Propylene polymerization to high molecular weight atactic polypropylene and copolymerization with 1-hexene using monocyclopentadienyl titanium catalysts

Article abstract of DOI:10.1039/b921617k

A number of cyclopentadienyltitanium aryloxide complexes, 1-Ar-2,3,4,5-Me₄-Cp(2,6-ⁱPr₂C₆H ₃O)TiCl₂ (Ar = 4-Me₃SiPhenyl (5), 4- ⁱPrPhenyl (6), 4-MePhenyl (7), 3,5-(CF₃)₂Phenyl (8)) and (1-Ar-2,3,4,5-Me₄CpTiCl₂)₂(OAr′ O) (Ar′ = 4,4′-(3,3′,5,5′-ⁱPr ₄C₆H₂-C₆H₂), Ar = 4-SiMe₃Phenyl (9), 4-MePhenyl (10)) were synthesized from the reaction of a corresponding cyclopentadienyl titanium trichloride derivative with the lithium salt of a relevant phenol. The molecular structures of complexes 6, 7 and 8 were determined by X-ray crystallography. Upon activation with ⁱBu₃Al and Ph₃CB(C₆F ₅)₄, all mononuclear complexes 5-8 exhibit good catalytic activities for propylene polymerization, whereas the binuclear complexes 9 and 10 show lower catalytic activities under the same polymerization conditions. ¹³C NMR, DSC and GPC analysis indicates the produced polymers are atactic polypropylene with relatively high molecular weight. It was found that the substituents on both the cyclopentadienyl and aryloxy ligands of these complexes show obvious influence on the molecular weight of the resultant polymers with complex 5 producing the highest molecular weight atactic polypropylene. Complexes 5, 6 and 7 were also tested as catalysts for copolymerization of propylene with 1-hexene and copolymers with 1.2-10.1% comonomer incorporation were obtained in reasonable catalytic activity. The Royal Society of Chemistry 2010.

Full text of DOI:10.1039/b921617k

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PAPER
www.rsc.org/dalton | Dalton Transactions
Propylene polymerization to high molecular weight atactic polypropylene and
copolymerization with 1-hexene using monocyclopentadienyl titanium
catalysts†
Qiaolin Wu,a Qing Su,a Ling Ye,a Guanghua Lib and Ying Mu*a
Received 15th October 2009, Accepted 14th December 2009
First published as an Advance Article on the web 22nd January 2010
DOI: 10.1039/b921617k
A number of cyclopentadienyltitanium aryloxide complexes, 1-Ar-2,3,4,5-Me4-Cp(2,6-iPr2C6H3O)TiCl2
(Ar = 4-Me3SiPhenyl (5), 4-iPrPhenyl (6), 4-MePhenyl (7), 3,5-(CF3)2Phenyl (8)) and
(1-Ar-2,3,4,5-Me4CpTiCl2)2(OAr¢O) (Ar¢ = 4,4¢-(3,3¢,5,5¢-iPr4C6H2–C6H2), Ar = 4-SiMe3Phenyl (9),
4-MePhenyl (10)) were synthesized from the reaction of a corresponding cyclopentadienyl titanium
trichloride derivative with the lithium salt of a relevant phenol. The molecular structures of complexes 6,
7 and 8 were determined by X-ray crystallography. Upon activation with iBu3Al and Ph3CB(C6F5)4, all
mononuclear complexes 5–8 exhibit good catalytic activities for propylene polymerization, whereas the
binuclear complexes 9 and 10 show lower catalytic activities under the same polymerization conditions.
13C NMR, DSC and GPC analysis indicates the produced polymers are atactic polypropylene with
relatively high molecular weight. It was found that the substituents on both the cyclopentadienyl and
aryloxy ligands of these complexes show obvious influence on the molecular weight of the resultant
polymers with complex 5 producing the highest molecular weight atactic polypropylene. Complexes 5, 6
and 7 were also tested as catalysts for copolymerization of propylene with 1-hexene and copolymers
with 1.2–10.1% comonomer incorporation were obtained in reasonable catalytic activity.
atactic polypropylene and polypropylene-co-a-olefins have been
reported. High molecular weight atactic polypropylene and
polypropylene-co-a-olefins have broad application prospects as
adhesives, compatibilizers, and additives. Therefore, developing
high performance catalyst systems capable of producing this
type of polymers is of interest. Zirconocene-type complexes
Introduction
Group 4 metallocene complexes have been an important and
versatile class of olefin polymerization catalysts in the past decades,
which exhibit unique characteristics in controlling over mi-
crostructure and molecular weight of polyolefins in a wide range.1–6
In particular, the stereoselective polymerization of propylene with
metallocene catalysts has been intensively investigated.7–10 So far,
the relationship between the nature of the catalyst system and
the tacticity of the resulting polymer has been well established
for metallocene catalyst systems, which offers a great opportu-
nity for tailoring polyolefin materials.4,11–13 It has been known
that C2-symmetric ansa-metallocene catalysts5,14 produce isotac-
tic polypropylene, Cs-symmetric ansa-metallocene catalysts15 af-
ford syndiotactic polypropylene, C1-symmetric ansa-metallocene
catalysts16 provide isotactic or hemiisotactic polypropylene, and
C2v-symmetric and other achiral metallocene catalysts usually
produce atactic polypropylene.17 To date, a large amount of
studies have been devoted to the development of catalysts
for isospecific and syndiospecific polymerization of propylene.
However, only a limited number of works on the development
of metallocene catalysts for producing high molecular weight
17b,18,19
17c
Cp2ZrCl2
and meso-Et(THID)2ZrCl2
(THID, namely
tetrahydroindenyl) were studied as catalyst precursors in the
polymerization of propylene, and atactic polypropylenes with
low molecular weights were obtained. Similar complexes such
20
21
as Et(Flu)2ZrCl2 and Me2Si(Flu)2ZrCl2 were found to pro-
duce high molecular weight atactic polypropene (Mw = 1~4 ¥
105). Et(Ind)2ZrCl2, Ph2C(Flu)(Cp)ZrCl2,22 Et(THID)2ZrCl2 and
iPr(Flu)(Cp)ZrCl2 have been studied as catalysts for the copoly-
23
merization of propylene with higher a-olefins to yield isotactic
23
and syndiotactic propylene-a-olefin copolymers while Cp2ZrCl2
has been used as catalyst for producing atactic propylene-1-hexene
copolymers. On the other hand, [Me2Si(C5Me4)(NR)]TiCl2/MAO
(methylaluminoxane) systems24 were reported to yield high molec-
ular weight syndiotactic-enriched atactic polypropylene at rela-
t
tively low polymerization temperatures (R = Bu, Mw = 4 ¥ 105 at
30 ◦C; R = adamantyl, Mw = 5~7 ¥ 105 at 40 ◦C; R = cyclododecyl,
Mw = 13~18 ¥ 105 at 40 ◦C). A number of monocyclopentadi-
enyltitanium(IV) trichlorides25 and their derivatives26,27 were also
reported to produce atactic polypropylene, but analogous mono-
cyclopentadienylzirconium complexes28 were found to promote
atactic-specific oligomerization of propylene.
aState Key Laboratory for Supramolecular Structure and Materials, School
of Chemistry, Jilin University, 2699 Qianjin Street, Changchun, 130012,
People’s Republic of China. E-mail: ymu@jlu.edu.cn; Fax: +86-431-
5193421; Tel: +86-431-5168472
bState Key Laboratory of Inorganic Synthesis and Preparative Chemistry,
School of Chemistry, Jilin University, 2699 Qianjin Street, Changchun,
130012, People’s Republic of China
In recent years, Nomura’s group has developed a type of non-
bridged cyclopentadienyltitanium aryloxide complexes29 as high
performance catalysts for the copolymerization of ethylene with
a-olefins to produce high molecular weight copolymers. On the
† CCDC reference numbers 750232–750234. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b921617k
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Scheme 1 Synthetic procedure of complexes 1–4.
basis of knowledge on structure and property of metallocene
catalysts, it could be expected that this type of catalyst might
show good performance, too, for propylene polymerization to
yield high molecular weight atactic polypropylene. However, one
example has been reported for polymerization of propylene with
this type of complexes, such as Cp*Ti(O-2,6-iPrC6H3)Cl2,29c in
the presence of MAO and these titanium catalysts containing
aryloxide ligands have also been active for polymerization of
1-hexene in the presence of MAO or borate co-catalyst. No
further studies for producing higher molecular weight atactic
polypropylene with this type of catalysts have been reported so far.
To develop new catalysts of the type for this purpose, we have syn-
thesized a number of new non-bridged cyclopentadienyltitanium
aryloxide complexes, 1-Ar-2,3,4,5-Me4-Cp(2,6-iPr2C6H3O)TiCl2
(Ar = 4-Me3SiPhenyl (5), 4-iPrPhenyl (6), 4-MePhenyl (7), 3,5-
(CF3)2Phenyl (8)) and (1-Ar-2,3,4,5-Me4CpTiCl2)2(OAr¢O) (Ar¢ =
4,4¢-(3,3¢,5,5¢- iPr4C6H2–C6H2), Ar = 4-SiMe3Phenyl (9), 4-
MePhenyl (10)), from their corresponding cyclopentadienyltita-
nium trichlorides, 1-Ar-2,3,4,5-Me4CpTiCl3 (Ar = 4-Me3SiPhenyl
(1), 4-iPrPhenyl (2), 4-MePhenyl (3), 3,5-(CF3)2Phenyl (4)), and
studied their catalytic properties for propylene homopolymeriza-
tion. By introducing a bulky aryl group (which can be easily
introduced) into the Me4Cp group, these catalysts have a more
crowded coordination environment with the bulky aryl group in
front of the metal center, which might slow down the rate of
chain transfer through b-H elimination during the polymerization
and therefore increase the molecular weight of the produced
polymer. In addition, considering that complexes of this type are
good catalysts for copolymerization of ethylene with a-olefins,
we also briefly investigated the catalytic properties of complexes
5, 6 and 7 for copolymerization of propylene with 1-hexene.
The binuclear complexes 9 and 10 were synthesized mainly for
examining the possible cooperative effect of the two metal centers.
Herein we wish to report the synthesis and characterization of the
new complexes 5–10, their catalytic performance for propylene
homopolymerization and copolymerization with 1-hexene, as
well as the characterization of the resulting polypropylenes and
propylene–1-hexene copolymers.
Et2O, followed by treatment of the reaction mixture with
concentrated HCl at room temperature, gives the free ligands
L1–L4 in high yields, respectively. The aryllithium salts were
obtained by treating 1-bromo-4-trimethylsilylbenzene, 1-bromo-
4-isopropylbenzene, 1-bromo-4-methylbenzene, or 1-bromo-3,5-
bis(trifluoromethyl)benzene with 1 equiv. of n-BuLi at low
temperature. The synthetic reaction was also tried in THF,
which gave the products in lower yields. The free ligands
L1–L4 were all characterized by elemental analyses and 1H
1
NMR spectroscopy. H NMR analysis indicates that the freshly
prepared compounds L1–L4 exist mainly in the form of one
isomer, not as a mixture of three isomers as observed in
the N,N-dimethylaminophenyltetramethylcyclopentadiene32 and
tetramethylcyclopentadienyl-phenol33 ligand systems.
Synthesis of complexes 1–4
Complexes 1–4 were synthesized in similar way to the published
procedure34,35 in high yields as red or orange solids (Scheme 1).
Deprotonation of the free ligands L1–L4 with n-butyl lithium in
THF, followed by the reaction with chlorotrimethylsilane, gives the
trimethylsilyl substituted derivatives of L1–L4, respectively. The
subsequent reactions of these trimethylsilyl substituted derivatives
with TiCl4 in toluene produce the corresponding complexes 1–4.
These complexes are well soluble in methylene chloride, diethyl
ether, toluene and benzene, while slightly soluble in n-hexane and
n-pentane. Complexes 1–4 were found to be relatively stable to
air and moisture in the solid state, while readily decomposed
in solution when exposed to air. These titanium complexes
1
were all characterized by H and 13C NMR spectroscopy along
with elemental analyses. The chemical shifts observed for the
protons of the CpCH3 moiety in complexes 1–4 (ca. 2.00–
2.47 ppm) are significantly downfield shifted in comparison with
the corresponding signals of their free Cp ligands. The 13C NMR
spectra show that complexes 1–4 have similar resonance signals for
the methyl carbons on the Cp ligands (two characteristic signals
at ca. 14.0–15.5 ppm for the four methyl carbons). The NMR
spectral features of complexes 1–4 indicate that these molecules
are symmetric in solution.
Results and discussion
Synthesis of complexes 5–10
Synthesis of the free ligands L1–L4
Complexes 5–8 were synthesized in relatively high yields (75–
80%) by reactions of 2,6-iPr2C6H3OLi (Scheme 2) with the
cyclopentadienyltitanium trichloride derivatives 1–4, respectively.
These reactions were usually carried out in toluene at 80 C for
12 h to make the reaction go to completion. The synthetic reaction
The free ligands 1-aryl-2,3,4,5-tetramethylcyclopentadiene L1–
L4 were synthesized using a modified literature procedure as
shown in Scheme 1.30,31 The reaction of 2,3,4,5-tetramethyl-
2-cyclopentenone with the corresponding aryllithium salt in
◦
2526 | Dalton Trans., 2010, 39, 2525–2535
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Scheme 2 Synthetic procedure of complexes 5–10.
was also tested in Et2O and THF, from which the desired product
was obtained in lower isolated yields. The binuclear titanium com-
plexes 9 and 10 were obtained by a similar procedure (Scheme 2)
from the reactions of 4,4¢-(3,3¢,5,5¢-iPr4C6H2–C6H2)O2Li2 with
the cyclopentadienyltitanium trichloride derivatives 1 and 3,
respectively. The isolated yields for complexes 9 and 10 (~70%)
are lower than those for complexes 5–8, which is understandable
since any undesired reaction or decomposition happening on one
side of either the dilithium salt of the biphenol ligand or the
formed binuclear complexwillcause the lose of the whole binuclear
complex molecule and thus lead to lower yields. Complexes 5–
10 are quite soluble in methylene chloride, toluene, benzene, and
diethyl ether, but less soluble in n-pentane and n-hexane. These
complexes were found to be more air and moisture sensitive in
solution than complexes 1–4 and the recrystalization of these
complexes must be handled very carefully to avoid the formation
of oxo-bridged complexes. Complexes 5–10 were all characterized
by elemental analyses, 1H and 13C NMR spectroscopy and
satisfactory analytic results were obtained. The 1H NMR signals
for the CpCH3 protons in complexes 5–10 shift slightly to higher
field compared to the corresponding signals in complexes 1–4,
and the 13C NMR signals for the CpCH3 carbons in complexes
5–10 shift about 1.0–1.6 ppm to higher field compared to the
corresponding signals in complexes 1–4. The 13C NMR spectra of
complexes 5–10 all show a down-field resonance about 160 ppm,
which can be assigned to the carbon adjacent to the oxygen atom
in the aryloxy ligand.
Fig. 1 Structure of complex 6 (Thermal ellipsoids are drawn at the 30%
probability level). Hydrogen atoms are omitted for clarity.
Crystal structures of complexes 6, 7 and 8
Molecular structures of complexes 6, 7 and 8 were determined by
single-crystal X-ray diffraction analysis. The ORTEP drawings of
molecule structures are shown in Fig. 1, 2 and 3, respectively. The
selected bond lengths and angles were summarized in Table 1. The
X-ray crystal structural analysis reveals complexes 6, 7 and 8 all
adopt a distorted tetrahedral geometry in the solid state with their
two bulky aryl groups folded on one side of their central titanium
atom due to the packing force. The Ti–O distances of complexes
Fig. 2 Structure of complex 7 (Thermal ellipsoids are drawn at the 30%
probability level). Hydrogen atoms are omitted for clarity.
catalytic performance of these complexes. The Ti–O–C angles for
complexes 6 (168.4(2)◦), 7 (166.77(14)◦) and 8 (170.2(3)◦), together
with the corresponding Ti–O distances, suggest that the Ti–O bond
in these complexes may be additionally stabilized by partial p-
donation from the oxygen atom of the aryloxy ligand. Other key
bond lengths and angles listed in Table 1 are comparable with
those values previously reported for similar titanium complexes.38
The dihedral angle between the Cp ring and the adjacent phenyl
ring in complex 8 (58.7(1)◦) is larger than the ones in 6 (43.7(2)◦)
˚
˚
˚
6 (1.773(2) A), 7 (1.784(2) A) and 8 (1.779(3) A) are in the range
29e,36
˚
of 1.772–1.820 A reported for their analogues.
Ti–Cl distances in complexes 6 (2.268(1) A), 7 (2.268(1) A) and 8
(2.267(1) A) are also in the range of observed values (2.250–2.305
A) for known dichloro titanium complexes.
The average
˚
˚
˚
36,37
˚
The Cp(cent)–
Ti–O angles are 127.1(3)◦ for 6, 119.0(1)◦ for 7 and 124.2(3)◦
for 8, which are related to the sterically open degree in front of
the titanium atom in these complexes, and might influence the
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Table 1 Selected bond lengths and angles for complexes 6, 7 and 8
Complex 6
Ti(1)–C(1)
Ti(1)–C(2)
Ti(1)–C(3)
Ti(1)–C(4)
Ti(1)–C(5)
Ti(1)–Cl(1)
Ti(1)–Cl(2)
Ti(1)–O(1)
Ti(1)–Cp(cent)
2.359(3)
2.342(3)
2.351(3)
2.401(3)
2.402(3)
2.2719(12)
2.2643(13)
1.773(2)
2.086(1)
Ti(1)–O(1)–C(19)
O(1)–Ti(1)–Cl(1)
O(1)–Ti(1)–Cl(2)
Cl(2)–Ti(1)–Cl(1)
O(1)–Ti(1)–C(1)
O(1)–Ti(1)–C(2)
O(1)–Ti(1)–C(3)
O(1)–Ti(1)–C(4)
O(1)–Ti(1)–C(5)
168.4(2)
102.97(8)
102.54(8)
100.88(5)
106.10(11)
88.77(11)
107.52(12)
142.07(12)
141.38(12)
Complex 7
Ti(1)–C(1)
Ti(1)–C(2)
Ti(1)–C(3)
Ti(1)–C(4)
Ti(1)–C(5)
Ti(1)–Cl(1)
Ti(1)–Cl(2)
Ti(1)–O(1)
Ti(1)–Cp(cent)
2.383(2)
2.419(2)
2.392(2)
2.337(2)
2.355(2)
2.2774(8)
2.2600(8)
1.7839(16)
2.049(11)
Ti(1)–O(1)–C(17)
O(1)–Ti(1)–Cl(1)
O(1)–Ti(1)–Cl(2)
Cl(2)–Ti(1)–Cl(1)
O(1)–Ti(1)–C(1)
O(1)–Ti(1)–C(2)
O(1)–Ti(1)–C(3)
O(1)–Ti(1)–C(4)
O(1)–Ti(1)–C(5)
166.77(14)
102.77(5)
103.91(6)
100.31(3)
105.83(7)
140.51(7)
141.28(8)
106.40(8)
88.08(7)
Fig. 3 Structure of complex 8 (Thermal ellipsoids are drawn at the 30%
probability level). Hydrogen atoms are omitted for clarity.
Complex 8
rized in Table 2. Upon activation with Al(iBu)3 and Ph3CB(C6F5)4,
complexes 5–10 all exhibit moderate catalytic activity (1156–
3436 kg PP (mol Ti)-1 h-1) for propylene polymerization. Under
similar conditions, the catalytic activity increases in the order
of 10 < 9 < 8 < 7 < 6 < 5, which indicates that the catalytic
activity of these complexes is notably affected by the nature of the
substituents on both the cyclopentadienyl and aryloxy ligands,
and increases with the increase in the electron-donating ability
of the aryl group on the Cp ring although the variation in the
catalytic activity is not very significant. It is well known for
group 4 metallocene catalysts that electron-donating substituents
on the ligands would stabilize the catalytically active cationic
species formed during the polymerization and therefore improve
the catalytic activity.39 The observed weak electronic effect may
be due to that the considered electron-donating or -withdrawing
Ti(1)–C(1)
Ti(1)–C(2)
Ti(1)–C(3)
Ti(1)–C(4)
Ti(1)–C(5)
Ti(1)–Cl(1)
Ti(1)–Cl(2)
Ti(1)–O(1)
Ti(1)–Cp(cent)
2.351(4)
2.405(4)
2.396(4)
2.352(4)
2.349(4)
2.2685(14)
2.2657(12)
1.776(3)
2.084(1)
Ti(1)–O(1)–C(17)
O(1)–Ti(1)–Cl(1)
O(1)–Ti(1)–Cl(2)
Cl(2)–Ti(1)–Cl(1)
O(1)–Ti(1)–C(1)
O(1)–Ti(1)–C(2)
O(1)–Ti(1)–C(3)
O(1)–Ti(1)–C(4)
O(1)–Ti(1)–C(5)
170.2(3)
103.39(12)
102.90(12)
100.39(5)
106.05(14)
141.07(14)
141.79(16)
107.13(16)
88.40(14)
and 7 (49.6(1)◦), which should result from the integrated steric
interaction among the two bulky aryl groups and the Me4Cp ring
in these complexes.
Propylene polymerization studies
i
Propylene polymerization using complexes 5–10 as pre-catalysts
substituents (Me, F3C, Pr, Me3Si) on the aryl group are too far
under different conditions was studied, and the results are summa-
away from the metal center. In comparison with complex 7, the
a
Table 2 Summary of propylene polymerization catalyzed by complexes 5–10 activated with Al(iBu)3 and Ph3CB(C6F5)4
T/◦C
Yield/g
Activityb
Mw ¥10-4
Mw/Mn
Mh ¥10-4
Tg/◦Ce
c
c
d
Run
Catalyst
Al : Ti
1
2
3
4
5
6
7
8
5
5
5
5
5
5
5
6
6
7
7
8
8
9
10
100
200
300
500
200
200
200
100
200
100
200
100
200
200
200
70
70
70
70
50
60
80
70
70
70
70
70
70
70
70
5.76
8.32
7.38
3.22
4.80
6.53
8.59
5.40
7.21
4.35
6.50
3.92
6.17
3.16
2.89
2304
3328
2952
1288
1920
2612
3436
2160
2884
1740
2600
1568
2468
1264
1156
29.5
23.8
2.58
3.06
28.3
22.7
20.1
16.5
30.6
26.7
19.8
21.6
17.5
20.4
17.2
22.1
18.3
22.6
18.6
-3.7
-4.6
9
19.8
18.1
2.31
3.27
-6.5
-6.9
10
11
12
13
14
15
20.0
23.3
18.9
2.30
3.14
2.91
-5.5
-4.9
-5.6
a Polymerization conditions: toluene solution, catalyst 5.0 mmol (2.5 mmol for 9 and 10), B/Ti ratio 1.25, time 30 min, propylene pressure 5 bar.
b Polymerization activity: kg PP (mol Ti) -1 h-1. c Measured by GPC analysis. d Intrinsic viscosity measured at 135 ◦C in THN. e Measured by DSC.
2528 | Dalton Trans., 2010, 39, 2525–2535
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catalyst activity of complex 8 doesn’t decrease very much, which
may suggest that, except the electronic effect, the steric effect
of the ligand on the catalytic activity also works by affecting
the interaction between the catalytically active cationic species
and the anionic co-catalyst. Similar results have been previously
reported by Waymouth et al. for (2-Ar-Ind)2ZrCl2/MAO catalyst
systems.40 The mononuclear complexes 5–8 exhibit higher catalytic
activity than the binuclear complexes 9 and 10 do under the
same conditions, which implies that there is no cooperative effect
between the two metal centers41 in these binuclear catalyst systems.
The binuclear complexes showing lower catalytic activity might be
attributed to at least two factors. One is that any half part of the
binuclear active cationic species formed during the polymerization
can be considered as an electron-withdrawing group for another
half part of the active species and will lower each other’s catalytic
activity. Another factor is that the binuclear active cationic species
carries two positive charges and thus should show relatively lower
solubility in solution, which will cause the binuclear complexes
to exhibit lower catalytic activity. The catalytic activity of these
binuclear catalysts changes in the same trend as observed in the
mononuclear catalyst systems under similar conditions, and in-
creases with the increase in the electron-donating ability of the aryl
group on the Cp ring. In addition, the observed catalytic activity
of these titanium complexes is also affected by the Al/Ti molar
ratio with the highest catalytic activity being reached at the Al/Ti
ratio about 200 for all catalysts. The catalytic activity of these
catalysts is dependent on the polymerization temperature too, and
increases with the increase in polymerization temperature. On the
other hand, the molecular weight of the resultant polypropylene
decreases with the increase in polymerization temperature. These
results are in agreement with those reported previously for similar
catalyst systems.42
group on the cyclopentadienyl ligand, which is reasonable since
the bulky aryl group on the cyclopentadienyl ligand would stay in
front of the central metal during the polymerization and therefore
would lower the chain-transfer rate and increase the molecular
weight of the resultant polymer. The binuclear complexes 9 and
10 produce polypropylene with molecular weight similar to or
slightly higher than the one produced by their corresponding
mononuclear complex 5 and 7, indicating that the size of the
substituent on the para position of the aryloxy ligand exerts
little influence on the molecular weight of the resultant polymer.
The 2,6-diisopropylphenoxy ligand was used in these complexes
because it has been reported that the 2,6-diisopropylphenoxy
complexes of this type show the best catalytic performance for
the copolymerization of ethylene with a-olefins.43
1
The H NMR spectrum of a typical polypropylene sample is
illustrated in Fig. 5. The resonances at 4.91 and 4.97 ppm could
be assigned to the protons of the vinylidene end group, while the
resonance at 5.03 ppm may be tentatively assigned to the olefinic
=
proton in the isobutenyl end group Me2C CH– which is possibly
formed by isomerization of the terminal vinylidene as discussed in
literature for a propylene isotactic polymerization system.44 There
is no other olefinic group, such as vinyl or internal olefin group
1
can be seen from the H NMR spectrum. The formation of the
vinylidene end group is indicative of that the b-H elimination is
a major chain transfer reaction for these systems. The 13C NMR
spectrum of the same polypropylene sample is shown in Fig. 6.
The observed resonances of the methyl carbons (20.0–22.5 ppm)
in the polymer are characteristic for atactic polypropylene.45
The gel permeation chromatography (GPC) analysis reveals
that the polypropylene obtained with complexes 5–10 possesses
relatively high molecular weight with unimodal molecular weight
distribution (Mw = 16–30 ¥ 104, Mw/Mn = 2.3–3.3). A typical
GPC diagram is shown in Fig. 4. The Mw value of the polypropy-
lene obtained under similar conditions is obviously dependant on
the structure of the catalyst and increases in the order of 7 < 10 <
6 < 8 < 9, 5. These results indicate that the molecular weight of the
produced polypropylene is mainly influenced by the size of the aryl
Fig. 5 1H NMR spectrum of the polypropylene obtained with catalyst 5
(run 2 in Table 2).
The calculated dyad, triad and pentad distributions for two
typical polypropylene samples listed in Table 3 reveal that the
polypropylene obtained with these catalysts is a kind of syndiotac-
tically enriched atactic polypropylene with r (54–55%) being larger
than m (45–46%) about 9%. By analyzing the triad distribution, it
can be seen that the values of 4[mm][rr]/[mr]2 (1.07 and 0.99 for
samples from run 2 and 14, respectively) are close to 1, which is in
agreement with the statistical model of Bernoullian.46 In addition,
the 13C NMR analysis indicates that the polypropylene produced
by these catalysts is mainly made up of 1,2-insertion units with
a little of 2,1-insertion and 1,3-enchainment units.47 The DSC
analysis on the polymer samples also confirms that the obtained
polymers are atactic polypropylenes which all show a glass
transition temperature (Tg) in the range of -7 to -3 ◦C, but no
melting endotherm.
Fig. 4 The GPC trace of the polypropylene sample prepared with catalyst
8 (run 13 in Table 2).
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Table 3 Pentad, triad and dyad distribution and statistical analysis for typical polypropylenes
Pentads (%)
Triads (%)
Dyads (%)
Sample
mmmm
mmmr
rmmr
mmrr
mmrm/rmrr mrmr
rrrr
rrrm
mrrm
mm
mr
rr
m
r
Run 2
Run 14
4.91
3.79
9.81
9.90
6.65
7.13
12.17
12.73
22.94
22.63
13.66
14.32
7.88
8.07
14.56
15.08
7.42
6.35
21.37
20.82
48.77
49.68
29.86
29.50
45.75
45.66
54.25
54.34
Table 4 Summary of propylene/1-hexene copolymerization catalyzed by complexes 5, 6 and 7 activated with Al(iBu)3 and Ph3CB(C6F5)4
a
1-hexene/mol L-1
Yield/g
Activityb
Mw ¥10-4
Mw/Mn
1-hexene contentd (mol%)
c
c
Run
Catalyst
1
2
3
4
5
6
7
8
5
5
5
5
6
6
7
7
0.05
0.10
0.20
0.50
0.20
0.50
0.20
0.50
1.38
0.91
0.67
0.53
0.59
0.42
0.58
0.43
920
607
447
353
393
280
387
286
18.93
17.26
13.10
10.24
12.85
10.08
12.60
9.81
2.69
3.51
2.33
2.62
3.06
2.44
2.38
2.75
1.28
2.70
5.25
9.57
5.28
9.63
5.36
10.11
a Polymerization conditions: toluene solution, temperature 70 ◦C, catalyst 3.0 mmol, B/Ti ratio 1.25, time 30 min, propylene pressure 5 bar. b Polymerization
activity: kg polymer (mol Ti) -1 h-1. c Measured by GPC analysis. d Calculated by 13C NMR spectra.
Fig. 6 13C NMR spectrum of the polypropylene obtained with catalyst 5 (run 2 in Table 2).
Propylene/1-hexene copolymerization studies
in the HH dyad sequence22 has been observed in the 13C NMR
spectra, it can be known that the 1-hexene units in the polymer
chain are essentially isolated by propylene units. Based on the
13C NMR analysis, the comonomer content of the copolymer
samples was calculated and listed in Table 4. In addition to
the comonomer concentration, it seems that the comonomer
incorporation is also affected by the structure of the catalyst.
The comonomer content of the copolymers obtained with catalyst
7 is somewhat higher than that of the copolymers produced by
catalyst 5 under similar conditions, due probably to that the
catalytically active species of 7 is less bulky and carries more
positive charge than the one of 5 does and therefore more favors
the coordination of the bulky comonomer. DSC analysis on the
copolymer samples indicates that the resulting copolymers are
amorphous, and the crystallization process could not be observed.
GPC analysis reveals that the molecular weight of the obtained
propylene-1-hexene copolymers (Mw = 10–19 ¥ 104) produced by
Complexes 5, 6 and 7 were briefly tested for the copolymerization
of propylene with 1-hexene, and the results are listed in Table 4.
The catalytic activities of these complexes in the copolymer-
ization reactions were found to decrease with increasing the
feed concentration of 1-hexene under similar conditions, and no
comonomer effect was observed. Obvious comonomer effect has
previously been observed in Me2Si(Ind)2ZrCl2/MAO catalyzed
propylene/1-hexene copolymerization reaction.22 The propylene-
1-hexene copolymers were analyzed by 13C NMR and the 13C
NMR spectrum of a typical copolymer sample is shown in Fig. 7.
The assignments for the observed resonances are made according
to the published literatures.48–50 The 13C NMR analysis indicates
that the obtained copolymers are atactic and the comonomer 1-
hexene is randomly incorporated into the polymer chains. Since
no resonance in the region of 41–43 ppm for the aa carbon
2530 | Dalton Trans., 2010, 39, 2525–2535
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1-bromo-4-trimethylsilylbenzene were purchased from Aldrich.
53
2,3,4,5-tetramethyl-2-cyclopentenone52 and Ph3CB(C6F5)4 were
1
prepared according to literature procedures. H and 13C NMR
spectra were measured using a Varian Mercury-300 NMR spec-
trometer. Elemental analyses were performed on a Perkin-Elmer
240c element analyzer. Viscosity-average molecular weights of the
◦
polypropylenes were determined in THN at 135 C using Schott
Gerate Mod. AVS/T2 Ubbelohde viscosimeter. Molecular weight
and Molecular weight distribution of the polypropylenes and
propyl◦ene-1-hexene copolymers were measured on a PL-GPC 220
at 140 C with 1,2,4-trichlobenzene as solvent. 1H NMR spectra of
the polymers were recorded on a Varian Mercury-300 NMR spec-
trometer with CDCl3 as solvent.13C NMR spectra of the polymers
were recorded on a Varian Unity-400 NMR spectrometer at 110 ◦C
with o-C6D4Cl2 as solvent. Glass transition temperatures (Tg)
were measured by differential scanning calorimetry (DSC) on a
NETZSCH DSC 204 with the heating/cooling rate at 10 ◦C min-1
from -50 to 200 ◦C, upon the second heating scan.
Fig. 7 13C NMR spectra of copolymer propylene-1-hexene together with
assignments of the corresponding peaks. (Run 4 in Table 4.)
Synthesis of 1-(4¢-trimethylsilylphenyl)-2,3,4,5-tetramethyl-
cyclopentadiene (L1). A solution of n-BuLi (12.5 mmol) was
added dropwise to a solution of 1-bromo-4-trimethylsilylbenzene
these catalysts is much higher than that of the copolymers obtained
with the Cp2ZrCl2 catalyst system,23 and the molecular weight
distribution is basically unimodal and narrow, being characteristic
for metallocene polyolefins.
◦
(2.86 g, 12.5 mmol) in Et2O (60 mL) at -25 C and the reaction
mixture was allowed to warm to room temperature. After
◦
four hours, the solution was cooled to -15 C, and a solution of
Conclusions
2,3,4,5-tetramethyl-2-cyclopentenone (1.72 g, 12.5 mmol) in Et2O
(20 mL) was added. The mixture was allowed to warm to room
temperature and stirred overnight. The reaction was quenched
with 100 mL of H2O and then acidified with 3 mL of concentrated
HCl. The organic layer was separated, dried over MgSO4, filtered
and concentrated by distillation under reduced pressure. Pure
product (3.12 g, 92.5%) was obtained as yellowish oil by column
chromatography over silica (petroleum ether). Anal. calcd for
A number of cyclopentadienyltitanium aryloxide complexes 5–
10 have been synthesized in relatively high yields from the
reaction of cyclopentadienyltitanium trichloride derivatives 1–4
with the corresponding lithium phenoxide. These new complexes
1
were all characterized by elemental analyses, H and 13C NMR
spectroscopy, and the molecular structures of complexes 6–8
were determined by X-ray crystallography. Upon activation with
iBu3Al/Ph3CB(C6F5)4, all complexes 5–10 exhibit good catalytic
activities for propylene polymerization, and produce syndiotacti-
cally enriched atactic polypropylene with high molecular weight.
The molecular weight of the resultant polymers is mainly influ-
enced by the size of the aryl group on the cyclopentadienyl ligand
in these complexes. Complexes 5 with 4¢-trimethylsilylphenyl
substituted cyclopentadienyl ligand produce atactic polypropy-
lene with the highest molecular weight. Complexes 5, 6 and 7
show reasonable catalytic activities for the copolymerization of
propylene with 1-hexene, producing poly(propylene-co-1-hexene)
with relatively high molecular weight (Mw = 10–19 ¥ 104) and
comonomer incorporation (up to 10 mol% 1-hexene).
1
C28H26Si (270.48): C 79.93, H 9.69. Found: C 79.65, H 9.52. H
NMR (CDCl3, 300 MHz; 298 K): d 7.51 (d, J = 8.1 Hz, 2 H,
Ph), 7.24 (d, J = 8.4 Hz, 2 H, Ph), 3.20 (q, 1 H, Cp), 2.05 (d, J =
1.8 Hz, 3 H, Cp-Me), 1.93 (s, 3 H, Cp-Me), 1.87 (s, 3 H, Cp-Me),
0.97 (d, J = 7.5 Hz, 3 H, Cp-Me), 0.28 (s, 9 H, SiMe3).
Synthesis of 1-(4¢-isopropylphenyl)-2,3,4,5-tetramethyl-cyclo-
pentadiene (L2). Ligand L2 was prepared in the same manner
as L1 with 12.5 mmol of 1-bromo-4-isopropylbenzene as starting
material. Pure product (2.80 g, 93.0%) was obtained as yellowish
oil. Anal. calcd for C18H24 (240.37): C 89.94, H 10.06. Found: C
1
89.60, H 9.93. H NMR (CDCl3, 300 MHz; 298 K): d 7.20 (m,
4 H, Ph), 3.18 (q, 1 H, Cp), 2.92 (m, 1 H, iPr), 2.04 (d, J = 1.8 Hz,
3 H, Cp-Me), 1.94 (s, 3 H, Cp-Me), 1.87 (s, 3 H, Cp-Me), 1.28 (d,
J = 6.9 Hz, 6 H, iPr), 0.97 (d, J = 7.8 Hz, 3 H, Cp-Me).
Experimental
Synthesis of 1-(4¢-methylphenyl)-2,3,4,5-tetramethyl-cyclo-
pentadiene (L3). Ligand L3 was prepared in the same manner
as L1 with 12.5 mmol of 1-bromo-4-methylbenzene as starting
material. Pure product (2.42 g, 91.6%) was obtained as yellowish
oil. Anal. calcd for C16H20 (212.16): C 90.51, H 9.49. Found: C
General comments
All manipulations involving air- and/or moisture-sensitive
compounds were carried out under an argon atmo-
sphere (ultra-high purity) using either standard Schlenk
techniques or glove box techniques. Solvents were dried
and distilled prior to use.51 Polymerization grade propy-
1
90.27, H 9.30. H NMR (CDCl3, 300 MHz; 298 K): d 7.19 (s,
4 H, Ph), 3.17 (q, 1 H, Cp), 2.02 (d, J = 1.8 Hz, 3 H, Cp-Me),
1.90 (s, 3 H, Cp-Me), 1.83 (s, 3 H, Cp-Me), 0.95 (d, J = 7.5 Hz,
3 H, Cp-Me).
lene was further purified by passage through columns of
i
˚
4 A molecular sieves and MnO. Al( Bu)3, n-BuLi, TiCl4,
2,6-bis-isopropylphenol, 1-bromo-4-methylbenzene, 1-bromo-4-
isopropylbenzene, 1-bromo-3,5-bis-trifluoromethylbenzene, and
Synthesis of 1-(3¢,5¢-bi-trifluoromethylphenyl)-2,3,4,5-tetra-
methyl-cyclopentadiene (L4). Ligand L4 was prepared in
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the same manner as L1 with 12.5 mmol of 1-bromo-3,5-bi-
trifluoromethylbenzene as starting material. Pure product (3.80 g,
91.0%) was obtained as yellowish oil. Anal. calcd for C17H16F6
chloride/n-hexane (1 : 3 in v/v). Anal. calcd for C17H15Cl3F6Ti
(487.52): C 50.90, H 6.17. Found: C 50.62, H 6.03. H NMR
(CDCl3, 300 MHz; 298 K): d 7.93 (s, 1 H, Ph), 7.85 (s, 2 H, Ph),
2.45 (s, 6 H, Cp-Me), 2.44 (s, 6 H, Cp-Me). 13C NMR (CDCl3,
75 MHz; 298 K): d 138.6, 137.2, 135.7, 135.0, 132.1, 130.6, 122.4,
121.9, 15.3, 14.0.
1
1
(334.30): C 61.08, H 4.82. Found: C 60.94, H 4.67. H NMR
(CDCl3, 300 MHz; 298 K): d 7.62 (s, 1 H, Ph), 7.44 (s, 2 H, Ph),
3.18 (q, 1 H, Cp), 2.06 (d, J = 1.8 Hz, 3 H, Cp-Me), 1.91 (s, 3 H,
Cp-Me), 1.85 (s, 3 H, Cp-Me), 0.96 (d, J = 7.8 Hz, 3 H, Cp-Me).
Synthesis of 1-(4¢-trimethylsilyl-phenyl)-2,3,4,5-tetramethyl-
cyclopentadienyl-TiCl2(O-2,6-di-isopropyl-C6H3) (5). A solution
of n-BuLi (3.80 mmol) was added dropwise to a solution of 2,6-
diisopropylphenol (0.680 g, 3.80 mmol) in Et2O (30 mL) at -25 ◦C.
The reaction mixture was allowed to warm to room temperature
and stirred for 2 h. The solvent was removed in vacuo and the
residue was washed with hexane. The obtained white powder
was dissolved in toluene (10 mL), and then a solution of 1-
(4¢-trimethylsilyl-phenyl)-2,3,4,5-tetramethyl-cyclopentadienyl ti-
tanium trichloride (1.48 g, 3.50 mmol) in toluene (15 mL) was
added at room temperature. The reaction mixture was heated
to 80 ◦C and stirred for 12 h. The mixture was filtered and the
precipitate was washed with toluene (2 ¥ 5 mL). The filtrate was
concentrated to leave a black-red residue. Recrystallization from
CH2Cl2–n-hexane (1 : 3) gave pure 5 as red crystals (1.60 g, 80.6%).
Anal. calcd for C30H42Cl2OSiTi (565.52): C 63.60, H 7.65. Found:
C 62.49, H 7.20. 1H NMR (CDCl3, 300 MHz; 298 K): d 7.56 (d,
J = 8.1 Hz, 2 H, Ph), 7.47 (d, J = 8.1 Hz, 2 H, Ph), 6.99 (m,
3 H, Ph), 3.02 (m, 2 H, Ar-iPr), 2.30 (s, 6 H, Cp-Me), 2.29 (s, 6 H,
Cp-Me), 1.03 (d, J = 7.2 Hz, 12 H, Ar-iPr), 0.30 (s, 9 H, Si-Me).
13C NMR (CDCl3, 75 MHz; 298 K): d 159.9, 140.7, 139.6, 136.8,
133.6, 133.1, 130.8, 129.6, 123.5, 123.1, 26.7, 23.7, 13.9, 13.2, -1.2.
Synthesis of 1-(4¢-trimethylsilylphenyl)-2,3,4,5-tetramethyl-cy-
clopentadienyl titanium trichloride (1). A solution of n-BuLi (8.50
mmol) was added dropwise to a solution of 1-(4¢-trimethylsilyl-
phenyl)-2,3,4,5-tetramethyl-cyclopentadiene (2.00 g, 8.50 mmol)
in THF (60 mL) at -78 ◦C and the reaction mixture was allowed
to warm to room temperature. After four hours, the mixture was
cooled to -15 ◦C, and a solution of Me3SiCl (8.90 mmol) in THF
(20 mL) was slowly added. The reaction mixture was allowed to
warm to room temperature and stirred for 2 h. The solvent and
excess Me3SiCl were removed under reduced pressure. The residue
was extracted with toluene (30 mL) and slowly added to a solution
of TiCl4 (8.50 mmol) in 50 mL of toluene at -78 ◦C. The reaction
mixture was allowed to warm to room temperature and stirred for
24 h. The precipitate was filtered off and the solvent was removed
to leave a red solid. Recrystallization from methylene chloride/n-
hexane (1 : 3 in v/v) gave pure 1 (2.82 g, 78.2%). Anal. calcd for
C18H25Cl3SiTi (423.71): C 50.90, H 6.17. Found: C 50.71, H 6.10.
1H NMR (CDCl3, 300 MHz; 298 K): d 7.55 (d, J = 7.5 Hz, 2 H,
Ph), 7.47 (d, J = 8.1 Hz, 2 H, Ph), 2.27 (s, 6 H, Cp-Me), 2.03 (s,
6 H, Cp-Me), 0.31 (s, 9 H, Si-Me3). 13C NMR (CDCl3, 75 MHz;
298 K): d 142.7, 141.3, 138.4, 135.9, 133.9, 133.6, 123.0, 15.3,
14.2, -1.2.
Synthesis of 1-(4¢-isopropyl -phenyl)-2,3,4,5-tetramethyl-cy-
clopentadienyl-TiCl2(O-2,6-di-isopropyl-C6H3) (6). Complex 6
was synthesized in the same manner as complex 5 except
that 3.50 mmol of 1-(4¢-isopropylphenyl)-2,3,4,5-tetramethyl-
cyclopentadienyl titanium trichloride was used instead of 1-
(4¢-trimethylsilylphenyl)-2,3,4,5-tetramethyl-cyclopentadienyl ti-
tanium trichloride. Pure 6 (1.47 g, 78.5%) was obtained as red
crystals by recrystallization from methylene chloride/n-hexane
(1 : 3 in v/v). Anal. calcd for C30H40Cl2OTi (535.42): C 67.16, H
Synthesis of 1-(4¢-isopropylphenyl)-2,3,4,5-tetramethyl-cyclo-
pentadienyl titanium trichloride (2). Complex 2 was synthesized
in the same manner as complex 1 with 8.50 mmol of 1-(4¢-
isopropylphenyl)-2,3,4,5-tetramethyl-cyclopentadiene as starting
material. Pure 2 (2.60 g, 78.0%) was obtained as red crystals by
recrystallization from methylene chloride/n-hexane (1 : 3 in v/v).
Anal. calcd for C18H23Cl3Ti (393.61): C 54.78, H 6.13. Found: C
54.37, H 6.08. 1H NMR (CDCl3, 300 MHz; 298 K): d 7.22 (s, 4 H,
Ph), 2.88 (m, 1 H, iPr), 2.40 (s, 6 H, Cp-Me), 2.35 (s, 6 H, Cp-Me),
1.21 (d, J = 7.2 Hz, 6 H, iPr). 13C NMR (CDCl3, 75 MHz; 298 K):
d 149.4, 143.4, 138.7, 136.2, 130.3, 126.4, 33.9, 23.8, 15.5, 14.6.
1
7.70. Found: C 66.75, H 7.35. H NMR (CDCl3, 300 MHz; 298
K): d 7.42 (d, J = 8.1 Hz, 2 H, Ph), 7.25 (d, J = 8.1 Hz, 2 H, Ph),
6.99 (m, 3 H, Ph), 3.02 (m, 2 H, Ar-iPr), 2.93 (m, 1 H,iPr), 2.29
(s, 12 H, Cp-Me), 1.27 (d, J = 7.2 Hz, 12 H, Ar-iPr), 1.03 (d, J =
6.9 Hz, 6 H, iPr-Me).13C NMR (CDCl3, 75 MHz; 298 K): d 159.8,
148.7, 139.6, 137.2, 133.7, 130.7, 130.4, 130.2, 126.2, 123.5, 123.1,
33.9, 26.7, 23.9, 23.7, 13.9, 13.4.
Synthesis of 1-(4¢-methylphenyl)-2,3,4,5-tetramethyl-cyclo-
pentadienyl titanium trichloride (3). Complex 3 was synthesized
in the same manner as complex 1 with 8.50 mmol of 1-(4¢-
methylphenyl)-2, 3,4,5-tetramethyl-cyclopentadiene as starting
material. Pure 3 (2.36 g, 76.0%) was obtained as red crystals by
recrystallization from methylene chloride/n-hexane (1 : 3 in v/v).
Anal. calcd for C16H19Cl3Ti (365.55): C 52.57, H 5.24. Found: C
Synthesis of 1-(4¢-methyl-phenyl)-2,3,4,5-tetramethyl-cyclo-
pentadienyl-TiCl2(O-2,6-di-isopropyl-C6H3) (7). Complex
7
was synthesized in the same manner as complex 5 except
that 3.50 mmol of 1-(4¢-methyl-phenyl)-2,3,4,5-tetramethyl-
cyclopentadienyl titanium trichloride was used instead of
1-(4¢-trimethylsilylphenyl)-2,3,4,5-tetramethyl-cyclopentadienyl
titanium trichloride. Pure 7 (1.40 g, 79.1%) was obtained as red
crystals by recrystallization from methylene chloride/n-hexane
(1 : 3 in v/v). Anal. calcd for C28H36Cl2OTi (507.36): C 66.15, H
1
52.31, H 5.11. H NMR (CDCl3, 300 MHz; 298 K): d 7.26 (s,
4 H, Ph), 2.47 (s, 6 H, Cp-Me), 2.43 (s, 6 H, Cp-Me), 2.41 (s,
3 H, Ph-Me). 13C NMR (CDCl3, 75 MHz; 298 K): d 143.2, 138.7,
138.6, 136.1, 130.2, 130.1, 129.0, 21.3, 15.5, 14.6.
Synthesis of 1-(3¢,5¢-di-trifluoromethylphenyl)-2,3,4,5-tetra-
methyl-cyclopentadienyl titanium trichloride (4). Complex 4 was
synthesized in the same manner as complex 1 with 8.50 mmol
1
7.35. Found: C 65.27, H 7.18. H NMR (CDCl3, 300 MHz; 298
of
1-(3¢,
5¢-di-trifluoromethylphenyl)-2,3,4,5-tetramethyl-
K): d 7.41 (d, J = 8.1 Hz, 2 H, Ph), 7.23 (d, J = 8.1 Hz, 4 H, Ph),
7.02 (m, 3 H, Ph), 3.04 (m, 2 H, Ar-iPr), 2.39 (s, 3 H, Ar-Me),
2.30 (s, 6 H, Cp-Me), 2.27 (s, 6 H, Cp-Me), 1.05 (d, J = 7.2 Hz,
cyclopentadiene as starting material. Pure 4 (3.18 g, 76.9%)
was obtained as red crystals by recrystallization from methylene
2532 | Dalton Trans., 2010, 39, 2525–2535
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12 H, Ar-iPr). 13C NMR (CDCl3, 75 MHz; 298 K): d 159.8, 139.6,
137.9, 137.3, 133.3, 131.0, 130.4, 130.0, 128.9, 123.5, 123.1, 26.7,
23.7, 21.2, 13.9, 13.2.
Table 5 Crystal data and structure refinement for complexes 6, 7 and 8
6
7
8
Empirical
formula
Mw
C30H40Cl2OTi
C28H36Cl2OTi
507.37
Orthorhombic Monoclinic
Pbca
8.3715(17)
17.975(4)
36.081(7)
90
90
90
5429.6(19)
8
1.241
2144
0.529
47 290
6203
C29H32Cl2F6OTi
629.35
Synthesis of 1-(3¢,5¢-(CF3)2-phenyl)-2,3,4,5-tetramethyl-cyclo-
pentadienyl-TiCl2(O-2,6-di-isopropyl-C6H3) (8). Complex 8 was
535.42
Monoclinic
P21/c
22.757(5)
8.7719(18)
15.626(3)
90
103.38(3)
90
3034.7(11)
4
1.172
1136
0.477
22 357
5298
synthesized in the same manner as complex
5 except
Crystal system
Space group
Pc
that 3.50 mmol of 1-(3¢,5¢-(CF3)2-phenyl)-2,3,4,5-tetramethyl-
cyclopentadienyl titanium trichloride was used instead of 1-
(4¢-trimethylsilyl-phenyl)-2,3,4,5-tetramethyl-cyclopentadienyl ti-
tanium trichloride. Pure 8 (1.69 g, 76.8%) was obtained as red
crystals by recrystallization from methylene chloride/n-hexane
(1 : 3 in v/v). Anal. calcd for C29H32Cl2F6OTi (629.34): C 55.25, H
˚
a/A
12.1002 (17)
8.7661(12)
15.896(2)
90
111.918(3)
90
1564.2(4)
2
1.336
648
0.500
10 396
5719
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
3
˚
1
V/A
5.28. Found: C 54.91, H 5.12. H NMR (CDCl3, 300 MHz; 298
Z
K): d 8.05 (s, 2 H, Ph), 7.91 (s, 1 H, Ph), 6.97 (m, 3 H, Ph), 3.06
(m, 2 H, Ar-iPr), 2.32 (s, 6 H, Cp-Me), 2.28 (s, 6 H, Cp-Me), 1.07
(d, J = 6.9 Hz, 12 H, Ar-iPr). 13C NMR (CDCl3, 75 MHz; 298
K): d 159.8, 139.4, 135.2, 133.4, 132.0, 131.9, 131.5, 130.7, 124.1,
123.3, 121.7, 26.9, 23.6, 13.8, 13.0.
Dc/g cm-3
F(000)
m/mm-1
No. of reflections
No. of
independent
reflections
Rint
Synthesis of (3,3¢,5,5¢-tetra-isopropyl-4,4¢-biphenolate)-bi-[1-(4¢-
trimethylsilylphenyl)-2,3,4,5-tetramethyl-cyclopentadienyl-TiCl2 ]
(9). Complex 9 was synthesized in the same manner as complex
5 except that 1.90 mmol of 3,3¢,5,5¢-tetra-isopropyl-4,4¢-biphenol
was used instead of 2,6-bi-isopropylphenol. Pure 9 (1.43 g, 72.5%)
was obtained as red crystals by recrystallization from methylene
chloride/n-hexane (1 : 3 in v/v). Anal. calcd for C60H82Cl4O2Si2Ti2
0.0852
0.0659
0.0324
b
R1a/WR2
GOF
0.0543/0.1082 0.0447/0.1063 0.0439/0.1044
1.044
0.204, -0.287
1.037
0.226, -0.320
1.011
0.352, -0.258
Largest
diffraction peak
and hole/e A
-3
˚
ꢀ
ꢀ
ꢀ
ꢀ
a R1 = ꢀFo| - |Fcꢀ/ |Fo|. b wR2 = [ [w(Fo - Fc2)2]/ [w(Fo2)2]]1/2
.
2
1
(1129.02): C 63.70, H 7.49. Found: C 62.81, H 7.20. H NMR
(CDCl3, 300 MHz; 298 K): d 7.56 (d, J = 4.5 Hz, 4 H, Ph), 7.49
(d, J = 4.5 Hz, 4 H, Ph), 7.14 (s, 4 H, Ph), 3.05 (m, 4 H, Ar-iPr),
2.32 (s, 24 H, Cp-Me), 1.09 (d, J = 4.2 Hz, 24 H, Ar-iPr), 0.31 (s,
18 H, Si-Me). 13C NMR (CDCl3, 75 MHz; 298 K): d 159.7, 140.5,
139.8, 136.7, 136.4, 133.7, 133.1, 130.8, 129.6, 129.0, 121.6, 26.7,
23.7, 13.9, 13.3, -1.2.
position. All calculations were performed using the SHELXTL
crystallographic software packages.55 Details of the crystal data,
data collections, and structure refinements are summarized in
Table 5.
Synthesis of (3,3¢,5,5¢-tetra-isopropyl-4,4¢-biphenolate)-bi-[1-
(4¢-methylphenyl)-2,3,4,5-tetramethyl-cyclopentadienyl-TiCl2 ]
(10). Complex 10 was synthesized in the same manner as
complex 9 except that 3.50 mmol of 1-(4¢-methyl-phenyl)-
2,3,4,5-tetramethyl-cyclopentadienyl titanium trichloride was
used instead of 1-(4¢-trimethylsilylphenyl)-2,3,4,5-tetramethyl-
cyclopentadienyl titanium trichloride. Pure 10 (1.27 g, 71.8%)
was obtained as red crystals by recrystallization from methylene
chloride/n-hexane (1 : 3 in v/v). Anal. calcd for C56H70Cl4O2Ti2
Polymerization reactions
The propylene polymerization experiments were carried out as
follows: a dry 250 mL steel autoclave was charged with 60 mL of
toluene, thermostated at desired temperature and saturated with
1.0 bar of propylene. The polymerization reaction was started by
addition of a mixture of a catalyst and Al(iBu)3 in toluene (5 mL)
and a solution of Ph3CB(C6F5)4 in toluene (5 mL) at the same
time. The reaction mixture was stirred for 30 min under 5 bar
of propylene. The polymerization was then quenched by injecting
acidified methanol [HCl (3 M)/methanol = 1 : 1]. The polymer was
collected by filtration, washed with water and methanol, and dried
to a constant weight under vacuum. For the copolymerization
experiments, appropriate amounts of 1-hexene were added in
toluene.
1
(1012.70): C 66.25, H 7.15. Found: C 65.13, H 6.92. H NMR
(CDCl3, 300 MHz; 298 K): 7.47 (d, J = 5.1 Hz, 4 H, Ph), 7.30 (d,
J = 5.1 Hz, 4 H, Ph), 7.21 (s, 4 H, Ph), 3.14 (m, 4 H, Ar-iPr), 2.46
(s, 6 H, Ar-Me), 2.38 (s, 12 H, Cp-Me), 2.35 (s, 12 H, Cp-Me), 1.18
(d, J = 3.9 Hz, 24 H, Ar-iPr). 13C NMR (CDCl3, 75 MHz; 298
K): d 159.7, 139.8, 137.9, 137.3, 136.3, 133.3, 130.9, 130.4, 130.0,
128.9, 121.6, 26.9, 23.8, 21.2, 14.0, 13.2.
Acknowledgements
X-Ray structure determinations of 6, 7 and 8
This work was supported by the National Natural Science
Foundation of China (no. 20674024 and 20772044).
Crystals of 6, 7 and 8 suitable for X-ray structure determination
were obtained from a saturated solution of CH2Cl2–n-hexane (1 : 3,
v/v) at room temperature. The data were collected at 293 K on the
Rigaku RAXIS-RAPID diffractometer using Mo Ka radiation.
The structures were solved by direct methods54 and refined by full-
matrix least-squares on F2. All non-hydrogen atoms were refined
anisotropically and the hydrogen atoms were included in idealized
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