Synthesis and structures of adamantyl-substituted constrained geometry cyclopentadienyl-phenoxytitanium complexes and their catalytic properties for olefin polymerization

Article abstract of DOI:10.1016/j.jorganchem.2011.03.041

A number of new constrained geometry titanium complexes, [η⁵: η¹-2-C₅Me₄-4-R-6-Ad- C₆H₂O]TiCl₂ [Ad = adamantyl, R = Me (8), ^tBu (9)] and [η⁵: η¹-

Full text of DOI:10.1016/j.jorganchem.2011.03.041

Journal of Organometallic Chemistry 696 (2011) 2499e2506
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and structures of adamantyl-substituted constrained geometry
cyclopentadienylephenoxytitanium complexes and their catalytic properties for
olefin polymerization
*
Jincai Li, Wei Gao, Qiaolin Wu, Hongchun Li, Ying Mu
State Key Laboratory of Supramolecular Structure and Materials, School of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
A number of new constrained geometry titanium complexes, [h5 1-2-C5Me4-4-R-6-Ad-C6H2O]TiCl2
: h
Article history:
[Ad ¼ adamantyl, R ¼ Me (8), tBu (9)] and [h5
: h
1-C5H2Ph2-4-tBu-6-Ad-C6H2O]TiCl2 (10), were synthe-
Received 8 January 2011
Received in revised form
13 March 2011
sized from reactions of TiCl4 either directly with corresponding free ligands, 2-C5Me4H-4-R-6-Ad-
C6H2OH [R ¼ Me (5), tBu (6)], or with the dilithium salt of the free ligand 2-C5H3Ph2-4-tBu-6-Ad-C6H2OH
(7). These new titanium complexes were fully characterized by 1H and 13C NMR spectroscopy and
elemental analyses, and the molecular structures of 8 and 9 were determined by single-crystal X-ray
crystallography. Upon activation with AliBu3 and Ph3CB(C6F5)4 (TIBA/B), these complexes exhibit high
catalytic activity for 5-ethylidene-2-norbornene (ENB) polymerization as well as ethylene/1-hexene and
ethylene/ENB copolymerization with good tacticity-control ability for the ENB polymerization and high
comonomer incorporation ability for the copolymerization reactions. It was found that the bulky ada-
mantyl substituent at the ortho position of the phenoxy group in the ligands of these complexes
apparently influences the molecular weight and the microstructure of the resultant polymers.
Ó 2011 Elsevier B.V. All rights reserved.
Accepted 23 March 2011
Keywords:
Ethylene polymerization
Olefin polymerization
Metallocene
Titanium complex
1. Introduction
activity in ethylene/a-olefin copolymerization though they produce
copolymers with relatively low molecular weights due probably to
their ligands being not bulky enough [16e19]. In addition, this type
of catalysts were found to show good catalytic properties in the
copolymerization of ethylene with cyclo-olefins such as norbornene
or 5-ethylidene-2-norbornene (ENB) and produce copolymers with
relatively high molecular weights and comonomer incorporation
[29,30]. To further improve the catalytic property of this type of
catalysts, we have synthesized several new titanium complexes of
type II bearing a bulky adamantyl substituent at the ortho-position
of the phenoxy group in their ligands. It was found that these new
complexes, upon activation with AliBu3 and Ph3CB(C6F5)4 (TIBA/B),
exhibit higher catalytic activity and produce polymers with higher
molecular weights for ethylene/1-hexene (E/H) copolymerization,
and show better comonomer incorporation ability in E/ENB copo-
lymerization and higher tacticity-control ability in ENB polymeri-
zation than the known complexes of this type [30]. In this paper, we
wish to report the synthesis and structural characterization of the
In the last two decades, the so-called constrained geometry
metallocene catalysts (CGC) with the general formula of [h5 h1
: -
C5R4(SiMe2)NR1]TiCl2 (I in Chart 1) have been widely studied in
academic [1e4] and industrial [5e8] institutions because of their
high performance in catalyzing the copolymerization of different
olefins. Various modifications on the chelating ligands have been
made in order to improve the catalytic performance of the CGC
catalysts through steric and electronic effects of their ligands. For
example, a variety of CGC catalysts with ligands bearing different
substituted cyclopentadienyl, indenyl and fluorenyl groups [9e14],
different coordinating heteroatoms [15e25], and linkages [26e28]
have been synthesized and studied. In comparison with the CGC
catalysts of type I, the catalysts with a pendent oxygen donor on the
cyclopentadienyl ring received relatively less attention and have not
been studied systematically [3]. We and other groups have devel-
oped a number of CGC catalysts of the type [h5 1-C5Me4-ArO]TiCl2
: h
(II in Chart 1) and found that these catalysts show high catalytic
new titanium complexes, [h5 1-2-C5Me4-4-R-6-Ad-C6H2O]TiCl2
: h
: h
[Ad ¼ adamantyl, R ¼ Me (8), tBu (9)] and [h5 1-2-C5H2Ph2-4-tBu-
6-Ad-C6H2O]TiCl2 (10), as well as the results from the ENB poly-
merization, the E/H and E/ENB copolymerization catalyzed by these
complexes in the presence of AliBu3 and Ph3CB(C6F5)4.
* Corresponding author. Tel.: þ86 431 85168376; fax: þ86 431 85193421.
E-mail address: ymu@jlu.edu.cn (Y. Mu).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.03.041

2500
J. Li et al. / Journal of Organometallic Chemistry 696 (2011) 2499e2506
Ph
R
R
Ph
Ph
OH
R
O
R
R
Ad
Br
2 eq. BuLi
Et2O
H+3O
R
Ph
R1
R
R
Ti
Cl
Cl
toluene
Si
Cl
Cl
OH
Ti
Ad
Ad= admannyl
N
O
7
R2
R1
Ph
1. 2 eq. BuLi
2. TiCl4 in tolene
Ph
Cl
II
I
Ti
O
Cl
Chart 1.
Ad
10
Scheme 2. Synthetic route of complex 10.
2. Results and discussion
2.1. Synthesis of ligands and titanium complexes
elemental analyses. The 1H and 13C NMR spectra of 8e10 indicate
that they all have Cs-symmetric structures in solution.
The synthetic routes to complexes 8, 9 and 10 are shown in
Schemes 1 and 2, respectively. Reaction of 1-bromoadamantane with
1 equivalent of corresponding phenol catalyzed by AlCl3 in octane at
refluxing temperature gives 2-adamantyl-4-alkylphenol (1, or 2) in
45e55% yields. Under similar conditions, compound 2 was synthe-
sized in higher yields than compound 1. Treatment of compound 1 or
2 with 1.05 equivalent of Br2 in chloroform at 0 ꢀC produces 2-bromo-
4-alkyl-6-adamantylphenol (3 or 4) in about 90% yields. Following
previously reported procedures [17,18], free ligands 5 and 6 were
synthesized in relatively high yields (45e50%) by the reaction of
tetramethylcyclopentenone with the corresponding dilithium
phenoxide, while ligand 7 was synthesized in low yields (35e40%)
with diphenylcyclopentenone, instead of tetramethylcyclopente-
none, as the starting material. Compounds 1e7 were all characterized
by 1H NMR and elemental analyses.
Titanium complexes 8 and 9 were synthesized in high yields
(80e90%) by the direct HCl elimination reaction between TiCl4 and
a corresponding free ligand (5 or 6) in the way reported previously
[16]. This synthetic method was found to work much better for the
synthesis of complexes of this type in comparison to other
synthetic approaches such as amine elimination [31e33], alkane
elimination [34,35], and Me3SiCl elimination reactions [36e38].
However, attempts to synthesize complex 10 by this method were
unsuccessful due probably to that the coordination of the phenyl
groups on the cyclopentadiene ring of the free ligand 7 reduces the
chance for the cyclopentadiene ring to coordinate to the titanium
atom and therefore makes the HCl elimination reaction between
TCl4 and the cyclopentadiene ring difficult. The Me3SiCl elimination
reaction was also found to be inefficient for the synthesis of
complex 10. Finally, complex 10 was synthesized by the traditional
lithium salt elimination reaction as shown in Scheme 2. All three
titanium complexes 8e10 were characterized by 1H, 13C NMR and
2.2. Crystal structures of 8 and 9
The molecular structures of complexes 8 and 9 were further
confirmed by single-crystal X-ray analysis. The ORTEP drawings of
the molecular structures of 8 and 9 are shown in Figs. 1 and 2,
respectively. The selected bond lengths and angles are summarized
in Table 1. The general structural features of 8 and 9 are comparable
to those previously reported for complexes I and II. Both molecules
possess Cs-symmetry with a distorted octahedral coordination
environment in their solid state structures and adopt a three-
legged piano stool geometry with the phenoxy O atom and the
two Cl atoms being the three legs and the Cp ring being the seat.
The Cp(cent)eTieO angles for 8 and 9 are 106.5ꢀ, 106.7ꢀ, respec-
tively, which are slightly smaller than those of known complexes II
(106.8e107.3ꢀ) [17] and that of the Cp(cent)eTieN angle in
complex [h5 1-C5Me4(SiMe2)NtBu]TiCl2 (107.6ꢀ) [15], indicating
: h
that complexes 8 and 9, as potential olefin copolymerization cata-
lyst precursors, possess similar sterically open features to
complexes I and known complexes II. The C(Cp)eC(phenolate)
vector is bent 11.9ꢀ in 8 and 11.0ꢀ in 9 from the Cp ring plane, being
similar to those for the known complexes II (9.9e11.3ꢀ) [17] and
reflecting similar steric strain in these complexes in the solid state.
ꢀ
ꢀ
The TieC(Cp) (av) distances of 2.011 A in 8 and 2.007 A in 9 are
OH
OH
R
OH
R
Ad
Br
Ad
1. 2eq.BuLi
AdBr/AlCl3
Br2
octane, reflux
CHCl3, 0°C
O
2.
R
R
Ti
R
Cl
Cl
H+3O
TiCl4 / toluene
- HCl
O
OH
Ad
Ad
R = Me (8), tBu (9)
R = Me (5), tBu (6)
Ad = admannyl
Fig. 1. Structure of complex 8 (thermal ellipsoids are drawn at the 30% probability
Scheme 1. Synthetic route of complexes 8 and 9.
level).

J. Li et al. / Journal of Organometallic Chemistry 696 (2011) 2499e2506
2501
Table 2
Results of ethylene/1-hexene copolymerization with 8e11/AliBu3/Ph3CB(C6F5)4
systems.a
Tempb
(ꢀC)
1-Hexenec
(mol/L)
Activityd
Incorpe
(mol%)
Mw
PDIf
f
Run
Cat
(ꢁ103)
(ꢁ103)
1
2
3
4
5
6
7
8
9
10
8
9
9
9
9
9
9
10
11
11
70
70
70
70
70
50
90
70
70
70
0.3
0.2
0.3
0.4
0.5
0.3
0.3
0.3
0.3
0.5
13.3
15.1
16.6
18.2
16.8
11.7
12.4
9.5
7.8
5.1
7.6
10.3
12.6
7.3
7.8
8.5
7.7
12.4
17
18
17
15
13
20
13
9
2.3
2.4
2.3
2.5
2.4
2.4
2.5
2.3
2.6
2.4
12.8
11.9
14
10
a
Reaction conditions: ethylene pressure, 5 atm; catalyst, 1
mmol; toluene þ 1-
hexene total, 80 mL; molar ratio of Al/Ti, 120; molar ratio of B/Ti, 1.5; polymeriza-
tion time, 10 min.
b
Polymerization temperature.
Concentration of 1-hexene in feed.
c
d
Activity in kg polymer/(mol Ti h).
e
Determined by 13C NMR.
f
Determined by GPC, Mw in g/mol.
Fig. 2. Structure of complex 9 (thermal ellipsoids are drawn at the 30% probability
level).
stericeffectof the ligands in thesecomplexes on theircatalytic activity
can be obviously observed by comparing the catalytic activity of 8, 9
and 11. Adequately bulky ligand would weaken the interaction
between the cationic catalyst and the anionic cocatalyst [16,35],
therefore could favor the coordination of the olefins and increase the
catalytic activity of the catalyst. Similar results have previously been
observed forethylene/1-hexene copolymerization reactionwith other
half-metallocene titanium(IV) catalyst systems [19,40,41]. With 9/
TIBA/B catalyst system, copolymerization experiments with different
1-hexene feed concentrations were carried out and obvious como-
nomer effect was observed. In addition, copolymerization reactions at
different temperatures were also examined and the reaction at 70 ꢀC
shows the highest catalytic activity. The comonomer content of the
obtained poly(ethylene-co-1-hexene)s was calculated based on 13C
NMR analysis [42], and the molecular weight of the poly(ethylene-co-
1-hexene)s was measured by GPC. It can be seen from the comonomer
content data that the Ph2Cp based complex 10 shows slightly higher
comonomer incorporation ability than the Me4Cp based complexes 8,
9 and 11 under similar conditions. GPC analysis reveals that the
poly(ethylene-co-1-hexene)s produced by the adamantyl-substituted
catalysts 8 and 9 possess relatively high molecular weight in
comparison tothe ones formed from the tert-butylsubstitutedcatalyst
11. The molecular weight distribution is basically unimodal and
narrow, being characteristic for metallocene polyolefins.
obviously shorter than those in the known complexes II
ꢀ
ꢀ
(2.335e2.348 A) [17], and the TieO bond lengths of 1.822(2) A in 8
ꢀ
and 1.823(2) A in 9 are also shorter than those in the known
ꢀ
complexes II (1.832e1.837 A) [17], which is indicative of good
stability of complexes 8 and 9 in comparison with their analogues.
2.3. Copolymerization of ethylene with 1-hexene
Copolymerization of ethylene with 1-hexene using complexes
8e10 as catalysts, activated with AliBu3 and Ph3CB(C6F5)4, was
explored. For comparison purpose, the catalytic property of a known
complex [h5 1-2-C5Me4-4,6-tBu2C6H2O]TiCl2 (11) was also exam-
: h
ined. The copolymerization results are summarized in Table 2. The
catalytic activity of these catalysts for the ethylene/1-hexene copoly-
merization under similar conditions changes in the order of
9 > 8 > 11 >10. The catalytic activity of the 10/TIBA/B catalyst system
is obviously lower than other catalyst systems under similar condi-
tions, which should be attributed to the weaker electron-donating
ability of the Ph2Cp ring in 10 comparing to the Me4Cp ring in other
complexes. It is well known for metallocene catalysts that electron-
donating groups on the Cp ring would increase the catalytic activity
of the catalyst [39]. Except for the electronic effect discussed above,
Table 1
Selected bond lengths and angles for complexes 8 and 9.
2.4. ENB polymerization
Complex 8
Ti(1)eC(1)
Ti(1)eC(2)
Ti(1)eC(3)
Ti(1)eO(1)
Cl(1)eTi(1)eO(1)
Cl(1)eTi(1)eCl(2)
O(1)eC(11)
TieC(Cp) (av)
C(6)eC(1)eCp(cent)
2.305(3)
2.309(3)
2.357(3)
1.822(2)
103.95(6)
104.37(4)
1.383(3)
2.011
Ti(1)eC(4)
Ti(1)eC(5)
Ti(1)eCl(1)
Ti(1)eCl(2)
Cl(2)eTi(1)eO(1)
Ti(1)eO(1)eC(11)
C(1)eTi(1)eO(1)
Cp(cent)eTieO
2.380(3)
2.371(1)
2.245(1)
2.259(1)
104.59(7)
125.6
ENB polymerization reactions catalyzed by the 8e10/TIBA/B
catalyst systems were studied in detail and the results are summa-
rized in Table 3. For comparison purpose, polymerization reaction
with
a
known
nonbridged
(2,6-diisopropyphenox-
y)(pentamethylcyclopentadienyl)titanium dichloride complex
[C5Me5][2,6-iPr2C6H2O]TiCl2 (12) [43,44] as catalyst was also
examined. The effects of the polymerization temperature and initial
ENB concentration on the polymerization reaction were examined
with 9/TIBA/B catalyst system. The catalytic activity, together with
the polymer yield and ENB conversion, increases with the elevation
in polymerization temperature and reaches their maximum values
at about 70 ꢀC. The intrinsic viscosity of the obtained poly(5-
ethylidene-2-norbornene) (PENB) decreases with the increase in
polymerization temperature, indicating that the molecular weight
of the PENB decreases with the elevation in polymerization
temperature. The catalytic activity increases with the increase in
75.42
106.5
11.9
Complex 9
Ti(1)eC(1)
Ti(1)eC(2)
Ti(1)eC(3)
2.298(2)
2.331(2)
2.384(2)
1.823(2)
106.31(7)
105.13(4)
1.367(3)
2.007
Ti(1)eC(4)
Ti(1)eC(5)
Ti(1)eCl(1)
Ti(1)eCl(2)
Cl(2)eTi(1)eO(1)
Ti(1)eO(1)eC(11)
C(1)eTi(1)eO(1)
Cp(cent)eTieO
2.369(2)
2.323(2)
2.268(1)
2.276(1)
104.12(6)
129.17(13)
75.17(8)
106.7
Ti(1)eO(1)
Cl(1)eTi(1)eO(1)
Cl(1)eTi(1)eCl(2)
O(1)eC(11)
TieC(Cp) (av)
C(10)eC(1)eCp(cent)
11.0

2502
J. Li et al. / Journal of Organometallic Chemistry 696 (2011) 2499e2506
Table 3
can be observed over the region of 4.9e5.8 ppm for the sample
produced by catalyst 11 as shown in Fig. 3(c), while the resonances
between5.5and5.8 ppmcanhardlybeobservedinFig. 3(a) and (b) for
the samples made with catalyst 9. The sample obtained with catalyst
12 shows further difference in the proton resonances in this region
with stronger signals between 5.5 and 5.8 ppm and narrow signals
between 5.0 and 5.2 ppm. These results indicate the difference in
microstructure of the PENB samples obtained from different catalyst
systems. Even only the major one of the two ENB isomers is consid-
ered, there should be three types of triads (as shown in Fig. 4) and ten
types of pentads in the PENB polymer chain. It has been known that
the Cs-symmetry constrained geometry (tBuNSiMe2Flu)TiMe2/MAO
catalyst system catalyzes the ethylene/norbornene copolymerization
to produce racemo-NN sequence enriched copolymer (racemo-NN
sequence/meso-NN sequence ¼ 11) [45]. On the basis of the above 1H
NMR results, it should be reasonable to suppose that the similar
Cs-symmetry catalyst 9 may produce racemo-ENBeENB sequence
enriched PENB with more RR triads (4.9e5.4 ppm) in the polymer
chain, while the less bulky catalyst 11, and especially the flexible
nonbridged catalyst 12 may produce PENB with more meso-ENBeENB
sequence and thus more RM and MM triads (5.5e5.8 ppm) in the
polymer chain. 13C NMR spectra of the PENB samples give little
information on the microstructure of the polymer chain.
Results of ENB homopolymerization with 8e12/AliBu3/Ph3CB(C6F5)4 systems.a
Run
Cat.
Tempb
(ꢀC)
ENBc
(mol/L)
Yield
(g)
Activityd
Conversion
(%)
h
e (dL/g)
(ꢁ103)
1
2
3
4
5
6
7
8
9
9
9
9
9
9
10
11
12
70
30
50
70
90
70
70
70
70
70
1.0
1.0
1.0
1.0
1.0
2.0
3.0
1.0
1.0
1.0
0.47
0.49
0.58
0.73
0.67
1.41
1.85
0.39
0.70
0.29
78
82
97
121
112
235
308
65
7.8
8.1
9.6
12.1
11.1
11.7
10.2
6.5
0.30
0.35
0.33
0.31
0.28
0.45
0.62
0.28
0.27
0.42
8
9f
10
116
48
11.6
4.8
a
Reaction conditions: catalyst, 2 mmol; molar ratio of Al/Ti, 150; molar ratio of
B/Ti, 1.5; toluene þ ENB total, 50 mL; polymerization time, 3 h.
b
c
d
e
f
Polymerization temperature.
Initial ENB concentration.
Activity in kg polymer/(mol Ti h).
Intrinsic viscosity measured at 135 ꢀC in decahydronaphthalene.
Cited from reference [30].
initial ENB concentration. In addition, the increase in the initial ENB
concentration results in an increase in the yield and intrinsic
viscosity of the PENB. These results are similar to those observed in
the ENB polymerization with 11/TIBA/B catalyst system [30]. As
observed for the ethylene/1-hexene copolymerization, the catalytic
activity of the 10/TIBA/B catalyst system is obviously lower than that
of 8 and 9/TIBA/B catalyst systems under similar conditions. In
comparison with the results reported in literature for the con-
strained geometry (tBuNSiMe2Flu)TiMe2/MAO catalyst system [45],
the catalytic activity of the 8e10/TIBA/B catalyst systems for the ENB
polymerization is relatively high even at lower polymerization
temperature.
2.5. Copolymerization of ethylene with ENB
The copolymerization of ethylene with ENB catalyzed by the
8e10/TIBA/B catalyst systems under different conditions was
investigated. The results, together with those from 11/TIBA/B catalyst
system [30], are summarized in Table 4. As seen above for the
ethylene/1-hexene copolymerization and the ENB polymerization,
the catalytic activity of 8 and 9/TIBA/B catalyst systems is higher than
that of 10/TIBA/B catalyst system under the same conditions. The
influence of Al/Ti molar ratio on the catalytic activity was examined
in the range of 60e150. Maximum catalytic activity was obtained at
the Al/Ti molar ratio about 120. The influence of the initial ENB
concentration on the E/ENB copolymerization was also examined.
For all of these catalyst systems, “comonomer effect” on the catalytic
activity was observed with the catalytic activity increasing first and
decreasing then after reaching a maximum value as the initial ENB
concentration increases from 0.8 to 1.4 mol/L. The content of ENB in
the poly(E-co-ENB) was calculated based on the 1H NMR spectra
according to the following equation [30,45]:
1H NMR spectra of several typical PENB samples from different
reactions are shown in Fig. 3. In these 1H NMR spectra, obvious
differences can be seen in the region of 5.5e6.2 ppm. According to
literatures [30,45],theresonancesbetween6.0and6.2 ppmareforthe
protons of the endocyclic double bond and the resonances between
4.9 and 5.8 ppm are for the double bond protons of the ethylidene
group. The 1H NMR spectra of these PENB samples show that ENB is
polymerized regioselectively by the 8e10/TIBA/B catalyst systems
through the endocyclic double bond with the ethylidene group
unreacted [45e47]. The signals of the ethylidene double bond protons
A
ENB ðmol%Þ ¼
A þ 1=4ðB ꢂ 11AÞ
where A is the integral of ethylidene hydrogen signals in the range
from 4.8 to 5.3 ppm and B is the integral over all other hydrogen
signals from 0.5 to 3.0 ppm. It can be seen from the results in
Table 4 that the content of ENB in the poly(E-co-ENB)s produced
with 8e10/TIBA/B catalyst systems is higher than that in the
polymer made with 11/TIBA/B catalyst system under the same
conditions.
The GPC analysis reveals that the obtained poly(E-co-ENB)
samples possess moderate molecular weights withnarrow molecular
S
R
S
R
S
R
S
R
S
R
S
R
S
R
S
R
R
S
meso, meso triad (MM)
racemic, racemic triad (RR)
racenic, meso triad (RM)
Fig. 3. 1H NMR spectra of typical PENB samples from (a) run 2, (b) run 4, (c) run 9 and
(d) run 10 in Table 3 (recorded in CDCl3 at room temperature).
Fig. 4. Possible microstructures of the PENB triads.

J. Li et al. / Journal of Organometallic Chemistry 696 (2011) 2499e2506
2503
Table 4
and n-octane were dried and distilled under nitrogen in the presence
of sodium and benzophenone. CH2Cl2, 1-hexene and ENB were dried
over calcium hydride and distilled or filtered before use. Polymeri-
zation grade ethylene was further purified by passage through
columns of 5 A molecular sieves and MnO. nBuLi, AliBu3 and 5-eth-
ylidene-2-norbornene were purchased from Aldrich or Acros. 3,4-
Diphenyl-2-cyclopentenone [53] and Ph3CB(C6F5)4 [54e56] were
synthesized according to literature procedures. Other chemical
reagents are all commercial available and were used as received. The
Results of E/ENB copolymerization with 8e11/AliBu3/Ph3CB(C6F5)4 systems.a
Run Cat. Al/Tib ENBc
(mol/L) (g)
1.0 0.094
Yield Activityd ENBe
Mw
PDIf Tg
f
g
(ꢁ103)
content (ꢁ103)
1
2
3
4
5
6
7
8
9
9
9
9
9
9
9
9
9
8
8
8
8
8
8
60
90
188
680
n.d.h
n.d.
91
86
79
2.4 177.8
2.3 176.3
2.2 170.3
2.2 173.4
1.0
1.0
1.0
0.4
0.6
0.8
1.2
1.4
0.4
0.6
0.8
1.0
1.2
1.4
0.4
0.6
0.8
1.0
1.2
1.4
0.8
1.4
0.34
0.81
0.66
0.41
0.54
0.67
0.75
0.64
0.35
0.49
0.62
0.74
0.71
0.62
0.29
0.38
0.45
0.51
0.47
0.43
0.53
0.66
120
150
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
1620
1320
820
1080
1340
1500
1280
700
64.6
n.d.
33.1
45.2
55.8
72.9
78.6
32.6
44.8
56.4
65.3
72.2
77.9
30.7
41.3
49.6
56.5
62.4
67.9
41.3
50.5
73
175
139
108
53
2.3
99.5
2.3 131.3
2.2 150.6
2.3 179.8
2.2 203.9
elemental analyses were performed on
a Perkin-Elmer 2400
analyzer. 1H and 13C NMR spectra were measured on either a Bruker
Avance-500 or a Varian Mercury-300 NMR spectrometer. 13C NMR
spectra of the copolymers were recorded on a Varian Unity-400
NMR spectrometer at 125 ꢀC with o-C6D4Cl2 as the solvent. The
intrinsic viscosity of the PENB samples was measured in decahy-
dronaphthalene at 135 ꢀC with an Ubbelohde viscometer. Molecular
weight and Molecular weight distribution of the copolymer samples
were measured on a PL-GPC 220 at 140 ꢀC with 1,2,4-trichlobenzene
as the solvent. The melting transition temperature of the polymers
was measured by differential scanning calorimetry (DSC) on
a NETZSCH DSC 204 at a heating/cooling rate of 10 ꢀC/min and the
data from the second heating scan were used.
9
32
10
11
12
13
14
15
16
17
18
19
20
21
22
23
184
141
106
77
52
31
169
138
115
102
72
48
135
105
2.4
97.4
980
2.3 130.8
2.3 152.8
2.2 171.9
2.2 180.6
2.2 199.8
1240
1480
1420
1220
580
760
900
1020
940
860
10
10
10
10
10
10
2.5
93.9
2.3 121.6
2.3 141.5
2.2 151.3
2.2 165.1
2.2 173.7
2.0 134.6
2.1 171.9
11i 120
11i 120
1060
1320
a
3.2. Synthesis of 2-adamantyl-4-methylphenol (1)
Reaction conditions: ethylene pressure 1 atm; catalyst, 1
m
mol; toluene þ ENB
total 50 mL, molar ratio of B/Ti 1.5, polymerization time 0.5 h, polymerization
temperature, 70 ꢀC.
In a dried flask, p-cresol (2.142 g, 19.8 mmol), 1-bromoada-
mantane (4.260 g, 19.8 mmol), AlCl3 (1.60 g, 12.0 mmol), and
n-octane (60 mL) were mixed under nitrogen at room temperature.
The mixture was heated to boiling and stirred for 3 days. After the
reaction mixture was cooled to room temperature, the reaction was
quenched with 6 N HCl solution (60 mL). After the mixture was
vigorously shaken, the organic phase was separated and dried over
anhydrous MgSO4. Removal of the solvent on a rotary evaporator
left a residue, which was purified by column chromatography on
silica gel eluting with hexanes/ethyl acetate (v/v, 30:1) to give
b
Molar ratio of Al/Ti.
Initial ENB concentration.
c
d
Activity in kg polymer/(mol Ti h).
e
Determined by 1H NMR spectroscopy (mol%).
f
Determined by GPC, Mw in g/mol.
Determined by DSC.
g
h
n.d. ¼ not determined.
i
Cited from reference [30].
weight distribution, suggesting that the polymerization reaction
takes place at a single site catalyst [48]. The Tg values of the poly(E-co-
ENB) samples determined by DSC increase with the increase in the
comonomer content, which is similar to the reported results for
poly(ethylene-co-norbornene)s [29,49] and poly(ethylene-co-ENB)s
[30,43,44,50e52].
a white solid (2.288 g, 9.44 mmol, 47.6%). Anal. Calcd for C17H22
(242.36): C, 84.25; H, 9.15. Found: C, 84.19; H, 9.10. 1H NMR (CDCl3,
300 MHz, 298 K): 6.992 (s, 1H, ArH), 6.841 (d, 1H, ArH), 6.530
O
d
(d, 1H, ArH), 4.560 (br, 1H, OH), 2.253 (s, 3H, CH3), 2.102 (br, 6H,
AdH), 2.059 (br, 3H, AdH), 1.760 (br, 6H, AdH).
2.6. Conclusions
3.3. Synthesis of 2-adamantyl-4-tert-butylphenol (2)
A number of new constrained geometry titanium complexes,
Compound 2 was prepared in the same way as described above
for 1 with 4-tert-butylphenol (2.974 g, 19.8 mmol) as starting
material. Pure product (3.072 g, 10.8 mmol, 54.5%) was obtained as
white crystalline material. Anal. Calcd for C20H28O (284.44):
C, 84.45; H, 9.92. Found: C, 84.41; H, 9.87. 1H NMR (CDCl3, 300 MHz,
[
h5 1-2-C5Me4-4-R-6-Ad-C6H2O]TiCl2 (8e10), have been synthe-
: h
sized. These new complexes were characterized by 1H and 13C NMR
spectroscopy and elemental analyses, and the molecular structures of
8 and 9 were determined by single-crystal X-ray crystallography.
Upon activation with AliBu3 and Ph3CB(C6F5)4, these complexes
exhibitgoodcatalyticactivityfortheethylene/1-haxeneandethylene/
ENB copolymerization reactions as well as the ENB polymerization
reaction, with the catalytic activity changes in the order of 9 > 8 > 10
under similar conditions. The introduction of the bulky adamantyl
substituenttotheorthopositionof thephenoxygroupintheligandsof
these complexes apparently influences the molecular weight and
microstructure of the resultant polymers, as well as the comonomer
incorporation ability in the copolymerization of ethylene with ENB.
298 K):
d 7.230 (s, 1H, ArH), 7.069 (d, 1H, ArH), 6.592 (d, 1H, ArH),
4.590 (br,1H, OH), 2.087 (br, 6H, AdH), 2.053 (br, 3H, AdH),1.786 (br,
6H, AdH), 1.301 (s, 9H, tBu).
3.4. Synthesis of 2-bromo-4-methyl-6-adamantylphenol (3)
A solution of Br2 (0.65 mL, 13 mmol) in chloroform (10 mL) was
added dropwise to a solution of 1 (2.957 g, 12.2 mmol) in 20 mL of
chloroform at 0 ꢀC during a period of 3 h. The mixture was stirred
for another 3 h at this temperature, and then a solution of NaHSO3
(0.1 g) in 15 mL H2O was added. The mixture was stirred for 30 min
and the organic layer was separated and dried over MgSO4.
Removal of the solvent on a rotary evaporator gave the crude
product, which was washed with pet ether to give the pure product
(3.566 g, 11.1 mmol, 91.0%) as white crystalline material. Anal. Calcd
for C17H21BrO (321.25): C, 63.56; H, 6.59. Found: C, 63.52; H, 6.53.
3. Experimental section
3.1. General comments
Manipulations with organometallic reagents were carried out
under a nitrogen atmosphere (ultrahigh purity) using standard
Schlenk or glove box techniques. Toluene, diethyl ether, n-hexane,
1H NMR (CDCl3, 300 MHz, 298 K):
d 7.128 (s, 1H, ArH), 6.929 (s, 1H,

2504
J. Li et al. / Journal of Organometallic Chemistry 696 (2011) 2499e2506
ArH), 5.605 (s, 1H, OH), 2.230 (s, 3H, CH3), 2.077 (br, 6H, AdH), 2.054
(br, 3H, AdH), 1.749 (br, 6H, AdH).
298 K): d 7.33e7.45 (m, 4H, ArH), 7.17e7.27 (m, 8H, ArH), 5.575 (s,
1H, OH), 3.951 (s, 2H, CpH), 2.322 (br, 6H, AdH), 2.154 (br, 3H, AdH),
t
1.863 (s, 6H, AdH), 1.225 (s, 9H, Bu).
3.5. Synthesis of 2-bromo-4-tert-butyl-6-adamantylphenol (4)
3.9. Synthesis of [h5 1-2-C5Me4-4-Me-6-Ad-C6H2O]TiCl2 (8)
: h
Compound 4 was prepared in the same way as described above
for 3 with 2 (2.825 g, 9.93 mmol) as starting material. Pure product
(3.324 g, 9.15 mmol, 92.1%) was obtained as white crystalline
material. Anal. Calcd for C20H27BrO (363.33): C, 66.12; H, 7.49.
A solution of 5 (0.550 g, 1.52 mmol) in toluene (15 mL) was
slowly added to a solution of TiCl4 (1.52 mmol) in toluene (30 mL)
at room temperature. The mixture was stirred at 60 ꢀC overnight.
The precipitate was filtered off, and the solvent was removed to
leave the crude product. Pure product (0.614 g, 1.28 mmol, 84.2%)
was obtained as red crystals by recrystallization from CH2Cl2/
hexane (v/v 1:3). Anal. Calcd for C26H32Cl2OTi (479.30): C, 65.15; H,
6.73. Found: C, 64.92; H, 6.87. 1H NMR (300 MHz, CDCl3, 298 K):
Found: C, 66.06; H, 7.44. 1H NMR (CDCl3, 300 MHz, 298 K):
d 7.317
(s, 1H, ArH), 7.188 (s, 1H, ArH), 5.650 (s, 1H, OH), 2.135 (br, 6H, AdH),
t
2.080 (br, 3H, AdH), 1.778 (br, 6H, AdH), 1.283 (s, 9H, Bu).
3.6. Synthesis of 2-(tetramethylcyclopentadienyl)-4-methyl-6-
adamantylphenol (5)
d
7.064 (s, 1H, ArH), 6.914 (s, 1H, ArH), 2.414 (s, 6H, C5Me4), 2.396(s,
3H, CH3), 2.050 (br, 6H, AdH), 2.031 (s, 6H, C5Me4), 2.028 (br, 3H,
AdH),1.753 (br, 6H, AdH). 13C NMR (CDCl3, 75 MHz, 298 K):
172.65,
A solution of 3 (3.100 g, 9.65 mmol) in Et2O (20 mL) was slowly
d
n
added to a solution of BuLi (21 mmol) in Et2O (20 mL) at ꢂ15 ꢀC.
145.10, 142.96, 136.56, 133.43, 129.99, 129.81, 126.80, 41.17, 37.35,
37.15, 29.29, 21.26, 13.27, 12.68.
The mixture was slowly warmed to room temperature and stirred
for 5 h. To the solution was slowly added 2,3,4,5-tetramethylcy-
clopentenone (1.45 mL, 9.65 mmol) in Et2O (10 mL) at 0 ꢀC. The
resulting solution was then allowed to warm to room temperature
and stirred overnight. The reaction mixture was hydrolyzed with
20 mL of concentrated HCl, and the organic layer was separated,
washed three times with water (50 mL) and dried over MgSO4.
Removal of the solvent on a rotary evaporator left a brownish oil.
Pure product (1.603 g, 4.42 mmol, 45.8%) was obtained by column
chromatography over silica (hexanes/CH2Cl2, 9:1) as a yellow
crystalline material. Anal. Calcd for C26H34O (362.55): C, 86.13; H,
9.45. Found: C, 86.09; H, 9.41. 1H NMR (CDCl3, 300 MHz, 298 K):
3.10. Synthesis of [h5 1-2-C5Me4-4-tBu-6-Ad-C6H2O]TiCl2 (9)
: h
Complex 9 was synthesized in the same way as described above
for complex 8 with compound 6 (0.611 g, 1.51 mmol) and TiCl4
(1.51 mmol) as starting material. Pure product (0.692 g, 1.35 mmol,
89.4%) was obtained as red crystals. Anal. Calcd for C29H38Cl2OTi
(521.38): C, 66.81; H, 7.35. Found: C, 66.72; H, 7.43. 1H NMR (CDCl3,
300 MHz, 298 K):
d 7.579 (d, 1H, ArH), 7.177 (d, 1H, ArH), 2.342 (br,
6H, AdH), 2.123 (s, 6H, C5Me4), 2.065 (br, 3H, AdH), 1.934 (s, 6H,
C5Me4), 1.833, 1.732 (dd, br, 6H, AdH), 1.439 (s, 9H, Bu). 13C NMR
t
d
6.802 (s, 1H, ArH), 6.778 (s, 1H, ArH), 3.054 (s, 1H, OH), 2.576 (q,
(CDCl3, 75 MHz, 298 K): d 172.43, 146.99, 145.24, 143.33, 136.04,
1H, CpH), 2.239 (s, 3H, CH3), 2.019 (br, 9H, AdH), 1.734 (br, 6H, AdH),
1.623 (s, 3H, C5Me4), 1.537 (s, 3H, C5Me4), 1.519 (s, 3H, C5Me4), 1.166
(d, 3H, C5Me4) ppm.
129.98, 129.58, 123.69, 123.11, 41.26, 37.70, 37.14, 34.91, 31.88, 29.30,
13.35, 12.73.
3.11. Synthesis of [h5 1-2-Ph2C5H2-4-tBu-6-Ad-C6H2O]TiCl2 (10)
: h
3.7. Synthesis of 2-(tetramethylcyclopentadienyl)-4-tert-butyl-6-
adamantylphenol (6)
A solution of nBuLi (4.0 mmol) in Et2O (10 ml) was slowly added
to a solution of 7 (1.001 g, 2.00 mmol) in Et2O (20 mL) at ꢂ20 ꢀC.
The reaction mixture was allowed to warm to room temperature
and stirred for 5 h. After the solvent was removed, the residue was
washed with hexanes and redissolved in toluene (25 mL). To the
solution was dropwise added a solution of TiCl4 (2.0 mmol) in
toluene (15 mL) at ꢂ40 ꢀC. The reaction mixture was allowed to
warm slowly to room temperature and stirred overnight. The
precipitate was filtered off, and the solvent was removed to leave
a red solid. Recrystallization from CH2Cl2/hexane (1:3) gave pure 10
as red crystals (0.561 g, 0.908 mmol, 45.4%), Anal. Calcd for
C37H38Cl2OTi (617.47): C, 71.97; H, 6.20. Found: C, 71.74; H, 6.37. 1H
Compound 6 was prepared in the same way as described above
for 5 with compound 4 (1.360 g, 3.74 mmol) as starting material.
Pure product (0.725 g, 1.79 mmol, 47.9%) was obtained as a white
crystal. Anal. Calcd for C29H40O (404.63): C, 86.08; H, 9.96. Found:
C, 85.93; H, 9.92. 1H NMR (CDCl3, 300 MHz, 298 K):
d 7.037 (s, 1H,
ArH), 7.019 (s, 1H, ArH), 3.102 (s, 1H, OH), 2.373 (q, 1H, CpH), 2.057
(br, 9H, AdH), 1.760 (br, 6H, AdH), 1.592 (s, 3H, C5Me4), 1.585 (s, 3H,
C5Me4), 1.561 (s, 3H, C5Me4), 1.295 (s, 9H, tBu), 1.221 (d, 3H, C5Me4).
3.8. Synthesis of 2-(diphenylcyclopentadienyl)-4-tert-butyl-6-
adamantylphenol (7)
NMR (C6D6, 300 MHz, 298 K): d 7.58e7.60 (m, 4H, PhH), 7.569 (d,
1H, ArH), 7.265 (d, 1H, ArH), 7.07e7.11 (m, 6H, PhH), 6.398 (s 2H,
A solution of 4 (2.402 g, 6.61 mmol) in Et2O (20 mL) was slowly
CpH), 2.415 (br, 6H, AdH), 2.123 (br, 3H, AdH), 1.883, 1.760 (dd, 6H
n
t
added to a solution of BuLi (15 mmol) in Et2O (20 mL) at ꢂ15 ꢀC.
AdH), 1.515 (s, 9H, Bu). 13C NMR (C6D6, 75 MHz, 298 K):
d
172.38,
The mixture was slowly warmed to room temperature and stirred
for 5 h. After the solvent was removed, the residue was suspended
in toluene (40 mL). To the suspension was dropwise added a solu-
tion of 3,4-diphenyl-2-cyclopentenone (1.542 g, 6.61 mmol) in
toluene (20 mL) at ꢂ15 ꢀC over an hour. The reaction mixture was
stirred at room temperature overnight and 65 ꢀC for further 4 h,
then quenched with 20 mL of saturated NH4Cl (aq). The organic
layer was separated, washed three times with water (40 mL) and
dried over MgSO4. Removal of the solvent on a rotary evaporator
left a brownish residue. Pure product (1.178 g, 2.35 mmol, 35.6%)
was obtained by column chromatography over silica (hexanes/
CH2Cl2, 1:2) as yellow needles. Anal. Calcd for C37H40O (500.71):
C, 88.75; H, 8.05. Found: C, 88.66; H, 7.98. 1H NMR (CDCl3, 300 MHz,
147.33, 145.64, 135.50, 133.11, 133.02, 131.94, 131.13, 130.02, 129.16,
128.41, 123.46, 123.29, 41.49, 37.73, 37.11, 35.02, 31.89, 29.33.
3.12. X-ray structure determination
X-ray data were collected at 293 K on a Siemens P4 four-circle
diffractometer for 8 and a Bruker SMART-CCD diffractometer for 9
ꢀ
(graphite-monochromated Mo KR radiation: l ¼ 0.71073 A). Details
of the crystal data, data collections, and structure refinements are
summarized in Table 5. The structures were solved by direct
methods [57] and refined by full-matrix least-squares on F2. All
non-hydrogen atoms were refined anisotropically, and the
hydrogen atoms were included in idealized positions. All

J. Li et al. / Journal of Organometallic Chemistry 696 (2011) 2499e2506
2505
Table 5
(2/3 of total amount) in toluene (40 mL), thermostated at the
desired temperature, and saturated with ethylene (1 atm). The
polymerization reaction was started by injection of a mixture of
a catalyst and AliBu3 (1/3 of total amount) in toluene (5 mL) and
a solution of Ph3CB(C6F5)4 in toluene (5 mL) at the same time. After
a certain period of time, the polymerization was quenched by
injecting acidified methanol. The polymer was collected by filtra-
tion, washed with water and methanol, and dried at 60 ꢀC in vacuo
to a constant weight.
Crystallographic data and structural refinement details for complexes 8 and 9.
8
9
mol formula
Mol wt
C26H32Cl2OTi
479.32
Monoclinic
P2(1)/c
7.3163(11)
19.168(3)
17.210(3)
90
90.526(2)
90
2413.4(6)
4
C29H38Cl2OTi
521.39
Triclinic
P-1
10.095(2)
10.579(2)
13.532(3)
93.73(3)
107.57(3)
95.03(3)
1366.0(5)
2
Crystal system
Space group
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
a
/deg
/deg
b
Acknowledgments
g
/deg
3
ꢀ
V/A
Z
This work was supported by the National Natural Science
Foundation of China (Nos. 21074043 and 20772044).
Dc/g cmꢂ3
1.319
1008
0.591
u
1.268
552
0.528
u
F(000)
Abs coeff/mmꢂ1
Scan type
e2
q
e2
q
Appendix A. Supplementary material
Collect range, deg
No. of reflns
No. of indep reflns
Rint
No. of data/restraints/params
R (I > 2sigma(I))
Rw (I > 2sigma(I))
Goodness of fit
Largest diff peak
1.59 ꢃ 2
13,368
4749
q
ꢃ 26.07
3.01 ꢃ 2
13,562
6211
q
ꢃ 27.48
CCDC 804461 and 804462 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
0.0555
0.0244
4749/0/277
0.0502
0.1138
0.950
0.504
ꢂ0.318
6211/0/305
0.0434
0.1147
1.052
0.585
ꢂ0.410
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a magnetic stirrer was charged with 70 mL of 1-hexene solution in
toluene, thermostated at desired temperature and saturated with
ethylene (1.0 atm). The polymerization reaction was started by
addition of a mixture of catalyst and AliBu3 in toluene (5 mL) and
a solution of Ph3CB(C6F5)4 in toluene (5 mL) at the same time. The
vessel was pressurized to 5 atm with ethylene immediately and
the pressure was kept by continuously feeding of ethylene. After
the reaction mixture was stirred at the desired temperature for
10 min, the polymerization was quenched by injecting acidified
ethanol containing HCl (3 M). The polymer was collected by
filtration, washed with water and ethanol, and dried to a constant
weight under vacuum.
3.14. General procedure of ENB polymerization and E/ENB
copolymerization
ENB polymerization experiments were performed as follows:
a dry 100 mL flask with a magnetic stirrer was charged with
a solution of appropriate amount of ENB and AliBu3 (2/3 of total
amount) in toluene (40 mL) under N2, thermostated at the desired
temperature in an oil bath. The polymerization reaction was started
by injection of a mixture of a catalyst and AliBu3 (1/3 of total
amount) in toluene (5 mL) and a solution of Ph3CB(C6F5)4 in toluene
(5 mL) at the same time. After a certain period of time, the poly-
merization was terminated by injecting acidified methanol [HCl
(3 M)/methanol 1:1]. The polymer was collected by filtration,
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