2,6-dibenzhydryl- N -(2-phenyliminoacenaphthylenylidene)-4- methylbenzenamine nickel dibromides: Synthesis, characterization, and ethylene polymerization

Article abstract of DOI:10.1021/om200154a

A series of 2,6-dibenzhydryl-N-(2-phenyliminoacenaphthylenylidene)-4- methylbenzenamines (L1-L5) and the nickel(II) dibromide complexes thereof (C1-C5) were synthesized and fully characterized. The molecular structures of representative complexes were determined by single-crystal X-ray diffraction and revealed a distorted-pyramidal geometry at nickel. All nickel(II) procatalysts exhibited very high activity for the polymerization of ethylene, with activities as high as the range of 10⁷ g of PE (mol of Ni)^-1 h ^-1.

Full text of DOI:10.1021/om200154a

ARTICLE
pubs.acs.org/Organometallics
2,6-Dibenzhydryl-N-(2-phenyliminoacenaphthylenylidene)-4-
methylbenzenamine Nickel Dibromides: Synthesis,
Characterization, and Ethylene Polymerization
Hao Liu,† Weizhen Zhao,† Xiang Hao,† Carl Redshaw,*,‡ Wei Huang,† and Wen-Hua Sun*,†,§
†Key Laboratory of Engineering Plastics and Beijing Natural Laboratory for Molecular Science, Institute of Chemistry,
Chinese Academy of Sciences, Beijing 100190, People's Republic of China
‡School of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K.
§State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics,
Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China
S Supporting Information
b
ABSTRACT: A series of 2,6-dibenzhydryl-N-(2-phenyliminoacenaphthylenylidene)-4-methylben-
zenamines (L1ꢀL5) and the nickel(II) dibromide complexes thereof (C1ꢀC5) were synthesized
and fully characterized. The molecular structures of representative complexes were determined by
single-crystal X-ray diffraction and revealed a distorted-pyramidal geometry at nickel. All nickel(II)
procatalysts exhibited very high activity for the polymerization of ethylene, with activities as high as
the range of 107 g of PE (mol of Ni)ꢀ1 hꢀ1
.
designed in recent years.15 Indeed, even now, driven by the thirst
for new polyethylene materials with high molecular weight and
extraordinary properties, researchers continue to develop new
ligand systems with the potential to induce high catalytic activity,
new product properties, or better still both of these features.
Although substantial work has been conducted on substituent
variation for the diimine ligand set, with much of the focus on
changing the N-bound aryl group16 or modifying the back-
bone,16,17 including the use of axial donating diimine ligands,18
unsymmetrical diimine ligands still remain rare.19 Previous studies
have shown that the phenyl ring orientation places the bulky
substituents in axial sites, which effectively retards the rate of chain
transfer relative to chain propagation.20 The present goal is to
synthesize a new bulky aniline which when incorporated into the
R-diimine system will prohibit free rotation about the arylꢀnitro-
gen bonds and thereby induce novel catalytic features for the
resulting metal procatalysts. Such a feature has been employed to
good effect in Guan’s cyclophane-based nickel complexes21 and
our recent unsymmetrical bis(imino)pyridyliron procatalysts.22
Herein, the synthesis, characterization, and catalytic behavior of
the 2,6-dibenzhydryl-N-(2-phenyliminoacenaphthylenylidene)-4-
methylbenzenamine nickel complexes (C1ꢀC5) are reported.
These new bulky unsymmetrical R-diimine nickel procatalysts are
capable of ethylene polymerization with high activity up to a value
1. INTRODUCTION
In comparison with early-metal-based systems, late-transition-
metal catalysts have some unique features1 which have led to great
interest in this field in the last few decades. In particular, following
the observations by Brookhart and co-workers,2 the number of
research papers in this area has mushroomed.3 We have been
attracted by the use of N∧N∧N tridentate procatalysts and have
designed a number of new ligands, namely 2-imino-1,10-
phenanthrolines,4 2-(2- benzimidazolyl)-1,10-phenanthrolines,5
2-(benzoxazolyl)-1,10-phenanthrolines,6 2-(2-benzimidazolyl)-
6-(1-(arylimino)ethyl) pyridines,7 2-(benzoxazolyl)-6-(1-(aryli-
mino)ethyl)pyridines,8 and 2-quinoxalinyl-6-iminopyridines.9 The
metal complexes with these ligands exhibited favorable catalytic
activity for either the selective oligomerization or polymerization
of ethylene. At the same time, we have also reported N∧N
bidentate procatalysts utilizing ligands such as 2-(2-pyridyl)
quinoxaline,10 2-ethylcarboxylate-6-iminopyridine,11 and pyrazoly-
liminophosphorane.12
In general, late-transition-metal olefin oligo-/polymerization
catalysts tend to utilize one of the metals iron, cobalt, nickel, and
palladium.13 Both iron(II)- and nickel(II)-based systems have
been shown to be very adaptable in terms of their ability to afford
a variety of products.14 This has been achieved by simple tuning
of the ancillary ligand set, which allows the product compositions
to vary from that of small oligomers to high molecular weight
polyethylene with narrow molecular weight distribution. In the
case of R-diimines, either the ligand backbone or the substituents
associated with the N-bound aryl can readily be manipulated to
suit the required electronic and/or steric features.1 As a result, a
variety of ligand sets for polymerization catalysts have been
of 107 g of PE (mol of Ni)ꢀ1 ꢀ1. Interestingly, the polymer
h
produced with different cocatalysts (Et2AlCl or MAO) possessed
quite diverse microstructures.
Received: February 18, 2011
Published: March 22, 2011
r
2011 American Chemical Society
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Scheme 1. Synthesis of Ligands (L1ꢀL5) and Nickel Com-
plexes (C1ꢀC5)
Figure 1. ORTEP drawing of C4. Thermal ellipsoids are shown at the
30% probability level. Hydrogen atoms have been omitted for clarity.
2. RESULTS AND DISCUSSION
2.1. Synthesis and Characterization of Ligands and Com-
plexes. The stoichiometric condensation reaction of acenaphthy-
lene-1,2-dione and 2,6-dibenzhydryl-4-methylaniline produced
the2-(2,6-dibenzhydryl-4-methylphenylimino)acenaphthylenone,
which further reacted with various anilines to afford the unsymme-
trical R-diimines 2,6-dibenzhydryl-N-(2-phenyliminoacenaphthy-
lenylidene)-4-methylbenzenamine (L1ꢀL5) (Scheme 1). All
newly synthesized R-diimines (L) on reaction with nickel(II) di-
bromide in dichloromethane formed R-diimine nickel(II) dibro-
mide complexes (C1ꢀC5) in good yields (Scheme 1). The nickel
complexes were characterized by IR spectra and elemental analysis.
2.2. X-ray Crystallographic Studies. Single crystals of com-
plexes C4 and C5 suitable for X-ray diffraction analysis were
grown by slow diffusion of diethyl ether into dichloromethane
solutions. The molecular structures of complexes C4 and C5
were confirmed by single-crystal X-ray diffraction. The molecular
structures are shown in Figures 1 and 2, respectively, and selected
bond lengths and angles are tabulated in Table S1 of the
Supporting Information. As shown in Figure 1, the coordination
geometry of C4 can be best described as a distorted tetrahedron,
with the three atoms N1, N2, and Br2 forming the basal plane
and the Br1 atom occupying the apical position. The nickel atom
is 0.892 Å away from the basal plane. The plane composed by N1,
N2, and Ni1 and the basal plane form a dihedral angle of 35.9°.
The dihedral angles between the aryl ring on N1 and the basal
plane and between the aryl ring on N2 and the basal plane are
49.5 and 48.6°, respectively. There is a fused five-membered ring
of nickel and the ligand with an acute angle N1ꢀNi1ꢀN2 of
83.03(14)° and bond distances Ni1ꢀN1 = 2.040(3) Å and
Figure 2. ORTEP drawing of C5. Thermal ellipsoids are shown at the
30% probability level. Hydrogen atoms have been omitted for clarity.
Ni1ꢀN2 = 2.027(3) Å. The bond lengths N1ꢀC12 and
N2ꢀC1 of the imino functions are 1.284(5) and 1.281(5) Å,
respectively, both of which are typical of CdN double-bond
character.
In the structure of C5, the nickel atom is surrounded by
an N-(2-(2,6-dibenzhydryl-4-methylphenylimino)acenaphthyl-
enylidene)-2,6-diethyl-4-methylbenzenamine ligand and bound
by two terminal bromides. Similar to the case for C4, the
geometry of the four-coordinate complex can be described
as a distorted tetrahedron, with the plane composed by the
three atoms N1, N2, and Br2 as the basal plane and the Br1
atom occupying the apical position. The plane composed
by N1, N2, and Ni1 and the basal plane form a dihedral angle
of 35.6°. The dihedral angles between the aryl ring on N1
and the basal plane and between the aryl ring on N2 and the
bottom plane are 51.4 and 52.1°, respectively, both greater than
those observed for C4. The C5 bond distances Ni1ꢀN1 =
2.039(2) Å and Ni1ꢀN2 = 2.010(3) Å are similar to those
observed for C4. The bond lengths associated with the imino
functions N1ꢀC12 and N2ꢀC1 are 1.291(4) and 1.286(4) Å,
respectively.
2.3. Ethylene Polymerization. In order to determine the most
suitable cocatalyst, initial investigations of procatalyst C4 were
conducted with various alkylaluminum reagents, such as ethyla-
luminum sesquichloride (Et3Al2Cl3, EASC), methylaluminoxane
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Table 1. Ethylene Polymerization by Procatalyst C4 with Various Cocatalystsa
b
entry
cocat.
Al/Ni
T/°C
t/min
activity/106 g of PE (mol of Ni)ꢀ1 hꢀ1
Mwb/105 g molꢀ1
Mw/Mn
Tmc/°C
1
2
3
4
MAO
1000
1000
200
20
20
20
20
30
30
30
30
3.30
trace
6.08
trace
12.78
21
91.8
MMAO
Et2AlCl
EASC
10.43
2.8
82.3
200
a Conditions: 1.5 μmol of Ni; 30 min; 10 atm of ethylene; total volume 100 mL. b Determined by GPC. c Determined by DSC.
Table 2. Catalytic Results of Ethylene Polymerization with C1ꢀC5/Et2AlCla
activity/106 g of PE (mol of Ni)ꢀ1 hꢀ1
Mwb/105 g molꢀ1
Mw/Mn
Tmc/°C
b
entry
procat.
Al/Ni
T/°C
t/min
1
C4
C4
C4
C4
C4
C4
C4
C4
C4
C1
C2
C3
C5
C4
C4
C4
C4
400
500
600
700
800
1000
600
600
600
600
600
600
600
600
600
600
600
20
20
20
20
20
20
40
60
50
20
20
20
20
20
20
20
20
30
30
30
30
30
30
30
30
30
30
30
30
30
5
9.28
10.7
10.8
10.6
9.88
9.83
6.36
4.48
4.81
9.95
6.88
10.9
8.53
13.0
11.8
10.9
6.65
5.43
5.55
5.97
6.08
6.74
7.43
4.62
2.98
4.68
4.72
6.87
9.42
7.74
5.63
5.69
5.81
7.95
2.4
2.2
2.2
2.5
2.6
2.5
2.3
2.2
2.2
2.4
2.3
2.7
2.4
2.2
2.3
2.4
2.7
65.2
65.2
78.4
79.7
70.1
69.2
48.7
2
3
4
5
6
7
8
9
29.1
56.2
65.2
49.1
80.8
58.7
53.6
52.9
78.4
10
11
12
13
14
15
16
17
10
20
60
a Conditions: 1.5 μmol of Ni; 30 min; 10 atm of ethylene; total volume 100 mL. b Determined by GPC. c Determined by DSC.
(MAO), modified methylaluminoxane (MMAO), and diethyla-
luminum chloride (Et2AlCl), at room temperature under
10 atm of ethylene (see Table 1). It was found that Et2AlCl was
found to be the most effective cocatalyst. Although the C4/MAO
catalyst system did not present the dominant activities, it was observed
to afford a diverse array of polymer products. For this reason, the
catalytic behavior of C4/MAO was also investigated in detail.
2.3.1. Ethylene Polymerization with C1ꢀC5/Et2AlCl System.
The catalytic behavior of complex C4 was evaluated for optimum
conditions in the presence of either Et2AlCl or MAO. In the
presence of Et2AlCl, reaction parameters such as molar ratios of
Et2AlCl to nickel and reaction temperatures are collected in
Table 2. From the data, it was observed that the catalytic activity
was enhanced on increasing the Al/Ni ratio from 200 up to 600
(entry 3 in Table 1 and entries 1ꢀ3 in Table 2), and for the
C4/Et2AlCl catalyst system, the highest activity was 1.30 ꢁ 107 g
of PE (mol of Ni)ꢀ1 hꢀ1 within 5 min (entry 14 in Table 2) and
1.08 ꢁ 107 g of PE (mol of Ni)ꢀ1 hꢀ1 within 30 min (entry 3 in
Table 2). However, a slight decrease of activity was observed on
further increasing the Al/Ni ratio from 600 to 1000 (entries 3ꢀ6
in Table 2). Thus, the most suitable molar ratio of Al to Ni
was 600:1 (entry 3 in Table 2), while the best performance was
observed at 20 °C (entries 3 and 7ꢀ9 in Table 2). Further
elevating the temperature from 20 to 60 °C led to a marked
decrease of activity, while simultaneously the molecular
weights exhibited the reverse trend, which is similar to the
situation previously observed for reported R-diimine catalyst
Figure 3. 13C NMR spectrum of polyethylene prepared with catalyst
C4/AlEt2Cl (entry 8 in Table 2).
systems.16aꢀe The other procatalysts were also found to have
good activity for ethylene polymerization, and the data are
summarized in Table 2.
The melting temperatures of the polyethylenes obtained
were found to be lower than 81 °C. Such unusual properties
were caused by the polyethylenes with high branches, which
were confirmed by the 13C NMR measurements. As shown in
Figure 3, the number of branches was calculated according to the
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Table 3. Catalytic Results of Ethylene Polymerization with C1ꢀC5/MAOa
b
entry
procat.
Al/Ni
T/°C
T/min
activity/106 g of PE (mol of Ni)ꢀ1 hꢀ1
Mwb/105 g molꢀ1
Mw/Mn
Tmc/°C
1
C4
C4
C4
C4
C4
C4
C4
C4
C1
C2
C3
C5
C4
C4
C4
C4
2000
2500
3000
3500
4000
3000
3000
3000
3000
3000
3000
3000
3000
3000
3000
3000
20
20
20
20
20
40
60
50
20
20
20
20
20
20
20
20
30
30
30
30
30
30
30
30
30
30
30
30
5
7.21
8.94
9.32
6.34
4.08
5.41
4.37
4.90
9.23
7.73
9.39
1.89
10.6
10.2
9.60
6.10
nd
nd
57.2
81.7
75.3
75.8
90.3
60.2
36.5
92.2
90.8
69.7
62.7
76.2
69.2
49.6
81.2
90.8
2
6.18
6.99
7.62
8.13
5.63
3.67
3.53
6.74
6.77
7.45
7.44
5.76
5.84
6.02
8.85
2.4
2.5
2.6
3.1
2.4
2.2
2.4
2.5
2.6
2.5
2.7
2.5
2.5
2.6
3.3
3
4
5
6
7
8
9
10
11
12
13
14
15
16
10
20
60
a Conditions: 1.5 μmol of Ni; 30 min; 10 atm of ethylene; total volume: 100 mL. b Determined by GPC. c Determined by DSC.
literature,23 and it was found that the polyethylene with 337
branches/1000 carbons (Figure 3) was obtained at 60 °C (entry
8 in Table 2), while the polyethylene with 99 branches/1000
carbons (Figure S1, Supporting Information) was obtained at
20 °C (entry 3 in Table 2). Using routine DSC procedures, the
polyethylenes were heated during the first scan, and then cooled
back down to room temperature, whereupon the kinetic proper-
ties remained for highly branched polyethylenes, which resulted
in some of the Tm values obtained being quite low.
2.3.2. Ethylene Polymerization with C1ꢀC5/MAO System.
Using MAO as cocatalyst, all nickel procatalysts (C1ꢀC5) also
showed good catalytic activities toward ethylene polymerization,
and the data are tabulated in Table 3. From the table, better
activities were observed on increasing the Al/Ni molar ratio from
2000 to 3000 (entries 1ꢀ3 in Table 3). When the Al/Ni molar
ratio is further increased to 4000, a slight decrease in the activity
was observed. Similar to the case for the C4/Et2AlCl catalytic
system, the molecular weights and distributions both gradually
increased with an increase in Al:Ni molar ratios for the C4/MAO
catalytic system (entries 2ꢀ5 in Table 3). The best performance
was observed at 20 °C (entry 3 and entries 6ꢀ8 in Table 3), and
the molecular weights decreased upon an increase in the
temperature (entries 3, 6, and 7 in Table 3). The polymerization
activity, similar to that for the C1ꢀC5/Et2AlCl system, de-
creased in the order C4 [2,4,6-tri(Me)] > C5 [2,6-di(Et)-4-Me],
C3 [2,6-di(i-Pr)] > C1 [2,6-di(Me)] > C2 [2,6-di(Et)]. Again, as
shown in the catalytic systems with the cocatalyst Et2AlCl, the
obtained polyethylenes with cocatalyst MAO are also highly
branched, as reflected by the low Tm values measured.
3. CONCLUSION
The synthesis and characterization of a class of nickel-based
ethylene polymerization catalysts ligated by new bulky unsymme-
trical R-diimines are described. Despite the fact that there have
been many reported R-diimine systems in the literature, the
unsymmetrical R-diimine presented herein represents a new
research avenue for R-diimine catalytic systems. On treatment
with the cocatalysts Et2AlCl and MAO, these complexes afforded
outstanding catalytic activity in the range of 107 g of PE (mol of
Ni)ꢀ1 hꢀ1, and the polyethylenes obtained exhibited a highdegree
of branching. Thus, the homopolymerization of ethylene by the
current nickel procatalysts provided highly branched polyethy-
lenes; the degree of branching varies at different temperatures.
The use of the ligand systems described herein with other metals,
as well as the polymerization of other monomers, will be reported
separately.
4. EXPERIMENTAL SECTION
4.1. General Considerations. All manipulations of air- and/or
moisture-sensitive compounds were carried out under a nitrogen atmo-
sphere using standard Schlenk techniques. Toluene was refluxed over
sodium benzophenone and distilled under nitrogen prior to use. Methy-
laluminoxane (MAO, 1.46 M solution in toluene) and modified methy-
laluminoxane (MMAO, 1.93 M in heptane, 3A) were purchased from
Akzo Nobel Corp. Diethylaluminum chloride (AlEt2Cl, 0.79 M in
toluene) and ethylaluminum sesquichloride (EASC, 0.87 M in toluene)
was purchased from Acros Chemicals. High-purity ethylene was pur-
chased from Beijing Yansan Petrochemical Co. and used as received.
Other reagents were purchased from Aldrich, Acros, or local suppliers.
NMR spectra were recorded on a Bruker DMX 400 MHz instrument at
ambient temperature using TMS as an internal standard; δ values are
given in ppm and J values in Hz. IR spectra were recorded on a Perkin-
Elmer System 2000 FT-IR spectrometer. Elemental analysis was carried
out using a Flash EA 1112 microanalyzer. Molecular weights and
molecular weight distribution (MWD) of polyethylene were determined
by a PL-GPC220 at 150 °C, with 1,2,4-trichlorobenzene as the solvent.
Melting points of polyethylenes were measured from the second scan-
ning run on a Perkin-Elmer DSC-7 differential scanning calorimetry
In terms of the lifetime for both the C4/Et2AlCl and C4/MAO
systems, the ethylene polymerization was conducted over differ-
ent time periods, namely 5, 10, 20, 30, and 60 min (entries 3
and 14ꢀ17 in Table 2 and entries 3 and 13ꢀ16 in Table 3). When
the reaction time was increased from 5 to 30 min, the produc-
tion followed an exponential increase (see Figure S2 in the
Supporting Information), whereas on further prolonged reaction
time, a distinct decrease of output was observed, suggesting that
active species suffered from deactivation for reaction times over
30 min.
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(DSC) analyzer under a nitrogen atmosphere; in the procedure, a sample
of about 2.0ꢀ6.0 mg was heated to 160 °C at a rate of 10 °C/min and
kept for 5 min at 160 °C to remove the thermal history and then cooled at
a rate of 10 °C/min to 20 °C. 13C NMRspectra of the polyethylenes were
recorded ona Bruker DMX-300 MHz instrument at 135 °C in deuterated
1,2-dichlorobenzene with TMS as an internal standard.
4.2.2.3. 2,6-Dibenzhydryl-N-(2-(2,6-diisopropylphenylimino)acenaph-
thylenylidene)-4-methylbenzenamine (L3). Using the same procedure
as for the synthesis of L1, L3 was obtained as a yellow powder in 33.7%
yield (0.34 g). Mp: 228ꢀ229 °C. IR (KBr; cmꢀ1): 3025.6 (w), 2958.4
(m), 1737.6 (s), 1650.8 (m), 1592.4 (s), 1493.0 (s), 1442.5 (s), 1238.8
(vs), 1039.0 (s), 927.1 (m), 829.6 (m), 764.1 (s), 744.1 (s). Anal. Calcd
for C57H50N2 (763.02): C, 89.72; H, 6.60; N, 3.67. Found: C, 89.33; H,
6.80; N, 3.44. 1H NMR (400 MHz, CDCl3, TMS): δ 7.67 (d, J = 8.22,
1H), 7.51 (d, J = 8.25, 1H), 7.29ꢀ7.24 (m, 7H), 7.22ꢀ7.17 (m, 3H),
7.12 (d, J = 7.45, 4H), 6.94ꢀ6.88 (m, 5H), 6.81 (s, 2H), 6.57 (t, J = 7.40,
4H), 6.45ꢀ6.37 (m, 3H), 5.93 (d, J = 7.10, 1H), 5.65 (s, 2H), 3.18 (m,
2H), 2.28 (s, 3H), 1.29 (d, J = 7.05, 6H), 1.02 (d, J = 6.78, 6H). 13C
NMR (100 MHz, CDCl3, TMS): δ 163.78, 162.22, 147.28, 147.01,
143.77, 141.85, 140.13, 135.86, 132.75, 132.44, 129.90, 129.72, 129.02,
128.72, 128.18, 127.91, 127.16, 129.79, 126.17, 125.61, 124.61, 124.46,
123.70, 123.01, 52.27, 28.63, 24.39, 23.87, 21.67.
4.2.2.4. 2,6-Dibenzhydryl-N-(2-(2,4,6-trimethylphenylimino)acenaph-
thylenylidene)-4-methylbenzenamine (L4). Using the same procedure
as for the synthesis of L1, L4 was obtained as a yellow powder in 29.7%
yield (0.22 g). Mp: 231ꢀ232 °C. IR (KBr; cmꢀ1): 3025.9 (w), 2914.7
(m), 1737.3 (s), 1664.7 (m), 1594.4 (m), 1493.2 (s), 1441.4 (s), 1235.2
(vs), 1036.8 (s), 918.6 (m), 837.0 (m), 765.8 (s), 738.8 (s). Anal. Calcd
for C54H44N2 (720.94): C, 89.96; H, 6.15; N, 3.89. Found: C, 89.55; H,
5.98; N, 4.11. 1H NMR (400 MHz, CDCl3, TMS): δ 7.71 (d, J = 8.22,
1H), 7.57 (d, J = 8.20, 1H), 7.29ꢀ7.22 (m, 5H), 7.19ꢀ7.15 (m, 2H),
7.11 (d, J = 7.46, 4H), 6.99 (m, 3H), 6.93 (d, J = 7.55, 4H), 6.79 (s, 2H),
6.60 (m, 5H), 6.42 (t, J = 7.22, 2H), 6.10 (d, J = 7.13, 1H), 5.61 (s, 2H),
2.38 (s, 3H), 2.27 (s, 3H), 2.17 (s, 6H). 13C NMR (100 MHz, CDCl3,
TMS): δ 163.58, 161.63, 146.88, 143.38, 142.01, 140.02, 132.96, 132.64,
132.35, 129.95, 129.67, 129.11, 128.84, 128.63, 128.21, 128.05, 127.79,
127.54, 126.92, 126.16, 125.50, 124.67, 124.23, 121.81, 52.33, 21.65,
21.05, 18.17.
4.2.2.5. 2,6-Dibenzhydryl-N-(2-(2,6-diethyl-4-methylphenylimino)
acenaphthylenylidene)-4-methylbenzenamine (L5). Using the same
procedure as for the synthesis of L1, L5 was obtained as a yellow powder
in 30.4% yield (0.41 g). Mp: 218ꢀ219 °C. IR (KBr; cmꢀ1): 3024.2 (w),
2912.9 (w), 1738.3 (m), 1660.2 (m), 1594.5 (m), 1493.84 (s), 1442.0
(vs), 1234.9 (vs), 1035.6 (s), 917.9 (m), 834.1 (m), 767.2 (s), 740.9 (s).
Anal. Calcd for C56H48N2 (748.99): C, 89.80; H, 6.46; N, 3.74. Found:
C, 89.67; H, 6.33; N, 3.92. 1H NMR (400 MHz, CDCl3, TMS): δ 7.69
(d, J = 8.25, 1H), 7.53 (d, J = 8.28, 1H), 7.26ꢀ7.33 (m, 5H), 7.17 (m,
2H), 7.11 (d, J = 7.56, 4H), 7.02 (s, 2H), 6.93 (m, 5H), 6.80 (s, 2H), 6.58
(t, 5H), 6.40 (t, J = 7.35, 2H), 6.01 (d, J = 7.16, 1H), 5.62 (s, 2H), 2.64
(m, 2H), 2.49 (m, 2H), 2.43 (s, 3H), 2.27 (s, 3H), 1.15 (t, J = 7.52, 6H).
13C NMR (100 MHz, CDCl3, TMS): δ 163.70, 161.96, 147.00, 145.96,
143.64, 141.95, 140.06, 133.30, 132.66, 132.39, 130.63, 129.93, 129.71,
128.95, 128.57, 128.19, 127.85, 127.30, 127.04, 126.96, 126.18, 125.56,
124.33, 122.41, 52.31, 24.57, 21.67, 21.39, 14.65.
4.2. Syntheses and Characterization. 4.2.1. 2-(2,6-Dibenzhy-
dryl-4-methylphenylimino)acenaphthylenone. A mixture of 2,6-diphe-
nylmethyl-4-methylaniline (1.45 g, 3.3 mmol), acenaphthylene-1,2-
dione (0.60 g, 3.3 mmol), and a catalytic amount of p-toluenesulfonic
acid in toluene (80 mL) was refluxed for 6 h. After solvent evaporation at
reduced pressure, the crude product was purified by column chroma-
tography on silica with the eluent petroleum ether/dichloromethane (2/
1 v/v) to afford 0.35 g of the red solid of the product in 17.6% isolated
yield. Mp: 222ꢀ223 °C. IR (KBr; cmꢀ1): 3025.9 (w), 1722.6 (s), 1649.9
(m), 1595.3 (s), 1491.5 (s), 1446.6 (s), 1274.4 (m), 1071.2 (m), 1026.4
(s), 908.5 (m), 829.2 (m), 776.9 (s), 743.4 (s), 694.7 (vs). Anal. Calcd
for C45H33NO (603.75): C, 89.52; H, 5.51; N, 2.32. Found; C, 89.22; H,
5.77; N, 1.99. 1H NMR (400 MHz, CDCl3, TMS): δ 8.029 (t, J = 6.56,
2H), 7.71 (m, 2H), 7.26ꢀ7.22 (m, 4H), 7.18 (d, J = 6.98, 2H), 7.05 (d,
5H), 6.86 (d, 4H), 6.79 (s, 2H), 6.60 (t, 4H), 6.43 (t, 2H), 6.14 (d, J =
7.08, 1H), 5.43 (s, 2H), 2.26 (s, 3H). 13C NMR (100 MHz, CDCl3,
TMS): δ 189.91, 162.50, 146.08, 143.11, 142.61, 141.91, 133.36, 131.94,
131.89, 129.83, 129.59, 128.84, 128.54, 128.29, 127.93, 127.13, 126.33,
125.64, 124.06, 121.67, 52.29, 21.67.
4.2.2. Synthesis of 2,6-Dibenzhydryl-N-(2-phenyliminoacenaphthy-
lenylidene)-4-methylbenzenamine (L1ꢀL5)
4.2.2.1. 2,6-Dibenzhydryl-N-(2-(2,6-dimethylphenylimino)acenaph-
thylenylidene)-4-methylbenzenamine (L1). A solution of 2-(2,6-dibenz-
hydryl-4-methylphenylimino)acenaphthylenone (0.34 g, 0.56 mmol), 2,6-
dimethylaniline (0.075 g, 0.62 mmol), and a catalytic amount of p-
toluenesulfonic acid in toluene (50 mL) was mixed and refluxed for 10
h. The solution was evaporated at reduced pressure. The residual solids
were further purified by silica column chromatography (8/1 petroleum
ether/ethyl acetate) to afford 0.15 g of L1 (yellow, 37.7% yield). Mp:
211ꢀ212 °C. IR (KBr; cmꢀ1): 3024.6 (w), 2915.6 (w), 1735.0 (m),
1664.5 (m), 1592.7 (m), 1493.8 (s), 1441.4 (s), 1233.3 (s), 1034.0 (s),
921.0 (m), 831.8 (m), 763.8 (vs), 739.8 (s). Anal. Calcd for C53H42N2
(706.91): C, 90.05; H, 5.99; N, 3.96. Found; C, 89.77; H, 5.68; N, 4.21. 1H
NMR (400 MHz, CDCl3, TMS): δ 7.72 (d, J = 8.20, 1H), 7.58 (d, J = 8.25,
1H), 7.26ꢀ7.23 (m, 5H), 7.17 (m, 4H), 7.12ꢀ7.06 (m, 5H), 6.99
(t, J = 7.80, 1H), 6.94 (d, J = 7.49, 4H), 6.79 (s, 2H), 6.60 (t, J = 7.38,
4H), 6.53 (d, J = 7.12, 1H), 6.42 (t, J = 7.33, 2H), 6.10 (d, J = 7.08, 1H),
5.30 (s, 2H), 2.27 (s, 3H), 2.21 (s, 6H). 13C NMR (100 MHz, CDCl3,
TMS): δ 163.58, 161.52, 149.46, 146.88, 143.43, 142.04, 140.09,
132.75, 132.38, 129.99, 129.71, 128.91, 128.81, 128.45, 128.26, 127.84,
127.60, 127.01, 126.22, 125.57, 124.96, 124.34, 123.82, 121.84, 52.40,
21.69, 18.29.
4.2.2.2. 2,6-Dibenzhydryl-N-(2-(2,6-diethylphenylimino)acenaph-
thylenylidene)-4-methylbenzenamine (L2). Using the same procedure
as for the synthesis of L1, L2 was obtained as a yellow powder in 32.8%
yield (0.43 g). Mp: 214ꢀ215 °C. IR (KBr; cmꢀ1): 3025.5 (w), 2928.4
(w), 1739.3 (m), 1672.5 (m), 1593.8 (m), 1494.0 (s), 1441.7 (vs),
1235.0 (vs), 1036.4(s), 920.6 (m), 831.0 (m), 762.1 (vs), 739.3 (s). Anal.
Calcd for C55H46N2 (734.97): C, 89.88; H, 6.31; N, 3.81. Found; C,
89.44; H, 6.17; N, 4.03. 1H NMR (400 MHz, CDCl3, TMS): δ 7.70 (d,
J = 8.20, 1H), 7.55 (d, J = 8.23, 1H), 7.28ꢀ7.17 (m, 10H), 7.13 (d, J =
7.36, 4H), 7.95 (d, J = 7.16, 5H), 6.82 (s, 2H), 6.60 (t, J = 7.31, 4H), 6.53
(d, J = 7.06, 1H), 6.42 (t, J = 7.22, 2H), 6.03 (d, J = 7.04, 1H), 5.66
(s, 2H), 2.70 (m, 2H), 5.54 (m, 2H), 2.29 (s, 3H), 1.18 (t, J = 7.47, 6H).
13C NMR (100 MHz, CDCl3, TMS): δ 163.65, 161.81, 148.52, 146.97,
143.65, 141.95, 140.10, 132.74, 132.38, 130.82, 129.94, 129.72, 128.99,
128.71, 128.22, 127.87, 127.34, 127.02, 126.27, 126.21, 125.60, 124.40,
124.18, 122.40, 52.34, 24.60, 21.69, 14.54.
4.2.3. Synthesis of the Tridentate Nickel Complexes C1ꢀC5. The
complexes C1ꢀC5 were synthesized by the reaction of (DME)NiBr2
with the corresponding ligands in dichloromethane. A typical synthetic
procedure for C1 is described as follows. The ligand L1 (0.146 g, 0.21
mmol) and (DME)NiBr2 (0.068 g, 0.22 mmol) were added to a Schlenk
tube together with 10 mL of dried dichloromethane. The reaction
mixture was then stirred for 8 h at room temperature, and absolute
diethyl ether (10 mL) was added to precipitate the complex. The
precipitate was washed with diethyl ether and dried under vacuum to
obtain a red powder of C1 in 83.3% (0.16 g) yield. IR (KBr; cmꢀ1):
3025.7 (w), 2964.3 (w), 1645.1 (w), 1601.3 (m), 1580.9 (s), 1494.2
(m), 1444.1 (s), 1292.9 (m), 1187.7 (w), 1082.2 (m), 1031.5 (m), 826.6
(m), 772.2 (vs), 747.8 (s). Anal. Calcd for C53H42Br2N2Ni (925.42): C,
68.79; H, 4.57; N, 3.03. Found: C, 68.40; H, 4.76; N, 3.31.
4.2.3.1. Data for C2. Yield: 86.8% (0.16 g), red powder. IR
(KBr; cmꢀ1): 3028.8 (w), 2967.9 (w), 1649.0 (w), 1629.6 (m), 1582.5
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Organometallics
ARTICLE
(s), 1492.7 (s), 1442.9 (s), 1287.9 (m), 1178.6 (m), 1075.5 (m), 1029.4
(m), 827.4 (m), 768.7 (vs), 744.4 (s). Anal. Calcd for C55H46Br2N2Ni
(953.47): C, 69.28; H, 4.86; N, 2.94. Found: C, 68.89; H, 4.59; N, 3.13.
4.2.3.2. Data for C3. Yield: 85.9% (0.091 g), red powder. IR
(KBr; cmꢀ1): 3024.0 (w), 2967.9 (m), 1646.0 (w), 1619.9 (m), 1581.6
(s), 1493.4 (s), 1444.3 (s), 1290.0 (m), 1179.9 (m), 1078.6 (w), 1036.9
(m), 828.8 (m), 769.9 (vs), 745.3 (s). Anal. Calcd for C57H50Br2N2Ni
(981.52): C, 69.75; H, 5.13; N, 2.85. Found: C, 69.57; H, 5.03; N, 3.22.
4.2.3.3. Data for C4. Yield: 82.4% (0.19 g), red powder. IR
(KBr; cmꢀ1): 3025.5 (w), 2973.0 (w), 1645.4 (w), 1602.1 (m), 1585.1
(s), 1493.6 (s), 1444.1 (s), 1294.1 (m), 1198.9 (w), 1074.9 (w), 1031.5
(m), 825.3 (m), 767.3 (vs), 742.9 (s). Anal. Calcd for C54H44Br2N2Ni
(939.44): C, 69.04; H, 4.72; N, 2.98. Found: C, 69.31; H, 4.51; N, 3.16.
4.2.3.4. Data for C5. Yield: 75.0% (0.15 g), red powder. IR
(KBr; cmꢀ1): 3022.7 (w), 2968.4 (w), 1652.3 (m), 1621.9 (s), 1583.3
(s), 1493.8 (s), 1445.0 (s), 1290.4 (m), 1182.4 (w), 1075.8 (w), 1030.8
(m), 829.1 (m), 770.0 (vs), 742.1 (s). Anal. Calcd for C56H48Br2N2Ni
(967.5): C, 69.52; H, 5.00; N, 2.90. Found: C, 69.18; H, 5.14; N, 3.10.
4.3. X-ray Crystallographic Studies. Single crystals of C4 and C5
suitable for X-ray diffraction analysis were obtained by laying diethyl ether
on the dichloromethane solution at room temperature. With graphite-
Brookhart, M. J. Am. Chem. Soc. 1996, 118, 11664. (c) Small, B. L.;
Brookhart, M.; Bennett, A. M. J. Am. Chem. Soc. 1998, 120, 4049.
(3) (a) Wang, C.; Friedrich, S.; Younkin, T. R.; Li, R. T.; Grubbs,
R. H.; Bansleben, D. A.; Day, M. W. Organometallics 1998, 17, 3149. (b)
Sun, W.-H.; Li, Z.; Hu, H.; Wu, B.; Yang, H.; Zhu, N.; Leng, X.; Wang, H.
New J. Chem. 2002, 26, 1474. (c) Speiser, F.; Braunstein, P.; Saussine, L.
Organometallics 2004, 23, 2625. (d) Hou, J.; Sun, W.-H.; Zhang, S.; Ma,
H.; Deng, Y.; Lu, X. Organometallics 2006, 25, 236. (e) Hao, P.; Zhang, S.;
Sun, W.-H.; Shi, Q. S.; Adewuyi, S.; Lu, X.; Li, P. Organometallics 2007,
26, 2439. (f) Wang, K.; Shen, M.; Sun, W. -H. Dalton Trans. 2009, 4085.
(4) (a) Sun, W.-H.; Zhang, S.; Jie, S.; Zhang, W.; Li, Y.; Ma, H.;
Chen, J.; Wedeking, K.; Fr€ohlich, R. J. Organomet. Chem. 2006,
691, 4196–4203. (b) Jie, S.; Zhang, S.; Sun, W.-H. Eur. J. Inorg. Chem.
2007, 35, 5584.
(5) Zhang, M.; Hao, P.; Zuo, W.; Jie, S.; Sun, W.-H. J. Organomet.
Chem. 2008, 693, 483.
(6) Zhang, M.; Gao, R.; Hao, X.; Sun, W.-H. J. Organomet. Chem.
2008, 693, 3867.
(7) (a) Sun, W.-H.; Hao, P.; Zhang, S.; Shi, Q.; Zuo, W.; Tang, X.; Lu,
X. Organometallics 2007, 26, 2720. (b) Chen, Y.; Hao, P.; Zuo, W.; Gao,
K.; Sun, W.-H. J. Organomet. Chem. 2008, 693, 1829. (c) Xiao, L.; Gao, R.;
Zhang, M.; Li, Y.; Cao, X.; Sun, W.-H. Organometallics 2009, 28, 2225.
(8) Gao, R.; Li, Y.; Wang, F.; Sun, W.-H.; Bochmann, M. Eur. J. Inorg.
Chem. 2009, 27, 4149.
(9) Sun, W.-H.; Hao, P.; Li, G.; Zhang, S.; Wang, W.; Yi, J.; Asma,
M.; Tang, N. J. Organomet. Chem. 2007, 692, 4506.
(10) Shao, C.; Sun, W.-H.; Li, Z.; Hu, Y.; Han, L. Catal. Commun.
2002, 3, 405.
ꢀ
monochromated Mo KR radiation (λ = 0.710 73 Å) at 173(2) K, cell
parameters were obtained by global refinement of the positions of all
collected reflections. Intensities were corrected for Lorentz and polariza-
tion effects and empirical absorption. Thestructures 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 refine-
ment were performed by using the SHELXL-97 package.24 Details of the
X-ray structure determinations and refinements are provided in Table S2
of the Supporting Information.
(11) Tang, X.; Sun, W.-H.; Gao, T.; Hou, J.; Chen, J.; Chen, W. J.
Organomet. Chem. 2005, 690, 1570.
(12) Zhang, C.; Sun, W.-H.; Wang, Z.-X. Eur. J. Inorg. Chem. 2006,
23, 4895.
(13) (a) Li, Z.; Sun, W.-H.; Ma, Z.; Hu, Y.; Shao, C. Chin. Chem. Lett.
2001, 12, 691. (b) Keim, W.; Killat, S.; Nobile, C. F.; Suranna, G. P.;
Englert, U.; Wang, R.; Mecking, S.; Schroder, D. L. J. Organomet. Chem.
2002, 662, 150. (c) Sun, W.-H.; Wang, K.; Wedeking, K.; Zhang, D.;
Zhang, S.; Cai, J.; Li, Y. Organometallics 2007, 26, 4781. (d) Liu, F.; Gao,
H.; Song, K.; Zhao, Y.; Long, J.; Zhang, L.; Zhu, F.; Wu, Q. Polyhedron
2009, 28, 673. (e) Zhang, S.; Sun, W.-H.; Xiao, T.; Hao, X. Organome-
tallics 2010, 29, 1168.
(14) (a) Song, D.-P.; Ye, W.-P.; Wang, Y.-X.; Liu, J.-Y.; Li, Y.-S.
Organometallics 2004, 28, 5697. (b) Zhang, M.; Zhang, S.; Hao, P.; Jie,
S.; Sun, W.-H.; Li, P.; Lu, X. Eur. J. Inorg. Chem. 2007, 3816. (c)
Schneider, Y.; Azoulay, J. D.; Coffin, R. C.; Bazan, G. C. J. Am. Chem. Soc.
2008, 130, 10464.
(15) (a) Deng, L.; Margl, P.; Ziegler, T. J. Am. Chem. Soc. 1997,
119, 1094. (b) Milano, G.; Guerra, G.; Pellecchia, C.; Cavallo, L.
Organometallics 2000, 19, 1343. (c) Leatherman, M. D.; Svejda, S. A.;
Johnson, L. K.; Brookhart, M. J. Am. Chem. Soc. 2003, 125, 3068. (d)
Milano, G.; Guerra, G.; Mazzeo, M.; Pellecchia, C.; Cavallo, L. Macro-
molecules 2005, 38, 2072. (e) Li, W.; Zhang, X.; Meetsma, A.; Hessen, B.
Organometallics 2008, 27, 2052. (f) Sgro, M. J.; Stephan, D. W. Dalton
Trans. 2010, 39, 5786–5794.
’ ASSOCIATED CONTENT
S
Supporting Information. Selected bond lengths and
b
angles (Table S1) and structure refinement details for C4 and
C5 (Table S2), the 13C NMR spectrum of polyethylene prepared
with catalyst C4/AlEt2Cl (entry 3 in Table 2, Figure S1), the
output of C4/Et2AlCl and C4/MAO systems over different
reaction times (Figure S2), figures giving all GPC curves regard-
ing the data of Tables 1 and 2, and CIF files giving X-ray crystal
structure data of nickel complexes C4 and C5. This material is
available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*C.R.: tel, þ44 (0)1603 593137; fax, þ44 (0)1603 592003;
e-mail, carl.redshaw@uea.ac.uk. W.-H.S.: tel, þ86-10-62557955;
fax, þ86-10-62618239; e-mail, whsun@iccas.ac.cn.
(16) (a) Gates, D. P.; Svejda, S. A.; Onate, E.; Killian, C. M.;
Johnson, L. K.; White, P. S.; Brookhart, M. Macromolecules 2000,
33, 2320. (b) Maldanis, R. J.; Wood, J. S.; Chandrasekaran, A.; Rausch,
M. D.; Chien, J. C. W. J. Organomet. Chem. 2002, 645, 158. (c) Zou, H.;
Zhu, F. M.; Wu, Q.; Ai, J. Y.; Lin, S. A. J. Polym. Sci., Part A: Polym. Chem.
2005, 43, 1325. (d) Bahuleyan, B. K.; Son, G. W.; Park, D.-W.; Ha, C.-S.;
Kim, I. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 1066. (e) Wegner,
M. M.; Ott, A. K.; Rieger, B. Macromolecules 2010, 43, 3624–3633. (f)
Song, C.-L.; Tang, L.-M.; Li, Y.-G.; Li, X.-F.; Chen, J.; Li, Y.-S. J. Polym.
Sci., Part A: Polym. Chem. 2006, 44, 1964. (g) Liu, H.-R.; Gomes, P. T.;
Costa, S. I.; Duarte, M. T.; Branquinho, R.; Fernandes, A. C.; Chien,
J. C. W.; Singh, R. P.; Marques, M. M. J. Organomet. Chem. 2005,
690, 1314. (h) Popeney, C. S.; Guan, Z. Macromolecules 2010, 43, 4091.
(i) Helld€orfer, M.; Backhus, J.; Milius, W.; Alt, H. G. J. Mol. Catal. A:
Chem. 2003, 193, 59.
’ ACKNOWLEDGMENT
This work was supported by MOST 863 program No.
2009AA033601. C.R. thanks the EPSRC for an overseas travel
grant (No. EP/H031855/1).
’ REFERENCES
(1) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. Rev. 2000,
100, 1169. (b) Mecking, S. Coord. Chem. Rev. 2000, 203, 325. (c)
Gibson, V. C.; Spitzmesser, S. K. Chem. Rev. 2003, 103, 283.
(2) (a) Johnson, L. K.; Killian, C. M.; Brookhart, M. J. Am. Chem. Soc.
1995, 117, 6414. (b) Killian, C. M.; Tempel, D. J.; Johnson, L. K.;
2423
dx.doi.org/10.1021/om200154a |Organometallics 2011, 30, 2418–2424

Organometallics
ARTICLE
(17) (a) Liu, F.-S.; Hu, H.-B.; Xu, Y.; Guo, L.-H.; Zai, S.-B.; Song,
K.-M.; Gao, H.-Y.; Zhang, L.; Zhu, F.-M.; Wu, Q. Macromolecules 2009,
42, 7789–7796.
(18) Leung, D. H.; Ziller, J. W.; Guan, Z. J. Am. Chem. Soc. 2008,
130, 7538.
(19) Li, L.; Jeon, M.; Kim, S. Y. J. Mol. Catal. A: Chem. 2009,
303, 110.
(20) (a) Killian, C. M.; Johnson, L. K.; Brookhart, M. Organome-
tallics 1997, 16, 2005. (b) Svefda, S. A.; Brookhart, M. Organometallics
1999, 18, 65.
(21) (a) Camacho, D. H.; Salo, E. V.; Ziller, J. W.; Guan, Z. Angew.
Chem., Int. Ed. 2004, 43, 1821. (b) Popeney, C. S.; Rheingold, A. L.;
Guan, Z. Organometallics 2009, 28, 4452. (c) Camacho, D. H.; Guan, Z.
Chem. Commun. 2010, 46, 7879–7893.
(22) Yu, J.; Hao, L.; Zhang, W.; Hao, X.; Sun, W.-H. Chem. Commun.
2011, 47, DOI: 10.1039/c0cc05373b.
(23) Galland, G. B.; Souza, R. F.; de.; Mauler, R. S.; Nunes, F. F.
Macromolecules 1999, 32, 1620.
(24) Sheldrick, G. M. SHELXTL-97, Program for the Refinement of
Crystal Structures; University of G€ottingen, G€ottingen, Germany, 1997.
2424
dx.doi.org/10.1021/om200154a |Organometallics 2011, 30, 2418–2424