Dissymmetric ansa zirconocene complexes with di- and trisubstituted indenyl ligands as catalysts for homogeneous ethylene homo- and ethylene/1-hexene copolymerization reactions

Article abstract of DOI:10.1016/j.poly.2017.01.021

Different routes for the synthesis of 1,2- and 1,2,3-substituted indene derivatives are described. Representative substituents are: Me, Ph, PhCH₂, PhCH₂CH₂, PhCH₂CH₂CH₂, CH₂CH?=?CH₂. Subsequent deprotonation of these substituted indenes and reaction with indenyl zirconium trichloride gave the corresponding dissymmetric bis(indenyl) zirconium complexes. After activation with methylaluminoxane (MAO) these complexes show high activities both in ethylene homopolymerisation and ethylene/1-hexene copolymerisation. The rate of comonomer incorporation can reach 33.3% (15/MAO). The copolymers exhibit lower melting points than the homopolymers and their crystallinities α are lower compared with the homopolymers.

Full text of DOI:10.1016/j.poly.2017.01.021

Polyhedron 126 (2017) 72–82
Contents lists available at ScienceDirect
Polyhedron
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Dissymmetric ansa zirconocene complexes with di- and trisubstituted
indenyl ligands as catalysts for homogeneous ethylene homo- and
ethylene/1-hexene copolymerization reactions
⇑
Andrea M. Rimkus, Helmut G. Alt
Laboratorium für Anorganische Chemie, Universität Bayreuth, Postfach 101251, D-95440 Bayreuth, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Different routes for the synthesis of 1,2- and 1,2,3-substituted indene derivatives are described.
Representative substituents are: Me, Ph, PhCH2, PhCH2CH2, PhCH2CH2CH2, CH2CH = CH2. Subsequent
deprotonation of these substituted indenes and reaction with indenyl zirconium trichloride gave the cor-
responding dissymmetric bis(indenyl) zirconium complexes. After activation with methylaluminoxane
(MAO) these complexes show high activities both in ethylene homopolymerisation and ethylene/1-hex-
ene copolymerisation. The rate of comonomer incorporation can reach 33.3% (15/MAO). The copolymers
Received 29 November 2016
Accepted 16 January 2017
Available online 25 January 2017
Keywords:
1,2 and 1,2,3-substituted indenes
Dissymmetric ansa metallocene complexes
Bis(indenyl) complexes
Catalytic ethylene mono- and
copolymerization
exhibit lower melting points than the homopolymers and their crystallinities
the homopolymers.
a are lower compared with
Ó 2017 Elsevier Ltd. All rights reserved.
Ethylene/hexene copolymers
1. Introduction
sity polyethylene’ (LDPE) [13–16]. Because of its excellent
properties, LLDPE is one of the most attractive polyolefins. Zirco-
nium complexes with substituted indenyl ligands are excellent
candidates for the copolymerisation of ethylene and 1-hexene.
Multinuclear or dissymmetric mononuclear complexes can be
used as catalysts to produce polyolefins with bimodal or multi-
modal molecular weight distributions [1–9]. Such polyolefins show
an advantageous processability because of their broad melting
range. Another option comprises the copolymerisation of at least
two monomers [10]. Suitable systems are ethylene and short chain
Bridged derivatives usually incorporate higher amounts of an
a-
olefin compared to the unbridged ones [17–19]. In the literature
the described routes for the synthesis of such complexes are cum-
bersome. Therefore it is essential to find better routes for the syn-
thesis of new 2-substituted indenyl complexes that give similar or
better copolymerisation results compared to the already existing
complexes. In this paper pathways to new 2-substituted indenyl
complexes are presented.
a-olefins like 1-hexene [11,12]. The copolymerisation of ethylene
and 1-hexene is a typical way to introduce short chain branches
into the linear polyolefin backbone to produce low density poly-
ethylene (LLDPE). An essential element of this process is the selec-
tivity of the catalyst towards ethylene and the respective
Since each catalyst incorporates different amounts of the
a
a
-olefin.
-olefin
into the polymer backbone resulting in polymers with different
branching patterns, it is possible to obtain a variety of new poly-
mers with different contents of comonomer and molecular weight
distributions. Compared to their corresponding homopolymers,
these copolymers exhibit different melting temperatures, crys-
tallinities and mechanical and optical characteristics. LLDPE shows
short chain branches, lower melting points and lower crystallini-
ties compared to ‘high density polyethylene’ (HDPE) and ‘low den-
2. Results and discussion
2.1. Synthesis of 2-bromoindene
An important starting compound for the preparation of 2-sub-
stituted indenes is 2-bromoindene (2) [20,21]. It was obtained in
a two step reaction from indene and N-bromosuccinimide (NBS)
in dimethylsulfoxide via a halohydrine reaction. The hydroxy
group of the obtained 1-hydroxy-2-bromoindane (1) was removed
in toluene under reflux catalysed by p-toluene sulfonic acid (p-
TosOH) to give 2-bromoindene (2) (Scheme 1). 2-Bromoindene
was then transferred to the Grignard compound 3 (Scheme 2).
⇑
Corresponding author.
E-mail address: helmut.alt@uni-bayreuth.de (H.G. Alt).
http://dx.doi.org/10.1016/j.poly.2017.01.021
0277-5387/Ó 2017 Elsevier Ltd. All rights reserved.

A.M. Rimkus, H.G. Alt / Polyhedron 126 (2017) 72–82
73
Scheme 1. Synthesis of 2-bromoindene (2) [20,21].
the main driving force of this reaction [27]. The alcohols 6–8 were
dehydrogenated with sulfuric acid (Scheme 6).
Different from the 12-hour period necessary for the dehydra-
tion of the indanols with para-toluene sulfonic acid, this method
only takes thirty minutes under reflux [30]. No noteworthy side
reactions were observed.
Scheme 2. Synthesis of 2-indenyl magnesium bromide (3).
2.5. Synthesis of dissymmetric unbridged indenyl zirconium complexes
2.2. Synthesis of 2-substituted indene compounds via Kumada
reactions
2-Substituted indene compounds and their corresponding sym-
metric group (IV) metal indenyl complexes are well described in
the literature [17,18]. Therefore, the goal was to obtain dissymmet-
ric di- and trisubstituted indenyl complexes. Two approaches will
be presented here: Either one substituted indenyl compound is
reacted with indenyl zirconium trichloride or two indenyl ligands
with different substituents are coordinated to a zirconium metal
centre (see Scheme 7).
In Kumada reactions, Grignard compounds and alkyl halides are
coupled in the presence of nickel catalysts like 1,3-bis-
diphenylphosphino-propane nickel dichloride [22,23]. 2-Bromoin-
dene (2) was reacted with allyl magnesium bromide to give 2-
allylindene (4) (Scheme 3). The reaction of 3 and allyl bromide also
gave 4 but in a much lower yield.
The Kumada reaction only worked smoothly with alkyl and
alkenyl magnesium halides, not with aryl Grignard compounds
giving side products.
Substituents R1–R5 can be alkyl, alkenyl, aryl or alkylaryl
groups.
2.5.1. Multisubstituted indenyl compounds
2.3. Palladium catalysed synthesis of 2-substituted indene compounds
More substituents can be introduced in positions one and three
of 2-substituted indenes. The 2-substituted indene derivatives
were deprotonated with n-butyl lithium and then reacted with
methyliodide respectively allylbromide. The reaction conditions
are very important to obtain the desired compounds. A reaction
period of twelve hours afforded 1,2,3-substituted indenes. To gain
the 1,2-substituted indene derivatives, the reaction time had to be
reduced to four hours and, additionally, the lithium salt, which was
produced in the first reaction step, had to be removed to get rid of
traces of unreacted n-butyl lithium. Since the degree of alkylation
can be controlled by choosing the appropriate reaction conditions,
both 1,2- and 1,2,3-substituted indene derivatives were synthe-
sised (see Schemes 8 and 9).
Indene was reacted with bromobenzene in the presence of a
palladium catalyst. The desired 2-phenylindene (5) was obtained
in a one step reaction after stirring for six hours at 100 °C (see
Scheme 4).
The reaction was not successful for allyl bromide or cyclohexyl
bromide; the yields were very low. Therefore, this route is only
partially useful to obtain 2-substituted indene compounds.
2.4. Synthesis of 2-substituted indene compounds from 2-indanone
Another method to obtain the desired 2-indene compounds is
the reaction of 2-indanone with Grignard reagents [25,26]. The
resulting alcohols need to be dehydrated in a second step.
Experiments showed that such Grignard reactions give several
side products, but their amounts can be minimized introducing
an intermediate step, where the Grignard compound was treated
with cerium trichloride before 2-indanone was added (Scheme 5)
[27–29]. Cerium trichloride is an oxophilic salt which can activate
carbonyl compounds by coordination. It also lowers the strong
base character of the Grignard compounds. This is most likely
2.5.2. Synthesis of the dissymmetric bis(indenyl) zirconium complexes
15 and 16
The synthesis of complexes 15 and 16 was carried out by depro-
tonation of the respective starting compound with n-butyl lithium
and reaction with indenyl zirconium trichloride. The substituted
indene compound was dissolved in diethylether and n-butyl
lithium was added. After stirring for 20 h, indenyl zirconium
trichloride was added resulting in the formation of light orange
Scheme 3. Synthesis of 2-allylindene (4) [24] via Kumada coupling.
Scheme 4. Synthesis of 2-phenylindene (5).

74
A.M. Rimkus, H.G. Alt / Polyhedron 126 (2017) 72–82
Scheme 5. Synthesis of 2-substituted indene compounds from Grignard reactions.
Scheme 6. Elimination of hydroxy groups of 2-indanols with sulfuric acid [31].
The half sandwich complexes and the 4,7-disubstituted indene
derivatives can then be prepared following the previously
described route (Section 2.5.2.). For olefin polymerisation reac-
tions, the dissymmetric bis(indenyl) zirconium complex 17 was
used as catalyst precursor (see Scheme 13).
Complexes 15–17 were characterized by 1H and 13C NMR spec-
troscopy, mass spectrometry and elemental analysis. Schemes 14
and 15 show the 1H and 13C NMR spectra of complex 17.
The 1H NMR spectrum of complex 17 shows a signal for the
methyl group (14) at d = 2.31 ppm. At d = 1.96 ppm and at
d = 2.59–2.96 ppm the signals of the methylene protons 7, 8, 20,
21 and 22 are located. The aromatic CH protons in the five mem-
bered indenyl ring give signals at d = 5.71, 5.77, 5.86, 6.14 and
6.20 ppm. The protons 5 and 6 give two signals because of rac
and meso isomers. The signals for the remaining protons of the
indenyl and phenyl rings appear between d = 6.92 bis 7.62 ppm.
In the 13C NMR spectrum, the methyl group 18 is visible at
d = 18.9 ppm. The five carbon atoms of the CH2 groups 10, 11, 28,
29 and 30 give signals at d = 30.4, 32.2, 33.7, 35.7 and 36.2 ppm.
The aromatic methine carbon atoms of the phenyl and indenyl
rings (1–4, 13–17, 20, 21 und 32–36) are found between
d = 125.3 and 128.5 ppm. The aromatic methine carbon atoms of
the five membered indenyl rings (6, 8 und 24–26) appear between
d = 103.0 and 115.6 ppm. The nine quarternary carbon atoms give
signals in the range between d = 125.2 and 143.5 ppm.
The mass spectrum of complex 15 (Scheme 16) shows the
molecular ion at m/z = 508. The loss of an allyl group and both
chloro ligands results in the formation of a fragment with m/
z = 393. The peak at m/z = 355 arises from the loss of the unsubsti-
tuted indenyl group and a chloro ligand. Further elimination of the
allyl group and the second chloro ligand results in the peak at m/
z = 277. The peak at m/z = 232 arises from the loss of the fragment
indenyl-Zr(Cl2). The base peak at m/z = 191 can be assigned to a 2-
phenylindenyl moiety (see Scheme 17).
Scheme 7. Unsymmetrical bis(indenyl) zirconium complex.
dissymmetric bis(indenyl) zirconium complexes. The complexes
could be isolated in yields up to 50% (see Scheme 10).
2.5.3. Dissymmetric bis(indenyl) zirconium complexes from 2-
substituted indenyl zirconium trichloride and substituted indene
derivatives
In the above described route multisubstituted indene deriva-
tives were reacted with indenyl zirconium trichloride. 2-Substi-
tuted indenyl zirconium trichloride half sandwich complexes are
obtained in a two step reaction from 2-substituted indene deriva-
tives treated with tributyl tin chloride followed by addition of zir-
conium tetrachloride [32] (see Scheme 11).
These half sandwich complexes can then be reacted with differ-
ently substituted indene compounds like 4,7-disubstituted indene
derivatives. Those indene derivatives are obtained by reacting
potassium tert-butylate with 2,5-diketones [33] and cyclopentadi-
ene in methanol [34] (see Scheme 12).
Scheme 8. Synthesis of 1,2-disubstituted indene compounds.

A.M. Rimkus, H.G. Alt / Polyhedron 126 (2017) 72–82
75
Scheme 9. Synthesis of 1,2,3-trisubstituted indene compounds.
Scheme 10. Synthesis of dissymmetric bis(indenyl) zirconium complexes.
Scheme 11. General synthesis of indenyl zirconium trichloride half sandwich complexes.
2.6. Results of homogeneous ethylene polymerisation and ethylene/1-
hexene copolymerisation with complexes 15–17/MAO
In the past 25 years metallocene dichloride complexes with
group IV metals in combination with methylaluminoxane (MAO)
have proven as excellent catalysts for olefin polymerization
[11,35, and references therein]. All synthesised bis(indenyl) zirco-
nium complexes were used as catalyst precursors for homoge-
Scheme 12. General synthesis of 4,7-disubstituted indene compounds [34].
neous
ethylene
polymerisation
and
ethylene/1-hexene
copolymerisation reactions.
For ethylene homopolymerisation experiments the complexes
were activated with methylaluminoxane (MAO) applying a ratio
Zr:Al = 1:2500. The polymerisation runs were routinely performed
at a temperature of 60 °C over 1 h employing an ethylene pressure
of 10 bar. As a solvent n-pentane was used. The polymerisation
results, viscosity molecular weight and DSC data are given in
Table 1.
For homogeneous ethylene/1-hexene copolymerisation reac-
tions the complexes were activated with methylaluminoxane
(MAO) applying a ratio Zr:Al = 1:2500. The polymerisation runs
were routinely performed at a temperature of 60 °C over 1 h
employing an ethylene pressure of 10 bar. The addition of 1-hex-
ene was set to 20 g/h. As solvent n-pentane was used. The poly-
merisation results and the DSC data are given in Table 2.
The activities of the three bis(indenyl) zirconium complexes in
copolymerisation reactions are in general lower than in ethylene
Scheme 13. Complex 17 as catalyst precursor for olefin polymerisation.

76
A.M. Rimkus, H.G. Alt / Polyhedron 126 (2017) 72–82
Scheme 14. 1H NMR spectrum of complex 17.
Scheme 15. 13C NMR spectrum of complex 17 in chloroform-d.
homopolymerisation experiments. The bulkyness of the indenyl
substituents rises from 15 to 17, which hinders the incorporation
of the comonomer 1-hexene and the growth of the polymer chain.
Complex 15/MAO shows the lowest activity in both polymerisation
types. It is likely, that the allyl substituent interacts with the active
centre and hinders the coordination of 1-hexene.
a certain sequence in the polymer chain [36]. The nomenclature
of the different carbon groups was taken from Carman et. al.
[37]. The labelling
ad+ means for example, that one methylene
group has one methine group as direct neighbour, but the second
methine group is at least four more methyl groups away.
All 13C NMR spectra show the typical spectrum for ethylene/1-
hexene copolymers (Scheme 18).
2.7. Examination of the chain structure of the ethylene/1-hexene
copolymers obtained with complexes 15–17/MAO using 13C NMR
spectroscopy
The values from the 13C NMR spectra were compared with the
data given in Table 3. The signals at d = 38.8, 34.2 and 33,8 ppm
(region B and C) are assigned for ‘‘EHE”- respectively ‘‘EHEE”-
units where one 1-hexene unit (H) is located between two or
more ethylene units (E). Long ethylene chains in the copolymer
show signals at d = 30.4 and 30.0 ppm. There, a 1-hexene unit is
The chain structures of the copolymers were determined with
13C NMR analysis. Each signal in the spectrum can be assigned to

A.M. Rimkus, H.G. Alt / Polyhedron 126 (2017) 72–82
77
Scheme 16. Mass spectrum of complex 15.
activity ethylene [kg PE/mol Zr • h]
22000
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
19910
activity ethylene/1-hexene [kg PE/mol Zr • h]
13160
5760
4260
2990
4210
15
16
17
Scheme 17. Comparison of the polymerisation activities of the bis(indenyl) zirconium complexes 15–17/MAO in ethylene homopolymerisation and ethylene/1-hexene
copolymerisation reactions.
Table 1
Ethylene homopolymerisation with the dissymmetric bis(indenyl) zirconium complexes 15–17. Polymerisation conditions: solvent: 250 ml n-pentane, activator: MAO, Zr:
Al = 1:2500, 60 °C, 10 bar ethylene, 1 h.
Compound
Activity (kg/molZr h)
M
g
(g/mol)
Tm [°C]
D
Hm [J/g]
a [%]
15
16
17
4260
13160
19910
167500
43000
175200
136.50
132.14
136.81
144.51
205.33
160.27
50
71
55
Table 2
Ethylene/1-hexene copolymerisation with the dissymmetric bis(indenyl) zirconium complexes 15–17. Polymerisation conditions: solvent: 250 ml n-pentane, activator: MAO (Zr:
Al = 1:2500), 60 °C, 10 bar ethylene, 1 h, flow rate (1-hexene): 20 g/h.
Compound
Activity (kg/molZr h)
Tm [°C]
D
Hm [J/g]
a [%]
15
16
17
2990
5760
4210
125.39
125.41
127.34
91.57
102.47
28.74
32
35
10
followed by several ethylene units (HEEE) or only ethylene units
can be found ((EEE)n). The region G and H signals contain no
specific sequence information. 1-Hexene units surrounded by
ethylene units or more 1-hexene units next to each other are pos-
sible. The signal at d = 27.1 ppm (region E) can be assigned to
‘‘HHEE”-units and signal d = 29.3 ppm to ‘‘HHE”-units. Comparing
the amount of signals that can be assigned to units where 1-hex-
ene is surrounded by ethylene to other units leads to the conclu-
sion that the incorporated 1-hexene units are mainly separated
by at least two ethylene units in the obtained copolymers. Blocks
with more 1-hexene units incorporated next to each other do not
exist (region A). The same is true for units, where the 1-hexene
units are only separated by one ethylene unit (region F) (see
Scheme 19).
2.8. Comparison of the properties of the polyethylenes and 1-hexene/
ethylene copolymers obtained with complexes 15–17/MAO
The viscosity molecular weights M of the polymers obtained
g
with the complexes 15–17/MAO show a similar trend as the activ-
ities of the catalysts. The molecular weight of the homopolymer
from complex 16/MAO (43,000 g/mol) represents the lowest value

78
A.M. Rimkus, H.G. Alt / Polyhedron 126 (2017) 72–82
Scheme 18. 13C NMR spectrum of the copolymer obtained with 17/MAO.
Table 3
Correlation of the signals of the 13C NMR spectrum to the sequences in the polymer chain [32] (E = ethylene unit, H = 1-hexene unit).
Region
C
Sequence
dtheor. [ppm]
15
16
17
dexp. [ppm]
dexp. [ppm]
dexp. [ppm]
A
a a
a a
a a
HHHH
HHHE
EHHE
41.4
40.9
40.2
B
CH
EHE
38.1
37.8
37.8
37.8
C
CH
4B
HHE
35.9
35.4
35.0
HHH
HHEH
EHEH
HHEE
HHE
a c
a c
a
d+
34.9
4B
a
4B
CH
d+
EHEE
EHE
HHH
34.5
34.1
33.5
34.2
33.8
34.2
33.8
34.2
33.8
D
c c
HEEH
HEEE
(EEE)n
EHE
HHE
HHH
30.9
30.5
30.0
29.5
29.3
29.2
c
d+
30.4
30.0
30.4
30.0
30.4
30.0
d+ d+
3B
3B
3B
29.3
29.3
29.3
E
F
b d+
EHEE
HHEE
27.3
27.1
b d+
27.1
27.1
27.1
b b
b b
b b
EHEHE
HHEHE
HHEHH
24.5
24.4
24.3
G
2B
1B
EHE + HHE + HHH
EHE + HHE + HHH
23.4
14.1
23.4
23.4
14.2
23.4
14.2
H
On the basis of the integrals in the 1H NMR spectra, the incorporation of 1-hexene in mol% was calculated (Table 4).
among the tested catalysts. The molecular weights of the other
two homopolymers were determined as 167,500 g/mol und
175,200 g/mol. Since the molecular weights were calculated by
viscosimetry measurements, it is not possible to compare the
molecular weights of the homopolymers and the copolymers
because the viscosimetry measurements reflect a too low value
for the copolymers (see Table 4).
ing peaks in the melting curve. The higher one is at Tm = 127.5 °C
and the lower one at Tm = 112 °C. Obviously the copolymer consists
of different polyethylene types (see Scheme 21).
The crystallinities
a were calculated from the melting enthal-
pies of the polymers. The values of the copolymers were again
lower than those of the homopolymers (Scheme 22).
For the copolymer obtained with 17/MAO, the crystallinity
a
DSC analyses showed clear differences in the polymer proper-
ties. The homopolymers exhibit melting points between 132 and
137 °C, the copolymers are about 10 °C lower (see Scheme 20).
The melting point of the homopolymer obtained from 15/MAO
at 132 °C is lower than the ones of the other two polymers. The
melting points of the copolymers from 15/MAO and 17/MAO are
at 125 °C. The copolymer obtained with 17/MAO shows two melt-
was calculated as 10% corresponding to a mainly amorphous struc-
ture. This polymer is best for further processing. The crystallinities
of the other two copolymers were distinctively higher (32% und
34%). The crystallinities of the ethylene homopolymers obtained
from 15/MAO and 17/MAO were determined as 50%. The highest
crystallinity was found for the polymer obtained with 16/MAO
(70%).

A.M. Rimkus, H.G. Alt / Polyhedron 126 (2017) 72–82
79
M
η
175200
200000
180000
160000
140000
120000
100000
80000
60000
40000
20000
0
167500
43000
15
16
17
Scheme 19. Comparison of the molecular weight M of the polymers obtained with 15–17/MAO.
g
Table 4
0
Incorporation of 1-hexene into the copolymers obtained with the complexes 15–17/
5
10
15
20
25
30
35
40
MAO.
127.5°C
Copolymer of complex
Incorporation [%]
1-hexene
112°C
Ethylene
15/MAO
16/MAO
17/MAO
33.3
16.7
12.5
66.7
83.3
87.5
3. Experimental
54
70
87
103
120
137
154
temperature [°C]
3.1. NMR spectroscopy
Scheme 21. Melting curve of the copolymer obtained with 17/MAO.
The spectrometers Bruker ARX 250 and Varian (Inova 400) were
available for the recording of the NMR spectra. The samples were
prepared under inert atmosphere (argon) and routinely recorded
at 25 °C. The chemical shifts in the 1H NMR spectra are referred
to the residual proton signal of the solvent (d = 7.24 ppm for CDCl3;
d = 5.32 ppm for CD2Cl2, d = 7.15 ppm for C6D6) and in 13C NMR
spectra to the solvent signal (d = 77.0 ppm for CDCl3; d =
53.5 ppm for CD2Cl2; d = 128.0 ppm for C6D6).
min, final temperature 290 °C) the end temperature was held for
15 min (plateau phase).
At the Zentrale Analytik of the University of Bayreuth GC/MS
spectra were routinely recorded with a HP5890 gas chromatograph
in combination with MAT 95 mass detector.
3.3. Mass spectrometry
Mass spectra were routinely recorded at the Zentrale Analytik
of the University of Bayreuth with a VARIAN MAT CH-7 instrument
(direct inlet, EI, E = 70 EV) and a VARIAN MAT 8500 spectrometer.
3.2. GC/MS spectroscopy
GC/MS spectra were recorded with a Thermo Focus gas chro-
matograph in combination with a Thermo DSQ mass detector. A
30 m HP-5MS fused silica column (film 0.25
lm, flow 75 ml/min,
3.4. Elemental analysis
split ratio 50:1), helium (4.6) was applied as the carrier gas. Using
a 30 m column, the routinely performed temperature program
started at 50 °C (2 min). After a heating phase of 24 min (10 K/
The analyses were performed with a VarioEI III CHN instrument.
The raw values of the carbon, hydrogen and nitrogen contents
meting points PE
melting points coopolymer
mp [°C]
138
136
134
132
130
128
126
124
15
16
17
Scheme 20. Comparison of the melting points of the ethylene homopolymers and the ethylene/1-hexene copolymers of complexes 15–17/MAO.

80
A.M. Rimkus, H.G. Alt / Polyhedron 126 (2017) 72–82
crystallinity α PE
crystallinity α Copolymer
α [%]
80
70
60
50
40
30
20
10
0
15
16
17
Scheme 22. Crystallinities
a
of the homo- and copolymers produced with the complexes 15–17/MAO.
were multiplied with calibration factors (calibration compound:
acetamide).
vent was evaporated. 1-Hydroxy-2-bromoindane (1) was obtained
quantitatively as a mixture of diastereomers.
1-Hydroxy-2-bromoindane (42.61 mmol) was then dissolved in
300 ml of toluene, and a catalytic amount of para-toluene sulfonic
acid was added. After stirring the reaction mixture for 3 days under
reflux with a Dean-Stark trap, the toluene was evaporated and n-
pentane was added. The suspension was filtered over silica and
the solvent removed. The product was obtained as yellow needles
after recrystallisation. Yield: 60–90%. 1H NMR: 7.35 d (1H, Ar-H),
7.29 d (1H, Ar-H), 7.23 t (1H, Ar-H), 7.16 dt (1H, Ar-H), 6.91 s
(1H, Ar-H), 3.58 s (2H, Ind-CH2). 13C NMR: 144.0, 142.6, 124.9
(Cq), 132.9, 126.7, 124.8, 123.2, 120.2 (Ar-CH), 45.5 (Ind-CH2).
MS: m/z 196 M+Å (8), 115 M – Br (100).
3.5. Differential scanning calorimetry (DSC)
The thermal attributes of the polymer samples were examined
in a Diamond DSC instrument (Perkin-Elmer). After drying the
polymer samples, an amount of 4–7 mg was weighed into a stan-
dard aluminium pan. The sealed pan was then introduced into
the instrument. The measurements were performed with the fol-
lowing temperature program:
(1) Heating phase (10 K/min) from 50 °C to 160 °C; 1. cooling
phase (ꢀ10 K/min) to 50 °C.
3.7.2. Synthesis of 2-allylindene (4)
(2) Heating phase (10 K/min) from 50 °C to 160 °C; 2. cooling
phase (ꢀ10 K/min) to 50 °C.
Allyl magnesium bromide (5 mmol) in 25 ml diethylether was
slowly added to a solution of 2-bromoindene (5 mmol) and Ni
(dppp)Cl2 (0.05 mmol), dissolved in 25 ml diethylether and stirred
over night at room temperature. Diluted hydrochloric acid was
used for the following hydrolysis. The organic layer was separated
and dried over sodium sulfate. The evaporation of the solvent and
recrystallization from n-pentane yielded compound 4. Yield: 55%.
1H NMR: 7.12–7.39 m (4H, Ar-H), 6.55 s (1H, Ar-H), 5.85 m (1H,@
CH), 5.03 m (2H,@CH2), 3.35 s (2H, Ind-CH2), 3.23 d (2H, CH2).
13C NMR: 145.1, 144.6, 142.7 (Cq), 135.2 (@CH), 131.7, 129.6,
128.4, 126.6, 125.9 (Ar-CH), 115.9 (@CH2), 38.1 (Ind-CH2), 34.9
(CH2). MS: m/z 156 M+Å (55), 141 M – CH3 (42), 128 M – C2H4
(68), 115 Indenyl (100).
The temperature was corrected linearly to indium
(mp = 156.6 °C), for calibration the melting enthalpy of indium
was used (DHm = 28.45 J/g).
For polyethylene, the maxima of the second heating cycle were
D
D
Hm
Hm0
used. For the calculation of the crystallinity, the correlation
was used.
DSC, for
a
¼
D
Hm was obtained from the second heating cycle of the
D
H0m as the melting enthalpy extrapolated for 100% crys-
talline polyethylene a value of 290 J/g [38] was used.
3.6. Viscosimetry
The molecular weight M was determined with an Ubbelohde
g
3.7.3. Synthesis of 2-phenylindene (5)
precision capillary viscosimeter (0C, Schott-Geräte) in cis/trans
decaline at 135 0.1 °C. The heating bath used was a CT 1450
instrument and the measurement unit an AVS 310. The samples
were weighed into Erlenmeyer vessels and dissolved in the corre-
sponding amount of decaline during 3–4 h at 140–150 °C. Insolv-
able parts were filtered off with glass wool. For the
To a solution of bromobenzene (6.54 mmol), indene (15 mmol)
and triethylamine (25.9 mmol) in 30 ml of dimethylformamide,
bis-(tri-o-tolyl-phosphine)-palladium dichloride (0.14 mmol) was
added. The reaction mixture was stirred at 100 °C for six hours,
then evaporated and the residue dissolved in a mixture of n-pen-
tane and dichloromethane (100:3). The solution was then filtered
over silica, the solvent removed and the product recrystallized
from n-pentane. Yield: 37%. 1H NMR: 7.62 d (2H, Ar-H), 7.42–
7.50 q (1H, Ar-H), 7.34–7.40 m (3H, Ar-H), 7.21–7.28 m (3H, Ar-
H), 7.15–7.19 m (1H, Ar-H), 3.78 s (2H, Ind-CH2). 13C NMR: 146.3,
145.3, 143.1, 136.1 (Cq), 128.7 (2C), 127.6, 126.6, 126.4, 125.7
(2C), 124.7, 123.7, 120.9 (Ar-CH), 39.0 (Ind-CH2). MS: m/z 192 M+Å
(100), 115 M – C6H5 (10).
determination of M , reference sheets were available. To reduce
g
errors, each polymer sample was weighed and measured twice.
The possible error in the molecular weight calculation is 10%.
3.7. Synthesis
3.7.1. Synthesis of 2-bromoindene (2)
To a solution of freshly distilled indene (42.61 mmol) in 200 ml
of dimethyl sulfoxide and water (82.2 mmol), N-bromosuccinimide
(43.29 mmol) was added. After stirring for 12 h, water was added
slowly to the reaction mixture. The organic layer was extracted
with diethylether four times, dried over sodium sulfate and the sol-
3.7.4. Synthesis of the 2-substituted indene compounds 5, 9 und 10
Cerium trichloride (45 mmol) was quickly and finely ground to
a powder in a mortar and placed in a 30 ml two-necked flask. The
flask was immersed in an oil bath and heated gradually to 135–

A.M. Rimkus, H.G. Alt / Polyhedron 126 (2017) 72–82
81
140 °C and evacuated (ca. 0.1 torr). After maintenance of the cer-
ium chloride at a constant temperature for 1 h, a magnetic stirring
bar was placed in the flask and the cerium chloride was completely
dried in vacuo by stirring at the same temperature for an addi-
tional 1 h. The hot flask was filled with argon gas and then cooled
in an ice bath. THF (5 ml) was added all at once with vigorous stir-
ring. The ice bath was removed and the suspension was stirred
overnight under argon at room temperature. Meanwhile the Grig-
nard reagent was prepared. To magnesium powder (75 mmol,
50 mesh) 50 ml tetrahydrofuran and a small piece of iodine was
added. Then 10 ml of the corresponding bromo compound
(45 mmol) in 100 ml of tetrahydrofuran was added. After the
iodine colour disappeared, the remaining bromide solution was
added with a dropping funnel and the solution was stirred over
night. The cerium trichloride suspension was again immersed in
an ice bath and the Grignard reagent was added after filtration.
After stirring for 1.5 h at 0 °C, 2-indanone (30 mmol), dissolved in
tetrahydrofurane (50 ml), was added and the stirring was contin-
ued for 120 minutes. The reaction mixture was treated with
10 ml of a 10% aqueous acetic acid. The product was extracted into
ether, and combined extracts were washed with brine and NaHCO3
solution and brine and dried with sodium sulfate. The solvent was
evaporated and the alcohols 6–8 were obtained and dehydro-
genated without further characterisation.
over sodium sulfate. The solvent was again removed. Yield: 58%.
(13) 1H NMR: 7.29–7.04 m (9H, Ar-H), 4.26 q (1H, Ind-H), 2.12 s
(2H, CH2), 1.54 d (3H, CH2), 1.53 s (3H, CH3). GC/MS: m/z 234 M+Å
(21), 219 M – CH3 (10), 204 M – 2 CH3 (11), 129 M – CH3 – C7H7
(15), 115 Indenyl (8), 105 M – 2 CH3 – C10H12 (100).
(14) GC/MS: m/z 286 M+Å (4), 245 M – C3H5 (100), 217 M – C3H5
– C2H4 (52), 203 M – 2 C3H5 (90), 167 M – C3H5 – C6H5 (24), 141 M
– C3H5 – C2H4 – C6H5 (87).
3.7.7. Synthesis of the bis(indenyl) zirconium complexes 15 and 16
To the indenyl derivatives 12 respectively 13 (5.44 mmol), dis-
solved in 50 ml diethylether, n-butyllithium (5.44 mmol, 2.5 M in
hexane) was added at ꢀ78 °C. The reaction mixture was stirred
over night at room temperature. Then indenyl zirconium trichlo-
ride (5.44 mmol) was added at ꢀ78 °C. The mixture was stirred
for four more hours and then the solvent was removed. The residue
was extracted with toluene and filtered over sodium sulfate. The
filtrate was evaporated and complexes 15 and 16 were obtained
after crystallization at ꢀ25 °C. Yield: 36–42%. (15) 1H NMR: 7.54–
7.63 m (2H, Ar-H), 7.51 d (1H, Ar-H), 7.37–7.47 m (5H, Ar-H),
7.32–7.36 m (1H, Ar-H), 7.22–7.30 m (2H, Ar-H), 7.12–7.21 m
(2H, Ar-H), 7.02–7.11 m (1H, Ar-H), 6.38 s (1H, Ar-H), 6.26 t (1H,
Ar-H), 6.14–6.19 m (1H, Ar-H), 5.72–5.83 m (1H, ACH@), 4.73–
4.92 dd (2H,@CH2), 3.76–3.81 m (1H, Ind-CH-Allyl), 1.48–1.90 m
(2H, CH2). 13C NMR: 134.2, 133.9, 129.3, 126.8, 123.8, 119.2 (Cq),
116.0 (@CH2), 135.2, 128.8, 128.5, 128.2, 126.5, 126.4, 126.3,
126.2, 125.9, 125.4, 125.0, 124.4, 124.3, 120.8, 104.9, 104.2, 104.1
(Ar-CH), 99.9 (@CH), 30.9 (CH2). MS: m/z 508 M+Å (2), 393 M – 2
Cl – C3H5 (25), 355 M – Ind – Cl (6), 277 M – Ind – C3H5 – 2 Cl
(15), 232 M – IndZrCl2 (45), 191 M – IndZrCl2 – C3H5 (100). Ele-
mental analyses: Found: C, 63.3; H, 3.85. Calc: C, 63.8; H, 4.38.
(16) 1H NMR: 7.54–7.58 dd (1H, Ar-H),7.43–7.49 dd (1H, Ar-H),
7.32–7.41 m (2H, Ar-H), 7.18–7.24 m (4H, Ar-H), 7.10–7.15 m (3H,
Ar-H), 7.02–7.08 m (2H, Ar-H), 6.89–6.98 m (2H, Ar-H), 6.78–
6.84 m (1H, Ar-H), 2.87 s (2H, CH2), 0.82 s (3H, CH3), 0.79 s (3H,
CH3). 13C NMR: 149.9, 146.1, 145.4, 145.1, 142.8, 141.7, 126.8,
114.7 (Cq), 134.1, 128.5, 128.4, 128.3, 126.3, 126.1, 126.5, 125.8,
125.4, 125.0, 124.6, 124.0, 122.2, 120.9, 118.4, 104.1 (Ar-CH),
29.7 (CH2), 14.1 (2C) (CH3). MS: m/z 512 M+Å (0), 437 M – 2 Cl
(5), 397 M – Ind (6), 345 M – Ind – Cl – CH3 (4), 308 M – Ind – 2
Cl – CH3 (8), 233 M – IndZrCl2 (32), 218 M – IndZrCl2 – CH3
In a second step, the hydroxyl groups of the alcohols were
removed by addition of 25 ml of 9 M sulfuric acid and stirring for
30 minutes at 110 °C. For neutralisation, a 20% sodium hydroxide
solution was added. The mixture was washed with dichloro-
methane twice, filtered over sodium sulfate and the solvent was
removed to obtain the product. Yield: 70–75%. (9) 1H NMR:
7.12–7.39 m (9H, Ar-H), 6.54 s (1H, Ar-H), 3.84 s (2H, Ind-CH2),
3.30 s (2H, CH2). GC/MS: m/z 206 M+Å (35), 129 M – C6H5 (21),
115 M – C7H7 (23), 91 benzyl (100).
(10) 1H NMR: 7.10–7.36 m (9H, Ar-H), 6.54 s (1H, Ar-H), 3.32 s
(2H, Ind-CH2), 2.78–2.97 m (4H, CH2). GC/MS: m/z 220 M+Å (15),
129 M – C7H7 (100).
3.7.5. Synthesis of 1- and 2-disubstituted indene compounds 11 and
12
A 2-substituted indene compound (5 mmol) was dissolved in
diethylether (100 ml), and then n-butyl lithium (5 mmol, 2.5 M
in hexane) was added. After stirring for four hours at room temper-
ature, the lithium salt was filtered and washed to remove traces of
unreacted n-butyl lithium. The salt was then diluted in diethy-
lether and allylbromide respectively methyliodide (6 mmol) was
added. The mixture was then stirred for four hours. The solvent
diethylether was evaporated, toluene was added and the solution
was filtered over sodium sulfate. The solvent was again removed.
Yield: 45%. (11) 1H NMR: 7.55 d (2H, Ar-H), 7.44 t (2H, Ar-H),
7.39 d (2H, Ar-H), 7.25–7.31 m (2H, Ar-H), 7.19–7.24 m (1H, Ar-
H), 7.09 s (1H, Ar-H), 3.93 q (1H, Ind-H), 1.35 dd (3H, CH3). 13C
NMR: 152.5, 149.5, 143.5, 135.4 (Cq), 128.6 (2C), 127.3, 126.8
(2C), 126.7, 125.8, 124.8, 122.8, 121.0 (Ar-CH), 44.0 (Ind-CH),
17.2 (CH3). MS: m/z 206 M+Å (100), 191 M – CH3 (77), 129 M –
C6H5 (18).
(100), 203 M – IndZrCl2 – 2 CH3 (26), 127 M – IndZrCl2 – C7H7
–
CH3 (18). Elemental analyses: Found: C, 63.9; H, 4.49. Calc: C,
63.5; H, 4.74.
3.7.8. NMR and elemental analysis data for complex 17
To 4-methyl-7-(2-phenylpropylyl)-indene, dissolved in 50 ml
diethylether, an equivalent of n-butyllithium was added at
ꢀ78 °C. The reaction mixture was stirred over night at room tem-
perature. Then an equivalent of 2-(2-phenylethyl)-indenyl zirco-
nium trichloride was added at ꢀ78 °C. The mixture was stirred
for four more hours and then the solvent was removed. The residue
was extracted with toluene and filtered over sodium sulfate. The
filtrate was evaporated and the complexes 15 and 16 were
obtained after crystallization at ꢀ25 °C.
(12) GC/MS: m/z 232 M+Å (30), 191 M – C3H5 (100).
1H NMR: 7.62 t (2H, Ar-H), 7.20–7.33 m (9H, Ar-H), 7.09 d (3H,
Ar-H), 6.92 s (2H, Ar-H), 6.20 s (1H, Ar-H), 6.14 s (1H, Ar-H), 5.86 d
(1H, Ar-H), 5.77 d (1H, Ar-H), 5.71 d (1H, Ar-H), 2.90–2.96 m (2H,
CH2), 2.79–2.85 m (2H, CH2), 2.59–2.74 m (4H, CH2), 2.31 s (3H,
CH3), 1.96 s (2H, CH2). 13C NMR: 143.5, 142.2, 141.1, 135.6,
132.1, 129.2, 129.2, 125.2, 125.2 (Cq), 128.5 (2C), 128.4 (2C),
128.33, 128.26 (4C), 126.2, 126.0, 125.7, 125.31 (2C), 125.27 (2C),
115.6, 105.6, 103.8, 103.3, 103.0 (Ar-CH), 36.2, 35.7, 33.7, 32.2,
30.4 (CH2), 18.9 (CH3). Elemental analyses: Found: C, 69.5; H,
5.68. Calc: C, 68.8; H, 5.45.
3.7.6. Synthesis of 1-, 2- and 3-trisubstituted indene compounds 13
and 14
A 2-substituted indene compound (5 mmol) was dissolved in
diethylether (100 ml), and then treated with n-butyl lithium
(5 mmol, 2.5 M in hexane). After stirring over night at room tem-
perature, allylbromide respectively methyliodide (6 mmol) was
added and the mixture was again stirred for four hours. The solvent
was evaporated. Toluene was added and the solution was filtered

82
A.M. Rimkus, H.G. Alt / Polyhedron 126 (2017) 72–82
3.7.9. Polymerisation of ethylene with the bis(indenyl) zirconium
complexes 15–17
Acknowledgement
The corresponding zirconium complex (1–5 mg) was dissolved
in 5 ml of toluene. Then methylaluminoxane (MAO, 30% in toluene,
Zr:Al ratio = 1:2500) was added to the solution and filled into a
flask with 250 ml of n-pentane. A 1 l autoclave was evacuated
and filled with argon several times and the catalyst mixture was
added. The mixture was then stirred for 1 hour at 60 °C with an
ethylene pressure of 10 bar. The ethylene pressure was released
and after cooling to room temperature the polymer mixture was
taken out of the reactor. The obtained polymer was washed with
hydrochloric acid, water and acetone and it was finally dried in
vacuo.
We thank Saudi Basic Industries Corporation (SABIC) - Saudi
Arabia for the financial support.
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3.7.10. Copolymerisation of ethylene and 1-hexene with the bis
(indenyl) zirconium complexes 15–17
The corresponding zirconium complex (1–5 mg) was dissolved
in 5 ml of toluene. Then methylaluminoxane (MAO, 30% in toluene)
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4. Conclusions
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The goal of this work was the synthesis of new metallocene
complexes and to test their behaviour in ethylene/1-hexene
copolymerisation reactions. Three different routes for the prepara-
tion of 2-substituted indenyl compounds have been investigated.
The modified Grignard reaction applying cerium trichloride to
obtain tri-substituted indene derivatives was the most successful
synthesis route. Several ways for the synthesis of dissymmetric
bis(indenyl) zirconium complexes were examined and the
obtained complexes were active both in homogeneous ethylene
polymerisation and ethylene/1-hexene copolymerisation. The
comparison of the obtained homo- and copolymers showed clear
differences of the polymer properties. The copolymers have lower
crystallinities and lower melting points than the ethylene
homopolymers and are therefore useful for industrial processing.
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