Living ethylene/norbornene copolymerisation catalyzed by titanium complexes having two pyrrolide-imine chelate ligands

Article abstract of DOI:10.1039/b202391a

Ethylene/norbornene copolymerisation behaviour of titanium complexes with two pyrrolide-imine chelate ligands is described.

Full text of DOI:10.1039/b202391a

Living ethylene/norbornene copolymerisation catalyzed by titanium
complexes having two pyrrolide-imine chelate ligands†
Yasunori Yoshida, Junji Saito, Makoto Mitani, Yukihiro Takagi, Shigekazu Matsui, Sei-ichi Ishii,
Takashi Nakano, Norio Kashiwa and Terunori Fujita*
R&D Centre, Mitsui Chemicals, Inc, 580–32 Nagaura, Sodegaura, Chiba, Japan.
E-mail: Terunori.Fujita@mitsui-chem.co.jp
Received (in Cambridge, UK) 7th March 2002, Accepted 1st May 2002
First published as an Advance Article on the web 17th May 2002
Ethylene/norbornene copolymerisation behaviour of tita-
nium complexes with two pyrrolide-imine chelate ligands is
described.
CH)C
4 3 2 2
H N] TiCl (complex 2), which were synthesised ac-
1
2
cording to the procedure reported in our previous paper.
Ethylene/NB copolymerisations were carried out with com-
plexes 1 and 2 using methylalumoxane (MAO) as a cocatalyst
at 25 °C under atmospheric pressure. The polymerisation results
are summarised in Table 1. Complexes 1 and 2 displayed very
high activities (complex 1; 576 kg polymer mol complex
complex 2; 2730 kg polymer mol complex
The increased interest in the development of new polymers
using well-defined transition metal complexes has resulted in
the introduction of a variety of high performance polymers such
as syndiotactic polystyrene (sPS), ethylene/styrene interpoly-
mers (ESI), elastomeric polypropylene, and cyclic olefin
copolymers (COC).1 ‡ Among these polymers, COC is one of
the most important engineering plastics which possess high
thermal stability and excellent optical properties (e.g., high
transparency and high refractive indices), and is thus used in
heat-resistant and optical applications. COC can be produced by
the copolymerization of cyclic olefins such as norbornene (NB)
with ethylene or a-olefins using various transition-metal based
catalysts (e.g., vanadium catalysts and group 4 metallocene
catalysts). Until now, a number of high performance catalysts
for the production of COC have been developed.4 There are,
however, only a few examples of catalysts (Tritto and
2
1 21
h ,
2
1 21
h ) and produced
amorphous polymers (Tg: entry 1; 130 °C, entry 2; 120 °C).§
–3
13
4j
Microstructural analyses using C NMR spectroscopy sug-
gest that the polymers are ethylene/NB copolymers produced
via vinyl-type polymerisation, with NB contents of 48.6 mol%
(complex 1) and 44.5 mol% (complex 2), respectively. The
distributions of the NB incorporated in the copolymers reveal
that the catalyst systems show a very high propensity to yield
alternating copolymers [complex 1; alternating part (–NB–
ethylene–NB–ethylene–NB–): 91%, isolated part (–ethylene–
NB–(ethylene) –; n ! 2): 9%, complex 2; alternating part: 91%,
n
,5
isolated part: 9%] (Fig. 1).¶ These practically alternating
copolymers contain similar amounts of meso and racemic –NB–
ethylene–NB– sequences (Table 1, entry 1; meso/racemic =
54.9/45.1, entry 2; meso/racemic = 53.8/46.2), indicating that
the alternating part in the copolymers are practically atactic
6
4b
coworkers and Cherdron et al. ) that form COC in a living
fashion.
Previously, we have described a strategy to develop new
olefin polymerisation catalysts on the basis of non-symmetric
bidentate ligands having moderate electron donating properties
though the catalyst precursor possesses C
microstructures of the copolymers arising from complexes 1
and 2 resemble that formed with the C
catalyst, Me
eoirregular alternating copolymers.
GPC analyses reveal that the copolymers possess very high
molecular weights (M ) of 127000 (complex 1) and 521000
(complex 2), respectively. However, more significantly, the
copolymers have extremely narrow molecular weight distribu-
2
symmetry. Thus, the
7
combined with transition metals. This approach has led to the
s
constrained geometry
which provides ster-
t
4i
discovery of high performance olefin polymerisation catalysts
2 4 2
Si(Me Cp)(NBu )TiCl ,
8
,9
10
based on phenoxy-imine,
indolide-imine, phenoxy-py-
ridine,11 or pyrrolide-imine
12,13
ligands combined with group 4
transition metal centres. In this paper, we describe the unique
catalytic properties of titanium complexes bearing two pyrro-
lide-imine chelate ligands, denoted PI Catalysts. These catalysts
promote living copolymerisation of ethylene with NB to
produce high molecular weight copolymers (COC) with
extremely narrow molecular weight distributions.
n
The titanium complexes (Scheme 1) employed in this study
are [2-(PhNCH)C H N] TiCl (complex 1) and [2-(CyN-
4 3 2 2
†
Electronic supplementary information (ESI) available: general procedures
and materials, ligand and complex syntheses and analyses, polymerisation
13
procedure, polymer analyses, C NMR spectra for polymers (entries 1 and
). See http://www.rsc.org/suppdata/cc/b2/b202391a/
2
Scheme 1
Table 1 Ethylene/NB copolymerisation results with complexes 1 and 2
Gas: C
2
2
H
4
/
Time/
min
Charged
NB/g
Yield/
mg
NB contentc/
mol%
1
Activitya
b
b
T
g
d/°C
Entry
Complex
2
N /L h
M
n
M /M
w n
1
2
3
4
5
6
1
2
1
2
1
2
50/0
50/0
0/50
0/50
100/0
2/100
10
10
20
20
5
10
10
10
10
0
96
455
0
0
500
18
576
2730
0
127000
521000
—
—
30000
50000
1.10
1.16
—
—
2.21
2.90
48.6
44.5
—
—
0
130
120
—
—
—
0
6000
106
10
0
0
—
a
Conditions: 25 °C, atmospheric pressure, complex: 1 mmol, cocatalyst; MAO (purchased from Albemarle) 1.25 mmol as Al, toluene 250 mL. kg polymer
mol-complex)2
1
21 b
(
(
n w n
h . M and M /M values were determined by GPC, equipped with refractive index (RI) detector, by using polystyrene calibration
entries 1 and 2) or polyethylene calibration (entries 5 and 6). NB contents were determined by C NMR. d
c
13
g
T measured by DSC.
1
298
CHEM. COMMUN., 2002, 1298–1299
This journal is © The Royal Society of Chemistry 2002

very high molecular weight copolymers having extremely
narrow molecular weight distributions with high activities. The
1
2
results described herein along with our previous reports
indicate that PI Catalysts have high potential for the production
of polymers which are difficult or impossible to prepare using
conventional Ziegler–Natta catalysts.
We thank Drs M. Mullins, M. Onda and A. Valentine for their
helpful discussions and suggestions.
Notes and references
‡
COC is commercially available from Mitsui Chemicals (APEL™) and
Ticona (TOPAS™).
2 2
Under the same conditions, Cp ZrCl did not produce any polymers,
§
indicating that complexes 1 and 2 possess high potential for the
Fig. 1 13C NMR spectrum for the ethylene/NB copolymer prepared by
complex 2/MAO (entry 2).
copolymerisation of ethylene with NB.
¶
The –NB–NB– sequences are not detected in the NMR for copolymers
produced by complexes 1 and 2.
The possibility cannot be ruled out that the active species are different
∑
tions (M
w
/M
n
; 1.10, 1.16). The M
w
/M
n
values suggest that
between ethylene homopolymerisation (non-living type active species) and
ethylene/NB copolymerisation (living type active species). Several stereoi-
somers of the complexes can exist as a consequence of different binding
geometries of the two non-symmetric ligands.
complexes 1 and 2/MAO catalyst systems may have the
characteristics of a living ethylene/NB copolymerisation under
the conditions employed.
The plots of M
time are shown in Fig. 2. The M
the polymerisation time while the narrow M
/M 1.07–1.15, complex 2; M /M 1.07–1.25) was retained
n
and M
w
/M
n
as a function of polymerisation
increased proportionally with
/M (complex 1;
1
2
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w
n
M
w
n
w
n
3
C. Janiak and P. G. Lassahn, Macromol. Rapid Commun., 2001, 22,
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metallocene catalysts which initiate living ethylene/NB copoly-
merisations to furnish monodisperse COC with very high
molecular weights (Max. M 800000). Considering that the
n
MAO used as the cocatalyst is a potential chain transfer agent,
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4
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represents one of the highest molecular weights among COCs
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medium and/or in the polymer chain is a requirement for living
copolymerisation since complexes 1 and 2 promote neither
ethylene nor NB polymerisation in a living fashion (entries
8
931.
3
–6). Preliminary DFT calculations suggest that the steric
5
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elimination and chain transfer to a cocatalyst) regarding the
complexes employed.∑
6
7
8
9
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2
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2
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Detailed mechanistic studies together with the synthesis of
COC with novel architectures are underway.
In summary, ethylene/NB copolymerisation behaviour of
titanium complexes with two pyrrolide-imine chelate ligands,
denoted PI Catalysts, has been introduced. These complexes
combined with MAO are capable of promoting room-tem-
perature living copoplymerisation of ethylene with NB to form
1
CHEM. COMMUN., 2002, 1298–1299
1299