New bis(imino)pyridine-iron(II)- and cobalt(II)-based catalysts: Synthesis, characterization and activity towards polymerization of ethylene

Article abstract of DOI:10.1016/S0022-328X(01)01418-8

The synthesis of a new series of iron(II)- and cobalt(II)-based complexes of the general formula M(N_ON_ON) Cl₂ (M = Fe; M = Co) bearing 2,6-bis(imin)pyridyl ligands [A-N=C-Py-C=N-A] that carry bulky, alkyl-free aromatic terminals (A = naphthyl, pyrenyl, 2-benzylphenyl, phenyl) or chiral cycloaliphatic auxiliary moieties (A = ((-)-cis-myrtanyl) is described. The Fe(II) complexes are exceptionally active (up to 40800 kg PE/(mol M h) towards the polymerization of ethylene in the presence of methylaluminoxane (MAO) as activator. Varying the steric bulkiness of the aromatic groups in the tridentate ligands affects catalytic productivity, molecular weight and for the first time the microstructure of the resulted material. The Fe(II) precatalysts are an order of magnitude more active than the corresponding Co(II) precatalysts.

Full text of DOI:10.1016/S0022-328X(01)01418-8

Journal of Organometallic Chemistry 648 (2002) 55–61
www.elsevier.com/locate/jorganchem
New bis(imino)pyridine-iron(II)- and cobalt(II)-based catalysts:
synthesis, characterization and activity towards polymerization of
ethylene
Adnan S. Abu-Surrah a,*, Kristian Lappalainen b, Ulla Piironen b, Petri Lehmus c,
b
Timo Repo b, Markku Leskela¨
a Department of Chemistry, Hashemite Uni6ersity, PO Box 150459, Zarqa 13115, Jordan
b Department of Chemistry, Laboratory of Inorganic Chemistry, PO Box 55, FIN-00014 Uni6ersity of Helsinki, Helsinki, Finland
c Borealis Polymers Oy, PO Box 330, FIN-06101 Por6oo, Finland
Received 21 June 2001; accepted 8 October 2001
Abstract
The synthesis of a new series of iron(II)- and cobalt(II)-based complexes of the general formula M(NSNSN)Cl2 (M=Fe;
M=Co) bearing 2,6-bis(imin)pyridyl ligands [A–NꢀC–Py–CꢀN–A] that carry bulky, alkyl-free aromatic terminals (A=naph-
thyl, pyrenyl, 2-benzylphenyl, phenyl) or chiral cycloaliphatic auxiliary moieties (A=((−)-cis-myrtanyl) is described. The Fe(II)
complexes are exceptionally active (up to 40800 kg PE/(mol M h) towards the polymerization of ethylene in the presence of
methylaluminoxane (MAO) as activator. Varying the steric bulkiness of the aromatic groups in the tridentate ligands affects
catalytic productivity, molecular weight and for the first time the microstructure of the resulted material. The Fe(II) precatalysts
are an order of magnitude more active than the corresponding Co(II) precatalysts. © 2002 Elsevier Science B.V. All rights
reserved.
Keywords: Iron(II)- and cobalt(II)-complexes; Diimine ligands; Linear and branched polyethylene; Polymerization catalysts; Methylaluminoxane
of technically important polar monomers with ethylene
are produced exclusively by radical polymerization
routes in high-pressure processes [5]. Therefore, there is
still a great interest to discover and develop new
families of polymerization catalyst that can allow more
control on the polymer material properties.
1. Introduction
The discovery of methylaluminoxane (MAO) as co-
catalyst for olefin polymerization has allowed an explo-
sive development of new homogeneous Ziegler–Natta
catalysts. A huge number of Group IV metal complexes
have been synthesized and tested as polymerization
catalysts after activation with MAO.
Worldwide research activities on Single-site, metal-
locene-based catalysts [1–3] have led to convincing
improvements of poly(1-olefin) materials as well as to
understanding of basic reaction mechanisms responsible
for the growth of a stereoregular polymer chain at a
metal center. However, this catalyst generation allows
only the use of a limited number of polar monomers
bearing sterically hindered functionalities due to the
sensitivity of early transition metal complexes to elec-
tron-donating functional groups [4]. Thus, copolymers
Late metal complexes are the most attractive candi-
dates because of their tolerance towards polar function-
alities. However, until middle of 90s only few reports
were introduced utilizing these compounds as catalysts
for polymerization of 1-olefins and ethylene [6]. This
could be due to the fact that these catalysts generally
exhibit reduced activities for olefin insertion and b-hy-
dride elimination, which steadily competes with chain
growth resulting in the formation of oligomers [7].
In 1995 Brookhart and coworkers reported new
Ni(II)- and Pd(II)-based catalysts bearing bulky diimine
ligands for ethylene polymerization [8,9]. These cata-
lysts are highly active and produce high molecular
weight polymers. The bulky substituents on the aryl
groups of the ligands block an associative olefin ex-
change, thus effectively retarding chain transfer pro-
* Corresponding author. Tel.: +962-5-382-6600x4315; fax: +962-
5-382-6613.
E-mail address: asurrah@hu.edu.jo (A.S. Abu-Surrah).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01418-8

56
A.S. Abu-Surrah et al. / Journal of Organometallic Chemistry 648 (2002) 55–61
cesses. Furthermore, the microstructure of the polymers
produced is a function of temperature, monomer pres-
sure, steric bulkiness of the auxiliary ligands, and tran-
sition metal center. Variation of these factors allows
access to a range of linear and branched polyethylene.
More recently, iron(II)- and cobalt(II)-based/MAO
catalysts systems that are capable for polymerizing
ethylene were reported by Brookhart et al. [10] and
Gibson et al. [11,12] The complexes are pentacoordi-
nate bearing 2,6-bis(imino)pyridyl tridentate ligands
with substituted aryl groups as terminals. In contrast to
palladium(II)- and nickel(II)-based catalysts that pro-
duce linear or branched polyethylene, these iron(II) and
cobalt(II) catalysts produce only highly linear
polyethylene. Ligand substituents have no influence on
the polymer microstructure even at high temperatures
and low ethylene pressure. By utilizing catalysts which
are lacking the ortho-alkyl substituents on the aryl
groups of the ligand only oligomers or polymer traces
were isolated [13].
In this report we describe the synthesis of new
iron(II) and cobalt(II)- based complexes bearing 2,6-
bis(imino)pyridyl ligands that contain bulky aromatic
terminals such as pyrenyl, 2-benzylphenyl, and naph-
thyl. The new catalysts are remarkably active towards
polymerization of ethylene. Varying the steric bulkiness
of the aryl groups in the tridentate ligands can allow
the control of both the molecular weight and the mi-
crostructure of the resulted polyethylene. In addition,
the increase of the steric bulk of the aromatic groups of
the ligand parallels the increase of catalyst productivity.
2. Results and discussion
2.1. Ligands and complexes
The tridentate 2,6-bis(imino)pyridine ligands (3a–3e)
were prepared in high yields by the condensation reac-
tion of 2,6-diacetylpyridine (1) with two equivalent of
the desired amine (2a–2e) in MeOH at 50 °C in the
presence of catalytic amount of formic acid (Scheme 1).
Treatment of the metal salts FeCl2, and CoCl2 with
the ligands (3a–3e) in THF for 24 h afford the com-
plexes (4a–4e and 5a–5c) (Scheme 2) with high to
moderate yields.
To confirm the identity of the compounds prepared
in the present study, a variety of techniques including
elemental analysis, mass spectroscopy (EI), infrared
1
spectroscopy, H- and 13C-NMR, and magnetic suscep-
tibility (veff, BM) have been used. The isolated com-
plexes are microcrystalline or powder-like and stable at
atmospheric conditions.
Magnetic susceptibility (veff, BM) of the complexes
were determined by a Faraday balance at room temper-
ature. All complexes are paramagnetic. The iron(II)
complexes (4a–4c) and the analogous cobalt(II) com-
plexes (5a–5c) are high spin species with a magnetic
moment (veff) of 4.55–5.42 BM [14], but complexes 4d
and 4e afford a magnetic moment of 1.52 and 2.71 BM,
respectively. The electronic environment of the com-
plexes was also influenced by the ligand substituents. In
the complexes 4a–4c, a slight difference in the magnetic
moment values with varying the bulkiness of the auxil-
iary aromatic groups was observed, which suggests the
presence of some dissimilarity in the geometry among
the penta-coordinated complexes.
Amines (1-naphthylamine, 1-aminopyrene, 2-benzy-
laniline, aniline, (−)-(cis)-myrtanylamine) that are
used as auxiliary ligands were optimized at the B3LYP/
SV(P) level of theory by using Gaussian 98 code [15].
Their electronic properties were evaluated by making
use of NBO analysis. The results showed that only
negligible changes are observed on the electronic prop-
erties of the nitrogen upon varying the bulkiness of the
Scheme 1. Synthesis and structures of the tridentate bis(imino)-
pyridine ligands (3a–3e).
,
aryl groups (C–N bond length $1.39 A; charge at N
$ −0.83; purity of lone pair $91–92%), while major
alterations were observed upon replacing the aryl by
the alkyl substituent (−)-(cis)-myrtanyl (C–N bond
,
length $1.46 A; charge at N $ −0.89; purity of lone
pair $98%). This suggests that the steric bulkiness of
the aryl groups is the major factor that influencing the
catalytic activity among the complexes 4a–4e.
Scheme 2. Synthesis of the iron(II) (4a–4e) and cobalt(II) complexes
(5a–5c) reported in the present study.

A.S. Abu-Surrah et al. / Journal of Organometallic Chemistry 648 (2002) 55–61
57
Table 1
Polymerization results
a
b
Entry no.
Cat. code
Catalyst
Loading (mmol) Pressure (bar)
Yield (g)
Activity 103 kg
PE/mol cat. h
Mw
Tm (°C)
×103
1
2
3
4
5
6
7
8
9
4a
5a
4b
5b
4c
4c
4c
5c
4d
4e
(BNaEP)FeCl2
(BNaEP)CoCl2
(BPyEP)FeCl2
(BPyEP)CoCl2
(BBzEP)FeCl2
(BBzEP)FeCl2
(BBzEP)FeCl2
(BBzEP)CoCl2
(BMyEP)FeCl2
(BPhEP)FeCl2
3.0
3.0
3.0
3.0
3.0
1.0
1.1
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
2.0
1.0
3.0
3.0
3.0
28.5
2.02
33.7
0.31
44.0
20.43
3.25
0.22
0.1
9.50
0.673
13.48
0.103
11.00
40.86
2.96
0.073
0.033
0.063
165.2
63.0
19.5
43.8
4.30
3.70
21.9
4.60
37.3
n.d. c
115
129
110, 121
128
125
n.d. c
109, 122
123
90, 126
125
10
0.19
Conditions: cat/MAO, 1:1000 (entry 7, 1:300); solvent (toluene, 200 ml); polymerization time 60 min (entry 6, 30 min); temperature, 30 °C.
a Molecular weight data reported against polystyrene standards.
b Determined by differential scanning calorimetry.
c n.d.: not determined.
2.2. Polymerization experiments
dine (3a) produce branched polymers (Fig. 1B and C,
respectively). The extent of branching is decreased
when utilizing complex 4b that contains the more bulky
pyrenyl groups. Analysis of the spectra indicates that
both methyl (l=20.0 ppm) and ethyl branching (l=
11.1 and 39.5 ppm) are taking place [17].
The catalysts are generated in situ in toluene by the
addition of methylaluminoxane as activator in the pres-
ence of ethylene. The polymerization results with the
different precatalysts are summarized in Table 1.
Complex 4c [(BBzEP)FeCl2], where the ligand carries
one benzyl substituent on each phenyl group, exhibits
extremely high activities that is about 20-fold more
compared with the most active iron(II) catalysts re-
ported previously under similar polymerization condi-
tion. For example the activity of precatalyst 4c (entry 6,
Table 1) is 40800 kg PE/(mol Fe h), while that for the
precatalyst [Fe{(2,6-i-PrPh)2PBIMe2}Cl2] (I) (2,6-i-
PrPh)2PBIMe2: 2,6-bis(1-(2,6-diisopropylphenylimino)-
ethyl)pyridine) [10] that contains 2,6-diisopropylphenyl
as terminal moieties is 1655 kg PE/(mol Fe h) under the
The molecular weights vary with modification of the
ligands and metal (Table 1). GPC measurements
showed that the resulted materials contain high molar
mass polyethylene together with low molecular weight
portion. Broad molecular weight distributions (Mw/Mn)
were observed, which is typical for these MAO-acti-
vated Fe(II) complexes bearing 2,6-bis(imino)pyridyl
tridentate ligands with alkyl substituted aryl groups
[8,10]. According to differential scanning calorimetry
(DSC), the polymer samples exhibit melting tempera-
tures (Tm) ranging from 90 to 129 °C (Table 1).
The mechanism of polymerization using 4c is thought
to be similar to that with other systems and involves a
cationic alkyl complex as the active species. Coordina-
tion of ethylene to the metal center followed by migra-
tory insertion into the M-alkyl bond, leads to chain
growth and regeneration of an alkyl species. This can
undergo further ethylene insertion, giving long polymer
chain [18]. The formation of branched polyethylene
upon utilizing the precatalysts 4a and 4b could took
place according to the mechanism proposed for the
branch formation in the presence of Ni(II) and Pd(II)
diimine catalysts [19].
same polymerization conditions (Mw=217×103
g
mol−1; Mw/Mn=47.9).
For comparison reasons, the ligands 2,6-bis[(1-
phenylimino)ethyl]pyridine (3e) (carry only phenyl
groups as terminals), 2,6-bis[(1-(cis)-myrtanylimino)-
ethyl]pyridine (3d) (carry chiral cycloaliphatic groups)
and their iron(II) chloride complexes were prepared and
tested for polymerization of ethylene. Both precatalysts
showed only low polymerization activities under similar
reaction conditions (Table 1). Very low activity was
also observed for the catalysts based on the correspond-
ing aldimine ligands [16].
Varying the bulky aryl terminals on the bis (imino)
pyridine ligand produces polymers with different mi-
crostructure. According to 13C-NMR analysis (Fig. 1),
the Fe(II) catalyst bearing the ligand 2,6-bis[1-(2-ben-
zylphenylimino)ethyl]pyridine (3c) can convert ethylene
to a linear polymer (Fig. 1A), while precatalysts which
contain the ligands 2,6-bis[(1-pyrenyl-imino)ethyl]-
pyridine (3b) and 2,6-bis[(1-naphthylimino)ethyl] pyri-
In summary, we report on highly active 2,6-
bis(arylimino)pyridine iron(II)- and cobalt(II)-based
ethylene polymerization catalysts, which lack the ortho
alkyl substituents on the aryl groups. This is the first
report on iron(II) catalysts where only the variation of
the ligand substituents allows access to an ethylene
polymer with different microstructures. Successful poly-

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A.S. Abu-Surrah et al. / Journal of Organometallic Chemistry 648 (2002) 55–61
merization of propylene at 30 °C and copolymerization
of ethylene with higher olefins will be reported
shortly.
10 mm probe in TCB at 100 °C. Infrared spectra were
measured on BIO-RAD FTS-7 FT-IR spectrometer
using KBr pellet. Mass spectra (EI) were acquired with
a JEOL JMS-SX102 mass spectrometer. Molecular
weight and molecular weight distributions were mea-
sured by gel permeation chromatography (GPC) rela-
tive to polystyrene standards. Magnetic susceptibility
(veff, BM) of the complexes was determined by Faraday
balance at room temperature (r.t.). The structures of
1-naphthylamine, 1-aminopyrene, 2-benzylaniline, ani-
line and (−)-(cis)-myrtanylamine were optimized at
the B3LYP/6-31G level of theory by using Gaussian 98
code, and their electronic properties were evaluated by
making use of NBO analyses. The calculated IR spectra
at the same level did not show any imaginary
frequencies.
3. Experimental
All reactions were carried out under dry argon using
standard Schlenk techniques. Elemental analyses were
performed at the Pharmacology Department, Univer-
sity of Helsinki (EA 1110 CHNS-O CE instrument).
1H-NMR spectra were recorded on a Varian Gemini
200 spectrometer operating at 200 MHz. 13C-NMR
spectra of the ligands were obtained on a Varian Gem-
ini 200 spectrometer operating at 50.286 MHz and
those of polymers on a Varian Gemini 2000 (75 MHz),
Fig. 1. 13C-NMR spectra of polyethylene produced with different catalysts: (A) (BBzEP)FeCl2 (4c, entry 5); (B) (BPyEP)FeCl2 (4b); (C)
(BNaEP)FeCl2 (4a).

A.S. Abu-Surrah et al. / Journal of Organometallic Chemistry 648 (2002) 55–61
59
3.1. Synthesis of ligands
ml) and five drops of formic acid. After 1 h of stirring
at r.t., a white precipitate was formed which was col-
lected after 14 h, washed with cold methanol (2×20
ml) and dried in vacuum.
3.1.1. 2,6-bis[(1-Naphthylimino)ethyl]pyridine (BNaEP)
(3a)
1
A solution of 2,6-diacetylpyridine (1) (2.0 g, 12.3
mmol) in MeOH (25 ml) was added to a solution of
1-naphthylamine (2a) (3.7 g, 25.7 mmol) in the same
solvent (25 ml) and three drops of 97% formic acid.
After 1 h stirring at r.t., a yellow precipitate was
formed which was collected after 5 h, washed with cold
methanol (2×25 ml) and dried in vacuum.
Yield: 1.2 g (65%), m.p. 106 °C. H-NMR (CDCl3):
l=8.07 (d, J (5.0 Hz), Harom.), 7.68 (t, J (5.0 Hz),
Harom.), 3.54–3.52 (m, 4H, CH2-Myrtanyl), 2.39 (s, 6H,
CH3CꢀN), 1.21, 1.09 (2s, 12H, CH3-myrtanyl). 13C {1H}-
NMR (CDCl3): l=166.2 (CꢀN), 13.97 (CH3CꢀN). IR
(KBr, cm−1): 1639 m (CꢀN). Anal. Calc. for C29H43N3:
C, 80.32; H, 9.99; N, 9.98. Found: C, 79.99; H, 10.03;
N, 9.06%.
1
Yield: 2.75 g (54%), m.p. 172 °C. H-NMR (CDCl3):
l=8.68–6.89 (m, 17H, Harom.), 2.47 (s, 6H, CH3CꢀN).
13C {1H}-NMR (CDCl3): l=168.4 (CꢀN). IR (KBr,
cm−1): 1638 m (CꢀN). Anal. Calc. for C29H23N3: C,
84.23; H, 5.61; N, 10.16. Found: C, 83.98; H, 5.85; N,
10.32%.
3.1.5. 2,6-bis[(1-Phenylimino)ethyl]pyridine (BPhEP)
(3e)
A solution of (1) (1.0 g, 6.13 mmol) in MeOH (25 ml)
was added to a solution of aniline (2e) (1.23 g, 13.21
mmol) in the same solvent (25 ml) and three drops of
97% formic acid. After 1 h of stirring at r.t., a yellow
precipitate was formed which was collected after 5 h,
washed with cold methanol (2×15 ml) and dried in
vacuum.
Yield: 1.30 g (68%). Anal. Calc. for C21H19N3: C,
80.48; H, 6.11; N, 13.40. Found: C, 79.93; H, 6.38; N,
14.04%.
3.1.2. 2,6-bis[(1-Pyrenylimino)ethyl]pyridine (BPyEP)
(3b)
A solution of (1) (0.29 g, 1.78 mmol) in MeOH
(25ml) was to added a solution of 1-aminopyrene (2b)
(0.85 g, 3.92 mmol) in the same solvent (25 ml) and
three drops of 97% formic acid. The reaction mixture
was stirred at 50 °C for 3 days after which the orange
product was filtered, washed with pentane (2×50 ml)
and dried in vacuum.
3.2. Synthesis of complexes
1
Yield: 0.92 g (92%), m.p. 241 °C. H-NMR (CDCl3):
l=8.77–7.49 (m, 21H, Harom.), 2.47 (s, 6H, CH3CꢀN).
13C {1H}-NMR (CDCl3): l=168.9 (CꢀN), 17.04
(CH3CꢀN). IR (KBr, cm−1): 1633 m (CꢀN). Anal.
Calc. for C42H27N3: 0.5 H2O: C, 86.29; H, 4.94; N, 7.36.
Found: C, 86.38; H, 4.88; N, 7.35%.
3.2.1. 2,6-bis[(1-Naphthylimino)ethyl]pyridine iron(II)
chloride (4a) [20] and 2,6-bis[(1-naphthyl-imino)ethyl]-
pyridine cobalt(II) chloride (5a)
A filtered solution of the ligand 3a (0.70 g, 1.69
mmol) in THF (50 ml) was added to FeCl2 or CoCl2
(1.54 mmol) under continuous stirring at r.t. Upon
addition a precipitate started to form gradually. After
24 h, the solid was filtered, washed with THF (2×25
ml), n-pentane (2×25 ml) and dried in vacuum.
4a, Yield: 0.46 g (55%), greenish–blue. M.p. (dec)
200 °C. (MS, EI): m/z (%) 539 (5%), 466 (5%), 413
(100%), 271 (60%). IR: w [cm−1]=1593 s (CꢀN). Anal.
Calc. for C29H23N3FeCl2: C, 64.47; H, 4.29; N, 7.78.
Found: C, 63.96; H, 4.51; N, 7.39%. veff (Faraday
balance): 4.86 BM.
5a, Yield: 0.55 g (65%), brown. M.p. (dec) 240 °C.
(MS, EI): m/z (%): 413 (100%), 271 (60%). IR: w
[cm−1]=1593 s (CꢀN). Anal. Calc. for C29H23N3-
CoCl2·0.5 H2O: C, 63.05; H, 4.37; N, 7.60. Found: C,
62.77; H, 4.44; N, 7.19%. veff: 4.78 BM.
3.1.3. 2,6-bis[1-(2-Benzylphenylimino)ethyl]pyridine
(BBzEP) (3c)
A solution of (1) (1.0 g, 6.13 mmol) in MeOH (25 ml)
was added to a solution of 2-benzylaniline (2c) (2.36 g,
12.87 mmol) in the same solvent (25 ml) and three
drops of 97% formic acid. The reaction mixture was
stirred at 50 °C for 2 days after which the solvent was
evaporated to dryness and the resulted yellow oily
product was washed with cold methanol (2×5 ml),
pentane (2×15 ml) and dried in vacuum.
Yield: 2.73 g (90%). 1H-NMR (CDCl3): l=8.46–
6.68 (m, 21H, Harom.), 2.47 (s, 6H, CH3CꢀN). 13C
{1H}-NMR
(CDCl3):
l=167.4
(CꢀN),
38.2
(CH2-benzyl), 16.1 (CH3CꢀN). IR (KBr, cm−1): 1638 m
(CꢀN). Anal. Calc. for C35H31N3: C, 85.15; H, 6.32; N,
8.51. Found: C, 84.82; H, 6.41; N, 8.63%.
3.2.2. 2,6-bis[(1-Pyrenylimino)ethyl]pyridine iron(II)
chloride (4b) and 2,6-bis[(1-pyrenylimino)-ethyl]pyridine
cobalt(II) chloride (5b)
A filtered solution of the ligand 3b (0.25 g, 0.445
mmol) in THF (50 ml) was added to FeCl2 or CoCl2
(0.394 mmol) under continuous stirring at r.t. Upon
addition a precipitate started to form. After 24 h, the
3.1.4. 2,6-bis[(1-(cis)-Myrtanylimino)ethyl]pyridine
(BMyEP) (3d)
A solution of (1) (0.696 g, 4.26 mmol) in MeOH
(25ml) was added a to solution of (−)-(cis)-myrtany-
lamine (2d) (1.37 g, 8.94 mmol) in the same solvent (25

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A.S. Abu-Surrah et al. / Journal of Organometallic Chemistry 648 (2002) 55–61
solid was filtered, washed with THF (2×25 ml), n-pen-
tane (2×25 ml) and dried in vacuum.
3.3. Polymerization experiments
4b, Yield: 0.17 g (63%), brown. M.p. (dec) 270 °C.
IR:
C41H27N3FeCl2: C, 71.53; H, 3.95; N, 6.10. Found: C,
71.60; H, 4.21; N, 5.93%. veff: 4.55 BM.
All polymerization reactions were performed in a 1-l
Bu¨chi glass reactor. In a typical polymerization experi-
ment, the autoclave was charged with 200 ml toluene
and the system was charged with ethylene up to the
desired concentration and the appropriate amount of
the complex and MAO (mixed previously together).
Pressure, inside temperature and the consumption of
ethylene as a function of time were recorded online
with Advantech GENIE® runtime software. The mechan-
ical stirrer was run with 1800 rpm for all experiments to
avoid diffusion controlled polymerization reactions. Af-
ter the desired polymerization time, the polymerization
were stopped by quenching with methanol containing
2% HCl. Polymers were washed with methanol and
dried overnight at 70 °C.
w s (CꢀN). Anal. Calc. for
[cm−1]=1588
5b, Yield: 0.20 g (73%), brown. M.p. (dec) 340 °C.
IR:
w s (CꢀN). Anal. Calc. for
[cm−1]=1587
C41H27N3CoCl2: C, 71.21; H, 3.93; N, 6.07. Found: C,
71.47; H, 4.31; N, 5.78%. veff: 4.82 BM.
3.2.3. 2,6-bis[(1-(2-Benzylphenylimino)ethyl]pyridine
iron(II) chloride (4c) and 2,6-bis[(1-(2-benzylphenyl-
imino)ethyl]pyridine cobalt(II) chloride (5c)
A filtered solution of the ligand 3c (0.50 g, 1.01
mmol) in THF (50 ml) was added to FeCl2 or CoCl2
(0.78 mmol) under continuous stirring at r.t. Upon
addition a precipitate started to form. After 24 h, the
solid was filtered, washed with THF (2×25 ml), n-pen-
tane (2×25 ml) and dried in vacuum.
Acknowledgements
4c, Yield: 0.27 g (56%), blue. M.p. (dec) 232 °C. IR:
Financial support by Fortum oy and Magnus Ehrn-
rooth foundation is gratefully acknowledged. KL
thanks the Graduate School of Inorganic Material
Chemistry, Finland. TR extends his acknowledgements
to the Academy of Finland for financial support. The
authors would also like to thank Docent H. Muhonen
for the magnetic susceptibility measurements and Do-
cent M. Sundberg and Docent R. Uggla for preliminary
modeling calculations.
w
[cm−1]=1590
s
(CꢀN). Anal. Calc. for
C35H31N3FeCl2: C, 67.76; H, 5.03; N, 6.77. Found: C,
67.90; H, 5.12; N, 6.48%. veff: 5.42 BM.
5c, Yield: 0.38 g (78%), light green. M.p. (dec)
317 °C. IR: w [cm−1]=1591 s (CꢀN). Anal. Calc. for
C35H31N3CoCl2: C, 67.42; H, 5.01; N, 6.74. Found: C,
67.63; H, 5.33; N, 6.55%. veff: 4.73 BM.
3.2.4. 2,6-bis[(1-(cis-Myrtanylimino)ethyl]pyridine
iron(II) chloride (4d)
References
A filtered solution of the ligand 3d (0.40 g, 0.922
mmol) in THF (50 ml) was added to FeCl2 (0.106 g,
0.836 mmol) under continuous stirring at r.t. Upon
addition a dark blue precipitate started to form. After
24 h, the solid was filtered, washed with THF (2×25
ml), n-pentane (2×25 ml) and dried in vacuum.
Yield: 0.43 g (91%), blue powder. M.p. (dec) 205 °C.
(MS, EI): m/z (%): 560 (5%), 435 (60%), 364 (50%), 310
(100%)+. IR: w [cm−1]=1530 m (CꢀN). Anal. Calc. for
C29H43N3FeCl2·2H2O: C, 58.39; H, 7.94; N, 7.04.
Found: C, 58.08; H, 7.79; N, 6.20%. veff: 1.52 BM.
[1] H. Sinn, W. Kaminsky, Adv. Organomet. Chem. 18 (1980) 99.
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3.2.5. 2,6-bis[(1-Phenylimino)ethyl]pyridine iron (II)
chloride (4e)
A filtered solution of the ligand 3e (0.50 g, 1.59
mmol) in THF (50 ml) was added to FeCl2 (0.18 g, 1.42
mmol) under continuous stirring at r.t. Upon addition
a dark blue precipitate started to form. After 24 h, the
solid was filtered, washed with THF (2×25 ml), n-pen-
tane (2×25 ml) and dried in vacuum.
[5] K.W. Doak, in: H.F. Mark (Ed.), Encyclopedia of Polymer
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2,2-bipyridyl can catalyze the oligomerization of olefins. At-
tempts of using these catalysts for polymerization reactions
showed that a facile deactivation of the catalyst via ß-hydride
migration occurred due to the labile coordination of the
Yield: 0.47 g (75%), blue. M.p. (dec) 206 °C. IR: w
[cm−1]=1590
C21H19N3FeCl2: C, 57.30; H, 4.35; N, 9.54. Found: C,
m
(CꢀN).
Anal.
Calc.
for
57.12; H, 4.49; N, 9.17%. veff: 2.71 BM.

A.S. Abu-Surrah et al. / Journal of Organometallic Chemistry 648 (2002) 55–61
61
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[20] We recently found that one of our complexes (4a) has been
prepared by another research group and utilized for polymeriza-
tion of ethylene in the presence of MAO and a chlorinated
solvent (J. Qiu, Y. Li, Y. Hu, Polym. Int. 49 (2000) 5). In
addition to the fact that the complex was not fully characterized,
the authors reported that it was isolated as a black powder,
which is not a typical color for such penta-coordinated iron(II)
complexes. Consequently, the compound showed low activity
(91.0 kg PE/(mol Fe h)). This is about 100 times less compared
to that reported by us.