2-Aldiminophenoxytitanium chloride complexes: Synthesis, characterization, and ethylene (co-)polymerization behavior

Article abstract of DOI:10.1016/j.jorganchem.2012.05.048

A series of trichlorotitanium 2-aldiminophenoxylate complexes (C1-C6) was synthesized by the stoichiometric reaction of TiCl₄(THF)₂ with the potassium salts of 6-alkyl-2-aldiminophenolates derived from ligands (L1-L6) bearing a bulky

Full text of DOI:10.1016/j.jorganchem.2012.05.048

Journal of Organometallic Chemistry 715 (2012) 119e128
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Journal of Organometallic Chemistry
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2-Aldiminophenoxytitanium chloride complexes: Synthesis, characterization,
and ethylene (co-)polymerization behavior
,
a
a,c,
Wenjuan Zhang a, Youhong Wang a, Carl Redshaw b , Xiang Hao , Wen-Hua Sun
*
**
a Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
b Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
c State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of trichlorotitanium 2-aldiminophenoxylate complexes (C1eC6) was synthesized by the
stoichiometric reaction of TiCl4(THF)2 with the potassium salts of 6-alkyl-2-aldiminophenolates derived
from ligands (L1eL6) bearing a bulky benzhydryl substituent, whereas the bis(2-aldiminophenoxy)
titanium dichloride (C7) was isolated in the reaction of a ligand L6 with 0.5 equivalents of TiCl4(THF)2. All
Received 25 February 2012
Received in revised form
23 May 2012
Accepted 31 May 2012
titanium complexes were characterized by 1H/13
C NMR spectroscopy and elemental analysis.
Single-crystal X-ray diffraction revealed distorted octahedron geometries around the titanium center for
complexes C2, C4 and C7. Upon activation with the co-catalyst MAO, all titanium pre-catalysts exhibited
good to high activities (up to 1.3 ꢀ 106 g mol (Ti)ꢁ1 hꢁ1) for ethylene polymerization at 70 ꢂC, producing
polyethylene products with high molecular weights. Furthermore, co-polymerization of ethylene with
Keywords:
Bulky 2-aldiminophenoxylate
Trichlorotitanium complexes
Ethylene polymerization
Ethylene co-polymerization
either a
-olefins or norbornene was achieved with activities in the range of 105 g mol (Ti)ꢁ1 hꢁ1 by these
titanium pre-catalysts along with good incorporation of co-monomer, typically 4.5 mol % for 1-hexene or
13.5 mol % for norbornene, respectively.
Crown Copyright Ó 2012 Published by Elsevier B.V. All rights reserved.
1. Introduction
possessed limited copolymerization ability compared with the PI
pre-catalysts, the latter possessing more open space around the
ZieglereNatta or metallocene-based systems are well estab-
lished as commercial catalysts in ethylene polymerization [1e7],
however early transition-metal complex pre-catalysts have
received attention as attractive alternatives due to their high
titanium center [31].
To enhance their co-polymerization behavior, mono-ligated
trichlorotitanium pre-catalysts have been explored (shown in
Scheme 1 and 2) [47e58]. The pre-catalyst I bearing a neutral
pendent phosphine donor, namely (LFI-PPh2)TiCl3 exhibited
considerable activity in ethylene polymerization (up to
1.41 kg polymer/(mmol (Ti) h bar)) and co-polymerization with 1-
hexene and NBE, providing high molecular weight (co)polymers
(Mw 104e105 g/mol) with narrow PDI (Mw/Mn ¼ 2e3). Presumably,
the five-coordinated complex pre-catalyst is less sterically
hindered, and consequently the co-monomer was more readily
taken up [47]. The pre-catalyst II exhibited appreciable activity
in both ethylene polymerization and co-polymerization
[48], whereas the pre-catalysts III that possessed a 1-methyl-2-
activity and controllability for a-olefin co-polymerization [8e10]
along with potentially producing precise polymers [11e15] and
advanced polymers [16e25]. The bis(iminophenoxy)titanium/
zirconium pre-catalysts, namely FI catalysts, have been widely
investigated in both ethylene polymerization and propylene syn-
diotactic polymerization [26e30]. Modification of these FI pre-
catalysts has focused on improving their thermal stability and co-
polymerization ability [31e38], with most examples focused on
bis-ligated titanium complexes [39e46]. However, bis-ligated FI
pre-catalysts were generally considered thermally unstable and
benzimidazolylmethyl
group,
produced
an
activity of
150 kg polymer/(mol (Ti) h bar) for ethylene polymerization only in
i
the presence of Bu3Al/DMAO, but produced polyethylenes with
* Corresponding author. Energy Materials Laboratory, School of Chemistry,
University of East Anglia, Norwich NR4 7TJ, UK. Tel.: þ44 1603 593137; fax: þ44
1603 592003.
** Corresponding author. Institute of Chemistry, Chinese Academy of Sciences,
Beijing 100190, China. Tel.: þ86 10 62557955; fax: þ86 10 62618239.
E-mail addresses: carl.redshaw@uea.ac.uk (C. Redshaw), whsun@iccas.ac.cn
(W.-H. Sun).
large PDI values (w48) [49]. The tridentate titanium complex pre-
catalyst IV exhibited a low activity for ethylene polymerization, and
with a broad distribution of polyethylene molecular weights [50].
However, the tridentate phenoxy-imine ligated titanium complex
pre-catalyst V was able to selectively trimerize ethylene in high
0022-328X/$ e see front matter Crown Copyright Ó 2012 Published by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.05.048

120
W. Zhang et al. / Journal of Organometallic Chemistry 715 (2012) 119e128
N
N
PPh2
N
Cl
Cl
N
Cl
Cl
Cl
Cl
Cl
Cl
N
N
Ti
Cl
N
N
Ti
O
N
O
Ti
Ti
R
O
O
Ti Cl
Cl
O
Cl
O
Cl
But
Cl
Cl
tBu
tBu
But
tBu
But
tBu
III
R2
IV
V
I
II
O
O
R1
Ph
R2
R4
O
R2
R4
N
R1
Cl
Cl
N
O
S R
Ti Cl
Cl
N
R3
R
X
N
Ti
R3
O
N
Ti Cl
Cl
Ti
Cl
O
Cl
Cl
Cl
Cl
R1
R2
Cl
VI
VII
IX
VIII
Scheme 1. Examples of mono-ligated trichlorotitanium pre-catalysts.
activity (up to 6.59 ꢀ 106 g/(g Ti h)) upon activation with MAO
[51e54]. The modified pre-catalysts VI [55] and VII [56] were found
to be capable of achieving high co-monomer incorporation during
ethylene co-polymerization, which was probably due to the
meridional arrangement of the ligands wrapped around the Ti
center. Furthermore, the tridentate phenoxy-imine titanium
complexes VIII [57], in which the carbonyl oxygen was bonded to
the titanium, were reported without polymerization data. Attrac-
tively, modified tridentate trichlorotitanium complexes of the type
IX exhibited good activity for both ethylene polymerization and co-
polymerization [58].
Clearly, these mono-ligated trichlorotitanium pre-catalysts have
not yet fulfilled the expected requirements of good catalytic activity,
better co-polymerization ability, and thermal stability. To create
more vacant space around the titanium center for improving the co-
polymerization ability, bi-dentate mono-ligated trichlorotitanium
complexes could be employed; a few examples of bi-dentate mono-
ligated trichlorotitanium pre-catalysts [59e62] were reported and
showed potential for considerable activity. Inspired by our recent
successful synthesis of late-transition metal pre-catalysts employing
ligands derived from benzhydryl-substituted anilines [63], we now
deploy a number of benzhydryl-substituted anilines to react with
salicylaldehydes to form corresponding bulky 2-aldiminophenolate
derivatives. Further reaction of the potassium salts of 2-
aldiminophenolates with titanium tetrachloride (THF complex)
afforded trichlorotitanium 2-aldiminophenolates (C1eC6), and also
an additional complex of bis(2-aldiminophenoxy)titanium dichlor-
ide (C7). When activated with methylaluminoxane (MAO), all tita-
nium pre-catalysts exhibited high activities for ethylene
polymerization at an optimized temperature at 70 ꢂC, affording high
molecular weight polyethylene products. Moreover, these titanium
pre-catalysts also showed good co-polymerization of ethylene with
either 1-hexene, or 1-octene, or norbornenes, illustrating a good
incorporation of norbornene (up to 13.5%) in the resultant co-
polymers. Herein, the synthesis and characterization of the tri-
chlorotitanium 2-aldiminophenoxylates (C1eC6) and bis(2-
aldiminophenoxy)titanium dichloride (C7) are reported, and their
ethylene (co-)polymerization behavior has been investigated.
R1
NH2
R5
CHO
R3
R1
Reflux
EtOH
R5
CH
OH
N
R2
+
R3
OH
R4
R2
R4
L1 - L6
2. Results and discussions
L6
Toluene
KH
Toluene
0.5 eq
KH
2.1. Synthesis and characterization of titanium complexes C1eC7
1.0 eq.
TiCl4(THF)2
Toluene
TiCl4(THF)2
Et
Toluene
The 2-((arylimino)methyl)phenol ligands (L1eL5) were
prepared by the condensation reaction of salicylaldehyde and
benzhydryl-substituted anilines as our previous procedure [48,64].
However, the reaction of 2-hydroxy-3-benzhydrylbenzaldehyde
with 2-benzhydrylanilines was not favorable, therefore the reac-
R1
R2
R5
CH
Cl
N
N
Ti
O
3
Cl
R
O
O
2
Et
Ph2HC
Cl
tion
diethylaniline was carried out to form the corresponding 2-(1-
(2,6-diethylphenylimino)methyl)-3-benzhydryl phenol (L6).
of
2-hydroxy-3-benzhydrylbenzaldehyde
with
2,6-
R4
Ti
C7
Cl
C1 - C6
Cl
R1
R2
R3
CHPh2
CHPh2
CHPh2
R4
R5
Treatment of the potassium salts of ligands (L1eL5) with either 0.5
or 1 equivalents of TiCl4(THF)2 afforded the same mono-ligated
trichlorotitanium complexes (LTiCl3(THF), C1eC5, Scheme 2) sug-
gesting that the bulky ligands formed from 2-benzhydrylanilines
prevented the formation of bis-ligated titanium complexes. In
contrast, the reaction of the potassium salt of L6 with 1 or 0.5
equivalents of TiCl4(THF)2 afforded two different complexes, viz the
mono-ligated L6TiCl3(THF) (C6) and the bis-ligated (L6)2TiCl2 (C7),
respectively (Scheme 2). The difference in the reactivity of the set of
tBu
tBu
tBu
tBu
tBu
CHPh2
tBu
Me
Me
Me
Me
Me
iPr
iPr
Me
CHPh2
CHPh2
CHPh2
Me
Me
Et
L1, C1
L2, C2
L3, C3
L4, C4
L5, C5
L6, C6
CHPh2 CHPh2
Me
H
CHPh2
Et
Scheme 2. Synthesis of ligands (L1eL6) and titanium complexes C1eC7.

W. Zhang et al. / Journal of Organometallic Chemistry 715 (2012) 119e128
121
ligands (L1eL5) and ligand L6 indicated the influence of ligands’
bulkiness (especially the location of the benzhydryl-substituent) on
the coordination at the titanium center. These highly sensitive
titanium complexes were fully characterized by 1H/13C NMR spec-
troscopy and by elemental analysis; complex C6 was more sensitive
than the analogs (C1eC5, C7). On comparing the 1H NMR spectra
with those of the corresponding ligands, the peak for the AreOH
(12.9e13.2 ppm) of the 2-(2-pyridinyliminomethyl)-phenols dis-
appeared in all the titanium complexes, indicating the formation of
the TieO bond. The peak for the CH]N (7.23e8.27 ppm) in the
ligands L1eL6 shifted to lower field (7.31e8.22 ppm) in the cor-
responding titanium complexes C1eC7, illustrating the formation
of a coordination bond between the Nimine and the Ti center. In the
13C NMR spectra, the CH]N resonances in the complexes appeared
at about 169e174 ppm and shifted downfield by 2.7e4.5 ppm
compared with those of the corresponding ligands.
The structures of the representative complexes C2, C4 and C7
were confirmed by the single crystal X-ray diffraction, and the
molecular structures are shown in Figs. 1e3, respectively. As is
shown in Fig.1, the titanium is coordinated with Ophenol, Nimine, OTHF
and three chlorides to give a distorted octahedron geometry, for
which the titanium is co-planar with the coordinated atoms of O1,
O2, N1 and Cl1; the other two chlorines (Cl2 and Cl3) are located in
trans-position with an angle Cl2eTi1eCl3 of 169.66(6)ꢂ. Within the
framework of ligands, the two phenyl groups on both sides of the
imine group are almost perpendicular, and the two chlorides Cl2
and Cl3 are located in trans-positions to each other, and the coor-
dinative sphere is completed by a THF molecule. The TieCl bond
lengths are consistent with those previously reported [65e70].
As seen in Fig. 2, the distorted octahedron geometry around the
Ti center in C2 is repeated in complex C4, though slight differences
are observed within the bond lengths TieO1, TieNimine (1.817(4),
2.288(4) Å) in C4 and (1.828(3), 2.185(4) Å) in C2. In contrast to C2,
the THF molecule in C4 is trans to a chloride (Cl3); the three chlo-
rides adopt a facial arrangement. Moreover, the two phenyl rings are
almost perpendicular in C4, similar to the situation observed for C2.
In Fig. 3, although complex C7 also possesses a distorted octa-
hedron geometry around the Ti center, because of the bis-ligated
nature of complex C7, much longer bond lengths are present, for
example TieO (1.864(3) and 1.884(3)). The ortho-benzhydryl at the
phenol (within L6) probably caused the weakening of the TieO
bond compared to those with an ortho-benzhydryl on the imino-
phenyl group (within L1eL5). This is also thought to be reason
why the mono-ligated titanium complex C6, having more space at
the metal, is more reactive than the other analogs C1eC5, and the
stable bis-ligated complex C7.
2.2. Catalytic behavior toward ethylene (co-)polymerization
2.2.1. Ethylene polymerization
Various alkylaluminium reagents were screened for their suit-
ability as co-catalysts in the catalytic system employing complex
C2. Poor results were observed when using the trialkylaluminium
reagents AlEt3, AlMe3 or AlEt2Cl. Interestingly, ethylene polymeri-
zation was observed with an activity as high as
1.12 ꢀ 105 g molꢁ1 (Ti) hꢁ1 when using methylaluminoxane (MAO)
as co-catalyst and 0.76 ꢀ 105 g molꢁ1 (Ti) hꢁ1 when using modified
methylaluminoxane (MMAO) under 10 atm ethylene with
3000:1 M ratio of Al/Ti at 50 ꢂC over 30 min. Considering the price
advantage of MAO over MMAO, subsequent investigations of
complex C2 were carried out by employing MAO as co-catalyst, and
the results are collected in Table 1.
2.2.1.1. Influence of the reaction parameters on the catalytic activi-
ties. Initially, the effect of temperature was investigated by
employing the C2/MAO system with a 3000 ratio of Al/Ti over
30 min. Upon elevating the temperature from 20 ꢂC to 50 ꢂC, the
catalytic activity gradually increased (runs 1e3, Table 1). When the
temperature rose above 50 ꢂC, the activity increased sharply and
the highest activity of 6.06 ꢀ 105 g molꢁ1 (Ti) hꢁ1 was achieved at
70 ꢂC, followed by a rapid decrease in activity on further increasing
the temperature until only trace polymer was observed at 90 ꢂC
(runs 4e7, Table 1), suggesting good thermal stability of the active
species. The FI titanium complex pre-catalysts demonstrated an
optimum activity of 3.8 ꢀ 106 g molꢁ1 (Ti) hꢁ1 at 50 ꢂC, but deac-
tivation occurred on elevating the temperature [29,30]. Its analogs
bearing the phenyl-substituent phenoxylimines showed a lower
activity of 4.40 ꢀ 105 g mol (Ti)ꢁ1 hꢁ1 barꢁ1 at 60 ꢂC (over 5 min at
1 bar) with a short lifetime. Other analogs bearing the iso-
propylbenzene imine exhibited
a
very low activity of
2 ꢀ 104 g mol (Ti)ꢁ1 hꢁ1 barꢁ1 at 60 ꢂC over 35 min [71e73]. The
current complex pre-catalysts showed reasonable thermal stability,
which is comparable to the commercial metallocene catalytic
system at around 75 ꢂC [5,6,74e76]. The reason is likely associated
with the bulkiness at the imine group, which plays a vital role in
stabilizing the active species at high temperature.
The effect of the Al/Ti molar ratio on the catalytic behavior was
also investigated. An increase of the Al/Ti molar ratio from 1000 to
4000 led to an increase of the activity for ethylene polymerization
from 1.98 ꢀ 105 g molꢁ1 (Ti) hꢁ1 to 12.26 ꢀ 105 g molꢁ1 (Ti) hꢁ1
(runs 8e12, Table 1). However, a further increase of the Al/Ti ratio
led to a dramatic decrease in catalytic activity and the amount of
resultant polyethylene (runs 12e14, Table 1); meanwhile the
molecular weights of the obtained polyethylenes decreased, which
is possible due to enhanced chain transfer to aluminum for the
termination [77,78]. Regarding the lifetime of the active species,
the effect of time on the activity was also evaluated. On prolonging
the reaction time, only a small decrease in the activity was
observed over 30 min (run 17 vs. run 12, Table 1) suggesting that
the active species could survive 30 min at this high temperature
(70 ꢂC).
Fig. 1. ORTEP drawing of C2 with thermal ellipsoids drawn at the 30% probability level.
Hydrogen atoms are omitted for clarity. Selected bond length (ꢂ) and selected bond
angles (Å): Ti(1)eO(1) 1.828(3), Ti(1)eO(2) 2.100(4), Ti(1)eN(1) 2.185(4), Ti(1)eCl(1)
2.3014(18), Ti(1)eCl(2) 2.3309(18), Ti(1)eCl(3) 2.3321(18), O(1)eTi(1)eO(2) 97.24(15),
O(1)eTi(1)eN(1) 82.85(15), O(2)eTi(1)eN(1) 176.15(15), O(1)eTi(1)eCl(1) 170.99(12),
O(2)eTi(1)eCl(1) 91.77(11), N(1)eTi(1)eCl(1) 88.18(11), O(1)eTi(1)eCl(2) 89.42(12),
O(2)eTi(1)eCl(2) 85.54(12), N(1)eTi(1)eCl(2) 98.31(12), Cl(1)eTi(1)eCl(2) 91.13(7),
O(1)eTi(1)eCl(3) 89.54(12), O(2)eTi(1)eCl(3) 84.39(12), N(1)eTi(1)eCl(3) 91.77(11),
Cl(1)eTi(1)eCl(3) 91.51(7), Cl(2)eTi(1)eCl(3) 169.66(6).

122
W. Zhang et al. / Journal of Organometallic Chemistry 715 (2012) 119e128
Fig. 2. ORTEP drawing of C4 with thermal ellipsoids drawn at the 30% probability level. Hydrogen atoms are omitted for clarity. Selected bond length (B) and selected bond angles
(Å): Ti(1)eO(1) 1.817(4), Ti(1)eO(2) 2.129(4), Ti(1)eN(1) 2.288(4), Ti(1)eCl(1) 2.2898(19), Ti(1)eCl(3) 2.296(2), Ti(1)eCl(2) 2.3057(19). O(1)eTi(1)eO(2) 87.48(16), O(1)eTi(1)eN(1)
79.96(16), O(2)eTi(1)eN(1) 84.25(16), O(1)eTi(1)eCl(1) 97.42(13), O(2)eTi(1)eCl(1) 86.80(12), N(1)eTi(1)eCl(1) 170.77(13), O(1)eTi(1)eCl(3) 92.23(13), O(2)eTi(1)eCl(3)
179.71(12), N(1)eTi(1)eCl(3) 95.67(12), Cl(1)eTi(1)eCl(3) 93.27(8), O(1)eTi(1)eCl(2) 164.25(13), O(2)eTi(1)eCl(2) 86.73(11), N(1)eTi(1)eCl(2) 84.89(12), Cl(1)eTi(1)eCl(2)
96.86(8), Cl(3)eTi(1)eCl(2) 93.55(7).
2.2.1.2. Effect of the ligand environment on the catalytic behavior. By
employing the optimized conditions of an Al/Ti molar ratio of
4000:1 at 70 ꢂC over 30 min, all titanium complexes were inves-
tigated for ethylene polymerization; and the results are collected in
Table 1. For the mono-ligated titanium complexes, catalytic activity
decreased in the order: C2 (R1, R3 ¼ CHPh2, R2 ¼ iPr, R4 ¼ tBu,
R5 ¼ Me) > C3 (R1, R3 ¼ CHPh2, R2 ¼ Me, R4 ¼ tBu, R5 ¼ Me) > C4 (R2,
R3 ¼ CHPh2, R1 ¼ Me, R4
¼
tBu, R5 ¼ Me) > C5 (R1, R2 ¼ Me,
R3 ¼ CHPh2, R4
¼
tBu, R5 ¼ Me) > C6 (R1, R3 ¼ Me, R2 ¼ H,
R4 ¼ CHPh2, R5 ¼ Me), suggesting that more sterically bulky
substituents on the benzene ring led to a more rigid environment
around titanium, thereby providing better protection at the higher
Table 1
Ethylene polymerization results by C1eC7/MAO systems.a
c
d
Run Cat. Al/Ti
T/ꢂC t/min Polymer (g) Activityb Mh
Tm (ꢂC)
1e
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C1
C3
C4
C5
C6
C7
3000 20
3000 40
3000 50
3000 60
3000 70
3000 80
3000 90
1000 70
2000 70
3000 70
3500 70
4000 70
4500 70
5000 70
4000 70
4000 70
4000 70
4000 70
4000 70
4000 70
4000 70
4000 70
4000 70
30
30
30
30
30
30
30
30
30
30
30
30
30
30
10
20
40
30
30
30
30
30
30
0.109
0.260
0.279
1.421
1.515
0.882
Trace
0.247
0.753
0.781
0.792
1.532
0.798
0.484
0.546
1.062
1.549
1.073
1.452
1.259
0.896
0.532
0.751
0.44
1.04
1.12
5.68
6.06
3.53
134.4
132.3
135.2
131.4
128.7
128.0
2e
2.1
3e
4e
2.2
4.0
n.s
5e
6e
7e
8f
1.98
6.03
6.24
6.34
12.26
6.38
131.7
130.5
15.9 133.5
9f
1.3
10f
11f
12f
13f
14f
15f
16f
17f
18f
19f
20f
21f
22f
23f
n.s
4.4
3.3
3.1
134.5
133.0
129.8
134.9
132.3
132.5
132.9
131.1
132.0
131.3
132.8
133.1
132.5
4.30
13.10
12.74
9.29
8.58
3.0
4.5
4.7
6.7
8.9
2.8
11.62
10.07
7.17
4.26
6.01
Fig. 3. ORTEP drawing of C7 with thermal ellipsoids drawn at the 30% probability level.
Hydrogen atoms are omitted for clarity. Selected bond length (ꢂ) and selected bond
angles (Å): Ti(1)eO(1) 1.864(3), Ti(1)eO(2) 1.884(3), Ti(1)eN(2) 2.212(4), Ti(1)eN(1)
2.222(4), Ti(1)eCl(2) 2.2933(16), Ti(1)eCl(1) 2.3458(16). O(1)eTi(1)eO(2) 87.27(15),
O(1)eTi(1)eN(2) 98.20(15), O(2)eTi(1)eN(2) 82.20(14), O(1)eTi(1)eN(1) 83.30(15),
O(2)eTi(1)eN(1) 101.67(15), N(2)eTi(1)eN(1) 175.94(15), O(1)eTi(1)eCl(2) 168.11(12),
O(2)eTi(1)eCl(2) 96.63(11), N(2)eTi(1)eCl(2) 93.47(11), N(1)eTi(1)eCl(2) 84.91(11),
O(1)eTi(1)eCl(1) 87.06(12), O(2)eTi(1)eCl(1) 165.17(11), N(2)eTi(1)eCl(1) 85.06(11),
N(1)eTi(1)eCl(1) 91.26(12), Cl(2)eTi(1)eCl(1) 91.68(6).
a
Conditions: MAO as co-catalyst, 10 atm ethylene, toluene, total volume 100 mL.
b
c
d
e
f
Activity: 105 g molꢁ1 hꢁ1
.
Determined by viscosity, 105 g molꢁ1
Determined by DSC.
.
5.0
25
m
mol cat.
m
mol cat.

W. Zhang et al. / Journal of Organometallic Chemistry 715 (2012) 119e128
123
temperatures (runs 12, 18e22). The current complex pre-catalysts
did not perform as well as the advanced FI pre-catalysts [26], but
the activity (4.26e11.62 ꢀ 105 g molꢁ1 (Ti) hꢁ1 at 70 ꢂC) was
generally considered better than those of analog titanium mono-
salicy(aldiminato) complexes [72,73]. It is noteworthy that the
sensitive complex C6 had to be used fresh, and immediately re-
crystallized prior to catalytic screening. However, the molecular
weight of the polymer produced by C6 was much higher than that
of C1eC5, suggesting that the larger distances between the
substituents on the ortho-position of the phenol and titanium
favored ethylene insertion and propagation. The bulky group at the
ortho-position of the aniline is more efficient at protecting the
active species than that at the ortho-position of the phenol for
ethylene polymerization at high temperature. As expected, the bis-
ligated titanium complex C7 showed much lower activity than did
the mono-ligated complexes C1eC5 (run 22 vs. runs 12, 18e21),
probably due to the crowded environment at the titanium center
in C7. However, the complex C7 showed higher activity than its
mono-ligated analog C6, which was quite unstable during the
catalysis.
Tm values of the ethylene/1-octene co-polymers produced by C1eC5,
and C7 were in the range 122.2e126.4 ꢂC (runs 2, 4e8, Table 2), lower
than those for the polyethylenes (131e135 ꢂC), which was consistent
with the incorporation of 1-octene. The 13C NMR (see Fig. 4) analysis
of the co-polymers (run 5, Table 2) revealed a 1-octene incorporation
rate of about 2.7 mol % [85].
2.2.3. Co-polymerization of ethylene/1-hexene
The co-polymerization behavior of ethylene with 1-hexene
using the catalysts herein was also investigated and the results
are collected in Table 3. The co-polymerization results for ethylene/
1-hexene (Table 3) were similar to those for ethylene/1-octene
(Table 2) and the catalysts exhibited moderate activity. The newly
purified complex C6 was screened, however, complex C6 exhibited
much lower activity for the co-polymerization of ethylene/1-
hexene than did C1eC5 at 70 ꢂC (run 1e7, Table 3); besides
stability, the steric bulk close to the TieO bond was thought to play
an important role, inhibiting the insertion of monomer and co-
monomer. The molecular weights of the resultant co-polymers
decreased in the order C4 > C3 > C2 > C1, which was the same
as the results observed for 1-octene. All the resultant co-polymers
also exhibited lower Tm values than did polyethylene, consistent
with incorporation of 1-hexene. In Fig. 5, the 13C NMR spectrum of
the ethylene/1-hexene co-polymer (run 8, Table 3) indicated the
resultant polymer contained a 4.5 mol % incorporation of 1-hexene
[85], which was higher than that observed for 1-octene.
2.2.2. Co-polymerization of ethylene/1-octene
The co-polymerization of ethylene with 1-octene by complexes
C1eC7 was also investigated with the Al/Ti molar ratio of 4000 at
70 ꢂC under 10 atm ethylene and the results are tabulated in Table 2.
The results showed that all catalysts exhibited moderate activities
toward ethylene/1-octene co-polymerization. Compared with the
results for ethylene homo-polymerization (Table 1), generally the
activities were lower; the reason is probably that the bulky envi-
ronment around the active species precludes the insertion of the
co-monomer.
Initially, the effect of the 1-octene concentration on the catalytic
behavior was investigated. An increase of 1-octene concentration
from 0.3 mol/Lto 1.0 mol/Lresultedin a slightlylower Tm value for the
resultant co-polymer (runs 1e3, Table 2), which is consistent with
previous results [50,57,79e84]. However, due to the low incorpora-
tion of 1-octene, there were no significant differences in Tm values of
the resultant copolymer. The highest activity for co-polymerization
by C2 was achieved with 1-octene at 0.5 M. The ligand environment
also had a big effect on the catalytic behavior and activities decreased
in the order: C2 > C3 > C4 > C1 > C5 > C7, which is the same as that
for the ethylene polymerization, suggesting that bulkier and stronger
donor substituents on the ortho-position of the arylimine are favor-
able for the stability of the active species at high temperature. The
order of the molecular weights of the polymers produced was
C4> C3> C2> C1, indicatingthat the bulkiersubstituentonthe ortho
position of the arylimine resulted in slower chain insertion and
propagation in the co-polymerization of ethylene with 1-octene. The
2.2.4. Co-polymerization of ethylene/norbornene
Co-polymers of ethylene with cyclo-olefins are known to be
amorphous materials with a promising combination of high
transparency in the UVeVis region along with humidity and heat-
resistance (called COC), all of which is attractive to industry
[86e88]. Herein, the catalysts were also tested for the co-
polymerization of ethylene with norbornene. As is shown in
Table 4, both the co-monomer concentration and the ligand envi-
ronment had a large effect on the catalytic activities. On increasing
the co-monomer concentration, the catalytic activities increased
initially and then decreased rapidly, which was consistent with
previous systems reported in the literature [84]; the best activity
was achieved at 1.8 mol/L concentration. The catalytic activities
decreased in the order: C2 > C3 > C4 > C5 > C1, suggesting that the
substituents on the imino-phenyl group had a strong influence on
the reactivity of their complexes. The bis-ligated complex C7
showed the lowest activity, with the highest Tm value of the
resultant co-polymer, and, as expected, also exhibited the lowest
incorporation of norbornene. The Mh produced by C5 was higher
than that observed for C1eC4, probably due to the smaller steric
Table 2
Co-polymerization of ethylene with 1-octene by C1eC5, C7/MAO.a
d
e
Run
Cat.
1-Octeneb
Polymer (g)
Activityc
Mh
Tm (ꢂC)
1
2
3
4
5
6
7
8
C2
C2
C2
C1
C3
C4
C5
C7
0.3
0.5
1.0
0.5
0.5
0.5
0.5
0.5
0.065
0.584
0.204
0.210
0.378
0.256
0.172
0.144
0.52
4.67
1.63
1.68
3.01
2.06
1.38
1.16
n.d
4.4
n.d
2.6
7.7
9.1
n.d
n.s
123.0
122.7
122.1
125.5
122.2
126.0
126.4
126.2
a
Conditions: 2.5
m
mol of cat., MAO, Al/Ti ¼ 4000, 70 ꢂC, 10 atm, 30 min, toluene,
total volume 100 mL, 30 min.
b
Mol Lꢁ1
.
c
d
e
Activity: 105 g molꢁ1 (Ti) hꢁ1
.
Determined by viscosity, 105 g molꢁ1
Determined by DSC.
.
Fig. 4. 13C NMR spectrum of ethylene/1-octene co-polymer.

124
W. Zhang et al. / Journal of Organometallic Chemistry 715 (2012) 119e128
Table 3
Table 4
Co-polymerization of ethylene with 1-hexene by C1eC7/MAO.a
Co-polymerization of ethylene with norbornene by C1eC5, C7/MAO.a
d
e
d
e
Run
Complex
1-Hexeneb
Polymer (g)
Activityc
Mh
Tm (ꢂC)
Run
Cat.
Norborneneb
Polymer(g)
Activityc
Mh
Tm (ꢂC)
1
2
3
4
5
6
7
8
C1
C2
C2
C3
C4
C5
C6
C7
0.5
0.5
1.0
0.5
0.5
0.5
0.5
0.5
0.283
0.641
0.285
0.434
0.403
0.189
0.151
0.187
2.27
5.16
2.28
3.47
3.22
1.52
1.21
1.50
1.2
4.0
125.5
125.2
124.7
125.0
124.8
124.6
124.1
123.6
1
2
3
4
5
6
7
8
9
C2
C2
C2
C2
C1
C3
C4
C5
C7
0.5
1.0
1.8
3.0
1.8
1.8
1.8
1.8
1.8
0.232
0.239
0.559
0.031
0.219
0.368
0.298
0.245
0.202
1.86
1.91
4.47
0.25
1.75
2.94
2.38
1.96
1.62
7.0
n.d
2.1
n.d
1.9
2.8
3.2
4.5
2.1
128.3
131.1
129.2
128.3
130.2
129.7
130.1
123.2
132.4
n.d
5.1
5.6
n.d
n.d
4.2
a
Conditions: 2.5
m
mol Ti, 10 atm, 70 ꢂC, 30 min, Al/Ti ¼ 4000, toluene, total
a
volume 100 mL.
Conditions: 2.5
m
mol of cat., MAO, 10 atm, 70 ꢂC, 30 min, Al/Ti ¼ 4000, toluene,
b
Mol Lꢁ1
.
total volume 100 mL.
c
d
e
b
Activity: 105 g molꢁ1 (Ti) hꢁ1
.
Mol Lꢁ1
.
Determined by viscosity, 105 g molꢁ1
Determined by DSC.
.
Activity: 105 g molꢁ1 (Ti) hꢁ1
.
c
d
e
Determined by viscosity, 105 g molꢁ1
Determined by DSC.
.
hindrance associated with C5, which favored the consecutive
coordination and insertion of ethylene or co-monomer. As seen
from the results, C7 produced the co-polymer with the lowest
molecular weight.
4. Experimental section
4.1. General procedure
In order to evaluate the incorporation rate of the norbornene,
the 13C NMR spectrum (Fig. 6) of the ethylene/norbornene co-
polymer (run 8, Table 4) was measured and the analysis indicated
that the resultant polymer possessed a 13.5 mol % incorporation of
norbornene [89e92].
All manipulations of air and/or moisture-sensitive compounds
were carried out under nitrogen atmosphere in a glove-box or
using standard Schlenk techniques. Methylaluminoxane (MAO,
1.46 M in toluene) was purchased from Albemarle. Potassium
hydride (KH) was washed with n-hexane before use to remove
contained mineral oil. Toluene, n-hexane and n-heptane were
refluxed in the presence of sodium and benzophenone, then freshly
distilled under nitrogen atmosphere before to use. Dichloro-
methane (CH2Cl2), 1-hexene and 1-octene were dried over calcium
hydride. Elemental analysis was performed on a Flash EA 1112
microanalyzer. 1H NMR and 13C NMR spectra were recorded on
a Bruker DMX 400 MHz instrument at ambient temperature using
TMS as an internal standard at 25 ꢂC. 13C NMR spectra of the
polymers was recorded on a Bruker DMX-300 MHz instrument at
110 ꢂC in deuterated 1,2-dichlorobenzene with TMS as an internal
standard. DSC trace and melting points of polyethylene were
obtained from the second scanning run on a PerkineElmer DSC-7 at
a heating rate of 10 ꢂC/min. In the trial of measuring the molecular
weights of obtained polymers by GPC, the GPC curves could be not
repeated, even for one same sample, with indicating portions of
ultra-high molecular weights. Therefore the molecular weights of
resultant polymers were measured by viscosity method. Viscosity
3. Conclusion
A series of 2-aldiminophenoxylate titanium complexes con-
taining the bulky CHPh2 group were prepared and fully character-
ized. When the eCHPh2 substituent was at the ortho-position of the
arylimine, the reaction of the potassium salt of the corresponding
ligands (L1eL5) with TiCl4(THF)2 at different ratios (2:1 or 1:1) gave
mono-ligated trichlorotitanium complexes [LTiCl3(THF)]. Whereas,
when this bulky group was located at the ortho-position of the
aryloxo moiety, the reaction afforded both the mono-ligated
complex C6 [L6TiCl3(THF)] and the bis-ligated complex C7
[(L6)2TiCl2]. In the presence of MAO, good activities were achieved
for ethylene homo-polymerization and co-polymerization of
ethylene with 1-hexene/1-octene/norbornene at 70 ꢂC, which was
much higher than the optimized temperature for FI catalysts
(50 ꢂC), and the incorporation rate for norbornene reached 13.5 mol
%. The bulky ligands enhanced the stability of their mono-ligated
titanium complexes, which provides an attractive strategy for
designing pre-catalysts for ethylene both homo-polymerization
and co-polymerization.
measurements [h
] were carried out in decalin at 130 ꢂC using an
Ubbelohde viscometer and molecular weight was calculated by the
1.37
Mh ¼ 5.37 ꢀ 104[
h
]
.
Fig. 5. 13C NMR spectrum of ethylene/1-hexene co-polymer.
Fig. 6. 13C NMR spectrum of ethylene/norbornene co-polymer.

W. Zhang et al. / Journal of Organometallic Chemistry 715 (2012) 119e128
125
4.2. Synthesis of ligand L1eL6
PheH), 6.61 (s, 1H, PheH), 6.55 (s, 1H, PheH), 5.52 (s, 1H,
CHPh2eH), 5.39 (s, 1H, CHPh2eH), 2.24 (s, 3H, CH3eH), 2.09 (s, 3H,
CH3eH), 1.45 (s, 9H, t-BueH). 13C NMR (CDCl3, 100 MHz, ppm):
168.4 (CH]N), 158.4, 146.6, 144.2, 143.5, 139.9, 137.4, 135.3, 131.5,
130.4, 130.0, 129.6, 129.4, 128.4, 128.3, 126.8, 126.3, 126.2, 118.2,
56.4, 52.3, 34.9, 29.5, 20.8, 18.8. IR (KBr, cmꢁ1): 3662 (OeH) (w),
3022, 2961, 2029, 1619 (CH]N) (s), 1592, 1440, 1388, 1319, 1263,
1204, 1163, 1128, 1076, 1028, 983, 863, 743, 696. Mp: 176 ꢂC. Anal.
Calcd. For C45H43NO: C, 88.05; H, 7.06; N, 2.28. Found: C, 88.25, H,
7.17; N, 2.16%.
4.2.1. 2-((2,6-Dibenzhydryl-4-isopropylphenylimino)methyl)-4,6-
di-tert-butylphenol (L1)
A mixture of 3,5-di-tert-butyl-2-hydroxybenzaldehyde (2.34 g,
10.0 mmol), 2,6-dibenzhydryl-4-isopropylbenzenamine (4.77 g,
10.0 mmol) and a catalytic amount of p-toluenesulfonic acid
(0.30 g) in 100 mL ethanol was refluxed for 12 h. The solution was
then cooled to room temperature, 2-((2,6-dibenzhydryl-4-
isopropylphenylimino)methyl)-4,6-di-tert-butylphenol (L1) was
obtained as a yellow solid (4.98 g, 72.8%). 1H NMR (CDCl3, 400 MHz,
ppm):
d
12.94 (s, 1H, OH), 7.33 (s, 1H, CH]N), 7.26e7.12 (m, 12H,
4.2.5. 2-((2-Benzhydryl-4,6-dimethylphenylimino)methyl)-6-tert-
butyl-4-methylphenol (L5)
Using the same procedure as for L1, 2-((2-benzhydryl-4,6-
dimethylphenylimino)methyl)-6-tert-butyl-4-methylphenol (L5)
was obtained as an orange/yellow solid in 62.5% yield (2.89 g). 1H
PheH), 7.03e7.01 (m, 8H, PheH), 6.89 (s, 1H, PheH), 6.71 (s, 2H,
PheH), 6.12 (d, 1H, J ¼ 2.04, PheH), 5.47 (s, 2H, CHPh2), 2.69 (m, 1H,
CH(CH3)2), 1.46 (s, 9H, t-BueH), 1.22 (s, 9H, t-BueH), 1.04 (d, 6H,
J ¼ 6.88, CH(CH3)2eH). 13C NMR (CDCl3, 100 MHz, ppm):
d 170.1
(CH]N), 158.0, 146.4, 144.4, 143.8, 139.8, 136.4, 135.0, 129.8, 128.3,
127.5, 127.2, 126.4, 126.2, 117.6, 52.6, 35.2, 34.1, 33.7, 31.6, 29.6, 24.1.
IR (KBr, cmꢁ1): 3661.2 (OeH) (w), 3059, 2956, 2164, 1629 (CN]N)
(m), 1593, 1443, 1359, 1251, 1163, 1118, 1027, 878, 845, 772, 737. Mp:
182 ꢂC. Anal. Calcd. For C50H53NO: C, 87.80; H, 7.81; N, 2.05. Found:
C, 87.98; H, 7.91; N, 2.11%.
NMR (CDCl3, 400 MHz, ppm): d 13.20 (s, 1H, OHeH), 7.70 (s, 1H,
CH]N), 7.26e7.15 (m, 7H, PheH), 7.09e7.04 (m, 4H, PheH), 6.97 (s,
1H, PheH), 6.62 (s, 1H, PheH), 6.56 (s, 1H, PheH), 5.55 (s, 1H,
CHPh2eH), 2.25 (s, 3H, CH3eH), 2.24 (s, 3H, CH3eH), 2.14 (s, 3H,
CH3eH), 1.46 (s, 9H, t-BueH). 13C NMR (CDCl3, 100 MHz, ppm):
d
168.4 (CH]N), 158.3, 146.0, 143.5, 137.3, 135.2, 133.8, 131.3, 130.3,
129.8, 129.7, 128.6, 128.3, 128.0, 126.7, 126.2, 118.2, 52.2, 34.8, 29.5,
21.1, 20.6, 18.5. IR (KBr, cmꢁ1): 3662 (OeH) (m), 3061, 2954, 2908,
2167, 1758, 1620 (CH]N) (s), 1581, 1476, 1431, 1389, 1358, 1320,
1262, 1234, 1199, 1158, 1132, 1031, 978, 860, 819, 775, 744, 697. Mp:
145 ꢂC. Anal. Calcd. For C33H35NO: C, 85.86; H, 7.64; N, 3.03. Found:
C, 85.92; H, 7.66; N, 2.96%.
4.2.2. 2-((2,6-Dibenzhydryl-4-isopropylphenylimino)methyl)-6-
tert-butyl-4-methylphenol (L2)
Using the same procedure as for L1, 2-((2,6-dibenzhydryl-4-
isopropylphenylimino)methyl)-6-tert-butyl-4-methylphenol (L2)
was obtained as an orange yellow solid in 63.9% yield (4.10 g). 1H
NMR (CDCl3, 400 MHz, ppm):
d 12.94 (s, 1H, OHeH), 7.23e7.12 (m,
14H, PheH), 7.04e7.02 (m, 8H, PheH), 6.73 (s, 2H, PheH), 6.08 (s,
1H, PheH), 5.49 (s, 2H, CHPh2eH), 2.71 (m, 1H, CH(CH3)2eH), 2.18
(s, 3H, PhCH3eH), 1.45 (s, 9H, t-BueH), 1.06 (d, 6H, J ¼ 6.88,
4.2.6. 2-((2,6-Diethylphenylimino)methyl)-6-benzhydryl-4-
methylphenol (L6)
Using the same procedure as for L1, 2-((2,6-diethylphenylimino)
methyl)-6-benzhydryl-4-methylphenol (L6) was obtained as an
orange/yellow solid in 63.2% yield (2.74 g). 1H NMR (CDCl3,
CH(CH3)2eH). 13C NMR (CDCl3, 100 MHz, ppm):
d 169.3 (CH]N),
158.3, 146.3, 144.5, 143.7, 137.0, 134.8, 131.3, 130.4, 129.8, 128.3,
126.5, 126.4, 126.3, 118.0, 52.5, 34.9, 33.7, 29.6, 24.1, 20.7. IR (KBr,
cmꢁ1): 3662 (OeH) (w), 3057, 3026, 2954, 2168, 1621 (CH]N) (w),
1592, 1432, 1388, 1266, 1207, 1157, 1127, 1029, 867, 772, 743, 699.
Mp: 178 ꢂC. Anal. Calcd. For C47H47NO: C, 87.94; H, 7.38; N, 2.18.
Found: C, 87.78; H, 7.46; N, 2.25%.
400 MHz, ppm):
d 13.09 (s, 1H, OH), 8.27 (s, 1H, CH]N), 7.32e7.29
(m, 1H, PheH), 7.25 (d, 3H, J ¼ 3.58, PheH), 7.22e7.19 (d, 4H,
J ¼ 3.58, PheH), 7.11e7.09 (m, 3H, PheH), 7.02 (d, 3H, J ¼ 1.23,
PheH), 6.86 (s, 1H, PheH), 6.07 (s, 1H, CHPh2eH), 2.51 (m, 4H,
CH2CH3eH), 2.23 (s, 3H, CH3eH), 1.13 (t, 6H, J ¼ 7.52, CH2CH3eH).
13C NMR (CDCl3, 100 MHz, ppm):
d 166.2 (CH]N), 156.3, 143.1,
4.2.3. 2-((2,6-Dibenzhydryl-4-methylphenylimino)methyl)-6-tert-
butyl-4-methylphenol (L3)
134.4, 133.9, 131.5, 130.2, 129.0, 127.8, 126.9, 125.9, 125.7, 124.7, 48.4,
24.3, 20.1, 14.4. IR (KBr, cmꢁ1): 3662 (OeH) (m), 2963, 2925, 2870,
1620 (CH]N) (s), 1583, 1494, 1447, 1261, 1185, 1158, 1077, 1030, 988,
865, 797, 728, 699. Mp: 176 ꢂC. Anal. Calcd. For C31H31NO: C, 85.87;
H, 7.21; N, 3.23. Found: C, 85.62; H, 7.35; N, 3.36%.
Using the same procedure as for L1, 2-((2,6-dibenzhydryl-4-
methylphenylimino)methyl)-6-tert-butyl-4-methylphenol
was obtained as an orange/yellow solid in 70.2% yield (4.31 g). 1H
NMR (CDCl3, 400 MHz, ppm): : 12.94 (s, 1H, OHeH), 7.29 (s, 1H,
(L3)
d
CH]NeH), 7.27e7.25 (m, 2H, PheH), 7.23e7.13 (m, 7H, PheH),
7.10e7.08 (m, 5H, PheH), 7.03e6.99 (m, 6H, PheH), 6.66 (s, 2H,
PheH), 6.38 (s,1H, PheH), 6.06 (s,1H, PheH), 5.47 (s, 2H, CHPh2eH),
4.3. Synthesis of trichlorotitanium 2-aldiminophenoxylates C1eC6
4.3.1. Trichlorotitanium 2-((2,6-dibenzhydryl-4-isopropylphenylimino)
methyl)-4,6-di-tert-butyl-phenoxylate THF adduct, L1TiCl3(THF) (C1)
2.17 (s, 3H, CH3eH), 2.16 (s, 3H, CH3eH), 1.44 (s, 9H, t-BueH). 13
C
NMR (CDCl3, 100 MHz, ppm):
d
169.4 (CH]N), 158.2, 146.1, 143.6,
To
a
stirred
solution
of
2-((2,6-dibenzhydryl-4-
142.9,137.0,135.0,131.3,130.4,129.8,128.3,126.7,126.4,126.3,118.0,
52.4, 34.8, 29.6, 21.5, 20.7. IR (KBr, cmꢁ1): 3662 (OeH) (w), 3026,
2960, 1619 (CH]N) (s), 1591, 1440, 1321, 1234, 1203, 1161, 1123,
1030, 983, 864, 743, 697. Mp: 156 ꢂC. Anal. Calcd. For C45H43NO: C,
88.05; H, 7.06; N, 2.28. Found: C, 88.22; H, 7.18; N, 2.23%.
isopropylphenylimino)methyl)-4,6-di-tert-butylphenol (L1) (0.684 g,
1.00 mmol) in dried toluene (30 mL), KH (0.040 g, 1.00 mmol) was
added at ꢁ78 ꢂC. The mixture was stirred for additional 3 h, then
TiCl4(THF)2 (0.334 g, 1.00 mmol) was added to the mixture solution
at ꢁ78 ꢂC, and the resultant mixture was allowed to warm to room
temperature and stirred for additional 24 h. The residue, obtained by
removing the solvent under vacuum, was extracted with CH2Cl2
(3 ꢀ 20 mL) and the combined filtrates were concentrated in vacuum
to 20 mL. The solution was recrystallized at ꢁ20 ꢂC to afford
brown crystals of trichlorotitanium 2-((2,6-dibenzhydryl-4-
4.2.4. 2-((2,4-Dibenzhydryl-6-methylphenylimino)methyl)-6-tert-
butyl-4-methylphenol (L4)
Using the same procedure as for L1, 2-((2,4-dibenzhydryl-6-
methylphenylimino)methyl)-6-tert-butyl-4-methylphenol
was obtained as an orange/yellow solid in 74.3% yield (4.56 g). 1H
NMR (CDCl3, 400 MHz, ppm): 13.14 (s, 1H, OHeH), 7.73 (s, 1H,
(L4)
isopropylphenylimino)methyl)-4,6-di-tert-butylphenoxylate
(C1)
d
(0.611 g, 67.2%). 1H NMR (CDCl3, 400 MHz, ppm): 7.58 (s, 1H, CH]N),
7.28e7.14 (m, 10H, PheH), 6.95e6.94 (m, 7H, PheH), 6.87e6.85 (m,
4H, PheH), 6.69 (s, 2H, PheH), 6.28 (s, 1H, PheH), 5.72 (s, 2H,
CH]N), 7.25e7.22 (d, 4H, J ¼ 7.47, PheH), 7.19e7.13 (m, 9H, PheH),
7.04 (d, 4H, J ¼ 7.24, PheH), 6.95 (d, 4H, J ¼ 6.51, PheH), 6.88 (s, 1H,

126
W. Zhang et al. / Journal of Organometallic Chemistry 715 (2012) 119e128
CHPh2eH), 4.52 (m, 4H, THF), 2.72 (m,1H, CH(CH3)2),1.93 (m, 4H, THF),
1.56 (s, 9H, t-BueH), 1.19 (s, 9H, t-BueH), 1.05 (d, 6H, J ¼ 6.88,
CH(CH3)2). 13C NMR (CDCl3, 100 MHz, ppm): 173.5 (CH]N), 160.6,
147.4, 145.5, 142.5, 136.4, 132.8, 129.9, 129.8, 128.4, 128.3, 126.8, 126.6,
126.5,123.8, 52.9, 35.3, 34.4, 33.7, 31.1, 30.0, 29.7, 25.4, 23.9. Anal. Calcd.
For C54H60Cl3NO2Ti: C, 71.33; H, 6.65; N, 1.54. Found: C, 71.42; H, 6.59;
N, 1.58%.
62.9%). 1H NMR (CDCl3, 400 MHz, ppm): 7.34 (s, 1H, CH]N),
7.24e7.00 (m, 10H, PheH), 6.96e6.94 (m, 4H, PheH), 5.79 (s, 1H,
CHPh2eH), 4.05 (m, 4H, THF), 2.24 (s, 6H, CH3eH), 2.11 (s, 3H,
CH3eH), 1.90 (m, 4H, THF), 1.52 (s, 9H, t-BueH). 13C NMR (CDCl3,
100 MHz, ppm): 171.8 (CH]N), 160.2, 143.2, 137.3, 136.8, 135.9,
135.5, 132.1, 129.9, 129.8, 129.3, 129.0, 128.4, 128.2, 128.1, 126.3,
125.3, 52.0, 34.9, 29.6, 25.2, 21.2, 20.7, 18.7, 18.0. Anal. Calcd. For
C37H42Cl3NO2Ti: C, 64.69; H, 6.16; N, 2.04. Found: C, 64.83; H, 6.24;
N, 2.11%.
4.3.2. Trichlorotitanium 2-((2,6-dibenzhydryl-4-isopropylphenylimino)
methyl)-6-tert-butyl-4-methyl-phenoxylate THF adduct, L2TiCl3(THF)
(C2)
4.3.6. Trichlorotitanium 2-((2,6-diethylphenylimino)methyl)-6-
benzhydryl-4-methylphenoxylate THF adduct, L6TiCl3(THF) (C6)
To a 30 mL toluene solution of 2-((2,6-diethylphenylimino)
methyl)-6-benzhydryl-4-methylphenol (1.00 mmol of L6), (0.040 g,
1.00 mmol) KH was added at ꢁ20 ꢂC. The mixture was stirred for
additional 4 h, then 0.334 g (1.0 mmol) TiCl4(THF)2 was added
at ꢁ78 ꢂC, and the resultant mixture was slowly warmed up to
room temperature and stirred for additional 12 h. After solvent
evaporation, the residue was extracted with CH2Cl2 (3 ꢀ 20 mL),
and the filtrate was combined and concentrated to about 20 mL.
The concentrated solution was covered with n-heptane and left for
three days to obtain brown crystals of trichlorotitanium 2-((2,6-
diethylphenylimino)methyl)-6-benzhydryl-4-methylphenoxylate
(C6) (0.493 g, 73.3%). 1H NMR (CDCl3, 400 MHz, ppm): 8.22 (s, 1H,
CH]N), 7.29 (m, 4H, AreH), 7.24 (m, 7H, AreH), 7.16 (m, 4H, AreH),
6.12 (s, 1H, CHPh2eH), 3.86 (m, 4H, THFeO(CH2)2eH), 2.61 (s, 3H,
Using the same procedure as for C1, trichlorotitanium 2-((2,6-
dibenzhydryl-4-isopropylphenylimino)methyl)-6-tert-butyl-4-
methylphenoxylate (C2) was isolated as a red solid (0.683 g, 77.6%).
1H NMR (CDCl3, 400 MHz, ppm): 7.47 (s, 1H, CH]N), 7.29e7.19 (m,
9H, PheH), 6.98e6.66 (s, 14H, PheH), 6.15 (s, 1H, PheH), 6.05 (s, 2H,
CHPh2eH), 4.24 (m, 4H, THF), 2.71 (m, 1H, CHMe2), 2.14 (s, 3H,
CH3eH), 1.90 (m, 4H, THF), 1.51 (s, 9H, t-BueH), 1.04 (d, 6H, J ¼ 5.16,
CH(CH3)2eH), 13C NMR (CDCl3, 100 MHz, ppm): 172.7 (CH]N),
160.1, 146.9, 143.7, 143.5, 137.7, 136.0, 135.3, 133.5, 130.0, 129.9,
128.3, 128.1, 127.0, 126.3, 53.6, 51.2, 35.0, 33.6, 30.1, 25.6, 24.0, 20.7.
Anal. Calcd. For C51H54Cl3NO2Ti: C, 70.63; H, 6.28; N, 1.62. Found: C,
70.75; H, 6.33; N, 1.68%.
4.3.3. Trichlorotitanium 2-((2,6-dibenzhydryl-4-methylphenylimino)
methyl)-6-tert-butyl-4-methyl-phenoxylate THF adduct, L3TiCl3(THF)
(C3)
CH3eH),
2.22
(s,
4H,
CH2CH3eH),
1.84
(m,
4H,
Using the same procedure as for C1, trichlorotitanium 2-((2,6-
dibenzhydryl-4-methylphenylimino)methyl)-6-tert-butyl-4-
methylphenoxylate (C3) was isolated as a brown solid (0.538 g,
64.1%). 1H NMR (CDCl3, 400 MHz, ppm): 7.31 (s, 1H, CH]N),
7.30e7.16 (m, 7H, PheH), 7.05 (d, 4H, J ¼ 6.72, PheH), 7.00e6.94 (m,
4H, PheH), 6.88e6.87 (d, 4H, J ¼ 5.70, PheH), 6.65 (s, 2H, PheH),
6.56 (s, 1H, PheH), 6.19 (s, 1H, PheH), 6.07 (s, 1H, PheH), 5.94 (s,
2H, CHPh2eH), 4.50 (m, 4H, THF), 2.18 (s, 3H, CH3eH), 2.15 (s, 3H,
CH3eH), 2.02 (m, 4H, THF), 1.54 (s, 9H, t-BueH). 13C NMR (CDCl3,
100 MHz, ppm): 172.9 (CH]N), 160.5, 143.0, 140.4, 133.0, 130.4,
130.0, 129.8, 129.5, 129.2, 129.1, 128.4, 128.2, 127.7, 126.4, 51.4, 35.0,
30.0, 25.7, 21.7, 21.6, 20.8. Anal. Calcd. For C49H50Cl3NO2Ti: C, 70.13;
H, 6.01; N, 1.67; Found: C, 70.25; H, 5.92; N, 1.62%.
THFeO(CH2CH2)2eH), 1.03 (s, 6H, CH2CH3eH). 13C NMR (CDCl3,
100 MHz, ppm): 168.9 (CH]N), 158.8, 139.9, 135.7, 134.0, 130.4,
129.1, 129.0, 128.5, 128.0, 127.3, 126.2, 125.6, 122.6, 47.3, 25.5, 20.6,
15.5. Anal. Calcd. For C35H38Cl3NO2Ti: C, 63.80; H, 5.81; N, 2.13.
Found: C, 64.02; H, 5.95; N, 2.14%.
4.3.7. Bis(2-((2,6-diethylphenylimino)methyl)-6-benzhydryl-4-
methylphenoxy)titanium dichloride, (L6)2TiCl2 (C7)
To a 30 mL toluene solution of 2-((2,6-diethylphenylimino)
methyl)-6-benzhydryl-4-methylphenol (L6), 0.040 g (1.00 mmol)
KH was added at ꢁ20 ꢂC. The mixture was stirred for additional 4 h,
then 0.167 g (0.50 mmol) TiCl4(THF)2 was added at ꢁ78 ꢂC, and the
resultant mixture was slowly warmed up to room temperature and
stirred for additional 12 h. After solvent evaporation, the residue
was extracted with CH2Cl2 (3 ꢀ 20 mL), and the filtrate was
combined and concentrated into about 20 mL. The concentrated
solution was covered with n-heptane and kept for three days to
obtain brown crystals of bis(2-((2,6-diethylphenylimino)methyl)-
6-benzhydryl-4-methylphenoxy)titanium dichloride (C7) (0.642 g,
65.2%). 1H NMR (400 MHz, CDCl3, 25 ꢂC): 8.13 (s, 2H, CH]N),
7.14e6.90 (m, 30H; PheH), 5.91 (s, 2H, CHPh2eH), 2.78 (s, 6H; CH3),
2.24 (s, 8H; CH2CH3), 1.03 (s, 12H, CH2CH3). 13C NMR (100 MHz,
CDCl3, ppm): 169.2 (CH]N), 159.7, 139.7, 136.7, 133.9, 130.4, 129.3,
129.1, 128.3, 128.1, 127.1, 126.1, 125.4, 122.6, 47.7, 25.2, 20.8, 15.2.
Anal. Calcd. For C62H60Cl2N2O2Ti: C, 75.68; H, 6.15; N, 2.85. Found:
C, 75.80; H, 6.01; N, 2.72%.
4.3.4. Trichlorotitanium 2-((2,4-dibenzhydryl-6-methylphenylimino)
methyl)-6-tert-butyl-4-methyl-phenoxylate THF adduct, L4TiCl3(THF)
(C4)
Using the same procedure as for C1, trichlorotitanium 2-((2,4-
dibenzhydryl-6-methylphenylimino)methyl)-6-tert-butyl-4-
methylphenoxylate (C4) was isolated as a brown solid (0.621 g,
74.0%). 1H NMR (CDCl3, 400 MHz, ppm): 7.29 (s, 1H, CH]N),
7.28e7.17 (m, 6H, PheH), 7.12e7.10 (m, 4H, PheH), 7.07e7.01 (m,
8H, PheH), 6.89 (s, 1H, PheH), 6.84 (d, 2H, J ¼ 7.27, PheH), 6.59 (s,
1H, PheH), 6.19 (s, 2H, PheH), 5.41 (s, 1H, CHPh2eH), 5.30 (s, 1H,
CHPh2eH), 4.26 (m, 4H, THF), 2.27 (s, 3H, CH3eH), 2.12 (s, 3H,
CH3eH), 1.89 (m, 4H, THF), 1.55 (s, 9H, t-BueH). 13C NMR (CDCl3,
100 MHz, ppm): 171.4 (CH]N), 160.2, 143.9, 143.7, 143.6, 143.2,
142.0, 137.9, 136.7, 135.4, 133.5, 133.0, 129.6, 129.3, 129.1, 128.4,
128.3,127.9,126.3,126.0,125.3, 56.2, 50.9, 35.0, 30.1, 25.2, 21.5, 20.8,
19.0. Anal. Calcd. For C49H50Cl3NO2Ti: C, 70.13; H, 6.01; N, 1.67.
Found: C, 70.28; H, 6.13; N, 1.59%.
4.4. Procedure for ethylene polymerization and co-polymerization
A stainless steel autoclave (250 mL) equipped with a mechanical
stirrer and a temperature controller was heated in vacuum at
120 ꢂC and recharged with ethylene three times, then cooled to
room temperature under ethylene atmosphere. A toluene solution
of the titanium pre-catalyst (with co-monomer) was transferred
into the reactor. After the desired reaction temperature was
reached and the required amount of co-catalyst (with total 100 mL
volume maintained through adding toluene) was added, the
autoclave was immediately pressurized to 10 atm. The ethylene
4.3.5. Trichlorotitanium 2-((2-benzhydryl-4,6-dimethylphenylimino)
methyl)-6-tert-butyl-4-methyl-phenoxylate THF adduct, L5TiCl3(THF)
(C5)
Using the same procedure as for C1, trichlorotitanium 2-((2-
benzhydryl-4,6-dimethylphenylimino)methyl)-6-tert-butyl-4-
methylphenoxylate (C5) was isolated as a brown solid (0.432 g,

W. Zhang et al. / Journal of Organometallic Chemistry 715 (2012) 119e128
127
Table 5
Crystal refinement of C2, C4 and C7.
C2
C4
C7
Empirical formula
Formula weight
Crystal color
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C51H54Cl3NO2Ti
867.20
Red
173(2)
0.71073
Triclinic
P-1
10.857(2)
15.604(3)
15.689(3)
69.83(3)
80.60(3)
85.88(3)
2461.1(9)
2
1.170
C49H49Cl3NO2Ti
838.14
Red
173(2)
0.71073
Monoclinic
P2(1)/c
15.291(3)
14.971(3)
24.297(5)
90
105.34(3)
90
5363.8(19)
4
C62H60Cl2N2O2Ti
983.92
Red
293(2) K
0.71073 A
Monoclinic
P2
11.165(2)
22.239(4)
22.190(4)
90
93.08(3)
90
5501.6(19)
4
b (Å)
c (Å)
a
b
g
(ꢂ)
(ꢂ)
(ꢂ)
Volume (Å3)
Z
Dcalc(Mg mꢁ3
)
1.038
0.341
1.188
0.296
m
(mmꢁ1
)
0.374
F(000)
Crystal size (mm)
range (ꢂ)
912
1756
2072
0.29 ꢀ 0.20 ꢀ 0.12
1.39e25.37
ꢁ10 ꢃ h ꢃ 13
ꢁ18 ꢃ k ꢃ 18
ꢁ18 ꢃ k ꢃ 18
18,848
0.37 ꢀ 0.16 ꢀ 0.13
1.38e25.32
ꢁ18 ꢃ h ꢃ 18
ꢁ17 ꢃ k ꢃ 18
ꢁ27 ꢃ k ꢃ 29
36,971
0.51 ꢀ 0.39 ꢀ 0.35
1.30e25.35
ꢁ13 ꢃ h ꢃ 13
ꢁ24 ꢃ k ꢃ 26
ꢁ26 ꢃ k ꢃ 20
38,215
q
Limiting indices
No. of rflns collected
No. of unique rflns
Rint
8906
0.0552
9764
0.1017
10,067
0.0754
Completeness to
q
(%)
98.7%
1.096
99.8%
1.072
99.9%
1.193
Goodness-of-fit on F2
Final R indices [I > 2
s
](I)]
R1 ¼ 0.0921,wR2 ¼ 0.2436
R1 ¼ 0.1191,wR2 ¼ 0.2666
0.581, ꢁ0.648
R1 ¼ 0.1049,wR2 ¼ 0.2657
R1 ¼ 0.1484,wR2 ¼ 0.2925
0.579, ꢁ0.422
R1 ¼ 0.0990,wR2 ¼ 0.2529
R1 ¼ 0.1154,wR2 ¼ 0.2646
0.540, ꢁ0.730
R indices (all data)
Largest diff peak, hole (e Åꢁ3
)
pressure was kept constant during the reaction through feeding
ethylene. At the end of the reaction time, the polymerization
reaction was stopped and the autoclave was placed in a water-ice
bath for an hour when 10% HCl-acidic ethanol was added. The
solid polyolefin was washed with ethanol and water several times
and then dried in vacuum to constant weight.
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
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Acknowledgments
This work was supported by National Natural Science Foundation
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