Syntheses of polymethylene bridged dinuclear zirconocenes and investigation of their polymerisation activities

Article abstract of DOI:10.1016/S0022-328X(98)01085-7

The polymethylene bridged dinuclear zirconocenes [(CH₂)_n (C₅H₄)₂][(C₉H₇)ZrCl ₂]₂ (n=3 (10), 5 (11), 7 (12), 9 (13)) have been synthesised by treating not on

Full text of DOI:10.1016/S0022-328X(98)01085-7

Journal of Organometallic Chemistry 580 (1999) 90–97
Syntheses of polymethylene bridged dinuclear zirconocenes and
investigation of their polymerisation activities
Seok Kyun Noh a,*, Jongmun Kim a, Jaehoon Jung a, Choon Sup Ra b, Dong-ho Lee c,
Hun Bong Lee c, Sang Won Lee d, Wan Soo Huh d
a School of Chemical Engineering and Technology, Yeungnam Uni6ersity, 214-1 Dae-dong, Kyongsan 712-749, South Korea
b Department of Chemistry, Yeungnam Uni6ersity, 214-1 Dae-dong, Kyongsan 712-749, South Korea
c Department of Polymer Science, Kyungpook National Uni6ersity, Taegu 702-701, South Korea
d Department of Chemical Engineering, Soongsil Uni6ersity, Seoul 156-743, South Korea
Received 24 August 1998
Abstract
The polymethylene bridged dinuclear zirconocenes [(CH2)n (C5H4)2][(C9H7)ZrCl2]2 (n=3 (10), 5 (11), 7 (12), 9 (13)) have been
synthesised by treating not only the respective disodium salts of the ligands with two equivalents of (C9H7)ZrCl3 in THF, but also
the distannylated derivatives of the ligands with two equivalents of (C9H7)ZrCl3 in toluene. All complexes are characterised by 1H-
and 13C-NMR and mass spectrometry and elemental analysis. It turned out that the values of Dl=[ld−lp], the chemical shift
difference between the distal (ld) and proximal (lp) protons, for the produced dinuclear compounds (0.1 for 10 and 11, and 0.11
for 12 and 13) were smaller than the Dl values of the known polysiloxane bridged dinuclear compounds. The chemical shifts of
the bridgehead carbons in these complexes are about 135 ppm shifted downfield with respect to the other two resonances at
cyclopentadienyl ring (113.7 and 113.7 ppm, respectively). In order to investigate the catalytic properties of the dinuclear
complexes and mononuclear metallocenes, ethylene polymerisation has been conducted in the presence of MMAO. The most
important feature is that the polymethylene bridged dinuclear metallocenes represent enormously improved activities compared
with the activities from the corresponding mononuclear metallocene as well as the polysiloxane bridged dinuclear zirconocenes.
In addition, the influence of both the nature and length of the bridging ligand upon the reactivities of the dinuclear metallocenes
has also been observed. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Dinuclear complexes; Distannylated derivatives; Polymethylene bridged dinuclear zirconocenes
Recently a variety of dinuclear metallocene com-
pounds, which contain two mechanically linked metal-
locene units, have been prepared to examine their
catalytic properties since dinuclear complexes could be
potentially useful as a new polymerisation catalyst as-
cribed by the cooperative electronic and chemical inter-
action between two centres. Patterson and Royo
prepared a series of dinuclear metallocenes of titanium
and zirconium and revealed structural features of these
complexes [3]. For the first time, Mu¨lhaupt studied
olefin polymerisation behaviours of the phenylene
bridged dinuclear zirconocene and demonstrated differ-
ences between molecular weights of polypropylenes
1. Introduction
Group 4 metallocene complexes are of increasing
interest in relation to many catalytic reactions, particu-
larly in homogeneous olefin polymerisation [1]. As an
advantage over the conventional Ziegler–Natta system,
the metallocene catalyst system combines high activity
with the possibility of tailoring the polymer properties
such as molecular weight and molecular weight distri-
bution as well as stereochemistry through an appropri-
ate ligand design at the metal centre [2].
* Corresponding author.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01085-7

S.K. Noh et al. / Journal of Organometallic Chemistry 580 (1999) 90–97
91
from the dinuclear compound and those from the cor-
responding mononuclear compound [4]. Recently,
Green synthesised a variety of dimethylsilyl-bridged
dinuclear metallocenes with Group 4 metals and probed
catalytic properties of these complexes [5]. The notice-
able feature of his experiments is that the catalytic
activities and molecular weight of obtained polymer
vary according to the dinuclear metallocene used. In
1997, Corey synthesised a group of dinuclear metal-
locenes of titanium and zirconium to study catalytic
dehydrocoupling of PhSiH3 with the prepared metal-
locenes and analysed the results in terms of the relative
distance between the two metallocene units [6]. More
recently, Spaleck and Soga prepared new types of
bridged zirconocenes holding two ansa-zirconocenes via
bridging silicone atom and examined their polymerisa-
tion properties [7]. The first systematic polymerisation
study of the dinuclear metallocene was performed by us
with the polysiloxane-bridged dinuclear zirconocenes
[8]. Our contribution to the dinuclear metallocene area
was originated by the idea to design a dinuclear model
complex holding polysiloxane moiety in order to ex-
plore properties of the heterogenised metallocene on
silica surface. Over the last several years we have ac-
complished not only the synthesis and characterisation
of various new types of dinuclear metallocenes, but
have also probed the polymerisation behaviour of those
compounds. In the case of polysiloxane-bridged dinu-
clear zirconocenes, it was found that the polymerisation
activity increased in the order of the bridge length. In
addition, the dinuclear metallocenes possessing rela-
tively shorter bridging ligand, generate greater molecu-
lar weight polyethylenes than others. In our
understanding these findings clearly demonstrated that
the dinuclear metallocenes show not only distinguished
properties from the known well-defined mononuclear
metallocenes, but also a strong dependence upon the
length of the bridging ligand [8a]. Cooperative reactiv-
ity pattern of the dinuclear metallocenes may be depen-
dent upon the structure of the bridging ligand as well as
the relative distance between two metal centres. This
indicates that the nature of the bridging ligand could be
the third element to identify the characteristics of dinu-
clear metallocene together with the metal and cyclopen-
tadienyl derivatives.
2. Results and discussion
The preparation of the polymethylene bridged dinu-
clear metallocenes has been achieved via two reaction
procedures. Treating the dilithium salts of the ligands
5–8 with two equivalents of (C9H7)ZrCl3 in THF gives
the formation of the respective dinuclear zirconocenes
10–13. The reaction products, however, always con-
tained
a
considerable amount (about 30%) of
(C9H7)2ZrCl2, 14, along with the desired dinuclear
metallocene complexes. In contrast to the polysiloxane
bridged dinuclear complexes, the polymethylene
bridged dinuclear complexes exhibit very similar solu-
bility property to (C9H7)2ZrCl2. It turned out that
sublimation is the only way to get rid of compound 14
from the product mixtures. For this reason, the prepar-
ative route to make the dinuclear complexes between
the dilithium salts and (C9H7)ZrCl3 suffered from the
reduced yield of less than 10%. Attempts to prevent the
generation of 14 by controlling the reaction conditions
were unsuccessful. It was found that generation of 14
was caused by facile rearrangement of (C9H7)ZrCl3 to
(C9H7)2ZrCl2 in the presence of THF. As a conse-
quence, the dinuclear zirconocenes are invariably pro-
duced along with unwanted (C9H7)2ZrCl2 as long as the
reaction is performed in THF as a reaction medium.
However, the poor solubility of both the dilithium salts
and (C9H7)ZrCl3 prevents the use of other solvents
(Scheme 1).
Recently, Nifant’ev reported that distannylated bis(-
cyclopentadienes) can be conveniently applied to pre-
pare ansa-metallocenes [9]. We have investigated the
performance of his method in the synthesis of dinuclear
metallocenes. The expected major advantage of the
method using distannylated compounds as one of the
starting materials resides in the easy blocking of the
rearrangement pathway of (C9H7)ZrCl3 to (C9H7)2-
ZrCl2 due to the solvent substitution from THF to
On this basis included in this report is a description
of the synthesis and characterisations of a family of
polymethylene bridged zirconocene complexes of the
general formula [C5H4–(CH2)n–C5H4][Zr(C7H9)]2 (n=
3, 5, 7, 9) to examine the influence of the types of
bridging ligand on the catalytic behaviours of dinuclear
metallocene compared with the known polysiloxane
bridged complexes. Further, ethylene polymerisation
with these complexes in the presence of methylalumi-
noxane (MAO) is conducted.

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S.K. Noh et al. / Journal of Organometallic Chemistry 580 (1999) 90–97
toluene since the distannylated derivatives are soluble in
toluene. In a one-pot synthesis, the dilithium salts 5–8
were treated with two equivalents of trimethyltin chlo-
ride in diethyl ether to give quantitatively distannylated
compounds 15–18, respectively, which were then (after
removing diethyl ether) reacted with (C9H7)ZrCl3 in
toluene to give the polymethylene dinuclear zir-
conocenes 10–13. Remarkably, the products from the
reaction do not consist of a variable amount of
(C9H7)2ZrCl2 as we had observed in the direct reaction
of dilithium salts with (C9H7)ZrCl3 in THF. In addi-
tion, an added advantage of this route is an easy
observation of the reaction progress. During the reac-
tion, disappearance of the starting, insoluble
(C9H7)ZrCl3 can be seen clearly to give rise to the
formation of dinuclear products which are soluble in
toluene. Recrystallisation from toluene results in the
isolation of polymethylene bridged dinuclear zir-
conocenes 10–13 in improved yields of about 60%, as a
bright yellow solid (Scheme 2).
for 10 and 11 and 5.95 and 5.84 ppm for 12 and 13 with
a JH–H value of 2.7 Hz due to an AA%BB% system and
three chemical shifts around 1–2.5 ppm for the
methylene protons. The remaining assignments are
listed in Table 1. The magnitudes of Dl—the chemical
shift difference between the distal and proximal protons
on the cyclopentadienyl ring—of the prepared dinu-
clear zirconocenes display unprecedentedly small values
(0.1 for 10 and 11, 0.11 for 12 and 13) compared with
the known values. In the case of the polysiloxane
bridged dinuclear zirconocenes, the magnitudes of Dl
have been reported to increase steadily from 0.47 to 0.5
as the bridging ligand becomes longer [8b]. Although
Dl values of 12 and 13 are slightly bigger than those of
10 and 11, it is unlikely that this result can be consid-
ered as the same tendency as in the case of polysiloxane
bridged complexes. One simple interpretation is that the
Dl values appear to be very sensitive to not only the
type of free cyclopentadienyl derivative but also the
type of bridging ligand. In addition, these could be
another example to demonstrate that the Dl value
cannot be employed as an appropriate spectroscopic
parameter to predict modes of coordination. Recently
Royo mentioned that the chemical shift due to the
cyclopentadienyl bridgehead carbon atom of the
[Me2Si(C5H4)2]−2 anion seemed to be sensitive to the
The dinuclear compounds have been characterised by
1H- and 13C-NMR, mass spectrometry, and elemental
analysis. 1H-NMR spectra of the complexes 11–13
indicate the expected resonances for the bridging poly-
methylenediylbis(cyclopentadienyl) moiety which ap-
pear as two sets of pseudotriplets at 5.92 and 5.82 ppm
Scheme 1.

S.K. Noh et al. / Journal of Organometallic Chemistry 580 (1999) 90–97
93
Scheme 2.
the catalysts 10–13. As shown in Fig. 1, the increasing
rate with the polysiloxane bridged catalysts cannot be
comparable with that of the polymethylene bridged ones.
The second feature is that activity values of the catalysts
in this study are much greater than those of the polysilox-
ane bridged complexes as well as the corresponding
mononuclear metallocene (C5H5)(C9H7)ZrCl2. All the
prepared catalysts except 10, which hold a shortest
distance between two zirconocenes, exhibit higher activ-
ity than the mononuclear one. On the contrary no
catalyst with the polysiloxane bridge represents higher
activity than the mononuclear one. Furthermore, the
activity difference between two groups of dinuclear
zirconocenes is getting larger and larger as the bridge
becomes longer.
We think these results can be explained by electronic
and steric characteristics of the dinuclear zirconocenes.
It is generally accepted that the polymerisation activity
of metallocene increases with increasing electron density
at the active centre. In our experiments the activity of the
catalysts decreased in the order 13\12\11\10, which
indicated the dinuclear zirconocene with more (CH2)
units as a bridge represented greater activity. It is
reasonable that the more electron density delivered by the
existence of longer polymethylene bridge should stabilise
the active site to accelerate the rate of polymerisation.
Bimolecular deactivation process could also be sup-
pressed in connected metallocenes because of the remote-
ness of two active sites [12]. One thing that should be
pointed out is the fact that in spite of the presence of the
electron releasing polymethylene bridge, the catalyst 10
displays lower activity than the corresponding mononu-
clear zirconocene which has absolutely no substituent at
the Cp ring. We suppose, in this respect, the steric
congestion around the zirconium centres will prevail to
mode of coordination of the ligand [10]. For most
dinuclear metallocenes containing this group as a bridg-
ing ligand, the chemical shift of the bridgehead carbon
is found downfield from the other carbons at the cy-
clopentadienyl ring, whereas the opposite trend is ob-
served for similar ansa-mononuclear complexes although
this spectral feature cannot be applied as a general rule
to distinguish the bridging or chelating disposition of the
ligand. Very interestingly, this statement has been proved
to be very well in accord with the behaviour observed for
the dinuclear complexes in this study. The chemical shifts
of the bridgehead carbons in these compounds are shown
about 135 ppm shifted downfield with respect to the other
two resonances (l 117.3 and 113.7, respectively).
The dinuclear complexes 10–13 were employed for the
polymerisation of ethylene to investigate the catalytic
characteristics in the presence of MMAO ([Al]/Zr ratio
of 20 000) at 40°C. The polymerisation activity of the
catalysts decreased in the order 13(5550 kg of PE/mol of
Zr h atm)\12(4602 kg of PE/mol of Zr h atm)\
11(3884 kg of PE/mol of Zr h atm)\10(2573 kg of
PE/mol of Zr h atm). From a standpoint of the catalyst
activity there are some important points to be noted to
characterise the synthesised complexes. The prime fea-
ture is that the activity increases sharply as the bridging
ligand becomes longer. This behaviour is very well in
accord with the activity tendency observed with the
polysiloxane bridged dinuclear zirconocenes [8a]. Fig. 1
displays the relation between the number of atoms in the
bridging ligand and activities of the dinuclear
zi2rconocenes. It is remarkable that the activity increases
steeply and steadily with the number of atoms in the
bridging ligand from three methylenes to nine methyle-
nes. The addition of ca. one methylene unit in the bridge
exerts 500 kg of PE/mol of Zr h atm on activity among

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S.K. Noh et al. / Journal of Organometallic Chemistry 580 (1999) 90–97
represent the apparent activity of the dinuclear metal-
locene and not electronic effect as a consequence of the
close distance between two metal centres due to the
relatively short bridge length of three (CH2) units. On the
other hand, the dinuclear zirconocenes holding more
than five (CH2) units as a bridge exhibited greater activity
than the mononuclear metallocene. This outcome sug-
Table 1
Summary of 1H- and 13C-NMR dataa
Compound
Assignment 1H-NMR
13C-NMR
134.8b
[(C5H4)2(CH2)3]
[(C9H7)ZrCl2]2
C5H4
C9H7
5.92 (t, 2.7)
5.82 (t, 2.7)
7.66 (m)
7.27 (m)
117.4
126.2
126.1
125.5
124.2
29.4c
6.90 (t, 3.3)
6.50 (d, 3.3)
2.47 (t, 7.2)
1.44 (m)
CH2
Fig. 1. Variation of activity (kg PE/mol Zr h atm) with the number
of atm in bridging ligand. For number of atoms in the bridge=0,
catalyst=(Cp)(ind)ZrCl2. For number of atoms in the bridge=3,
(ꢀ) complex 10, (“) [O(SiMe2C5H4)2][(C9H7)ZrCl2]2. For number of
atoms in the bridge=5, (ꢀ) complex 11, (“) [O(SiMe2-
C5H4)2][(C9H7)ZrCl2]2. For number of atoms in the bridge=7, (ꢀ)
complex 12, (“), [O{O(SiMe2)2C5H4}2][(C9H7)ZrCl2]2. For number of
atoms in the bridge=9, (ꢀ) complex 13.
[(C5H4)2(CH2)5]
[(C9H7)ZrCl2]2
C5H4
5.92 (t,2.7)
135.5b
5.82 (t, 2.7)
117.3
113.7
126.2
126.1
125.5
124.1
102.7
29.8
C9H7
7.66 (m)
7.28 (m)
6.90 (t, 3.3)
6.49 (d, 3.3)
gests that the length of five (CH2) units would correspond
to the critical distance, that the electronic effect of the
bridge in catalytic properties of the dinuclear complexes
surpasses the steric hindrance between two metals.
CH2
2.47 (t, 6.6)
1.45 (m)
1.25 (m)
29.7
28.7
[(C5H4)2(CH2)7]
[(C9H7)ZrCl2]2
C5H4
5.95 (t,2.7)
135.8b
5.84 (t, 2.7)
117.3
113.7
126.1c
125.5
124.1
30.3
C9H7
CH2
7.66 (m)
7.27 (m)
6.90 (t, 3.3)
2.49 (t, 7.5)
1.42 (m)
30.0
1.21 (br)
29.1
28.9
[(C5H4)2(CH2)9]
[(C9H7)ZrCl2]2
C5H4
5.95 (t, 2.7)
5.84 (t, 2.7)
135.8b
117.3
113.7
126.1c
125.5
124.1
102.7
30.4
C9H7
CH2
7.66 (m)
7.27 (m)
6.90 (t, 3.3)
6.49 (d, 3.3)
2.49 (t, 7.5)
1.43 (m)
30.0
1.20 (m)
29.3
29.2c
3. Summary
a Chemical shifts are in ppm and solvent is CDCl3.
b Resonance assigned to bridgehead carbon.
c Overlapping of two carbon chemical shifts.
The polymethylene bridged dinuclear zirconocenes
10–13 have been synthesised via two procedures. The

S.K. Noh et al. / Journal of Organometallic Chemistry 580 (1999) 90–97
95
dinuclear products from the reaction of the dilithium
salts of the ligands with (C9H7)ZrCl3 was complicated
by the accompanying generation of (C9H7)2ZrCl2. How-
ever, the route using distannylated derivatives of the
ligands instead of the dilithium salts showed a remark-
able advantage over the route using lithium salts by the
blocking of (C9H7)2ZrCl2 generation. The dinuclear
toluene, hexane, and pentane were distilled from
sodium/benzophenone ketyl prior to use. Methylene
chloride was distilled from phosphorous pentoxide
prior to use. White filtering aid (Celite) was stored in a
130°C oven. CpLi, CpNa (2.5 mol solution in THF),
and TlOEt were used as purchased from Aldrich.
Modified methylaluminoxane (MMAO, Type-4, 6.4
wt.% Al, Akzo, USA) was used without further purifi-
cation. NMR spectra were recorded at 300 MHz on a
Bruker ARX-300 FT-NMR spectrometer. Metal con-
tent was measured by Jobin-Yvon 38 Plus ICP Emis-
sion Spectrometer. IR spectra were recorded on a
JASCO FT/IR-5300 spectrophotometer between 4000
and 200 cm−1. All the dimetallic salts (indenyl)ZrCl3
were synthesised according to literature methods
[3,8,11].
1
compounds have been characterised by H- and 13C-
NMR, mass spectrometry, and elemental analysis. The
magnitudes of Dl—the chemical shift difference be-
tween the distal and proximal protons on cyclopentadi-
enyl ring—of the prepared dinuclear zirconocenes,
display unprecedentedly small values (0.1 for 10 and 11,
0.11 for 12 and 13) compared with the known values.
This result demonstrates that the Dl values appear to
be very sensitive to not only the type of free cyclopenta-
dienyl derivative but also the type of bridging ligand.
The chemical shifts of the bridgehead carbons in these
compounds are shown about 135 ppm shifted downfield
with respect to the other two resonances (l 117.3 and
113.7, respectively). The dinuclear complexes 10–13
were employed in the polymerisation of ethylene to
investigate the catalytic characteristics in the presence
of MMAO ([Al]/Zr ratio of 20 000) at 40°C. The poly-
merisation activity of the catalysts decreased in the
order 13(5550 kg of PE/mol of Zr h atm)\12(4602 kg
of PE/mol of Zr h atm)\11(3884 kg of PE/mol of Zr
h atm)\10(2573 kg of PE/mol of Zr h atm). This
indicates that the activity increases sharply as the bridg-
ing ligand becomes longer. In addition, all the prepared
catalysts except 10, which hold a shortest distance
between two zirconocenes, exhibit higher activity than
the mononuclear one as well as the previously reported
polysiloxane bridged complexes. These results suggest
that the greater electron density delivered by the exis-
tence of a longer polymethylene bridge should stabilise
the active site to accelerate the rate of polymerisation.
In case of the catalyst 10, the steric congestion around
the zirconium centres is more pronounced to represent
the activity and not electronic effect as a consequence
of the close distance between two metal centres due to
the relatively short bridge length of three (CH2) units.
This outcome suggests that the length of five (CH2)
units would correspond to the critical distance that the
electronic effect of the bridge is subject to the catalytic
properties of the dinuclear complexes over the steric
hindrance between two metals.
4.1. Synthesis of [(CH2)3C5H4)2][(C9H7)ZrCl2]2, 10
Dilithium 1,3-dicyclopentadienylpropane (0.76 g,
4.08 mmol) was suspended in 50 ml of ether and cooled
to −40°C and 1.8 g (9 mmol) of trimethyltin chloride
was then added. The resulting mixture was allowed to
warm to room temperature and stirred for 5 h. After
removal of LiCl by filtration, the solvent was evapo-
rated to give yellow oil (1.9 g, 95%). The distannylated
derivative thus obtained was diluted in 50 ml of
toluene. Subsequently, 2.60 g of (indenyl)ZrCl3 was
added, and the mixture was taken to 80°C and stirred
for an additional 6 h. The yellow solution was sepa-
rated off and the resulting solution was then stored at
−70°C to recrystallise the product in 60% yields as a
yellow solid.
1H-NMR (CDCl3, 20°C, l ppm): 7.66 (m, 4H, C9H7),
7.27 (m, 4H, C9H7), 6.90 (t, 2H, 3.3 Hz, C9H7), 6.50 (d,
4H, 3.3 Hz, C9H7), 5.92 (t, 4H, 2.7 Hz, C5H4), 5.82 (t,
4H, 2.7 Hz, C5H4), 2.47 (t, 4H, 7.2 Hz, CH2), 1.44 (m,
2H, CH2). 13C-NMR (CDCl3, 20°C, l ppm): 126.2
(C9H7), 126.1 (C9H7), 125.5 (C9H7), 124.2 (C9H7), 102.2
(C9H7), 134.8 (C5H4), 117.4 (C5H4), 113.6 (C5H4), 29.4
(CH2). MS (m/e): 722 (11, M+), 607 (70, M+ –Ind),
463 (14, M+ –Ind–Cl4), 342 (88, (Cp)(Ind)ZrCl2), 170
(39,(Cp)2C3H6), 115 (41, Ind).
4.2. Synthesis of [(CH2)5C5H4)2][(C9H7)ZrCl2]2, 11
Dilithium 1,5-dicyclopentadienylpentane (0.88 g, 4.1
mmol) was suspended in 50 ml of ether and cooled to
−40°C, and 1.7 g (8.4 mmol) of trimethyltin chloride
was then added. The resulting mixture was allowed to
warm to room temperature and stirred for 5 h. After
removal of LiCl by filtration, the solvent was evapo-
rated to give yellow oil (1.87 g, 95%). The distannylated
derivative thus obtained was diluted in 50 ml of
toluene. Subsequently, 2.43 g of (indenyl)ZrCl3 was
added, and the mixture was taken to 80°C and stirred
4. Experimental
All reactions were carried out under a dry, oxygen-
free atmosphere using standard Schlenk techniques with
a double manifold vacuum line. Nitrogen gas was
purified by passage through a column of molecular
˚
sieve (4 A) and Drierite (8 mesh). THF, diethylether,

96
S.K. Noh et al. / Journal of Organometallic Chemistry 580 (1999) 90–97
for an additional 6 h. The yellow solution was sepa-
rated off and the resulting solution was then stored at
−70°C to recrystallise the product in 60% yields as a
yellow solid.
for an additional 6 h. The yellow solution was sepa-
rated off and the resulting solution was then stored at
−70°C to recrystallise the product in 60% yields as a
yellow solid.
1H-NMR (CDCl3, 20°C, l ppm): 7.66 (m, 4H, C9H7),
7.28 (m, 4H, C9H7), 6.90 (t, 2H, 3.3 Hz, C9H7), 6.49 (d,
4H, 3.3 Hz, C9H7), 5.92 (t, 4H, 2.7 Hz, C5H4), 5.82 (t,
4H, 2.7 Hz, C5H4), 2.47 (t, 4H, 6.6 Hz, CH2), 1.45 (m,
4H, CH2), 1.25 (m, 2H, CH2). 13C-NMR (CDCl3, 20°C,
l ppm): 126.2 (C9H7), 126.1 (C9H7), 125.5 (C9H7), 124.1
(C9H7), 102.7 (C9H7), 135.5 (C5H4), 117.3 (C5H4), 113.7
(C5H4), 29.8 (CH2), 29.7 (CH2), 28.7 (CH2). Anal.
Found: C, 52.54; H, 4.23. C33H32Cl4Zr2. Calc.: C,
52.64; H, 4.28%. MS (m/e): 750 (7, M+), 680 (10,
M+ –Cl2), 635 (15, M+ –Ind), 490 (15, M+ –Ind–Cl4),
198 (7, (Cp)2C5H10), 115 (100, Ind).
1H-NMR (CDCl3, 20°C, l ppm): 7.66 (m, 4H, C9H7),
7.27 (m, 4H, C9H7), 6.90 (t, 2H, 3.3 Hz, C9H7), 6.49 (d,
4H, 3.3 Hz, C9H7), 5.95 (t, 4H, 2.7 Hz, C5H4), 5.84 (t,
4H, 2.7 Hz, C5H4), 2.49 (t, 4H, 7.5 Hz, CH2), 1.43 (m,
4H, CH2), 1.20 (m, 10H, CH2). 13C-NMR (CDCl3,
20°C, l ppm): 126.1 (C9H7), 125.5 (C9H7), 124.1
(C9H7), 102.7 (C9H7), 135.8 (C5H4), 117.3 (C5H4), 113.7
(C5H4), 30.4 (CH2), 30.0 (CH2), 29.3 (CH2), 29.2 (CH2).
Anal. Found: C,54.93; H, 4.98. C37H40Cl4Zr2. Calc.: C,
54.69; H, 5.36. MS (m/e): 691 (5, M+ –Ind), 342 (5,
(Cp)(Ind)ZrCl2), 254 (3, (Cp)2C9H18), 115 (43, Ind).
4.5. Polymerisation
4.3. Synthesis of [(CH2)7C5H4)2][(C9H7)ZrCl2]2, 12
All operations were carried out under a nitrogen
atmosphere. In a 400 ml glass reactor the proper
amount of toluene and MMAO solution were intro-
duced sequentially, and then the system was saturated
with ethylene. With continuous flow of ethylene, the
polymerisation was initiated by injecting the solution of
the prepared dinuclear metallocenes. After 2 h poly-
merisation, polyethylene was precipitated in acidified
methanol.
Dilithium 1,7-dicyclopentadienylheptane (0.66 g, 2.4
mmol) was suspended in 50 ml of ether and cooled to
−40°C and 1 g (5 mmol) of trimethyltin chloride was
then added. The resulting mixture was allowed to warm
to room temperature and stirred for 5 h. After removal
of LiCl by filtration, the solvent was evaporated to give
yellow oil (1.3 g, 95%). The distannylated derivative
thus obtained was diluted in 50 ml of toluene. Subse-
quently, 1.60 g of (indenyl)ZrCl3 was added, and the
mixture was taken to 80°C and stirred for an additional
6 h. The yellow solution was separated off and the
resulting solution was then stored at −70°C to recrys-
tallise the product in 60% yields as a yellow solid.
1H-NMR (CDCl3, 20°C, l ppm): 7.66 (m, 4H, C9H7),
7.27 (m, 4H, C9H7), 6.90 (t, 2H, 3.3 Hz, C9H7), 6.49 (d,
4H, 3.3 Hz, C9H7), 5.95 (t, 4H, 2.7 Hz, C5H4), 5.84 (t,
4H, 2.7 Hz, C5H4), 2.49 (t, 4H, 7.5 Hz, CH2), 1.42 (m,
4H, CH2),1.21 (br, 6H, CH2). 13C-NMR (CDCl3, 20°C,
l ppm): 126.1 (C9H7), 125.5 (C9H7), 124.1 (C9H7). 102.7
(C9H7), 135.8 (C5H4), 117.3 (C5H4), 113.7 (C5H4), 30.3
(CH2), 30.0 (CH2), 29.1 (CH2), 28.9 (CH2). MS (m/e):
663 (5, M+ –Ind), 511 (5, M+ –Ind–Cl), 342 (5,
(Cp)(Ind)ZrCl2), 408 (21, M+ –Ind–Cl4), 226 (7,
(Cp)2C7H14), 115 (76, Ind).
Acknowledgements
The authors thank the Korea Science and Engineer-
ing Foundation (Grant 96-0502-01-01-3) for financial
support.
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