New bis(arylimino)pyridyl complexes as components of catalysts for ethylene polymerization

Article abstract of DOI:10.1023/B:KICA.0000023788.95153.d5

A new series of 2,6-bis(arylimino)pyridineiron(II) complexes with cycloaliphatic (cyclopentyl, cyclohexyl, cyclooctyl, and cyclododecyl) substituents in the ortho position of the aryl ring are synthesized and studied as components for ethylene polymerization catalysts. Methylaluminoxane is used as an activator for the complexes. The resulting catalytic systems are more active in polymerization at elevated temperatures (60-80°C) than previously described systems based on substituted 2,6-bis(arylimino)pyridines. The influence of the number of CH₂ groups in a cycloaliphatic substituent on the efficiency of the catalytic system is studied. Polymers formed are characterized by an increased molecular weight, high density, and high crystallinity.

Full text of DOI:10.1023/B:KICA.0000023788.95153.d5

Kinetics and Catalysis, Vol. 45, No. 2, 2004, pp. 176–182. Translated from Kinetika i Kataliz, Vol. 45, No. 2, 2004, pp. 192–198.
Original Russian Text Copyright © 2004 by Ivanchev, Tolstikov, Badaev, I.I. Oleinik, Ivancheva, Rogozin, I.V. Oleinik, Myakin.
CATALYTIC REACTION
MECHANISMS
New Bis(arylimino)pyridyl Complexes as Components
of Catalysts for Ethylene Polymerization
S. S. Ivanchev*, G. A. Tolstikov**, V. K. Badaev*, I. I. Oleinik**, N. I. Ivancheva*,
D. G. Rogozin*, I. V. Oleinik**, and S. V. Myakin*
* Boreskov Institute of Catalysis (St. Petersburg Branch), Siberian Division, Russian Academy of Sciences,
St. Petersburg, Russia
** Vorozhtsov Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia
Received March 28, 2003
Abstract—A new series of 2,6-bis(arylimino)pyridineiron(II) complexes with cycloaliphatic (cyclopentyl,
cyclohexyl, cyclooctyl, and cyclododecyl) substituents in the ortho position of the aryl ring are synthesized and
studied as components for ethylene polymerization catalysts. Methylaluminoxane is used as an activator for the
complexes. The resulting catalytic systems are more active in polymerization at elevated temperatures
(60−80°C) than previously described systems based on substituted 2,6-bis(arylimino)pyridines. The influence
of the number of CH2 groups in a cycloaliphatic substituent on the efficiency of the catalytic system is studied.
Polymers formed are characterized by an increased molecular weight, high density, and high crystallinity.
INTRODUCTION
related catalysts at polymerization temperatures above
40–50°ë.
First bis(arylimino)pyridines with the general struc-
In this work, we attempted to synthesize new 2,6-
bis(arylimino)pyridineiron(II) chloride complexes
retaining (in combination with methylaluminoxane as a
cocatalyst) their catalytic activity at temperatures
higher than the 40–60°ë used in this technology. With
this purpose we synthesized, for the first time, a series
of 2,6-bis(arylimino)pyridineiron complexes contain-
ing one or two cycloaliphatic ortho-substituents in the
aryl group [9]. This study is based on our first experi-
ment on studying 2,6-bis(arylimino)pyridines with
cyclopentyl substituents [10].
ture
R4
R2
R1
R3
Cl
N
N
N
Fe
Cl
R3
R1
R2
EXPERIMENTAL
Reagents and Solvents
R4
Toluene (special purity grade) was dried for 24 h
over calcined alumina, distilled in an argon flow over
metallic sodium, and stored in the presence of metallic
sodium in argon.
have recently been synthesized and studied as compo-
nents of catalysts for olefin polymerization by two
independent research groups in the United States[1, 2]
and Great Britain [3, 4]. The related catalysts turned out
to be very attractive due to their high activity (at the
level of metallocene catalysts), accessibility, and low
sensitivity to admixtures in a monomer (moisture, CO,
and others). During a short period, extensive experi-
mental data were accumulated on the synthesis of vari-
ous ligand structures of bis(arylimino)pyridine com-
plexes based on iron and cobalt halides and on the study
of their catalytic activity in α-olefin polymerization.
These were generalized in two reviews [5, 6].
Isopropyl alcohol (reagent grade) was used without
additional purification.
Ethylene with a purity of at least 99.5% and argon
(special purity grade) were dried by passing through
columns packed with calcined Al2O3 before supplying
to a reactor. After drying the moisture content of ethyl-
ene was at most 10–20 ppm and that of argon was at
most 10 ppm.
Polymethylaluminoxane from SL Witko GmbH
The 2,6-bis(arylimino)pyridine derivatives had a (Eurecen® Al 5100/10T) was used as a 10% solution in
certain limitation for their wide-spread use as reported toluene. According to analyses of the reagent producer,
in [3] and then in [7, 8]: a decrease in the activity of the the total aluminum content of polymethylaluminoxane
0023-1584/04/4502-0176 © 2004 MAIK “Nauka /Interperiodica”

NEW BIS(ARYLIMINO)PYRIDYL COMPLEXES AS COMPONENTS
177
was 4.6–5.6 mol %, and the relative concentration of Al C, 82.70; H, 10.41; N, 6.89. Found (%): C, 82.73; H,
recalculated per trimethylaluminum was 32–36 mol %. 10.45; N, 6.85.
2,4-Dimethyl-6-cyclooctylaniline. Yield 98%,
b.p. 145–147°C at 0.5 mm Hg. C16H25N anal. calcd.
Synthesis of 2,6-Bis(arylimino)pyridyl Ligands
(%): C, 83.06; H, 10.89; N, 6.05. Found (%): C, 83.10;
and Corresponding Complexes
H, 10.92; N, 6.08.
2,6-Bis(arylimino)pyridyl ligands, for example, 2,6-
2,4-Dimethyl-6-cyclododecylaniline. Yield 96%,
bis[1-(2-methyl-6-cycloalkylphenylimino)ethyl]pyri-
b.p. 180–182°C at 0.5 mm Hg. C20H33N anal. calcd.
dines, were synthesized in 80–85% yields by heating
(%): C, 83.56; H, 11.57; N, 4.87. Found (%): C, 83.59;
2-methyl-6-cycloalkylanilines with 2,6-diacetylpyri-
H, 11.60; N, 4.85.
dine in methanol in the presence of catalytic amounts of
2,6-Bis[1-(2-methyl-6-cyclopentylphenylimino)
ethyl]pyridine. Yield 85%, m.p. 170–172°C. C33H39N3
anal. calcd. (%): C, 82.97; H, 8.23; N, 8.80. Found (%):
C, 82.94; H, 8.26; N, 8.84. 1H NMR (CDCl3, CCl4) δ:
8.54 (d, 2 H, Py–Hm), δ 7.96 (t, 1 H, Py–Hp), δ 7.13–6.88
(m, 6 H, Ar–H), 2.26 (s, 6 H, N=C–CH3), 2.03 (s, 6 H,
CAr–Me), 1.78, 1.6 (d, 16 H, cyclopentyl).
formic acid using a modified procedure described
in [11].
Ortho-cycloalkenylanilines necessary for the syn-
thesis of 2,6-bis(arylimino)pyridyl ligands, for exam-
ple, 2-methyl-6-(cyclo-2'-alkenyl)anilines, were syn-
thesized by the reaction of 3-halocycloalkenes with
2-methylaniline by the amino-Claisen rearrangement
of the primarily formed N-(cyclo-2'-alkenyl)-2-methyl-
anilines [12].
Ortho-cycloalkylanilines necessary for the synthe-
sis of 2,6-bis(imino)pyridyl ligands, for example, 2-
methyl-6-(cyclo-2'-alkenyl)anilines, were prepared by
the hydrogenation of the corresponding 2-methyl-6-
cyclo-2'-alkenylanilines in the presence of Raney
nickel under mild conditions with a 95–98% yield.
2,6-Bis[1-(2-methyl-6-cyclohexylphenylimino)
ethyl]pyridine.Yield 81%, m.p. 215–217°C. C35H43N3
anal. calcd. (%): C, 83.12; H, 8.57; N, 8.31. Found (%):
C, 83.15; H, 8.54; N, 8.34. 1H NMR (CDCl3, CCl4), δ:
8.48 (d, 2 H, Py–Hm), δ 7.9 (t, 1 H, Py–Pp), 6.99–6.86
(m, 6 H, Ar–H), δ 2.2 (s, 6 H, N=C–CH3), 1.98 (s, 6 H,
CAr−Me), δ 1.76–1.23 (m, 20 H, cyclohexyl).
2,6-Bis[1-(2-methyl-6-cyclooctylphenylimino)
ethyl]pyridine.Yield 85%, m.p. 140–142°C. C39H51N3
anal. calcd. (%): C, 83.37; H, 9.15; N, 7.48. Found (%):
C, 83.78; H, 9.11; N, 7.45.
2,6-Bis(arylimino)pyridyl complexes of metal
halides, for example, 2,6-bis[1-(2-methyl-6-cycloalky-
lphenylimino)ethyl]pyridineiron(II) chloride, were
synthesized in high yields by the reaction of the
corresponding 2,6-bis(arylimino)pyridyl ligand, for
2.6-Bis[1-(2-methyl-6-cyclododecylphenylimino)
ethyl]pyridine.Yield 83%, m.p. 178–180°C. ë47ç67N3
anal. calcd. (%): C, 83.75; H, 10.02; N, 6.23. Found (%):
C, 83.39; H, 10.04; N, 6.18.
example,
2,6-bis[1-(2-methyl-6-cycloalkylphenyl-
imino)ethyl]pyridine, with FeCl2 · 4ç2é in THF at
room temperature in argon using a modified procedure
described in [11].
2,6-Bis[1-(2,4-dimethyl-6-cyclopentylphenylimino)
ethyl]pyridine.Yield 81%, m.p. 183–185°ë. ë35ç43N3
anal. calcd. (%): C, 83.12; H, 8.57; N, 8.31. Found (%):
2-Methyl-6-cyclopentylaniline.
Yield
98%,
1
b.p. 98–100°C at 0.5 mm Hg. ë12ç17N anal. calcd. (%):
C, 82.23; H, 9.78; N, 7.99. Found (%): C, 82.51; H, 9.77;
N, 7.98.
C, 83.13; H, 8.58; N, 8.30. H NMR (ëDël3, ëël4) δ
8.46 (d, 2 H, Py–Pm), δ 7.86 (t, 1 H, Py–Hp), δ 6.78 (d,
4 H, Ar–H), δ 2.27 (s, 6 H, N=C–CH3), δ 2.19 (s, 6 H,
2-Methyl-6-cyclohexylaniline.
Yield
96%, CAr–Me), 1.93 (s, 6 H, CAr–Me), δ 1.73, 1.56 (d, 16 H,
b.p. 100–102°ë at 0.5 mm Hg. ë13ç19N anal. calcd. (%): cyclopentyl).
C, 82.46; H, 10.12; N, 7.40. Found (%): C, 82.51;
H, 10.15; N, 7.41.
2,6-Bis[1-(2,4-dimethyl-6-cyclohexylphenylimino)
ethyl]pyridine.Yield 82%, m.p. 234–236°C. C37H47N3
anal. calcd. (%): C, 83.25; H, 8.87; N, 7.87. Found (%):
C, 83.27; H, 8.85; N, 7.85. 1H NMR (CDCl3, CCl4), δ:
8.46 (d, 2 H, Py–Hm), 7.88 (t, 1 H, Py–Hp), δ 6.80 (d,
4 H, Ar–H), 2.27 (s, 6 H, N=C–CH3), δ 2.19 (s, 6 H,
CAr–Me), δ 1.94 (s, 6 H, CAr–Me), δ 1.76–1.23 (m, 20 H,
cyclohexyl).
2-Methyl-6-cyclooctylaniline.
Yield
98%,
b.p. 129–130°ë at 0.5 mm Hg. ë15ç23N anal. calcd. (%):
C, 82.89; H, 10.67; N, 6.44. Found (%): C, 82.91;
H, 10.64; N, 6.41.
2-Methyl-6-cyclododecylaniline. Yield 95%,
b.p. 170–172°ë at 0.5 mm Hg. ë19ç31N anal. calcd. (%):
C, 83.45; H, 11.43; N, 5.12. Found (%): C, 83.48;
H, 11.45; N, 5.15.
2,4-Dimethyl-6-cyclopentylaniline. Yield 98%,
b.p. 134–136°ë at 0.5 mm Hg. ë13ç19N anal. calcd. (%):
C, 82.70; H, 10.12; N, 7.40. Found (%): C, 82.48;
H, 10.15; N, 7.41.
2,6-Bis[1-(2,4-dimethyl-6-cyclooctylphenylimino)
ethyl]pyridine.Yield 80%, m.p. 128–130°C. C41H55N3
anal. calcd. (%): C, 83.48; H, 9.40; N, 7.12. Found (%):
C, 83.50; H, 9.43; N, 7.10.
2,6-Bis[1-(2,4-dimethyl-6-cyclododecylphenyl-
imino)ethyl]pyridine. Yield 80%, m.p. 168–169°C.
2,4-Dimethyl-6-cyclohexylaniline. Yield 97%, C49H55N3 anal. calcd. (%): C, 83.82; H, 10.19; N, 5.98.
b.p. 133–135°ë at 0.5 mm Hg. ë14ç21N anal. calcd. (%): Found (%): C, 83.85; H, 10.22; N, 5.95.
KINETICS AND CATALYSIS Vol. 45 No. 2 2004

178
IVANCHEV et al.
Table 1. Characteristics of the structures of the synthesized complexes
Substituents in aryl ring
R2 R3
Catalyst
R1
R4
P-1
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
cyclopentyl
cyclopentyl
cyclopentyl
cyclopentyl
cyclohexyl
cyclohexyl
cyclohexyl
cyclohexyl
cyclooctyl
cyclooctyl
cyclooctyl
cyclododecyl
cyclododecyl
iso-C3H7
H
H
H
P-2
CH3
P-3
CH3
CH3
H
P-4
cyclopentyl
H
H-1
H
H-2
CH3
H
H-3
CH3
CH3
H
H-4
cyclohexyl
H
O-1
H
O-2
CH3
H
O-3
CH3
CH3
H
D-1
CH3
D-3
CH3
CH3
H
Catalyst for comparison*
* According to published data [3].
iso-C3H7
2,6-Bis[1-(2-methyl-6-cyclopentylphenylimino)
2,6-Bis[1-(2,4-dimethyl-6-cyclooctylphenylimino)
chloride. Yield 80%.
ethyl]pyridineiron(II) chloride. Yield 88%. ethylpyridineiron(II)
C33H39Cl2FeN3 anal. calcd. (%): C, 65.57; H, 6.50; Cl, C41H55Cl2FeN3 anal. calcd. (%): C, 68.71; H, 7.74; Cl,
11.73; N, 6.95. Found (%): C, 65.32; H, 6.25; Cl, 11.9; 9.89; N, 5.86. Found (%): C, 68.52; H, 7.51; Cl, 9.99;
N, 6.51.
N, 5.68.
2,6-Bis[1-(2,4-dimethyl-6-cyclododecylphenyl-
imino)ethyl]pyridineiron(II) chloride. Yield 83%.
C49H71Cl2FeN3 anal. calcd. (%): C, 71.00; H, 8.63; Cl,
8.55; N, 5.07. Found (%): C, 70.89; H, 8.50; Cl, 8.86;
N, 4.91.
Designations and compositions of the synthesized
bis(arylimino)pyridyliron(II) chloride complexes are
presented in Table 1.
2,6-Bis[1-(2-methyl-6-cyclohexylphenylimino)
ethyl]pyridineiron(II) chloride. Yield 87%.
C35H43Cl2FeN3 anal. calcd. (%): C, 66.46; H, 6.85; Cl,
11.21; N, 6.64. Found (%): C, 66.24; H, 6.75; Cl, 11.45;
N, 6.47.
2,6-Bis[1-(2-methyl-6-cyclooctylphenylimino)
ethyl]pyridineiron(II)
C35H51Cl2FeN3 anal. calcd. (%): C, 68.03; H, 7.47; Cl,
10.30; N, 6.10. Found (%): C, 67.88; H, 7.37; Cl, 10.53;
N, 6.01.
chloride.
Yield
86%.
Ethylene Polymerization
Ethylene was polymerized in a stainless steel reac-
tor equipped with a demountable jacket and a propeller
mixer with a magnetic driving gear operating at pres-
sures below 0.6 MPa and temperatures from 30 to
80°ë. The pressure in the reactor was maintained auto-
matically, and the temperature regime was controlled
by a water supply (at the corresponding temperature)
from an ultrathermostat into the reactor jacket.
Before polymerization, the reactor was evacuated to
a residual pressure of 1 × 10–1 mm Hg at 150–170°ë for
1 h along with triple purging with dry argon (moisture
content lower than 10 ppm).
2,6-Bis[1-(2-methyl-6-cyclododecylphenylimino)
ethyl]pyridineiron(II)
C47H67Cl2FeN3 anal. calcd. (%): C, 70.49; H, 8.43; Cl,
8.85; N, 5.25. Found (%): C, 70.21; H, 8.24; Cl, 9.03;
N, 6.48.
chloride. Yield
88%.
2,6-Bis[1-(2,4-dimethyl-6-cyclopentylphenylimino)
ethyl]pyridineiron(II)
C35H43Cl2FeN3 anal. calcd. (%): C, 66.46; H, 6.85; Cl,
11.21; H, 6.64. Found (%): C, 66.23; H, 6.76; Cl, 11.43;
N, 5.08.
chloride. Yield
85%.
2,6-Bis[1-(2,4-dimethyl-6-cyclohexylphenylimino)
After the cooling of the reactor to room temperature,
ethyl]pyridineiron(II)
chloride. Yield
88%, toluene and components of the catalytic system were
C37H47Cl2FeN3 anal. calcd. (%): C, 67.28; H, 7.17; Cl, loaded by medical syringes through a loading outlet in
10.73; N, 6.36. Found (%): C, 67.04; H, 7.00; Cl, 10.95; an argon counterflow. The reaction mixture was satu-
N, 6.18.
rated with ethylene and simultaneously heated to the
KINETICS AND CATALYSIS Vol. 45 No. 2 2004

NEW BIS(ARYLIMINO)PYRIDYL COMPLEXES AS COMPONENTS
179
w × 10–3, (kg of PE)/((mol of Fe) min)
A × 10–3, (kg PE)/((mol Fe) MPa h)
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
120
2
5
100
80
60
40
20
0
1
4
3
3
2
1
20
40
60
80
Polymerization temperature, °C
0
10
20
30
40
50
60
Time, min
Fig. 1. Changes in the polymerization rate with time of the
Fig. 2. Plots of the activity of the 2,6-bis(arylimino)pyridy-
liron(II) chloride complexes vs. temperature of ethylene
polymerization: (1) P-3, (2) H-3, (3) O-3, (4) D-3, and
(5) catalyst for comparison (see Table 1). For experimental
conditions, see Table 2.
reaction at 70°ë (P
= 0.3 MPa, methylaluminox-
ethylene
–6
ane/Fe = 1500 : 1 (mol/mol)): 1, P-3, n = 2.5 × 10 mol;
Fe
–6
–6
2, H-3, n = 2.5 × 10 mol; 3, D-3, n = 0.9 × 10 mol.
Fe
Fe
ture of the melting beginning (Tb) and end (Te) and the
position of the maximum of the melting end (Tm) were
determined from the thermograms.
operating temperature. The ethylene pressure was
increased to the calculated value, which was automati-
cally maintained during the whole experiment.
The specified regime of the reactor was achieved for
~1 min, after which the polymerization rate was mea-
sured.
After 60 min, the reaction was stopped by adding
isopropyl alcohol to the reaction medium. The liquid
phase was separated on a Büchner funnel, and the
resulting polymer was dried at 60°ë in a vacuum until
it showed a constant weight.
The specific melting peak maximum (ƍm) was
determined as the surface area restricted by the curve of
the melting peak and basic line connecting the Tb and Te
points.
RESULTS AND DISCUSSION
The results of ethylene polymerization on the syn-
thesized catalysts are presented in Table 2.
Procedure for Determination of Properties
of Prepared Polyethylenes
The activities of the synthesized catalytic systems
are higher than that of the iron halide complex of 2,6-
bis[(2,4-diisopropylarylimino)ethyl]pyridine [3] at
temperatures >50°ë. Moreover, the activity decreases
with temperature only in the case of the cyclopentyl
substituents, whereas for the cyclohexyl, cyclooctyl,
and cyclododecyl substituents the polymerization rate
remains unchanged or increases (the latter is especially
the case for the cyclododecyl substituents: samples 21−24
in Table 2).
The melt flow index was determined in order to esti-
mate the molecular weights of the polyethylene sam-
ples. It was determined on a standard extrusion-type
plastometer at 190°ë and loading of 5 kg.
The polymer density was determined by the method
of flotation of molded samples with a thickness of
1 mm in an aqueous–alcohol solution at 20 ± 1°ë.
The structures of the polyethylenes were analyzed
by FTIR spectroscopy on a FTIR-8300 Shimadzu spec-
trometer.
The ethylene polymerization rate at 70°C in the
presence of the bis(arylimino)pyridineiron(II) chloride
The specific heats of phase transitions and charac- complexes studied reaches the maximum value
teristic temperatures were measured on a DSC-60 dif- 5−10 min after the beginning of the experiment fol-
ferential scanning calorimeter (Shimadzu) with a heat- lowed by a decrease, which is least pronounced for
ing rate of 10°C/min using a sample of 7 mg. The sample D-3 (Fig. 1). This specific feature is important
results were presented as thermograms in the specific for the selection of the optimum ligands of the catalytic
thermal flow–temperature coordinates. The tempera- complex for polymerization in view of the require-
KINETICS AND CATALYSIS Vol. 45 No. 2 2004

180
IVANCHEV et al.
Table 2. Ethylene polymerization in the presence of new bis(arylimino)pyridyliron(II) chloride complexes
Amount of catalyst
precursor, µmol
Polymerization
temperature, °C
A × 10–3,
(kg of PE)/((mol of Fe) MPa h)
No.
Catalyst
Yield, g
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
P-2
P-2
P-2
P-2
H-2
H-2
H-2
H-2
O-2
O-2
P-3
P-3
P-3
H-3
H-3
H-3
H-3
O-3
O-3
O-3
D-3
D-3
D-3
D-3
P-4
P-4
P-4
H-4
H-4
H-4
H-4
1.25
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.0
2.0
2.5
2.5
2.5
2.5
1.25
1.25
1.25
2.5
2.0
2.0
0.9
0.9
0.9
0.9
2.5
2.5
2.5
2.5
2.5
2.5
2.5
30
50
70
80
30
50
70
80
70
80
50
70
80
30
50
70
80
50
70
80
30
50
70
80
50
70
80
30
50
70
80
12.17
22.02
17.83
4.85
12.28
23.92
26.24
25.56
23.2
19.5
26.5
20.92
7.68
13.5
11.38
15.93
13.13
24.5
27.36
26.6
10.8
13.8
17.5
20.7
33.9
29.4
23.8
6.5
16.4
31.9
35.0
34.1
38.7
32.5
35.3
27.9
10.2
18.0
30.3
42.5
35.0
32.7
45.6
44.3
40.0
51.0
64.8
76.7
32.2
27.6
18.8
15.2
15.5
3.5
24.13
20.7
14.13
11.4
11.6
2.6
0.81
1.1
Note: Duration of experiment 1 h, solvent toluene (50 ml), methylaluminoxane/Fe = 1500 : 1. A is activity.
ments regarding the molecular weight of the resulting shows that the use of these systems makes it possible to
polyethylene.
obtain only oligomeric products. The character of the
changes in the polymerization rate on these samples is
the same as that for their analogs (H-2, D-2, and oth-
ers).
The kinetic curves presented in Fig. 2 confirm that, con-
trary to the previously described [3] catalytic system based
on 2,6-bis[(2,4-diisopropylarylimino)ethyl]pyridine
(Table 1), which rapidly loses activity with a tempera-
ture increase (curve 2), our new 2,6-
bis(arylimino)pyridineiron(II) chloride complexes (in
particular, those with H-3 and O-3) at 70°C are more
active than at 50°C, and the activity continues to
increase with an increase in polymerization tempera-
ture to 80°C (curve 4).
The presented results suggest that
(1) When cycloaliphatic substituents in combination
with a methyl group are introduced into the ortho posi-
tion of the arylimine group of the iron halide complexes
of the catalytic systems, the activity maximum shifts
toward higher temperatures;
Our study of ethylene polymerization in the 30–
(2) The temperature maximum depends on the num-
80°C temperature interval on the H-1, O-1, and D-1 cat- ber of CH2 groups in the cycloalkyl substituent: it is
alyst precursors in the presence of methylaluminoxane approximately 50°C for cyclopentyl and 70°C for
KINETICS AND CATALYSIS Vol. 45 No. 2 2004

NEW BIS(ARYLIMINO)PYRIDYL COMPLEXES AS COMPONENTS
181
Table 3. Characteristics of polyethylenes obtained on new bis(imino)pyridyliron(II) chloride complexes
Polymerization
temperature, °C
Flow index
of melt*, g/10 min
No.
Catalyst
Density, kg/m3
Tm, °C
∆Hm, J/g
1
2
P-2
P-2
P-2
P-2
H-2
H-2
H-2
H-2
H-2
H-2
P-3
P-3
P-3
H-3
H-3
H-3
H-3
H-3
H-3
H-3
D-3
D-3
D-3
D-3
P-4
P-4
P-4
H-4
H-4
H-4
30
50
70
80
30
50
70
80
70
80
50
70
80
30
50
70
80
50
70
80
30
50
70
80
50
70
80
30
50
70
2.3
0.83
65.0
>4000
0.53
71.0
6.0
–
–
–
–
–
–
3
–
–
–
–
4
120.0
–
–
5
972.5
970.0
–
–
202.0
209.0
–
6
133.0
138.0
–
7
8
11.0
0.43
5.9
–
9
972.0
–
133.3
133.3
132.0
–
197.0
220.0
–
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
1.0
–
42.0
>180
3.8
972.0
–
–
–
–
972.6
130.0
–
0.33
44.0
94.0
0.98
0.98
>101
4.4
–
–
–
–
–
–
971.0
–
–
970.0
133.3
134.7
–
–
–
–
968.0
–
11.4
9.3
–
133.0
135.0
134.0
–
195.0
–
205
160.0
0.62
5.6
–
222.0
972.3
–
–
–
–
–
–
970.0
–
16.0
115.0
480.0
760.0
–
–
–
–
–
130.0
132.0
120.0
Note: For numbering and conditions of polyethylene preparation, see Table 2.
* Loading 5 kg.
cyclohexyl and cyclooctyl, while for cyclododecyl the the second ortho and para positions) along with close
polymerization rate does not decrease even at 80°C;
results on the dynamics of ethylene absorption pro-
duces only oligomeric products and, hence, the experi-
mental data for P-1, H-1, O-1, and D-1 are not included
in Table 2.
(3) The introduction of two cycloalkyl substituents
into the ortho position of arylimine substantially
decreases the polymerization rate and molecular weight
of the product, that is, the melt flow index of the formed
polymers increases. This means that the steric effects of the para position of the arylimine group are insufficient
two cycloaliphatic substituents favor a decrease in the for a substantiated discussion of this effect.
chain propagation rate constant and an increase in the
probability of β-hydride chain transfer;
(4) The presence of only one cycloaliphatic substit- is inversely proportional to the molecular weight) and
uent in the ortho position (without any substituents in density. The highest molecular weights were obtained
Available data on the influence of the substituent in
The molecular characteristics of the polyethylenes
were studied by measuring the melt flow index (which
KINETICS AND CATALYSIS Vol. 45 No. 2 2004

182
IVANCHEV et al.
in the catalytic systems at 30–50°ë (Table 3), and the
melt flow index increases in a regular manner with an
increase in the polymerization temperature. However,
in many cases, polymers appropriate from the view-
point of the molecular weight are formed at 70–80°ë
(Table 3, samples 7, 9, 10, and 19). Note that the poly-
ethylenes obtained at 35°ë in the presence of the cata-
lytic system based on the 2,6-bis[(2,4-dimethylphe-
nylimino)ethyl]pyridyliron(II) chloride complexes and
methylaluminoxane [13] are characterized by a melt
flow index equal to 13.6 g/10 min at a loading of
2.16 kg, that is, the molecular weight is much lower
than that for polyethylenes synthesized on our cata-
lysts.
ACKNOWLEDGMENTS
This work was supported by the Siberian Division
of the Russian Academy of Sciences in the framework
of the Complex Integration Project no. 16.
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groups per 100 carbon atoms determined by IR spec-
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their thermal properties (see Table 3).
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The main result is that the modification of the 2,6-
bis(arylimino)pyridyliron(II) chloride complexes by
the introduction of cycloaliphatic substituents into the
ortho position of the aryl groups substantially enlarges
the temperature interval of efficient use of the related
catalysts for ethylene polymerization under homoge-
neous conditions. This considerably enhances the
potential of using the new catalysts for polyethylene
production technologies.
KINETICS AND CATALYSIS Vol. 45 No. 2 2004