Dinuclear ansa zirconocene complexes containing a sandwich and a half-sandwich moiety as catalysts for the polymerization of ethylene

Article abstract of DOI:10.1016/S0022-328X(02)01673-X

Dinuclear ansa zirconocene complexes containing a half-sandwich and a sandwich moiety and their ligand precursors have been synthesized and characterized. After activation with methylalumoxane (MAO), these catalysts produce polyethylenes with bimodal mole

Full text of DOI:10.1016/S0022-328X(02)01673-X

Journal of Organometallic Chemistry 658 (2002) 259Á265
/
www.elsevier.com/locate/jorganchem
Dinuclear ansa zirconocene complexes containing a sandwich and a
half-sandwich moiety as catalysts for the polymerization of ethylene
Helmut G. Alt *, Rainer Ernst, Ingrid K. Bohmer
¨
Laboratorium fur Anorganische Chemie der Universitat Bayreuth, Lehrstuhl fur Anorganische Chemie II, Universitat Bayreuth, Postfach 10 12 51,
¨ ¨
¨
¨
Universitaetsstrasse 30, NW I, D-95440 Bayreuth, Germany
Received 16 May 2002; received in revised form 5 June 2002; accepted 14 June 2002
Abstract
Dinuclear ansa zirconocene complexes containing a half-sandwich and a sandwich moiety and their ligand precursors have been
synthesized and characterized. After activation with methylalumoxane (MAO), these catalysts produce polyethylenes with bimodal
molecular weight distributions in homogeneous and heterogeneous media. The catalyst performances and the polymer properties
were compared with mono nuclear reference catalysts. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Ansa zirconocene; Half-sandwich complexes; Dual site catalysts; Dinuclear complexes; Homogeneous and heterogeneous ethylene
polymerization
1. Introduction
[6Á13]. The model compounds presented in this paper
/
should provide the advantages of both the half-sand-
wich (high molecular mass) [14,15] and the sandwich
catalysts (low molecular mass) [5,16,17] and thus have
the potential of dual site catalysts.
In the last decade metallocene complexes have been
established as excellent catalysts for the polymerization
of ethylene and propylene [1Á5]. The produced poly-
/
olefins have narrow molecular weight distributions due
to identical active sites of the catalyst. However, this can
be disadvantageous for industrial processing. In order to
obtain broader molecular weight distributions, cumber-
some or costly approaches, like the blending of different
resins, are necessary. On the other side, in most cases, it
is not possible to obtain the desired multi modal resins
by mixing individual mono nuclear catalysts (averaging
effect). Therefore, it was the intention to solve this
problem with dinuclear complexes as catalyst precur-
sors. Two different active sites in one molecule should be
able to produce two different polymer chains with
different molecular weights. Other known dinuclear
complexes do not unify two different catalytic centers
2. Results and discussion
2.1. Synthesis of the ligand precursors
For the preparation of asymmetric dinuclear metallo-
cene complexes, a ligand precursor with an v-alkenyl
functionality is reacted catalytically with dichloro-
methylsilane in a hydrosilylation reaction [18]. This
chlorosilane intermediate then reacts in an SN2 reaction
[19Á23] with two equivalents of sodium cyclopentadie-
/
nide to form the ligand precursor (Scheme 1).
In the same manner, the following intermediates and
ligand precursors were synthesized:
* Corresponding author. Tel.:
552157
E-mail address: helmut.alt@uni-bayreuth.de (H.G. Alt).
ꢀ
/
49-921-552555; fax:
ꢀ/49-921-
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 6 7 3 - X

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H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259Á265
/
2.2. Synthesis of the dinuclear complexes 7Á
/
9
Compounds 7Á9 showed mid range activities in the
/
homogeneous polymerization which varied around the
value for reference catalyst 11/methylalumoxane
(MAO). The homogeneous polymerization with 9/
MAO exceeded the activity of the reference catalyst
11/MAO by ca. 50%. The activities from the hetero-
geneous experiments were generally lower than those
from the homogeneous series. This result confirms the
The reaction of such a ligand precursor with four
equivalents of butyllithium and two equivalents of
zirconium tetrachloride leads to the dinuclear complexes
7Á
The following complexes were synthesized in the same
manner:
/9 (Scheme 2).
For comparison purposes, the already known silyl
bridged sandwich complex 10 [20,23] (Scheme 3) and the
half-sandwich complex 11 [14,15] (Scheme 4) were
synthesized.
observations from other metallocene catalysts [17,20,23]
where heterogenization on silica gel causes decreasing
activities (Scheme 5). The lowest decrease is observed in
the case of the half-sandwich reference catalyst 11/
MAO.
The molecular masses of these polyethylenes pro-
2.3. Polymerization of ethylene
duced with the dinuclear catalysts 7Á9/MAO are
/
significantly higher than those of the reference catalyst
10/MAO; the trend of the molecular weights by hetero-
genization was not found to follow a certain rule
(Scheme 6).
Half-sandwich catalysts of titanium and zirconium
are known to produce polyethylenes of very high
molecular masses (ꢀ
silyl bridged bis(cyclopentadienyl) catalysts produce
resins with a significantly lower molecular mass (B
5ꢂ
105 g molꢁ1) [20,23]. The polymerization properties
of the asymmetric dinuclear complexes 7Á9 meet the
expectations (Table 1).
/
106 g molꢁ1) [13,14]. In contrast,
The polymer produced with catalyst 11/MAO shows
the highest Mn of the complete series both under homo-
and heterogeneous conditions. All other polymers vary
/
/
/
around Mnꢃ
80 kg molꢁ1 under homogeneous condi-
/

H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259Á
/265
261
Table 1
Polymerization data
Catalyst Activity g(PE)/g(Zr) h Mn
Tm
Mw
Mh
Mz
DHm
Crystallinity a
Polydispersity HI
Homogeneous conditions
7
51,000
102,000
146,000
109,000
89,000
81,210
505,500
138.1
147.3
50.8
1,654,000
406,400
6.2
8
85,230
614,800
139.3
145.8
50.3
2,098,000
498,900
7.5
Scheme 1. Synthesis of the intermediate 1 and the ligand precursor 2.
9
70,400
578,600
140.9
175.6
60.6
2,983,000
446,100
8.2
10
11
95,120
266,400
851,600
217,200
n.d.
n.d.
2.8
261,500
737,200
Scheme 2. Synthesis of the dinuclear complex 7.
1,981,000
717,200
2.8
Heterogeneous conditions (supported on silica gel)
7
42,000
77,000
33,400
406,950
139.3
147.8
50.9
1,679,990
316,000
12.2
Scheme 3. Synthesis of the mono nuclear silyl bridged metallocene
complex 10.
8
91,060
710,200
140.1
149.1
51.4
2,417,000
577,100
7.8
9
102,000
102,000
88,000
45,140
357,450
136.5
155.6
53.7
1,329,840
284,090
7.9
10
11
104,000
271,200
n.d.
n.d.
Scheme 4. Synthesis of the mono nuclear amido silyl half-sandwich
complex 11.
1,075,000
258,900
2.6
tions. Silica supported catalysts develop molecular
masses that are in the range of the homogeneously
produced polymers or below (Scheme 6).
Polymerization with the dinuclear complexes/MAO
gave resins with a broader molecular mass distribution
width HI than with mononuclear complexes. The
196,100
488,300
2,008,000
416,900
2.5
n.d., not determined.
polydispersities observed were between HIꢃ6.2 and
/

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H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259Á265
/
at 25,000 g molꢁ1 by the sandwich component of
catalyst 7. This conclusion can be derived from the
properties of the monomeric reference catalysts and the
produced polymers.
The HT-GPC curve does not always show two
separate maxima but a distinct broadening of the
molecular mass distribution relative to the mononuclear
catalysts.
Polymerization with a 1:1 mixture of 10/MAO and
11/MAO does not give the same bimodal molecular
weight distribution as with 9/MAO. The 1:1 mixture of
10/MAO and 11/MAO produces a mononuclear resin
with only a slightly broadened molecular weight. We
assume that in the mixture, the two originally different
active sites ‘communicate’ with each other, eventually
via the cocatalyst MAO to give an ‘averaged’ molecular
weight.
Scheme 5. Activities of the catalysts 7Á11/MAO in the homogeneous
and heterogeneous polymerization reactions of ethylene.
/
In the dinuclear catalysts, the active sites are sepa-
rated from each other and cannot undergo such a
reaction. This behavior is the major justification for
the preparation of such dual site catalysts.
Scheme 6. Molecular weights Mn of the polyethylenes obtained from
7Á/11/MAO.
3. Experimental
All experimental work was routinely carried out using
Schlenk technique. Dried and purified Ar was used as
inert gas. Toluene, pentane, diethylether and tetrahy-
drofuran were purified by distillation over Na/K alloy.
Ether was additionally distilled over LiAlH4. Methylene
chloride was dried with CaH2. Deuterated solvents such
as CHCl3-d1 and C6H6-d6 were dried over molecular
sieves (300 pm), degassed and stored under inert gas
atmosphere.
Scheme 7. Polydispersities HI of the polyethylenes obtained from 7Á
11/MAO.
/
Commercially available indene was distilled and
stored at ꢁ28 8C. Cyclopentadiene was freshly distilled
/
from the dimer. MAO (30% in C6H5CH3) was supplied
by Witco Company, Bergkamen. All the other starting
materials were commercially available and were used
without further purification.
12.2 under homo- and heterogeneous conditions. They
exceeded the values of the reference polymers of 10/
MAO (homogeneous: HIꢃ
2.6) and 11/MAO (homogeneous: HIꢃ
neous: HIꢃ2.5) by more than 100% (Scheme 7).
/
2.8; heterogeneous: HIꢃ
/
/
2.8; heteroge-
/
This width increase is especially pronounced with the
polyethylene produced from 7/MAO where two relative
maxima can be seen in the HT-GPC plot (Scheme 8).
It is well known from former results that half-
sandwich catalysts produce polyethylenes with high
3.1. NMR spectroscopy
The spectrometer Bruker ARX 250 was available for
the recording of the NMR spectra. The organometallic
compounds were prepared under inert gas atmosphere
(Ar). The spectra were recorded at 25 8C. The chemical
shifts in the 1H-NMR spectra are referred to the residual
molecular masses (ꢀ
106 g molꢁ1) [13,14]. The amido
/
silyl compounds are sterically not very demanding and
the active center of the catalysts is easily accessible for
the addition of the monomer. Polymer growth occurs
stress free, termination reaction only starts at high
molecular weight. It can be postulated that the fraction
with a maximum at 700,000 g molꢁ1 is produced by the
half-sandwich component, the fraction with a maximum
proton signal of the solvent (dꢃ
dꢃ
7.15 ppm for C6H6) and in the 13C-NMR spectra to
the solvent signal (dꢃ77.0 ppm for CHCl3-d1, dꢃ128.0
ppm for C6H6-d6). Tetramethylsilane (dꢃ0.0 ppm) was
used as external reference for 29Si-NMR spectra.
/
7.24 ppm for CHCl3,
/
/
/
/

H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259Á
/265
263
Scheme 8. Molecular weight distribution of the polyethylene produced with 7/MAO under homogeneous conditions.
˚
3.2. GCÁ
/
MS and mass spectroscopy
of the styragels were 500, 1000, 10,000 and 100,000 A in
the individual columns. A RI Waters 401 refractometer
was used for detection. The polymer samples were
dissolved in boiling 1,2,4-trichlorobenzene that was
also used as eluent. The measurements were carried
out at 150 8C. The apparatus was calibrated with an
internal polystyrene standard.
GCÁMS spectra were performed with a HP5971A
/
mass detector in combination with a HP5890 gas
chromatograph. Helium was applied as carrier gas, a
12 m J&W Fused Silica column (DB 1, film 0.25 mm was
used. The measuring program was: 3 min at 70 8C
(starting phase); 20 8C minꢁ1 (heating phase); variable
time at 210 8C (final phase).
The mass spectra were recorded with a VARIAN
3.5. Synthesis of the chlorosilane precursors
MAT CH7 instrument, GCÁMS with a VARIAN 3700
/
gas chromatograph in combination with a VARIAN
MAT 312 mass spectrometer.
3.5.1. General procedure
v-Alkenyl substituted half-sandwich ligand precursor
(10 mmol) in 10 ml of C5H12 and ca. 50 mg of
hexachloroplatinic acid hydrate were given to a Schlenk
vessel at room temperature (r.t.). Methyldichlorosilane
(1.15 g, 10 mmol) was added and the mixture was stirred
for 40 h. Then the suspension was filtered through
Na2SO4 and the solvent was removed in vacuo. Yields:
3.3. Gas chromatography
Gas chromatograms were recorded using a PerkinÁ
/
Elmer Auto System gas chromatograph with flame
ionization detector (FID) and He as carrier gas (1 ml
minꢁ1).
90Á95%.
/
Temperature program:
Starting phase: 3 min at 50 8C
Heating phase: 5 8C minꢁ1 (15 min)
Plateau phase: 310 8C (15 min)
3.6. Synthesis of the ligand precursors 1Á6
/
3.4. High temperature gel permeation chromatography
(HT-GPC)
3.6.1. General procedure
The corresponding chlorosilane presursor (5 mmol) in
100 ml of Et2O was treated with 0.88 g (10 mmol)
sodium cyclopentadienide dissolved in 10 ml of THF.
The mixture was stirred for 8 h at r.t. The suspension
was filtered through Na2SO4 and the solvent was
A Waters HT-GPC 150C instrument was applied to
measure the mass distributions of the polymer samples.
Four columns filled with cross-linked polystyrene were
used for separation of the fractions. The pore diameters
removed in vacuo. Yields: 90Á95%.
/

264
H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259Á265
/
Table 2
NMR data of compounds 1Á9
/
Compound 1H-NMR
13C-NMR
29Si-NMR
1
7.59Á
(s, 1H, al H, Ind), 2.03Á
NÃSiÃCH3), 0.78 (s, 9H, t Bu), 0.14 (s, 3H, ClÃSiÃCH3) 14.2 (CH2, bridge), 4.2 (CH3, t Bu), 0.9, ꢁ0.2 (SiÃCH3)
/
7.19 (m, 5H, ar H, Ind), 6.61 (s, 1H, ar H, Ind), 3.79 144.7, 143.1 (Cq, Ind), 131.5, 129.9, 126.6, 124.6, 122.6 33.1 (ClÃSi),
/
0.57 (m, 12H, bridge), 0.91 (s, 3H, (CH, Ind), 44.9 (CH, al, Ind), 32.1, 30.0, 22.5, 21.8, 18.2, 4.2 (IndÃSi)
2
7.50Á7.22 (m, 12H, ar H, Ind), 6.95Á6.47 (m, 8H, ar H, 144.6, 143.9 (Cq, Ind, Cp), 138.5, 132.9, 129.6, 126.2,
Cp), 3.52 (s, 2H, al H, Ind), 3.06Á3.00 (m, 2H, al H, Cp), 124.5, 122.3 (CH, ar, Ind, Cp), 47.3 (CH, al, Ind, Cp),
1.26Á
0.45 (m, 12H, bridge), 1.21 (m, 9H, t Bu), 0.02Á
ꢁ0.10 (s, 6H, SiÃCH3)
7.67Á
(s, al H, Ind), 2.76Á2.71, 1.87Á
1.23 (m, 12H, bridge), 1.33 (CH, ar, Ind), 45.7 (CH, al, Ind), 33.5, 33.1 (CH3, t Bu), 7.3 (IndÃSi)
/
/
5.5, ꢁ7.3
/
/
/
33.1, 29.9, 23.9, 22.9 (CH2, bridge), ꢁ3.2, ꢁ4.5
(SiÃCH3)
3
4
/
7.31 (m, 4H, ar H, Ind), 6.41 (s, 1H, ar H, Ind), 3.72 144.8, 143.9 (Cq, Ind), 127.8, 125.8, 124.6, 123.7, 119.5 32.8 (ClÃSi),
/
/
(s, 3H, NÃSiÃCH3), 0.84 (s, 9H, t Bu), 0.29 (s, 6H,
ClÃSiÃCH3)
31.9, 27.5, 23.6, 19.9 (CH2, bridge), 5.4, 0.3, 90.0
(SiÃCH3)
7.63Á
/
7.22 (m, 4H, ar H, Ind), 6.34 (s, 1H, ar H, Ind), 3.69 145.1, 144.6, 143.8 (Cq, Ind), 127.5, 125.6, 124.4, 123.6, 33.1 (ClÃSi),
(s, 1H, al H, Ind), 2.68Á
/
0.54 (m, 20 H, bridge, pentyl-
substituent), 0.91 (s, 3H, NÃSiÃCH3), 0.79 (s, 9H, t Bu), 27.9, 22.7, 22.4, 21.7, 16.6 (CH2, bridge, pentyl-sub-
119.5 (CH, ar, Ind), 44.9 (CH, al, Ind), 32.5, 32.1, 28.4, 5.4 (IndÃSi)
0.18 (s, 6H, ClÃSiÃCH3)
stituent), 15.8 (CH3, t Bu), 14.3 (CH3), ꢁ1.4, ꢁ1.9
(SiÃCH3)
5
6
7
7.52Á7.19 (m, 12H, ar H, Ind), 6.93Á
/
/
6.23 (m, 8H, ar H, 145.7, 144.8 (Cq, Ind, Cp), 132.9, 129.3, 125.1, 124.1,
123.2, 119.4 (CH, ar, Ind, Cp), 46.3 (CH, al, Cp), 32.5,
ꢁ7.0
Cp), 3.54 (s, 2H, al H, Ind), 3.02 (m, 2H, al H, Cp), 1.77Á
/
t
0.13 (m, 8H, bridge), 1.23 (s, 9H, Bu), ꢁ0.07Á
/
ꢁ0.26 (s, 29.9, 27.6, 23.4 (CH2, bridge), ꢁ4.6, ꢁ5.9 (SiÃCH3)
9H, SiÃCH3)
7.53Á
Cp), 3.68 (s, 2H, al H, Ind), 3.01 (m, 2H, al H, Cp), 1.34Á
0.55 (m, 20H, bridge), 1.19Á
1.17 (m, 9H, t Bu), 0.05Á
ꢁ0.13 (s, 6H, SiÃCH3)
/
7.26 (m, 12H, ar H, Ind), 6.98Á6.33 (m, 8H, ar H, 144.9, 144.3 (Cq), 137.3, 133.2, 127.8, 125.4, 124.7, 122.6 4.9, ꢁ7.5
/
/
(CH, ar, Ind, Cp), 46.4 (CH, al, Cp), 35.4, 32.6, 29.6,
/
/
24.3, 23.6, 22.8 (CH2, bridge), ꢁ4.2, ꢁ5.9 (SiÃCH3)
7.55Á6.38 (m, 14H, ar H), 2.72Á
/
/
0.46 (m, 23H, bridge,
145.8, 145.1 (Cq, Ind, Cp), 138.3, 132.9, 130.9, 129.4,
ꢁ7.5 (CpÃSi),
pentyl-substituent), 1.33 (s, 9H, t Bu), ꢁ0.03, ꢁ0.15 (s, 125.1, 123.9, 119.5 (CH, Ind, Cp), 45.9 (Cq, t Bu), 33.2, ꢁ9.5 (IndÃSi)
6H, SiÃCH3)
32.2, 29.9, 28.6, 27.6, 24.2, 24.1, 22.8, 13.4, 13.3 (CH2,
bridge, pentyl-substituent), 14.3 (CH3, t Bu), 5.8, ꢁ6.7
(SiÃCH3)
8
9
7.64Á
/
6.61 (m, 14H, ar H), 2.30Á
/
0.41 (m, 12H, bridge),
145.6, 143.9 (Cq, Ind, Cp), 131.0, 128.3, 126.4, 123.9,
121.4 (CH, Ind, Cp), 32.2, 29.7, 27.1, 26.5, 24.3, 22.9
(CH2, bridge), 4.5 (CH3, t Bu), 1.9, ꢁ6.5 (SiÃCH3)
ꢁ7.6 (CpÃSi),
ꢁ8.1 (IndÃSi)
1.41 (s, 9H, t Bu), 0.11Á
/
ꢁ0.01 (s, 6H, SiÃCH3)
7.62Á
/
6.67 (m, 14H, ar H), 2.74Á
/
0.47 (m, 8H, bridge), 1.05 145.8, 144.6 (Cq, Ind, Cp), 130.7, 128.6, 127.5, 124.7,
119.8 (CH, Ind, Cp), 33.2, 32.9 (t Bu), 30.8, 30.7, 27.4,
ꢁ7.8 (CpÃSi),
ꢁ12.9 (IndÃSi)
(s, 9H, t Bu), 0.21, 0.19, ꢁ0.01 (s, 9H, SiÃCH3)
26.2, 19.8, 14.1 (CH2, bridge), 0.3, 0.2, ꢁ6.5 (SiÃCH3)
3.7. Synthesis of the dinuclear complexes 7Á
/
9
3.8. Synthesis of the ligand precursors for the mono
nuclear complexes
3.8.1. General procedure
3.7.1. General procedure
Dichlorodimethylsilane (2.58 g, 20 mmol) in 200 ml of
Et2O and 10 mmol of sodium cyclopentadienide (or 10
mmol of fluorenyllithium) were mixed at r.t. in a
Schlenk vessel. The mixture was stirred for 8 h, then
filtered through Na2SO4 and silica gel. The solvent was
removed in vacuo. Yield: 95%.
The ligand precursor (5 mmol) was dissolved in 400
ml of Et2O and 12.5 ml (20 mmol) of n-butyllithium (1.6
M in C6H14) were added. The reaction mixture was
stirred for a minimum of 8 h at r.t.
The solution was cooled to ꢁ78 8C. Then 2.33 g (10
/
mmol) of ZrCl4 was added. The reaction mixture was
brought to r.t. within 6 h and stirred for another 6 h.
The solvent was removed in vacuo, the residue sus-
pended in CH2Cl2 and the suspension filtered through
Na2SO4. The CH2Cl2 phase was removed in vacuo, the
residue washed with C5H12 and the product crystallized
3.9. Preparation of the indenyl chlorosilane precursor
Indene (80 mmol) in 150 ml of Et2O was treated with
50 ml (80 mmol) of butyllithium (1.6 M solution in
C6H14). The solution was stirred for 4 h at r.t. Then it
from CH2Cl2/C5H12. Yields: 60Á70% (Table 2).
/
was cooled to ꢁ78 8C. Dichlorodimethyl silane (80
/

H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259Á
/265
265
mmol) was added, slowly warmed to r.t. and stirred for
12 h. The suspension was filtered through Na2SO4 and
the solvent was removed in vacuo. Yield: 95%.
suspension was stirred for 3 min. Both for homogeneous
and heterogeneous polymerizations, the catalyst suspen-
sion was diluted with 250 ml of C5H12 and injected to a 1
l Buchi laboratory autoclave thermostated at 60 8C. An
¨
ethylene pressure of 10 bar was applied to the reactor
3.10. Preparation of the indenyl ligand precursor
and the catalyst was polymerized for 30 min at 60 (9
/
The indenyl chlorosilane precursor (80 mmol) in 200
ml of CH2Cl2 was treated with 200 mmol of t-
butylamine at r.t. The mixture was stirred for 12 h,
then the solvent was removed in vacuo. The residue was
suspended in 200 ml of C5H12 and the suspension was
filtered through Na2SO4. The solvent was removed in
vacuo. Yield: 95%.
3) 8C. The obtained polymer was dried in air for at least
60 h. The polymerization results and the physical data of
the polymers are presented in Table 1.
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft
(DFG) and Phillips Petroleum Company (Bartlesville,
OK, USA) for the financial support and Witco company
(Bergkamen) for the donation of methylalumoxane.
3.11. Preparation of the mono nuclear zirconocene
complex 10
The ligand precursor (10 mmol) was dissolved in 200
ml of Et2O. Butyllithium solution (12.5 ml, 1.6 M in
C6H14; 20 mmol) was added. The mixture was stirred for
at least 8 h at r.t. Then the solution was cooled to
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/
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residue was suspended in CH2Cl2 and the suspension
was filtered through Na2SO4. The solvent of the CH2Cl2
phase was removed in vacuo, the residue was washed
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/
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The ligand precursor (20 mmol) was dissolved in 400
ml of Et2O. Butyllithium solution (12.5 ml, 1.6 M in
C6H14; 20 mmol) was added at ꢁ
was stirred for 12 h at r.t. Then the solution was cooled
to ꢁ78 8C again and 4.66 g (20 mmol) of ZrCl4 was
/
78 8C. The mixture
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Atovmyan, Organometallics 11 (1992) 3942.
/
[12] W. Abriel, G. Baum, H. Burdorf, J. Heck, Z. Naturforsch. Teil. B
46 (1991) 841.
added. The mixture was brought to r.t. within 10 h and
stirred for another 10 h. The solvent was removed in
vacuo, the residue was suspended in C5H12 and the
suspension was filtered through Na2SO4. The solvent
was removed in vacuo, the residue was suspended in
C5H12 and the LiCl containing solution was filtered. The
[13] M. Bochmann, S.J. Lancaster, M.B. Hursthouse, M. Mazid,
Organometallics 12 (1993) 4718.
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(1999) 448;
(b) G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem. Int.
Ed. Engl. 38 (1999) 428.
solution was stored for 24 h at ꢁ28 8C. The yellowish
complex precipitated. Yield: 35%.
/
[15] H.G. Alt, J. Mol. Catal. A: Chem. 174 (2001) 35.
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3.13. Polymerization reactions
¨
An amount of 20Á
complex was dissolved in 50 ml of C6H5CH3. A volume
of the solution containing 1Á2 mg of complex was taken
and activated with MAO (30% in C6H5CH3; AlÁZrꢃ
2500:1).
/
25 mg of the corresponding
Jungling, R. Mulhaupt, F. Langhauser, Organometallics 13
¨ ¨
(1994) 964.
[20] S.J. Palackal, Dissertation, Universitat Bayreuth, 1991.
¨
[21] N. Klouras, H. Kopf, Monatsh. Chem. 112 (1981) 887.
¨
/
/
/
[22] C.S. Baygur, W.R. Tikkanen, J.L. Petersen, Inorg. Chem. 24
(1985) 2539.
For heterogeneous polymerizations silica gel was
added (1 g SiO2 mmolꢁ1 (Zr)) to this solution and the
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Chem. 509 (1996) 63.