Copolymerization of ethylene with functionalized olefins by [ONX] titanium complexes

Article abstract of DOI:10.1021/ma400283p

A series of titanium complexes bearing [ONX] tridentate ligands have been synthesized and characterized. The complexes containing sulfur or phosphine donors showed high activity in the copolymerization of ethylene with 9-decen-1-ol (up to 1.3 × 10⁸ g polymer (mol Ti) ^-1h^-1) with an incorporation ratio of up to 8.8 mol %. Moreover, they have also shown excellent capability for copolymerization of ethylene with AlBuⁱ₃ (or tert-butylchlorodimethylsilane) pretreated 4-penten-1-ol, ω-alkenoic acid, and ω-alkenoic ester, as well as unprotected tertiary amine.

Full text of DOI:10.1021/ma400283p

Note
pubs.acs.org/Macromolecules
Copolymerization of Ethylene with Functionalized Olefins by [ONX]
Titanium Complexes
Zhou Chen, Jun-Fang Li, Wen-Jie Tao, Xiu-Li Sun,* Xiao-Hong Yang, and Yong Tang*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, CAS, Shanghai, P. R. China
S
* Supporting Information
ABSTRACT: A series of titanium complexes bearing [ONX]
tridentate ligands have been synthesized and characterized. The
complexes containing sulfur or phosphine donors showed high
activity in the copolymerization of ethylene with 9-decen-1-ol
(up to 1.3 × 108 g polymer (mol Ti)−1 h−1) with an
incorporation ratio of up to 8.8 mol %. Moreover, they have
also shown excellent capability for copolymerization of ethylene
with AlBui3 (or tert-butylchlorodimethylsilane) pretreated 4-
penten-1-ol, ω-alkenoic acid, and ω-alkenoic ester, as well as unprotected tertiary amine.
mol %) incorporation ratio at an Al/Zr molar ratio of 12600.
Compared with the late-transition metal and zirconium
catalysts, the titanium catalysts proved to be poor for the
copolymerization of ethylene and polar alkenes. Marques7f et al.
reported [Cp*Si(Me)2N-t-Bu]TiCl2 (CGC) could copolymer-
ize ethylene with 5-hexen-1-ol with an activity of up to 5.1 ×
105 g polymer (mol Ti)−1 h−1 and exhibited a high sensitivity
toward the polar group. Recently, Fujita et al. reported that
titanium complexes bearing bis(phenoxyimine) ligands were
active catalysts for the copolymerization of ethylene with acetyl-
protected hex-5-en-1-ol with an activity of up to 5.15 × 105 g
polymer (mol Ti)−1 h−1 and 0.74 mol % incorporation ratio.
Even in the presence of an excess amount of hex-5-enyl acetate
to DMAO, these complexes can produce copolymers with an
activity of 1.5 × 104 g polymer (mol Ti)−1 h−1 and 3.20 mol %
comonomer content.8 Li and co-workers have documented that
bis(β-enaminoketonato)titanium catalysts copolymerized ethyl-
ene with trialkylaluminium protected 5-norbornene-2-methanol
in an activity of up to 2.5 × 106 g polymer (mol Ti)−1 h−1 and
5.3 mol % incorporation ratio.9 Very recently, we have reported
titanium complexes bearing tridentate ligands were robust and
highly active in the polymerization of ethylene,10 and
copolymerization of ethylene with α-olefin, ω-alkenol, or ω-
alkenoic acid.10,11 To further understand the structure−
reactivity relationship of the catalysts, we synthesized and
characterized a series of titanium complexes bearing [ONX]
tridentate ligands. Investigation on the behaviors of these
complexes in copolymerzization of ethylene with ω-alkenol, ω-
alkenoic acid, ω-alkenoic ester, and ω-alkenyltertiary amine
unveiled the highest activity of 1.3 × 108 g copolymer (mol
Ti)−1 h−1 could be achieved. In this paper, we wish to report
the results in detail.
INTRODUCTION
■
Functionalized polyolefins possess, to a large extent, the
original properties of the polyolefins as well as some unique
properties such as permeability, affinity for dyes, and
compatibility with more polar polymers. The synthesis of
polyolefins bearing functional groups along the chain backbone
has been attracting interest in past decades.1,2 The copoly-
merization of ethylene with polar alkenes provides an easy and
low-cost access to functionalized polyethylenes. Of the methods
documented, two strategies, including the use of late transition
metal catalysts and early transition metal catalysts by masking
the functional group of polar alkenes with Lewis acids such as
triethylaluminium, have been reported. Although many
catalysts have been developed, only a few catalysts exhibit
high activity to afford polymers with good contents of polar
comonomers.1,3−7 For instance, α-diimine palladium complexes
could copolymerize ethylene with polar monomers, such as
acrylates, methyl vinyl ketones, and silyl vinyl ethers to yield
highly branched copolymers.3 Nickel complexes bearing
salicylaldiminato ligands exhibited good tolerance to functional
group and promoted the copolymerization of ethylene with 5-
norbornene-1-ol with comonomer incorporation up to 22 wt
%.4 Neutral palladium phosphine−sulfonate complexes5 prove
to be remarkably efficient for the copolymerization of olefins
with polar acrylate and its derivatives, producing highly linear
copolymers with in-chain polar monomer incorporation.
Although early transition metal catalysts are known for their
intolerance to polar group due to their high oxophilicity,6 by
protecting the functional group with trialkylaluminium or in the
presence of a large amount of excess cocatalysts, zirconocene/
methylaluminoxane (MAO) catalysts offer a good way to
copolymerize ethylene and propylene with monomers contain-
ing functional groups.7 For example, Aaltonen7b et al. reported
ethylene and propylene were copolymerized with 10-undecen-
1-ol using stereorigid zirconocene catalysts with an activity of
up to 6.7 × 106 g polymer (mol Zr)−1 h−1 and 3.1 wt % (0.5
Received: February 6, 2013
Revised: March 15, 2013
Published: March 27, 2013
© 2013 American Chemical Society
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dx.doi.org/10.1021/ma400283p | Macromolecules 2013, 46, 2870−2875

Macromolecules
Note
Table 1. Synthesis of Ligands and Complexes
a
X
R1
C6H5
R2
C6H5
R3
CH3
yield (%)
3a, 4a
3b, 4b
3c, 4c
3d, 4d
3e, 4e
3f, 4f
S
O
P
N
S
S
S
S
S
S
S
S
S
90
76
76
84
98
60
77
82
92
92
91
86
86
C6H5
C6H5
CH3
C6H5
C6H5
(Ph)2
(CH2)4
n-Pr
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
i-Pr
3g, 4g
3h, 4h
3i, 4i
C6H5
C6H5
C6H5
Cyclohexyl
n-Pr
C6H5
C6H5
p-CH3C6H4
p-CF3C6H4
C6H5
p-CH3C6H4
C6H5
3j, 4j
n-Pr
3k, 4k
3l, 4l
p-CF3C6H4
C6H5
n-Pr
CF3
CH3
3m, 4m
CH3
C6H5
n-Pr
a
Isolated yield of 4.
[3-((2-(Diphenylphosphino)ethyl)imino)-1,3-diphenylprop-1-en-
EXPERIMENTAL SECTION
■
1-olate]TiCl3 (4c). A procedure similar to that described for 4a was
1
General Methods. All air or moisture sensitive manipulations
were carried out under nitrogen atmosphere using Schlenk techniques
or in a glovebox. 1H NMR, 13C NMR spectra were recorded on Varian
Mercury 300 spectrometer or Varian 400 NMR spectrometer. Mass
spectra were carried out with a HP5989A spectrometer. Elemental
analysis was performed by the Analytical Laboratory, Shanghai
Institute of Organic Chemistry. Mn, Mw, and Mw/Mn values of
polymers were determined with Agilent Technologies PL-GPC 220
High Temperature Chromatography at 150 °C (polystyrene
calibration, 1,2,4-trichlorobenzene as a solvent at a flow rate of 1.0
mL·min−1). 1H and 13C NMR data of polymers were obtained using o-
dichlorobenzene-d4 as a solvent at 110 °C. X-ray crystallographic data
was collected using a Bruker AXSD8 X-ray diffractometer. Toluene,
hexane, dichloromethane (DCM) and tetrahydrofuran (THF) were
purified by MB SPS-800 system. Modified methylaluminoxane
(MMAO-3A) was purchased from Akzo Chemical as a 1.88 M
heptane solution. The catalyst, rac-ethenebis(indenyl)zirconium
dichloride (rac-Et[Ind]2ZrCl2 (4n)) was purchased as powder from
Alfa-Aesar. Polymerization-grade ethylene was purified before use.
Complexes 4a, 4e, 4f, 4g, 4i, 4j and 4m were synthesized as described
previously.11 The new complexes were prepared as follows:
General Procedure for the Synthesis of Titanium Complexes
4. [3-((2-Methoxyethyl)imino)-1,3-diphenylprop-1-en-1-olate]TiCl3
(4b). To a suspension of potassium hydride (KH) (0.2 g, 5.3 mmol)
in dry THF (30 mL) was added a solution of 3b (1.0 g, 3.6 mmol) in
THF (10 mL) at −78 °C. The resulting suspension was warmed to
room temperature and stirred for 3 h. The solvent was removed under
reduced pressure and the residue was dissolved in dry DCM (20 mL).
It was then added dropwise into a solution of TiCl4 (1.0 g, 5.3 mmol)
in DCM (30 mL) at −78 °C. The solution was allowed to warm to
room temperature and stirred for 18 h. The solid was filtered off and
washed with DCM (10 mL). The solvent was removed under reduced
pressure and the residue was dissolved in a mixed solvent of dry
toluene (20 mL) and THF (10 mL), and then kept at −30 °C
overnight. The resulting reddish crystals were collected and dried
followed to yield 4c: 0.7 g (76%). H NMR (300 MHz, CDCl3): δ
7.88−7.81 (m, 6H, Ar−H), 7.52−7.29 (m, 14H, Ar−H), 6.35 (s, 1H,
CH), 4.19−4.07 (m, 2H, NCH2), 2.75−2.68 (m, 2H, PCH2). 13C
NMR (75 MHz, CDCl3): δ 170.6, 168.9, 138.3, 132.8, 132.7, 1332.5,
132.3, 132.1, 131.9, 131.6, 130.6, 129.5, 129.4, 129.2, 128.8, 128.7,
128.2, 127.5, 127.2, 125.8, 125.6, 109.0, 54.9 (d, J = 9.0 Hz), 24.8(d, J
= 22.1 Hz). 31P NMR (121.4 MHz, CDCl3): δ 17.16. Anal. Calcd for
C29H25Cl3NOPTi (587.02): C, 59.16; H, 4.28; N, 2.38. Found: C,
58.97; H, 4.27; N, 2.30.
[1,3-Diphenyl-3-((2-(pyrrolidin-1-yl)ethyl)imino)prop-1-en-1-
olate]TiCl3 (4d). A procedure similar to that described for 4b was
1
followed to yield 4d: 1.2 g (84%). H NMR (300 MHz, CDCl3): δ
7.81 (d, 2H, J = 7.5 Hz, Ar−H), 7.51−7.33 (m, 8H, Ar−H), 6.32 (s,
1H, CH), 4.23−4.17 (m, 2H, N(CH2CH2)2), 3.80 (t, 2H, J = 5.1
Hz, NCH2), 3.58−3.52 (m, 2H, N(CH2CH2)2), 2.97 (t, 2H, J = 5.1
Hz, NCH2), 2.14−2.10 (m, 2H, N(CH2CH2)2), 1.93−1.90 (m, 2H,
N(CH2CH2)2). 13C NMR (75 MHz, CDCl3): δ 170.2, 169.6, 136.8,
132.5, 131.9, 129.9, 129.2, 128.8, 127.1, 126.1, 108.9, 63.0, 57.1, 54.9,
22.1. Anal. Calcd for C21H23Cl3N2OTi (472.04): C, 53.25; H, 4.89; N,
5.91. Found: C, 53.30; H, 5.14; N, 5.74.
[3-((2-(Cyclohexylthio)ethyl)imino)-1,3-diphenylprop-1-en-1-
olate]TiCl3 (4h). A procedure similar to that described for 4b was
1
followed to yield 4h (1.1 g, 82%). H NMR (300 MHz, CDCl3): δ
7.83 (d, 2H, J = 6.6 Hz, Ar−H), 7.52−7.29 (m, 8H, Ar−H), 6.40 (s,
1H, CH), 4.04 (brs, 2H, NCH2), 3.55−3.48 (m, 1H, SCH), 3.10
(brs, 1H, SCH2), 2.92 (brs, 1H, SCH2), 2.77 (brs, 1H, Cy-H), 2.02−
1.37 (m, 9 H,Cy-H). 13C NMR (75 MHz, CDCl3): δ 170.6, 169.6,
137.6, 132.1, 132.0, 129.8, 129.3, 128.9, 127.2, 125.8, 109.5, 79.0, 57.5,
49.9, 33.4, 25.6(2), 25.5(6). Anal. Calcd for C23H26Cl3NOSTi
(517.03): C, 53.25; H, 5.05; N, 2.70. Found: C, 52.89; H, 4.96; N,
2.53.
[3-Phenyl-3-((2-(propylthio)ethyl)imino)-1-(4-(trifluoromethyl)-
phenyl)prop-1-en-1-olate]TiCl3 (4k). To a stirred solution of TiCl4
(1.5 g, 8.0 mmol) in dry toluene (50 mL) at −78 °C was added
dropwise a solution of 3k (2.0 g, 6.1 mmol) in dry toluene (10 mL)
over 20 min. The solution was allowed to warm to room temperature
and stirred for 16 h. The solvent was removed under reduced pressure
and the residue was dissolved in dry toluene (100 mL). The solution
was concentrated under reduced pressure to about 20 mL and kept at
−30 °C overnight. Dark red crystals were collected and dried under
1
under reduced pressure to give complex 4b: 1.2 g (76%). H NMR
(300 MHz, CDCl3): δ 7.86−7.83 (m, 2H, Ar−H), 7.54−7.31 (m, 8H,
Ar−H), 6.42 (s, 1H, CH), 4.40 (s, 3H, OCH3), 4.14 (t, 2H, J = 5.4
Hz, OCH2), 3.93 (t, 2H, J = 5.4 Hz, NCH2). 13C NMR (100 MHz,
CDCl3): δ 170.6, 170.1, 136.3, 132.2, 131.7, 130.3, 129.3, 129.0, 127.2,
126.1, 109.5, 76.0, 68.1, 53.7. Anal. Calcd for C18H18Cl3NO2Ti
(432.99): C, 49.75; H, 4.17; N, 3.22. Found: C, 49.98; H, 4.44; N,
2.87.
1
reduced pressure to yield complex 4k (0.61 g, 91%). H NMR (300
MHz, CDCl3): δ 7.93 (d, 2H, J = 8.1 Hz, Ar−H), 7.67 (d, 2H, J = 8.4
Hz, Ar−H), 7.54−7.52 (m, 3H, Ar−H), 7.32−7.30 (m, 2H, Ar−H),
2871
dx.doi.org/10.1021/ma400283p | Macromolecules 2013, 46, 2870−2875

Macromolecules
Note
6.43 (s, 1H, CH), 4.20−4.03 (m, 2H, NCH2), 3.49−3.40 (m, 1H,
SCH2), 3.26−3.19 (m, 1H, SCH2), 3.01−2.92(m, 1H, SCH2), 2.77−
2.73 (m, 1H, SCH2), 2.00−1.87 (m, 2H, CH2CH2CH3),1.14 (t, 3H, J
= 7.2 Hz, CH2CH2CH3). 13C NMR (100 MHz, CDCl3): δ 170.6,
167.6, 137.3, 135.6, 133.1 (q, J = 32.7 Hz), 130.0, 129.5, 127.4, 125.9
(q, J = 3.3 Hz), 123.6 (q, J = 270.6 Hz), 57.4, 41.7, 36.4, 21.8, 13.5. 19F
NMR (376 MHz, CDCl3):
C21H21Cl3F3NOSTi (544.98): C, 46.14; H, 3.87; N, 2.56. Found: C,
δ −63.03. Anal. Calcd for
45.92; H, 4.22; N, 2.42.
[4,4,4-Trifluoro-3-((2-(methylthio)ethyl)imino)-1-phenylbut-1-en-
1-olate]TiCl3 (4l). A procedure similar to that described for 4b was
followed to yield 4l (1.3 g, 86%). 1H NMR (300 MHz, CDCl3): δ 7.91
(d, 2H, J = 7.8 Hz, Ar−H), 7.61−7.47 (m, 3H, Ar−H), 6.76 (s, 1H, 
CH), 4.44 (brs, 2H, NCH2), 3.45−3.36 (m, 1H, SCH2), 2.93−2.86
(m, 1H,SCH2), 2.83 (s, 3H, SCH3). 13C NMR (75 MHz, CDCl3): δ
175.1, 156.4 (q, J = 28.9 Hz), 133.2, 131.8, 129.2, 127.6, 118.7(q, J =
285.3 Hz), 100.8 (q, J = 4.5 Hz), 55.6, 38.2, 22.8. 13F NMR (282 MHz,
CDCl3): δ −63.33. Anal. Calcd for C13H13Cl3F3NOSTi (440.92): C,
35.28; H, 2.96; N, 3.17. Found: C, 35.26; H, 3.09; N, 3.08.
General Procedure for Pretreating Comonomers with
AlBui3. To a solution of comonomer (0.1 mol) in toluene (30 mL)
was added AlBui3 (0.12 mol for ω-alkenol, 0.22 mol for ω-alkenoic
acid and ester) at −20 °C. The resulting mixture was allowed to warm
to room temperature and the solution was stirred for 24 h. Toluene
was added until the total volume of the solution was 100 mL for
further use.
General Procedure of Copolymerization of Ethylene and
Polar Monomers. A desired amount of toluene was transferred into a
flask and saturated with ethylene at polymerization temperature.
Modified-methylaluminoxane (MMAO) and comonomer were
syringed into the flask in sequence, and the mixture was stirred for
10 min. The polymerization was started by adding a solution of 4 in
DCM. After the desired time, the copolymerization was quenched with
acidified ethanol and poured into a large amount of acidified ethanol
(300 mL, 10% HCl (v/v) in ethanol). The precipitated copolymer was
collected, washed with ethanol, and then dried at 60 °C under reduced
pressure until a constant weight.
Figure 1. Molecular Structure of Complex 4h (H atoms are omitted
for clarity). Selected bond lengths(Å) and angles (deg): Ti(1)−O(1)
= 1.836(1), Ti(1)−N(1) = 2.153(1), Ti(1)−Cl(3) = 2.277(1), Ti(1)−
Cl(1) = 2.285(1), Ti(1)−Cl(2) = 2.327(1), Ti(1)−S(1) = 2.617(1);
O(1)−Ti(1)−N(1) = 84.36(5), O(1)−Ti(1)−Cl(3) = 103.38(4),
N(1)−Ti(1)−Cl(3) = 171.58(4), O(1)−Ti(1)−Cl(1) = 96.98(4),
N(1)−Ti(1)−Cl(1) = 87.64(4), Cl(3)−Ti(1)−Cl(1) = 94.582(19),
O(1)−Ti(1)−Cl(2) = 94.57(4), N(1)−Ti(1)−Cl(2) = 82.96(4),
Cl(3)−Ti(1)−Cl(2) = 93.024(19), Cl(1)−Ti(1)−Cl(2) = 164.31(2),
O(1)−Ti(1)−S(1)
= 162.82(4), N(1)−Ti(1)−S(1) =
79.20(4),Cl(3)−Ti(1)−S(1) = 92.773(17), Cl(1)−Ti(1)−S(1) =
87.363(17), Cl(2)−Ti(1)−S(1) = 78.57(16).
4a/MMAO as a catalyst. Some representative results are
summarized in Table 2. Significant influences of copolymeriza-
a
Table 2. Effects of Copolymerization Conditions.
e
incorp
bc
,
b
d
RESULTS AND DISCUSSION
entry T (°C) Al/Ti
W (g)
Mw
PDI activity
(mol %)
■
Synthesis and Characterization of Complexes 4.
Complexes 4a−4m were prepared in moderate to good yields
by treatment of TiCl4 and ligands or the corresponding
deprotonated ligands as shown in Table 1. They were fully
characterized by 1H, 13C, 19F, and 31P NMR spectra and
elemental analysis. Crystal of 4h suitable for X-ray structure
determination was developed from toluene. As shown in Figure
1, complex 4h features a distorted octahedral coordination of
the titanium with three chlorine ligands in a mer position. The
bond angle sum of C(5)−S-C(6) (103.5°), C(5)−S−Ti
(96.8°), and C(6)−S−Ti(113.6°) is 313.9°, suggesting that
the S atom in 4h is sp3-hybridized. The dihedral angel between
phenyl group (R2) on enolate moiety and the C1−C2−C3−
N1−Ti1−O1 ring is 17.68°, while that between phenyl group
(R1) on imine and the C1−C2−C3−N1−Ti1−O1 ring is
71.70°.
Ethylene Copolymerization with 9-Decen-1-ol. Using
9-decen-1-ol as a model monomer, the performances of the
titanium complexes 4 were explored initially. The results
indicated that the polymerization conditions significantly
affected the copolymerization. In addition, the performance
of complexes 4a−4m on the copolymerization showed that
both the property of the coordination atom X and the
substituent of the β-carbonylenamine affected their behaviors in
the copolymerization.
1
2
3
4
5
6
7
8
0
25
40
60
40
40
40
40
1000
1000
1000
1000
200
0.2125
0.4604
0.4746
0.2209
0.1949
0.4612
0.3130
0.9612
23.8
7.7
3.0
2.8
1.6
3.5
3.4
2.6
2.7
2.8
0.7
1.5
1.5
0.7
0.6
1.5
1.0
3.3
5.8
8.2
8.8
8.5
5.8
6.7
8.8
6.4
5.6
2.9
13.1
6.8
500
2000
1000
4.1
f
6.0
a
Conditions: toluene (50 mL), 9-decen-1-ol (10 mmol) pretreated
b
with AlBui3 (12 mmol), 5 min, 3.5 μmol of catalyst. Determined by
c
d
e
f
GPC. 104 g/mol. 106 g/mol·h. Determined by 1H NMR. -Decen-1-
ol (5 mmol) pretreated with AlBui3 (6 mmol).
tion conditions on the activity of polymerization and
incorporation ratio of 9-decen-1-ol were observed. Raising the
temperature from 0 to 25 °C increased the activity to 1.5 × 106
g polymer (mol Ti)−1 h−1 and the incorporation ratio of 9-
decen-1-ol was improved to 8.2 mol % from 5.8 mol %. The
comonomer incorporation ratio of the copolymer was increased
to 8.8 mol % at 40 °C while the catalytic activity was similar to
that at 25 °C (entry 2 vs 3, Table 2). The increase of insertion
ratio is probably due to the reduction of ethylene concentration
in solvent at relatively high temperature. Further elevating the
temperature to 60 °C resulted in a decrease of activity and the
incorporation ratio was no longer increased. GPC studies of the
copolymer showed that the Mw of the polymer was temper-
ature-dependent. With the increase of the temperature, the Mw
of the polymer decreased sharply from 23.8 × 104 g/mol at 0
(1). Optimization of Copolymerization Conditions. We
first protected the hydroxyl group with 1.2 equiv of AlBui3 and
examined the copolymerization by using the titanium complex
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Macromolecules
Note
a
Table 3. Effects of the Side Arm
bc
b
d
e
,
entry
side arm (catalyst)
W (g)
Mw
5.6
PDI
activity
incorp (mol %)
1
2
3
4
SCH3(4a)
OCH3(4b)
PPh2(4c)
0.4746
0.0828
0.6430
1.6
3.2
1.5
1.5
0.3
2.1
−
8.8
6.2
4.1
−
17.7
2.9
−
N(CH2)4(4d)
−
−
a
b
Conditions: toluene (50 mL), 9-decen-1-ol (10 mmol) pretreated with AlBui3 (12 mmol), 5 min, 3.5 μmol of catalyst, 40 °C. Determined by GPC.
c
d
e
104 g/mol. 106 g/mol·h. Determined by H NMR.
1
a
Table 4. Effects of Complexes Structure on the Copolymerization
bc
b
d
e
,
entry
catalyst (umol)
R
W (g)
Mw
6.0
PDI
activity
incorp (mol %/wt %)
1
4a (3.5)
4e (3.5)
4f (3.5)
Me
nPr
iPr
0.9612
1.2709
1.2886
0.3980
1.5437
1.6332
1.5032
0.9604
0.5770
0.7006
0.2967
0.0470
0.4245
1.1933
1.5981
2.8
3.4
3.0
2.9
2.4
2.9
2.6
2.5
2.5
3.1
4.4
1.8
2.3
3.8
3.8
3.3
4.4
4.4
1.4
5.2
5.6
5.1
3.3
2.0
2.4
1.0
14
6.4/27.5
4.8/22.1
3.6/17.0
4.1/19.2
3.5/17.0
4.8/23.3
4.1/19.7
2.7/13.2
2.3/11.7
3.5/16.9
2.2/11.2
1.4/7.4
2
2.5
6.5
5.6
5.6
1.9
2.6
7.0
6.5
1.4
14.3
11.4
7.8
5.3
5.5
3
4
4g (3.5)
4h (3.5)
4i (3.5)
Ph
Cy
5
6
p-MeC6H4
p-CF3C6H4
Ph
7
4j (3.5)
8
4k (3.5)
4l (3.5)
9
10
12
4m (3.5)
4n(Zr) (3.5)
4n(Zr) (0.1)
4i (0.1)
Me
−
−
f
13
f
14
p-MeC6H4
p-MeC6H4
p-MeC6H4
130
24
3.3/16.0
2.4/12.0
2.2/11.1
g
15
4i(0.1)
h
16
4i(0.1)
16
a
Conditions: toluene (50 mL), 9-decen-1-ol (5 mmol) pretreated with AlBui3 (6 mmol), 5 min, 3.5 μmol of catalyst, 3.5 mmol of MMAO, and 40
b
c
d
e
f
g
h
°C. Determined by GPC. 104 g/mol. 106 g/mol·h. Determined by H NMR. 2 min. 30 min. 60 min.
1
°C to 2.9 × 104 g/mol at 60 °C, indicating that the high
polymerization temperature promoted the chain transfer
reaction more than chain propagation. Decreasing the Al/Ti
molar ratio from 1000 to 500, the comonomer incorporation
ratio slightly decreased to 6.7 mol % and the catalytic activity
was still maintained (entry 6, Table 2). Complex 4a showed
good activity (0.6 × 106 g polymer (mol Ti)−1 h−1) with an
incorporation ratio of 5.8 mol % even when a low amount of
MMAO (Al/Ti ratio =200) was used (entry 5, Table 2). When
the Al/Ti ratio arrived at 2000, the catalytic activity slightly
decreased and the incorporation ratio of 9-decen-1-ol did not
change (entry 7, Table 2). Reducing the initial concentration of
9-decen-1-ol resulted in the improvement of activity and
decreasement of the comonomer incorporation ratio (entry 3
vs 8, Table 2).
(2). Effects of the Side Arm. As shown in Table 3, the donor
atoms in the side arm affect the catalytic behavior significantly
in the copolymerization of ethylene with AlBui3-protected 9-
decen-1-ol, in terms of activity and comonomer incorporation
ratio. Complex 4b, with a pendant -OMe group, gave only
moderate activity (0.3 × 106 g polymer (mol Ti)−1 h−1) in a
good incorporation ratio (6.2 mol %) of comonomer (entry 2,
Table 3). And, complex 4d, bearing N(CH2)4 group, did not
produce any polymers under the same polymerization
conditions. While the complexes 4a and 4c, with a pendant
group containing sulfur and phosphine donors respectively,
showed much higher activity than the corresponding 4b and 4d
under the same conditions. These results are similar to our
previous report on the copolymerization of ethylene with α-
olefin.12 Compared with 4c, 4a gave the polymer with high
molecular weight and high incorporation ratio, probably
resulting from the steric hindrance as well as the electronic
properties of the pendant group.
(3). Substituent Effects. The substituent effects of titanium
complexes 4 on the copolymerization of ethylene and AlBui3-
protected 9-decen-1-ol are summarized in Table 4. The
substituent on the pendant group and aryl group influenced
the copolymerization activity as well as the incorporation ratio
of 9-decen-1-ol. As shown in Table 4, the activity of complex 4a
was 3.3 × 106 g polymer (mol Ti)−1 h−1 with a high
incorporation ratio (6.7 mol %). Compared with 4a, 4e with a
n-propyl thioether group gave a lower incorporation ratio of 9-
decen-1-ol (4.8 mol %) and a slightly higher activity (4.4 × 106
g polymer (mol Ti)−1 h−1) (entry 1 vs 2). Complex 4f with an
isopropyl thioether group has a much lower incorporation ratio
(3.6 mol %) and similar activity as complex 4e, suggesting that
increasing the steric hindrance on sulfur donor decreased the
incorporation ratio of comonomer. Noticeably, complex 4g
with a phenyl thioether group showed lower activity (1.4 × 106
g polymer (mol Ti)−1 h−1) than 4a (entry 4). Complex 4h with
a cyclohexylthioether group exhibited a slightly higher activity
(5.2 × 106 g polymer (mol Ti)−1 h−1) than 4f and the
comonomer incorporation ratio of the polymers obtained with
the two catalysts 4h and 4f are almost the same (entry 3 vs 5).
2873
dx.doi.org/10.1021/ma400283p | Macromolecules 2013, 46, 2870−2875

Macromolecules
Note
a
Table 5. Ethylene Copolymerization with Other Comonomers
bc
,
b
i
d
e
entry
FG (mmol)
Al/Ti
W (g)
Mw
PDI
4.8
activity
incorp /mol %
f
1
(CH2)3OH (5)
1000
1000
3000
3000
3000
1000
1000
0.8277
0.4414
1.2251
0.2689
0.8263
1.6605
4.7
n.d.
8.9
8.9
n.d.
0.3
2.9
2.8
1.5
4.2
0.9
2.8
5.7
0.4
1.4
2.9
5.6
1.8
1.9
2.5
i
i
2
3
4
5
(CH2)8OTBS (5)
(CH2)8OTBS (5)
(CH2)3OTBS (5)
(CH2)3NPri2 (5)
(CH2)8COOH (5)
(CH2)8COOMe (5)
n.d.
2.6
2.5
n.d.
2.0
2.4
i
g
6
g,h
7
0.2020
1.3
a
b
c
d
e
1
Conditions: toluene (50 mL), 5 min, 3.5 μmol of 4a, and 40 °C. Determined by GPC. 104 g/mol. 106 g/mol·h. Determined by H NMR.
f
g
h
i
Comonomer was pretreated with AlBui3 (6 mmol). Comonomer was pretreated with AlBui3 (11 mmol). 10 min. Not detected.
Electronic effects of substitute R1 on enloate moiety in ligand 4
could be observed. Compared with 4e, 4i that bears electron-
donating group at the para-position of the phenyl group (R1 =
4-MeC6H5), displayed higher activity (5.6 × 106 g polymer
(mol Ti)−1 h−1), while the introduction of electron-with-
drawing group (R1 = 4-CF3C6H5, 4k) led to a reduced activity
(3.3 × 106 g polymer (mol Ti)−1 h−1) (entry 6, 8 vs 2). The
electronic effects of substitutes on imine site are very weak. For
example, the activity of 4j with a 4-trifluoromethylphenyl
substituen on imine was similar to that of complex 4e (entry 2
vs 7). Replacing the 4-MeC6H5 group of 4j with either Me or
CF3 (4l and 4m) reduced slightly the activities. Compared with
the electronic properties, the steric hindrance has more impact
on the activity and monomer content. The molecular weight
distribution is in the range of 2.3−3.4, similar to those of
polyethylene produced by a single-site catalyst. As a control,
rac-ethenebis(indenyl)zirconium dichloride 4n proceeded the
copolymerization with an activity of 1.0 × 106 g polymer (mol
Zr)−1 h−1 and 2.2 mol % incorporation ratio under these
conditions. Further studies showed that lowering the loading of
1-amine proceeded very well with a good activity (2.8 × 106 g
polymer (mol Ti)−1 h−1) and good incorporation ratio (1.9 mol
%) (entry 5). Moreover, comonomers containing various
carbonyl groups were tested in copolymerization. The activity
(5.7 × 106 g polymer (mol Ti)−1 h−1) of 10-undecenoic acid on
the polymerization was similar to that of the corresponding
alcohol with good incorporation ratio (2.5 mol %); however,
the copolymerization of ethylene with methyl undec-10-enoate
showed one order lower activity (0.4 × 106 g polymer (mol
Ti)−1 h−1) and lower incorporation ratio (1.3 mol %) (entry 6
vs 7). In addition, molecular weight distribution of most
copolymers ranged from 2.0 to 2.6 except that of the copolymer
containing 4-penten-1-ol, which has a broad molecular weight
distribution, and the reason is unclear.
CONCLUSION
■
In summary, a series of titanium complexes bearing [ONX]
tridentate ligands has been synthesized and characterized. The
complexes with a pendant group containing sulfur and
phosphine donors, respectively, showed high activity in the
copolymerization even at low Al/Ti ratios. The electronic
properties and steric hindrance of the pendant group proved to
strongly influence the copolymerization. The highest activity of
the copolymerization of ethylene with 9-decen-1-ol reached 1.3
× 108 g polymer (mol Ti)−1 h−1 with the incorporation ratio of
3.3 mol %. In addition, they have also shown excellent
capability to catalyze the copolymerization of ethylene with 4-
penten-1-ol, 5-N,N-diisopropylamino-1-pentene, undec-10-
enoic acid, and methyl undec-10-enoate. These observations
will be helpful for the design of early transition metal catalyst
for the copolymerization of ethylene with polar olefins.
the precatalyst 4i increased the activity to 1.3 × 108
g
polymer(mol Ti)−1 h−1 with an incorporation ratio of 3.3 mol
% (entry 14). In comparison, the Zr-complex 4n showed nearly
one order lower activity (1.4 × 107 g polymer (mol Ti)−1 h−1)
in combined with MMAO under these conditions (entry 13).
Noticeably, high activities (1.6 × 107 g polymer (mol Ti)−1
h−1) could be maintained even when the polymerization time
was prolonged to 60 min. (entry 16). In this case, the insertion
ratio of monomer decreased slightly and the molecular weight
distribution widened slightly (entry 14 vs 16).
Ethylene Copolymerization with Other Comonomers.
The copolymerization of ethylene with other polar vinyl
comonomers were investigated by using 4a/MMAO. Some
representative results are summarized in Table 5. Compared
with 9-decen-1-ol, 4-penten-1-ol is also a suitable comonomer
giving good activity while the incorporation ratio was much
lower (1.4 mol %) (entry 1). The copolymerization of ethylene
and tert-butyldimethylsilyl (TBS)-protected 9-decen-1-ol pro-
ceeded very well. As shown in Table 5, complex 4a afforded
functionalized PE with high activity (1.5 × 106 g polymer (mol
Ti)−1 h−1) and good incorporation ratio (2.9 mol %) even in
the presence of an excess amount of the tert-butyl(dec-9-
enyloxy)dimethylsilane relative to MMAO (entry 2). However,
as the Al/Ti ratio was increased to 3000, the catalytic activity
and the incorporation ratio of comonomer were both improved
(entry 3). The copolymerization of ethylene with TBS-
protected 4-penten-1-ol also produced copolymer with good
activity and good incorporation ratio (entry 4). Noticeably,
ASSOCIATED CONTENT
* Supporting Information
■
S
General experimental procedures, synthesis of the ligands 3a−
3m and complexes 4a, 4e, 4f, 4g, 4i, 4j, and 4m, NMR spectra
of complexes 4a−4m, and NMR spectra of copolymers; X-ray
crystallographic data of 4h. These materials are available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: (X.-L.S.) xlsun@sioc.ac.cn; (Y.T.) tangy@sioc.ac.cn.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We are grateful for the financial support from the Natural
Sciences Foundation of China (No. 21121062, and 21174159),
■
i
even without pretreating the comonomer with Bu3Al, the
copolymerization of ethylene with N, N-diisopropylpent-4-en-
2874
dx.doi.org/10.1021/ma400283p | Macromolecules 2013, 46, 2870−2875

Macromolecules
Note
(10) Yang, X.-H.; Wang, Z.; Sun, X.-L.; Tang, Y. Dalton Trans. 2009,
8945.
(11) Yang, X.-H.; Liu, C.-R.; Wang, C.; Sun, X.-L.; Guo, Y.-H.; Wang,
X.-K.; Wang, Z.; Xie, Z.; Tang, Y. Angew. Chem., Int. Ed. 2009, 8099.
(12) Wang, C.; Ma, Z.; Sun, X.-L.; Gao, Y.; Guo, Y.-H.; Tang, Y.; Shi,
L.-P. Organometallics 2006, 25, 3259.
the Major State Basic Research Development Program (Grant
No. 2009CB825300) and the Chinese Academy of Sciences.
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