Dialkoxy-substituted, C1-symmetric metallocenes: Synthesis and catalytic behavior in the propylene polymerization reaction

Article abstract of DOI:10.1515/znb-2004-0217

The synthesis of a series of C₁-symmetric metallocene complexes rac-[1-(5,6-dialkoxy-2-methyl-1-η⁵-indenyl)-2-(9-η ⁵-fluorenyl)ethane]zirconium dichlorides (alkyl: n-butyl, n-hexyl, n-octyl, n-decyl) is described. These co

Full text of DOI:10.1515/znb-2004-0217

Dialkoxy-Substituted, C1-Symmetric Metallocenes:
Synthesis and Catalytic Behavior in the Propylene Polymerization
Reaction
Martin Schlo¨gl and Bernhard Rieger
University of Ulm, Department of Materials and Catalysis,
Albert-Einstein-Allee 11, D-89069 Ulm, Germany
Reprint requests to Prof. Dr. B. Rieger. Fax: +49 (0)731 5023039.
E-mail: bernhard.rieger@chemie.uni-ulm.de
Z. Naturforsch. 59b, 233 – 240 (2004); received October 20, 2003
The synthesis of a series of C1-symmetric metallocene complexes rac-[1-(5,6-dialkoxy-2-methyl-
1-η5-indenyl)-2-(9-η5-fluorenyl)ethane]zirconium dichlorides (alkyl: n-butyl, n-hexyl, n-octyl, n-
decyl) is described. These complexes are versatile catalysts in the polymerization of propylene af-
ter in situ activation with triisobutylaluminum (TIBA) and Ph3C[B(C6F5)4] in toluene and heptane
solution. All catalysts show higher solubility and improved polymerization properties in industrially
used hydrocarbon solvents (e.g. heptane). However, the molecular weights and isotacticity values of
the resulting polypropylene materials are decreased compared to the ethoxy-bridged analogue rac-
[1-(5,6-ethylenedioxy-2-methyl-η5-indenyl)-2-(9-η5-fluorenyl)ethane]zirconium dichloride. A pos-
sible explanation is based on enhanced interaction of the active catalyst centers with Al(III) scavenger
molecules even at low Al : Zr ratios, leading to reversible chain transfer.
Key words: Metallocene Catalysis, Dialkoxy Substitution, Propylene Polymerization
Introduction
Results and Discussion
One significant advantage in metallocene polymer-
ization catalysis [1] is the easy possibility to design
polymer microstructures and the corresponding mate-
rial properties by variation of the catalyst structure.
This can be performed by various methods. The na-
ture of the cocatalyst [2] certainly plays a decisive role
as well as the variation of the ligand framework [3].
Recently, we published a series of papers on asym-
metric, ”dual-side“, catalysts that produce high perfor-
mance polypropylene elastomers [4]. Here, a substi-
tution in 5,6-position of the indenyl moiety has a ma-
jor influence on the polymerization properties concern-
ing a shift to higher molecular weight PP materials.
However, the partially reduced solubility of these com-
pounds in hydrocarbon solvents, like hexane or hep-
tane, hinders a broader application [5, 6]. In this con-
text we synthesized a series of zirconocene derivatives
containing 5,6-di(n-alkoxy)indenyl ligands [7, 8] and
tested their catalytic behavior in the polymerization
of propylene in toluene and heptane solution reveal-
ing significant changes compared to their non-alkoxy-
substituted counterparts and to an ethoxy-bridged ana-
logue.
Ligand synthesis
The 1,2-ethylidene-bridged, fluorenyl-indenyl lig-
ands 7a – d are built up from the 5,6-dialkoxyindene
anions and an equimolar amount of 9-(2-bromoethyl)-
fluorene 6 via a convergent route (Scheme 1). The flu-
orene derivative 6 is obtained by a modified litera-
ture procedure from fluorene after deprotonation with
n-BuLi and treatment with excess 1,2-dibromoethane.
The indene derivatives are formed within several
steps: The etherification of 1 with the correspond-
ing n-alkyl bromide (10 mol-% excess) using K2CO3
in DMF gives the dialkoxybenzenes. A subsequent
Friedel-Crafts cycloacylation with methacroyl chloride
at −78 ◦C leads to the indanones 3a – d using AlCl3 as
Lewis acid in 10 mol-% excess. Lower quantities result
in non-cyclic side products, whereas higher amounts of
aluminum chloride cause partially cleavage of the ether
functionalities. The synthesis of the diastereomeric in-
danoles 4a – d is performed quantitatively by reduction
with NaBH4. These are transformed directly to the de-
sired indene precursors 5a– d by dehydration with p-
toluenesulfonic acid at 70 ◦C.
c
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M. Schlo¨gl – B. Rieger · Dialkoxy-Substituted Metallocene Catalysts
Scheme 1. Ligand synthesis.
Synthesis of zirconium complexes
minum (TIBA; ratio 100:1) and subsequent addition
of Ph3C[B(C6F5)4] (ratio 10:1). Complete alkylation
The synthesis of the rac-[1-(5,6-dialkoxy-2-methyl-
1-η5-indenyl)-2-(9-η5-fluorenyl)ethane] zirconocene
dichlorides 8a – d is performed by deprotonation of
compounds 7a – d and treatment with an equimolar
amount of ZrCl4 (Scheme 2). Re-crystallization from
toluene or toluene/hexane mixtures give the orange,
solid products in good to moderate yield [9].
with TIBA proceeds only after heating for one hour at
50 ◦C, which nearly doubles polymerization activities,
compared to experiments without preliminary heating.
The polymerizations were repeated several times with
reproducible results [10].
Formula 3.
The polymerization behavior of catalysts 8a – d in
toluene solution (Table 1: Run 1 – 18) comprises mod-
erate catalyst activities at 30 C with no significant
◦
Scheme 2. Catalyst synthesis.
variation concerning the monomer pressure, but can be
enhanced by a factor of 2 by raising the polymeriza-
tion temperature to 50 ◦C. The isotacticity values are at
Polymerization reactions
The propylene polymerization behavior of com- both temperatures in the range of 10 – 15% revealing
plexes 8a – d is tested at various temperatures and atactic material. The obtained molecular weights are
monomer concentrations in toluene and heptane so- between 20000 and 70000 g/mol and show no signif-
lution. The results are compared to an analogous set icant dependency on the monomer pressure, tempera-
of experiments using a similar catalyst structure con- ture and variation of the alkoxy-chain length. The re-
taining an ethylene dioxid group at the 5,6-position sults are compared to an analogue set of polymeriza-
of the indenyl moiety 9 (Formula 3). Activation is tion reactions in toluene using structure 9 (Fig. 3). This
performed by in situ treatment with triisobutylalu- catalyst is known to polymerize α-olefins according to
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M. Schlo¨gl – B. Rieger · Dialkoxy-Substituted Metallocene Catalysts
235
Table 1. Polymerization results with 8a – d and 9 / TIBA / Ph3C[B(C6F5)4] in toluene.
Activityb
[mmmm]c
a
Run
Cat.
Amount
[ µmol]
Temp.
[◦C]
Pressure
[bar]
[C3]
[g/mol]
Yield
[g]
tp
[h]
Mw
PD
1
2
3
4
8a
8a
8a
8a
5
5
10
5
30
30
30
50
3.0
5.0
7.0
6.5
1.3
3.0
5.0
3.0
2.63
7.89
8.43
7.69
0.52
0.75
0.43
0.30
20000
50000
30000
40000
1.7
4.7
3.6
3.5
800
700
800
11.3
10.0
11.6
12.0
1700
5
6
7
8
8b
8b
8b
8b
10
10
10
5
30
30
30
50
3.0
5.0
7.0
6.5
1.3
3.0
5.0
3.0
10.13
7.50
7.50
7.50
0.91
0.50
0.51
0.30
30000
30000
30000
40000
4.2
4.6
3.6
5.9
900
500
300
11.2
12.2
10.4
12.6
1700
9
10
11
12
13
8c
8c
8c
8c
8c
10
10
10
5
30
30
30
40
50
3.0
5.0
7.0
5.7
6.5
1.3
3.0
5.0
3.0
3.0
8.44
11.25
11.25
11.25
11.25
1.00
0.67
0.58
0.50
0.30
40000
40000
40000
40000
50000
2.9
2.8
2.7
3.1
4.8
700
600
900
1500
2500
10.3
10.6
10.9
11.8
14.9
5
14
15
16
17
18
8d
8d
8d
8d
8d
10
10
10
5
30
30
30
40
50
3.0
5.0
7.0
5.7
6.5
1.3
3.0
5.0
3.0
3.0
7.50
7.50
7.50
11.25
11.25
0.83
0.70
0.55
0.55
0.28
40000
40000
40000
50000
70000
2.7
3.5
3.3
3.7
4.3
600
400
300
1400
2700
10.8
11.2
13.4
12.6
15.3
5
19
20
21
22
a
9
9
9
9
2
2
2
2
30
30
30
50
3.0
5.0
7.0
6.5
1.3
3.0
5.0
3.0
2.70
4.50
9.00
8.70
0.50
0.50
1.00
0.50
120000
130000
160000
100000
2.0
3.2
3.5
2.9
2100
1500
1000
2900
50.7
43.9
43.3
63.3
Relative against PP standards; b kg PP/[molZr]*[C3]*h; c isotacticity [%].
Table 2. Polymerization results with 8d / TIBA / Ph3C[B(C6F5)4] in heptane.
a
Run
Cat.
Amount
[ µmol]
10
10
5
Temp.
[◦C]
30
30
30
Pressure
[bar]
3.0
5.0
7.0
[C3]
[g/mol]
0.7
1.7
3.0
Yield
[g]
6.19
9.38
9.38
9.38
tp
[h]
0.88
0.35
0.27
0.33
Mw
PD
Activityb
[mmmm]c
23
24
25
26
a
8d
8d
8d
8d
30000
50000
70000
30000
4.0
3.4
2.4
6.1
1000
1600
2300
4100
9.7
9.6
8.1
10
50
4.0
0.7
12.7
Relative against PP standards; b kg PP/[molZr]*[C3]*h; c isotacticity [%].
the earlier proposed “back-skip” mechanism. Here, the trations of 1 – 10 µm/ml. Experiments with 9 showed
polymerizations expose results expected for this cata- only insufficient catalyst solubility under these condi-
lyst family (Table 1: Run 19 – 22). Molecular weights tions and therefore, no catalyst activity in propylene
are enhanced by approximately a factor of 2 compared polymerizations occurred. Exemplary polymerization
to 8a – d and higher MW values are obtained at lower experiments of 8d in heptane solution (Table 2) were
temperatures. The most explicit differences occur at performed under conditions similar to run 1 – 22 (Ta-
the PP isotacticities: Complex 9 produces PP compris- ble 1). The resulting molecular weights (MW : 30000–
ing [mmmm] sequences from 50% to 65% and the iso- 70000 g/mol) and isotacticity values ([mmmm]: ap-
tacticities increase at the higher temperatures, as ex- prox. 10%) are completely in the same range com-
pected [4]. Also the declining [mmmm] values with pared to polymerization experiments in toluene. How-
higher monomer concentration at polymerization tem- ever, there are significantly increased polymer yields
peratures of 30 ◦C are typical for the “back-skip” poly- (up to factor 8) relative to experiments in toluene.
merization mechanism.
A probable explanation for these unexpected exper-
The n-alkoxy substituted metallocenes 8a – d reveal imental results might be seen in an enhanced interac-
a significantly increased solubility in hydrocarbon sol- tion of active sites with aluminum scavenger molecules
vents (hexane, heptane) compared to 9. Solubility tests [11]. In MAO activated polymerization reactions with
of 8a – d in heptan gave clear solutions within concen- 9 [4b] in toluene a reversible chain transfer to Al cen-
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236
M. Schlo¨gl – B. Rieger · Dialkoxy-Substituted Metallocene Catalysts
ters is supported by deuterium labeling experiments. moieties is underway to suppress the influences of Al-
Such a reversible transport process results in lower MW coordination at oxygen containing ligand fragments.
and [mmmm] values, due to the existence of the two
enantiomeric zirconocene species with opposite enan- Experimental Section
tiofacial discrimination of prochiral propene monomer
molecules [12]. Reduced Al : catalyst ratios within
in situ TIBA/borate activation method of 9 suppress
this transfer effect and lead again to higher tactici-
ties and molecular weights. Apparently, different cir-
cumstances exist in polymerizations using 8a – d and
TIBA/Ph3C[B(C6F5)4]: Here, molecular weights and
isotacticities of the obtained polymer materials are low,
even after MAO-free activation processes. A possible
explanation for this effect might be found in the am-
phiphilic nature of the catalyst sites, bearing polar “Zr-
head functions” and apolar n-alkoxy substituents. In
apolar media, in our case especially in heptane, this
might lead to a close contact of oxygen-substituted
zirconocenium centers and Al(III)-activator molecules
via formation of (e.g. inverse micellar) aggregates.
This assumption proposal cannot be supported experi-
mentally (light scattering, etc.) yet, due to the high sen-
sitivity of the cationic catalyst sites.
General remarks
The rac-[1-(5,6-ethylenedioxy-2-methyl-η5-indenyl)-2-
(9-η5- fluorenyl)ethane]zirconium dichloride 9 [4b] and
Ph3C[B(C6F5)4] [13] were synthesized according to lit-
erature procedures, 9-(2-bromoethyl)-fluorene 6 [14] and
the 1,2-dialkoxybenzenes 2a – d [15] according to modified
literature methods. All synthetical work (except the syn-
thesis of 2a – d) was done using standard Schlenk tech-
niques under argon atmosphere. The 1-bromoalkanes, 1,2-
dihydroxybenzene, methacroyl chloride, p-toluenesulfonic
acid, fluorene, 1,2-dibromoethane, n-BuLi (1.6 molar in hex-
ane), K2CO3, Na2SO4, NaBH4, AlCl3 and ZrCl4 were pur-
chased from Aldrich. Triisobutylaluminum (1 molar in hex-
ane) was purchased from Crompton, solvents for synthesis
and polymerizations were purchased from Merck and dried
via distillation over LiAlH4.
NMR analysis of the prepared compounds was performed
on a Bruker DRX 400 spectrometer at ambient temperatures
and referenced to the CDCl3 solvent signal. Elemental anal-
ysis (Vario EL Elementar) and mass spectra (Finnigan MAT
SSQ 7000) were determined by the Microanalytical Lab-
oratory of the University of Ulm. PP analysis: 13C NMR
spectra were recorded on a Bruker AMX 500 spectrometer
(C2D2Cl4, 90 ◦C, 125 MHz, 5 mm probe) in the invers gated
decoupling mode with a 3 s pulse delay and a 45 ◦C pulse
to attain conditions close to the maximum signal-to-noise
ratio. Molecular weights and molecular weight distributions
Conclusion
Here we present a series of new, C1-symmetric
metallocene complexes containing diverse 5,6-di(n-
alkoxy)indenyl ligands. These structures are ver-
satile catalysts for the polymerization of propy-
lene in toluene and heptane solution using in situ
were determined by gel permeation chromatography (GPC,
◦
TIBA/Ph3C[B(C6F5)4] activation. The introduction of Waters 2000, 140 C in 1,2,4-trichlorobenzene) relative to
polypropylene standards.
apolar alkyl segments into the ligand structure leads
to a good solubility in hydrocarbon solvents compared
to non-alkyl substituted counterparts. Additionally, the
resulting polymerization activities of 8a – d in heptane
can be enhanced compared to experiments in toluene.
This is an advantageous fact as hydrocarbons like hep-
tane can be used as solvents in industrial polymer-
ization processes. However, the obtained polypropy-
lenes reveal significant changes in the catalyst prop-
erties compared to similar non-substituted structures
resulting in reduced polymer molecular weights and
isotacticities. A hypothetical explanation is based on
an extended interaction between Lewis acidic Al cen-
ters of the TIBA co-activator and the active catalyst.
This would lead to a reversible chain transfer, which is
accepted for analogue systems and results in reduced
MW - and [mmmm] values. The synthesis of analogous
Synthesis
1, 2-Dialkoxybenzenes 2a – d
A suspension of 750.0 mmol (M: 138.21 g/mol; 103.66 g)
of K2CO3, 250.0 mmol (M:110.11 g/mol; 27.53 g) of 1,2-
dihydroxybenzene 1 and 600.0 mmol of 1-bromoalkane in
500 ml of DMF was stirred for 12 h at 80 ◦C in a 2 l round-
bottom flask with reflux condenser. After cooling to room
temperature 500 ml of H2O und 800 ml of Et2O was added.
After separation of remaining inorganic salts the H2O / DMF
phase was washed with 200 ml of water. The combined ether
phases were extracted with 2 × 200 ml of H2O and distilled
to dryness.
2a: Yield: 48.20 g (M: 222.33 g/mol; 217.1 mmol; 86.9%)
red oil. – 1H NMR (400 MHz, CDCl3): δ = 1.02 (t, 6H,
CH3), 1.54 (m, 4H, -CH2CH3), 1.83 (m, 4H, -OCH2CH2-),
catalyst structures bearing n-alkyl-substituted indenyl 4.03 (q, 4H, -OCH2), 6.91 (s, 4H, Har). – 13C NMR
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237
(400 MHz, CDCl3): δ = 14.4, 19.8; 32.0, 69.5, 114.8, −OCH2CH2-), 2.66 (m, 2H, CH2-indenyl), 3.29 (m, 1H, CH-
114.8, 121.6, 149.9. – MS (GC-MS): m/z = 222 [M+]. – indenyl), 4.01 (dt, 4H, -OCH2-), 6.75 (s, 1H, Har), 7.10 (s,
C14H22O2: calcd. C 75.63, H 9.97; found C 75.49, H 9.81.
2b: Yield: 62.91 g (M: 278.44 g/mol; 226.3 mmol;
90.5%) red liquid. – 1H NMR (400 MHz, CDCl3): δ =
0.93 (t, 6H, CH3), 1.36 (m, 8H, -CH2CH2CH3), 1.51 (m,
4H, -OCH2CH2CH2-), 1.83 (m, 4H, -OCH2CH2-), 4.00 (t,
4H, -OCH2), 6.89 (s, 4H, Har). – MS (GC-MS): m/z =
1H, Har). – 13C NMR (400 MHz, CDCl3): δ = 14.3, 17.0,
22.9, 22.9, 25.9, 26.0, 29.2, 29.3, 31.8, 31.8, 35.1, 42.6,
69.4, 69.5 106.5, 108.9, 129.1, 148.8, 149.1, 149.9, 156.0,
208.6. – MS (GC-MS): m/z = 347 [M+]. – C22H34O3: calcd.
C 76.26, H 9.89; found C 76.13, H 9.80.
3c: Yield: 15.17 g (M: 402.62 g/mol; 37.67 mmol;
278 [M+]. – C18H30O2: calcd. C 77.65, H 10.86; found C 37.7%) white solid after re-crystallization in 50 ml of
77.62, H 10.79.
MeOH. 1H NMR (400 MHz, CDCl3): δ = 0.83 (t, 6H, CH3
“chain”), 1.23 (s, 3H, CH3-indenyl), 1.25 – 1.35 (m, 20H,
-OCH2CH2(CH2)5-), 1.46 (m, 4H, -OCH2CH2-), 2.52 (m,
2H, CH2-indenyl), 3.20 (m, 1H, CH-indenyl), 4.01 (dt, 4H, -
OCH2-), 6.83 (s, 1H, Har), 7.13 (s, 1H, Har). – 13C NMR
(400 MHz, CDCl3): δ = 12.3, 14.9, 20.8, 24.2, 24.2, 10
signals at 27.2 – 30.0, 40.4, 67.3, 67.5, 104.4, 106.7, 112.7,
127.0, 146.7, 147.4, 153.9, 206.4. – MS (GC-MS): m/z =
403 [MH+]. – C26H42O3: calcd. C 77.56, H 10.51; found C
77.85, H 10.30.
3d: Yield: 19.28 g (M: 458.73 g/mol; 42.02 mmol;
42.0%) white solid after re-crystallization in 50 ml of
MeOH. 1H NMR (400 MHz, CDCl3): δ = 0.81 (t, 6H, CH3
“chain”), 1.23 (s, 3H, CH3-indenyl), 1.15 – 1.51 (m, 28H,
-OCH2CH2(CH2)7-), 1.78 (m, 4H, -OCH2CH2-), 2.56 (m,
2H, CH2-indenyl), 3.20 (m, 1H, CH-indenyl), 3.98 (dt, 4H,
−OCH2-), 6.76 (s, 1H, Har), 7.10 (s, 1H, Har). – MS (GC-
MS): m/z = 460 [MH+]. – C30H50O3: calcd. C 78.55, H
10.99; found C 78.40, H 10.91.
2c: Yield: 52.28 g (M: 334.55 g/mol; 157.4 mmol; 62.9%)
red oil. – 1H NMR (400 MHz, CDCl3): δ = 0.89 (t,
6H, CH3), 1.30 (m, 16H, -(CH2)4CH3), 1.48 (m, 4H, -
OCH2CH2CH2-), 1.81 (m, 4H, -OCH2CH2-), 3.99 (t, 4H, -
OCH2), 6.88 (s, 4H Har). – 13C NMR (400 MHz, CDCl3):
δ = 13.9, 22.4, 22.5, 22.6, 26.0, 28.1, 28.7, 69.2, 114.1,
114.4, 120.9, 149.2. – MS (GC-MS): m/z = 334 [M+]. –
C22H38O2: calcd. C 78.99, H 11.45; found C 78.91 H, 11.30.
2d: Yield: 12.18 g (M: 390.66 g/mol; 187.3 mmol; 74.9%)
white needles after re-crystallization in 100 ml of EtOH. 1H
NMR (400 MHz, CDCl3): δ = 0.91 (t, 6H, CH3), 1.20 – 1.55
(m, 28H, CH2), 1.71 – 1.90 (m, 4H, -O-CH2CH2-), 3.98 (t,
4H, -OCH2-), 6.89 (s, 4H, Har). – 13C NMR (400 MHz,
CDCl3): δ = 14.2, 22.8, 26.2, 29.4, 29.5, 29.6, 29.7, 29.7,
32.0, 69.4, 114.3, 114.3, 121.1, 149.4. – C26H46O2: calcd. C
79.94 H 11.87; found C 80.02 H 11.41.
5,6-Dialkoxy-2-methylindan-1-ones 3a – d
14.67 g of AlCl3 (M: 133.34 g/mol; 110 mmol) were sus-
pended in 100 ml of dichloromethane ◦in a 500 ml Schlenk
flask, the mixture was cooled to −78 C and 100 mmol of
methacroyl chloride was added. A solution of 100 mmol of
1,2-dialkoxybenzene in 100 ml of CH2Cl2 was added over
1 h. After stirring 12 h at room temperature the suspension
was cooled to −78 ◦C and hydrolyzed with 100 ml of H2O.
The organic phase was washed with 2 × 100 ml of water,
dried with Na2SO4 and evaporated to dryness.
3a: Yield: 13.13 g (M: 290.41 g/mol; 45.2 mmol; 45,2%)
white solid after re-crystallization from 50 ml of EtOH and
washing with 20 ml of MeOH. 1H NMR (400 MHz, CDCl3):
δ = 0.94 (t, 6H, CH3 “chain”), 1.26 (s, 3H, CH3-indenyl),
5,6-Dialkoxy-2-methylindan-1-oles 4a-d
30.0 mmol of 3a – d and 30 mmol of NaBH4 (M:
37.80 g/mol; 1.13 g) in 100 ml of EtOH were stirred for 24 h
at room temperature in a 500 ml Schlenk flask. After neutral-
ization with HCl, 100 ml of H2O and 100 ml of Et2O were
added. The organic phase was separated and washed with
2 × 100 ml of water. Drying with Na2SO4 and evaporating
to dryness lead to white solids which were converted directly
to the corresponding indenes 5a – d without purification.
5,6-Dialkoxy-2-methylind-1-enes 5a – d
The indanoles 4a – d were dissolved in 100 ml of toluene,
1.48 (m, 4H, -OCH2CH2CH2-), 1.80 (m, 4H, -OCH2-CH2), 0.57 g of p-toluenesulfonic acid (M: 190.22; 3.0 mmol) was
2.60 (m, 2H, CH2-indenyl), 3.21 (m, 1H, CH-indenyl), 4.00 added and the mixture was stirred for 1 h at 70 C. After
◦
(t, 4H, −OCH2-), 6.80 (s, 1H, Har), 7.13 (s, 1H, Har). – washing with 2 × 100 ml of H2O and drying with Na2SO4
13C NMR (400 MHz, CDCl3): δ = 14.5, 17.3 19.9, 31.6, the solvent was removed via distillation.
35.4, 42.9, 69.5, 106.8, 109.2, 129.4, 149.1, 149.9, 156.3,
208.9. – MS (GC-MS): m/z = 291 [M+]. – C18H26O3: calcd.
C 74.45, H 9.02; found C 74.41, H 8.99.
5a: Yield: 3.98 g (M: 274.41 g/mol; 14.5 mmol; 48.3% re-
garding to 3a) white crystals after re-crystallization in 30 ml
of EtOH. 1H NMR (400 MHz, CDCl3): δ = 0.96 (t, 6H,
3b: Yield: 11.89 g (M: 346.51 g/mol; 34.36 mmol; 34.4%) CH3 “chain”), 1.49 (m, 4H, -OCH2CH2CH2-) 1.78 (m, 4H,
white solid after re-crystallization in 50 ml of EtOH and -OCH2CH2-), 2.09 (s, 3H, CH3-indenyl), 3.19 (s, 2H, CH2-
washing with 20 ml of MeOH. 1H NMR (400 MHz, CDCl3): indenyl), 3.97 (t, 4H, -OCH2-), 6.36 (s, 1H, CH-indenyl),
δ = 0.90 (t, 6H, CH3 “chain”), 1.23 (s, 3H, CH3-indenyl), 6.81 (s, 1H, Har), 6.97 (s, 1H, Har). – 13C NMR (400 MHz,
1.35 – 1.55 (m, 12H, -OCH2CH2(CH2)3-), 1.90 (m, 4H, CDCl3): δ = 14.6, 17.3, 19.9, 32.2, 43.3, 70.2, 70.7, 107.5,
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238
M. Schlo¨gl – B. Rieger · Dialkoxy-Substituted Metallocene Catalysts
112.3, 127.3, 136.6, 140.0, 145.4, 147.1, 149.3. – MS (GC- (400 MHz, CDCl3): δ = 30.5, 36.6, 46.4, 120.1, 124.4, 127.2,
MS): m/z = 274 [M+]. – C18H26O2: calcd. C 78.79, H 9.55; 127.5, 141.1, 145.8. – MS (GC-MS): m/z = 273 [MH+]. –
found C 78.74, H 9.56.
C15H13Br: calcd. C 65.95, H 4.80; found C 65.89, H 4.77.
5b: Yield: 6.75 g (M: 330.52 g/mol; 20.4 mmol; 68.1%
regarding to 3b) white solid after re-crystallization in 20 ml
of EtOH. 1H NMR (400 MHz, CDCl3): δ = 0.89 (t, 6H, CH3
“chain”), 1.33 (m, 8H, -OCH2CH2CH2(CH2)3-), 1.47 (m,
4H, -OCH2CH2CH2-), 1.79 (m, 4H, -OCH2CH2-), 2.10 (s,
3H, CH3-indenyl), 3.19 (s, 2H, CH2-indenyl), 3.97 (t, 4H, -
OCH2-), 6.35 (s, 1H, CH-indenyl), 6.81 (s, 1H, Har), 6.97 (s,
1H, Har). – 13C NMR (400 MHz, CDCl3): δ = 14.7, 17.3,
23.3, 26.4, 30.2, 32.2, 42.3, 70.5, 71.0, 107.4, 112.3, 127.4,
136.6, 140.0, 145.4, 147.1, 149.2. – MS (GC-MS): m/z =
331 [M+]. – C22H34O2: calcd. C 79.95, H 10.37; found C
79.88, H 10.32.
5c: Yield: 7.61 g (M: 386.62 g/mol; 19.7 mmol; 65.6% re-
garding to 3c) white needles after re-crystallization in 30 ml
of MeOH. 1H NMR (400 MHz, CDCl3): δ = 0.83 (t, 6H,
CH3 “chain”), 1.29 (m, 16H, -OCH2CH2CH2(CH2)4-), 1.41
(m, 4H, -OCH2CH2CH2-), 1.75 (m, 4H, -OCH2CH2-), 2.01
(s, 3H, CH3-indenyl), 3.10 (s, 2H, CH2-indenyl), 3.95 (t, 4H,
-OCH2-), 6.30 (s, 1H, CH-indenyl), 6.78 (s, 1H, Har), 6.90
(s, 1H, Har). – 13C NMR (400 MHz, CDCl3): δ = 14.0, 16.6,
22.6, 29.2, 29.3, 29.4, 29.5, 31.7, 42.5, 69.7, 70.2, 104.4,
106.7, 111.5, 126.6, 125.8, 139.2, 144.6, 146.4, 148.5. – MS
(GC-MS): m/z = 386 [MH+]. – C26H42O2: calcd. C 80.77,
H 10.95; found C 80.61, H 10.84.
[1-(5,6-Dialkoxy-2-methylinden-1-yl)-2-
(9-fluorenyl)]ethanes 7a – d
20,0 mmol of 5a – d were degassed and dissolved in
70 ml of a mixture of toluene/dioxane (10:1) in a 250 ml
◦
Schlenk flask. After cooling to −78 C 12.5 ml of n-BuLi
(1.6 molar in hexane; 20.0 mmol) were added. The obtained
suspension was stirred for 2 h at room temperature, trans-
ferred to a dropping funnel and added to a solution of 9-(2-
bromoethyl)fluorene 6 in 50 ml of toluene (250 ml Schlenk
flask) via 2 h. The mixture was stirred at room temperature
for 12 h and washed with 2 × 100 ml of water. The organic
phase was dried with Na2SO4 and a yellow solid was ob-
tained after removing the solvent.
7a: Yield: 5.74 g (M: 466.67 g/mol; 12.3 mmol; 61.55%)
white powder after washing with 300 ml of isopropanol. 1H
NMR (400 MHz, CDCl3): δ = 0.99 (m, 6H, CH3-“chain”),
1.42 (m, 2H, CH2-bridge), 1.52 (m, 4H, −O(CH2)2CH2-),
1.69 (m, 2H, CH2-bridge), 1.80 (m, 4H, −OCH2CH2-), 1.87
(s, 3H, CH3-indenyl), 3.03 (t, 1H, CH-indenyl), 3.86 (t, 1H,
FluH), 4.00 (m 4H −OCH2-), 6.32 (s, 1H, olefinic CH-
indenyl), 6.70 (s, 1H, Har indenyl), 6.80 (s, 1H, Har in-
denyl), 7.25 – 7.75 (m, 8H, Har fluorenyl). – MS (GC-MS):
m/z = 466 [M+]. – C33H38O2: calcd. C 84.94, H 8.21; found
C 84.81, H 8.20.
7b: Yield: 7.97 g (M: 522.78 g/mol; 15.2 mmol; 76.4%)
white solid after re-crystallization in 50 ml of isopra-
panol. 1H NMR (400 MHz, CDCl3): δ = 0.92 (m, 6H,
CH3-“chain”), 1.35 (m, 2H, CH2-bridge), 1.41 (m, 12H,
-O(CH2)2(CH2)3-), 1.70 (m, 2H, CH2-bridge), 1.80 (m, 4H,
-OCH2CH2-), 1.88 (s, 3H, CH3-indenyl), 3.03 (t, 1H, CH-
indenyl), 3.86 (t, 1H, FluH), 4.00 (m, 4H, -OCH2-), 6.33 (s,
1H, olefinic CH-indenyl), 6.70 (s, 1H, Har indenyl), 6.80 (s,
1H, Har indenyl), 7.25 – 7.73 (m, 8H, Har fluorenyl). – MS
(GC-MS): m/z = 523 [M+]. – C37H46O2: calcd. C 85.01, H
8.87; found C 84.85, H 8.92.
5d: Yield: 7.78 g (M: 442.73 g/mol; 17.6 mmol; 58.6%
regarding to 3d) white solid after re-crystallization in 50 ml
1
EtOH. H NMR (400 MHz, CDCl3): δ = 0.91 (t, 6H, CH3
“chain”), 1.20 – 1.54 (m, 28H, -OCH2CH2(CH2)7-), 1.80
(m, 4H, -OCH2CH2-), 2.11 (s, 3H, CH3-indenyl), 3.22 (s,
2H, CH2-Indenyl), 4.00 (m, 4H, -OCH2-), 6.36 (s, 1H, CH-
indenyl), 6.82 (s, 1H, Har), 6.99 (s, 1H, Har). – MS (GC-
MS): m/z = 443 [MH+]. – C30H50O2: calcd. C 81.39, H
11.38; found C 81.21, H 11.29.
9-(2-Bromoethyl)-fluorene 6
10.00 g of fluorene (M: 166.22 g/mol; 60.2 mmol) were
degassed in a 500 ml Schlenk flask with a dropping funnel
7c: Yield: 7.92 g (M: 578.89 g/mol; 13.7 mmol; 68.4%)
and dissolved in 300 ml of Et2O. After cooling to −78 C white solid after re-crystallization in 50 ml of ethanol. 1H
37.6 ml of n-BuLi (1.6 molar in hexane; 60.2 mmol) were NMR (400 MHz, CDCl3): δ = 0.82 (m, 6H, CH3-“chain”),
added over 0.5 h. After stirring for 2 h at room temperature 1.22 (m, 20H, −O(CH2)2(CH2)5-), 1,25 (m, 2H, CH2-
the mixture was cooled again to −78 ◦C and 20.7 ml of 1,2- bridge), 1.40 (m, 4H, −OCH2CH2-), 1.60 (m, 2H, CH2-
dibromoethane (M: 187.9 g/mol; 240.8 mmol; δ: 2.18) were bridge), 1.81 (s, 3H, CH3-indenyl), 2.96 (t, 1H, CH-indenyl),
added rapidly. Stirring for 12 h at room temperature lead to a 3.79 (t, 1H, FluH), 3.92 (m, 4H, −OCH2-), 6.26 (s, 1H,
yellow suspension, which was washed twice with 100 ml of olefinic CH-indenyl), 6.63 (s, 1H, Har Indenyl), 6.73 (s, 1H,
H2O. Evaporation to dryness gave a brown solid, which was Har indenyl), 7.20 – 7.69 (m, 8H, Har fluorenyl). – MS (GC-
◦
re-crystallized from 50 ml of pentane.
MS): m/z = 579 [M+]. – C41H54O2: calcd. C 85.07, H 9.40;
found C 84.80, H 9.08.
Yield: 13.14 g (M: 273.17; 48.1 mmol; 74.9%) yel-
low solid. 1H NMR (400 MHz, CDCl3): δ = 2.53 (m,
7d: Yield: 6.53 g (M: 634.99 g/mol; 10.3 mmol; 51.4%)
2H, FluHCH2CH2-), 3.31 (t, 2H, -CH2Br), 4.17 (t, 1H, white solid after re-crystallization in 80 ml of ethanol.
FluH); 7.37, 7.42 and 7.78 (m, 8H, Har). – 13C NMR 1H NMR (400 MHz, CDCl3): δ = 0.89 (m, 6H, CH3
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239
“chain”), 1.28 (m, 28H, −O(CH2)2(CH2)7-), 1.48 (m, 2H, CDCl3): δ = 0.86 (m, 6H, CH3-“chain”), 1.15 – 1.50 and
CH2-bridge), 1.60 (m, 2H, CH2-bridge), 1.75 (m, 4H, 1.56 (m, together 20H, -O(CH2)2(CH2)5-), 1.76 and 1.89
−OCH2CH2-), 1.88 (s, 3H, CH3-indenyl), 3.03 (t, 1H, CH-
(m, each 2H, -OCH2CH2-), 2.14 (s, 3H, CH3-indenyl), 3.76
and 4.54 (m, each 1H, CH2-bridge to indenyl; diastereotope),
indenyl), 3.86 (t, 1H, FluH), 4.00 (m, 4H, −OCH2-), 6.34 (s,
1H, olefinic CH-indenyl), 6.70 (s, 1H, Har indenyl), 6.80 (s,
1H, Har indenyl), 7.21 – 7.78 (m, 8H, Har fluorenyl). – MS
(GC-MS): m/z = 634 [M+]. – C45H62O2: calcd. C 85.12, H
9.84; found C 85.02, H 9.87.
3.86 (t, 2H, CH2-bridge to fluorenyl), 4.06 (m, 4H, -OCH2-),
5.99 (s, 1H, olefinic CH-indenyl), 6.51 (s, 1H, Har indenyl),
7.07 (s, 1H, Har indenyl), 7.08 – 7.89 (m, 8H, Har fluo-
renyl). – C41H52Cl2O2Zr: calcd. C 66.58, H 7.04; found C
66.18, H 7.07.
rac-[1-(5,6-Dialkoxy-2-methyl-1-η5-indenyl)-
2-(9-η5-fluorenyl)ethane]zirconium dichlor-
i d e s 8a – d
8d: After washing with 50 ml of toluene the clear so-
lution was evaporated to dryness. Re-crystallization from
20 ml of toluene gave an orange solid. Yield: 1.70 g (M:
795.11 g/mol; 2.1 mmol; 42.86%). 1H NMR (400 MHz,
CDCl3): δ = 0.86 (m, 6H, CH3-“chain”), 1.15 – 1.50 and
1.55 (m, together 28H, -O(CH2)2(CH2)7-), 1.76 und 1.89
(m, each 2H, -OCH2CH2-), 2.14 (s, 3H, CH3-indenyl), 3.76
and 4.52 (m, each 1H, CH2-bridge to indenyl; diastereotope),
3.85 (t, 2H, CH2-bridge to fluorenyl), 4.05 (m, 4H, -OCH2-),
5.99 (s, 1H, olefinic CH-indenyl), 6.51 (s, 1H, Har indenyl),
7.07 (s, 1H, Har indenyl), 7.08 – 7.89 (m, 8H, Har fluo-
renyl). – C45H60Cl2O2Zr: calcd. C 67.92, H 7.55; found C
68.02, H 7.66.
5.0 mmol of 7 a – d were degassed and dissolved in 80 ml
of toluene/dioxane (10:1) in a 250 ml Schlenk flask. After
cooling to −78 ◦C 10.0 mmol of n-BuLi (1.6 molar in hex-
ane; 6.3 ml) was added. The mixture was stirred for 2 h
◦
at room temperature and re-cooled to −78 C. Adding of
5.0 mmol solid ZrCl4, stirring at room temperature for 12 h
and subsequent evaporation of the solvent lead to the rough
product. The purification was performed according to follow-
ing procedures:
8a: Washing with 2 × 50 ml of hot toluene resulted in a
clear solution which was concentrated to a volume of 20 ml.
◦
Propylene polymerizations
Cooling at −20 C over night gave an orange precipitate.
Yield: 0.93 g (M: 626.89 g/mol; 1.5 mmol; 29.56%). 1H
NMR (400 MHz, CDCl3): δ = 0.91 and 1,06 (t, each 3H,
CH3-“chain”), 1.43 and 1.59 (m, each 2H, -O(CH2)2CH2-),
1.75 and 1.90 (m, each 2H, -OCH2CH2-), 2.14 (s, 3H, CH3-
indenyl), 3.76 and 4.44 (m, each 1H, CH2-bridge to indenyl;
diastereotope), 3.87 (t, 2H, CH2-bridge to fluorenyl), 4.07
(m, 4H, -OCH2-), 5.99 (s, 1H, olefinic CH-indenyl), 6.51
(s, 1H, Har indenyl), 7.07 (s, 1H, Har indenyl), 7.08 – 7.88
(m, 8H, Har fluorenyl). – C33H36Cl2O2Zr: calcd. C 63.26, H
5.75; found C 63.87, H 5.86.
All reactions were performed in a 0.5 l Bu¨chi steel reac-
tor at constant pressure ( 0.1 bar) and temperature ( 1 ◦C).
First the desired amount of dichloro-zirconocene precursor
was dissolved in 10 ml of dry solvent under argon atmo-
sphere in a Schlenk flask and 100 equivalents of TIBA were
added. This solution was injected into the autoclave, which
had been charged with 2◦00 ml of the corresponding sol-
vent. After stirring at 50 C for one hour, the polymeriza-
tion temperature was adjusted and the reactor was floated
with propene up to the desired partial pressure. The poly-
merizations were started by injecting the appropriate amount
of PhC3+[B(C6F5)4]− (10 mmol/ml in toluene) via a pres-
sure burette. The monomer consumption was measured by
a calibrated gas flow meter (Bronkhorst F-111C-HA-33P),
and the pressure was kept constant during the entire poly-
merization period (Bronkhorst pressure controller P-602C-
EA-33P). Pressure, temperature and consumption of propene
were monitored and recorded online. The polymerization re-
actions were quenched by injecting 1 ml methanol. Reac-
tion mixtures were poured into acidified methanol (500 ml)
and the polymer precipitated. The product was filtered,
washed with excess methanol and dried in vacuum at 50 ◦C
overnight.
8b: After washing with 50 ml of toluene the clear solu-
tion was evaporated to dryness. Re-crystallization from 20 ml
of toluene/hexane (1:1) gave an orange solid. Yield: 0.82 g
(M: 682.90 g/mol; 1.2 mmol; 23.33%). 1H NMR (400 MHz,
CDCl3): δ = 0.87 and 0.95 (t, each 3H, CH3-“chain”), 1.28,
1.41 and 1.56 (m, together 12H, -O(CH2)2(CH2)3-), 1.75
and 1.91 (m, each 2H, -OCH2CH2-), 2.14 (s, 3H, CH3-
indenyl), 3.76 and 4.54 (m, each 1H, CH2-bridge to indenyl;
diastereotope), 3.86 (t, 2H, CH2-bridge to fluorenyl), 4.06
(m, 4H, -OCH2-), 5.99 (s, 1H, olefinic CH-indenyl), 6.51
(s, 1H, Har indenyl), 7.07 (s, 1H, Har indenyl), 7.08 – 7.89
(m, 8H, Har fluorenyl). – C37H44Cl2O2Zr: calcd. C 67.07, H
6.65; found: C 67.24, H 6.56.
8c: After washing with 50 ml of toluene the clear so-
lution was evaporated to dryness. Re-crystallization from
Acknowledgement
20 ml of toluene gave an orange solid. Yield: 2.22 g (M: The authors thank DFG “Deutsche Forschungsgemein-
739.01 g/mol; 3.0 mmol; 60.12%). 1H NMR (400 MHz, schaft”, SFB 569, for financial support of this research.
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240
M. Schlo¨gl – B. Rieger · Dialkoxy-Substituted Metallocene Catalysts
[1] For recent reviews see: a) H. H. Brintzinger, D. Fischer,
c) P. Lehmus, E. Kokko, O. Ha¨rkki, R. Leino,
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[8] Asymmetric complexes are easily accessible, also in
larger quantities, relative to their C2-symmetric ana-
logues: There is no material- and time-consuming sep-
aration of rac- and meso-species, which might be espe-
cially difficult or even impossible for alkyl-substituted
rac-derivatives.
R. Mu¨lhaupt, B. Rieger, R. M. Waymouth, Angew.
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[9] Purification of corresponding complexes with shorter
alkoxy substituents at 5,6-position (e.g.: ALK = ethyl)
failed due to insufficient solubility in apolar solvents.
[10] Activity values and molecular weight averages: 15%;
isotacticities: 5%.
[11] A second hypothesis might be seen in a change of the
polymerization mechanism by this 5,6-dialkoxy sub-
stitution. The long, flexible n-alkyl substituents might
cause an increased interaction with the growing poly-
mer chain. However, this assumption cannot explain
the reduced isotacticity values with 8a – d as well as
the lack of influence of the polymerization temperature
and the length of the n-alkyl substituents on the poly-
mer properties.
[4] a) U. Dietrich, M. Hackmann, B. Rieger, M. Klinga,
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polymer product due to their relatively high boil-
ing points. Therefore, lower boiling (and less toxic)
aliphatic hydrocarbons are predominantly used in in-
dustrial processes. Here, the insufficient solubility of
metallocene catalyst compounds is considered to be
a problem, which hinders a broader application. See: [12] For analogue examples of reversible chain trans-
M. K. Gosh, S. J. Maiti, Polym. Mater. 16, 113 (1999).
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Lamanna, R. A. Newmark, J. Stevens, D. E. Richard-
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