Unbridged 1- and 2-substituted bis(silylindenyl) zirconium(IV) and hafnium(IV) dichloride complexes as catalyst precursors for ethylene polymerization

Article abstract of DOI:10.1016/j.poly.2017.07.028

Twelve unbridged metallocene dichloride complexes of the types [1-(4-XC₆H₄SiMe₂)-η⁵-Ind]₂MCl₂ and [2-(4-XC₆H₄SiMe₂)-η⁵-Ind]₂MCl₂ (X = Me, MeO, F; M = Zr, Hf) with differently 1- and 2-substituted indenyl ligands have been synthesized, characterized and applied for catalytic ethylene polymerization. After activation with methylaluminoxane (MAO), all complexes are catalysts for ethylene polymerization. However, in nearly all cases, the species with the silyl substituent in the 1-position show much higher activities than those with the same substituent in 2-position of the indenyl moiety. For instance, the MAO activated complex bis(η⁵-1-(dimethyl-4-tolylsilyl)idenyl) zirconium(IV) dichloride (3), displayed an almost five times higher activity (3980 kg PE/mol cat.h) than the isomeric bis(η⁵-2-(dimethyl-4-tolylsilyl)indenyl) zirconium(IV) dichloride (19)/MAO catalyst (870 kg PE/mol cat.h). The same trend was observed for the para-fluorophenyl silyl indenyl complexes 23 and 17. This behavior may be explained in a way that the same silyl substituent in position 2 can exert more steric hindrance around the metal center compared to the 1-substituted analogues. The GPC characterization of the produced polyethylenes showed that some of the resins have a bimodal molecular weight distribution indicating at least two different active sites that are involved in the polymerization process.

Full text of DOI:10.1016/j.poly.2017.07.028

Accepted Manuscript
Unbridged 1- and 2-substituted bis(silylindenyl) zirconium(IV) and hafni-
um(IV) dichloride complexes as catalyst precursors for ethylene polymerization
Mohamed E.M. Abdelbagi, Helmut G. Alt
PII:
S0277-5387(17)30519-3
DOI:
http://dx.doi.org/10.1016/j.poly.2017.07.028
POLY 12764
Reference:
Polyhedron
To appear in:
Received Date:
Revised Date:
Accepted Date:
25 May 2017
26 July 2017
28 July 2017
Please cite this article as: M.E.M. Abdelbagi, H.G. Alt, Unbridged 1- and 2-substituted bis(silylindenyl)
zirconium(IV) and hafnium(IV) dichloride complexes as catalyst precursors for ethylene polymerization,
Polyhedron (2017), doi: http://dx.doi.org/10.1016/j.poly.2017.07.028
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Revised manuscript
Unbridged 1- and 2-substituted bis(silylindenyl) zirconium(IV) and
hafnium(IV) dichloride complexes as catalyst precursors for ethylene
polymerization
Mohamed E. M. Abdelbagi, Helmut G. Alt*
Laboratorium für Anorganische Chemie, Universität Bayreuth
Postfach 101251, D-95440 Bayreuth, Germany
Keywords:
-
-
-
-
-
Unbridged bis(indenyl) complexes
Silyl substituents
Zirconium and hafnium complexes
Catalytic ethylene polymerization
Structure-property-relationships
* Corresponding author: Tel.: +49 921 43864.
E-mail address: helmut.alt@uni-bayreuth.de (H.G. Alt)
1

Abstract
Twelve unbridged metallocene dichloride complexes of the types [1-(4-XC6H4SiMe2)-
η5-Ind]2MCl2 and [2-(4-XC6H4SiMe2)-η5-Ind]2MCl2 (X = Me, MeO, F; M = Zr, Hf) with
differently 1- and 2- substituted indenyl ligands have been synthesized, characterized
and applied for catalytic ethylene polymerization. After activation with
methylaluminoxane (MAO), all complexes are catalysts for ethylene polymerization.
However, in nearly all cases, the species with the silyl substituent in the 1-position
show much higher activities than those with the same substituent in 2-position of the
indenyl moiety. For instance, the MAO activated complex bis(η5-1-(dimethyl-4-
tolylsilyl)idenyl) zirconium(IV) dichloride (3), displayed an almost five times higher
activity (3980 kg PE/mol cat.h) than the isomeric bis(η5-2-(dimethyl-4-
tolylsilyl)indenyl) zirconium(IV) dichloride (19)/MAO catalyst (870 kg PE/mol cat.h).
The same trend was observed for the para-fluorophenyl silyl indenyl complexes 23
and 17. This behavior may be explained in a way that the same silyl substituent in
position 2 can exert more steric hindrance around the metal center compared to the
1-substituted analogues. The GPC characterization of the produced polyethylenes
showed that some of the resins have a bimodal molecular weight distribution
indicating at least two different active sites that are involved in the polymerization
process.
1. Introduction
Metallocene complexes received substantial attention in industry and research due to
their capability of being highly active catalyst precursors for ethylene
homopolymerization, copolymerization and stereospecific polymerization of higher α-
olefins [1-5]. Unlike traditional Ziegler Natta catalysts [6-8], the facile ligand
modification with various substituents has led to the preparation of a large number of
metallocene complexes to improve the activity of the catalysts and the properties of
the produced polyolefins [9]. The size, nature and position of the substituents
attached to the cyclopentadienyl, indenyl, or fluorenyl ligands play a key role on the
catalytic activity as well as on the molecular weight and molecular weight distribution
of the produced polymer [10-17]. Since Waymouth et al. [18,19] reported the
successful application of unbridged bis(η5-2-phenylindenyl) zirconium dichloride,
activated with MAO, in the production of elastomeric polypropylene (ePP), a wide
2

range of unbridged bis(2-indenyl) metallocene complexes bearing siloxy, amino, aryl,
alkyl and alkenyl substituents at the 2-position of the indenyl moiety have been
synthesized and investigated as catalyst precursors for the polymerization of olefins
[20-30]. The symmetric metallocene complexes derived from substituted indenes
exist in two conformations: rac- and meso-diastereomers. The ratio rac/meso
depends on the bulkiness of the substituent [31]. Silyl groups have been extensively
used as bridging groups in ansa-metallocene complexes [9]. However, little has
been reported on the catalytic behavior of unbridged indenyl complexes containing
silyl substituents attached directly to the ligand. The synthesis of rac- and meso-
bis(1-dimethylsilylindenyl)-zirconium dichloride was briefly described in a review [32],
while the syntheses of 1- and 2-substituted bis[(trialkylsilyl)indenyl] zirconium
dichloride complexes were only recently reported in the literature [33-36]. In this
study, novel complexes of the type [1-(4-XC6H4SiMe2)-η5-Ind]2MCl2 and [2-(4-
XC6H4SiMe2)-η5-Ind]2MCl2 (where X = Me, MeO, F; M = Zr, Hf) are reported. The
characteristic features of these ligands are the bulky silyl groups functionalized with
an electron donating group (Me), a hetero atom with a lone pair of electrons (MeO) or
an electron withdrawing group (F). The substituents were chosen to cover a wide
range of electronic properties and located at the 4-position of the aryl moiety. The
behavior of these complexes towards ethylene polymerization, after activation with
MAO, is investigated.
2. Results and discussion
2.1. Preparation of 1-substituted silylindenyl compounds
The reactions of the arylchlorodimethylsilanes 1-4 with stoichiometric amounts of
indenyllithium, freshly prepared via deprotonation of indene with n-butyllithium (n-
BuLi), afforded the 1-silyl substituted indenyl compounds 5-8 (Scheme 1). The
arylchlorodimethylsilanes 1-4 as intermediates were prepared according to published
methods [37,38] through reactions of 4-substituted bromobenzene derivatives with
magnesium and a two fold excess of dichlorodimethylsilane in tetrahydrofuran
(Scheme 1). In these reactions, a large excess of dichlorodimethylsilane was used to
3

avoid the problems arising from substitution reactions of both chlorine atoms at the Si
atom leading to the formation of bisaryldimethylsilyl compounds as heavier
byproducts as detected by GC/MS analysis in some reactions. Therefore, cleaner
reactions and better yields were only achieved when using a large excess of
dichlorodimethylsilane.
1) Mg / THF
2) Me2SiCl2
Br
Si
Si
Si
R
R
R
R
Cl
-MgBrCl
1-4
_
Li+
Cl
-LiCl
1-4
5-8
R = Me (1)
R = Me (5)
R = OMe (2)
R = F (3)
R = OMe (6)
R = F (7)
R = CF3 (4)
R = CF3 (8)
Scheme 1: Preparation of the silanes 1-4 and the ligand precursors 5-8.
2.2. Preparation of the 2-substituted silylindenyl compounds 9-12
The 2-silyl substituted indenyl compounds 9-12 were prepared via a synthetic route
that comprises the reaction of the Grignard reagent of 2-bromoindene and the
corresponding aryldimethylchlorosilanes 1-4. Therefore, 2-bromoindene, prepared
according to the literature [39] by reaction of indene with N-bromosuccinimide (NBS)
followed by dehydration (Scheme 2), was reacted with magnesium powder in THF to
yield the corresponding deep red Grignard reagent. Subsequent addition of a THF
4

solution of an equivalent amount of the aryldimethylchlorosilanes 1-4 afforded the 2-
substituted silylindenyl compounds 9-12 in 65-80% yields (Scheme 3).
NBS
p-TosOH
toluene
H2O / DMSO / 0°C
Br
OH
Br
-H2O
Scheme 2: Preparation of 2-bromoindene.
THF / reflux
-MgBrCl
+
BrMg
Si
Si
R
R
Cl
1-4
9-12
R = Me (9)
R = OMe (10)
R = F (11)
R = CF3 (12)
Scheme 3: Preparation of the ligand precursors 9-12.
The silyl substituted indenes 5-12 and their parent chlorosilanes 1-4 were
1
characterized by H-, 13C-NMR and GC/MS. The complete data is given in Table 5
(Experimental).
2.3. Synthesis of the transition metal complexes
Two equivalents of the indenyl ligand precursors 5-8 were deprotonated with two
equivalents of n-butyllithium (n-BuLi) in diethyl ether. Subsequent metallation
reactions with one equivalent of zirconium tetrachloride or hafnium tetrachloride in
diethyl ether yielded the desired metallocene complexes 13-18. The general
synthesis of these complexes is shown in Scheme 4.
5

R
R
1) 2 n-BuLi, Et2O, -78°C - rt
- 2BuH
2
Si
R
2) MCl4, Et2O, -78°C - rt
- 2LiCl
Si
Si
M
Cl
Cl
5-8
13-18
Complex
R
Me
Me
OMe
OMe
F
M
Zr
Hf
Zr
Hf
Zr
Hf
13
14
15
16
17
18
F
Scheme 4: Synthesis of the metallocene complexes 13-18.
The 2-substituted silylindenyl complexes 19-24 were synthesized in an analogous
manner. Thus, two equivalents of the 2-substituted indenyl compounds 9-12 were
transformed to their lithium salts via deprotonation with n-BuLi. Following reactions
with Zr(IV) or Hf(IV) chloride in diethyl ether provided the desired complexes
(Scheme 5). The complexes were obtained in moderate to high yields as fine
powders. Reactions of the ligand precursors 8 and 12 bearing trifluoromethyl
substituents at the silyl groups with zirconium tetrachloride were futile and failed to
yield the desired complexes under various reaction conditions. Instead, extremely air
sensitive products were obtained. The attempts to identify these residues were
unsuccessful because of their insolubility in common organic solvents.
6

R
R
1) 2 n-BuLi, Et2O, -78°C - rt
-2 BuH
2) MCl4, Et2O, -78°C - rt
-2LiCl
2
R
Si
Si
Si
M
Cl
Cl
9-12
19-24
No.
19
20
21
22
23
24
R
Me
Me
OMe
OMe
F
M
Zr
Hf
Zr
Hf
Zr
Hf
F
Scheme 5: Synthesis of the metallocene complexes 19-24.
2.4. Characterization of the complexes
Complexes 13-24 were characterized with NMR spectroscopy, mass spectroscopy,
and elemental analysis (see Experimental). The silyl substituted bis(indenyl)
1
metallocene complexes were characterized with H and 13C NMR spectroscopy
(Table 6). The NMR spectra of few complexes exhibited the existence of two or more
isomers.
The mass spectrometric characterization of 1- and 2-substituted bis(silylindenyl)
complexes using a direct inlet mass spectrometer (EI, 70 eV) was unsuccessful.
Using this high energy (70 eV) ionization technique, the molecules break into smaller
fragments. For instance, complex 17 when analyzed by mass spectroscopy (70 eV)
exhibited only peaks corresponding to the fragment from the loss of one ligand (m/z =
425). Accordingly, matrix-assisted LASER desorption ionization (MALDI-TOF) was
used as a milder ionization technique for mass spectra measurements.
7

2.5. Polymerization of Ethylene
2.5.1. General aspects and mechanism
Metallocene dichloride complexes of group (IV) metals are very important candidates
in catalysis because they can facilitate the polymerization of olefins when treated with
a suitable activator. Methylaluminoxane (MAO), among other activators, is the most
commonly used cocatalyst for this purpose and started its breakthrough as
component of olefin polymerization catalysts 40 years ago [40]. MAO is considered to
consist of cages of [–O-AlMe-]n (n = 3 - 20) units built of mainly six-membered rings
[41-45] In the inside of these dynamic cages monomeric trimethylaluminum
molecules provide the alkylating potential in the activation process. The activation of
a metallocene precatalyst proceeds by substitution of one chloro ligand with a methyl
group followed by abstraction of the remaining chloro ligand. Consequently, an active
metal center with a vacant coordination site (14 electron species) is generated which
is assumed to be (L)2M+–R (L = cyclopentadienyl, indenyl, fluorenyl). The latter is
considered as the active species and can react as a strong Lewis acid capable to
react with π-electrons of the incoming ethylene monomer [42,46].
CH3
Cl
Cl
Al
Zr
Al
O
O
n-1
CH3
Cl
Cl
CH3
Zr
Al
+
O
n
MAO
Scheme 6: Activation of a metallocene catalyst with MAO.
The homogeneous metallocene based polymerization of olefins using
methylaluminoxane (MAO) as a cocatalyst can be explained by a mechanism first
reported by Cossee [47] and Arlman [48,49] for mechanistic studies of the traditional
Ziegler-Natta catalysts. The proposed mechanism involves three steps: initiation,
propagation and chain termination (Scheme 7). The initiation step essentially
represents the insertion of the first ethylene molecule into the M–CH3 bond of the
8

catalyst cation. The ethylene molecule coordinates to the metal through its π-
electrons giving rise to an η2-ethylene complex. The propagation step starts with
further insertions of ethylene molecules followed by migration of the chain to the
newly π-coordinated ethylene providing a new vacant site to repeat the insertion
process. Finally, the growth of the polymer chain is terminated by β-hydrogen
elimination or chain transfer to the cocatalyst.
CH3
CH3
Zr
Zr
Zr
MAO
MAO
MAO
a) Initiation step
Zr
Zr
P
MAO
MAO
b) Chain propagation
H
Zr
Zr
P
_
P
MAO
MAO
c) Chain termination
Scheme 7: Cossee-Arlman mechanism of ethylene polymerization: a) initiation step,
b) chain propagation, and c) chain termination.
2.5.2. Ethylene polymerization activities of complexes 13-18
The catalyst precursors 13-18 are unbridged indenyl metallocene complexes bearing
phenyl substituted silyl groups at the 1-position of the indenyl ligands. Ethylene
9

polymerization reactions were carried out in a 1 liter Büchi steel reactor using 250 ml
of pentane and MAO as co-catalyst (M:Al = 1:2000) at a polymerization temperature
of 60°C and 10 bar ethylene pressure. The catalytic activities of complexes 13-18 are
shown in Table 1.
Table 1: Ethylene polymerization activities of complexes 13-18.
Structure
No.
13
14
15
16
17
18
M
Zr
Hf
Zr
Hf
Zr
Hf
R
Me
Me
MeO
MeO
F
Activitya
3980
1760
490
R
R
Si
Si
50
4475
1755
M
Cl
Cl
F
a (kg PE/mol cat. h)
In the catalyst series 13-18, the zirconium catalyst 17 bearing a fluoro substituent at
the phenyl silyl group was the most active catalyst (4475 kg PE/mol cat. h), whereas
the hafnium catalyst 16 containing a methoxy phenyl silyl group showed the lowest
activity (50 kg PE/mol cat. h). The variation in the activities of 13-18 correlates well
with the steric bulk of the substituents (Me, MeO, F) rather than their electronic
properties. For instance, the complexes 13 and 17 showed comparable activities
despite the big difference in the electronic nature of methyl and fluoro groups. This
trend is even more obvious for complexes 14 and 18. This can give an indication that
the electronic nature of methyl and fluoro substituents seems to have a minor effect
on the activity of the corresponding catalysts and that only their similar steric
contribution accounts for their comparable activities. In a similar study [50] it has
been demonstrated that the activity variation in ethylene polymerization of a series of
1- and 2-substituted indenyl complexes can be mainly rationalized by steric reasons.
The activities observed for complexes 13-18 were lower than the activity recorded for
the unsubstituted metallocene complex Ind2ZrCl2 [29300 kg PE/mol Zr h] under
similar polymerization conditions [51]. However, the activities in the
homopolymerization of ethylene of 14 and 17 are significantly higher than the
10

activities recently reported [52] for similar metallocene catalysts comprising silyl-
substituted ligands: [1-(SiMe3)indenyl]2ZrCl2 (300 kg PE/mol Zr h) and [1-
(Me2SiPh)indenyl]2ZrCl2 (2570 kg PE/mol Zr h). This behaviour reveals that the
electronic effect of the aromatic phenyl ring of the synthesized catalysts enhances
their activity. The polymerization activities of the 1-substituted catalysts 13-18 (Table
1) are generally lower than the activity values observed for the analogous 1-benzyl
substituted catalyst [53] and the 1-(4-fluorobenzyl) substituted catalyst [16]. The
hafnium complexes in this series of catalysts exhibited significantly lower activities
compared with their zirconium analogues which can be explained by the
thermodynamically more stable metal carbon σ-bond between hafnium and the
polymer chain (Hf-C) or due to kinetic reasons [54]. The catalysts 15 and 16/MAO
bearing methoxy groups exhibited comparatively lower activities compared with the
other catalysts. However, these activity values are consistent and comparable with
the activity values noted for other similar catalysts incorporating heteroatom
substituted ligands [55]. The inefficiency of these types of catalysts can be attributed
to the poisoning effect resulting from intermolecular interactions of the lone pair
electrons at the heteroatoms with the cationic metal centers or the cocatalyst (Lewis
base-Lewis acid interaction).
2.5.3 Ethylene polymerization activities of complexes 19-24
Complexes 19-24 are a series of unbridged symmetrical 2-substituted silylindenyl
complexes of zirconium and hafnium. The bulky silyl substituents bear an electron
withdrawing atom (F), an electron donating group (Me), and an electron donating
group with lone pair of electrons (O-Me) at the para position to the silicon atom.
Ethylene polymerization reactions were carried out in a 1 liter Büchi steel reactor
using 250 ml of pentane and MAO as the cocatalyst (M:Al = 1:2000) at a
polymerization temperature of 60°C and 10 bar ethylene pressure. The catalytic
activities of complexes 19-24 are presented in Table 2.
.
11

Table 2: Ethylene polymerization activities of complexes 19-24.
Structure
No.
19
20
21
22
M
Zr
Hf
Zr
Hf
R
Activitya
870
Me
R
R
Me
770
MeO
MeO
940
Si
Si
60
M
23
Zr
Hf
F
F
510
n.d.
Cl
Cl
24
a (kg PE/mol cat. h)
Among this series, the lowest activity is displayed by complex 22 bearing a methoxy
substituted silyl group (60 kg PE/ mol cat. h). This result could be explained by the
fact that the methoxy group attached to the silicon atom is a Lewis base due to the
presence of free electron pairs at the oxygen atom. These lone pairs of electrons can
interact in a greater extent with hafnium resulting in blocking the active sites and
substantially deactivate the catalyst [50]. The high bulkiness exerted by the silyl
groups, particularly at the 2-positions, renders the other parameters, such as the
nature of central metal or substituents, less dominant in activity. Thus, no remarkable
differences are observed in their catalytic activities. The catalysts 19 – 23/MAO
exhibited lower activities compared with the previously reported 2-trimethylsilyl and 2-
dimethylphenylsilyl substituted catalysts [47] and the 2-benzyl and 2-alkyl substituted
catalysts [45]. In a comparison with the unsubstituted metallocene catalyst Ind2ZrCl2,
the catalyst precursors 19-23, demonstrated lower polymerization activities [46].
In a comparison between the polymerization activities of the 1- and 2-substituted
zirconocene complexes, the position at which the substituents are attached to the
indenyl rings has proved to possess a significant influence on the activities. For
instance, catalyst 13/MAO bearing a methyl phenyl substituted silyl group at position
1 displayed an almost five times higher activity than the catalyst 19/MAO bearing the
12

same substituent at position 2. The same trend was observed for complexes 23 and
17 bearing a fluoro substituted phenyl silyl group.
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
1-Substituted complexes
2-Substituted complexes
4475
3980
870
940
490
510
0
23
13
19
15
21
17
Scheme 8: Comparison of the polymerization activities of 1- and 2-substituted
zirconocene complexes bearing the same silyl substituents.
The higher activities of the 1-substituted indenyl complexes in ethylene
polymerization could be explained in a way that the same silyl substituent in position
2 can exert more steric hindrance around the metal center compared to the 1-
substituted analogues.
2.5.4 Polymer analysis
The produced polyethylene samples were analyzed by high temperature gel
permeable chromatography GPC. The values of polymer molecular weights and PD
for polymers produced by zirconium catalysts are given in Table 3.
13

Table 3: GPC molecular weight analyses of polyethylene samples produced with
zirconium complexes 13, 15, 17, 19, 21, 23/MAO
PE sample
Mn
Mw
PD
2.8
9.8
3.1
10.4
6.7
6.5
13
15
17
19
21
23
97880
42430
80590
18450
33970
43850
275790
416440
256190
193630
230470
284660
Scheme 9: Molecular weight distribution curve of the polyethylene sample obtained
with 19/MAO.
The produced polyethylene samples were also analyzed by differential scanning
calorimetry (DSC) and viscosimetry. The results of the polymer analyses are
summarized in Table 4.
Table 4: DSC and viscosimetry molecular weight analysis of polyethylenes produced
with complexes 13-23
Complex
∆Hm [J/g]
162.3
Tm [°C]
135.4
136.2
135.5
136.2
Crystallinity [α]
Mη [g/mol]
292000
355000
n.d.
13
14
15
16
0.56
0.52
0.49
0.49
151.2
141.9
142.0
n.d.
14

17
18
19
20
21
22
23
152.7
141.7
169.2
144.9
158.5
138.9
151.1
136.9
135.9
135.4
135.2
137.5
135.0
135.4
0.53
0.49
0.58
0.50
0.55
0.48
0.52
270000
535000
265000
445000
350000
n.d.
385000
From DSC analyses of the polyethylene samples, no significant differences in the
melting points were observed. However, molecular weight measurements showed
that the molecular weights of polymers produced with hafnium complexes are
significantly higher than those of the polymers produced with the analogous
zirconium complexes. This can be attributed to the thermodynamically more stable
bond between hafnium and the polymer chain [49] allowing more insertion steps in
the polymerization process before chain termination occurs. It was a surprise that
complexes 15, 19, 21 and 23 produced resins with a bimodal molecular weight
distribution indicating at least two different active sites that are involved in the
polymerization process. The crystallinity values were obtained from the following
equation: α = ∆Hm/∆Hm,0 with ∆Hm,0 = 290 J/g extrapolated for 100% crystalline
polyethylene [56]. While the molecular weights of the hafnium catalyzed polyethylene
samples were higher compared with the zirconium catalyzed polymers, the opposite
trend could be observed for the crystallinity values.
3. Experimental
3.1 General
All reactions were carried out under an inert gas atmosphere of pure oxygen-free
argon using standard Schlenk techniques. n-Pentane, n-hexane, diethyl ether,
toluene, and tetrahydrofuran were purified by distillation over Na/K alloy. Diethyl ether
was additionally distilled over lithium aluminum hydride. Toluene was additionally
distilled over phosphorus pentoxide. Methylene chloride and carbon tetrachloride
were dried over phosphorus pentoxide. Deuterated organic solvents (CDCl3, CD2Cl2,
and C6D6) for NMR spectroscopy were purchased from Euriso-Top and stored over
molecular sieves (3 Å). Argon (5.0) and ethylene (3.5) were purchased from Rieβner
15

Company. Methylaluminoxane (10% in toluene) was purchased from Chemtura
Europe Limited (Bergkamen). All other starting materials were commercially available
and used without further purification.
3.2 NMR spectroscopy
NMR spectra were recorded with Bruker ARX (250 MHz), Varian Inova (300 MHz) or
Varian Inova (400 MHz) spectrometers. All spectra were recorded at 298 K. In the
1H-NMR spectra, the chemical shift of the residual proton signal of the solvent was
used as a reference (δ = 7.24 ppm for chloroform, δ = 5.32 ppm for methylene
13
chloride, δ = 7.16 ppm for benzene). In the C-NMR spectra, the chemical shift of
the solvent was used as a reference (δ = 77.0 ppm for chloroform-d1, δ = 54.0 ppm
for methylene chloride-d2, δ = 128.0 ppm for benzene-d6).
3.3 GC/MS
GC/MS spectra were recorded with a Thermo FOCUS gas chromatograph combined
with a DSQ mass detector. A 30 m HP-5 fused silica column (internal diameter 0.32
mm, film 0.25 µm and flow 1 ml/min) was used and helium (4.6) was applied as
carrier gas. The measurements were recorded using the following temperature
program:
Starting temperature: 50 °C, duration: 2 minutes;
Heating rate: 20 °K/minute, duration: 12 minutes;
Final temperature: 290 °C, duration: 27 minutes.
3.4 Mass spectrometry
Mass spectra were recorded with a VARIAN MAT CH-7 instrument (direct inlet, EI, E
= 70 EV) and a VARIAN MAT 8500 spectrometer at the Zentrale Analytik of the
University of Bayreuth. Matrix Assisted Laser Desorption Ionization Time-of-Flight
Mass Spectrometry (MALDI-TOF-MS) measurements were performed on a Bruker
Daltonic Reflex TOF using graphite as the matrix. The LASER intensity was set to
60-65 %. The sample solutions were prepared in toluene or methylene chloride at a
concentration of 1 mg/ml.
3.5 Elemental analysis
16

Elemental analyses were performed with a Vario EL ІІІ CHN instrument. Therefore, 4-
6 mg of the complex were weighed into a standard tin pan. The tin pan was carefully
closed and introduced into the auto sampler of the instrument. The values of C, H
and N were calibrated using acetamide as a standard.
3.6 High temperature gel permeable chromatography GPC
The molecular weights (Mw/Mn) of the ethylene polymers were determined by gel
permeation chromatography, HT-GPC PL-220 chromatograph at 150°C using 1,2,4-
trichlorobenzene as the mobile phase. The samples were prepared by dissolving the
polymer (0.2 mg/l) in the mobile phase solvent in an external oven and were run
without filtration. The molecular weight was referenced to polystyrene (Mw = 510 –
3100000 g/mol) standards. The reported values are the average of at least two
independent determinations.
3.7 DSC analysis
Differential scanning calorimetry experiments were conducted at a heating rate of
10°C/min under N2 atmosphere with a Mettler Toledo DSC/SDTA 821e instrument.
Melting enthalpies and melting points were taken from the second heating phase.
The values were calibrated using indium as a standard (m.p. 429.78 K, Hm = 28.45
J/g).
3.8 Viscosimetry analysis
Viscosimetry analyses for the determination of the viscosity average molecular
weights [Mη] of the polyethylene samples were performed on an Ubbelohde precision
capillary viscometer in cis/trans-decalin at 135 0.1 °C. For the preparation of the
sample solutions, an amount of 50 mg of the polymer was dissolved in decalin (45
ml) by heating for 3 hours at 135 °C. Mη values were determined by comparing the
obtained values with calibration curves available for different polymer concentrations.
17

Table 5: NMRa and MS data of compounds 1-12.
No.
1H NMR
13C NMR
MS [m/z] (%)
7.61 d (3J =5.6 Hz, 2H-Ar)
7.31 d (3J =5.6 Hz, 2H-Ar)
2.46 s (3H, CH3)
140.4 (Cq)
133.1 (CH)
132.6 (Cq)
128.8 (CH)
21.5 (CH3)
2.1 (Si(CH3)2)
1
n.d.
0.76 s (6H, Si(CH3)2)
7.44 d (3J =8.5 Hz, 2H-Ar)
6.78 d (3J =9.0 Hz, 2H-Ar)
3.29 s (3H, O-CH3)
161.9 (Cq)
135.1 (CH)
127.3 (Cq)
114.1 (CH)
54.5 (O-CH3)
2.1 (Si(CH3)2)
2
3
4
n.d.
0.47 s (6H, Si(CH3)2)
7.61-7.57 m (2H-Ar
7.09 t (2H-Ar)
0.66 s (6H, Si(CH3)2)
164.4 d (Cq)
135.3 d (CH)
131.8 d (Cq)
115.3 d (CH)
2.1 (Si(CH3)2)
188 M+ (17)
173 M+-Me (100)
153 (8)
7.75 d (3J =7.0 Hz, 2H-Ar)
7.65 d (3J =7.0 Hz, 2H-Ar)
0.70 s (6H, Si(CH3)2)
142.0 (Cq)
238 M+ (10)
134.5 q (CH)
126.3 m (Cq)
125.7 q (CH)
123.5 m (Cq, CF3)
2.9 (Si(CH3)2)
223 M+-Me (100)
7.33-7.27 m (4H, Ar-H)
7.13-7.08 m (4H, Ind-H)
6.85 m (1H, C3-Ind)
6.50 m (1H, C2-Ind)
3.63 s (1H, C1-Ind)
2.28 s (3H, Ar-CH3)
0.06 s (3H, Si-CH3)
0.00 s (3H, Si-CH3)
144.9, 144.2, 139.2 (Cq) 264 M+ (8)
135.6 (CH, 2C)
133.9 (Cq)
133.8, 129.1, 128.6,
124.8, 123.5, 122.9 (CH)
120.9 (CH, 2C)
249 M+-Me (3)
149 M+-Ind (100)
115 Indenyl (5)
5
45.8 (CH, C1-Ind)
21.5 (Ar-CH3)
-4.4, -5.0 (Si(CH3)2)
7.40-6.80 m (8H, Ar-H,
Ind-H)
161.3, 145.4, 144.7,
135.7 (Cq)
135.5 ( CH, 2C)
129.6, 128.2, 125.3,
124.0, 123.3, 121.4 (CH)
114.0 (CH, 2C)
54.5 (O-CH3)
46.5 (CH, C1-Ind)
-4.0, -5.0 (Si(CH3)2)
280 M+ (4)
265 M+-Me (2)
165 M+-Ind (100)
115 Indenyl (7)
6.75 m (1H, C3-Ind)
6.48 m (1H, C2-Ind)
3.55 m (1H, C1-Ind)
3.28 s (3H, O-CH3)
0.01 s (3H, Si-CH3)
0.00 s (3H, Si-CH3)
6
7
7.28 d (3J = 8.3Hz, 2H,
Ar-H)
163.9 d (1JC-F = 249 Hz
Cq, C-F)
268 M+ (7)
253 M+-Me (2)
153 M+-Ind (100)
115 Indenyl (8)
7.24 d (3J = 7.2Hz 2H,
Ar-H)
144.6 ,144.2 (Cq)
135.7 d (3JC-F = 7 Hz,
18

7.09-6.90 m (4H, Ind-H)
6.75 d (3J = 5.2 Hz, 1H,
C3-Ind)
CH, 2C)
135.2 (CH)
132.7 d (4JC-F = 4 Hz, Cq)
129.4, 125.0, 123.6,
122.8, 121.1(CH)
114.9 d (2JC-F = 20 Hz,
CH, 2C)
6.42 d (3J = 5.2 Hz, 1H,
C2-Ind)
3.54 s (1H, C1-Ind)
0.03 s (3H, Si-CH3)
0.00 s (3H, Si-CH3)
45.7 (CH, C1-Ind)
-4.2, -4.8 (Si(CH3)2)
7.51-7.44 m (4H, Ar-H)
7.31-7.23 m (4H, Ind-H)
6.92 m (1H, C3-Ind)
6.60 m (1H, C2-Ind)
3.44 s (1H, C1-Ind)
0.46 s (3H, Si-CH3)
0.44 s (3H, Si-CH3)
144.0 (Cq)
134.5 q (2C),133.3,
132.5 (CH)
132.0, 131.5 (Cq)
126.8 (CH)
218 M+ (5)
299 M+-F (1)
203 M-Ind (100)
115 Indenyl (12)
8
125.9 m (Cq)
124.5, 124.4 (CH)
124.3 m (Cq, CF3)
122.7, 121.0 q (2C), 39.0
(CH)
0.6 (Si(CH3)2)
7.36 br (2H, Ar-H)
7.32 br (2H, Ar-H)
7.29 m (1H, C3-Ind)
7.12-7.07 m (4H)
3.36 s (2H, C1-Ind)
2.26 s (3H, Ar-CH3)
0.40 br (6H, Si(CH3)2)
147.3, 146.9, 145.4 (Cq) 264 [M+] (6)
142.1 CH (C3-Ind)
138.9, 134.6 (Cq)
133.9 (CH, 2C)
128.6 (CH, 2C)
126.2, 124.8, 123.6,
120.9 (CH)
249 M+-Me (5)
149 M+-Ind (100)
115 Indenyl (38)
9
42.6 (CH2, C1-Ind)
21.5 (Ar-CH3)
-2.4 (Si(CH3)2)
7.56-7.49 m (2H, Ar-H)
7.45 m (1H, C3-Ind)
7.33-7.16 (4H, Ind-H)
7.00-6.93 m (2H, Ar-H)
3.87 s (2H, C1-Ind)
3.85 s (3H, O-CH3)
0.53 s (3H, Si-CH3)
0.35 s (3H, Si-CH3)
160.6, 147.5, 145.4 (Cq) 280 M+ (3)
142.0, 135.4 (2C) (CH)
130.9, 127.0 (Cq)
265 M+-Me (4)
165 M+-Ind (100)
124.7 (2C),124.5, 123.5, 115 Indenyl (20)
122.9, 113.6 (CH)
54.9 (O-CH3)
42.5 (CH2, C1-Ind)
0.9, -2.3 (Si(CH3)2)
10
7.52 m (2H, Ar-H)
7.48 m (2H, Ar-H)
7.35 s (1H, C3-Ind)
7.28-7.24 m (2H)
7.16-7.10 m (2H)
3.51 s (2H, C1-Ind)
0.58 s (6H, Si(CH3)2)
165.3 d, 146.8, 145.2,
146.6 (Cq)
142.4 (CH)
135.8 d (2C, CH)
134.9 d (Cq)
126.3 d (2C, CH)
125.0, 123.6, 121.0,
115.0 (CH)
42.5 (CH2, C1-Ind)
-2.4 (Si(CH3)2)
268 M+ (20)
253 M+-Me (10)
152 M+-Ind (100)
114 Indenyl (11)
11
12
7.73-7.63 dd (4H, Ar-H)
7.60-7.46 m (2H)
146.8, 145.6, 145.1,
141.1 (Cq)
318 M (5)
303 M+-Me (2)
19

7.35-7.26 m (2H)
142.9 (CH)
134.1 q (2C, CH)
132.4 q (Cq)
128.0 m (Cq, CF3)
126.4, 125.1, 124.3,
123.6 (CH)
203 M+-Ind (100)
115 Indenyl (7)
7.25 s (1H, C3-Ind)
3.49 d (3J =1.7 Hz, 2H)
0.59 s (6H, Si(CH3)2)
121.0 q (2C, CH)
42.5 (CH2, C1-Ind)
-2.7 (Si(CH3)2)
a δ (ppm) rel. CHCl3 (7.24 ppm, 1H NMR) and rel. CDCl3 (77.0 ppm, 13C NMR) at 298 K.
Table 6: 1H and 13C NMRa spectra of complexes 13-24.
No.
Structure
1H NMR
13C NMR
7.52-7.46 m (4H)
7.30-7.28 m (4H)
7.13-7.06 m (8H)
6.3 br (2H, C3-Ind)
6.0 br (2H, C2-Ind)
2.3 s (6H, Ar-CH3)
0.58 s (6H, Si-CH3)
0.53 s (6H, Si-CH3)
139.3, 134.5, 134.4
(Cq)
134.2 (2C, Ar-CH)
130.0 (Cq)
128.8, 127.0, 126.8,
126.4, 126.1 (CH),
125.5 (2C, Ar-CH)
113.5 (Cq, C1-Ind)
105.3 (CH, C2-Ind)
21.5 (Ar-CH3)
Si
Si
13
Zr
-0.6, -1.3 (Si(CH3)2)
Cl
Cl
7.49-7.43 m (4H)
7.31-7.29 m (4H)
7.13-7.08 m (8H)
6.3 d (3J =2.8 Hz,
2H, C3-Ind)
139.3, 134.5 (Cq)
134.2 (2C, Ar-CH)
133.5, 130.1 (Cq)
128.8, 126.9, 126.4,
126.3, 125.9 (CH),
125.5 (2C, Ar-CH)
110.1 (Cq, C1-Ind)
102.8 (CH, C2-Ind)
21.5 (Ar-CH3)
Si
5.8 d (3J =2.8 Hz,
2H, C2-Ind)
Si
14
2.3 s (6H, Ar-CH3)
0.6 s (6H, Si-CH3)
0.5 s (6H, Si-CH3)
Hf
-0.4, -1.2 (Si(CH3)2)
Cl
Cl
20

7.50 d (3J =7.8 Hz,
4H)
160.6 (Cq)
135.6 (2C, CH)
134.5, 129.9, 128.9
(Cq)
O
O
7.33 d (3J =7.9 Hz,
4H, Ar-H)
7.16-7.10 dd (4H)
6.83 d (3J =7.9 Hz,
4H, Ar-H)
127.0, 126.8, 126.3,
126.1, 125.5 (CH)
113.8 (Cq, C1-Ind)
113.7 (2C, CH)
105.3 (CH, C2-Ind)
55.1 (O-CH3)
Si
Si
15
6.33 d (3J =3.0 Hz,
2H, C3-Ind)
6.00 d (3J =3.0 Hz,
2H, C2-Ind)
Zr
-0.5, -1.1 (Si(CH3)2)
3.72 s (6H, O-CH3)
0.60 s (6H,Si-CH3)
0.53 s (6H,Si-CH3)
Cl
Cl
7.56-7.47 m (4H)
7.35 m (4H, Ar-H)
7.21 m (4H)
6.91 m (4H, Ar-H)
6.38 br (2H, C3-Ind)
6.05 br (2H, C2-Ind)
3.74 s (6H, O-CH3)
0.61 s (6H, Si-CH3)
0.53 s (6H, Si-CH3)
160.9 (Cq)
O
O
135.8 (2C, CH)
134.6, 129.7, 129.0
(Cq)
127.2, 126.9, 126.6,
126.3, 125.9 (CH)
111.2 (Cq, C1-Ind)
113.9 (2C, CH)
102.7 (CH, C2-Ind)
55.1 (O-CH3)
Si
Si
16
Hf
-0.5, -1.0 (Si(CH3)2)
Cl
Cl
7.46 br (4H, Ar-H)
7.30 br (4H, Ar-H)
7.10 m (2H)
163.9 d (Cq, 1JC-F
247 Hz)
=
F
F
136.0 d (2JC-F = 7.3,
CH-Ar, 2C)
6.89 m (2H)
6.34 m (2H)
6.20 m (2H)
6.03 m (2H, C3-Ind)
5.63 m (2H, C2-Ind)
0.53 s (6H, Si-CH3)
0.49 s (6H, Si-CH3)
133.6 d (Cq, 4JC-F
3.8 Hz, C-F)
130.0, 128.5 (Cq)
127.6, 127.0, 126.3,
125.8, 125.3 (CH)
114.9 d (3JC-F = 19.8
Hz, CH-Ar, 2C)
=
17b
Si
Si
Zr
113.8 (Cq, C1-Ind)
106.1 (CH, C2-Ind)
-0.5, -0.9 (Si(CH3)2)
Cl
Cl
21

7.50 dd (4H)
7.32 t (4H)
7.13 d (4H)
163.8 d (Cq, 1JC-F
248 Hz, C-F)
=
F
F
136.0 d (2JC-F=7.3,
Ar-CH, 2C)
6.95 t (4H)
6.25 d (3J = 3.2 Hz,
2H, C3-Ind)
133.9 d (Cq, 4JC-F
3.8 Hz, C-F)
133.4, 128.6 (Cq)
127.2, 126.9, 126.4,
126.0, 125.3 (CH)
115.0 d (3JC-F = 19.5
Hz, Ar-CH, 2C)
=
5.94 d (3J =2.8 Hz,
2H, C2-Ind)
Si
Si
18
0.58 s (6H, Si-CH3)
0.57 s (6H, Si-CH3)
Hf
110.7 (Cq, C1-Ind)
102.8 (CH, C2-Ind)
0.6, -1.1 (Si(CH3)2)
Cl
Cl
7.65-7.63 m (4H)
7.11-7.09 m (4H)
7.04-6.95 dd (8H,
Ar-H)
5.96 s (4H, C1-Ind)
2.19 s (6H, Ar-CH3)
138.7, 138.4, 135.2
(Cq)
133.7 (CH)
129.3 (Cq)
128.4, 125.7, 125.4,
112.3 (CH)
Si
Si
19
20
21
0.35 s (12H, Si-CH3) 21.3 (Ar-CH3)
-2.5 (CH3, Si(CH3)2)
Zr
Hf
Zr
Cl
Cl
Cl
Cl
Cl
Cl
7.71-7.69 m (4H)
7.20-7.18 m (4H)
7.10 d (3J =7.2 Hz,
4H, Ar-H)
138.8, 138.1, 135.4
(Cq)
133.8 (CH)
128.6 (Cq)
128.4, 125.8, 125.3,
109.3 (CH)
Si
Si
7.02 d (3J =7.2 Hz,
4H, Ar-H)
5.90 s (4H, C1-Ind)
2.25 s (6H, Ar-CH3)
0.41 s (12H, SiCH3)
21.3 (Ar-CH3)
-2.4 (Si(CH3)2)
O
O
7.34-7.27 m (8H)
7.00-6.92 m (8H)
6.11 s (4H, C1-Ind)
3.84 s (6H, O-CH3)
0.10 s (12H, SiCH3)
159.7, 144.9, 144.0
(Cq)
129.4 (CH)
129.2 (Cq)
126.3, 126.0, 120.6,
113.9 (CH)
Si
Si
55.1 (O-CH3)
2.1 (Si(CH3)2)
22

O
O
7.40-7.32 m (8H)
7.09-7.01 m (8H)
6.16 s (4H, C1-Ind)
3.84 s (6H, O-CH3)
0.11 s (12H, SiCH3)
160.0, 145.0, 144.1
(Cq)
129.7 (CH)
129.1 (Cq)
126.4, 126.0, 120.8,
Si
Si
22
114.3 (CH)
55.2 (O-CH3)
2.1 (Si(CH3)2)
Hf
Cl
Cl
7.42 m (4H, Ar-H)
7.29-7.13 m (8H)
7.07 m (4H, Ar-H)
6.20 s (4H, C1-Ind)
0.08 s (12H, SiCH3)
164.1 d (1JC-F = 253
Hz, Cq)
F
F
144.7 d (4JC-F = 3.6
Hz, Cq)
143.4 (Cq)
135.7 d (2JC-F = 7.9
Hz, Ar-CH)
Si
Si
23b
132.8 (Cq)
129.4, 125.0 (CH)
115.0 d (3JC-F = 19.5
Hz, Ar-CH)
Zr
Cl
Cl
105.3 (CH, C1-Ind)
-4.0 (Si(CH3)2)
7.43 m (4H, Ar-H)
7.28-7.16 m (8H)
7.05 m (4H, Ar-H)
5.90 s (4H, C1-Ind)
0.45 s (12H, SiCH3)
163.5 d (1JC-F = 254
Hz, Cq)
F
F
138.2 d (4JC-F = 3.6
Hz, Cq)
136.0 d (2JC-F = 6.9
Hz, Ar-CH)
Si
Si
24b
133.5, 128.6 (Cq)
126.0, 125.7 (CH)
115.0 d (3JC-F = 19.5
Hz, CH)
Hf
109.1 (CH, C1-Ind)
-2.3 (Si(CH3)2)
Cl
Cl
a δ (ppm) rel. CHCl3 (7.24 ppm, 1H NMR) and rel. CDCl3 (77.0 ppm, 13C NMR) at 298 K.
b Two isomers.
3.9 Polymerization of ethylene
Few milligrams of the complexes were dissolved or suspended in toluene (5-10 ml)
and mixed with the appropriate amount of methylaluminoxane (MAO). The activated
complexes were suspended in pentane (250 ml) in a 1l Schlenk flask and then
transferred under argon to a 1l Büchi autoclave. The temperature of the thermostat
was adjusted to the desired value and an ethylene pressure of 10 bar was applied for
one hour. After releasing the pressure, the obtained polymer was filtered over a frit,
23

washed with dilute hydrochloric acid, water, and finally with acetone and dried under
vacuum.
3.10. Synthesis procedures
3.10.1 General synthesis of the arylchlorodimethylsilane compounds 1-4
A solution of a 4-substituted 1-bromobenzene (15.0 mmol) in THF (40 ml) was added
dropwise at room temperature to a mixture of magnesium powder (20.0 mmol) and
dichlorodimethylsilane (52.0 mmol) in THF (100 ml). After the addition was complete,
the flask content was heated at reflux for approximately 4 hours and subsequently
stirred at room temperature overnight. The solvent and the excess
dichlorodimethylsilane were removed in vacuo (25 mbar). The residue was extracted
three times with n-pentane (300 ml) and the excess magnesium and magnesium
salts were filtered off. The combined pentane solutions were concentrated under
vacuum and the residue was distilled under reduced pressure. The compounds 1-4
were obtained as colorless liquids in 60-75% yields.
3.10.2 General synthesis of the 1-(aryldimethylsilyl)indenyl compounds 5-8
An amount of 10 mmol of n-butyllithium (1.6 M in hexanes) was added to 10 mmol of
indene dissolved in 100 ml of diethyl ether at 0°C. The solution was stirred for 2
hours at room temperature. The solution was again cooled to 0 °C and then an
equivalent amount of the appropriate arylchlorodimethylsilane (1-4) in diethyl ether
was added slowly. The resulting solution was stirred overnight at room temperature.
The solvent was removed in vacuo and the residue was extracted twice with pentane.
The suspension was filtered and passed through silica gel. After removing the
solvent, compounds 5-8 were obtained as yellow oily liquids in 70-80% yields.
3.10.3 Synthesis of 2-bromoindene
To a mixture of indene (200 mmol), distilled water (15 ml) and dimethyl sulfoxide (70
ml) was added portion wise an amount of 210 mmol of N-bromosuccinimide. The
resulting orange solution was stirred for 10 hours at room temperature, hydrolyzed
with chilled water (100 ml), and extracted with diethyl ether (3 x 100 ml). The
combined extracts were dried with magnesium sulphate and concentrated to give
crystals of 2-bromoindan-1-ol upon standing overnight at -24 °C. The obtained 2-
24

bromoindan-1-ol (120 mmol) was suspended in 100 ml of toluene and mixed with a
catalytic amount of para-toluenesulfonic acid monohydrate. The mixture was heated
at reflux for 12 hours, and water was removed by a Dean-Stark apparatus. The
resulting dark brown suspension was filtered and the volatiles were removed under
vacuum. The residue was passed through silica gel using pentane as eluent, then the
solvent was evaporated, and the crude product was distilled in vacuo. 2-
Bromoindene was finally obtained as yellow crystals in 55% yield.
3.10.4 General synthesis of the 2-(aryldimethylsilyl)indenyl compounds 9-12
Magnesium powder (18.0 mmol) and 15 ml of THF were placed in a 250 ml flask. A
solution of 2-bromoindene (15.0 mmol) in 40 ml of THF was added over a period of
40 minutes using a pressure equalizing-addition funnel. After the addition was
completed, the reaction mixture was heated at reflux for 4 hours. The unreacted
magnesium was filtered off and the violet-red coloured Grignard solution was added
dropwise to a stirred solution of the appropriate arylchlorodimethylsilane 1-4 (15.0
mmol) and 50 ml of THF at room temperature. The resulting mixture was stirred for
another 12 hours. The solvent was removed under vacuum and the residue was
extracted twice with n-pentane. The suspension was filtered and passed through
silica gel. After removing the solvent, compounds 9-12 were obtained as red or
yellow oily liquids in 65-80% yields.
3.10.5 General synthesis of the transition metal complexes 13-24
An amount of 2 mmol of the appropriate 1- or 2-substituted indenyl compound was
dissolved in 50 ml of diethyl ether. To this solution, n-butyllithium (2 mmol 1.6 M in
hexanes) was added at -78 °C. This solution was allowed to warm to room
temperature and stirred for further 3 hours. Subsequently, this mixture was
transferred to a suspension of zirconium tetrachloride (1 mmol) or hafnium
tetrachloride (1 mmol) in 20 ml of diethyl ether at -78 °C. The mixture was slowly
allowed to come to room temperature and stirred for further 24 hours. Diethyl ether
was removed and toluene (100 ml) was added. The toluene suspension was filtered,
the volume of the filtrate was reduced, and the complexes were precipitated by
addition of n-pentane. After filtration, the precipitate was washed several times with
25

n-pentane and dried in vacuo to obtain the desired complexes as coloured powders
in 60-70% yields.
Table 7: Elemental analysis data of complexes 13-24.
No.
13
14
15
16
17
18
19
20
21
22
23
24
Cexp
%
Ctheor
%
Hexp
%
Htheor%
62.21
54.93
59.10
52.75
58.15
51.20
62.05
54.01
58.99
52.66
58.03
51.66
62.76
55.70
59.97
53.50
58.60
52.08
62.76
55.70
59.97
53.50
58.60
52.08
5.41
4.52
4.88
4.35
4.82
4.25
5.22
5.30
5.04
4.37
4.99
4.55
5.56
4.93
5.31
4.74
4.63
4.11
5.56
4.93
5.31
4.74
4.63
4.11
4. Conclusions
The synthesis and comparison of six unbridged bis(indenyl) zirconium and hafnium
dichloride complexes containing bulky silyl substituents in the 1-position of the
indenyl ligand and their isomers with the same substituents in the 2-position of the
indenyl ligand is an excellent example to study structure-property-relationships in
catalytic ethylene polymerization. In nearly all cases, the isomers with the
substituents in the 1-position showed higher activities and molecular weights of the
produced polyethylenes. Complex 13 was nearly five times more active than its
isomer 19 and it produced polyethylene with an Mn of 292000 [g/mol] compared with
265000 [g/mol] in the case of 19. Since all polymerization conditions were constant,
steric reasons in the coordination sphere of the catalyst cation seem to be
responsible for this behavior. The interaction with the bulky MAO counter anion must
26

also be considered in this context. The production of bimodal resins is indicating at
least two different active sites that are involved in the polymerization process.
Acknowledgements
The authors thank the Deutsche Akademischer Austauschdienst, DAAD, for financial
support and Dr. W.P. Kretschmer for the GPC measurements.
References
[1] W. Kaminsky, M Fernandes, Polyolefins Journal 2015, 2, 1.
[2] C. Redshaw, Y. Tang, Chem. Soc. Rev. 2012, 41, 4484.
[3] M.C. Baier, M.A. Zuideveld, S. Mecking, Angew. Chem. Int. Ed. 2014, 53, 9722
[4] W. Kaminsky (ed.), “Polyolefins: 50 years after Ziegler and Natta”, Springer, Adv.
Polymer Science 2013/14, 257.
[5] H.G. Alt, Polyolefins Journal 2015, 2, 17.
[6] G. Natta, Angew. Chem. 1956, 68, 393.
[7] K. Ziegler, Angew. Chem. 1964, 76, 545.
[8] G. Natta, Angew. Chem. 1964, 76, 553.
[9] H. G. Alt, A. Köppl, Chem. Rev. 2000, 100, 1205.
[10]N. Piccolrovazzi, P. Pino, G. Consiglio, A. Sironi, M. Moret, Organometallics
1990, 9, 3098.
[11] H. H. Brintzinger, D. Fischer, R. Mülhaupt, B. Rieger, R. Waymouth, Angew.
Chem. 1995, 107, 1255.
[12] M. Bochmann, J. Chem. Soc., Dalton Trans. 1996, 255.
[13] P. C. Möhring, N. J. Coville, J. Organomet. Chem. 1994, 479, 1.
[14] A. C. Möller, R. Blom, R. H. Heyn, O. Swang, J. Kopf, T. Seraidaris, Dalton
Trans. 2006, 2098.
[15] S. Lin, E. Hauptman, T. K. Lal, R. M. Waymouth, R. W. Quan, A. B. Ernst, J.
Mol. Catal. A: Chem. 1998, 136, 23.
[16] G. Jany, M. Gustafsson, T. Repo, E. Aitola, J. A. Dobado, M. Klinga, M.
Leskelä, J. Organomet. Chem. 1998, 553, 173.
[17] R. Leino, H. Luttikhedde, P. Lehmus, C. Wilen, R. Sjöholm, A. Lehtonen, J. V.
Seppälä, J. H. Näsman, Macromolecules 1997, 30, 3477.
27

[18] G. W. Coates, R. M. Waymouth, Science 1995, 267, 217.
[19] H. H. Brintzinger, D. Fischer, R. Mülhaupt, B. Rieger, R. M. Waymouth,
Angew. Chem., Int. Ed. Engl. 1995, 34, 1143.
[20] R. Leino, H. Luttikhedde, C. Wilén, R. Sillanpää, J. H. Näsman,
Organometallics 1996, 15, 2450.
[21] S. Knüppel, J.-L. Fauré, G. Erker, G. Kehr, M. Nissinen, R. Fröhlich,
Organometallics 2000, 19, 1262.
[22] H. Luttikhedde, R. Leino, M. J. Ahlgrén, T. A. Pakkanen, J. H. Näsman, J.
Organomet. Chem. 1998, 557, 227.
[23] H. Luttikhedde, R. Leino, C. Wilén, J. H. Näsman, M. J. Ahlgrén, T. A.
Pakkanen, Organometallics 1996, 15, 3092.
[24] T. Dreier, G. Erker, R. Fröhlich, B. Wibbeling, Organometallics 2000, 19, 4095.
[25] T. Dreier, G. Unger, G. Erker, B. Wibbeling, R. Fröhlich, J. Organomet. Chem.
2001, 622, 143.
[26] T. Dreier, K. Bergander, E. Wegelius, R. Fröhlich, G. Erker, Organometallics
2001, 20, 5067.
[27] H. Schumann, D. F. Karasiak, S. H. Mühle, W. Kaminsky, U. Weingarten, J.
Organomet. Chem. 2001, 636, 31.
[28] R. Schmidt, H. G. Alt, J. Organomet. Chem. 2001, 621, 304.
[29] G. Y. Lee, M. Xue, M. S. Kang, O. C. Kwon, J.-S. Yoon, Y.-S. Lee, H. S. Kim,
H. Lee,I.-M. Lee, J. Organomet. Chem. 1998, 558, 11.
[30] S. C. Collins, Y. Hong, R. Ramachandran, N. J. Taylor, Organometallics 1991,
10, 2349.
[31] A. J. Puranen, M. Klinga, M. Leskelä, T. Repo, Organometallics 2004, 23,
3759.
[32] T. Cuenca, P. Royo, Coord. Chem. Rev. 1999, 193–195, 447.
[33] O. W. Lofthus, C. Slebodnick, P. A. Deck, Organometallics 1999, 18, 3702.
[34] N. E. Grimmer, N. J. Coville, C. B. de Koning, J. M. Smith, L. M. Cook, J.
Organomet. Chem. 2000, 616, 112.
[35] N. E. Grimmer, N. J.Coville, C. B. de Koning, J. Organomet. Chem. 2002, 642,
195.
[36] A. C. Möller, R. H. Heyn, R. Blom, O. Swang, C. H. Görbitz, J. Kopf, Dalton
Trans. 2004, 1578.
[37] C. Eaborn, K. L. Jones, P. D. Lickiss, J. Organomet. Chem. 1994, 466, 35.
28

[38] C. Beyer, U. Böhme, C. Pietzsch, G. Röwer, J. Organomet. Chem. 2002, 654,
187.
[39] W. A. Lindley, D. W. H. MacDowell, J. Org. Chem. 1982, 47, 705.
[40]
A. Andresen, H.-G. Cordes, J. Herwig, W. Kaminsky, A. Merck, R. Mottweiler,
J. Pein, H. Sinn, H.-J- Vollmer, Angew. Chem. Int. Ed. Engl. 1976, 15, 630.
[41]
[42]
H. Sinn, W. Kaminsky, Adv. Organomet. Chem.1980, 18, 99.
M. R. Mason, J. M. Smith, S. G. Bott, A. R. Barron, J. Am. Chem. Soc. 1993,
115, 4971.
[43]
M. S. Kuklin, J. T. Hirvi, M. Bochmann, M. Linnolahti, Organometallics
2015, 34, 3586.
[44]
A. F. R. Kilpatrick, J.-C. Buffet, P. Norby, N. H. Rees, N. P. Funnell, S.
Sripothongnak, D. O´Hare, Chem. Mater. 2016, 26, 7444.
[45]
H. S. Zijlstra, M. Linnolahti, S. Collins, J. S. McIndoe, Organometallics 2017,
36, 1803.
[46] H. Sinn, Makromol. Chem., Makromol. Symp. 1995, 97, 27.
[47] P. Cossee, J. Catal. 1964, 3, 80.
[48] E. J. Arlman, J. Catal. 1964, 3, 89.
[49] E. J. Arlman, P. Cossee, J. Catal. 1964, 3, 99.
[50] N. E. Grimmer, N. J.Coville, C. B. de Koning, J. Organomet. Chem. 2002, 642,
195.
[51] A. C. Möller, R. Blom, O. Swang, A. Hannisdal, E. Rytter, J. A. Stovneng, T.
Piel, J. Phys. Chem. A 2008, 112, 4074.
[52] C. Schmid, Ph.D. Thesis, University of Bayreuth 1996.
[53] E. Aitola, M. Surakka, T. Repo, M. Linnolahti, K. Lappalainen, Kaisa Kervinen,
M. Klinga, T. Pakkanen, M. Leskelä, J. Organomet. Chem. 2005, 690, 773.
[54] J. A. Simoes, J. L. Beauchamp, Chem. Rev. 1990, 90, 629.
[55] I.M. Lee, W. Gauthier, J. M. Ball, B. Iyengar, S. Collins, Organometallics 1992,
11, 2115.
[56] G. Luft, M. Dorn, Angew. Makromol. Chem. 1991, 188, 177.
29