Ethylene polymerization by 2-iminopyridylnickel halide complexes: Synthesis, characterization and catalytic influence of the benzhydryl group

Article abstract of DOI:10.1039/c2dt30989k

A series of 2-(2-benzhydrylbenzenamino)pyridine ligands (L1-L13) was synthesized and used as bidentate N^N ligands with nickel halides to afford the corresponding nickel dihalide complexes L₂Ni₂Cl ₄C1-C13 and L₂NiBr₂D1-D13. All ligands and complexes were characterized by IR and NMR spectroscopy, and by elemental analysis. The molecular structures of the representative complexes C1·2CH₃OH, C5·2H₂O, D4, D7 and D9 were confirmed by single-crystal X-ray diffraction studies. Upon activation with either methylaluminoxane (MAO) or ethylaluminium sesquichloride (Et ₃Al₂Cl₃, EASC), these nickel pre-catalysts exhibited high activities (up to the range of 10⁷ g mol^-1 (Ni) h^-1) towards ethylene polymerization, producing branched polyethylenes with narrow polydispersity.

Full text of DOI:10.1039/c2dt30989k

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An international journal of inorganic chemistry
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Volume 41 | Number 39 | 21 October 2012 | Pages 11909–12312
ISSN 1477-9226
COVER ARTICLE
Wen-Hua Sun, Carl Redshaw et al.
Ethylene polymerization by 2-iminopyridylnickel halide complexes: synthesis,
characterization and catalytic influence of the benzhydryl group

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PAPER
Ethylene polymerization by 2-iminopyridylnickel halide complexes: synthesis,
characterization and catalytic influence of the benzhydryl group†
Wen-Hua Sun,*a Shengju Song,a Baixiang Li,b Carl Redshaw,*c Xiang Hao,a Yue-Sheng Lib and
Fosong Wanga
Received 7th May 2012, Accepted 7th August 2012
DOI: 10.1039/c2dt30989k
A series of 2-(2-benzhydrylbenzenamino)pyridine ligands (L1–L13) was synthesized and used as
bidentate N^N ligands with nickel halides to afford the corresponding nickel dihalide complexes
L2Ni2Cl4 C1–C13 and L2NiBr2 D1–D13. All ligands and complexes were characterized by IR and NMR
spectroscopy, and by elemental analysis. The molecular structures of the representative complexes
C1·2CH3OH, C5·2H2O, D4, D7 and D9 were confirmed by single-crystal X-ray diffraction studies.
Upon activation with either methylaluminoxane (MAO) or ethylaluminium sesquichloride (Et3Al2Cl3,
EASC), these nickel pre-catalysts exhibited high activities (up to the range of 107 g mol−1 (Ni) h−1
towards ethylene polymerization, producing branched polyethylenes with narrow polydispersity.
)
corresponding nickel complexes,16 and all resulting complex
pre-catalysts showed an enhancement of both their catalytic
activity and thermo-stability. With this in mind, benzhydryl-sub-
stituted anilines have been used in reactions with picolinalde-
hyde or 2-acetylpyridine to form a series of 2-iminopyridine
compounds, and two series of nickel halide complexes have
been isolated and characterized. When activated with various
alkylaluminium co-catalysts, all such nickel complex pre-cata-
lysts performed with high activities (up to the range of 107 g
mol−1 (Ni) h−1) in ethylene polymerization. The synthesis and
characterization of the 2-iminopyridine ligands and their nickel
halide complexes are reported herein and are discussed along
with investigations of the catalytic behavior of the nickel com-
plexes in ethylene polymerization.
Introduction
Great progress has been made in the area of late-transition metal
complexes as catalysts for polyolefin production over the last
decade or so.1 Significant features can be incorporated into the
resultant polyethylenes (PE) by employing different classes of
pre-catalysts in the homo-polymerization of ethylene, namely
iron and cobalt-based pre-catalysts for highly linear PE2 or
nickel and palladium-based systems for branched PE.3 Further-
more, such systems have also enjoyed some success in the some-
what more challenging area of the co-polymerization of ethylene
with polar monomers.4 The search for useful nickel complex
pre-catalysts has included the use of various ligand sets, which
can act as bi-dentate chelates based on P^O,5 P^P,6 N^O,7 P^N,8
and N^N9,10 ligation and tri-dentate chelates based on N^N^O,11
N^P^N,12 P^N^N,13 and N^N^N14 ligation. In general, N^N
bidentate nickel pre-catalysts provided more variation for both
ethylene oligomerization and polymerization via the fine-tuning
of substituents on their ligands.9,10 Recently, benzhydryl-substi-
tuted anilines were used in successfully modifying both bis-
(imino)pyridine ligands for the corresponding iron and cobalt
complexes15 and imino-based bidentate ligands for the
Results and discussion
Synthesis and characterization of ligands and nickel complexes
The condensation reaction of benzhydryl-substituted anilines
with picolinaldehyde readily affords 2-((benzhydryl-phenyl-
imino)methyl)pyridine compounds in good isolated yields
(L1–L7, Scheme 1), whilst similar reactions with 2-acetylpyri-
dine produced 2-((benzhydryl-phenylimino)ethyl)pyridine com-
pounds (L8–L13, Scheme 1) with the exception of L14, which
proved difficult to purify. All compound formulations were con-
sistent with the recorded FT-IR and NMR spectra and the
obtained elemental analyses.
The series of 2-iminopyridine compounds (L1–L13,
Scheme 1) when reacted with an equivalent of nickel chloride
(NiCl2·6H2O) or half an equivalent of (1,2-dimethoxyethane)-
nickel bromide [(DME)NiBr2] in ethanol afforded a yellow pre-
cipitate of the respective nickel complex on addition of diethyl
ether. These nickel complexes were characterized by FT-IR
aKey Laboratory of Engineering Plastics and Beijing National
Laboratory for Molecular Sciences, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, China. E-mail: whsun@iccas.ac.cn;
Fax: +86 10 62618239; Tel: +86 10 62557955
bState Key Laboratory of Polymer Physics and Chemistry, Changchun
Institute of Applied Chemistry, Chinese Academy of Sciences,
Changchun 130022, China
cEnergy Materials Laboratory, School of Chemistry, University of East
Anglia, Norwich, NR4 7TJ, UK. E-mail: carl.redshaw@uea.ac.uk;
Fax: +44 (0)1603 592003; Tel: +44 (0)1603 593137
†CCDC 877850, 877851, 877852, 877853, and 877854 for
C1·2CH3OH, C5·2H2O, C17, C20 and C22. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c2dt30989k
This journal is © The Royal Society of Chemistry 2012
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Fig. 2 Molecular structure of C5·2H2O thermal ellipsoids are shown at
30% probability level. Hydrogen atoms have been omitted for clarity.
Scheme 1 Synthetic procedure.
Fig. 1 Molecular structure of C1·2CH3OH thermal ellipsoids are
shown at 30% probability level. Hydrogen atoms have been omitted for
clarity.
Fig. 3 Molecular structure of D4 thermal ellipsoids are shown at 30%
probability level. Hydrogen atoms have been omitted for clarity.
spectra, which revealed that the νCvN stretching frequencies
shifted to lower values with weaker intensity on comparison
with those of the corresponding free ligands, for example the
νCvN stretching frequency is 1644 cm−1 for the 2-iminopyri-
dine compound L1 cf 1631 cm−1 for the nickel chloride C1 and
1630 cm−1 for the nickel bromide D1. However, their elemental
analysis data indicated different structural features for the chlor-
ide compounds, i.e. L2Ni2Cl4 (C1–C13, Scheme 1) versus the
bromide compounds, viz. L2NiBr2 (D1–D13, Scheme 1). Single
crystals of the representative nickel complexes C1·2CH3OH,
C5·2H2O, D4, D7 and D9 were grown by slow diffusion of
diethyl ether into their methanol solutions, and the molecular
structures were confirmed by single crystal X-ray diffraction.
The nickel chloride complexes C1·2CH3OH and C5·2H2O were
found to be chloride-bridged bimetallic dimers (Fig. 1 and 2),
whilst the bromide analogs D4, D7 and D9 possessed a bis-
chelate structure around the nickel center along with two
bromide ligands (Fig. 3–5).
Fig. 4 Molecular structure of D7 thermal ellipsoids are shown at 30%
probability level. Hydrogen atoms have been omitted for clarity.
12000 | Dalton Trans., 2012, 41, 11999–12010
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Table 2 Selected bond lengths (Å) and angles (°) for D4, D7 and D9
D4
D7
D9
Bond lengths (Å)
Ni(1)–N(1)
Ni(1)–N(2)
Ni(1)–N(1A)
Ni(1)–N(2A)
Ni(1)–Br(1)
2.037(3)
2.057(5)
2.067(7)
2.275(3)
2.037(3)
2.275(3)
2.5508(11)
2.310(4)
2.057(5)
2.310(4)
2.5346(8)
2.069(6)
2.045(7)
2.061(7)
2.3961(15)
Bond angles (°)
N(1A)–Ni(1)–N(2A)
N(1A)–Ni(1)–N(1)
N(2A)–Ni(1)–N(1)
N(1A)–Ni(1)–N(2)
N(2A)–Ni(1)–N(2)
N(1)–Ni(1)–N(2)
N(1A)–Ni(1)–Br(1)
N(2A)–Ni(1)–Br(1)
N(1)–Ni(1)–Br(1)
N(2)–Ni(1)–Br(1)
78.36(10)
180.000(1)
101.64(10)
101.64(10)
180.0
78.36(10)
86.75(8)
88.64(7)
93.25(8)
91.36(7)
77.59(17)
180.0
79.6(3)
109.4(3)
93.5(3)
94.3(3)
168.3(3)
79.1(2)
122.5(2)
96.6(2)
128.08(19)
95.05(18)
102.41(17)
102.41(17)
180.00(12)
77.59(17)
90.67(11)
84.88(11)
89.33(11)
95.12(11)
Fig. 5 Molecular structure of D9 thermal ellipsoids are shown at 30%
probability level. Hydrogen atoms have been omitted for clarity.
Table 1 Selected bond lengths (Å) and angles (°) for C1·2CH3OH and
C5·2H2O
C1·2CH3OH
C5·2H2O
distance is 3.363 Å, though slightly shorter than the literature
data,10a,b indicating no direct bonding between the two nickel
atoms. On comparison with analogous reported complexes,10a,b
the two nickel–nitrogen bonds were enlarged along with a
smaller nitrogen–nickel–nitrogen angle, which is possibly
caused by the benzhydryl-substituents, which act as better
electron-withdrawing groups than do alkyl substituents. The
same structural features are exhibited by complex C5, and so
there is no need to discuss them further.
Fig. 3 shows how the nickel centre of complex D4 is
surrounded by four nitrogen atoms of two bi-dentate ligands and
two bromide ligands to give an octahedral geometry, similar to
reported analogues.9o,10e The Ni–N bonds are of different
lengths with the Ni–Npyridine shorter than the Ni–Nimino, for
Bond lengths (Å)
Ni(1)–N(1)
Ni(1)–N(2)
Ni(1)–Cl(1)
Ni(1)–Cl(2)
Ni(1)–O(1)
2.082(3)
2.103(3)
2.3831(10)
2.4111(9)
2.108(2)
2.063(4)
2.150(4)
2.3631(16)
2.4773(15)
2.186(4)
Bond angles (°)
N(1)–Ni(1)–N(2)
N(1)–Ni(1)–O(1)
N(2)–Ni(1)–O(1)
N(1)–Ni(1)–Cl(1)
N(2)–Ni(1)–Cl(1)
O(1)–Ni(1)–Cl(1)
N(1)–Ni(1)–Cl(2)
N(2)–Ni(1)–Cl(2)
O(1)–Ni(1)–Cl(2)
Cl(1)–Ni(1)–Cl(2)
78.55(11)
97.39(10)
90.57(10)
87.16(8)
95.92(8)
172.72(7)
171.90(8)
93.54(8)
84.30(7)
91.99(3)
79.10(17)
88.23(17)
91.89(15)
91.36(14)
98.71(12)
169.12(11)
95.71(13)
171.17(11)
80.74(11)
88.49(5)
example Ni1–N1, 2.037(3)
Å and Ni1–N2, 2.275(3) Å
(see Table 2). The same structural features are also observed in
the molecular structure of complex D7 (Fig. 4 and Table 2).
As shown in Fig. 5, however, complex D9 adopted a distorted
square-based pyramidal geometry about the nickel center.
The nickel atom was coordinated by four nitrogen atoms of
two ligands and one bromide, leaving a bromide as a free-anion.
In addition, the Ni–N bond distances were short, but of quite
Crystal structures
Molecular structures of the nickel chloride complexes
C1·2CH3OH (Fig. 1) and C5·2H2O (Fig. 2) revealed centrosym-
metric dimers with a distorted octahedral geometry at the nickel
center. The metal is coordinated by two nitrogen atoms of the
ligand (N1 and N2), one terminal chlorine (Cl1), two bridging
chlorine atoms (Cl2 and Cl2A) and one additional oxygen from
the solvent (C1, methanol; C5, water). Selected bond lengths
and angles are tabulated in Table 1.
Chloro-bridged nickel dimers are common, and reported
examples include complexes bearing bidentate ligands such as
2-(arylimino)pyridines10a,b as well as N-(5,6,7-trihydroquinolin-
8-ylidene)arylaminonickel dichlorides.9n,o,p,16c For the nickel
complex C1, the coordination of nickel with the bidentate ligand
provided a five-membered heterocyclic ring comprising Ni1, N1,
C5, C6 and N2, in which the nickel atom deviates by 0.289 Å
from the co-plane of the four atoms N1, C8, C9 and N2. The
pyridyl and phenyl planes are near perpendicular with a dihedral
angle of 85.97°, whilst the dihedral angles are −89.0(4)° for C6–
N2–C7–C8 and 94.2(4)° for C6–N2–C7–C12. The Ni1⋯Ni1A
similar lengths with Ni–Npyridine shorter than the Ni–Nimino
.
Ethylene polymerizaion
The ligands used herein can be divided into the two groups
2-((benzhydryl-phenylimino)methyl)pyridine derivatives (i.e.
R = H, L1–L7) and 2-((benzhydryl-phenylimino)ethyl)pyridine
derivatives (i.e.
R = Me, L8–L13), whilst their nickel
complexes can also be considered separately as two groups with
R = H for chloride complexes C1–C7 and bromide complexes
D1–D7, and R = Me for chloride complexes C8–C13 and
bromide complexes D8–D13. The reaction conditions were opti-
mized by considering the reaction parameters such as the co-
catalyst type, the molar ratio of co-catalyst to nickel complex
(Al/Ni), the ethylene pressure, reaction temperature and the
polymerization lifetime.
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Table 3 Ethylene polymerization by pre-catalyst C1 with various co-catalystsa
c
c
d
Run
Co-cat
T/°C
Al/Ni
Poly./g
Act.b
Mw
Mw/Mn
Tm
Branchese
1
2
3
4
5
6
7
MAO
MAO
MMAO
Et2AlCl
Et2AlCl
EASC
EASC
20
30
20
20
30
20
30
1000
1000
1000
200
200
200
15.5
15.3
12.0
12.6
11.6
11.0
9.80
9.30
9.18
7.20
7.56
6.96
6.60
5.88
1.58
1.30
1.93
1.53
1.08
1.59
1.21
2.00
1.86
1.93
1.85
1.77
2.50
1.91
103
85.1
100
104
86.2
105
88.7
63.1
54.9
46.5
61.9
55.8
45.8
56.2
200
a Conditions: 5 μmol Ni, 20 min, 10 bar ethylene, 100 mL of toluene. b Activity, 106 g mol−1 (Ni) h−1
.
c Molecular weights were determined by GPC,
kg mol−1 d Determined by DSC, °C. e Determined by IR,17 Branches/1000C.
.
Table 4 Catalytic results of ethylene polymerization with C1/MAOa
Act.b
Mw
Mw/Mn
Tm
Branchese
c
c
d
Run
Al/Ni
T/°C
t/min
Poly./g
1
2
3
4
5
6
7
8
500
20
20
20
20
20
30
40
20
20
20
20
20
20
20
20
20
20
20
20
40
60
20
20
120
11.3
15.5
15.9
15.8
15.6
15.4
7.23
21.7
25.3
0.97
8.75
225
6.78
9.30
9.54
9.48
9.36
9.24
4.34
6.51
5.06
0.58
5.25
4.50
1.14
1.58
1.58
1.64
1.57
1.39
1.00
1.42
1.49
1.39
1.48
1.55
1.81
2.00
1.96
2.01
2.10
1.88
1.75
1.93
1.96
1.87
1.95
1.99
99.4
103
100
103
102
86.0
Wax
99.4
101
101
102
102
47.5
63.1
53.9
65.1
56.6
56.3
42.3
19.8
53.8
54.2
55.3
55.1
1000
1500
2000
3000
1500
1500
1500
1500
1500
1500
1000
9
10f
11g
12h
a Conditions: 5 μmol Ni, 10 bar ethylene, 100 mL of toluene. b Activity, 106 g mol−1 (Ni) h−1
kg mol−1 d Determined by DSC, °C. e Determined by IR,17 Branches/1000C. f Conditions: 5 μmol Ni, 1 atm. ethylene, 30 mL of toluene.
g Conditions: 5 μmol Ni, 5 atm. ethylene, 100 mL of toluene. h Conditions: 25 μmol Ni, 10 atm. ethylene, 3000 mL of toluene.
.
c Molecular weights were determined by GPC,
.
Ethylene polymerization by nickel complexes bearing
2-((benzhydryl-phenylimino)methyl)pyridine derivatives (R =
H). In order to determine the most suitable co-catalyst, initial
investigations of pre-catalyst C1 were conducted with various
alkylaluminium reagents, such as methylaluminoxane (MAO),
modified methylaluminoxane (MMAO), diethylaluminium chloride
(Et2AlCl) and ethylaluminium sesquichloride (Et3Al2Cl3,
EASC), at 20 °C and 30 °C under 10 atm ethylene (in Table 3).
The polymers obtained possessed low molecular weight, but
with narrow distribution. Upon activation with methylaluminoxane
(MAO), the nickel pre-catalyst C1 showed high catalytic
activities (up to 9.30 × 106 g mol−1 (Ni) h−1) for ethylene
polymerization. Therefore, MAO was the most effective co-cata-
lyst and the catalytic behavior of C1/MAO was investigated
further.
The catalytic behavior of complex C1 was evaluated for
optimum conditions using the co-catalyst MAO under 10 atm
ethylene. In the presence of MAO, the effects of these para-
meters on activities of the pre-catalysts, molecular weights and
PDIs of the resultant polyethylenes were evaluated and are pre-
sented in Table 4. From the data, it was observed that the cata-
lytic activity was enhanced on increasing the Al/Ni ratio from
500 up to 1500 (runs 1–3 in Table 4), and for the C1/MAO cata-
lyst system, the highest activity was 9.54 × 106 g mol−1 (Ni) h−1
within 20 min (run 3 in Table 4). However, a slight decrease of
activity was observed on further increasing the Al/Ni ratio from
1500 to 3000 (runs 3–5 in Table 4). Thus, the most suitable
molar ratio of Al : Ni was 1500 : 1 (run 3 in Table 4), whilst the
best performance was observed at 20 °C (runs 3 and 6–7 in
Table 4). Further elevating the temperature from 20 °C to 40 °C
led to a marked decrease of activity, while the molecular weights
exhibited the same trend, which is similar to previously reported
pyridinylimine catalyst systems and might be caused by the
instability of the active species or possibly a lower concentration
of ethylene in the reaction solution at the elevated reaction tem-
perature.9k,10a At higher temperatures, the nickel catalysts
undergo irreversible decomposition. Although highly dependent
on the polymerization temperature, the molecular weight of the
materials produced by these Ni(II) complexes (Mw in the range
1001–1640) remains remarkably lower than that obtained with
analogous α-diimine systems under similar conditions,3 indicat-
ing that so-called chain walking (a chain end isomerization
involving repetitive β-H elimination and rotation/reinsertion of
the eliminated olefin) was less frequent.1b,18 In general, all poly-
ethylene products possessed narrow polydispersity in the range
of 1.75–2.10, indicative of single site active species. The other
pre-catalysts were also found to have high activity for ethylene
polymerization and the data is summarized in Table 5.
Ethylene polymerizations with the catalytic system C1/MAO
were conducted under different pressures of ethylene (runs 3, 10,
11 in Table 4). The ethylene concentration significantly affected
the catalytic behavior. As depicted in Table 4, the higher the
12002 | Dalton Trans., 2012, 41, 11999–12010
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Table 5 Catalytic results of ethylene polymerization with C1–C7,
D1–D7/MAOa
and D1–D3), the ethylene polymerization activities decreased
with the size of the R1 substituents in the order C1 (R1 = Me) >
C2 (R1 = Et) > C3 (R1 = iPr) (runs 1–3 in Table 5). This implied
that the less bulky R1 (R1 = Me) group was favorable for
enhanced activity. It is assumed that the factors controlling the
reaction speed mostly relies on the insertion of ethylene at the
active metal center, and a less bulky group allows for a faster
insertion reaction and consequently higher activity. The para-
substituent (R2) also affected the catalytic activities of these
nickel complexes, and the observed activity order was C4 (R2 =
Me) > C5 (R2 = iPr) (runs 4–5 in Table 5). The introduction of
chloro substituents at the phenyl group (R2 = Cl) led to higher
catalytic activity, which was attributed to the electron withdraw-
ing groups. These phenomena are consistent with the trend of
‘the higher the net charge of the late-transition metal complexes,
the higher the catalytic activity of the complex pre-catalysts’.19
The complexes C4–C6 with steric hindrance (benzhydryl) at
the ortho aryl position produced polymers with much higher
molecular weight and wider distribution than complexes C1–C3,
which was attributed to the dibenzhydryl steric protection at the
ortho aryl. Bulky anilines with an ortho-dibenzhydryl substitu-
ent either on both sides or only one side can be employed,
however only one ortho-dibenzhydryl-substituent proved enough
to provide effective steric protection for achieving higher activi-
ties and lower molecular weight products, which is supported by
our results on the unsymmetrical ligand/nickel systems reported
and is consistent with the literature.10f,g In a similar manner to
the chloride analogues, ethylene polymerization by the bromide
systems D1–D7/MAO was investigated under the optimum con-
ditions (Al/Ni molar ratio of 1500 : 1 at 20 °C in Table 5). Rela-
tively higher activities were exhibited relative to those of the
chloride analogues, presumably because of the better solubility
associated with the former. Other bis-ligated bromide complexes
of the type (L)2Ni in literature were inactive or of low activity
for polymerization because no sites are available for the olefin
insertion reaction.7a,18a,b However, the nickel bromide complexes
(L)2NiBr2 herein were active when combined with co-catalysts
such as MAO or other alkylaluminiums in the presence of
olefins, where they are possibly transformed into a mono-ligated
complex of the type (L)NiBr2.9d,10e The nickel(II) bromide pre-
catalysts demonstrated a significant influence on the activity, the
molecular weight and branching frequency of the obtained PEs.
The trend for catalytic activities was such that the order D6 > D1
> D4 > D5 > D7 > D2 > D3 was observed. The presence of an
electron withdrawing group (p-Cl) on the aryl system affects the
catalytic activities. Compared with other analogs containing the
ortho-alkyl substituted arylamine unit that produce branched
oligomers, PEs or mixture thereof,9d,10a,c,d,f the current nickel
pre-catalysts derived from bulky ortho-benzhydryl substituted
arylamines showed increased activities. Apparently, the bulky
benzhydryl unit herein provided steric protection, which
favoured chain propagation over β-H transfer and thereby
enhanced activities. The mononuclear systems showed much
higher activities than those observed for the binuclear sys-
tems.9f,10h The attainment of low molecular weight polyethylenes
is likely due to the fact that the (imino)pyridine ligands provide
only half of the ortho aryl steric protection (compared to sym-
metric α-diimine ligands), thus increasing the chain transfer
rate.9j Compared with N-(5,6,7-trihydroquinolin-8-ylidene)-
Run Pre-cat. Poly./g Act.b Mw
Mw/Mn
Tm
Branchese
c
c
d
1
2
3
4
5
6
7
8
C1
C2
C3
C4
C5
C6
C7
D1
D2
D3
D4
D5
D6
D7
15.9
13.4
12.2
15.4
14.6
17.0
13.8
23.2
21.5
20.0
22.3
20.8
23.3
21.3
9.54 1.58 1.96
8.04 2.15 2.17
7.32 1.38 2.03
9.24 2.56 2.47
8.76 2.12 2.42
100
106
97.2 67.1
98.7 54.9
98.2 62.7
99.6 64.1
98.5 54.2
53.9
55.8
10.2
2.15 2.50
8.28 1.73 2.40
13.8
1.55 2.16
1.38 2.11
2.13 2.30
2.03 2.45
2.83 2.47
2.56 2.52
2.08 2.34
103
43.2
40.2
45.8
45.3
27.1
49.6
60.9
9
12.5
12.0
13.4
12.9
13.9
12.8
102
103
103
102
102
103
10
11
12
13f
14
a Conditions: 5.0 μmol Ni, 1500 equiv. MAO, 20 °C, 20 min, 10 bar
ethylene, 100 mL of toluene. b 105 g mol−1 (Ti) h−1 c Molecular
.
weights were determined by GPC, kg mol−1 d Determined by DSC, °C.
.
e Determined by IR,17 Branches/1000C. f Determined by NMR,20
Branches/1000C.
Fig. 6 The correlation between catalytic activity and time.
ethylene pressure, the higher the catalytic activity; the higher
pressure increased the chain propagation, leading to higher
molecular weights.
In terms of the lifetime for the C1/MAO system, the ethylene
polymerization was conducted over different time periods,
namely 20, 40 and 60 min (runs 3 and 8, 9 in Table 4). On
prolonging the reaction time from 20 to 60 min, the activities for
ethylene polymerization slightly decreased. The ethylene was
continually absorbed on prolonging of the reaction time
(120 min, run 12 in Table 4). Given the lifetime of the active
species is relatively long (shown in Fig. 6), such systems could
have potential industrial application.
To compare the influence of the ligand environment on the
catalytic behaviour of these nickel pre-catalysts, the pre-catalysts
C1–C7 and D1–D7 were investigated under the optimum con-
ditions (Al/Ni molar ratio of 1500 : 1 at 20 °C) under 10 atm
ethylene, and the data is tabulated in Table 5. The catalytic
activities were likely affected by both steric and electronic influ-
ences of the ligands (substituents R1 and R2). For the nickel(II)
complexes C1–C7 and D1–D7, when R2 = benzhydryl (C1–C3
This journal is © The Royal Society of Chemistry 2012
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View Article Online
arylaminonickel dichlorides,9n,o,p,q,16c these catalysts have higher
activity in ethylene polymerization.
branches was calculated according to the literature,20 and it was
found that polyethylene with 49.6 branches/1000 carbons
(Fig. 7) was obtained at 20 °C (run 13 in Table 5).
The melting point of the polyethylenes obtained were found
to be lower than 110 °C and gradually decreased on elevating
the polymerization reaction temperature. The extent of branching
was a function of both the temperature and the ethylene pressure.
Such unusual properties were caused by the formation of poly-
ethylenes with moderate branching, as confirmed by the
13C NMR measurements. As shown in Fig. 7, the number of
Ethylene polymerization by nickel complexes bearing
2-((benzhydryl-phenylimino)ethyl)pyridine derivatives (R
=
Me). On changing from the aldimine (R = H) to the ketimine (R
= Me) derivative (for a given aryl group), a reduction in the
activity of the catalyst system was observed along with a higher
molecular weight and narrow distribution for the polymer. In a
similar procedure, complex D11 was used to explore suitable
co-catalysts (runs 1–4 in Table 6) for optimum polymerization
conditions. The D11 catalytic system displayed high catalytic
activities for ethylene polymerization with various alkylalumi-
nium reagents (MAO, MMAO, Et2AlCl and EASC). In the pres-
ence of EASC, the highest activity was obtained, and produced
high molecular weight polyethylene. Based on catalytic activity
and economic considerations (less co-catalyst), EASC was
selected for further investigation, and the catalytic system under
10 bar ethylene was typically investigated, with varying reaction
parameters (Table 6).
On changing the reaction parameters, it was observed that
nickel bromide complex D11 has higher activity under the
optimum conditions (10 atm ethylene, Al/Ni = 300 : 1 at 20 °C
in Table 6). In the D11/EASC system, ethylene polymerization
was steadily maintained over 60 min (runs 8, 13 and 14 in
Table 6). Therefore, the catalytic behavior of all the nickel com-
plexes were investigated under these optimum conditions, and
the results are summarized in Table 6. Similar catalytic behavior
was observed for these nickel complexes (Table 6), but relatively
Fig. 7 13C-NMR spectrum of polyethylene (run 13 in Table 5).
Table 6 Catalytic results of ethylene polymerization with C8–C13, D8–D13a
Act.b
Mw
Mw/Mn
Tm
Branchese
c
c
d
Run
Pre-cat. (μmol)
Co-cat.
T/°C
t (min)
Al/Ni
Poly./g
1
2
3
4
5
6
7
8
D11(3.0)
D11(3.0)
D11(3.0)
D11(3.0)
D11(1.5)
D11(4.5)
D11(3.0)
D11(3.0)
D11(3.0)
D11(3.0)
D11(3.0)
D11(3.0)
D11(3.0)
D11(3.0)
C8(5.0)
MAO
20
20
20
20
20
20
20
20
20
20
30
40
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
40
60
20
20
20
20
20
20
20
20
20
20
20
20
1000
1000
200
200
200
200
100
300
400
500
300
300
300
300
300
300
300
300
300
300
300
300
300
300
300
300
3.05
2.23
2.68
3.33
1.21
4.15
2.99
3.49
3.02
1.81
2.98
1.45
6.50
9.62
9.85
6.12
5.23
3.23
3.15
3.45
6.78
5.29
4.50
2.72
3.51
3.50
3.05
2.23
2.68
3.33
2.42
2.77
2.99
3.49
3.02
1.81
2.98
1.45
3.25
3.21
5.91
3.67
3.14
1.94
1.89
2.07
6.78
5.29
4.50
2.72
3.51
3.50
2.83
3.23
3.31
3.66
4.63
3.67
3.98
3.82
3.25
2.88
3.72
2.13
3.72
3.62
1.59
2.09
2.28
4.05
3.95
4.55
1.85
2.12
2.29
3.83
3.99
3.79
2.17
2.00
2.16
2.09
2.00
2.01
2.03
1.99
2.00
1.91
1.99
1.87
2.19
2.07
1.90
1.92
2.00
2.00
2.00
2.00
1.87
1.89
2.01
2.03
1.90
1.97
87.7
84.0
89.0
88.6
93.7
82.2
93.4
92.5
88.2
96.3
43.5
45.7
53.2
39.3
29.4
20.1
53.3
44.1
53.1
49.6
53.3
42.2
63.1
29.8
43.3
44.1
63.1
54.7
42.7
56.1
74.4
19.5
13.4
49.6
29.6
32.9
MMAO
Et2AlCl
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
9
10
11
12
13
14
15f
16
17
18
19
20
21
22
23
24
25
26g
Wax
Wax
94.7
96.0
97.7
96.0
99.2
95.6
98.7
97.2
98.4
98.5
102
104
97.5
98.9
C9(5.0)
C10(5.0)
C11(5.0)
C12(5.0)
C13(5.0)
D8(3.0)
D9(3.0)
D10(3.0)
D12(3.0)
D13(3.0)
D11(3.0)
a Conditions: 10 bar ethylene, 100 mL of toluene. b Activity, 106 g mol−1 (Ni) h−1
.
c Molecular weights were determined by GPC, kg mol−1
d Determined by DSC, °C. e Determined by IR,17 Branches/1000C. f Determined by NMR,20 Branches/1000C. g With adding 3.0 μmol(DME)NiBr2.
.
12004 | Dalton Trans., 2012, 41, 11999–12010
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lower activities and higher molecular weights were exhibited
relative to those of their analogues (Table 5). A clear trend for
catalytic activities was displayed in regard to the nature of the
ligands present, such that the order C8 > C9 > C10, C13 > C11
> C12, D8 > D9 > D10 and D13 > D11 > D12 was observed.
However, the complexes C8–C10 and D8–D10 displayed higher
polymerization activity than did complexes C11–C13 and
D11–D13, which suggested that a reduction in the steric bulk at
the ortho-aryl position or replacement of the para-aryl proton
with a chlorine can increase the activity. Furthermore, complexes
C11–C13 and D11–D13 with increased steric hindrance at the
ortho-aryl, produced polymers of much higher molecular weight
than those by pre-catalysts C8–C10 and D8–D11. From the
crystal structures, the nickel center of D9 appears to be
restricted/hindered from interacting with ethylene and this leads
to the poorer catalytic properties, which is similar to other
reports.14g On introducing one equivalent of (DME)NiBr2,
complex D11 did not show higher activity, which indicated that
there were no new active species formed during the ethylene
polymerization. The polyethylene obtained was analyzed by
13C-NMR measurements and the number of branches was calcu-
lated according to the literature,20 and it was found that poly-
ethylene with 43.3 branches/1000 carbons (Fig. 8) was obtained
at 20 °C (run 15 in Table 6).
Experimental section
Syntheses and characterization of the organic compounds and
nickel complexes
2-((2,4-Dibenzhydryl-6-methylphenylimino)methyl)pyridine
(L1). A mixture of picolinaldehyde (0.540 g, 5.0 mmol), 2,4-
dibenzhydryl-6-methylbenzenamine (2.19 g, 5.0 mmol) and a
catalytic amount of p-toluenesulfonic acid in toluene (80 mL)
were refluxed for 6 h. After solvent evaporation at reduced
pressure, the crude product was purified by column chromato-
graphy on alumina with the eluent of petroleum ether–ethyl
acetate (v : v = 10 : 1) to afford a white solid in 78% isolated
yield. Mp: 163–164 °C. δH (400 MHz; CDCl3; Me4Si) 8.61 (1H,
d, J = 7.6 Hz), 8.04 (1H, d, J = 7.9 Hz), 7.81 (1H, s), 7.56 (1H,
t, J = 10.2 Hz), 7.32 (1H, t, J = 8.1 Hz), 7.23 (4H, t, J =
9.7 Hz), 7.17 (2H, d, J = 7.3 Hz), 7.14–7.08 (6H, m), 7.04 (4H,
d, J = 7.3 Hz), 6.94 (4H, d, J = 7.8 Hz), 6.87 (1H, s), 6.57 (1H,
s), 5.54 (1H, s), 5.39 (1H, s), 2.06 (3H, s, –CH3). δC (100 MHz;
CDCl3; Me4Si) 164.2, 154.2, 149.5, 148.3, 144.2, 143.5, 139.0,
136.5, 134.1, 129.8, 129.5, 129.3, 128.9, 128.2, 128.1, 126.1,
126.0, 125.9, 125.2, 121.3, 56.34, 52.01, 18.52. Anal. Calcd for
C39H32N2 (528.26) C, 88.60; H, 6.10; N, 5.30; Found: C, 88.53;
H, 6.17; N, 5.20. FT-IR (Diamond disk, cm−1): 3022, 1644,
1598, 1568, 1469, 1448, 1203, 1128, 1077, 745, 698.
2-((2,4-Dibenzhydryl-6-ethylphenylimino)methyl)pyridine (L2).
In a manner similar to that described for L1, L2 was prepared
as a light yellow solid in 75% yield. Mp: 165–166 °C. δH
(400 MHz; CDCl3; Me4Si) 8.62 (1H, d, J = 7.6 Hz), 8.03 (1H,
d, J = 8.0 Hz), 7.76 (2H, m), 7.34 (1H, t, J = 10.1 Hz), 7.22
(4H, d, J = 7.6 Hz), 7.18 (2H, d, J = 7.9 Hz), 7.14–7.10 (6H,
m), 7.04 (4H, d, J = 7.5 Hz), 6.91 (5H, d, J = 7.8 Hz), 6.56 (1H,
s), 5.49 (1H, s), 5.41 (1H, s), 2.45–2.38 (2H, m), 0.87 (3H, t,
J = 8.9, –CH3). δC (100 MHz; CDCl3; Me4Si) 164.1, 154.3,
149.7, 148.2, 144.4, 143.7, 139.1, 136.6, 133.7, 132.3, 129.6,
129.5, 129.4, 129.0, 128.3, 128.2, 126.2, 125.9, 125.3, 121.5,
56.59, 52.22, 24.68, 14.87. Anal. Calcd for C40H34N2 (542.27)
C, 88.52; H, 6.31; N, 5.16; Found: C, 88.42; H, 6.41; N, 5.06.
FT-IR (Diamond disk, cm−1): 3022, 1644, 1598, 1567, 1469,
1447, 1199, 1072, 741, 697.
Conclusion
A series of ligands (L1–L13) and nickel complexes (C1–C13,
D1–D13) were synthesized and fully characterized. Single
crystal X-ray crystallographic studies for representative com-
plexes C1·2CH3OH, C5·2H2O, D4, D7 and D9 were performed.
These nickel complexes exhibited high activities of up to 1.39 ×
107 g mol−1 (Ni) h−1 in ethylene polymerization under optimum
conditions, and produced moderately branched polyethylene of
low molecule weight and narrow PDI, indicative of single-site
active species. The catalytic activities and the molecular weights
decreased on elevating the reaction temperature. Further research
efforts indicated that the ligand substituents present had a
remarkable influence on the observed activities. The highest
activity was obtained with the complex D6 having R as hydro-
gen, R1 as benzhydryl and R2 as chlorine. Such pre-catalysts
could have application in the industrialized production of poly-
ethylene waxes.
2-((2,4-Dibenzhydryl-6-isopropylphenylimino)methyl)pyridine
(L3). In a manner similar to that described for L1, L3 was pre-
pared as a light yellow solid in 79% yield. Mp: 168–169 °C. δH
(400 MHz; CDCl3; Me4Si) 8.63 (1H, d, J = 7.6 Hz), 8.01 (1H,
d, J = 8.1 Hz), 7.77 (1H, t, J = 10.2 Hz), 7.72 (1H, s), 7.34 (1H,
t, J = 10.1 Hz), 7.24 (12H, m), 7.04 (4H, d, J = 7.7 Hz), 6.97
(1H, s), 6.91 (4H, d, J = 7.6 Hz), 6.53 (1H, s), 5.46 (1H, s), 5.41
(1H, s), 2.90–2.83 (1H, m, –CH–), 1.06 (6H, d, J = 8.3 Hz, 2 ×
–CH3). δC (100 MHz; CDCl3; Me4Si) 164.2, 154.3, 149.7,
147.7, 144.6, 143.8, 139.1, 137.1, 136.6, 133.4, 129.7, 129.5,
128.9, 128.3, 128.2, 126.2, 125.3, 121.6, 56.78, 52.41, 27.97,
23.74. Anal. Calcd for C41H36N2 (556.29) C, 88.45; H, 6.52;
N, 5.03; Found: C, 88.35; H, 6.63; N, 4.99. FT-IR (Diamond
disk, cm−1): 3024, 1639, 1585, 1567, 1494, 1444, 1079, 776,
739, 692.
2-((2,6-Dibenzhydryl-4-methylphenylimino)methyl)pyridine (L4).
In a manner similar to that described for L1, L4 was prepared as
Fig. 8 13C-NMR spectrum of polyethylene (run 15 in Table 6).
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a light yellow solid in 70% yield. Mp: 258–259 °C. δH
(400 MHz; CDCl3; Me4Si) 8.58 (1H, d, J = 7.6 Hz), 7.68 (2H,
t, J = 9.9 Hz), 7.58 (1H, d, J = 7.6 Hz), 7.28 (2H, m), 7.21–7.08
(14H, m), 7.00 (7H, d, J = 8.6 Hz), 6.64 (1H, s), 5.53 (1H, s),
2.04 (3H, s, –CH3). δC (100 MHz; CDCl3; Me4Si) 165.1, 153.6,
149.6, 148.1, 143.8, 142.9, 136.5, 133.2, 132.6, 129.8, 129.7,
129.4, 129.2, 128.8, 128.6, 128.2, 128.0, 126.7, 126.3, 125.2,
122.3, 121.8, 52.04, 21.53. Anal. Calcd for C39H32N2 (528.26)
C, 88.60; H, 6.10; N, 5.30; Found: C, 88.45; H, 6.25; N, 5.15.
FT-IR (Diamond disk, cm−1): 3024, 1560, 1589, 1566, 1492,
1445, 1203, 1077, 1030, 872, 741, 700.
5.54 (1H, s), 5.39 (1H, s), 2.06 (3H, s, –CH3), 1.55 (3H, s). δC
(100 MHz; CDCl3; Me4Si) 168.7, 156.3, 148.6, 146.7, 144.6,
144.5, 143.7, 142.7, 138.2, 136.4, 133.3, 129.9, 129.5, 128.9,
128.4, 128.3, 128.1, 126.3, 126.2, 126.0, 125.2, 124.8, 121.3,
56.50, 52.45, 18.11, 16.75. C40H34N2 (542.27) C, 88.52; H,
6.31; N, 5.16. Found: C, 88.43; H, 6.43; N, 4.04. FT-IR
(Diamond; cm−1): 3024, 1643, 1599, 1566, 1493, 1468, 1449,
1362, 1225, 1104, 1075, 1033, 781, 696.
2-((2,4-Dibenzhydryl-6-ethylphenylimino)ethyl)pyridine (L9).
In a manner similar to that described for L1, L9 was prepared as
a yellow solid in 59% yield. Mp: 127–128 °C. δH (400 MHz;
CDCl3; Me4Si) 8.61 (1H, d, J = 8.1 Hz), 8.29 (1H, d, J =
7.9 Hz), 7.78 (1H, t, J = 9.1 Hz), 7.35 (1H, t, J = 9.2 Hz),
7.24–7.04 (16H, m), 6.96 (2H, s), 6.88 (3H, s), 6.59 (1H, s),
5.42 (1H, s), 5.36 (1H, s), 2.22 (2H, m), 1.54 (3H, s), 1.03
(3H, t, J = 9.9 Hz, –CH3). δC (100 MHz; CDCl3; Me4Si) 168.6,
156.4, 148.7, 146.3, 144.7, 144.6, 143.8, 142.7, 138.2, 136.4,
132.8, 131.0, 129.9, 129.5, 128.9, 128.6, 128.3, 128.2, 128.0,
127.5, 126.3, 126.2, 126.0, 124.8, 121.3, 56.65, 52.48, 24.38,
16.97, 13.70. C41H36N2 (556.29) C, 88.45; H, 6.52; N, 5.03.
Found: C, 88.35; H, 6.70; N, 4.99. FT-IR (Diamond; cm−1):
3023, 1638, 1599, 1567, 1493, 1448, 1364, 1305, 1105, 743,
697.
2-((2,6-Dibenzhydryl-4-isopropylphenylimino)methyl)pyridine
(L5). In a manner similar to that described for L1, L5 was pre-
pared as a yellow solid in 75% yield. Mp: 201–202 °C. δH
(400 MHz; CDCl3; Me4Si) 8.58 (1H, d, J = 7.8 Hz), 7.68 (1H, t,
J = 10.2 Hz), 7.61 (1H, d, J = 8.4 Hz), 7.28 (1H, t, J = 9.8 Hz),
7.20–7.09 (12H, m), 7.04 (1H, s), 7.00 (8H, d, J = 7.4 Hz), 6.69
(2H, s), 5.45 (2H, s), 2.73–2.66 (1H, m), 1.06–0.93 (6H, d, J =
8.3 Hz, 2 × –CH3). δC (100 MHz; CDCl3; Me4Si) 165.1, 153.8,
149.6, 148.3, 143.9, 143.5, 136.3, 132.9, 129.7, 128.5, 128.2,
126.2, 125.0, 122.1, 52.16, 33.65, 24.13. Anal. Calcd for
C41H36N2 (556.29) C, 88.45; H, 6.52; N, 5.03; Found: C, 88.27;
H, 6.62; N, 4.99. FT-IR (Diamond disk, cm−1): 3026, 1634,
1585, 1493, 1468, 1444, 1031, 884, 741, 696.
2-((2,4-Dibenzhydryl-6-isopropylphenylimino)ethyl)pyridine
(L10). In a manner similar to that described for L1, L10 was
prepared as a yellow solid in 65% yield. Mp: 164–165 °C. δH
(400 MHz; CDCl3; Me4Si) 8.63 (1H, d, J = 8.1 Hz), 8.31 (1H,
d, J = 8.0 Hz), 7.80 (1H, t, J = 8.0 Hz), 7.37 (1H, t, J = 8.2 Hz),
7.24–7.07 (15H, m), 7.00 (2H, s), 6.92 (2H, s), 6.86 (1H, s),
6.59 (1H, s), 6.27 (1H, s), 5.44 (1H, s), 5.37 (1H, s), 2.61 (1H,
m, –CH–), 1.53 (3H, s), 1.03 (6H, d, J = 8.4 Hz, 2 × –CH3). δC
(100 MHz; CDCl3; Me4Si) 168.6, 156.4, 148.6, 145.5, 144.8,
144.7, 143.8, 142.7, 138.2, 136.4, 135.7, 132.6, 129.9, 129.5,
128.8, 128.3, 128.2, 128.0, 126.2, 126.1, 126.0, 125.0, 124.8,
121.4, 56.76, 52.62, 28.07, 23.80, 22.72, 17.16. C42H38N2
(570.3) C, 88.38; H, 6.71; N, 4.91. Found: C, 88.32; H, 5.00; N,
4.80. FT-IR (Diamond; cm−1): 3023, 1650, 1584, 1566, 1493,
1467, 1444, 1363, 1104, 780, 745, 696.
2-((2,6-Dibenzhydryl-4-chlorophenylimino)methyl)pyridine (L6).
In a manner similar to that described for L1, L6 was prepared as
a yellow solid in 70% yield. Mp: 256–257 °C. δH (400 MHz;
CDCl3; Me4Si) 8.58 (1H, d, J = 8.0 Hz), 7.69 (1H, t, J =
10.1 Hz), 7.51 (1H, d, J = 8.3 Hz), 7.31 (1H, t, J = 9.9 Hz),
7.19–7.09 (13H, m), 6.99 (8H, d, J = 7.4 Hz), 6.89 (1H, s), 6.81
(2H, s). δC (100 MHz; CDCl3; Me4Si) 165.8, 153.3, 149.8,
149.0, 148.3, 142.9, 141.9, 136.5, 135.5, 129.7, 129.5, 129.2,
129.0, 128.8, 128.5, 128.4, 128.2, 128.0, 127.1, 126.6, 125.4,
122.5, 52.08. Anal. Calcd for C38H29ClN2 (548.2) C, 83.12; H,
5.32; N, 5.10; Found: C, 82.99; H, 5.45; N, 4.96. FT-IR
(Diamond disk, cm−1): 3025, 1649, 1566, 1493, 1450, 1433,
1260, 1176, 1077, 1026, 802, 738, 697.
2-((2-Benzhydryl-4,6-dimethylphenylimino)methyl)pyridine (L7).
In a manner similar to that described for L1, L7 was prepared as
a yellow solid in 76% yield. Mp: 116–117 °C. δH (400 MHz;
CDCl3; Me4Si) 8.62 (1H, d, J = 7.8 Hz), 8.02 (1H, d, J =
8.1 Hz), 7.77 (1H, t, J = 10.2 Hz), 7.34 (1H, t, J = 10.1 Hz),
7.21–7.12 (6H, m), 7.04 (4H, d, J = 8.8 Hz), 6.95 (1H, s), 6.59
(1H, s), 6.58 (2H, s), 2.22 (3H, s, –CH3), 2.10 (3H, s, –CH3). δC
(100 MHz; CDCl3; Me4Si) 164.5, 154.4, 149.7, 148.0, 143.9,
136.6, 134.3, 133.2, 130.0, 129.8, 128.3, 128.1, 126.2, 125.9,
125.3, 121.5, 52.08, 21.26, 18.45. Anal. Calcd for C27H24N2
(376.19) C, 86.13; H, 6.43; N, 7.44; Found: C, 86.01; H, 6.55;
N, 7.31. FT-IR (Diamond disk, cm−1): 3021, 1642, 1585, 1492,
1470, 1434, 1202, 1135, 990, 740, 696.
2-((2,6-Dibenzhydryl-4-methylphenylimino)ethyl)pyridine (L11).
In a manner similar to that described for L1, L11 was prepared
as a yellow solid in 66% yield. Mp: 181–182 °C. δH (400 MHz;
CDCl3; Me4Si) 8.58 (1H, d, J = 8.1 Hz), 8.01 (1H, d, J =
8.0 Hz), 7.70 (1H, t, J = 8.0 Hz), 7.32 (1H, t, J = 8.1 Hz),
7.24–7.11 (12H, m), 7.01 (8H, t, J = 10.2 Hz), 6.68 (2H, s), 5.26
(2H, s), 2.17 (3H, s, –CH3), 1.07 (3H, s, –CH3). δC (100 MHz;
CDCl3; Me4Si) 169.7, 156.2, 148.6, 146.3, 143.9, 142.7, 136.2,
132.4, 131.7, 130.0, 129.6, 128.8, 128.4, 128.2, 126.4, 126.1,
124.7, 121.5, 52.26, 21.53, 17.07. C40H34N2 (542.27) C, 88.52;
H, 6.31; N, 5.16. Found: C, 88.42; H, 6.43; N, 5.00. FT-IR
(Diamond; cm−1): 3025, 1646, 1599, 1582, 1493, 1445, 1238,
1106, 769, 697.
2-((2,4-Dibenzhydryl-6-methylphenylimino)ethyl)pyridine (L8).
In a manner similar to that described for L1, L8 was prepared as
a yellow solid in 58% yield. Mp: 123–124 °C. δH (400 MHz;
CDCl3; Me4Si) 8.61 (1H, d, J = 8.0 Hz), 8.31 (1H, d, J = 7.9 Hz),
7.80 (1H, t, J = 8.8 Hz), 7.37 (1H, t, J = 8.2 Hz), 7.23–7.08
(16H, m), 7.00 (2H, s), 6.92 (2H, s), 6.86 (1H, s), 6.62 (1H, s),
2-((2,6-Dibenzhydryl-4-isopropylphenylimino)ethyl)pyridine
(L12). In a manner similar to that described for L1, L12 was
prepared as a yellow solid in 67% yield. Mp: 145–146 °C. δH
(400 MHz; CDCl3; Me4Si) 8.58 (1H, d, J = 8.1 Hz), 8.02 (1H,
d, J = 8.0 Hz), 7.70 (1H, t, J = 8.0 Hz), 7.32 (1H, t, J = 8.0 Hz),
12006 | Dalton Trans., 2012, 41, 11999–12010
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7.24–7.11 (12H, m), 7.00 (8H, t, J = 10.1 Hz), 6.72 (2H, s), 5.26
(2H, s), 2.70 (1H, m, –CH–), 1.06 (9H, d, J = 7.9 Hz, 3 ×
–CH3). δC (100 MHz; CDCl3; Me4Si) 169.5, 156.2, 148.6,
146.5, 144.0, 142.9, 142.7, 136.2, 132.1, 130.0, 129.6, 128.4,
128.1, 126.4, 126.2, 126.1, 124.7, 121.5, 52.44, 33.70, 24.32,
17.14. C42H38N2 (570.3) C, 88.38; H, 6.71; N, 4.91. Found: C,
88.25; H, 6.98; N, 4.84. FT-IR (Diamond; cm−1): 3026, 1646,
1600, 1585, 1566, 1493, 1467, 1362, 1105, 767, 745, 696.
Found: C, 71.65; H, 5.39; N, 4.00. FT-IR (Diamond; cm−1):
3023, 1632, 1597, 1493, 1447, 1157, 1027, 761, 700.
2-((2,6-Dibenzhydryl-4-chlorophenylimino)methyl)pyridyl
nickel dichloride (C6). In a manner similar to that described for
C1, C6 was prepared as a yellow powder in 87% yield. Anal.
Calcd for C38H29Cl3N2Ni (676.07) C, 67.25; H, 4.31; N, 4.13;
Found: C, 67.15; H, 4.44; N, 4.00. FT-IR (Diamond; cm−1):
3021, 1632, 1597, 1571, 1494, 1446, 1302, 1172, 1028, 765,
699.
2-((2,6-Dibenzhydryl-4-chlorophenylimino)ethyl)pyridine (L13).
In a manner similar to that described for L1, L13 was prepared
as a yellow solid in 68% yield. Mp: 142–143 °C. δH (400 MHz;
CDCl3; Me4Si) 8.58 (1H, d, J = 8.1 Hz), 7.98 (1H, d, J =
8.0 Hz), 7.71 (1H, t, J = 8.0 Hz), 7.34 (1H, t, J = 8.2 Hz),
7.24–7.13 (12H, m), 7.01–6.97 (8H, m), 6.84 (2H, s), 5.24 (2H,
s), 1.04 (3H, s, –CH3). δC (100 MHz; CDCl3; Me4Si) 170.2,
155.7, 148.7, 147.1, 142.9, 141.8, 136.3, 134.5, 129.8, 129.5,
128.6, 128.3, 128.1, 126.7, 126.5, 125.0, 121.5, 52.22, 17.16.
C39H31ClN2 (562.22) C, 83.18; H, 5.55; Cl, 6.30; N, 4.97.
Found: C, 83.00; H, 5.65; N, 4.85. FT-IR (Diamond; cm−1):
3025, 1645, 1581, 1563, 1493, 1427, 1302, 1180, 1105, 769,
695.
2-((2-Benzhydryl-4,6-dimethylphenylimino)methyl)pyridyl
nickel dichloride (C7). In a manner similar to that described for
C1, C7 was prepared as a yellow powder in 85% yield. Anal.
Calcd for C27H24Cl2N2Ni (504.07) C, 64.08; H, 4.78; N, 5.54;
Found: C, 63.99; H, 4.88; N, 5.44. FT-IR (Diamond; cm−1):
3023, 1633, 1596, 14446, 1196, 1131, 1026, 770.745, 700.
2-((2,4-Dibenzhydryl-6-methylphenylimino)ethyl)pyridyl nickel
dichloride (C8). In a manner similar to that described for C1, C8
was prepared as a yellow powder in 86% yield. Anal. Calcd for
C40H34Cl2N2Ni (670.15) C, 71.46; H, 5.10; N, 4.17; Found: C,
71.26; H, 5.16; N, 4.10. FT-IR (Diamond; cm−1): 3208, 1611,
1596, 1493, 1444, 1315, 1259, 1029, 743, 698.
2-((2,4-Dibenzhydryl-6-methylphenylimino)methyl)pyridyl
nickel dichloride (C1). The ligand L1 (0.264 g, 0.5 mmol) and
NiCl2·6H2O (0.118 g, 0.5 mmol) were added to a Schlenk tube
together with 10 ml of dried ethanol. The reaction mixture was
then stirred for 12 h at room temperature and diethyl ether
(10 ml) was added to precipitate the complex. The precipitate
was washed with diethyl ether and dried in vacuum to obtain a
yellow powder in 83% yield. Anal. Calcd for C39H32Cl2N2Ni
(656.13) C, 71.16; H, 4.90; N, 4.26; Found: C, 71.00; H, 5.00;
N, 4.36. FT-IR (Diamond; cm−1): 2971, 1631, 1596, 1494,
1448, 1078, 1045, 770, 746, 700.
2-((2,4-Dibenzhydryl-6-ethylphenylimino)ethyl)pyridyl nickel
dichloride (C9). In a manner similar to that described for C1,
C9 was prepared as a yellow powder in 88% yield. Anal. Calcd
for C41H36Cl2N2Ni (684.16) C, 71.75; H, 5.29; N, 4.08; Found:
C, 71.65; H, 5.49; N, 4.00. FT-IR (Diamond; cm−1): 3024,
1613, 1593, 1493, 1451, 1374, 1320, 1259, 743, 697.
2-((2,4-Dibenzhydryl-6-isopropylphenylimino)ethyl)pyridyl
nickel dichloride (C10). In a manner similar to that described
for C1, C10 was prepared as a yellow powder in 89% yield.
Anal. Calcd for C42H38Cl2N2Ni (698.18) C, 72.03; H, 5.47; N,
4.00; Found: C, 72.00; H, 5.57; N, 3.90. FT-IR (Diamond;
cm−1): 3025, 1614, 1592, 1493, 1452, 1373, 1257, 743, 697.
2-((2,4-Dibenzhydryl-6-ethylphenylimino)methyl)pyridyl nickel
dichloride (C2). In a manner similar to that described for C1, C2
was prepared as a yellow powder in 86% yield. Anal. Calcd for
C40H34Cl2N2Ni (670.15) C, 71.46; H, 5.10; N, 4.17%. Found:
C, 71.36; H, 5.30; N, 4.00. FT-IR (Diamond; cm−1): 3225,
1631, 1596, 1494, 1448, 1192, 1077, 1043, 772, 746, 701.
2-((2,6-Dibenzhydryl-4-methylphenylimino)ethyl)pyridyl nickel
dichloride (C11). In a manner similar to that described for C1,
C11 was prepared as a yellow powder in 85% yield. Anal. Calcd
for C40H34Cl2N2Ni (670.15) C, 71.46; H, 5.10; N, 4.17; Found:
C, 71.26; H, 5.30; N, 4.07. FT-IR (Diamond; cm−1): 3024,
1614, 1595, 1494, 1445, 1372, 1317, 1258, 1029, 769, 700.
2-((2,4-Dibenzhydryl-6-isopropylphenylimino)methyl)pyridyl
nickel dichloride (C3). In a manner similar to that described for
C1, C3 was prepared as a yellow powder in 81% yield. Anal.
Calcd for C41H36Cl2N2Ni (684.16) C, 71.75; H, 5.29; N, 4.08;
Found: C, 71.65; H, 5.39; N, 4.00. FT-IR (Diamond; cm−1):
3027, 1633, 1596, 1494, 1447, 1302, 1077, 1040, 775, 745,
701.
2-((2,6-Dibenzhydryl-4-isopropylphenylimino)ethyl)pyridyl
nickel dichloride (C12). In a manner similar to that described
for C1, C12 was prepared as a yellow powder in 89% yield.
Anal. Calcd for C42H38Cl2N2Ni (698.18) C, 72.03; H, 5.47; N,
4.00; Found: C, 72.13; H, 5.57; N, 3.95. FT-IR (Diamond;
cm−1): 2959, 1615, 1596, 1494, 1445, 1317, 1258, 1028, 769,
700.
2-((2,6-Dibenzhydryl-4-methylphenylimino)methyl)pyridyl nickel
dichloride (C4). In a manner similar to that described for
C1, C4 was prepared as a yellow powder in 88% yield. Anal.
Calcd for C39H32Cl2N2Ni (656.13) C, 71.16; H, 4.90; N, 4.26;
Found: C, 71.00; H, 4.98; N, 4.14. FT-IR (Diamond; cm−1):
3025, 1633, 1597, 1494, 1447, 1197, 1029, 765, 702.
2-((2,6-Dibenzhydryl-4-chlorophenylimino)ethyl)pyridyl nickel
dichloride (C13). In a manner similar to that described for C1,
C13 was prepared as a yellow powder in 91% yield. Anal. Calcd
for C39H31Cl3N2Ni (690.09) C, 67.62; H, 4.51; N, 4.04%;
Found: C, 67.52; H, 4.71; N, 4.00. FT-IR (Diamond; cm−1):
3060, 1616, 1596, 1568, 1495, 1429, 1318, 1180, 1027, 768,
698.
2-((2,6-Dibenzhydryl-4-isopropylphenylimino)methyl)pyridyl
nickel dichloride (C5). In a manner similar to that described for
C1, C5 was prepared as a yellow powder in 92% yield. Anal.
Calcd for C41H36Cl2N2Ni (684.16) C, 71.75; H, 5.29; N, 4.08;
This journal is © The Royal Society of Chemistry 2012
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Bis(2-((2,4-dibenzhydryl-6-methylphenylimino)methyl)pyridyl)-
nickel dibromide (D1). The ligand L1 0.264 g (0.5 mmol) and
(DME)NiBr2 0.154 g (0.25 mmol) was added to a Schlenk tube
together with 10 ml of dried ethanol. The reaction mixture was
then stirred for 12 h at room temperature and diethyl ether
(10 ml) was added to precipitate the complex. The precipitate
was washed with diethyl ether and dried in vacuum to obtain a
yellow powder in 83% yield. Anal. Calcd for C78H64Br2N4Ni
(1272.29) C, 73.43; H, 5.06; N, 4.39; Found: C, 73.24; H, 5.26;
N, 4.21. FT-IR (Diamond; cm−1): 3025, 1630, 1596, 1494,
1446, 1301, 1077, 1037, 770, 744, 699.
Bis(2-((2,4-dibenzhydryl-6-ethylphenylimino)ethyl)pyridyl)-
nickel dibromide (D9). In a manner similar to that described for
D1, D9 was prepared as a yellow powder in 85% yield. Anal.
Calcd for C82H72Br2N4Ni (1328.35) C, 73.94; H, 5.45; N, 4.21;
Found: C, 74.00; H, 5.55; N, 4.01. FT-IR (Diamond; cm−1):
3058, 1621, 1596, 1494, 1446, 1375, 1321, 1259, 1026, 738,
698.
Bis(2-((2,4-dibenzhydryl-6-isopropylphenylimino)ethyl)pyridyl)-
nickel dibromide (D10). In a manner similar to that described for
D1, D10 was prepared as a yellow powder in 87% yield. Anal.
Calcd for C84H76Br2N4Ni (1356.38) C, 74.18; H, 5.63; N, 4.12;
Found: C, 74.08; H, 5.83; N, 4.02. FT-IR (Diamond; cm−1):
2967, 1620, 1596, 1494, 1446, 1371, 1261, 1032, 747, 700.
Bis(2-((2,4-dibenzhydryl-6-ethylphenylimino)methyl)pyridyl)-
nickel dibromide (D2). In a manner similar to that described for
D1, D2 was prepared as a yellow powder in 85% yield. Anal.
Calcd for C80H68Br2N4Ni (1300.32) C, 73.69; H, 5.26; N, 4.30;
Found: C, 73.56; H, 5.35; N, 4.14. FT-IR (Diamond; cm−1):
3024, 1629, 1595, 1493, 1447, 1301, 1077, 1037, 770, 744,
698.
Bis(2-((2,6-dibenzhydryl-4-methylphenylimino)ethyl)pyridyl)-
nickel dibromide (D11). In a manner similar to that described
for D1, D11 was prepared as a yellow powder in 88% yield.
Anal. Calcd for C80H68Br2N4Ni (1300.32) C, 73.69; H, 5.26; N,
4.30; Found: C, 73.55; H, 5.32; N, 4.20. FT-IR (Diamond;
cm−1): 3027, 1618, 1595, 1493, 1442, 1316, 1256, 1032, 767,
700.
Bis(2-((2,4-dibenzhydryl-6-isopropylphenylimino)methyl)pyridyl)-
nickel dibromide (D3). In a manner similar to that described for
D1, D3 was prepared as a yellow powder in 83% yield. Anal.
Calcd for C82H72Br2N4Ni (1331.98) C, 73.94; H, 5.45; N, 4.21;
Found: C, 73.85; H, 5.68; N, 4.13. FT-IR (Diamond; cm−1):
2959, 1627, 1596, 1494, 1446, 1301, 1034, 768, 743, 699.
Bis(2-((2,6-dibenzhydryl-4-isopropylphenylimino)ethyl)pyridyl)-
nickel dibromide (D12). In a manner similar to that described for
D1, D12 was prepared as a yellow powder in 89% yield. Anal.
Calcd for C84H76Br2N4Ni (1356.38) C, 74.18; H, 5.63; N, 4.12;
Found: C, 74.00; H, 5.73; N, 4.02. FT-IR (Diamond; cm−1):
3025, 1621, 1596, 1493, 1442, 1255, 1070, 1035, 767, 700.
Bis(2-((2,6-dibenzhydryl-4-methylphenylimino)methyl)pyridyl)-
nickel dibromide (D4). In a manner similar to that described for
D1, D4 was prepared as a yellow powder in 88% yield. Anal.
Calcd for C78H64Br2N4Ni (1272.29) C, 73.43; H, 5.06; N, 4.39;
Found: C, 73.34; H, 5.16; N, 4.21. FT-IR (Diamond; cm−1):
3295, 1630, 1597, 1493, 1446, 1197, 1028, 760, 698.
Bis(2-((2,6-dibenzhydryl-4-chlorophenylimino)ethyl)pyridyl)-
nickel dibromide (D13). In a manner similar to that described
for D1, D13 was prepared as a yellow powder in 88% yield.
Anal. Calcd for C78H62Br2Cl2N4Ni (1340.21) C, 69.67; H, 4.65;
N, 4.17; Found: C, 69.77; H, 4.85; N, 4.07. FT-IR (Diamond;
cm−1): 3025, 1618, 1596, 1493, 1437, 1320, 1257, 1176, 1031,
767, 700.
Bis(2-((2,6-dibenzhydryl-4-isopropylphenylimino)methyl)pyridyl)-
nickel dibromide (D5). In a manner similar to that described for
D1, D5 was prepared as a yellow powder in 81% yield. Anal.
Calcd for C82H72Br2N4Ni (1331.98) C, 73.94; H, 5.45; N, 4.21;
Found: C, 73.80; H, 5.63; N, 4.12. FT-IR (Diamond; cm−1):
2960, 1635, 1597, 1492, 1444, 1157, 1075, 747, 699.
General considerations
Bis(2-((2,6-dibenzhydryl-4-chlorophenylimino)methyl)pyridyl)-
nickel dibromide (D6). In a manner similar to that described for
D1, D6 was prepared as a yellow powder in 82% yield. Anal.
Calcd for C76H58Br2Cl2N4Ni (1312.18) C, 69.33; H, 4.44; N,
4.26; Found: C, 69.50; H, 4.51; N, 4.15. FT-IR (Diamond;
cm−1): 3321, 1630, 1596, 1493, 1446, 1168, 1027, 760, 700.
All manipulations of air- and moisture-sensitive compounds
were performed under a nitrogen atmosphere using standard
Schlenk techniques. Toluene was refluxed over sodium–benzo-
phenone and distilled under nitrogen prior to use. Methylalumi-
noxane (MAO, 1.46 M solution in toluene) and modified
methylaluminoxane (MMAO, 1.93 M in heptane, 3A) were pur-
chased from Akzo Nobel Corp. Diethylaluminium chloride
(Et2AlCl, 1.7 M in toluene) and ethylaluminium sesquichloride
(Et3Al2Cl3, 0.87 M in toluene) were purchased from Acros
Chemicals. High-purity ethylene was purchased from Beijing
Yansan Petrochemical Co. and used as received. Other reagents
Bis(2-((2-benzhydryl-4,6-dimethylphenylimino)methyl)pyridyl)-
nickel dibromide (D7). In a manner similar to that described for
D1, D7 was prepared as a yellow powder in 83% yield. Anal.
Calcd for C54H48Br2N4Ni (968.16) C, 66.76; H, 4.98; N, 5.77;
Found: C, 66.75; H, 5.00; N, 5.61. FT-IR (Diamond; cm−1):
2894, 1631, 1591, 1493, 1444, 1305, 1129, 1025, 770, 744, 698.
1
were purchased from Aldrich, Acros, or local suppliers. H and
13C-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 analyses were carried out
using a Flash EA 1112 microanalyzer. The molecular weights
and molecular weight distributions of the polymers were deter-
mined by gel permeation chromatography (GPC) using a Waters
Alliance GPC 2000 instrument equipped with a refractive index
Bis(2-((2,4-dibenzhydryl-6-methylphenylimino)ethyl)pyridyl)-
nickel dibromide (D8). In a manner similar to that described for
D1, D8 was prepared as a yellow powder in 85% yield. Anal.
Calcd for C80H68Br2N4Ni (1300.32) C, 73.69; H, 5.26; N, 4.30;
Found: C, 73.59; H, 5.36; N, 4.20. FT-IR (Diamond; cm−1):
3033, 1622, 1595, 1493, 1445, 1372, 1319, 1259, 1026, 742,
698.
12008 | Dalton Trans., 2012, 41, 11999–12010
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Table 7 Crystal data and structure refinement for C1·2CH3OH, C5·2H2O, D4, D7 and D9
C1·2CH3OH
C5·2H2O
D4
D7
D9
Cryst. color
Empirical formula
Fw
Yellow
Yellow
Yellow
Yellow
C78H64Br2N4Ni
1275.82
173(2)
0.71073
Green
C80H70Cl4N4Ni2O2 C246H230Cl12N12Ni6O6 C54H48Br2N4Ni
1380.64
173(2)
0.71073
Monoclinic
P2(1)/n
18.888(16)
10.107(2)
20.625(4)
90
97.49(3)
90
3903.9(13)
2
1.175
0.664
1440
C82H71Br2N4Ni
1330.96
173(2)
0.71073
Monoclinic
P2(1)
15.921(3)
12.415(3)
18.706(3)
90
112.93(3)
90
3405.3(12)
2
1.299
1.506
1380
4228.08
173(2)
0.71073
Triclinic
ˉ
P1
18.912(4)
20.045(4)
22.057(4)
103.16(3)
109.38(3)
111.43(3)
6738(2)
971.49
173(2)
0.71073
Monoclinic
P2(1)/c
14.822(3)
15.439(3)
9.767(2)
90
95.39(3)
90
2225.2(8)
2
T (K)
Wavelength (Å)
Cryst. syst.
Space group
a (Å)
b (Å)
c (Å)
Triclinic
ˉ
P1
11.955(2)
12.075(2)
14.474(3)
94.80(3)
112.89(3)
93.79(3)
1907.0(6)
1
α (°)
β (°)
γ (°)
V (Å3)
Z
D
1
calcd (mg m−3
)
1.042
0.578
2210
1.450
2.274
996
1.111
1.342
658
μ (mm−1
F(000)
)
Cryst size (mm)
θ range (°)
Limiting indices
0.27 × 0.20 × 0.15
1.38–27.52
−24 ≤ h ≤ 15
−13 ≤ k ≤ 12
−26 ≤ l ≤ 26
19 692
8898 (0.0477)
99.2
Empirical
8898/0/403
1.114
R1 = 0.0637,
wR2 = 0.1680
R1 = 0.0763,
wR2 = 0.1779
0.537 and −0.519
0.18 × 0.10 × 0.08
1.07–25.34
−22 ≤ h ≤ 22
−22 ≤ k ≤ 24
−26 ≤ l ≤ 25
54 230
24 513 (0.0615)
99.3
Empirical
24 513/11/1240
1.039
R1 = 0.0942,
wR2 = 0.2709
R1 = 0.1276,
wR2 = 0.2996
0.734 and −1.179
0.20 × 0.12 × 0.10 0.42 × 0.36 × 0.26 0.18 × 0.15 × 0.05
1.38–27.55
−18 ≤ h ≤ 19
−20 ≤ k ≤ 12
−12 ≤ l ≤ 12
11 332
5083 (0.0512)
98.9
1.54–27.48
−15 ≤ h ≤ 15
−14 ≤ k ≤ 15
−26 ≤ l ≤ 26
17 090
8677 (0.0358)
99.2
1.18–26.02
−19 ≤ h ≤ 19
−15 ≤ k ≤ 13
−23 ≤ l ≤ 20
15 957
11 537 (0.0466)
99.2%
No. of rflns collected
No. unique rflns [R(int)]
Completeness to θ (%)
Abs corr
Data/restraints/params
Goodness of fit on F2
Final R indices [I > 2σ(I)]
Empirical
5083/0/277
1.172
Empirical
8677/0/385
1.070
Empirical
11 537/40/882
1.076
R1 = 0.0823,
wR2 = 0.1943
R1 = 0.1072,
wR2 = 0.2149
0.752 and −0.625
R1 = 0.0538,
wR2 = 0.1486
R1 = 0.0635,
wR2 = 0.1538
0.570 and −0.552
R1 = 0.0779,
wR2 = 0.1413
R1 = 0.0960,
wR2 = 0.1536
0.600 and −0.419
R indices (all data)
Largest diff peak and hole (e Å−3
)
(RI) detector and a set of u-Styragel HT columns of 106, 105,
104 and 103 pore size in series. The measurement was performed
at 135 °C with 1,2,4-trichlorobenzene as the eluent at a flow rate
of 0.95 mL min−1. Narrow-molecular-weight PS samples were
used as standards for calibration.
on a Rigaku Saturn724+ CCD with graphite monochromated
Mo Kα radiation (λ = 0.71073 Å). Cell parameters were obtained
by global refinement of the positions of all collected reflections.
Intensities were corrected for Lorentz and polarization effects
and empirical absorption. The structures were solved by direct
methods and refined by full-matrix least squares on F2. All
hydrogen atoms were placed in calculated positions. Structure
solution and refinement were performed by using the
SHELXTL-97 package.20 During structure refinement of
C1·2CH3OH, C5·2H2O, D7 and D9, there were several dis-
ordered solvents that could neither be identified unambiguously
nor be refined well. Therefore, it was impossible to determine
the number and the identity of these disordered solvents defini-
tively by means of single-crystal X-ray diffraction. The
SQUEEZE option of the crystallographic program PLATON21
was used to remove these disordered solvents from the structures
of C1·2CH3OH, C5·2H2O, D7 and D9; the geometry of the
main compounds remained unaffected by employing SQUEEZE.
Crystal data and processing parameters for C1·2CH3OH,
C5·2H2O, D4, D7 and D9 are summarized in Table 7.
Procedure for polymerization at higher ethylene pressure
Ethylene polymerizations were performed in a 250 mL autoclave
stainless steel reactor equipped with a mechanical stirrer and a
temperature controller. A 100 mL amount of toluene containing
the catalyst precursor was transferred to the fully dried reactor
under an ethylene atmosphere. The required amount of co-cata-
lyst (MAO, MMAO or Et2AlCl) was then injected into the
reactor via a syringe. At the desired reaction temperature, the
reactor was sealed and pressurized to high ethylene pressure, and
the ethylene pressure was maintained by feeding in ethylene.
After the reaction mixture was stirred for the desired period, the
pressure was released, and then the residual reaction solution
was quenched with 5% hydrochloric acid in ethanol.
X-ray crystallography
Acknowledgements
Single-crystals of C1·2CH3OH, 3(C5·2H2O), D4, D7 and D9
suitable for X-ray diffraction were obtained by the slow diffusion
of diethyl ether into the methanol solution. Data were collected
This work is supported by NSFC No. 20904059 as well as the
MOST 863 program No. 2009AA034601. The EPSRC are
thanked for the award of a travel grant (to CR).
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 11999–12010 | 12009

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Lett., 2001, 12, 691; (d) J. M. Benito, E. De Jesús, F. J. de la Mata,
J. C. Flores, R. Gómez and P. Gómez-Sal, Organometallics, 2006, 25,
3876; (e) X. Tang, W.-H. Sun, T. Gao, J. Hou, J. Chen and W. Chen,
J. Organomet. Chem., 2005, 690, 1570; (f) S. Jie, D. Zhang, T. Zhang,
W.-H. Sun, J. Chen, Q. Ren, D. Liu, G. Zheng and W. Chen, J. Organo-
met. Chem., 2005, 690, 1739; (g) C. Shao, W.-H. Sun, Z. Li, Y. Hu and
L. Han, Catal. Commun., 2002, 3, 405; (h) J. Li, T. Gao, W. Zhang and
W.-H. Sun, Inorg. Chem. Commun., 2003, 6, 1372; (i) X. Tang, Y. Cui,
W.-H. Sun, Z. Miao and S. Yan, Polym. Int., 2004, 53, 2155;
( j) G. J. P. Britovsek, S. P. D. Baugh, O. Hoarau, V. C. Gibson,
D. F. Wass, A. J. P. White and D. Williams, Inorg. Chim. Acta, 2003,
345, 279; (k) R. Gao, L. Xiao, X. Hao, W.-H. Sun and F. Wang, Dalton
Trans., 2008, 5645; (l) F. Yang, Y. Chen, Y. Lin, K. Yu, Y. Liu, Y. Wang,
S. Liu and J.-T. Chen, Dalton Trans., 2009, 1243; (m) S. Song, T. Xiao,
T. Liang, F. Wang, C. Redshaw and W.-H. Sun, Catal. Sci. Technol.,
2011, 1, 69; (n) J. Yu, Y. Zeng, W. Huang, X. Hao and W.-H. Sun,
Dalton Trans., 2011, 40, 8436; (o) L. Zhang, X. Hao, W.-H. Sun and
C. Redshaw, ACS Catal., 2011, 1, 1213; (p) J. Yu, X. Hu, Y. Zeng,
L. Zhang, C. Ni, X. Hao and W.-H. Sun, New J. Chem., 2011, 35, 178;
(q) W. Chai, J. Yu, L. Wang, X. Hu, C. Redshaw and W.-H. Sun, Inorg.
Chim. Acta, 2012, 385, 21; (r) X. Hou, T. Liang, W.-H. Sun, C. Redshaw
and X. Chen, J. Organomet. Chem., 2012, 708–709, 98.
References
1 (a) G. J. P. Britovsek, V. C. Gibson and D. F. Wass, Angew. Chem., Int.
Ed., 1999, 38, 428; (b) S. D. Ittel, L. K. Johnson and M. Brookhart,
Chem. Rev., 2000, 100, 1169; (c) S. Mecking, Coord. Chem. Rev., 2000,
203, 325; (d) V. C. Gibson and S. K. Spitzmesser, Chem. Rev., 2003,
103, 283; (e) F. Speiser, P. Braunstein and L. Saussine, Acc. Chem. Res.,
2005, 38, 784; (f) W.-H. Sun, D. Zhang, S. Zhang, S. Jie and J. Hou,
Kinet. Catal., 2006, 47, 278; (g) C. Bianchini, G. Giambastiani,
G. I. Rios, G. Mantovani, A. Meli and A. M. Segarra, Coord. Chem.
Rev., 2006, 250, 1391; (h) V. C. Gibson, C. Redshaw and G. A. Solan,
Chem. Rev., 2007, 107, 1745; (i) Y. Song, S. Zhang, Y. Deng, S. Jie,
L. Li, X. Lu and W.-H. Sun, Kinet. Catal., 2007, 48, 664; ( j) S. Jie,
W.-H. Sun and T. Xiao, Chin. J. Polym. Sci., 2010, 28, 299;
(k) C. Bianchini, G. Giambastiani, L. Luconi and A. Meli, Coord. Chem.
Rev., 2010, 254, 431; (l) T. Xiao, W. Zhang, J. Lai and W.-H. Sun,
C. R. Chim., 2011, 14, 851.
2 (a) B. L. Small, M. Brookhart and A. M. M. Bennett, J. Am. Chem. Soc.,
1998, 120, 4049; (b) B. L. Small and M. Brookhart, J. Am. Chem. Soc.,
1998, 120, 7143; (c) G. J. P. Britovsek, V. C. Gibson, B. S. Kimberley,
P. J. Maddox, S. J. McTavish, G. A. Solan, A. J. P. White and
D. J. Williams, Chem. Commun., 1998, 849; (d) 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
and D. J. Williams, J. Am. Chem. Soc., 1999, 121, 8728.
3 (a) L. K. Johnson, C. M. Killian and M. Brookhart, J. Am. Chem. Soc.,
1995, 117, 6414; (b) C. M. Killian, D. J. Tempel, L. K. Johnson and
M. Brookhart, J. Am. Chem. Soc., 1996, 118, 11664; (c) S. A. Svejda,
L. K. Johnson and M. Brookhart, J. Am. Chem. Soc., 1999, 121, 10634;
(d) D. P. Gates, S. A. Svejda, E. Oñate, C. M. Killian, L. K. Johnson,
P. S. White and M. Brookhart, Macromolecules, 2000, 33, 2320.
4 (a) L. K. Johnson, S. Mecking and M. Brookhart, J. Am. Chem. Soc.,
1996, 118, 267; (b) S. Mecking, L. K. Johnson, L. Wang and
M. Brookhart, J. Am. Chem. Soc., 1998, 120, 888; (c) S. R. Foley,
R. A. Stockland, H. Shen and R. F. Jordan, J. Am. Chem. Soc., 2003,
125, 4350; (d) E. Drent, R. van Dijk, R. van Ginkel, B. van Oort and
R. I. Pugh, Chem. Commun., 2002, 744; (e) E. Drent, R. van Dijk, R. van
Ginkel, B. van Oort and R. I. Pugh, Chem. Commun., 2002, 964;
(f) S. Luo and R. F. Jordan, J. Am. Chem. Soc., 2006, 128, 12072;
(g) S. Luo, J. Vela, G. R. Lief and R. F. Jordan, J. Am. Chem. Soc., 2007,
129, 8946; (h) T. Kochi, S. Noda, K. Yoshimura and K. Nozaki, J. Am.
Chem. Soc., 2007, 129, 8948; (i) W. Weng, Z. Shen and R. F. Jordan,
J. Am. Chem. Soc., 2007, 129, 15450; ( j) C. Chen, S. Luo and
R. F. Jordan, J. Am. Chem. Soc., 2008, 130, 12892; (k) S. Ito,
K. Munakata, A. Nakamura and K. Nozaki, J. Am. Chem. Soc., 2009,
131, 14606; (l) C. Chen, S. Luo and R. F. Jordan, J. Am. Chem. Soc.,
2010, 132, 5273; (m) K. Nozaki, S. Kusumoto, S. Noda, T. Kochi, L.
W. Chung and K. Morokuma, J. Am. Chem. Soc., 2010, 132, 16030;
(n) A. Nakamura, S. Ito, K. Munakata, T. Kochi, L. W. Chung,
K. Morokuma and K. Nozaki, J. Am. Chem. Soc., 2011, 133, 6761;
(o) S. Ito, M. Kanazawa, K. Munakata, J.-I. Kuroda, Y. Okumura and
K. Nozaki, J. Am. Chem. Soc., 2011, 133, 1232.
10 (a) T. V. Laine, U. Piironen, K. Lappalainen, M. Klinga, E. Aitola and
M. Leskel, J. Organomet. Chem., 2000, 606, 112; (b) T. V. Laine,
M. Klinga and M. Leskelä, Eur. J. Inorg. Chem., 1999, 959;
(c) T. V. Laine, M. Klinga, A. Maaninen, E. Aitola and M. Leskel, Acta
Chem. Scand., 1999, 53, 968; (d) A. Köppl and H. G. Alt, J. Mol. Catal.
A: Chem., 2000, 154, 45; (e) Z. Huang, K. Song, F. Liu, J. Long, H. Hu,
H. Gao and Q. Wu, J. Polym. Sci., Part A: Polym. Chem., 2008, 46, 1618;
(f) T. V. Laine, K. Lappalainen, J. Liimatta, E. Aitola1, B. Löfgren and
M. Leskelä, Macromol. Rapid Commun., 1999, 20, 487;
(g) G. J. P. Britovsek, S. P. D. Baugh, O. Hoarau, V. C. Gibson, D. F. Wass,
A. J. P. White and D. J. Williams, Inorg. Chim. Acta, 2003, 345, 279;
(h) V. C. Gibson, C. M. Halliwell, N. J. Long, P. J. Oxford, A. M. Smith,
A. J. P. White and D. J. Williams, Dalton Trans., 2003, 918.
11 (a) Q.-Z. Yang, A. Kermagoret, M. Agostinho, O. Siri and P. Braunstein,
Organometallics, 2006, 25, 5518; (b) P. Hao, S. Zhang, W.-H. Sun,
Q. Shi, S. Adewuyi, X. Lu and P. Li, Organometallics, 2007, 26, 2439.
12 F. Speiser, P. Braunstein and L. Saussine, Dalton Trans., 2004, 1539.
13 (a) J. Hou, W.-H. Sun, S. Zhang, H. Ma, Y. Deng and X. Lu, Organo-
metallics, 2006, 25, 236; (b) C. Zhang, W.-H. Sun and Z.-X. Wang,
Eur. J. Inorg. Chem., 2006, 4895.
14 (a) L. Wang, W.-H. Sun, L. Han, H. Yang, Y. Hu and X. Jin, J. Organo-
met. Chem., 2002, 658, 62; (b) F. A. Kunrath, R. F. Souza, Jr.,
O. L. Casagrande, N. R. Brooks Jr. and V. G. Young, Organometallics,
2003, 22, 4739; (c) N. Ajellal, M. C. A. Kuhn, A. D. G. Boff, M. Hörner,
C. M. Thomas, J.-F. Carpentier, Jr. and O. L. Casagrande, Organometal-
lics, 2006, 25, 1213; (d) W.-H. Sun, S. Zhang, S. Jie, W. Zhang, Y. Li,
H. Ma, J. Chen, K. Wedeking and R. Fröhlich, J. Organomet. Chem.,
2006, 691, 4196; (e) W.-H. Sun, K. Wang, K. Wedeking, D. Zhang,
S. Zhang, J. Cai and Y. Li, Organometallics, 2007, 26, 4781; (f) R. Gao,
M. Zhang, T. Liang, F. Wang and W.-H. Sun, Organometallics, 2008, 27,
5641; (g) K. Wang, R. Gao, X. Hao and W.-H. Sun, Catal. Commun.,
2009, 10, 1730.
15 (a) J. Yu, H. Liu, W. Zhang, X. Hao and W.-H. Sun, Chem. Commun.,
2011, 47, 3257; (b) W. Zhao, J. Yu, S. Song, W. Yang, H. Liu, X. Hao,
C. Redshaw and W.-H. Sun, Polymer, 2012, 53, 130; (c) J. Yu,
W. Huang, L. Wang, C. Redshaw and W.-H. Sun, Dalton Trans., 2011,
40, 10209.
5 (a) J. Pietsch, P. Braunstein and Y. Chauvin, New J. Chem., 1998, 22,
467; (b) W. Liu, J. M. Malinoski and M. Brookhart, Organometallics,
2002, 21, 2836.
6 N. A. Cooley, S. M. Green and D. F. Wass, Organometallics, 2001, 20,
4769.
7 (a) T. R. Younkin, E. F. Connor, J. I. Henderson, S. K. Friedrich,
R. H. Grubbs and D. A. Bansleben, Science, 2000, 287, 460; (b) T. Hu,
L.-M. Tang, X.-F. Li, Y.-S. Li and N.-H. Hu, Organometallics, 2005, 24,
2628; (c) L. Wang, W.-H. Sun, L. Han, Z. Li, Y. Hu, C. He and C. Yan,
J. Organomet. Chem., 2002, 650, 59; (d) A. Kermagoret and
P. Braunstein, Dalton Trans., 2008, 1564; (e) C. Carlini, M. Isola,
V. Liuzzo, A. M. R. Galletti and G. Sbrana, Appl. Catal., A, 2002, 231,
307.
8 (a) W. Keim, S. Killat, C. F. Nobile, G. P. Suranna, U. Englert, R. Wang,
S. Mecking and D. L. Schröder, J. Organomet. Chem., 2002, 662, 150;
(b) F. Speiser, P. Braunstein and L. Saussine, Organometallics, 2004, 23,
2633; (c) F. Speiser, P. Braunstein, L. Saussine and R. Welter, Inorg.
Chem., 2004, 43, 1649; (d) Z. Weng, S. Teo and T. S. A. Hor, Organo-
metallics, 2006, 25, 4878; (e) Z. Guan and W. J. Marshall, Organometal-
lics, 2002, 21, 3580.
16 (a) H. Liu, W. Zhao, X. Hao, C. Redshaw, W. Huang and W.-H. Sun,
Organometallics, 2011, 30, 2418; (b) H. Liu, W. Zhao, J. Yu, W. Yang,
X. Hao, C. Redshaw, L. Chen and W.-H. Sun, Catal. Sci. Technol., 2012,
2, 415; (c) X. Hou, Z. Cai, X. Chen, L. Wang, C. Redshaw and
W.-H. Sun, Dalton Trans., 2012, 41, 1617; (d) J. Lai, X. Hou, Y. Liu,
C. Redshaw and W.-H. Sun, J. Organomet. Chem., 2012, 702, 52.
17 T. Usami and S. Takayama, Polym. J., 1984, 16, 731.
18 (a) E. F. Connor, T. R. Younkin, J. I. Henderson, A. W. Waltman and
R. H. Grubbs, Chem. Commun., 2003, 2272; (b) V. C. Gibson,
C. K. A. Gregson, C. M. Halliwell, N. J. Long, P. J. Oxford, A. J. P. White
and D. J. Williams, J. Organomet. Chem., 2005, 690, 6271.
19 G. B. Galland, R. F. de Souza, R. S. Mauler and F. F. Nunes, Macromole-
cules, 1999, 32, 1620.
20 G. M. Sheldrick, SHELXTL-97 Program for the Refinement of Crystal
Structures, University of Göttingen, Germany, 1997.
21 A. L. Spek, Acta Crystallogr., Sect. D: Biol. Crystallogr., 2009, D65, 148.
9 (a) S. A. Svejda and M. Brookhart, Organometallics, 1999, 18, 65;
(b) B. Y. Lee, X. Bu and G. C. Bazan, Organometallics, 2001, 20, 5425;
(c) Z. L. Li, W. H. Sun, Z. Ma, Y. L. Hu and C. X. Shao, Chin. Chem.
12010 | Dalton Trans., 2012, 41, 11999–12010
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