Synthesis of new substituted cyclopentadienyl titanium monomethoxydifluorides with BF3·OEt2 as fluorinating reagent and their use in syndiotactic polymerization of styrene

Article abstract of DOI:10.1016/j.jorganchem.2004.01.031

Five substituted cyclopentadienyl titanium trimethoxide complexes, RCpTi(OMe)₃ (R=Me (2b), ⁱPr (2c), Me₃Si (2d), allyl (2e), PhCH₂ (2f)), were prepared. By reacting RCpTi(OMe)₃ with BF₃OMe₂, six RCpTiF₂(OMe) (R=H (3a), Me (3b), ⁱPr (3c), Me₃Si (3d), allyl (3e), PhCH₂ (3f)) were obtained. When activated with methylaluminoxane (MAO), the activities of RCpTiF₂(OMe) system were less than those of RCpTi(OMe)₃ system in solution polymerization of styrene, but the polymers made by RCpTiF₂(OMe) exhibited higher Mw and melting point than those by RCpTi(OMe)₃. Both systems produced polymers with similar syndiotacticities in the range 92.4-97.6%. Introduction of a substituent group into the Cp-ligand enhanced the melting points of the polymers, and meanwhile decreased the catalytic activities of RCpTi(OMe)₃/MAO and RCpTiF₂(OMe)/MAO systems, where the order of activity was RCp=Cp > MeCp > ⁱPrCp > Me₃SiCp > CH₂=CHCH₂Cp > PhCH₂Cp. Complexes 2a (CpTi(OMe)₃) and 3a showed the highest activities respectively for both systems, and are three to four times more active than CpTiCl₃. In bulk polymerization, the difference of activities between RCpTi(OMe)₃/MAO and RCpTiF₂ (OMe)/MAO systems became small, where complexes 2e and 3e exhibited remarkably higher activities compared with their solution polymerization activities. The maximum polymerization activities were found at the polymerization temperature of 50 °C for most of the complexes. The influence of the polymerization time (t_P), polymerization temperature (T_P) and Al/Ti ratio on the activities of complexes 2b and 3b were investigated. It was observed that the initial rate of propagation of complex 2b was higher than that of complex 3b and the highest activities of both catalysts were reached at the relatively low Al/Ti ratio of 150 and decrease for larger ratios.

Full text of DOI:10.1016/j.jorganchem.2004.01.031

Journal of Organometallic Chemistry 689 (2004) 1503–1510
www.elsevier.com/locate/jorganchem
Synthesis of new substituted cyclopentadienyl titanium
monomethoxydifluorides with BF3 ꢀ OEt2 as fluorinating reagent
and their use in syndiotactic polymerization of styrene
*
Xianmiao Qian, Jiling Huang , Yanlong Qian
Laboratory of Organometallic Chemistry, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
Received 23 April 2002; accepted 6 January 2004
Abstract
Five substituted cyclopentadienyl titanium trimethoxide complexes, RCpTi(OMe)3 (R ¼ Me (2b), iPr (2c), Me3Si (2d), allyl (2e),
i
PhCH2 (2f)), were prepared. By reacting RCpTi(OMe)3 with BF3OMe2, six RCpTiF2(OMe) (R ¼ H (3a), Me (3b), Pr (3c), Me3Si
(3d), allyl (3e), PhCH2 (3f)) were obtained. When activated with methylaluminoxane (MAO), the activities of RCpTiF2(OMe)
system were less than those of RCpTi(OMe)3 system in solution polymerization of styrene, but the polymers made by RCp-
TiF2(OMe) exhibited higher Mw and melting point than those by RCpTi(OMe)3. Both systems produced polymers with similar
syndiotacticities in the range 92.4–97.6%. Introduction of a substituent group into the Cp-ligand enhanced the melting points of the
polymers, and meanwhile decreased the catalytic activities of RCpTi(OMe)3/MAO and RCpTiF2(OMe)/MAO systems, where the
order of activity was RCp ¼ Cp > MeCp > iPrCp > Me3SiCp > CH2@CHCH2Cp > PhCH2Cp. Complexes 2a (CpTi(OMe)3) and 3a
showed the highest activities respectively for both systems, and are three to four times more active than CpTiCl3. In bulk poly-
merization, the difference of activities between RCpTi(OMe)3/MAO and RCpTiF2(OMe)/MAO systems became small, where
complexes 2e and 3e exhibited remarkably higher activities compared with their solution polymerization activities. The maximum
polymerization activities were found at the polymerization temperature of 50 °C for most of the complexes. The influence of the
polymerization time ðtPÞ, polymerization temperature ðTPÞ and Al/Ti ratio on the activities of complexes 2b and 3b were investigated.
It was observed that the initial rate of propagation of complex 2b was higher than that of complex 3b and the highest activities of
both catalysts were reached at the relatively low Al/Ti ratio of 150 and decrease for larger ratios.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Titanocene; Syndiotactic polymerization; Styrene; Catalyst
1. Introduction
tacticity, the melting point and the molecular weight of
s-PS, and meanwhile decrease the amount of MAO, a
wide variety of new catalysts based on titanium, zirco-
nium or other transition metal compounds have been
developing [3–5]. Among them, half-sandwich titanoc-
enes of types Cp0TiX3 and Ind0TiX3 (where Cp0 is
(un)substituted cyclopentadienyl, Ind0 is (un)substituted
indenyl, and X is Cl, F, Alkyl or alkoxyl, etc.) have been
demonstrated to be the most effective syndiotactic cat-
alyst precursors for styrene polymerization.
The polymerization mechanism and the structure of
the active site were investigated [6–13]. Many observa-
tions have been made viz.: (1) Replacing Cp ligand by
Cpꢁ ligand dramatically increased the molecular weight
of s-PS (Mw > 600 000), and the corresponding melting
In 1986, Ishihara et al. [1,2] first discovered syndio-
tactic polystyrene (s-PS) by using homogeneous tita-
nium compounds and methylaluminoxane (MAO). s-PS
is a crystalline polymeric material with a melting tem-
perature of about 270 °C, and has a high crystallization
rate, a high modulus of elasticity and an excellent re-
sistance to heat and chemical agents, which make s-PS
suitable for a large number of applications in industries.
In order to obtain an efficient catalyst system, which
should have a high polymerization activity, increase the
* Corresponding author. Fax: +86-21-54282375.
E-mail address: qianling@online.sh.cn (J. Huang).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.01.031

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X. Qian et al. / Journal of Organometallic Chemistry 689 (2004) 1503–1510
point of polymer also rised [14,15]. (2) Replacing Cp
ligand by Ind ligand enhanced the catalyst activity, the
syndiotacticity and the melting point of the polymer.
This catalyst was relatively insensitive to polymerization
conditions compared with CpTiCl3 [16,17]. (3) Partial or
full replacement of chlorine atoms by alkyl or alkoxyl
groups often raised catalytic activity [14,15,18–24]. (4)
Full replacement of chlorine atoms by fluorine atoms
showed a large increase in the catalyst activity, especially
for CpꢁTiF3 and Ind0TiF3, and reduced the amount of
excess MAO to an Al:Ti ratio of 300 [25,26].
To investigate the catalytic activities and properties
of polymers produced by a new half-sandwich titano-
cene system in which one chlorine atom is substituted by
an alkoxyl group and the other two by fluorine atoms is
the basis of this report.
toluene for 24 h, although the exchange reaction of
(RCp)2TiCl2 with BF3 ꢀ OEt2 easily took place [31]. In-
stead, we found that RCpTi(OMe)3 reacts in a molar
ratio of 3:2 with BF3 ꢀ OEt2 in diethyl ether to give target
compounds in 40–80% yield, which are purified by
sublimation under vacuum and found to be elementally
pure (Scheme 1). Synthetic details and spectral data for
these compounds are given in the experimental section.
It was found that the fluorine atoms in complexes 3a
to 3f shown two peaks in 19F NMR spectrum at room
temperature (Table 1). There existed a broad peak in
100–150 ppm and a sharp peak in 160–190 ppm. The
area ratio of two peaks depended on the substituted
group in Cp. It indicated that the chemical environment
of the fluorine atoms is different. When the temperature
increased to 50 °C, the two peaks turned to one peak.
The first fluorinated half-sandwich titanocene
(CpTiF3) was prepared through the reaction of
CpTi(OEt)3 with CH3COF by Nesmeyanov in 1968. He
further obtained CpTiF2(OEt) and CpTiF(OEt)2 by the
exchange reaction of CpTiF3 with CpTi(OEt)3 [27]. In
recent years, Roesky [28–30] used AsF3 and especially
Me3SnF as fluorinated reagents, and succeeded in pre-
paring a large range of fluorinated half-sandwich tita-
nocenes and other organometallic fluorides.
2.2. Polymerization results
Table 2 summarizes the results on the syndiotactic
polymerization of styrene in solution with RCpTi
(OMe)3/MAO and RCpTiF2(OMe)/MAO systems. The
RCpTiF2(OMe)/MAO system is less active than the
corresponding RCpTi(OMe)3/MAO system at 50 °C.
The polymers produced by both systems have similar
syndiotacticities.
The active catalytic site for sPS polymerization, il-
lustrated in Scheme 2, is thought to be (RCp-
TiMe)þ(MAO ꢀ X2)ꢂ, where X is methoxy group or
fluoride. The methoxy group and fluoride are stripped
during the formation of active species. They could still
surround the active species and stabilize active species
In this work, we begin by using an easily available,
inexpensive and less toxic boron trifluoride diethyl eth-
erate (BF3 ꢀ OEt2) as fluorinating reagent to synthesize
six substituted cyclopentadienyl titanium mono-
methoxydifluoride complexes of general formula RCp-
i
TiF2(OMe) (R ¼ H, Me, Pr, Me3Si, Allyl, PhCH2) by
the reaction of RCpTi(OMe)3 with the BF3 ꢀ OEt2 and
detailed compare their catalytic behavior with
RCpTi(OMe)3 and CpTiCl3 in the syndiotactic poly-
merization of styrene.
.
MeOH/NEt3
ether
BF3
OEt2
RCpTiCl3
RCpTi(OMe)3
RCpTiF2(OMe)
ether
1a
2a
R=H
3a
R=H
R=H
1b
2 b
2. Results and discussion
R=Me
3 b
R=Me
R=Me
i
i
i
1c
1d
1e
R= Pr
2c
2d
2e
R= Pr
3 c
3d
3e
R= Pr
R=Me3Si
R=allyl
R=Me3Si
R=allyl
R=Me3Si
R=allyl
2.1. Catalyst synthesis
1 f R=PhCH2
2 f R=PhCH2
3
f R=PhCH2
Direct reaction of CpTiCl3 with BF3 ꢀ OEt2 did not
result in halide exchange even at reflux temperature in
Scheme 1.
Table 1
19F NMR spectrum of complexes 3a to 3f
Complex
27 °C
50 °C
Peak A (d ppm)
Peak B (d ppm)
Area ratio (A/B) d ppm
(3a) CpTiF2(OMe)a
134 (br. s)
114 (br. s)
106 (br. s)
136 (br. s)
109 (br. s)
129 (br. s)
184 (s)
161 (s)
160 (s)
183 (s)
163 (s)
179 (s)
3.6
1.9
3.6
31
135 (s)
(3b) MeCpTiF2(OMe)b
i
(3c) PrCpTiF(OMe)b
(3d) Me3SiCpTiF2(OMe)a
(3e) CH2@CHCH2CpTiF2 (OMe)b
1.6
1.8
(3f) PhCH2CpTiF2 (OMe)a
135 (s)
a Solvent: C6D6.
b Solvent: CDCl3.

X. Qian et al. / Journal of Organometallic Chemistry 689 (2004) 1503–1510
1505
Table 2
Syndiotactic polymerization of styrene in solution catalyzed by RCpTi(OMe)3/MAO and RCpTiF2(OMe)/MAO systemsa
Activityb (106) s-PSc (%)
Tm (°C)
Mw
MWD
d
Catalyst
Yield (g)
Conversion (%)
(2a) CpTi(OMe)3
(2b) MeCpTi(OMe)3
1.5847
1.4403
1.4108
1.1263
0.6508
0.3285
1.3630
1.2143
1.0329
0.6550
0.4566
0.2169
0.3328
87.2
79.2
77.6
62.0
35.8
18.1
75.0
66.8
56.8
36.0
25.1
11.9
18.3
18.16
16.50
16.16
12.91
7.46
92.7
97.0
96.7
97.6
96.2
93.3
93.9
97.2
97.3
94.2
95.8
92.4
92.5
258.3
48 000
76 500
2.16
2.12
i
(2c) PrCpTi(OMe)3
266.8
266.4
(2d) Me3 SiCpTi(OMe)3
(2e) CH2@CHCH2CpTi(OMe)3
(2f) PhCH2CpTi(OMe)3
(3a) CpTiF2(OMe)
3.76
15.62
13.91
11.84
7.50
258.9
266.1
269.4
269.8
267.4
264.5
257.9
54 800
96 400
1.94
1.96
(3b) MeCpTiF2(OMe)
i
(3c) PrCpTiF2(OMe)
(3d) Me3 SiCpTiF2(OMe)
(3e) CH2@CHCH2CpTiF2 (OMe)
(3f) PhCH2CpTiF2(OMe)
CpTiCl3
5.23
2.49
3.81
a Polymerization conditions: [Ti] ¼ 0.42 mM, Al/Ti ¼ 300, 50 °C for 1 h, styrene ¼ 2 ml, Vtotal ¼ 12 ml.
b g bulk polymer/(mol Ti ꢀ mol S ꢀ h).
c g of 2-butanone insoluble polymer/g of bulk polymer.
d Melting temperature of s-PS.
radical polymerization
.
RCpTiX2 + Al(CH3)2X + CH3
observation was shown in [(PhCH2CH2)Me4C5]-
Ti(OMe)3/MAO system by Newman [35]. The allyl
group is sterically less bulky than the isopropyl and
trimethylsilyl groups, but complexes 2e and 3e exhibit
lower activities. This indicates that the electron-donor
ability of the allyl group is less than that of the isopropyl
and trimethylsilyl groups. Moreover, the C@C bond of
allyl group might coordinate to the active center, as
suggested in the literature [36]. In addition, introduction
of substituent group into Cp-ligand increases the melt-
ing points of the polymers. On average, the melting
points of the polymers are 6–11 °C higher than those of
the polymers obtained with complexes 2a and 3a. When
R ¼ iPr and Me3Si, the melting points of the polymers
made with RCpTiF2(OMe) are 2–3 °C higher than those
with RCpTi(OMe)3. This shows that the substituent
groups not only have an influence on the activity due to
steric and electronic effects but also have an effect on the
syndiotacticities and the melting points of the polymers.
Compared with complexes 2a and 3a, the polymers
made by complexes 2b and 3b exhibit higher molecular
weight. The molecular weight is controlled by the rela-
tive rates of two competing processes, the b-hydride
elimination and the styrene insertion. This means the
introduction of fluoride ligand into the coordination
sphere of the metal compound can reduce the b-hydride
elimination.
RCpTiX3 + Al(CH3)3
.
CH3
MAO
.
C2H6
RCpTiXCH3 + [MAO X]
[RCpTiCH3]+
.
-
[MAO X2]
Scheme 2. Formation of initiating species by RcpTiX3 MAO system.
[32]. The methoxy group is better p-donor than fluo-
ride ligand [33], which might lead to generating more
active sites in RCpTi(OMe)3/MAO system than in RCp-
TiF2(OMe)/MAO systems. Therefore, the RCpTi(OMe)3
shows more active than RCpTiF2(OMe).
Compared with CpTiCl3, complexes 2a and 3a show
much higher catalytic activities. It indicates that they
could generate more active sites and enhance the cata-
lytic activity. Similar phenomena have been described in
the literature [25,26].
Introduction of substituent group into Cp-ligand
decreases the catalytic activities for RCpTi(OMe)3/
MAO and RCpTiF2(OMe)/MAO systems, where the
order of activity is RCp ¼ Cp > MeCp > iPrCp >
Me3SiCp > CH2@CHCH2Cp > PhCH2Cp. Generally,
the stronger electron-donating and less bulky sub-
stituent groups are beneficial to the polymerization by
increasing the rate of propagation. Compared with
complexes 2a and 3a, complexes 2f and 3f have only a
fifth of the activity. Besides the steric bulk of the benzyl
group, it was able to coordinate to the titanium [34].
This coordination was so strong that it interfered with
coordination and insertion of styrene. So complexes 2f
and 3f show the lowest activities in both systems. Similar
Taking complexes 2b and 3b as representatives of
each corresponding system, we further investigated the
influence of polymerization time ðtPÞ, polymerization
temperature ðTPÞ and Al/Ti ratio on their activities. The
dependence of the polymerization activity on the poly-
merization time with the two complexes is as shown in
Fig. 1. The highest activities can be observed after 5 min
for both complexes and thereafter decreased. However,
the activity of the trimethoxy-substituted complex (2b) is

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X. Qian et al. / Journal of Organometallic Chemistry 689 (2004) 1503–1510
50 °C for both catalysts. At 90 °C, the syndiotacticity
140
120
100
80
MeCpTi(OMe)3
MeCpTiF2(OMe)
decreases sharply, because syndio-directing active sites
are destroyed into atactic sites [20]. In addition, Table 3
shows that the activity is affected by Al/Ti ratio. The
highest activities for both catalysts are reached at the
relatively low Al/Ti ratio of 150 and decrease for larger
ratios. This is contrary to the CpTiCl3 system where
activity is maximum at Al/Ti ratio of 1500 under iden-
tical condition.
60
40
20
When the polymerization is carried in bulk (Table 4),
polymer yield is higher, and the possibility for the oc-
clusion of active centers in the precipitated polymer is
aggravated as a consequence of the restricted mobility.
The difference of the activities for RCpTi(OMe)3/MAO
and RCpTiF2(OMe)/MAO systems becomes small,
compared with that in solution polymerization (Table
2). With the exception of complexes 2f and 3f, all other
complexes maintain high levels of syndiotacticity at the
high monomer concentration used. For both systems,
the unsubstituted-Cp complexes afford the highest
polymer yields and hence activities, while the benzyl-Cp
complexes yield the least activities. Similar results were
observed in 2-PhCH2IndTiCl3 system [16]. A remark-
able change is observed in the complexes 2e and 3e
systems, whereby in bulk polymerization, they show
much higher activities than in solution polymerization.
The variation of the monomer concentration probably
causes the difference of a dynamic interaction between
the allyl group and titanium. Because of the unusual
behavior of alkenyl groups, a more detailed research
about their influence on catalytic activity is in progress.
As shown in Table 4, maximum polymerization
activities are obtained at 50 °C for most of the com-
plexes. Higher temperature (TP ¼ 90 °C) led to the de-
crease of the activities of catalysts and syndiotacticities
of polymers.
0
0
20
40
60
80
100
TP (min)
Fig. 1. Dependence of the polymerization activity on the polymeriza-
tion time with MeCpTi(OMe)3 and MeCpTiF2(OMe). Polymerization
conditions: [Ti] ¼ 0.42 mM, Al/Ti ¼ 300, 50 °C, styrene ¼ 2 ml,
Vtotal ¼ 12 ml.
higher than that of the difluoromethoxy substituted
complex (3b) at the initial stages of polymerization.
With the passage of time, the difference of their activities
becomes smaller. The activity of complex 2b decreases
much faster than that of complex 3b after 10 min. The
decrease may be attributed to the deactivation of the
active centers and to the occlusion of part of the catalyst
in the precipitating polymer [2]. This indicates again that
the fluorinated complex 3b is more stable than complex
2b, although complex 2b has a faster propagation rate
than complex 3b at the beginning of polymerization due
to more active sites. A time dependence of activity was
observed in CpTiF3, MeCpTiF3 and MeIndTiF3 [25,26].
Table 3 summarizes the comparison of polymeriza-
tion results at different TP and Al/Ti ratio. In the range
25–90 °C, the activity of complex 3b is slightly less than
that of complex 2b, and the syndiotacticities of obtained
polymers are similar. The highest activity is reached at
Table 3
Comparison of the activities of MeCpTi(OMe)3 and MeCpTiF2(OMe) at different TP and Al/Ti ratioa
Catalyst
Al/Ti (mol/mol)
TP (°C)
Yield (g)
Conversion (%)
Activityb (106)
s-PSc
MeCpTi(OMe)3
300
300
300
300
150
500
25
50
70
90
50
50
0.9785
1.4403
1.2880
1.0687
1.5001
1.2781
53.8
79.2
70.8
58.8
82.5
70.3
11.21
16.50
14.76
12.25
17.19
14.64
98.6
97.0
92.6
77.3
96.8
97.2
MeCpTiF2(OMe)
300
300
300
300
150
500
25
50
70
90
50
50
0.9157
1.2143
1.1680
0.9552
1.3468
0.9328
50.4
66.8
64.2
52.5
74.1
51.3
10.49
13.91
13.38
10.94
15.43
10.69
98.9
97.2
92.6
74.6
96.0
93.8
a Polymerization conditions: [Ti] ¼ 0.42 mM, 1 h, styrene ¼ 2 ml, Vtotal ¼ 12 ml.
b g of bulk polymer/(mol Ti ꢀ mol S ꢀ h).
c g of 2-butanone insoluble polymer/g of bulk polymer (%).

X. Qian et al. / Journal of Organometallic Chemistry 689 (2004) 1503–1510
1507
Table 4
Syndiotactic polymerization of styrene in bulk catalyzed by RCpTi(OMe)3/MAO and RCpTiF2(OMe)/MAO systemsa
Catalyst
TP (°C)
Yield (g)
Conversion (%)
Activityb (106)
s-PSc (%)
(2a) CpTi(OMe)3
30
50
70
90
1.4859
4.6228
4.2580
2.9735
14.9
46.2
42.6
29.7
6.14
19.11
17.60
12.29
95.0
92.0
92.2
85.3
(2b) MeCpTi(OMe)3
30
50
70
90
1.3656
4.4201
3.6181
2.4962
13.7
44.2
36.2
25.0
5.64
18.27
14.95
10.32
92.4
94.9
93.7
86.1
i
(2c) PrCpTi(OMe)3
30
50
70
90
1.4204
3.5475
2.8341
2.5767
14.2
35.5
28.3
25.8
5.87
14.66
11.71
10.65
92.1
95.6
95.9
91.0
(2d) Me3 SiCpTi(OMe)3
30
50
70
90
2.6009
3.3117
2.9776
2.5812
26.0
33.1
29.8
25.8
11.00
13.69
12.31
10.67
93.5
95.0
93.3
88.6
(2e) CH2@CHCH2CpTi(OMe)3
(2f) PhCH2CpTi(OMe)3
50
4.3329
43.3
17.91
92.0
30
50
70
90
0.6823
0.8882
0.9840
0.9338
6.8
8.9
9.8
9.3
2.82
3.67
4.07
3.86
89.3
87.4
84.9
71.2
(3a) CpTiF2 (OMe)
30
50
70
90
1.8829
4.1231
4.0215
2.9899
18.8
41.2
40.2
29.9
7.78
17.04
16.62
12.36
96.0
93.4
92.0
88.8
(3b) MeCpTiF2 (OMe)
30
50
70
90
1.9508
3.9404
3.2235
2.4788
19.5
39.4
32.2
24.8
8.06
16.29
13.32
10.25
95.8
95.0
94.6
91.6
i
(3c) PrCpTiF2 (OMe)
30
50
70
90
1.0690
3.4948
2.5920
2.1011
10.7
35.0
25.9
21.0
4.42
14.45
10.71
8.68
82.8
90.6
93.8
85.4
(3d) Me3SiCpTiF2 (OMe)
30
50
70
90
2.4330
2.9177
3.2470
2.9650
24.3
29.2
32.5
29.7
10.06
12.06
13.42
12.25
93.2
93.2
92.1
89.0
(3e) CH2@CHCH2CpTiF2 (OMe)
(3f) PhCH2CpTiF2 (OMe)
50
3.9339
39.3
16.26
92.3
30
50
70
90
0.7482
0.8632
0.9810
0.9207
7.5
8.6
9.8
9.2
3.09
3.56
4.05
3.81
91.5
88.4
73.0
68.8
CpTiCl3
50
0.8056
8.1
3.33
82.3
a Polymerization conditions: [Ti] ¼ 0.21 mM, Al/Ti ¼ 300, tP ¼ 1 h, styrene ¼ 11 ml.
b g of bulk polymer/(mol Ti ꢀ mol S ꢀ h).
c g of 2-butanone insoluble polymer/g of bulk polymer.
3. Experimental
(diethyl ether, THF, toluene and n-hexane) and CaH2
(dichloromethane).
All manipulations were carried out under a dry argon
atmosphere using standard Schlenk techniques. Solvents
were purified by distillation over sodium benzophenone
MAO was produced by Witco GmbH. Styrene was
dried over anhydrous CaCl2, vacuum distilled from
CaH2 and stored at )25 °C in the dark. BF3 ꢀ OEt2 was

1508
X. Qian et al. / Journal of Organometallic Chemistry 689 (2004) 1503–1510
distilled from CaH2 at reduced pressure before use.
i
mmol), and NEt3 (10.7 ml, 76.2 mmol) were used to get
5.7 g (80%) of a pale yellow oil (74–76 °C/0.05 mmHg).
1H NMR (CDCl3): d 0.28 (s, 9H, SiMe3), 4.09 (s, 9H,
OCH3), 6.46 (t, J ¼ 2:6 Hz, 2H, Cp), 6.56 (t, J ¼ 2:6 Hz,
2H, Cp). IR (KBr): m 3078w, 2952m, 2910m, 2809m,
1440w, 1406w, 1367m, 1314w, 1247s, 1182m, 1122m,
1047s, 908m, 840s, 797s, 733m, 650m, 628m, 562s. EI
MS: 278 (Mþ, 6), 263 (Mþ–CH3, 100), 247 (Mþ–OCH3,
23), 232 (Mþ–CH3–OCH3, 12), 216 (Mþ – 2OCH3, 13).
Anal. Calc. for C11H22O3SiTi: C, 47.48; H, 7.97. Found:
C, 47.49; H, 7.96%.
CpTi(OMe)3 [37], PrCpTiCl3 [38], Me3SiCpTiCl3 [39],
CH2@CHCH2CpTiCl3 [40], and PhCH2CpTiCl3 [41]
were synthesized by using published methods. The
general procedure for the preparation of RCpTi(OMe)3
was carried out as in the literature [41].
Mass spectra were measured on a HP5989A spec-
trometer. IR spectra were recorded on Nicolet FTIR
5SXC spectrometer. 1H NMR and 19F NMR were
measured on an ADVANCE-500 spectrometer using
tetramethylsilane (TMS) and CF3COOH as internal
standards, respectively. Elemental analyses were per-
formed by Shanghai Institute of Organic Chemistry.
3.4. CH2@CHCH2CpTi(OMe)3 (2e)
3.1. MeCpTi(OMe)3 (2b)
The operation was the same as that described for 2b.
CH2@CHCH2CpTiCl3 (3.1 g, 12.1 mmol), MeOH (1.5
ml, 36.3 mmol), and NEt3 (5.1 ml, 36.3 mmol) were used
to produce 2.5 g (83%) of a bright yellow oil (80–82 °C/
To an Et2O solution (120 ml) of MeCpTiCl3 (4.2 g,
18.0 mmol) was added dropwise an Et2O solution (30
ml) of MeOH (2.2 ml, 54.0 mmol) and NEt3 (7.5 ml,
54.0 mmol) at room temperature, and stirred overnight.
The reaction mixture was filtered, and the residue was
washed with diethyl ether (2 ꢃ 25 ml). All filtrates were
combined and concentrated under vacuum to remove
the solvent. The residual oil was distilled at 57–59 °C/
1
0.2 mmHg). H NMR (CDCl3): d 3.38 (d, J ¼ 6:7 Hz,
2H, CH2), 4.10 (s, 9H, OCH3), 5.09–5.16 (m, 2H,
CH2@), 5.95–6.03 (m, 1H, CH@), 6.17 (t, J ¼ 2:7 Hz,
2H, Cp), 6.25 (t, J ¼ 2:7 Hz, 2H, Cp). IR (KBr): m
3077w, 2977w, 2910m, 2808m, 1638m, 1491w, 1429m,
1288w, 1114s, 1038m, 995m, 912m, 855s, 799s, 630m,
530s. EI MS: 246 (Mþ, 9), 215 (Mþ–OCH3, 18), 184
(Mþ–2OCH3, 100), 141 (Mþ–C3H5Cp, 63), 105
(C3H5Cpþ, 46), 79 (TiOMeþ, 31). Anal. Calc. for
C11H18O3Ti: C, 53.68; H, 7.37. Found: C, 53.35; H,
7.18%.
1
0.04 mmHg to give 3.3 g (83%) of a pale yellow oil. H
NMR (CDCl3): d 2.26 (s, 3H, CH3), 4.11 (s, 9H, OCH3),
6.12 (t, J ¼ 2:6 Hz, 2H, Cp), 6.21 (t, J ¼ 2:6 Hz, 2H,
Cp). IR (KBr): m 3085w, 2909m, 2887m, 2806s, 1498m,
1439m, 1375w, 1353w, 1241w, 1127s, 1052m, 1036m,
935w, 855s, 796s, 628m, 530s. EI MS: 220 (Mþ, 29), 189
(Mþ–OCH3, 39), 188 (Mþ–HOCH3, 67), 158 (Mþ–
2OCH3, 57), 141 (Mþ–CH3Cp, 100), 127 (Mþ–3OCH3,
14). Anal. Calc. for C9H16O3Ti: C, 49.12; H, 7.33.
Found: C, 49.12; H, 6.98%.
3.5. PhCH2CpTi(OMe)3 (2f)
The operation was the same as that described for 2b.
PhCH2CpTiCl3 (5.4 g, 17.6 mmol), MeOH (2.1 ml, 52.8
mmol), and NEt3 (7.5 ml, 52.8 mmol) were used to
produce 3.5 g (68%) of a pale yellow oil (128–130 °C/
i
3.2. PrCpTi(OMe)3 (2c)
1
0.05 mmHg). H NMR (CDCl3): d 3.95 (s, 2H, CH2),
The operation was the same as that described for 2b.
iPrCpTiCl3 (3.9 g, 12.8 mmol), MeOH (1.6 ml, 38.5
mmol) and NEt3 (5.4 ml, 38.5 mmol) were used to give
to give 2.6 g (82%) of a pale yellow oil (72–75 °C/0.1
4.10 (s, 9H OCH3), 6.12 (t, J ¼ 2:7 Hz, 2H, Cp), 6.23 (t,
J ¼ 2:7 Hz, 2H, Cp), 7.19–7.33 (m, 5H, Ph). IR (KBr): m
3060w, 3026w, 2910m, 2808m, 1602w, 1494m, 1453m,
1437w, 1109m, 1036m, 938w, 796s, 704s, 623m, 546s. EI
MS: 296 (Mþ, 1), 265 (Mþ–OCH3, 25), 264 (Mþ–
HOCH3, 44), 234 (Mþ–2OCH3, 100), 203 (Mþ–3OCH3,
27). Anal. Calc. for C15H20O3Ti: C, 60.83; H, 6.81.
Found: C, 60.79; H, 6.74%.
1
mmHg). H NMR (CDCl3): d 1.28 (d, J ¼ 6:9 Hz, 6H,
CH3), 2.96–3.01 (m, 1H, CH), 4.11 (s, 9H, OCH3), 6.20
(s, 4H, Cp). IR (KBr): m 3091w, 2959s, 2910m, 2872m,
2808m, 1731w, 1489m, 1462m, 1456m, 1422w, 1380w,
1362m, 1317m, 1247w, 1154s, 1130s, 1037m, 932m,
847s, 793s, 683s, 622s, 542s. EI MS: 248 (Mþ, 3), 217
(Mþ–OCH3, 79), 186 (Mþ–2OCH3, 45), 155 (Mþ–
3OCH3, 10), 141 (Mþ–iPrCp, 60). Anal. Calc. for
C11H20O3Ti: C, 53.24; H, 8.12. Found: C, 53.28; H,
8.20%.
3.6. CpTiF2(OMe) (3a)
To an Et2O solution (20 ml) of CpTi(OMe)3 (0.55 g,
2.7 mmol) was added dropwise an Et2O solution (10 ml)
of BF3 ꢀ OEt2 (0.25 ml, 2.0 mmol) at )30 °C, whereupon
a solid immediately began to form. The reaction mixture
was allowed to warm to room temperature, and stirred
overnight. The solvent was removed under vacuum, and
the residue sublimed at 110 °C/0.1 mmHg to yield 0.37 g
3.3. Me3SiCpTi(OMe)3 (2d)
The operation was the same as that described for 2b.
Me3SiCpTiCl3 (7.4 g, 25.4 mmol), MeOH (3.1 ml, 76.2
1
(76%) of a yellow solid. m.p. ¼ 130–132 °C. H NMR

X. Qian et al. / Journal of Organometallic Chemistry 689 (2004) 1503–1510
1509
(CDCl3): d 4.11 (br.s, 3H, OCH3), 6.71 (s, 5H, Cp). IR
(KBr): m 3098m, 2932w, 2892w, 2826w, 1804w, 1656w,
1445m, 1361w, 1038s, 1018m, 863m, 828s, 618s, 591s,
543s. EI MS: 182 (Mþ, 80), 163 (Mþ–F, 49), 151 (Mþ–
OCH3, 68), 132 (Mþ–F–OCH3, 98), 117 (Mþ–Cp, 60),
86 (TiFþ2 , 38). Anal. Calc. for C6H8F2OTi: C, 39.60; H,
4.43. Found: C, 39.52; H, 4.40%.
(Mþ–CH3, 33), 238 (Mþ–CH4, 100), 235 (Mþ–F, 5), 223
(Mþ–OCH3, 68), 208 (Mþ–CH3–OCH3, 48), 117 (Mþ–
Me3SiCp, 6). Anal. Calc. for C9H16F2OSiTi: C, 42.53;
H, 6.34. Found: C, 42.41; H, 6.45%.
3.10. CH2@CHCH2CpTiF2(OMe) (3e)
The same procedure as the described for 3a was used.
CH2@CHCH2CpTi(OMe)3 (1.5 g, 6.1 mmol) and
BF3 ꢀ OEt2 (0.57 ml, 4.5 mmol) were used to yield 0.90 g
3.7. MeCpTiF2(OMe) (3b)
1
The same procedure as described for 3a was used.
MeCpTi(OMe)3 (0.76 g, 3.4 mmol) and BF3 ꢀ OEt2 (0.32
ml, 2.5 mmol) were used to give 0.47 g (70%) of a bright
(66%) of an orange solid. m.p. ¼ 82–84 °C. H NMR
(CDCl3): d 3.49 (d, J ¼ 6:6 Hz, 2H, CH2), 4.04 (br.s,
3H, OCH3), 5.13–5.19 (m, 2H, CH2@), 5.93–6.06 (m,
1H, CH@), 6.41 (s, 2H, Cp), 6.59 (s, 2H, Cp). IR (KBr):
m 3111w, 3080w, 2978w, 2913w, 1639m, 1490m, 1429m,
1290w, 1045m, 996m, 913m, 851s, 810s, 733m, 631s,
580s, 510s. EI MS: 222 (Mþ, 3), 203 (Mþ–F, 45), 184
(Mþ–2F, 19), 172 (Mþ–F–OCH3, 61), 105 (C3H5Cpþ,
66), 79 (TiOCH3þ, 100). Anal. Calc. for C9H12F2OTi: C,
48.68; H, 5.45. Found: C, 48.60; H, 5.50%.
1
yellow solid. m.p. ¼ 107–109 °C. H NMR (CDCl3): d
2.38 (s, 3H, CH3), 4.05 (br.s, 3H, OCH3), 6.39 (s, 2H,
Cp), 6.59 (s, 2H, Cp). IR (KBr): m 3114w, 3084w, 2943w,
2833w, 1497m, 1459w, 1378w, 1247w, 1042m, 1006m,
937w, 895m, 844s, 615s, 581s, 542s. EI MS: 196 (Mþ,
17), 177 (Mþ–F, 9), 165 (Mþ–OCH3, 20), 146 (Mþ–F–
OCH3, 28), 86 (TiFþ2 , 14), 79 (MeCpþ, 56). Anal. Calc.
for C7H10F2OTi: C, 42.89; H, 5.14. Found: C, 42.77; H,
5.01%.
3.11. PhCH2CpTiF2(OMe) (3f)
i
3.8. PrCpTiF2(OMe) (3c)
To an Et2O solution (20 ml) of PhCH2CpTi(OMe)3
(0.75 g, 2.5 mmol) was added dropwise an Et2O solution
(10 ml) of BF3 ꢀ OEt2 (0.23 ml, 1.9 mmol) at )30 °C. The
reaction mixture was allowed to warm to room tem-
perature, and stirred overnight. The solvent was re-
moved under vacuum. The residue was washed with n-
hexane, and dried under vacuum. The solid was re-
crystallized with CH2Cl2/n-hexane at )25 °C to obtain
The same procedure as the described for 3a was used.
iPrCpTi(OMe)3 (0.82 g, 3.3 mmol) and BF3 ꢀ OEt2 (0.30
ml, 2.4 mmol) were used to give 0.36 g (48%) of a yellow
1
solid. m.p. ¼ 78–80 °C. H NMR (CDCl3): d 1.30 (d,
J ¼ 6:9 Hz, 6H, CH3), 3.07–3.15 (m, 1H, CH), 4.12
(br.s, 3H, OCH3), 6.46 (s, 2H, Cp), 6.56 (s, 2H, Cp). IR
(KBr): 3106w, 2961s, 2928m, 2872m, 1735w, 1637w,
1491m, 1462m, 1424w, 1382w, 1364w, 1318w, 1152w,
1105w, 1082w, 1041m, 931m, 804s, 732m, 681m, 628s,
583s, 503m. EI MS: 224 (Mþ, 3), 205 (Mþ–F, 18), 193
(Mþ–OCH3, 20), 174 (Mþ–F–OCH3, 10), 107 (iPrCpþ,
24). Anal. Calc. for C9H14F2OTi: C, 48.24; H, 6.30.
Found: C, 47.98; H, 6.19%.
1
0.42 g (61%) of a orange crystal. m.p. ¼ 122–124 °C. H
NMR (CDCl3): d 4.04 (br.s, 3H, OCH3), 4.07 (s, 2H,
CH2), 4.00 (br.s, 3H, OCH3), 6.36 (s, 2H, Cp), 6.56 (s,
2H, Cp), 7.23–7.34 (m, 5H, Ph). IR (KBr): m 3095m,
3025w, 2923w, 2826w, 1723w, 1600w, 1491m, 1450m,
1425m, 1366w, 1233w, 1041m, 854s, 836m, 769w, 732m,
704m, 620s, 593m, 544s. EI MS: 253 (Mþ–F, 6), 252
(Mþ–HF, 18), 241 (Mþ–OCH3, 12), 240 (Mþ–HOCH3,
98), 222 (Mþ–F–OCH3, 56), 155 (PhCH2Cpþ, 53), 86
(TiFþ2 , 16), 77 (Phþ, 44). Anal. Calc. for C13H14F2OTi:
C, 57.38; H, 5.19. Found: C, 56.95; H, 5.11%.
3.9. Me3SiCpTiF2(OMe) (3d)
To an Et2O solution (20 ml) of Me3SiCpTi(OMe)3
(0.74 g, 2.7 mmol) was added dropwise an Et2O solution
(10 ml) of BF3 ꢀ OEt2 (0.25 ml, 2.0 mmol) at )30 °C. The
reaction mixture was allowed to warm to room tem-
perature, and stirred overnight. The solvent was re-
moved under vacuum. The residue was washed with
cold n-hexane, and dried under vacuum. The solid was
kept at 50 °C/0.05 mmHg to removed orange-red oil,
and then sublimed at 80 °C/0.05 mmHg to yield 0.25 g
(37%) of a yellow solid. m.p. ¼ 73–75 °C. 1H NMR
(CDCl3): d 0.33 (s, 9H, SiMe3), 4.17 (br.s, 9H, OCH3),
6.79 (s, 2H, Cp), 7.26 (s, 2H, Cp). IR (KBr): 3103w,
2955m, 2897w, 1606w, 1448w, 1410m, 1369w, 1317w,
1250s, 1178m, 1119w, 1050m, 907m, 840s, 759m, 729m,
696w, 627s, 591m, 544m, 516m. EI MS: 254 (Mþ, 1), 239
3.12. Polymerization procedure
Polymerization was conducted in small ampoules
baked under vacuum and flushed with argon several
times. Styrene, toluene, MAO was sequentially injected.
After the catalyst precursor in toluene was added, the
bottle was placed in an oil bath at the desired poly-
merization temperature at once. After 1 h, the poly-
merization was quenched with 10% HCl in ethanol,
filtered, washed with ethanol and dried under vacuum at
80 °C for 24 h to a constant weight. The melting tem-
perature of the polymers was recorded on DSC Uni-
versal V2.3C TA Instrument.

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X. Qian et al. / Journal of Organometallic Chemistry 689 (2004) 1503–1510
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Acknowledgements
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The authors gratefully acknowledge the financial
support of the National Natural Science Foundation of
China (20072004), the special Funds for Major State
Basic Research Projects (G1999064801) and the Re-
search Fund for the Doctoral Program of High Educa-
tion (RFDP) (20020251002).
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