemistry 696 (2011) 2594e2599
2595
R
N
N
N
N
N
N
R2
N
N
N
R1
N
N
Ar
N
N
N
Ar
Ar
Ar
Ar
C
B
D
A
N
N
R2
N
N
R2
N
N
N
NH
R1
N
N
O
Ar
N
Ar
N
R1
F
G
E
Et
O
N
N
N
N
N
N
N
N
N
R2
N
N
Ar
R2
Ar
Ar
R1
Ar
J
H
I
K
Scheme 1. Previously used ligands.
catalytic investigation showed that these Fe(II) complexes could
dimerize ethylene to afford butanes in higher than 95% yields with
imino nitrogen atom and the metal cation. The unambigious struc-
tures were confirmed by single-crystal X-ray diffraction analysis.
a good selectivity for a-olefins. Herein, the synthesis and charac-
terization of the title complexes are reported and the catalytic
properties for ethylene dimerization are investigated and discussed
in detail.
2.2. Crystal structures
Single crystals of complexes Co1, Co3 and Co4 suitable for X-ray
diffraction analysis were obtained by slow diffusion of diethyl ether
into methanol solutions. The crystal structures are shown in
Figs. 1e3, and selected bond lengths and angles are collected in
Table 1.
2. Results and discussion
2.1. Synthesis and characterization of complexes
In the structure of Co1, the geometry around the cobalt center
can be described as distorted tetrahedral, in which the cobalt atom
is coordinated by one bidentate NˆN ligand and two chlorine atoms.
The quinoline plane with the aryl ring makes a dihedral angle of
79.01ꢂ and the cobalt center slightly deviates by 0.143Å from the
quinoline plane. Meanwhile, the quinoline plane with the aryl ring
makes dihedral angles of 59.31ꢂ and 81.88ꢂ in Co3 and Co4,
respectively. The slight differences of bond distances and angles
around the cobalt center were caused by the presence of different
substituents on the ligands, which also affected the catalytic
behavior of the cobalt complexes.
A series of 8-(1-aryliminoethylidene)quinaldines (L1eL5) were
prepared using our previous reported procedures [45]. The iron(II)
and cobalt complexes Fe1eFe5 and Co1eCo5 were readily prepared
by mixing the corresponding ligand and one equivalent of
FeCl2$4H2O or CoCl2 in ethanol at room temperature under nitrogen
(Scheme 2). The resulting complexes were precipitated from the
reaction solution and separated as red, yellow, or green air-stable
powders. All the complexes were characterized by FT-IR spectra
and elemental analysis. In the IR spectra, the stretching vibration
bands of the C]N of these iron(II) and cobalt(II) complexes
(1609e1625 cmꢁ1) shifted to lower wave number and the peak
intensity was greatly reduced, as compared to the corresponding
ligands (1635e1656 cmꢁ1), indicative of coordination between the
FeCl2
or CoCl2
R1
R1
N
N
N
N
ethanol
M
Cl
R2
R1
R2
Cl R1
R1
R2
Et i-Pr Me
Et
Me
Me
H
H
Me
H
L1
L2
L3
L4
L5
M = Fe Fe1 Fe2 Fe3 Fe4 Fe5
M = Co
Co1 Co2
Co3 Co4 Co5
Fig. 1. Molecular structure of Co1. Thermal ellipsoids are shown at the 30% probability
Scheme 2. Synthetic procedure.
level. Hydrogen atoms have been omitted for clarity.

2596
S. Song et al. / Journal of Organometallic Chemistry 696 (2011) 2594e2599
Table 1
Selected bond lengths(Å) and angles(ꢂ) for Co1, Co3 and Co4.
Co1
Co3
Co4
2.021(3)
1.996(3)
2.2381(14)
2.2596(12)
1.342(5)
1.388(5)
1.302(5)
1.452(5)
Bond lengths (Å)
Co(1)eN(1)
Co(1)eN(2)
Co(1)eCl(1)
Co(1)eCl(2)
N(1)eC(1)
N(1)eC(10)
N(2)eC(11)
N(2)eC(13)
2.025(3)
1.997(3)
2.2421(14)
2.2443(13)
1.350(5)
1.376(5)
1.290(5)
1.456(5)
2.0398(19)
2.0012(19)
2.2056(8)
2.2309(9)
1.338(3)
1.380(3)
1.287(3)
1.451(3)
Bond angles(ꢂ)
N(2)eCo(1)eN(1)
N(2)eCo(1)eCl(1)
N(1)eCo(1)eCl(1)
N(2)eCo(1)eCl(2)
N(1)eCo(1)eCl(2)
Cl(1)eCo(1)eCl(2)
C(1)eN(1)eC(10)
C(1)eN(1)eCo(1)
C(10)eN(1)eCo(1)
C(11)eN(2)eC(13)
C(11)eN(2)eCo(1)
C(13)eN(2)eCo(1)
94.25(14)
107.59(11)
115.62(11)
113.57(11)
111.38(10)
113.03(5)
120.0(3)
117.5(3)
122.3(3)
121.1(4)
126.9(3)
90.76(7)
109.31(6)
122.64(6)
114.15(6)
103.37(6)
114.56(3)
120.2(2)
120.89(16)
113.44(14)
121.19(18)
122.84(15)
115.97(14)
95.75(14)
114.91(11)
110.24(11)
109.64(10)
113.06(10)
112.26(5)
119.5(3)
117.2(3)
123.1(3)
119.6(3)
125.8(3)
Fig. 2. Molecular structure of Co3. Thermal ellipsoids are shown at the 30% probability
level. Hydrogen atoms have been omitted for clarity.
2.3. Reactions with ethylene
2.3.1. Ethylene dimerization by iron complexes
112.0(3)
114.6(2)
The influence of various alkylaluminium reagents such as
methylaluminoxane (MAO), modified methylaluminoxane (MMAO)
and diethylaluminium chloride (Et2AlCl) as co-catalysts was eval-
uated for ethylene activation by Fe3. The results are summarized in
Table 2. The catalytic system Fe3/MMAO exhibited highest activi-
ties, whilst the systems Fe3/Et2AlCl or MAO showed no activity.
Herein, MMAO as co-catalyst was further explored.
The influence of reactionparameters such as the Al/Fe molar ratio
and the reaction temperature on the ethylene dimerization activity
was investigated (Table 2). For the iron complex Fe3, the enhance-
ment of the Al/Fe molar ratio from 1000 to 1500 resulted in an
increase in the catalytic activity (entries 3e5, Table 2), which may be
attributed to the fact that the MMAO scavenged any adventitious
water and impurities present in the solvent at low Al/Fe ratios, and
the iron complex required more co-catalyst to be activated. Further
increasing the molar ratio to 3500 resulted in decreased activities
with the optimum condition using an Al/Fe ratio of 1500. This
observation could be traced to the increasing amount of isobutyl
groups present, which come from the MMAO, resulting in the
generated species hindering the insertion reaction of ethylene due
to increased steric bulk [31,46,47]. Meanwhile, it is noteworthy that
in productivity (entries 5 and 10e12 in Table 2), suggesting that the
active centers are thermally unstable [48].
The nature of the ligands present has a large influence on the
catalyst performance. To compare the influence of the ligand
environment on the catalytic behavior of the iron pre-catalysts, all
iron pre-catalysts Fe1eFe5 were investigated under optimum
reaction condition of molar ratio MMAO/Fe at 1500:1, 30 ꢂC and
10 atm ethylene (Table 2). The catalytic activities of the iron
complexes were significantly affected by the ligand environments,
and an activity order of Fe3 > Fe5 > Fe4 > Fe2 > Fe1 was observed.
The steric effects of ligands played a major role, especially
substituents at the ortho-position of the N-bound aryl group. The
bulkier the substituents, the higher the activity observed, which
was in line with observations for the iron pre-catalysts ligated
by 2-(1-methyl-2-benzimidazolyl)-6-(1-(arylimino)ethyl)pyridines
[31] and 2-(1H-2-benzimidazolyl)-6-(1-(arylimino)ethyl) pyridines
[49]. For pre-catalysts with less bulky substituents, the iron center
was more exposed not only to ethylene but also to other impurities,
the a-C4 selectivity of Fe3 decreased slightly with increasing Al/Fe
molar ratio. Notably, for the complex Fe3, the varied amounts of
co-catalyst showed no clear impact on the proportion of the C4
component in the products. An Al/Fe ratio of 1500 appeared as
a good trade-off between the activity and selectivity. Elevating the
reaction temperature from 30 ꢂC to 60 ꢂC resulted in a large decrease
Table 2
Ethylene dimerization with pre-catalysts Fe1eFe5a
Entry T/ꢂC Co-cat. Cat. Al/Fe Activityb Oligomer distributionc (%)
a
-C4
C4/SC
C6/SC
1
2
3
4
5
6
7
8
30
30
30
30
30
30
30
30
30
40
50
60
30
30
30
30
30
MAO
Et2AlCl Fe3
Fe3 1000
200
e
e
e
e
e
e
e
e
MMAO Fe3 1000 1.18
MMAO Fe3 1200 3.01
MMAO Fe3 1500 5.71
MMAO Fe3 2000 5.51
MMAO Fe3 2500 4.01
MMAO Fe3 3000 3.83
MMAO Fe3 3500 3.09
MMAO Fe3 1500 4.64
MMAO Fe3 1500 3.52
MMAO Fe3 1500 0.78
MMAO Fe1 1500 4.37
MMAO Fe2 1500 4.77
MMAO Fe3 1500 5.71
MMAO Fe4 1500 4.94
MMAO Fe5 1500 4.97
93.6
99.2
99.1
97.5
97.2
99.6
100
99.6
96.6
95.7
96.8
97.7
97.8
97.5
99.1
98.5
0.8
0.9
2.5
2.8
0.4
e
99.0
99.6
98.5
98.8
100
9
97.2
95.5
96.4
94.6
99.1
98.9
99.6
98.2
99.3
0.4
3.2
4.3
3.2
2.3
2.2
2.5
0.9
1.5
10
11
12
13
14
15
16
17
a
Conditions: 5
mmol Fe, 10 atm ethylene, 30 min, 100 mL toluene.
b
c
Fig. 3. Molecular structure of Co4. Thermal ellipsoids are shown at the 30% probability
level. Hydrogen atoms have been omitted for clarity.
105 g,molꢁ1(Fe),hꢁ1
.
Determined by GC; SC denotes the total amounts of oligomers.

S. Song et al. / Journal of Organometallic Chemistry 696 (2011) 2594e2599
2597
Table 3
in Table 2), with the activity order as Fe4 > Fe1 and Fe5 > Fe2. Such
phenomena were also observed for iron pre-catalysts ligated by
2-quinoxalinyl-6-iminopyridines [33] and 2-(1-isopropyl-2-benzi-
midazolyl)-6-(1-(arylimino)ethyl)pyridines [50].
Ethylene dimerization with pre-catalysts Co1eCo5a
Entry T/oC Co-catalyst Cat. Al/Co Activityb Oligomer distributionc (%)
P
P
a
eC4
C4/
C
C6/
C
1
2
3
4
5
6
7
8
20
20
20
20
20
20
20
20
20
20
30
40
50
20
20
20
20
20
MAO
Co3 1000 0.24
Co3 200 0.36
Co3 1000 2.01
Co3 1500 2.40
Co3 2000 3.21
Co3 2250 4.26
Co3 2500 4.89
Co3 2750 3.66
Co3 3000 3.19
Co3 3500 2.15
Co3 2500 3.88
Co3 2500 2.20
Co3 2500 1.97
Co1 2500 3.03
Co2 2500 3.34
Co3 2500 4.89
Co4 2500 3.07
Co5 2500 3.56
92.0
50.3
43.2
45.2
63.0
51.2
59.9
50.3
50.3
53.0
53.3
68.6
80.4
58.4
57.2
59.9
57.6
56.5
76.8
98.2
92.0
98.5
98.9
98.8
98.4
98.6
98.7
94.6
98.9
98.7
98.3
98.2
96.5
98.4
98.2
97.2
23.2
1.8
8.0
1.5
1.1
1.2
1.6
1.4
2.3
1.6
1.1
1.3
1.7
1.8
3.5
1.6
1.8
2.8
2.3.2. Ethylene dimerization by cobalt complexes
Et2AlCl
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
In a similar procedure, complex Co3 was used to explore suitable
co-catalysts (entries 1e3 in Table 3) for optimum dimerization
conditions. The Co3/MAO catalytic system displayed low catalytic
activities for ethylene dimerization with high selectivity for butanes
at 10 atm of ethylene pressure. In the presence of MMAO, the higher
9
activity was obtained, but with lower selectivity for a-olefins.
10
11
12
13
14
15
16
17
18
The catalytic system Co3/MMAO was typically investigated with
varying reaction conditions. When the Al/Co molar ratio of Co3 was
enhanced from 1000 to 3500 (entries 3e10 in Table 3), the
optimum activity was observed at 2500, meanwhile the selectivity
for a-butene was relatively lower. As the ethylene dimerization is
a highly exothermic reaction, the reaction temperature significantly
affects the catalytic activity. With increasing reaction temperature,
the catalytic activity gradually decreased, which may be attributed
to the decomposition of the active sites and lower ethylene solu-
bility at higher temperature (entries 7, 11e13 in Table 3). However,
a
Conditions: 5
mmol Co, 10 atm ethylene, 30 min, 100 mL toluene.
b
c
105 g,molꢁ1(Co),hꢁ1
.
Determined by GC; SC denotes the total amounts of oligomers.
the selectivity for
a-olefins showed an enhancement, whilst the
which resulted in the deactivation of the active species. In addition,
bulkier substituents might be helpful due to their enhanced solu-
bility properties. Introducing one methyl group at the para-position
of the aryl group led to a slightly higher activity (entries 16 and 17
proportion of C4 was only slightly affected. Complex Co3 exhibited
an activity of 4.89 ꢀ 105 g molꢁ1(Co) hꢁ1 at the Al/Co molar ratio of
2500:1 and 20 ꢂC under 10 atm of ethylene pressure.
In a similar manner to the iron complexes, ethylene dimeriza-
tion by Co1eCo5/MMAO systems was investigated under optimum
condition (Al/Co molar ratio of 2500:1 at 20 ꢂC). In general, for
these cobalt systems, relatively lower activities were exhibited with
lower selectivity for
(entries 14e18 in Table 3). The order the activities observed for the
cobalt pre-catalysts was consistent with the iron analogs above.
Table 4
Crystal data and structure refinement for pre-catalysts Co1, Co3 and Co4.
Co1
Co3
Co4
a-butene compared to their iron analogs
Cryst color
Empirical formula
fw
Green
Green
Green
C20H20Cl2CoN2
418.21
173(2)
0.71073
Orthorhombic
Pbca
14.711(3)
15.083(3)
17.342(4)
90
C24H28Cl2CoN2
474.31
293(2)
0.71073
Monoclinic
C2/c
29.757(6)
10.487(2)
15.019(3)
90
104.17(3)
90
4544.3(16)
8
1.387
1.003
C21H22Cl2CoN2
432.24
293(2)
0.71073
Monoclinic
P2(1)/c
12.007(2)
12.966(3)
16.588(3)
90
103.00(3)
90
2516.3(9)
4
1.141
0.900
T (K)
3. Conclusion
Wavelength (Å)
Cryst syst
Space group
a (Å)
b (Å)
c (Å)
The series of cobalt(II) and iron(II) complexes bearing 8-(1-
aryliminoethylidene)quinaldines were synthesized and fully char-
acterized by FT-IR, elemental analyses and single crystal X-ray
diffraction. Upon activation with MMAO, all the iron(II) and
cobalt(II) complexes showed good activity in ethylene dimeriza-
tion, in which the iron(II) pre-catalysts showed higher activities
a
b
g
(ꢂ)
(ꢂ)
(ꢂ)
90
90
V (Å3)
3848.0(13)
8
1.444
and better selectivity for a-butene than did their cobalt(II) analogs.
Z
Dcalcd. (mgmꢁ3
)
Bulky substituents resulted in better catalytic activities, with
additional substituents at the para-position of the aryl group
yielding higher activity.
m
(mmꢁ1
)
1.174
F(000)
Cryst size (mm)
1720
1976
892
0.40 ꢀ 0.30 ꢀ 0.20 0.25 ꢀ 0.20 ꢀ 0.08 0.20 ꢀ 0.20
ꢀ 0.09
q
range (ꢂ)
Limiting indices
2.35e30.02
1.41e27.48
ꢁ26 ꢃ h ꢃ 38
ꢁ13 ꢃ k ꢃ 13
ꢁ19 ꢃ l ꢃ 19
18031
1.74e27.45
ꢁ12 ꢃ h ꢃ 15
ꢁ16 ꢃ k ꢃ 16
ꢁ21 ꢃ l ꢃ 16
20193
4. Experimental section
ꢁ14 ꢃ h ꢃ 20
ꢁ14 ꢃ k ꢃ 21
ꢁ24 ꢃ l ꢃ 24
4.1. General considerations
No. of rflns collected 38256
All manipulations of air- and moisture-sensitive compounds were
performed under a nitrogen atmosphere using standard Schlenk
techniques. The 8-(1-aryliminoethylidene)quinaldines(L1eL5)
were prepared according to our reported procedure [45]. Toluene
was refluxed over sodium-benzophenone and distilled under
argon 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. Dieth-
ylaluminium chloride (Et2AlCl, 1.7M in toluene) was purchased
from Acros Chemicals. FT-IR spectra were recorded on a Per-
kineElmer System 2000 FT-IR spectrometer. Elemental analyses
were carried out using a Flash EA 1112 microanalyzer. GC analyses
were performed with a Varian CP-3800 gas chromatograph
equipped with a flame ionization detector and a 30 m (0.2 mm
No. unique rflns
[R(int)]
Completeness to
(%)
Abs corr
Data/restranints
/params
5615 (0.0800)
5217(0.0320)
5634(0.0746)
q
99.9%
99.8%
97.9%
None
5615/0/226
None
5217/0/262
None
5634/0/235
Goodness of fit on
1.313
1.168
0.993
F2
Final R indices
[I > 2s(I)]
R indices (all data)
R1 ¼ 0.0970
wR2 ¼ 0.1868
R1 ¼ 0.1065
wR2 ¼ 0.1910
R1 ¼ 0.0456
wR2 ¼ 0.1235
R1 ¼ 0.0475
wR2 ¼ 0.1249
R1 ¼ 0.0678
wR2 ¼ 0.1702
R1 ¼ 0.0878
wR2 ¼ 0.1838
Largest diff peak
and hole
0.564 and ꢁ0.543 0.409 and ꢁ0.596 0.637 and
ꢁ0.562
(e Åꢁ3
)

2598
S. Song et al. / Journal of Organometallic Chemistry 696 (2011) 2594e2599
i.d., 0.25
m
m film thickness) CP-Sil 5 CB column. The yields of
4.2.7. [2,6-diethyl-N-(1-(2-methylquinoline-8-yl)ethylidene)
benzenamine]CoCl2 (Co2)
Co2 was obtained as a green powder in 79% yield. (Found: C,
59.14; H, 5.45; N, 6.21. C22H24Cl2CoN2 (445.06) requires C, 59.21; H,
5.42; N, 6.28%); FT-IR (Diamond disc, cmꢁ1) 1609, 1584, 1556, 1510,
1443, 1328, 1271, 1203, 858, 771.
oligomers were calculated by referencing with the mass of the
solvent, on the basis of the prerequisite that the mass of each
fraction was approximately proportional to its integrated areas in
the GC trace. Selectivity for the linear
(amount of linear -olefin of all fractions)/(total amount of olig-
a-olefin was defined as
a
omer products) in percent.
4.2.8. [2,6-diisopropyl-N-(1-(2-methylquinoline-8-yl)ethylidene)
benzenamine]CoCl2 (Co3)
4.2. Synthesis of complexes
Co3 was obtained as a green powder in 85% yield. (Found: C,
60.89; H, 5.94; N, 5.89. C24H28Cl2CoN2 (473.10) requires C, 60.77; H,
5.95; N, 5.91%); FT-IR (Diamond disc, cmꢁ1) 1617, 1591, 1563, 1452,
1366, 1325, 1272, 1248, 1202, 849, 804, 762.
4.2.1. [2,6-dimethyl-N-(1-(2-methylquinoline-8-yl)ethylidene)
benzenamine]FeCl2 (Fe1)
To a solution of the ligand (E)-2,6-dimethyl-N-(1-(2-methyl-
quinoline-8-yl)ethylidene)benzenamine (0.288, 1.0 mmol) in
ethanol (5 mL), FeCl2$4H2O (0.199 g, 1.0 mmol) was added under
nitrogen. The reaction mixture was stirred at room temperature for
12 h to afford a precipitate from the reaction mixture. The resulting
precipitate was filtered off, washed twice with diethyl ether and
dried in vacuum to furnish the pure product. Fe1 was obtained as
a red solid in 75% yield. (Found: C, 57.75; H, 4.97; N, 6.51.
C20H20Cl2N2Fe (414.04) requires C, 57.86; H, 4.86; N, 6.75%); FT-IR
(Diamond disc, cmꢁ1) 1618, 1596, 1565, 1505, 1467, 1371, 1280,
1203, 1185, 843, 794, 772.
4.2.9. [2,4,6-trimethyl-N-(1-(2-methylquinoline-8-yl)ethylidene)
benzenamine]CoCl2 (Co4)
Co4 was obtained as a green powder in 77% yield. (Found: C,
58.35; H, 5.17; N, 6.42. C21H22Cl2CoN2 (431.05) requires C, 58.35; H,
5.13; N, 6.48%); FT-IR (Diamond disc, cmꢁ1) 1617, 1582, 1561, 1514,
1376, 1273, 1205, 853, 774.
4.2.10. [2,6-diethyl-4-methyl-N-(1-(2-methylquinoline-8-yl)
ethylidene)benzenamine]CoCl2 (Co5)
C10 was obtained as a green powder in 84% yield. (Found: C,
60.00; H, 5.71; N, 6.05. C23H26Cl2CoN2 (459.08) requires C, 60.01; H,
5.69; N, 6.09%); FT-IR (Diamond disc, cmꢁ1) 1614, 1587, 1561, 1510,
1456, 1267, 1208, 849, 774.
4.2.2. [2,6-diethyl-N-(1-(2-methylquinoline-8-yl)ethylidene)
benzenamine]FeCl2 (Fe2)
Fe2 was obtained as a yellow power in 73% yield. (Found: C,
59.42; H, 5.56; N, 6.21. C22H24Cl2FeN2 (442.07) requires C, 59.62; H,
5.46; N, 6.32%); FT-IR (Diamond disc, cmꢁ1): 2965, 1625, 1600, 1507,
1453, 1368, 1288, 1220, 848, 760.
4.3. General procedure for ethylene dimerization
Ethylene dimerization at 10 atm ethylene pressure was per-
formed in a stainless steel autoclave (0.25 L capacity) equipped
with a mechanical stirrer, a temperature controller and gas ballast
through a solenoid clave for continuous feeding of ethylene at
constant pressure. The catalyst precursor was dissolved in 50 mL
toluene in a Schlenk tube stirred with a magnetic stirrer and
injected into the reactor under an ethylene flux. With adding the
aluminium co-catalyst and more toluene in order to maintain
a total volume of 100 mL toluene, the reaction temperature had
been adapted to the required value, then ethylene with the desired
pressure was introduced to initiate the reaction. After the reaction
mixture had been stirred for the desired period of time, the reaction
was stopped and about 1 mL of the reaction solution was collected,
terminated by the addition of 10% aqueous hydrogen chloride. The
organic layer was analyzed by gas chromatography (GC) for deter-
mining the composition and mass distribution of the oligomers
obtained.
4.2.3. [2,6-diisopropyl-N-(1-(2-methylquinoline-8-yl)ethylidene)
benzenamine]FeCl2 (Fe3)
Fe3 was obtained as a yellow power in 86% yield. (Found:
C,60.99; H, 6.10; N, 5.93. C24H28Cl2FeN2 (470.10) requires C, 61.17; H,
5.99; N, 5.94%); FT-IR (Diamond disc, cmꢁ1): 2963, 1620, 1598, 1514,
1455, 1365, 1290, 1178, 850, 765.
4.2.4. [2,4,6-trimethyl-N-(1-(2-methylquinoline-8-yl)ethylidene)
benzenamine]FeCl2 (Fe4)
Fe4 was obtained as a red power in 78% yield. (Found: C,58.53;
H, 5.27; N, 6.32. C21H22Cl2FeN2 (428.05) requires C, 58.77; H, 5.17;
N, 6.53%); FT-IR (Diamond disc, cmꢁ1) 2915, 1617, 1591, 1564, 1508,
1371, 1274, 1204, 1148, 850, 767.
4.2.5. [2,6-diethyl-4-methyl-N-(1-(2-methylquinoline-8-yl)
ethylidene)benzenamine]FeCl2 (Fe5)
Fe5 was obtained as a yellow power in 86% yield. (Found: C,
60.34; H, 5.79; N, 6.07. C23H26Cl2FeN2 (456.08) requires C, 60.42; H,
5.73; N, 6.13%); FT-IR (Diamond disc, cmꢁ1) 1614, 1497, 1419, 1374,
1249, 1110, 1059, 864, 682.
4.4. Crystal structure determinations
Single-crystals of Co1, Co3 and Co4 suitable for X-ray diffraction
studies were obtained by the slow diffusion of diethyl ether into
their methanol solutions. Single-crystal X-ray diffraction studies
were carried out on a Rigaku RAXIS Rapid IP diffractometer using
4.2.6. [2,6-dimethyl-N-(1-(2-methylquinoline-8-yl)ethylidene)
benzenamine]CoCl2 (Co1)
To a solution of the ligand (E)-2,6-dimethyl-N-(1-(2-methyl-
quinoline-8-yl)ethylidene)benzenamine (0.288 g, 1.0 mmol) in
ethanol (5 mL), CoCl2 (0.130 g, 1 mmol) was added. The reaction
mixture was stirred at room temperature for 12 h to afford a green
precipitate from the reaction mixture. The resultant precipitate was
collected, washed with diethyl ether and dried in vacuum. Co1 was
obtained as a green powder in 80% yield. (Found: C, 58.22; H, 5.24;
N, 6.34. C20H20Cl2CoN2 (431.05) requires C, 58.35; H, 5.13; N, 6.48%);
FT-IR (Diamond disc, cmꢁ1) 1615, 1586, 1560, 1513, 1455, 1272, 1207,
848,770.
graphite monochromated Mo-K
a
radiation (
l
¼ 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 anisotropically. All
hydrogen atoms were placed in calculated positions. Structure
solution and refinement were performed by using the SHELXL-97
package [51]. Crystal data and processing parameters for the
complexes Co1, Co3 and Co4 are summarized in Table 4.

S. Song et al. / Journal of Organometallic Chemistry 696 (2011) 2594e2599
2599
[24] W.-H. Sun, S. Jie, S. Zhang, W. Zhang, Y. Song, H. Ma, J. Chen, K. Wedeking,
R. Fröhlich, Organometallics 25 (2006) 666e677.
Acknowledgments
[25] W.-H. Sun, S. Zhang, S. Jie, W. Zhang, Y. Li, H. Ma, J. Chen, K. Wedeking,
R. Fröhlich, J. Organomet. Chem. 691 (2006) 4196e4203.
[26] S. Jie, S. Zhang, K. Wedeking, W. Zhang, H. Ma, X. Lu, Y. Deng, W.-H. Sun, C. R.
Chim. 9 (2006) 1500e1509.
[27] S. Jie, S. Zhang, W.-H. Sun, X. Kuang, T. Liu, J. Guo, J. Mol. Catal. A: Chem. 269
(2007) 85e96.
This work is supported by MOST 863 program No.
2009AA033601. The EPSRC are thanked for the awarded of a travel
grant (to CR).
[28] S. Zhang, S. Jie, Q. Shi, W.-H. Sun, J. Mol. Catal. A: Chem. 276 (2007)
174e183.
Appendix A. Supplementary material
[29] J.D.A. Pelletier, Y.D.M. Champouret, J. Cadarso, L. Clowes, M. Ganete, K. Singh,
V. Thanarajasingham, G.A. Solan, J. Organomet. Chem. 691 (2006) 4114e4123.
[30] S. Jie, S. Zhang, W.-H. Sun, Eur. J. Inorg. Chem. (2007) 5584e5598.
[31] W.-H. Sun, P. Hao, S. Zhang, Q. Shi, W. Zuo, X. Tang, X. Lu, Organometallics 26
(2007) 2720e2734.
CCDC 812782, 812783, and 812784 contain the supplementary
crystallographic data for the complexes Co1, Co3 and Co4. These
data can be obtained free of charge from The Cambridge Crystal-
lographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[32] P. Hao, S. Zhang, W.-H. Sun, Q. Shi, S. Adewuyi, X. Lu, P. Li, Organometallics 26
(2007) 2439e2446.
[33] W.-H. Sun, P. Hao, G. Li, S. Zhang, W. Wang, J. Yi, M. Asma, N. Tang,
J. Organomet. Chem. 692 (2007) 4506e4518.
References
[34] S. Adewuyi, G. Li, S. Zhang, W. Wang, P. Hao, W.-H. Sun, N. Tang, J. Yi,
J. Organomet. Chem. 692 (2007) 3532e3541.
[35] M. Zhang, S. Zhang, P. Hao, S. Jie, W.-H. Sun, P. Li, X. Lu, Eur. J. Inorg. Chem.
(2007) 3816e3826.
[36] M. Zhang, P. Hao, W. Zuo, S. Jie, W.-H. Sun, J. Organomet. Chem. 693 (2008)
483e491.
[37] S. Zhang, I. Vystorop, Z. Tang, W.-H. Sun, Organometallics 26 (2007)
2456e2460.
[38] S. Zhang, W.-H. Sun, X. Kuang, I. Vystorop, J. Yi, J. Organomet. Chem. 692
(2007) 5307e5316.
[39] K. Wang, K. Wedeking, W. Zuo, D. Zhang, W.-H. Sun, J. Organomet. Chem. 693
(2008) 1073e1080.
[40] R. Gao, Y. Li, F. Wang, W.-H. Sun, M. Bochmann, Eur. J. Inorg. Chem. (2009)
4149e4156.
[41] M. Zhang, R. Gao, X. Hao, W.-H. Sun, J. Organomet. Chem. 693 (2008)
3867e3877.
[1] B.L. Small, M. Brookhart, A.M.A. Bennet, J. Am. Chem. Soc. 120 (1998)
4049e4050.
[2] B.L. Small, M. Brookhart, Macromolecules 32 (1999) 2120e2130.
[3] B.L. Small, M. Brookhart, J. Am. Chem. Soc. 120 (1998) 7143e7144.
[4] G.J.P. Britovsek, V.C. Gibson, B.S. Kimberley, P.J. Maddox, S.J. McTavish,
G.A. Solan, A.J.P. White, D.J. Williams, Chem.Commun. (1998) 849e850.
[5] G.J.P. Britovsek, M. Bruce, V.C. Gibson, B.S. Kimberley, P.J. Maddox,
S. Mastroianni, S.J. McTavish, C. Redshaw, G.A. Solan, S. Strömberg,
A.J.P. White, D.J. Williams, J. Am. Chem. Soc. 121 (1999) 8728e8740.
[6] V.C. Gibson, S.K. Spitzmesser, Chem. Rev. 103 (2003) 283e315.
[7] G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem. Int. Ed. 38 (1999) 428e447.
[8] S.D. Ittel, L.K. Johnson, M. Brookhart, Chem. Rev. 100 (2000) 1169e1203.
[9] S. Mecking, Angew. Chem. Int. Ed. 40 (2001) 534e540.
[10] S. Park, Y. Han, S.K. Kim, J. Lee, H.K. Kim, Y. Do, J. Organomet. Chem. 689
(2004) 4263e4276.
[42] T. Xiao, J. Lai, S. Zhang, X. Hao, W.-H. Sun, Catal. Sci. Technol. DOI:10.1039/
c1cy00028d.
[11] C. Bianchini, G. Giambastiani, G.I. Rios, G. Mantovani, A. Meli, A.M. Segarra,
Coord. Chem. Rev. 250 (2006) 1391e1418.
[43] S. Zhang, W.-H. Sun, T. Xiao, X. Hao, Organometallics 29 (2010) 1168e1173.
[44] J. Yu, L. Hao, W. Zhang, X. Hao, W.-H. Sun, Chem. Commun. 47 (2011)
3257e3259.
[45] S. Song, T. Xiao, T. Liang, F. Wang, C. Redshaw, W.-H. Sun, Catal. Sci. Technol. 1
(2011) 69e75.
[46] E.Y. Chen, T.J. Marks, Chem. Rev. 100 (2000) 1391e1434.
[47] A.R. Karam, E.L. Catarí, F. López-Linares, G. Agrifoglio, C.L. Albano, A. Díaz-
Barrios, T.E. Lehmann, S.V. Pekerar, L.A. Albornoz, R. Atencio, T. González,
H.B. Ortega, P. Joskowics, Appl. Catal. A: Gen. 280 (2005) 165e173.
[48] G.J.P. Britovsek, S. Mastroianni, G.A. Solan, S.P.D. Baugh, C. Redshaw,
V.C. Gibson, A.J.P. White, D.J. Williams, M.R.J. Elsegood, Chem. Eur. J. 6 (2000)
2221e2231.
[12] V.C. Gibson, C. Redshaw, G.A. Solan, Chem. Rev. 107 (2007) 1745e1776.
[13] F. Speiser, P. Braustein, L. Saussine, Acc. Chem. Res. 38 (2005) 784e793.
[14] S. Jie, W.-H. Sun, T. Xiao, Chin. J. Polym. Sci. 28 (2010) 299e304.
[15] W.-H. Sun, D. Zhang, S. Zhang, S. Jie, J. Hou, Kinet. Catal. 47 (2006) 278e283.
[16] W.-H. Sun, S. Zhang, W. Zuo, C.R. Chim. 11 (2008) 307e316.
[17] M. Qian, M. Wang, R. He, J. Mol. Catal. A: Chem. 160 (2000) 243e247.
[18] L. LePichon, D.W. Stephan, X. Gao, Q. Wang, Organometallics 21 (2002)
1362e1366.
[19] G.J.P. Britovsek, V.C. Gibson, O.D. Hoarau, S.K. Spitzmesser, A.J.P. White,
D.J. Williams, Inorg. Chem. 42 (2003) 3454e3465.
[20] R. Cowdell, C.J. Davies, S.J. Hilton, J.-D. Maréchal, G.A. Solan, O. Thomas,
J. Fawcett, Dalton Trans. 20 (2004) 3231e3240.
[49] L. Xiao, R. Gao, M. Zhang, Y. Li, X. Cao, W.-H. Sun, Organometallics 28 (2009)
2225e2233.
[21] M.-S. Zhou, S.-P. Huang, L.-H. Weng, W.-H. Sun, D.-S. Liu, J. Organomet. Chem.
665 (2003) 237e245.
[50] Y. Chen, P. Hao, W. Zuo, K. Gao, W.-H. Sun, J. Organomet. Chem. 693 (2008)
1829e1840.
[22] W.-H. Sun, X. Tang, T. Gao, B. Wu, W. Zhang, H. Ma, Organometallics 23 (2004)
5037e5047.
[51] G.M. Sheldrick, SHELXTL-97, Program for the Refinement of Crystal Structures.
University of Göttingen, Germany, 1997.
[23] L. Wang, W.-H. Sun, L. Han, H. Yang, Y. Hu, X. Jin, J. Organomet. Chem. 658
(2002) 62e70.