(α-diimine)nickel(II) complexes containing chloro substituted ligands as catalyst precursors for the oligomerization and polymerization of ethylene

Article abstract of DOI:10.1016/S1381-1169(02)00468-5

(α-Diimine)nickel(II) dibromide complexes and their derivatives can be used for the polymerization and oligomerization of ethylene after activation with methyl-aluminoxane (MAO). The activities of these catalysts and the properties of the obtained polyethylenes depend on the structure of the used catalyst precursors. Therefore a variety of (α-diimine)nickel(II) dibromide complexes with chlorine and methyl substituents on the ligands and various substituents on the ligand backbone were studied as catalysts for the homogeneous polymerization of ethylene. The range of the polymerization products reaches from oligomers to polymers of low molecular weights.

Full text of DOI:10.1016/S1381-1169(02)00468-5

Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
(␣-Diimine)nickel(II) complexes containing chloro substituted
ligands as catalyst precursors for the oligomerization and
polymerization of ethylene
Markus Helldörfer, Judith Backhaus, Wolfgang Milius, Helmut G. Alt∗
Laboratorium für Anorganische Chemie, Universität Bayreuth, Universitätsstraße 30, NW I, D-95440 Bayreuth, Germany
Received 15 July 2002; accepted 7 August 2002
Abstract
(␣-Diimine)nickel(II) dibromide complexes and their derivatives can be used for the polymerization and oligomerization of
ethylene after activation with methyl-aluminoxane (MAO). The activities of these catalysts and the properties of the obtained
polyethylenes depend on the structure of the used catalyst precursors. Therefore a variety of (␣-diimine)nickel(II) dibromide
complexes with chlorine and methyl substituents on the ligands and various substituents on the ligand backbone were studied as
catalysts for the homogeneous polymerization of ethylene. The range of the polymerization products reaches from oligomers
to polymers of low molecular weights.
© 2002 Elsevier Science B.V. All rights reserved.
Keywords: ␣-Diimine ligands; Nickel; Catalysis; Polymerization; Oligomers; Ethylene
1. Introduction
the ligand structure on the polymerization products.
Here, we report about (␣-diimine)nickel(II) dibromide
complexes that posses a methyl and a chloro sub-
stituent in the ligand framework. These compounds
were activated with MAO and tested as catalysts for
the polymerization of ethylene. The influence of the
functional groups on the arene moiety and the varia-
tions of the ligand backbones on the polymerization
behaviors of these catalysts were analyzed.
Homogeneous nickel catalysts for the oligomeriza-
tion and polymerization of ethylene are available since
the 1970s [1–11]. (␣-Diimine)nickel(II) complexes
have been known since 1975 [12–15]. Brookhart and
others discovered them as catalyst precursors for the
polymerization of olefins [16–25] (Fig. 1). These
catalysts with a late transition metal are suitable to
polymerize ethylene to give short chain oligomers
and highly branched or linear polymers [26–31].
These investigations are mainly focused on cata-
lyst precursors with more or less bulky aliphatic or
aromatic ortho-substituents at the arene moiety of the
␣-diimine ligand in order to study the influence of
2. Results and discussion
2.1. Synthesis of the catalyst precursors
2.1.1. Synthesis of the α-diimine ligands
The ␣-diimine ligands were synthesized by con-
densation of two equivalents of a substituted aniline
∗
Corresponding author. Tel.: +49-921-552555;
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)00468-5

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M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
Fig. 1. (␣-Diimine)nickel(II) catalyst precursors.
derivative with one equivalent of a 1,2-diketone com-
pound according to Scheme 1.
13C NMR spectroscopy. The corresponding data are
summarized in third table.
In case of 1a, 1b, 1c dichloromethane was used as
solvent due to the boiling point of the 2,3-butadione
(88 ◦C). For the synthesis of the other ligands toluene
was used. The para-toluene sulfonic acid was added
as catalyst and the aniline derivatives were applied in
a small excess. The end of the reaction was recognized
by GC. All compounds were characterized by 1H and
2.1.2. Synthesis of the (α-diimine)nickel(II)
dibromide complexes
(␣-Diimine)nickel(II) complexes become available
by the reaction of dimethoxyethane nickel dibromide
[32] with the corresponding ␣-diimine ligand [12,13].
Therefore the ␣-diimine compound is dissolved in
Scheme 1. Synthesis of the ␣-diimine ligands.

M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
61
Scheme 2. Synthesis of (␣-diimine)nickel(II) dibromide complexes.
tetrahydrofuran and reacted with an equimolar amount
of the nickel complex (Scheme 2).
The reaction starts immediately and can be observed
by a color change of the reaction mixture from yellow
to dark red. The yields of the complexes are almost
quantitative. All synthesized (␣-diimine)nickel(II) di-
bromide 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 revealed the molecule ion in the case of complexes
5a and 6b. In all the other cases fragments with the
loss of bromine and chlorine atoms or a methyl group
were observed. The mass spectrometric data with typ-
ical fragments and their intensities are given for the
complexes 5a–8d in fourth table.
Complex 5b gave single crystals that were suitable
for an X-ray analysis (Fig. 2). The crystal structure of
5b shows a trinuclear cationic complex, each nickel
atom has the coordination number six. The three nickel
atoms together with three bromine atoms form a planar
six membered ring. Above and below the ring plane is
a bromine atom that bridges all three nickel atoms. The
remaining bromine atom is located as counteranion in
the lattice. The two nitrogen atoms of the ␣-diimine
ligand complete the distorted octahedral coordination
of the nickel atoms. The aryl rings of the ␣-diimine
lie nearly perpendicular to the plane formed by the
metal and the coordinated nitrogen atoms like in re-
lated structures [17,26,33]. The crystals show the sym-
metric trigonal space group P-3. The quality of the
crystals allowed only a R-value of 10.45%. Some im-
portant bond lengths and angles are given in Table 1.
Although 5b is trinuclear in the solid state, the para-
magnetism of the dissolved complex is indicative for
a monomeric structure in solution.
Fig. 2. Molecular structure of 5b.
2.2. Polymerization of ethylene with the
(α-diimine)nickel(II) complexes 5a–8d
The (␣-diimine)nickel dibromide complexes syn-
thesized above were tested for homogeneous ethylene
polymerization. After activation with MAO (30 wt.%
Table 1
Selected bond lengths and angles of the molecular structure of 5b
Bond lengths (Å)
Ni–N(1)
Ni–N(2)
Ni–Br(1)
Ni–Br(2)
2.058(15) Ni–Br(3)
2.071(14) N(1)–C(1)
2.595(3)
1.27(2)
1.25(2)
1.54(3)
2.546(3)
2.551(3)
N(2)–C(2)
C(1)–C(2)
Bond angles (◦)
N(1)–Ni–N(2)
N(1)–Ni–Br(1)
N(2)–Ni–Br(1) 175.4(4)
N(1)–Ni–Br(2) 174.8(5)
77.9(6)
97.9(5)
Br(3)–Ni–Br(3)1 164.36(11)
Ni1–Br(1)–Ni
Ni1–Br(2)–Ni
Ni–Br(3)–Ni(2)
77.98(10)
77.79(10)
75.64(11)
N(2)–Ni–Br(2)
Br(1)–Ni–Br(2)
N(1)–Ni–Br(3)
N(2)–Ni–Br(3)
Br(1)–NI–Br(3)
Br(2)–Ni–Br(3)
97.2(4)
86.94(10)
97.7(4)
97.6(4)
84.67(8)
84.71(8)
C(1)–N(1)–C(12) 121.1(15)
C(1)–N(1)–Ni
C(12)–N(1)–Ni
C(2)–N(2)–C(5)
C(2)–N(2)–Ni
C(5)–N(2)–Ni
116.8(12)
122.1(11)
121.0(15)
115.6(13)
123.3(11)

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M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
Scheme 3. Synthesized (␣-diimine)nickel(II) complexes.
in toluene), the solvent was removed in vacuo. The
dried catalysts were suspended in pentane and used for
slurry polymerization reactions. The results are sum-
marized in Table 2.
In all cases a mixture of oligomers and polymers
was obtained. In order to analyze the products, the
polymerization mixture was filtered to separate the
oligomers and the polymers. The polymer was washed
with half concentrated hydrochloric acid in order to
remove MAO and then it was dried in vacuo. The
pentane of the oligomeric solution was destilled over
a Vigreux column. The remaining oligomers were an-
alyzed by GC. The classification for oligomers and
polymers was the solubility of the products in pen-
tane. Mass spectrometric analyses suggested a molec-
ular weight of ca. 1000 g mol−1 as the border line.
A comparison of the observed activities reveals that
chloro substituents in the para-position (5b, 6b) or
the ortho-position (7c, 8d) at the aryl groups of the
␣-diimine ligand lead to the highest activities (Fig. 3).

M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
63
Table 2
Results of the homogeneous ethlyene polymerization for the ␣-(diimine)nickel(II) complexes 5a–8d activated with MAO
No.
Activitya
(g(product) mmol−1 (Ni) h)
TOFb
Polymer share
(wt.%)
Mw (polymer share)
(g mol−1
)
Dc
(mol(C2H4) mol−1(Kat.) h)
5a
5b
5c
6a
6b
6c
7a
7b
7c
8a
8b
8c
8d
1,350
2,230
1,467
1,021
1,497
951
1,162
346
2,636
270
50,625
83,625
55,013
38,288
56,138
35,663
43,575
12,975
98,850
10,125
8,813
75
24.7
90
59
49.5
54
66.7
95
83.3
74.1
70
5,469
6,900
6,170
n.d.d
n.d.
n.d.
12,240
5,600
1,475
6,110
5,920
n.d.
4.5
2.7
3.7
n.d.
n.d.
n.d.
7.9
10.5
5.6
26.8
12.3
n.d.
8.6
235
270
2,870
10,125
107,625
95.2
62.1
1,520
Polymerization conditions: activation with 30 wt.% MAO in toluene (Al/Ni = 1000/1; polymerization in 250 ml pentane, 60 ◦C, 1 l
autoclave, 10 bar ethylene pressure, 60 min).
a The activities were calculated from the total consumption of ethylene (1.0 l ethylene = 1.2 g product).
b Turn over frequency.
c Polydispersity Mw/Mn of the polymer share.
d Not determined.
There is also a trend that bulkier substituents at the
ligand backbone lead to a decrease of the activities.
Therefore, the activity of 5b (2230 g(product) mmol−1
(Ni) h) with two methyl groups at the ligand back-
bone is nearly 10 times higher then the activity of
8b (235 g(product) mmol−1 (Ni) h) bearing two phenyl
groups.
The relations for the polymer share determined for
the different catalysts show also some clear trends
(Fig. 4). A comparison of the catalysts with the same
Fig. 3. Comparison of the observed activities of the catalyst precursors 5a–8d.

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M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
Fig. 4. Comparison of the polymer share obtained with the catalyst precursors 5a–8d.
substituents at the ligand backbone obtained from 5a,
5b and 5c shows that 5b with a chloro substituent in
the para-position produces the lowest polymer share.
Similar effects were also observed for the catalysts
derived from 6a, 6b, 6c, 8a, 8b and 8c.
It is obvious that there is an increase of the polymer
share from the catalysts with two methyl groups at the
ligand backbone to those with two ethyl groups and
further a little decrease of the polymer share for the
catalysts with two phenyl groups at the ligand back-
bone.
The GC analyses of the oligomer mixtures show
the formation of almost all isomers that are possible
for olefins with an even carbon number (Fig. 5). All
oligomer mixtures were viscous oils or waxes. There-
fore, it can be assumed that the produced polymers
are not a consequence of a copolymerization of low
molecular olefins and ethylene, but direct polymer-
ization products that show a higher molecular weight
than 1000 g mol−1 and are insoluble in pentane.
Most of these results can be explained with the
so called “chain running mechanism” suggested by
Brookhart and others [16–26,34] (Scheme 4).
With this mechanism the formation of oligomers
and polymers can be explained. An important role
whether polymer or short chain oligomers are formed
plays the ortho-position at the aryl rings of the
␣-diimine ligand. Deng et al. [35,36] proved this
with calculations for the transition states of the chain
propagation and the chain transfer reaction. The
ortho-substituents have a considerable influence on
the monomer addition to the catalytic center and the
dissociation of the formed polymer from the metal
due to their interaction with the axial coordination
sites of the metal center (Fig. 6).
Considering this background, the comparatively
high activities of 5b and 6b can be related to the
low influence of the para-chloro substituent on the
catalytic center. For these catalysts the coordination
of the monomer and the dissociation of the formed
oligomers is privileged. Therefore, high activities and
a low polymer share are observed. On the other hand,
a chloro substituent in the ortho-position like in the
case of 7c and 8d seems to stabilize the catalytic
species better than a methyl group in that position. As
a consequence for these catalysts, very high activities
are observed, whereas the polymer share is already
bigger than 60 wt.%. The decrease of activities and
the increase of the polymer share with bulkier sub-
stituents at the ligand backbone results from to the

M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
65
Fig. 5. GC plot of the oligomers obtained with complex 6c/MAO.
interaction between the backbone and the aryl groups
of the ligand. Bulkier groups at the backbone reduce
the free rotation of the aryl rings. Therefore, the axial
coordination sites of the metal center are sterically
more hindered.
In contradiction to the results of Killian et al. [21],
we found the formation of isomers of the short chain
oligomers. Brookhart et al. reported a high selectiv-
ity to the formation of ␣-olefins. This observation
can be related to the polymerization conditions. Here
an ethylene pressure of 10 bar was used whereas
Brookhart carried out his polymerization reactions at
comparatively high pressures (56 atm) favoring the
ethylene insertion process. The considerable isomer-
ization and the production of both oligomers and
polymers made it almost impossible to calculate a
Schulz–Flory distribution for the obtained oligomer
mixtures.
3. Experimental
Fig. 6. Axial (Ax) and equatorial (Eq) coordination sites of
the metal center and their steric interactions with the ortho-
substituents.
NMR spectroscopic investigations were performed
with a Bruker ARX 250 instrument. All organometal-

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M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
Scheme 4. Chain running mechanism [16–25,34].
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 resid-
ual 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).
Molecular weight determinations of the polyethy-
lene samples were performed using a Millipore Wa-
ters 150C HT-GPC with refractometric detection (RI
Waters 401). The polymer samples were dissolved
in 1,2,4-trichlorobenzene (flow rate 1 ml min−1) and
measured at 150 ◦C.
MS spectra were recorded with a Varian MAT CH7
mass spectrometer (direct inlet system, electron im-
pact 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.
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−1).
Temperature program include the following:
• starting phase: 3 min at 50 ◦C;

M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
67
• heating phase: 5 ◦C min−1 (15 min); and
3.3. General synthesis procedure for the
(α-diimin)nickel dibromide complexes 5a–8d
• plateau phase: 310 ◦C (15 min).
Methyl-aluminoxane (MAO) was supplied by Witco
GmbH, Bergkamen, as 30% solution in toluene (av-
erage molecular weight 1100 g mol−1, aluminum con-
tent: 13.1%, 3.5% as trimethylaluminum).
A 5 mmol of the respective ␣-diimine ligand
were dissolved in 150 ml THF. Then 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 com-
plexes were obtained as crystalline powders. Yields:
5a, 95%; 5b, 95%; 5c, 90%; 6a, 95%; 6b, 90%; 6c,
90%; 7a, 90%; 7b, 90%; 7c, 85%; 8a, 85%; 8b, 85%;
8c, 85%; 8d, 90%. The complexes were identified by
mass spectrometry (Table 4).
The synthesized complexes did not show a melt-
ing point under inert atmosphere but decomposition
at higher temperatures. Decomposition temperatures:
5a, 230 ◦C; 5b, 240 ◦C; 5c, 235 ◦C; 6a, 230 ◦C;
6b, 250 ◦C; 6c, 240 ◦C; 7a, 235 ◦C; 7b, 230 ◦C;
7c, 240 ◦C; 8a, 220 ◦C; 8b, 225 ◦C; 8c, 240 ◦C; 8d,
210 ◦C.
3.1. General synthesis procedure for the α-diimine
ligands 1a–1c
To a solution of 40 mmol of the respective ani-
line derivative in dichloromethane, 15 mmol of the
corresponding diketo compound and a catalytic
amount of p-toluene sulfonic acid were added. The
mixture was heated under reflux. The progress of
the reaction was observed by GC. After 12–24 h
the reaction mixture was cooled to room temper-
ature and filtered 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 obtained as yellow crys-
tals. Yields: 1a, 75%; 1b, 80%; 1c, 80%. All com-
pounds were characterized by NMR spectroscopy
(Table 3).
The purity of complexes 5a, 6a and 6b was tested by
microanalyses: 5a, C = 39.92% (Ccalc. = 39.18%),
H = 4.00% (Hcalc. = 3.29%); 6a, C = 38.93 (Ccalc.
=
3.2. General synthesis procedure for the α-diimine
ligands 2a–4d
40.33), H = 3.86 (Hcalc. = 3.56); 6b, C = 40.54
(Ccalc. = 40.33), H = 4.00 (Hcalc. = 3.56).
To a solution of 40 mmol of the respective ani-
line derivative in toluene, 15 mmol of the corre-
sponding diketo compound and a catalytic amount
of p-toluenesulfonic acid were given. The mixture
was heated under reflux. The resulting water was
removed as azeotropic mixture using a Dean–Stark
apparatus. The progress of the reaction was ob-
served by GC. After 12–24 h the reaction mix-
ture was cooled to room temperature and filtered
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 obtained as yellow crystals. Yields: 2a, 55%;
2b, 65%; 2c, 65%; 3a, 35%; 3b, 45%; 3c, 50%;
4a, 25%; 4b, 25%; 4c, 30%; 4d, 35%. All com-
pound were characterized by NMR spectroscopy
(Table 3).
3.4. General procedure for the activation of the
(α-diimine)nickel(II) complexes
A 5–10 mg of the complex were suspended in
toluene and activated with the corresponding 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 suspension was used
for ethylene polymerization within 30 mm.
3.5. Homogeneous ethylene polymerization
The activated complex was added to a 1 l metal auto-
clave (Büchi), filled with 250 ml n-pentane. The poly-
merizations were performed under an ethylene pres-
sure of 10 bar (99.98% ethylene, dried over aluminium
oxide) and at a temperature of 60 ◦C. After a period of

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M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
Table 3
1H and 13C NMR data of compounds 1a–4d
No.
1H NMRa
13C NMRb
1a
7.18 (m, 4H), 6.59 (m, 2H), 2.20 (s, 6H), 2.15 (s, 6H)
Cq: 168.0, 150.4, 135.1, 124.9; CH: 126.6, 124.4, 115.9;
CH3: 15.5, 14.5
Cq: 168.2, 147.8, 129.0, 128.8; CH: 130.2, 126.3, 118.8;
CH3: 17.7, 15.6
4
3
1b
1c
2a
2b
7.20 (d, 2H, JHH = 2.0 Hz), 7.15 (dd, 2H, JHH
=
4
3
8.3 Hz, JHH = 2.2 Hz), 6.55 (d, 2H, JHH = 8.3 Hz),
2.09 (s, 6H), 2.07 (s, 6H)
3
3
7.18 (d, 2H, JHH = 8.1 Hz), 7.03 (dd, 2H, JHH
=
Cq: 167.9, 150.1, 131.4, 124.9; CH: 131.3, 123.5, 117.3;
CH3: 17.0, 15.4
4
4
8.1 Hz, JHH = 2.7 Hz), 6.70 (d, 2H, JHH = 2.2 Hz),
2.13 (s, 6H), 2.12 (s, 6H)
3
7.11 (m, 4H), 6.54 (m, 2H), 2.60 (q, 2H, JHH
7.6 Hz), 2.15 (s, 6H), 2.09 (s, 3H), 1.04 (t, 3H, JHH
=
=
Cq: 172.6, 167.3, 150.7, 150.4, 135.3, 135.2, 124.9,
124.6; CH: 126.9, 126.8, 124.6, 124.4, 116.1, 116.0;
CH2: 21.9; CH3: 16.1, 14.9, 14.8, 12.3
Cq: 172.6, 167.2, 147.9, 147.7, 128.9, 128.7, 128.6,
128.4; CH: 130.3. 130.2, 126.4, 126.3, 118.8, 118.6;
CH2: 21.7; CH3: 17.82, 17.79, 16.0, 12.3
3
7.6 Hz)
4
3
7.20 (d, 2H, JHH = 1.9 Hz), 7.13 (d, 2H, JHH
=
3
4
8.2 Hz), 6.55 (dd, 2H, JHH = 8.2 Hz, JHH = 2.0 Hz),
3
2.59 (q, 2H, JHH = 7.6 Hz), 2.08 (s, 3H), 2.06 (s,
3
6H), 1.03 (t, 3H, JHH = 7.6 Hz)
3
4
2c
3a
7.13 (d, br, 2H, JHH = 8.2 Hz, JHH = 2.1 Hz), 6.99
Cq: 172.5, 167.3, 150.4, 150.1, 138.7, 125.0, 124.8;
CH: 131.5, 131.4, 123.7, 123.5, 117.5, 117.3; CH2:
21.9; CH3: 17.4, 17.3, 16.1, 12.3
3
4
(dd, 1H, JHH = 8.2 Hz, JHH = 1.3 Hz), 6.98 (dd,
3
4
4
1H, JHH = 8.2 Hz, JHH = 1.3 Hz), 6.65 (Vt, JHH
=
2.1 Hz), 2.60 (q, 2H, 3JHH = 7.5 Hz), 2.07 (s, 3H), 2.05
(s, br, 3H), 2.04 (s, br, 3H), 1.05 (t, 3H, 3JHH = 7.5 Hz)
3
3
7.11 (t, 2H, JHH = 2.9 Hz), 6.77 (d, 2H, JHH
=
Cq: 171.7, 150.6, 135.3, 124.6; CH: 126.8, 124.4, 116.0;
CH2: 22.1; CH3: 14.9, 12.0
3
2.8 Hz), 6.56 (d, 2H, JHH = 2.8 Hz), 2.58 (q, 4H,
3JHH = 7.5 Hz), 2.15 (s, 6H), 1.04 (t, 6H, JHH
=
3
7.5 Hz)
3b
3c
7.24 (s, 2H), 7.12 (d, 2H, 3JHH = 8.3 Hz), 6.64 (dd, 2H,
Cq: 171.6, 150.2, 131.6, 124.8; CH: 131.3, 123.5, 117.3;
CH2: 22.1; CH3: 17.5, 12.0
3JHH = 5 Hz, JHH = 1.8 Hz), 2.56 (q, 4H, JHH
=
=
4
3
3
7.5 Hz), 2.05 (s, 6H), 1.03 (t, 6H, JHH = 7.5 Hz)
4
3
7.24 (d, 2H, JHH = 1.3 Hz), 7.04 (dd, 2H, JHH
Cq: 173.2, 145.1, 134.4, 123.1; CH: 130.2, 127.9, 119.3;
CH2: 22.7; CH3: 20.6, 11.7
4
3
8.3 Hz, JHH = 1.3 Hz), 6.65 (d, 2H, JHH = 8 Hz),
3
2.58 (q, 4H, JHH = 7.5 Hz), 2.31 (s, 6H), 1.09 (t, 6H,
3JHH = 7.5 Hz)
4a
4b
7.92 (m, 2H), 7.68 (m, 2H), 7.47 (m, 10H), 7.20 (m,
Cq: 164.3, 148.1, 137.4, 134.8, 127.5; CH: 134.5, 131.9,
128.9, 128.2, 126.1, 117.7; CH3: 15.3
Cq: 163.1, 147.3, 137.9, 134.3, 129.7; CH: 131.4, 130.3,
128.9, 128.4, 125.5, 118.0; CH3: 16.5
2H)
4
7.87 (m, 4H), 7.41 (m, 6H), 6.92 (d, 2H, JHH
=
3
4
2.3 Hz), 6.73 (dd, 2H, JHH = 7.5 Hz, JHH = 2.3 Hz),
3
6.35 (d, 2H, JHH = 8.3 Hz), 1.31 (s, 6H)
4c
7.89 (m, 4H), 7.44 (m, 6H), 6.83 (m, 4H), 6.36 (m,
Cq: 163.6, 148.4, 137.8, 130.6, 130.4; CH: 131.6, 130.9,
129.0, 128.3, 124.7, 117.0; CH3: 16.3
Cq: 164.0, 143.1, 137.4, 136.4, 128.1; CH: 131.4, 130.1,
128.8, 128.5, 127.5, 118.6; CH3: 20.6
2H), 1.35 (s, 6H)
7.88 (m, 4H), 7.47–7.30 (m, 6H), 6.99 (d, 2H, JHH
4
4d
=
3
4
2.0 Hz), 6.65 (dd, 2H, JHH = 8.3 Hz, JHH = 2.0 Hz),
3
6.47 (d, 2H, JHH = 7.5 Hz), 2.16 (s, 6H)
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 (77.0).
1 h the autoclave was cooled to room temperature and
the pressure was reduced. The polymerization mixture
was filtered, the remaining polymer was washed with
half concentrated hydrochloric acid, dried in vacuo
and weighted. After removing n-pentane by destilla-
tion over a Vigreux column, the obtained oligomers
were analyzed by GC.
3.6. X-ray analysis
A Siemens P4 diffractometer (Mo K␣ radiation;
λ = 0.71073 Å) with a graphite monochromator was
used for the measurement of the reflection intensities.
The structure calculation was performed with Siemens
SHELXTL PLUS (VMS).

M. Helldörfer et al. / Journal of Molecular Catalysis A: Chemical 193 (2003) 59–70
69
Table 4
Mass spectrometric data of complexes 5a–8d
No.
Fragment (m/z) (intensity (%))
5a
5b
5c
6a
6b
6c
7a
7c
7b
8a
8b
8c
8d
M+ (–Me) = 537 (1), 421 (5), 377 (15), 332 (35), 297 (15), 210 (45), 166 (100), 130 (35), 125 (38)
M+ = 552 (1), 472 (3), 377 (10), 362 (15), 332 (90), 317 (100), 297 (18), 210 (28), 166 (100), 130 (100), 125 (100), 89 (100)
M+ (–Br, –Cl, –Me) = 422 (1), 332 (5), 317 (25), 166 (100), 131 (15), 125 (20), 89 (15)
M+ = 565 (1), 485 (1), 345 (30), 311 (10), 180 (100), 165 (75), 124 (50), 89 (20)
M+ (–Br) = 485 (1), 394 (5), 345 (15), 331 (20), 180 (100), 166 (80), 131 (15), 125 (15), 89 (10)
M+ (–Br) = 486 (1), 377 (5), 346 (5), 331 (20), 180 (100), 166 (80), 131 (10), 125 (45), 89 (20)
M+ (–Br, –Cl, –Me) = 450 (5), 406 (10), 360 (15), 325 (8), 226 (40), 180 (100), 146 (20), 125 (15), 89 (20)
M+ (–Br, –Cl, –Me) = 450 (1), 406 (4), 360 (8), 345 (10), 325 (4), 226 (10), 180 (100), 146 (10), 125 (15), 89 (10)
M+ (–Cl) = 545 (1), 406 (10), 360 (5), 325 (95), 226 (10), 180 (100), 125 (15), 89 (10)
M+ (–2Br, –Me) = 501 (2), 456 (75), 421 (5), 379 (2), 272 (5), 228 (100), 193 (90), 125 (65), 89 (60)
M+ (–Br, –Cl, –Me) = 546 (5), 502 (10), 456 (10), 422 (5), 272 (30), 228 (100), 193 (65), 125 (30), 89 (45)
M+ (–Br, –Cl, –Me) = 546 (5), 502 (10), 456 (15), 441 (5), 422 (3), 272 (15), 228 (100), 193 (20), 125 (10), 89 (10)
M+ (–Br, –Cl, –Me) = 546 (8), 502 (10), 487 (8), 456 (15), 441 (8), 422 (3), 272 (45), 228 (100), 193 (50), 125 (25), 89 (35)
C54H54Br6Cl6N6Ni3 (5b): red brown hexago-
[2] G. Wilke, Angew. Chem. 100 (1988) 189;
G. Wilke, Angew. Chem. Int. Ed. Engl. 100 (1988) 185.
[3] W. Keim, F.H. Kowaldt, R. Goddard, C. Krüger, Angew.
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W. Keim, F.H. Kowaldt, R. Goddard, C. Krüger, Angew.
Chem. Int. Ed. Engl. 90 (1978) 466.
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3635937 (1969).
[5] W. Keim, R.F. Mason, P. Glockner, US Patent 3647914
(1972).
[6] W. Keim, R. Appel, A. Storeck, C. Krüger, R. Goddard,
Angew. Chem. 93 (1981) 91;
W. Keim, R. Appel, A. Storeck, C. Krüger, R. Goddard,
Angew. Chem. Int. Ed. Engl. 93 (1981) 116.
[7] M. Peuckert, W. Keim, Organometallics 2 (1983) 594.
[8] U. Klabunde, S.D. Ittel, J. Mol. Catal. 41 (1987) 123.
[9] K.A. Ostoja Starzewski, J. Witte, Angew. Chem. 100 (1988)
861;
nal prism crystallized in diethylether/acetone of the
dimension 0.18 mm × 0.12 mm × 0.10 mm trigo-
nal; space group: P-3; a = 13.1758(13) Å, c =
23.958(6) Å, Z = 2, d(calc.) = 1.526 mg m−3, absorp-
tion coefficient: 4.362 mm−1, minimum/maximum
transmission coefficients: 0.9413/0.534, F(000) =
1632, measured reflections: 5437, independent reflec-
tions: 4179, goodness-of-fit: 1.000, R = 10.45%.
Crystallographic data (excluding structure factors)
for the structure reported in this paper have been
deposited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC-xxxx.
Copies of the data can be obtained free of charge on
application to The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: +44-1223-336-033;
e-mail: deposit@chemcrys.cam.ac.uk).
K.A. Ostoja Starzewski, J. Witte, Angew. Chem. Int. Ed.
Engl. 100 (1988) 839.
[10] K.A. Ostoja Starzewski, J. Witte, Angew. Chem. 97 (1985)
610;
K.A. Ostoja Starzewski, J. Witte, Angew. Chem. Int. Ed.
Engl. 24 (1985) 599.
[11] K.A. Ostoja Starzewski, J. Witte, H. Barti, European Patent
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Acknowledgements
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We thank Chevron Phillips Chemical Co., USA,
for the financial support and Dr. C. Erdelen for the
HT-GPC measurements.
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