The influence of halogen substituents at the ligand framework of (α-diimine)nickel(II) catalyst precursors on their behavior in ethylene oligomerization and polymerization

Article abstract of DOI:10.1016/S1381-1169(02)00519-8

The ligand structure of (α-diimine)nickel(II) catalyst precursors has a significant influence on the behavior of these catalysts in the polymerization of ethylene. After activation with MAO, homogeneous nickel catalysts of this type are suitable to polymerize olefins to low molecular oligomers and/or more or less branched polymers. The variation of the ligand framework of the catalysts with halogen substituents in different positions shows clear dependencies between these substituents and the properties of the polymerization products. Unsaturated oligomers with an even number of carbon atoms (4-50) and all possible isomers as well as polymers up to a molecular weight of 36,000 g/mol can be obtained.

Full text of DOI:10.1016/S1381-1169(02)00519-8

Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
The influence of halogen substituents at the ligand framework
of (␣-diimine)nickel(II) catalyst precursors on their
behavior in ethylene oligomerization
and polymerization
Markus Helldörfer, Wolfgang Milius, Helmut G. Alt∗
Laboratorium für Anorganische Chemie, Universität Bayreuth,
Universitätsstraße 30, D-95440 Bayreuth, Germany
Received 1 August 2002; received in revised form 20 August 2002; accepted 23 August 2002
Abstract
The ligand structure of (␣-diimine)nickel(II) catalyst precursors has a significant influence on the behavior of these catalysts
in the polymerization of ethylene. After activation with MAO, homogeneous nickel catalysts of this type are suitable to
polymerize olefins to low molecular oligomers and/or more or less branched polymers. The variation of the ligand framework
of the catalysts with halogen substituents in different positions shows clear dependencies between these substituents and
the properties of the polymerization products. Unsaturated oligomers with an even number of carbon atoms (4–50) and all
possible isomers as well as polymers up to a molecular weight of 36,000 g/mol can be obtained.
© 2002 Elsevier Science B.V. All rights reserved.
Keywords: Halogen substituent; (␣-Diimine)nickel(II) complexes; Ethylene; Oligomer; Polymerization
1. Introduction
polymerization of olefins [29–34]. The catalytic poten-
tial of these (␣-diimine)nickel(II) complexes depends
on the structure of the catalyst precursors and is ex-
plained with the so called “chain running mechanism”
[19–28,35] (Scheme 1).
This mechanism gives reasons for the formation
of linear and branched polymers and short chain
oligomers in the ethylene polymerization with nickel
catalysts. The influence of the ligand structure on this
mechanism is mainly caused by the interaction of
substituents with the axial coordination sites of the
metal center [35–37]. Especially the steric demands
of the substituents are important (Fig. 2).
Various types of nickel catalysts for the oligomer-
ization and polymerization of olefins are known for 30
years [1–9]. Some of them found an application in the
Shell Higher Olefin Process (SHOP) [10–14]. During
the last few years, investigations were mainly focused
on (␣-diimine)nickel(II) complexes [15–18] that were
discovered by Brookhart and co-workers [19–28] as
suitable catalysts in combination with methylalumi-
noxane (MAO) (Fig. 1).
Other research groups have reported identical or
closely related catalyst systems that can be used for the
Here, we report about the behavior of (␣-diimine)
nickel(II) catalysts that bear halogen substituents at
the ligand framework when used in the polymerization
∗
Corresponding author. Fax: +49-921-552157.
E-mail address: helmut.alt@uni-bayreuth.de (H.G. Alt).
1381-1169/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S1381-1169(02)00519-8

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M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
Fig. 1. (␣-Diimine)nickel(II) catalyst precursors.
Scheme 1. Chain running mechanism [19–28,35].

M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
3
2.1.2. Synthesis of the (α-diimine)nickel(II)
complexes
The (␣-diimine)nickel dibromide complexes were
prepared according to procedures described in the lit-
erature [15,16]: the corresponding ␣-diimine ligand
is dissolved in tetrahydrofuran and reacted with an
equimolar amount of dimethoxyethane nickel dibro-
mide [38]. The synthesized complexes are summarized
in Scheme 3.
Due to the paramagnetic nature of this type of com-
plexes, it is not very informative to characterize them
by NMR spectroscopy. The mass spectrometric analy-
ses did not reveal the molecule ion in the case of com-
plexes 7a, 7b, 8a, 8c, 10a and 10b. Their fragments
deriving from the loss of bromine or iodine atoms
were observed. All mass spectrometric data with typ-
ical fragments and their intensity for the complexes
6a–10b are given in Table 4.
Fig. 2. Axial (Ax) and equatorial (Eq) coordination sites of the
metal center and their steric interactions with the ortho-sub-
stituents.
of ethylene. Relationships between the nature and the
position of substituents and the catalytic potential were
investigated.
In case of 10a, single crystals could be obtained that
were suitable for an X-ray analysis (Fig. 4).
2. Results and discussion
The complex crystallized from a solution in ace-
tone/diethylether. Therefore, one acetone molecule is
coordinated to the metal center in order to compensate
the electron deficit of the complex. The nickel atom
has the coordination number five and shows a distorted
square-planar pyramidal environment that can be de-
rived from an octahedron where one axial position is
not occupied due to the steric hindering of the two io-
dine atoms. The aryl rings of the ␣-diimine lie nearly
perpendicular to the plane formed by the metal and the
coordinated nitrogen atoms like in related structures
[20–39]. Some important bond lengths and angles are
given in Table 1.
2.1. Synthesis of the catalyst precursors
2.1.1. Synthesis of the α-diimine ligands
The ␣-diimine ligands become available by a con-
densation reaction of 2,3-butadione with the corre-
sponding aniline derivative according Scheme 2.
The synthesized ligands differ in the nature and po-
sition of the substituents at the aryl moiety. Mainly
compounds with halogen substituents were studied.
All ligands are listed in Fig. 3.
The compounds were characterized by NMR spec-
troscopy (Table 3).
Scheme 2. Synthesis of the ␣-diimine ligands.

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M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
Fig. 3. Synthesized ␣-diimine ligands.
2.2. Polymerization of ethylene with the
(α-diimine)nickel(II) complexes 6a–10b
polymerization. The toluene was removed in vacuo
and the dried catalysts were suspended in pentane and
used for a slurry polymerization reaction. The results
are summarized in Table 2.
The range of the obtained products reached from
low molecular olefinic oligomers to polymers. For
After activation with MAO (30 wt.% in toluene), the
(␣-diimine)nickel dibromide complexes synthesized
previously were tested for the homogeneous ethylene
Scheme 3. Synthesis of the (␣-diimine)nickel dibromide complexes 6a–10b.

M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
5
Fig. 4. Molecular structure of 10a.
the separation of the oligomers and the polymers, the
polymerization mixture was filtered and the remain-
ing polymer was washed with half concentrated hy-
drochloric acid in order to remove MAO. After that it
was dried in vacuo and weighed. The pentane of the
oligomer solution was removed by destillation over
a Vigreux column and the oligomers were analyzed
by GC. The classification for oligomers and polymers
was the solubility of the products in pentane. Mass
spectrometric analyses suggested a molecular weight
of ca. 1000 g/mol as the border line.
A comparison of the observed activities reveals that
complexes bearing the same substituent only in differ-
ent positions of the aryl moiety show the highest activ-
ities if the substituent is located in the ortho-position
(Fig. 5).
Only the fluorine containing complexes 7a, 7b
and 7c show a different behavior. There, 7c with a
para-fluorine substituent provides the highest activ-
ity. It can be assumed that two effects are responsible
for the activity. An ortho-substituent interacts with
the catalytic center via the axial coordination sites of
the metal. Therefore, halogens in that position seem
to stabilize the active species. Especially 10a with
two iodine atoms suits into that theory and provides
the highest activity of the catalysts studied here. The
other effect can be related to the electronic condi-
tions of the complex. If the electron density at the
metal center is comparatively low, the coordination of
the monomer is favored. In 7c with the strong elec-
tronegative fluorine substituent in para-position, this
electronic effect superimposes the ortho-effect of the
corresponding ortho-substituted complex 7a. In case
of fluorine substituents, the low steric demands of the
fluorine atom additionally do not cause an intensive
interaction of these substituents with the metal center.
Therefore, it can be concluded that the activity of
(␣-diimine)nickel(II) catalysts of this type is a corre-
lation between electronic and steric effects caused by
the substituents at the aryl moiety of the ligand.
In this context, the formation of oligomers and
polymers also can be explained. The obtained
oligomer/polymer ratios are shown in Fig. 6.
According to the “chain running mechanism” the
formation of oligomers depends on the number of
chain transfers. After a coordinated higher olefin has
been formed, it has to be replaced by an ethylene
molecule. For this replacement, the axial coordination
sites of the metal are decisive. If they are sterically
hindered by a substituent, chain transfer is suppressed
and polymer is produced. Therefore, the unsubsti-
tuted complex 6a is only able to dimerize ethylene
to butene. Higher olefins can only be detected in
slight traces. The fluorine substituted complexes 7a,
7b and 7c and the complexes with substituents in the
meta- or para-position (6c, 8b, 8c, 9b, 10b) produce

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M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
Table 1
low molecular olefins and ethylene but direct polymer-
ization products that show a higher molecular weight
than 1000 g/mol and are insoluble in pentane.
Selected bond lengths and angles of the molecular structure of 10a
Bond lentghs (Å)
Ni–N(1)
Ni–O
2.061 (5)
2.076 (4)
2.081 (5)
2.4137 (10)
2.4415 (10)
1.277 (7)
1.275 (7)
1.496 (8)
Based on the GC analyses of the oligomer mixtures,
it is possible to calculate the Schulz–Flory-constant α
[40–43] for the distribution of the oligomer fractions.
For this calculation, the area integrals of the oligomer
fractions with a carbon number from 10 to 30 were
used. Due to the formation of both isomers of the
olefins and polymers, the values of α imply a statistical
error especially in the cases of 6b and 9a were α ≥ 1.
All values of α are included in Table 2.
Beside activity and oligomer/polymer ratio, also the
selectivity for the formation of ␣-olefins depends on
the nature and the position of the substituents at the
aryl moiety of the ligands. For a quantitative discus-
sion, the selectivity towards 1-octene was examined.
The results are summarized in Fig. 9.
Whereas in the case of the fluorine substituted com-
plexes 7a, 7b and 7c, no influence of the position of the
fluorine atoms on the oligomer/polymer ratio could be
observed. A view on the selectivity to ␣-olefins reveals
certain dependencies: The para-substituted complex
7c shows almost no selectivity. In turn from meta- (7b)
to ortho-substitution (7a), the selectivity for 1-octene
is rising nearly linear. This trend can also be observed
for 6b and 6c. For the other catalyst precursors, no
such relations can be determined because they produce
too little octene or only polymers.
Ni–N(2)
Ni–Br(2)
Ni–Br(1)
N(1)–C(1)
N(2)–C(2)
C(1)–C(2)
Bond angles (◦)
N(1)–Ni–O
N(1)–Ni–N(2)
O–Ni–N(2)
N(1)–Ni–Br(2)
O–Ni–Br(2)
N(2)–Ni–Br(2)
N(1)–Ni–Br(1)
O–Ni–Br(1)
N(2)–Ni–Br(1)
Br(2)–Ni–Br(1)
C(1)–N(1)–C(5)
C(1)–N(1)–Ni
C(5)–N(1)–Ni
C(2)–N(2)–C(11)
C(2)–N(2)–Ni
C(11)–N(2)–Ni
N(1)–C(1)–C(2)
N(1)–C(1)–C(4)
C(2)–C(1)–C(4)
N(2)–C(2)–C(1)
N(2)–C(2)–C(3)
C(1)–C(2)–C(3)
154.98 (19)
77.56 (19)
85.25 (19)
97.55 (14)
92.24 (14)
159.57 (14)
95.79 (13)
103.07 (13)
92.55 (14)
107.75 (4)
118.7 (5)
116.0 (4)
125.3 (4)
120.7 (5)
114.6 (4)
124.0 (4)
115.0 (5)
125.8 (5)
119.1 (5)
115.6 (5)
125.7 (6)
118.7 (5)
An explanation for this behavior is rather difficult.
According to the “chain running mechanism”, the
formation of ␣-olefins should be favored. A high se-
lectivity for these products, however, is only observed
under comparatively high polymerization pressures
[24]. Under these conditions, the monomer concen-
tration is sufficient to replace the formed olefin in
a chain transfer reaction before a double bond iso-
merization takes place. Therefore, complexes with
an easily accessible catalytic center should pro-
duce mainly ␣-olefins. But in the case of para- and
meta-substituted catalysts, the selectivity is very low.
Only ortho-substituted catalysts are able to oligomer-
ize ethylene to ␣-olefins with good selectivity. It can
be assumed that the isomerization of the olefins pro-
ceeds via a mechanism that includes the axial coordi-
nation sites of the metal center. If these coordination
sites are sterically hindered by an ortho-substitutent
of the ligand, the isomerization step is suppressed.
oligomers with an even carbon number up to ca. 50
carbon atoms. The GC-plot of the oligomer mixture
produced with 7c/MAO is shown in Fig. 7.
The catalysts bearing a substituent in the ortho-
position of the aryl moiety produce polymers to a cer-
tain extent. The amount of polymer is closely related
to the bulk of the substituent. Therefore, 10a with the
most bulky iodine substituents only forms a polymer
with an average molecular weight of 36,000 g/mol.
The oligomer mixtures obtained with 6b, 8a and 9a
are vicous oils or waxes. Compared to the oligomers
produced with the other catalysts, olefins with higher
carbon numbers are dominating. This can easily be
seen in the GC-plot of the oligomer mixture produced
with 6b/MAO (Fig. 8).
Therefore, it can be assumed that the produced poly-
mers are not a consequence of a copolymerization of

M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
7
Table 2
Results of the homogeneous ethlyene polymerization for the (␣-diimine)nickel(II) complexes 6a–10b activated with MAOa
No.
Activityb
TOFc
Polymer share (wt.%)
αd
1-Octenee
Mw (polymer share) (g/mol)
Df
6a
6b
6c
7a
7b
7c
8a
8b
8c
822
869
464
939
499
1843
1702
1321
505
733
587
30,825
32,588
17,400
35,213
18,713
69,113
63,825
49,538
18,938
27,488
22,013
149,663
39,600
0
41
–
0
–
–
3.0
1.00
0.64
0.65
0.66
0.68
n.d.
0.72
0.65
1.22
0.54
n. d.
0.67
37.6
30.8
47.7
26.4
7.6
n.d.
12.8
25.8
n.d.
34.5
–
69,000
n.d.g
n.d.
n.d.
n.d.
6,700
n.d.
n.d.
18,460
n.d.
35,870
n.d.
<1
<1
0.7
<1
22
1.2
3.1
27
n.d.
n.d.
n.d.
n.d.
1.3
n.d.
n.d.
1.6
9a
9b
10a
10b
1.1
100
4.2
n.d.
23.6
n.d.
3991
1056
49.3
a Polymerization conditions: activation with 30 wt.% methylaluminoxane in toluene (Al:Ni = 1000:1; polymerization in 250 ml pentane,
60 ◦C, 1 l autoclave, 10 bar ethylene pressure, 60 min).
b The activities [g (product)/mmol (Ni) h] were calculated from the total consumption of ethylene (1.0 l ethylene = 1.2 g product).
c TOF [mol(C2H4)/mol(cat.) h]: turn over frequency.
rate of propagation
k
d α =
=
= Schulz–Flory-constant.
B
(k +k
B
)
C
rate of propagation+rate of chain transfer
e 1-Octene share (mol%) of all octene isomers.
f D: polydispersity Mw/Mn of the polymer share.
g n.d.: not determined.
Fig. 5. Comparison of the observed activities of the catalyst precursors 6a–10b.

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M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
Fig. 6. Oligomer/polymer ratio obtained with the catalyst precursors 6a–10b.
Fig. 7. Oligomer mixture obtained with 7c/MAO.

M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
9
Fig. 8. Oligomer mixture obtained with 6b/MAO.
Fig. 9. Selectivity for the formation of 1-octene in the case of 6b, 6c, 7a, 7b, 7c, 8b, 8c, 10b.

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M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
Over all, the selectivity of the examined catalysts
to ␣-olefins is in all cases lower than 50%.
tion was observed by GC. After 12–24 h, the reac-
tion mixture was cooled to room temperature and fil-
tered over silica. After removing the solvent in vacuo,
the product was precipitated with cold methanol. For
purification, the products were recrystallized from a
methanol/ethanol mixture (3:1). The ligands were ob-
tained as yellow crystals.
Yields: 1a, 80%; 1b, 65%; 1c, 70%; 2a, 45%; 2b,
45%; 2c, 65%; 3a, 75%; 3b, 25%; 3c, 60%; 4a, 30%;
4b, 55%; 5a, 70%; 5b, 80%.
3. Experimental
NMR spectroscopic investigations were performed
with a Bruker ARX 250 instrument. All organometal-
lic samples were prepared under argon and measured
at 25 ◦C. CDCl3 served as solvent. The chemical shifts
(δ) in the 1H NMR spectra are referenced to the resi-
dual proton signal of the solvent (δ = 7.24 ppm for
chloroform) and in 13C NMR spectra to the solvent
signal (δ = 77.0 ppm for chloroform-d1).
All compounds were characterized by NMR spec-
troscopy (Table 3).
3.2. General synthesis procedure for the
(α-diimine)nickel dibromide complexes 6a–10b
MS spectra were recorded with a VARIAN MAT
CH7 mass spectrometer (direct inlet system, elec-
tron impact ionization 70 eV). In addition, a Hewlett-
Packard 5917A mass spectrometer was routinely
used to record MS spectra and in combination with a
Hewlett-Packard Series II 5890 gas chromatograph to
record GC/MS spectra.
A concentration of 5 mmol of the respective
␣-diimine ligand were dissolved in 150 ml THF and
5 mmol of dimethoxyethane nickel dibromide were
added under argon atmosphere. The mixture was
stirred for 8 h at room temperature. For purification,
the volume of the solvent was reduced in vacuo and the
complexes were precipitated by adding pentane. After
washing several times with pentane until the solvent
stayed colorless, the products were dried in vacuo.
The complexes were obtained as crystalline powders.
Yields: 6a, 95%; 6b, 90%; 6c, 90%; 7a, 85%; 7b,
90%; 7c, 90%; 8a, 85%; 8b, 80%; 8c, 85%; 9a, 80%;
9b, 90%; 10a, 85%; 10b, 90%.
Molecular weight determinations of the polyethy-
lene samples were performed using a Millipore Wa-
ters 150 C HT-GPC with refractometric detection (RI
Waters 401). The polymer samples were dissolved in
1,2,4-trichlorobenzene (flow rate 1 ml/min) and mea-
sured at 150 ◦C.
Gas chromatograms were recorded using a Perkin-
Elmer Auto System gas chromatograph with flame
ionization detector (FID) and helium as carrier gas
(1 ml/min).
The complexes were identified by mass spectrome-
try (Table 4).
The synthesized complexes did not show a melt-
ing point under inert atmosphere but decomposition at
higher temperatures.
The temperature program is as follows.
Starting phase: 3 min at 50 ◦C.
Heating phase: 5 ◦C/min (15 min).
Plateau phase: 310 ◦C (15 min).
Decomposition temperatures: 6a, 205 ◦C; 6b,
200 ◦C; 6c, 205 ◦C; 7a, 210 ◦C; 7b, 200 ◦C; 7c,
210 ◦C; 8a, 220 ◦C; 8b, 210 ◦C; 8c, 210 ◦C; 9a,
240 ◦C; 9b, 230 ◦C; 10a, 220 ◦C; 10b, 230 ◦C.
The purity of complexes 7c and 9b was tested by mi-
croanalyses: 7c, C = 41.36% (Ccalc. = 39.16%), H =
Methylaluminoxane was supplied by Witco GmbH,
Bergkamen, as 30% solution in toluene (average
molecular weight 1100 g/mol, aluminum content:
13.1, 3.5% as trimethylaluminum).
4.62% (Hcalc. = 2.88%); 9b, C = 29.55 (Ccalc.
31.37), H = 2.75 (Hcalc. = 2.30).
=
3.1. General synthesis procedure for the α-diimine
ligands 1a–5b
To a solution of 40 mmol of the respective aniline
derivative in dichloromethane, 15 mmol of the cor-
responding diketo compound and a catalytic amount
of p-toluene sulfonic acid were added. The mixture
was heated under reflux. The progress of the reac-
3.3. General procedure for the activation of the
(α-diimine)nickel(II) complexes
An amount of 5–10 mg of the complex were sus-
pended in toluene and activated with the correspond-

M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
11
Table 3
NMR data for compounds 1a–5b
No.
1H NMRa
13C NMRb
1a
1b
7.29 (m, 4H), 7.06 (m, 2H), 6.85 (m, 4H), 2.19 (s, 6H)
Cq : 168.3, 150.9; CH: 129.0, 123.8, 118.7; CH3: 15.4
Cq : 167.7, 149.5, 126.7; CH: 130.4, 126.4, 123.9,
117.6; CH3: 17.8, 15.6
3
4
7.12 (m, 8H), 6.93 (dt, 2H, JHH = 7.5 Hz, JHH = 1.2 Hz),
3
3
6.55 (dd, 2H, JHH = 7.8 Hz, JHH = 0.9 Hz), 2.03 (s, 6H)
1c
2a
7.16 (m, 4H), 6.68 (m, 4H), 2.34 (s, 6H), 2.15 (s, 6H)
Cq : 168.3, 148.3, 133.2; CH: 129.5, 118.8; CH3: 20.8,
15.3
1
6.85 (m, 8H), 2.24 (s, 6H)
Cq : 170.2, 151.3 (d, JCF = 239 Hz), 128.5; CH: 124.8
3
(d, JCF = 7 Hz), 124.0, 121.2, 115.7 (d,
2JCF = 20 Hz); CH3: 15.4
1
2b
7.20 (m, 2H), 6.70 (m, 2H), 6.42 (m, 4H), 2.02 (s, 6H)
7.05 (m, 4H), 6.73 (m, 4H), 2.13 (s, 6H)
Cq : 168.7, 163.3 (d, JCF = 247 Hz), 152.5 (d,
3
3JCF = 9 Hz); CH: 130.3 (d, JCF = 9 Hz), 114.3, 110.5
2
2
(d, JCF = 21 Hz), 106.1 (d, JCF = 23 Hz); CH3: 15.4
1
2c
3a
Cq : 168.7, 159.7 (d, JCF = 242 Hz), 146.7; CH: 120.3
3
2
(d, JCF = 8 Hz), 115.7 (d, JCF = 23 Hz); CH3: 15.4
Cq : 168.5, 144.1, 122.3; CH: 129.7, 127.1, 124.6,
119.5; CH3: 15.9
3
4
7.46 (dd, 2H, JHH = 8.0 Hz, JHH = 1.2 Hz), 7.29 (dt, 2H,
3JHH = 7.5 Hz, JHH = 1.2 Hz), 7.09 (dt, 2H,
4
3JHH = 9.3 Hz, JHH = 1.5 Hz), 6.84 (dd, 2H,
4
3JHH = 9.2 Hz, JHH = 1.4 Hz), 2.19 (s, 6H)
4
3b
7.25 (m, 2H), 6.74 (m, 2H), 6.35 (m, 4H), 2.09 (s, 6H)
Cq : 168.5, 146.1, 121.3; CH: 126.7, 125.1, 124.6,
115.5; CH3: 15.5
3c
4a
7.31 (m, 4H), 6.70 (m, 4H), 2.11 (s, 6H)
Cq : 168.7, 149.2, 129.3, CH: 129.1, 120.2; CH3: 15.4
Cq : 169.5, 149.1, 113.1; CH: 132.9, 128.0, 125.1,
119.4; CH3: 16.2
3
4
7.63 (dd, 2H, JHH = 8.0 Hz, JHH = 1.3 Hz), 7.33 (dt, 2H,
3JHH = 7.6 Hz, JHH = 1.3 Hz), 6.97 (dt, 2H,
4
4
3JHH = 7.9 Hz, JHH = 1.6 Hz), 6.80 (dd, 2H,
4
3JHH = 7.9 Hz, JHH = 1.6 Hz), 2.16 (s, 6H)
4b
5a
7.42 (m, 4H), 6.61 (m, 4H), 2.11 (s, 6H)
Cq : 169.4, 149.8, 114.3; CH: 130.2, 122.5; CH3: 15.3
Cq : 169.2, 151.9, 88.9; CH: 139.0, 128.9, 125.4, 118.3;
CH3: 16.2
3
4
7.86 (dd, 2H, JHH = 7.9 Hz, JHH = 1.3 Hz), 7.34
3
4
(dt, 2H, JHH = 7.6 Hz, JHH = 1.3 Hz), 6.83 (dt, 2H,
3JHH = 7.8 Hz, JHH = 1.6 Hz), 6.74 (dd, 2H,
4
3JHH = 7.8 Hz, JHH = 1.4 Hz), 2.16 (s, 6H)
4
5b
7.65 (m, 4H), 6.53 (m, 4H), 2.10 (s, 6H)
Cq : 168.5, 150.4, 87.5; CH: 138.0, 120.9; CH3: 15.4
a 250.13 MHz, 25 ◦C, in chloroform-d1, δ [ppm] rel. chloroform (7.24).
b 62.9 MHz, 25 ◦C, in chloroform-d1, δ [ppm] rel. chloroform-d1 (77.0).
Table 4
Mass spectrometric data of complexes 6a–10b
No.
Fragment (m/z) (intensity (%))
6a
6b
6c
7a
7b
7c
8a
8b
8c
M+ = 455 (2), 375 (10), 236 (100), 118 (100), 77 (85)
M+ = 481 (4), 402 (8), 264 (42), 249 (100), 132 (100), 91 (100)
M+ = 481 (1), 402 (7), 264 (38), 249 (23), 131 (100), 91 (55)
M+(–Br) = 411 (3), 321 (10), 272 (90), 253 (30), 135 (100), 95 (90)
M+(–Br) = 411 (1), 321 (5), 272 (80), 253 (4), 135 (100), 95 (95), 75 (48)
M+ = 491 (2), 410 (5), 272 (45), 161 (60), 156 (35), 135 (100), 111 (95), 95 (70)
M+(–Br) = 445 (1), 409 (2), 374 (3), 315 (8), 304 (2), 269 (85), 152 (100), 111 (40)
M+ = 525 (4), 443 (5), 394 (6), 350 (30), 304 (100), 269 (25), 198 (23), 152 (100), 111 (95), 75 (20)
M+(–Br) = 445 (2), 350 (5), 304 (25), 269 (8), 152 (100), 111 (20)
9a
M+ = 612 (4), 533 (4), 394 (5), 312 (90), 233 (15), 196 (100), 154 (28)
M+ = 612 (3), 532 (10), 451 (4), 394 (90), 312 (80), 195 (100), 154 (95), 117 (75), 84 (80), 76 (85)
M+(–Br, –I) = 503 (4), 429 (8), 361 (100), 244 (95), 203 (45), 76 (55)
M+(–Br) = 626 (2), 488 (20), 442 (15), 361 (10), 244 (100), 203 (15), 117 (15)
9b
10a
10b

12
M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 197 (2003) 1–13
ing amount of MAO (Al:Ni = 1000:1). The solvent
was removed in vacuo and the activated catalyst was
suspended in 50 ml n-pentane. The catalyst suspen-
sion was used for ethylene polymerization within
30 min.
Acknowledgements
We thank Chevron Phillips Chemical Co., USA,
for the financial support and Dr. C. Erdelen for the
HT-GPC measurements.
3.4. Homogeneous ethylene polymerization
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