Polymerizable group 4 ansa-cyclopentadienyl-amido catalysts for the copolymerization of ethylene with 1-octene

Article abstract of DOI:10.1016/j.jorganchem.2011.03.007

A styrene unit has been successfully incorporated into the half metallocene constrained-geometry framework as [(η⁵-C₅Me ₄)SiMe₂(η¹-NC₆H ₄CHCH₂)]MX₂ (M = Ti, X = NMe₂, 6a; M = Zr, X = NMe₂, 6b; M = Ti, X = Cl, 7a; M = Zr, X = Cl, 7b). These complexes have been characterized with ¹H NMR, ¹³C NMR spectroscopy together with single crystal X-ray diffraction studies of 6a and 6b. A polystyrene-immobilized constrained-geometry catalyst 8 was formed by the radical copolymerization of 7a with styrene using AIBN as the initiator. The complexes 6a, 6b, 7a and 8 gave active homogeneous catalysts for the copolymerization of ethylene with 1-octene when treated with excess methylalumoxane (MAO). The polymerization results showed that 7a was highly active and effective for the incorporation of comonomer 1-octene whereas the zirconium complex 6b and the immobilized catalyst 8 yield low activities and low incorporations of 1-octene in the products with broad molecular weight distributions.

Full text of DOI:10.1016/j.jorganchem.2011.03.007

Journal of Organometallic Chemistry 696 (2011) 2414e2419
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Polymerizable group 4 ansa-cyclopentadienyl-amido catalysts for the
copolymerization of ethylene with 1-octene
Wendy Rusli, Boon-Ying Tay, Ludger P. Stubbs, Martin van Meurs, Jozel Tan, Chacko Jacob,
*
Sze-Chen Chia, Yuan-Ling Woo, Cun Wang
*
Institute of Chemical and Engineering Sciences, A STAR (Agency for Science, Technology and Research), 1 Pesek Road, Jurong Island, Singapore 627833, Singapore
a r t i c l e i n f o
a b s t r a c t
Article history:
A styrene unit has been successfully incorporated into the half metallocene constrained-geometry
framework as [(
h
5-C5Me4)SiMe2(
h
1-NC6H4CH]CH2)]MX2 (M ¼ Ti, X ¼ NMe2, 6a; M ¼ Zr, X ¼ NMe2, 6b;
Received 21 January 2011
Received in revised form
24 February 2011
M ¼ Ti, X ¼ Cl, 7a; M ¼ Zr, X ¼ Cl, 7b). These complexes have been characterized with 1H NMR, 13C NMR
spectroscopy together with single crystal X-ray diffraction studies of 6a and 6b. A polystyrene-immo-
bilized constrained-geometry catalyst 8 was formed by the radical copolymerization of 7a with styrene
using AIBN as the initiator. The complexes 6a, 6b, 7a and 8 gave active homogeneous catalysts for the
copolymerization of ethylene with 1-octene when treated with excess methylalumoxane (MAO). The
polymerization results showed that 7a was highly active and effective for the incorporation of como-
nomer 1-octene whereas the zirconium complex 6b and the immobilized catalyst 8 yield low activities
and low incorporations of 1-octene in the products with broad molecular weight distributions.
Ó 2011 Elsevier B.V. All rights reserved.
Accepted 3 March 2011
Keywords:
Olefin polymerization
Constrained-geometry catalyst
Polymerizable catalyst
Titanium
Zirconium
Cyclopentadienyl-amido ligand
1. Introduction
We wish to disclose here the synthesis of a new polymerizable
constrained-geometry catalyst 7a bearing
a styrene moiety
The silicon bridged Cp/amido systems Me2Si(
h
5-C5Me4)(h1
-
attached to the nitrogen atom. Also described here are the immo-
bilization of 7a on polystyrene support and the catalysts’ behaviour
towards the copolymerization of ethylene with 1-octene.
NtBu)MX2 (M ¼ Ti, Zr, X ¼ Cl, alkyl), also known as the constrained-
geometry catalysts (CGC), have attracted great interest for their
excellence in ethene/1-alkene copolymerization, forming linear
low-density polyethylene (LLDPE) which has a commercial scale of
over one billion kg per year [1,2]. In order to investigate the effect of
catalyst structure on polymerization parameters and polymer
properties, numerous contributions in this field have been focused
on the variations on the Cp ring, silicon bridge and nitrogen centre
[3]. Other examples include the binuclear analogous catalysts [4],
cross-linked (aminomethyl)polystyrene supported CGC and self-
2. Results and discussion
2.1. Synthesis of the ligand
For the purpose of post immobilization of catalyst, we tried to
incorporate the polymerizable styrene unit into the CGC system at
the three potential positions which are the Cp ring, silicon bridge
and the nitrogen atom. Due to styrene’s high sensitivity towards
cationic, anionic or radical polymerization and even high temper-
ature [8], functionalization at the Cp ring and the silicon bridge
failed under the conditions applied in the ligand synthesis.
Attempts of trying to attach the styrene unit to CGC system through
a chain also failed for the same reason. But we did successfully built
a polymerizable CGC system by introducing the styrene unit
directly to the nitrogen atom described in Fig. 1.
immobilized systems containing
u-alkenyl substituents [5]. They
show special capabilities for more branch production and higher
incorporation of olefins including styrene. Immobilization of
homogeneous catalysts on a support can usually lead to better
catalyst stability, longer life, uniform product morphology, less
reactor fouling, etc [6]. Polystyrene is one of the most widely used
organic supports, for example, for metathesis, phase-transfer,
crossed aldol reaction catalysts [7].
The synthesis of the ligand is quite straightforward (Scheme 1).
1,2,3,4-tetramethyl-1,3-cyclopentadiene was deprotonated with
n-BuLi to yield lithium tetramethylcyclopentadienide (1) which
was subsequently treated with dichlorodimethylsilane to give
* Corresponding author. Tel.: þ65 6796 3838; fax: þ65 6316 6182.
E-mail address: wang_cun@ices.a-star.edu.sg (C. Wang).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.03.007

W. Rusli et al. / Journal of Organometallic Chemistry 696 (2011) 2414e2419
2415
towards the Lewis acidity of TiCl4 or ZrCl4, radical condition and/or
high temperature used.
Cl
Cl
Si
Ti
We used a modified metathesis method by using less reactive
and more selective reagents TiCl2(NMe2)2 and ZrCl2(NMe2)2 [11]
(Scheme 2). Reaction of the dilithium salt 5 with one equivalent
of TiCl2(NMe2)2 in THF led to the very pure titanium diamide 6a in
a 91% yield. The zirconium analogue 6b was obtained similarly in
a 67% yield by the treatment of 5 with ZrCl2(NMe2)2 which was
formed in situ from stoichiometric amount of ZrCl4(THF)2 and Zr
(NMe2)4. Group 4 metal chlorides are more desirable in catalysis
and the formation of other derivatives. Chlorination of CGC amides
to their chlorides are mostly achieved by using HCl, ClSiMe3,
Cl2SiMe2 [11,12]. HCl can induce the decomposition of 6a and 6b.
ClSiMe3 and Cl2SiMe2 are not strong enough to bring the reaction of
6a to 7a completely even when excess amount was added under
heating at 50 ꢀC overnight. Only mono chlorination product was
found on an NMR scale reaction. Complete transformation to 7a
was achieved by the treatment of 6a with 1.5 equivalents of BCl3 at
room temperature. Large excess of BCl3 also induced the decom-
position of 6a. The zirconium chloride 7b was formed on an NMR
scale reaction of 6b with excess of Cl2SiMe2 in C6D6 under 50 ꢀC
overnight, but decomposed or polymerized products were found
when prepared on a larger scale.
N
7a
Fig. 1. The titanium CGC catalyst 7a bearing a styrene unit to the nitrogen atom.
Me2SiCl2
LiCl
n-BuLi
Si
Cl
Li
1
2
Li
HN
(3)
2equiv. n-BuLi
Li
Li
Si
Si
NH
0.7THF
THF
LiHCl
In solution, complexes 6a, 6b, 7a and 7b exhibit NMR spectra
typical for symmetric rigid constrained half metallocenes. Two sets
of 1H NMR signals of the diastereotopic pairs of C5(CH3)4 hydrogens
were found for each of the above complexes (for example, 6a:
N
4
5
d
2.09, 1.85). They also feature a single Si-(CH3)2 1H NMR signal (6a:
0.67). The up-field shift of the ipso carbon in the Cp ring is the
Scheme 1. Ligand synthesis.
d
typical behaviour of constrained metallocene systems (6a:
d 102.1,
about 38 ppm lower than that of (C5Me4Si Me3)TiCl3 [13]). One
possible explanation is that the exocyclic bond of the Cp ring is not
in the plane of the Cp, and the Cp ring adopts an unsymmetrical
coordination mode to the metal centre. The negative charge of the
Cp ring is not shared equally among the five carbons, but is much
higher at the bridged one. More information was obtained by the
determination of X-ray single crystal structures of 6a and 6b.
mono-substituted product 2 according to literature [1c]. Further
substitution reaction of 2 with lithium 4-vinylanilinide (3) followed
by double deprotonation with n-BuLi in tetrahydrofuran yielded
the dilithium salt as THF adduct (5). We did not see the anionic
polymerization of 3, 4 and 5. The stability could come from the
negative charge on nitrogen atom which may prevent the addition
of n-BuLi to the styrene unit to form a less stable dianionic species.
2.3. X-ray diffraction studies of the single crystals of 6a and 6b
2.2. Synthesis of titanium and zirconium complexes
Single crystals for X-ray structure analysis were obtained from 6a
and 6b by the slow diffusion of pentane vapour to their solutions in
toluene at ꢁ25 ꢀC (Fig. 2, Fig. 3 and Table 1). The structure of 6awill be
discussed in detail to outline the general characteristics of this class of
compounds. In the crystal 6a, the titanium atom is in a pseudo-
tetrahedral environment surrounded by the CpSiN and the amido
ligands. The typical feature of 6a is its constrained nature of frame-
work formed by the CpSiN ligand. The connecting vector C1eSi1 is
bent out of the Cp plane towards the metal centre, as shown by the
corresponding angle (Cp(centroid)eC1eSi1: 151.63ꢀ). The con-
strained-geometry feature in 6a is also well explained by the Cp
(centroid)eTileN angles: Cp(centroid)eTi1eN1 (104.60ꢀ) is much
There are three basic synthesis routes to CGC catalysts:
metathesis, metallation and template approach [3]. Direct
metathesis of the dilithium salts with TiCl4/ZrCl4 or their THF
adducts usually gave very low yields. Modification of this method
by applying the metathesis with TiCl3(THF)3 followed by PbCl2
oxidation gave better results in terms of yield and reproducibility
[9]. Metallation by amine or alkane elimination is another efficient
method for the synthesis of CGC catalysts. Template approach has
the advantage of the late introduction of the amido fragment giving
way to broad catalyst screenings [10]. But all of these methods are
not applicable in our case because of the styrene’s high sensitivity
NMe2
NMe2
M
Si
Cl
Cl
M
Si
BCl3
MCl2(NMe2)2
Li
N
N
Si
0.7 THF
or Me2SiCl2
N
Li
6a
7a
(M = Ti)
(M = Ti)
(M = Zr)
5
7b
6b (M = Zr)
Scheme 2. Synthesis of the titanium and zirconium complexes.

2416
W. Rusli et al. / Journal of Organometallic Chemistry 696 (2011) 2414e2419
Table 1
Summary of crystallographic data for compounds characterized by X-ray diffraction
study.
6a
6b
Mol. formula
C23H37N3SiTi
431.55
110.15
P2(1)/n
Monoclinic
12.265(3)
15.487(3)
12.391(3)
90
92.17(3)
90
2352.0(8)
4
C23H37N3SiZr
474.87
110.15
P2(1)/n
Monoclinic
12.404(3)
15.546(3)
12.516(3)
90
91.25(3)
90
2413.0(8)
4
Mol. weight
Temperature/K
Space group
Crystal system
a/Å
b/Å
c/Å
ꢀ
ꢀ
ꢀ
/
a
/
b
/
g
Volume/Å3
Z
Dc/g cmꢁ3
1.219
0.428
1.307
0.518
m
/mmꢁ1
Reflection collected
Unique reflections
Parameters varied
Goodness-of-fit
R (int)
33104
5837
263
1.140
0.0261
0.0471
0.1281
0.755 and ꢁ0.561
17185
5911
263
1.176
0.0290
0.0454
0.1226
1.095 and ꢁ0.679
R1 (I > 2s(I))
Fig. 2. View of the molecular structure of 6a. Selected bond lengths (Å) and angles (ꢀ):
C1eC2 1.448(2), C2eC3 1.404(2), C3eC4 1.430(2), C4-C5 1.411(2), C1eC5 1.432(2),
TieN1 2.032(1), TieN2 1.927(2), TieN3 1.913(2), Si1eC1 1.865(2), Si1eN1 1.744(2),
C18eC19 1.320(3), Cp(centroid)eTi1 2.083, Si1eN1eC12 125.95(11), Si1eN1eTi1
101.66(7), C12eN1eTi1132.29(11), Cp(centroid)eTi1eN1104.60, Cp(centroid)eC1eSi1
151.63, C1eSi1eN1 93.30(7).
wR2 (all data)
Largest diff. peak and hole e Åꢁ3
in the same plane (as seen from the dihedral angles’ values:
Ti1eN3eC12eC13 (169.38ꢀ), C16eC15eC18eC19 (175.10ꢀ)).
smaller than the Cp(centroid)eTi1eN2 (122.44ꢀ) and Cp(centroid)e
Ti1eN3 (116.14ꢀ). The planarity for N1 (the sum of three angles
around N1 is 359.9ꢀ) suggests a strong interaction between the
2.4. Immobilization of 7a on polystyrene
7a can be incorporated into polystyrene by its radical copoly-
merization with styrene using azobisisobutyronitrile (AIBN) as the
initiator (Scheme 3). To confirm that only the vinyl group in 7a is
active for the radical polymerization, a control experiment was
monitored with the analogous Me2Si(C5Me4)(NPh)TiCl2 (9) under
same conditions, and no evident reaction was found. The comple-
tion of the reaction was easily confirmed with the help of 1H NMR
spectroscopy that the signals of vinyl groups disappeared at the
range of 5.0e6.5 ppm. A GPC analysis of the immobilized complex 8
shows that it has a uniform composition as seen from the very
narrow molecular weight distribution with a PDI value of 2.0
(Mn ¼ 11402, Mw ¼ 22812). The determination of titanium content
in 8 was investigated with ICP and XPS [6e], but no satisfactory
results were obtained. The titanium content in the polystyrene
support (10.5 mg Ti/g) was confirmed using 1H NMR spectroscopy
by the individual integration of the proton signals of CpCH3 and
phenyl groups of 7, and this result was very close to the expected
value based on the calculation of the ratio of starting materials. The
zirconium complex 6b was not supported on styrene for its low
stability and very low activity in the copolymerization of ethylene
with 1-octene.
ligand’s nitrogen atom with titanium metal centre through a
s-p
bonding mode. The conjugation of this -bonding is even extended to
p
the phenyl ring and vinyl group in the styrene unit as they are almost
Cl
Cl
Cl
Si
Ti
Ti
Cl
Si
N
N
free radical polymerization
AIBN as catalyst
Fig. 3. View of the molecular structure of 6b. Selected bond lengths (Å) and angles (ꢀ):
C1eC2 1.438(3), C2eC3 1.413(4), C3eC4 1.426(4), C4-C5 1.414(3), C1eC5 1.451(3),
Zr1eN1 2.170(2), Zr1eN2 2.061(2), Zr1eN3 2.038(2), Si1eC1 1.875(3), Si1eN11.740(2),
C18eC19 1.318(4), Cp(centroid)eZr1 2.218, Si1eN1eC12 126.39(17), Si1eN1eZr1
102.91(9), C12eN1eZr1 130.69(16), Cp(centroid)eZr1eN1 99.78, Cp(centroid)eC1eSi1
154.25, C1eSi1eN1 94.97(10).
m
n
7a
8
Scheme 3. Immobilization of 7a on polystyrene.

W. Rusli et al. / Journal of Organometallic Chemistry 696 (2011) 2414e2419
2417
d
Table 2
2.5. Catalytic copolymerization of ethylene with 1-octene
Ethylene/1-octene copolymerization using the polymerizable catalysts.a
Entry Compounds g(copol) Activityb Ethene/1-octenec Mn
Mw/Mn
1.7
5588 38
d
The complexes 6a, 6b, 7aand 8 gave active homogeneouscatalysts
for the copolymerization of ethylene with 1-octene when treated
with excess methylalumoxane (MAO). Preliminary polymerization
results with 7a showed that large excess of MAO was required to
activate the catalyst. High temperature was also beneficial for the
efficient catalyst activation. For the purpose of comparison, we also
tested the analogous catalyst Me2Si(C5Me4)(NPh)TiCl2 (9) and the
bench mark CGC catalyst Me2Si(C5Me4)(t-BuN)TiCl2 (10) (Fig. 4). The
results are summarized in Table 2. Although we could not isolate 7b,
the diamido zirconium 6b can still be transformed to active species
using excess MAO based on the previous results [14]. This is also true
for 6a and 7a which gave similar copolymer products in terms of
molecular weight, molecular weight distribution and comonomer
content, except for the lower activity obtained with 6a (Table 2, entry
1 and 3). These results suggest that 6a and 7a can be transformed into
similaractivespeciesundertheactivationoflargeexcessofMAO.6bis
not good for the incorporation of 1-octene to polyethylene, which is
consistent with other findings that the zirconium based CGC systems
are less effective than their titanium counterparts in the copolymer-
ization [1e,1f,2a,11]. The low activity obtained with 6b may be due to
its low stability under the polymerization conditions. 7a is compa-
rable to its analogue 9 and was highly active and effective for the
incorporation of comonomer 1-octene both under low and high
pressure of ethylene. Compared to the bench mark catalyst 10, 7a has
a higher capacity in the incorporation of 1-octene but with a lower
activity. The immobilized catalyst 8 showed low activity and low
incorporation of 1-octene in the product. The closeness of the metal
centres to the support in 8 may prevent the easy access of activator
and monomers to the active sites. The broad molecular weight
distribution of the product obtained with 8 indicates the multi-site
property of the immobilized catalyst.
1e
2
6a
6b
7a
7a
8
1.42
0.23
3.65
17.1
3.03
18.2
81.5
426
6.9
1095
513
91
2.9
75
12919
3e
4
2.8
3.0
7.6
3.5
7.4
10014
15138
5137 17
14557
29325
1.9
3.1
5
6
7
9
10
546
2445
3.1
4.1
a
Conditions: 150 mL of toluene, 50 mL of 1-octene, 20 mmol of [M], 12 mL of MAO
(1.7 M in toluene), Al/M: 1000, 10 bar of ethylene, 90 ꢀC, 10 min.
b
Catalyst activities in g(copolymer)/((mmol of metal) h bar).
c
Molar monomer ratio in the copolymer determined by 13C NMR spectroscopy.
d
Determined by GPC.
1 bar of ethylene.
e
scan technique. Data was collected and processed using Crystal-
Clear (Rigaku) software. The structure was solved by direct
methods (SHELXS-97) and refined on F2 against all reflections
(SHELXL-97) [16]. A summary of crystallographic data can be found
in Table 1. All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were generated geometrically and allowed to ride
on their parent heavy atoms and refined isotropically. ORTEP
diagrams of the two structures were drawn with thermal ellipsoids
at 30% probability.
3.3. Synthesis of ligand and complexes
3.3.1. Lithium 4-vinylanilinide (3)
4-vinylaniline (2.38 g, 20.0 mmol) was dissolved in 10 mL of THF
and cooled to 0 ꢀC with an ice-water bath. n-BuLi (1.6 M in hexane,
12.5 mL, 20.0 mmol) was added dropwise while white powder was
precipitated. The precipitated white powder was isolated by
filtration and dried under vacuum to give the product as THF (1.34
equivalents) adduct. Yield: 3.05 g, 13.8 mmol, 69%. 1H NMR
3. Experimental section
(400 MHz, DMSO-d6, 295 K):
d
6.57 (d, 3JHH ¼ 8.4 Hz, 2H, Ph), 6.21
3
3
(dd, JHH ¼ 10.6 Hz, JHH ¼ 17.6 Hz, 1H, CH]CH2), 5.82 (d,
3.1. General considerations
3JHH ¼ 8.4 Hz, 2H, Ph), 4.79 (dd, JHH ¼ 17.6 Hz, JHH ¼ 1.6 Hz, 1H,
3
2
3
2
CH]CH2), 4.25 (dd, JHH ¼ 10.6 Hz, JHH ¼ 1.6 Hz, 1H, CH]CH2),
All manipulations were carried out under a dry argon atmo-
sphere using standard Schlenk techniques or in a glovebox.
Solvents were dried and purified with MBRAUN solvent purifica-
tion system. MAO, 4-vinylaniline, Zr(NMe2)4, Ti(NMe2)4 and BCl3
were purchased and used as received. TiCl2(NMe2)2 [15], 2 [1c], 9
[1e] and 10 [1e] were prepared according to the literature proce-
dures. NMR spectra were recorded on a Bruker 400 MHz spec-
3.60 (m, a-THF), 1.76 (m, b-THF).
3.3.2. ((Tetramethylcyclopentadienyl)dimethylsilyl)(4-vinylphenyl)
amine (4)
((Tetramethylcyclopentadienyl)dimethylsilyl)chloride
(2)
(1.22 g, 5.68 mmol) was dissolved in 5 mL of THF and cooled to 0 ꢀC
with an ice-water bath and then a solution of 3 in 10 mL of THF was
added slowly. After the reaction mixture was stirred for 2 h at RT, all
volatiles were removed under vacuum and the residue was
extracted with pentane (2 ꢂ 10 mL). Pentane was removed from the
extraction under vacuum and the product was left as yellow oil
which was used directly without further purification. 1H NMR
trometer. Chemical shifts are reported in d
, referenced to 1H (of
residual protons) and 13C signals of deuterated solvents as internal
standards. Elemental analysis was performed on EuroEA3000
series CHNS analyzer.
3.2. X-ray crystal structure analysis
(400 MHz, C6D6, 295 K) for the major isomer:
d 7.23
(d, 3JHH ¼ 8.8 Hz, 2H, Ph), 6.80 (dd, 3JHH ¼ 10.8 Hz, 3JHH ¼ 17.6 Hz,1H,
CH]CH2), 6.53 (d, 3JHH ¼ 8.8 Hz, 2H, Ph), 5.60 (dd, 3JHH ¼ 17.6 Hz,
2JHH ¼ 1.6 Hz, 1H, CH]CH2), 5.05 (dd, 3JHH ¼ 10.8 Hz, 2JHH ¼ 1.6 Hz,
1H, CH]CH2), 3.12 (s, 1H, CpH), 3.06 (s, 1H, NH), 1.90, 1.81 (each s,
each 6H, CpCH3), 0.07(s, 6H, Si(CH3)2). 13C{1H}NMR (100 MHz, C6D6,
Data sets were collected with a Rigaku Saturn 70 CCD diffrac-
tometer at 110 K with graphite monochromated Mo Ka radiation
¼ 0.71070 Å). Absorption correction was done using the multi-
(l
295 K): d 149.8 (CeN), 139.6 (CH]CH2), 138.8 (Cp), 134.9 (Cp), 130.7
Cl
Cl
Cl
Cl
(CeCH¼CH2), 130.4 (Ph), 119.2 (Ph), 112.0 (CH]CH2), 57.3 (ipso-Cp),
Si
Ti
Si
Ti
N
N
16.7, 13.7 (CpCH3), 0 (Si(CH3)2).
3.3.3. Dilithium ((tetramethylcyclopentadienyl)dimethylsilyl)(4-
vinylphenyl)amide (5)
9
10
The above obtained product 4 was dissolved in 10 mL of THF and
Fig. 4. Analogous complex 9 and the bench mark catalyst 10.
cooled to 0 ꢀC n-BuLi (1.6 M in hexane, 6.73 mL, 10.8 mmol) was

2418
W. Rusli et al. / Journal of Organometallic Chemistry 696 (2011) 2414e2419
added slowly. After the reaction mixture was stirred for 5 h at RT,
THF was removed and the residue was treated with 20 mL of
pentane. The precipitated product was isolated by filtration and
dried under vacuum to give pale brown solid. Yield: 1.93 g,
5.36 mmol, 94% from 2. Although there was no satisfactory 1H NMR
spectrum obtained in DMSO-d6 due to the formation of aggregates,
the content of THF (0.7 equivalent) in the product could still be
determined by the individual integration of the proton signals of
CpCH3 (2.0e1.8 ppm) and THF at 3.60 ppm.
and dried under vacuum. Yield: 680 mg, 1.64 mmol, 80%. Anal.
Calcd. for C19H25Cl2NSiTi: C 55.09, H 6.08, N 3.38. Found: C 55.08, H
6.10, N 3.30. 1H NMR (400 MHz, C6D6, 295 K):
d 7.30 (d,
3
3JHH ¼ 8.4 Hz, 2H, Ph), 7.23 (d, JHH ¼ 8.4 Hz, 2H, Ph), 6.55 (dd,
3
3JHH
¼
10.8 Hz, JHH
¼
17.6 Hz, 1H, CH]CH2), 5.55 (dd,
3JHH ¼ 17.6 Hz, 2JHH ¼ 1.2 Hz, 1H, CH]CH2), 5.02 (dd, 3JHH ¼ 10.8 Hz,
2JHH ¼ 1.2 Hz, 1H, CH]CH2), 2.03, 2.01 (each s, each 6H, CpCH3),
0.45 (s, 6H, Si(CH3)2). 13C{1H}NMR (100 MHz, C6D6, 295 K):
d 152.3
(CeN),142.0 (Cp),137.9 (Cp),136.80 (CH]CH2),134.0 (CeCH]CH2),
127.3 (Ph), 119.6 (Ph), 112.4 (CH]CH2), 105.4(ipso-Cp), 16.2, 13.1
(CpCH3), 2.72 (Si(CH3)2).
3.3.4. Bis(dimethylamido)(
tetramethylcyclopentadienyl-
h
5:(4-vinylphenylamidodimethylsilyl)
N)-titanium (6a)
k
TiCl2(NMe2)2 (0.62 g, 3.0 mmol) in 10 mL of THF was added to
a solution of the dilithium salt 5 (1.08 g, 3.0 mmol) in 5 mL of THF
at ꢁ78 ꢀC. After the reaction mixture was stirred for 5 h at RT. THF
was removed and the residue was extracted with toluene
(2 ꢂ 10 mL). Removal of toluene yielded red solid which was treated
with 20 mL of pentane and cooled at e 30 ꢀC overnight. The
precipitated product was isolated by filtration and dried under
vacuum to give brown solid. Yield: 1.18 g, 2.73 mmol, 91%. Suitable
X-ray crystals were obtained by slow diffusion of pentane into
a solution of 6a in toluene at ꢁ25 ꢀC. Anal. Calcd. for C23H37N3SiTi: C
3.3.7. (
tetramethylcyclopentadienyl-
h
5:(4-vinylphenylamidodimethylsilyl)
N)dichlorozirconium (7b)
k
10 mg of 6b was combined with 27 mg of Me2SiCl2 in 0.6 mL of
C6D6 in a J-Young NMR tube and heated at 50 ꢀC overnight. 1H NMR
3
(400 MHz, C6D6, 295 K):
d
7.31 (d, JHH ¼ 8.4 Hz, 2H, Ph), 7.23
(d, 3JHH ¼ 8.4 Hz, 2H, Ph), 6.64 (dd, 3JHH ¼ 10.8 Hz, 3JHH ¼ 17.6 Hz,1H,
CH]CH2), 5.60 (dd, 3JHH ¼ 17.6 Hz, 2JHH ¼ 1.2 Hz,1H, CH]CH2), 5.57
(dd, 3JHH ¼ 10.8 Hz, 2JHH ¼ 1.2 Hz, 1H, CH]CH2), 2.15, 1.87 (each s,
each 6H, CpCH3), 0.46 (s, 6H, Si(CH3)2). 13C{1H}NMR (100 MHz,
C6D6, 295 K):
d 150.4 (CeN), 137.4 (CH]CH2), 136.8 (Cp), 133.0
64.02, H 8.64, N 9.74. Found: C 64.34, H 8.74, N 9.21. 1H NMR
(CeCH¼CH2), 132.5 (Cp), 127.9 (Ph), 123.1 (Ph), 112.2 (CH]CH2),
3
(400 MHz, C6D6, 295 K):
d
7.39 (d, JHH ¼ 8.4 Hz, 2H, Ph), 6.95 (d,
111.0 (ipso-Cp), 16.1, 12.5 (CpCH3), 3.31 (Si(CH3)2).
3JHH ¼ 8.4 Hz, 2H, Ph), 6.75 (dd, 3JHH ¼ 10.8 Hz, 3JHH ¼ 17.6 Hz, 1H,
CH]CH2), 5.65 (dd, 3JHH ¼ 17.6 Hz, 2JHH ¼ 1.2 Hz,1H, CH]CH2), 5.05
3.4. Immobilization of 7a on polystyrene
3
2
(dd, JHH ¼ 10.8 Hz, JHH ¼ 1.2 Hz, 1H, CH]CH2), 2.96 (s, 12H, N
(CH3)2), 2.09,1.85 (each s, each 6H, CpCH3), 0.67 (s, 6H, Si(CH3)2). 13
{1H}NMR (100 MHz, C6D6, 295 K):
154.3 (CeN), 137.7 (CH]CH2),
C
7a (50 mg, 120
mmol), freshly dried and distilled styrene
d
(500 mg, 4.8 mmol), and AIBN (0.2 M in toluene, 1.2 mL, 240
mmol)
129.4 (CeCH¼CH2), 129.0 (Cp), 127.4 (Ph), 126.6 (Cp), 120.3 (Ph),
109.6 (CH]CH2), 101.1(ipso-Cp), 43.1 (N(CH3)2), 13.9, 10.9 (CpCH3),
3.75 (Si(CH3)2).
were combined in a Schlenk flask and heated at 80 ꢀC for 14 h. The
completion of the reaction was monitored with the help of 1H NMR
spectroscopy where the signals of vinyl groups disappeared in the
range of 5.0e6.5 ppm. All the volatiles were removed, and the
residue was washed with pentane and dried under vacuum to give
408 mg dry powder. A GPC analysis of the immobilized complex 7
shows it has a narrow molecular weight distribution with a PDI
value of 1.6 (Mn ¼ 7693, Mw ¼ 12657). The titanium content in 7
(10.5 mg Ti/g) was determined by the 1H NMR analysis.
3.3.5. Bis(dimethylamido)(
tetramethylcyclopentadienyl-
h
5:(4-vinylphenylamidodimethylsilyl)
N)-zirconium (6b)
k
ZrCl2(NMe2)2 (2.0 mmol) was formed in situ by mixing
ZrCl4(THF)2 (377 mg, 1.0 mmol) and Zr(NMe2)4 (267 mg, 1.0 mmol)
in 5 mL of THF and stirred at RT for 2 h. A solution of the dilithium
salt 5 (720 mg, 2.0 mmol) in 5 mL of THF was then added at 0 ꢀC.
After the reaction mixture was stirred for 2 h at RT. THF was
removed and the residue was extracted with pentane (2 ꢂ 10 mL).
The pentane extract was concentrated to about 5 mL and cooled
at ꢁ30 ꢀC overnight. The precipitated yellow crystals were isolated
by filtration and dried under vacuum. Yield: 632 mg, 1.33 mmol,
67%. Suitable X-ray crystals were obtained by slow diffusion of
pentane into a solution of 6b in toluene at ꢁ25 ꢀC. Anal. Calcd. for
3.5. Catalytic copolymerization of ethylene with 1-octene
A 1 L Büchi stainless steel autoclave with a catalyst reservoir and
magnetic stirrer was evacuated and filled with argon three times
before it was charged with 150 mL of toluene, 50 mL of 1-octene,
and 12 mL of MAO (1.7 M in toluene). A precise amount of catalyst
(20 mmol) was dissolved in 5 mL of toluene and then loaded into the
C23H37N3SiZr: C 58.17, H 7.85, N 8.85. Found: C 57.88, H 7.94, N 7.96.
reservoir. The stirrer speed was adjusted to 500 U/min and the
autoclave was thermostated at 90 ꢀC while the solution was satu-
rated with ethylene at 10 bar After the solution was saturated with
ethylene, the catalyst solution in the chamber was introduced
directly into the autoclave. The polymerization reaction was
stopped by terminating the flow of ethylene with and quenching it
with 20 mL of methanol after 10 min. The reaction mixture was
poured into a larger beaker and treated with acidified methanol
and water. The organic phase was separated and washed with
water. The toluene solution was concentrated by using a rotary
evaporator and then the residue was dried overnight at 60 ꢀC in
a vacuum oven until a constant weight was obtained.
3
1H NMR (400 MHz, C6D6, 295 K):
d
7.35 (d, JHH ¼ 8.4 Hz, 2H, Ph),
3
3
6.97 (d, JHH ¼ 8.4 Hz, 2H, Ph), 6.71 (dd, JHH ¼ 10.8 Hz,
3JHH ¼ 17.6 Hz, 1H, CH]CH2), 5.61 (dd, 3JHH ¼ 17.6 Hz, 2JHH ¼ 1.2 Hz,
1H, CH]CH2), 5.03 (dd, 3JHH ¼ 10.8 Hz, 2JHH ¼ 1.2 Hz, 1H, CH]CH2),
2.82 (s, 12H, N(CH3)2), 2.15, 1.87 (each s, each 6H, CpCH3), 0.69 (s,
6H, Si(CH3)2). 13C{1H}NMR (100 MHz, C6D6, 295 K):
d 153.1 (CeN),
137.6 (CH]CH2), 129.1 (CeCH¼CH2), 128.7 (Cp), 127.7 (Ph), 124.9
(Cp), 121.2 (Ph), 109.6 (CH]CH2), 102.1(ipso-Cp), 47.9 (N(CH3)2),
14.3, 11.8 (CpCH3), 4.21 (Si(CH3)2).
3.3.6. (
tetramethylcyclopentadienyl-
h
5:(4-vinylphenylamidodimethylsilyl)
N)dichlorotitanium (7a)
k
BCl3 (1.0 M in toluene, 3.36 mL, 3.36 mmol) was added dropwise
to a solution of 6a (880 mg, 2.04 mmol) in 10 mL of toluene at 0 ꢀC.
After the reaction mixture was stirred for 2 h at RT, it was
concentrated to about 3 mL under vacuum and then 5 mL of
pentane was added. The reaction mixture was cooled to e 30 ꢀC
overnight. The precipitated red product were isolated by filtration
3.6. Characterization of polymers
1H and 13C NMR experiments of copolymers were carried out in
d2-tetrachloroethane at 100 or 120 ꢀC for the solid products and in
d6-benzene for waxy or oily products at room temperature on
Bruker 400 MHz spectrometer. Molar monomer ratio in the

W. Rusli et al. / Journal of Organometallic Chemistry 696 (2011) 2414e2419
2419
copolymer was determined by the integration of 13C NMR signals
[17]. Molecular weights and polydispersities of polymers were
obtained by GPC analysis (Varian PL-GPC 220 equipped with a triple
detection system) with two Plgel Olexis columns (300 ꢂ 7.5 mm,
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using polystyrene standards as references.
Acknowledgements
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We thank the Institute of Chemical and Engineering Sciences,
A*STAR (Agency for Science, Technology and Research, Singapore)
for financial support.
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Appendix A. Supplementary material
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(2005) 4760.
CCDC 804057 (6a) and 804058 (6b) contain the supplementary
crystallographic 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.
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