Catalytic activity of new nickel(II) formazanates in ethylene oligomerization

Article abstract of DOI:10.1134/S0965544112010124

Thirteen mono-and three bisformazans containing one system of azahydrazone bonds have been synthesized, as well as mono-and binuclear complexes on their basis. The kinetic features of ethylene oligomerization in the presence of catalytic systems on the basis of AlEtCl₂-activated Ni(II) formazanates differing in composition and structure have been studied. The structures of the mono-and binuclear complexes differ by substituents in the formazan ligand, which have an effect on the activity of the systems and the product composition. The catalytic activity of the binuclear complexes is several times below that of mononuclear Ni(II) formazanates. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S0965544112010124

ISSN 0965ꢀ5441, Petroleum Chemistry, 2012, Vol. 52, No. 1, pp. 28–34. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.V. Zaidman, I.I. Khasbiullin, G.P. Belov, I.G. Pervova, I.N. Lipunov, 2012, published in Neftekhimiya, 2012, Vol. 52, No. 1, pp. 31–38.
Catalytic Activity of New Nickel(II) Formazanates
in Ethylene Oligomerization
A. V. Zaidmana, I. I. Khasbiullinb, G. P. Belovc, I. G. Pervovaa, and I. N. Lipunova
aUral State Forest Engineering University, Yekaterinburg, Russia
eꢀmail: Zaidman@yandex.ru
bKazan State Technological University, Kazan, Russia
eꢀmail: khailnaz@yandex.ru
cInstitute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, Russia
eꢀmail: gbelov@cat.icp.ac.ru
Received May 12, 2011
Abstract—Thirteen monoꢀ and three bisformazans containing one system of azahydrazone bonds have been
synthesized, as well as monoꢀ and binuclear complexes on their basis. The kinetic features of ethylene oligoꢀ
merization in the presence of catalytic systems on the basis of AlEtCl2ꢀactivated Ni(II) formazanates differꢀ
ing in composition and structure have been studied. The structures of the monoꢀ and binuclear complexes
differ by substituents in the formazan ligand, which have an effect on the activity of the systems and the prodꢀ
uct composition. The catalytic activity of the binuclear complexes is several times below that of mononuclear
Ni(II) formazanates.
DOI: 10.1134/S0965544112010124
Creation of new highꢀperformance catalytic sysꢀ report in this paper data on the influence of the comꢀ
tems for oligomerization of
α
ꢀolefins remains an position of the inner coordination sphere and the
important task, since the demand for new oligomeric number of active metal centers on the catalytic activity
materials does not pass and the progress in controlling of these complexes in the ethylene oligomerization
the structure and properties of oligomers was always reaction.
associated with the development of catalysts with new
structure [1]. Metal complexes of Ni(II) with “nitroꢀ
genꢀskeleton” organic ligands in combination with
EXPERIMENTAL
organoaluminum compounds showed themselves to
advantage as such catalytic systems [2].
Ethylene Oligomerization
The reaction was carried out in toluene for 1 h in a
stainless steel reactor of 0.2 l volume equipped with a
magnetic stirrer and a gauge for controlling the ethylꢀ
ene pressure. The cleaned, inert gasꢀpurged reactor
was evacuated for 1–2 h at 353 K. A calculated
amount of solvent and ethylene were fed to the reactor
heated to a desired temperature, and then solutions of
the catalyst components Ni(II) formazanate and ethꢀ
ylaluminum dichloride were successively injected with
a metal syringe (Schlenk technique). Toluene was preꢀ
liminary purified according to the standard procedure
by distillation over 4–5 Å molecular sieves. Ethylene
Formazans (azahydrazones) [3], polydentate cheꢀ
late ligands, have already been known in many areas
of practical application including catalysis. Wide
variability of substituents in formazan molecules and
relative ease of their synthesis make it possible to
study the influence of the fine ligand structure on the
catalytic activity of metal complexes in ethylene oliꢀ
gomerization.
Earlier [4] we have studied the influence of location
of chlorineꢀcontaining substituents in formazan
ligands, temperature, pressure, and Al/Ni molar ratio
on the reaction kinetics and the product composition
of ethylene oligomerization in the presence of a cataꢀ
lytic system based on Ni(II) formazanates and
EtAlCl2. It was shown that effective metal complex
systems can be obtained by varying the ligand compoꢀ
sition and structure.
was of 99.9 wt % purity. The cocatalyst AlC2H5Cl2
taken as a 73 wt % solution in benzene, was not addiꢀ
tionally purified.
,
Product Analysis
This study is in continuation of our investigation
The products were determined chromatographiꢀ
into the influence of the nature of substituents in the cally on a Chromꢀ5 chromatograph: a TRꢀ5 MS capꢀ
structure of Ni(II) formazanates on their catalytic illary column (manufactured by Thermo Fisher Sciꢀ
activity in ethylene oligomerization. In addition, we entific) of 30 m
∅
0.25 mm in size with 5% pheꢀ
28

CATALYTIC ACTIVITY OF NEW NICKEL(II) FORMAZANATES
29
nylpolysylphenylene–siloxane inner film of 0.25
μm
Synthesis of formazan 16. A diazonium salt soluꢀ
thickness; the carrier gas was argon, with a flameꢀionꢀ tion prepared from 0.31 g of bisaminobissulfide
ization detector. The elemental analysis was carried (1.12 mmol) dissolved in 5 ml of concentrated HCl
and 0.15 g (2.2 mmol) of sodium nitrite in 5 ml of
water was slowly added to a solution 0.53 g (2.2 mmol)
of 1ꢀ(benzothiazolꢀ2ꢀyl)ꢀ3ꢀpyridinylhydrazone in
25 ml of isopropanol. After the addition of the diazoꢀ
solution, the resulting mixture was held for additional
20 min in an ultrasonic bath, a 2 N NaOH solution was
added with vigorous stirring until pH ~ 10, and the
mixture was left to stay for 40 min. A concentrated
hydrochloric acid solution was added to the resultant
mixture to pH ~ 7, and the solution was held at room
temperature for 2–3 h. The precipitate was filtered off,
washed with water, dried in air, and recrystallized from
ethanol.
out on a PerkinꢀElmer PE2400SII automated CHN
analyzer. The proceeding of the reaction was moniꢀ
tored and synthesized Ni(II) complexes were identiꢀ
fied by TLC on Silufolꢀ254 plates (acetone : hexane =
1 : 1 blend as an eluent). Electronic absorption spectra
in the visible and nearꢀUV regions were recorded on a
Shimadzu UVꢀ2100 spectrophotometer. The magꢀ
netic characteristics were measured by the relative
Faraday technique at temperatures in the range of
288–293 K [5] at the Institute of Solid State Physics,
Ural Branch, Russian Academy of Sciences (Yekaterꢀ
inburg).
Formazans 14 and 15 were synthesized according
to the same procedure.
Synthesis of metal complex I was conducted as
described in [6]. A solution of Ni(CH3COO)2 · 4H2O
(0.85 mmol) in 10 ml of water was added dropwise
with continuous stirring to a solution of formazan 1
Synthesis of Ligands and Metal Complexes
Synthesis of monoformazan 1. A diazonium salt
solution prepared from 2.30 g of
pꢀchloroaniline
(18.04 mmol) dissolved in 5 ml of concentrated HCl
and 1.24 g (18.04 mmol) of sodium nitrite in 5 ml of
water was slowly added to a solution of 3.45 g
(18.04 mmol) of the corresponding hydrazone in
(0.85 ml) in 50 ml of acetone at 40
5°С. The resultꢀ
ing mixture was stirred for 30 min and then evaporated
to 15 ml. The precipitate was filtered off, washed sucꢀ
50 ml of DMF. After the addition of the whole amount cessively with warm distilled water and isopropanol,
of the diazosolution, the resulting mixture was held for and dried in air.
additional 20 min, then a 2 N NaOH solution was
added with vigorous stirring until pH ~ 9, and the mixꢀ
ture was left to stay for 30 min. A concentrated acetic
acid solution was added to the resultant mixture to
have pH ~ 7, and the mixture was held at room temꢀ
perature for 10–15 h. The precipitate was filtered off,
Complexes II
–XVI were synthesized according to
the same procedure.
RESULTS AND DISCUSSION
Monoformazans 1–10 containing one system of
washed with water, dried in air, and recrystallized from azahydrazone bonds and mononuclear complexes on
acetone. Formazans 2–13 were synthesized according their basis (
) were synthesized according to
I–X
to the same procedure.
scheme 1:
R1
N
S
N
N
N
R2
R3
R5
R2
R3
R5
N
N
N
S
+
N2
R
NH
N
+
R4
N
N
R4
NH
N
Ni
S
R
N
N
N
CH
N
R1
S
R1
N
I–X
R1
1–10
Scheme 1. Synthesis of formazans and their complexes
.
The substituents in the synthesized compounds is ligands [7], the coordination unit NiN6 has the
specified in Table 1. Table 2 gives the main characterꢀ
istics of the synthesized formazans and Ni(II) comꢀ
plexes on their basis.
octahedral form, which can be noticeably distorted
by substituents on the phenyl ring at N1 according
to [8]. Therefore, in was assumed that metal comꢀ
plexes I–X have the same structure of the coordinaꢀ
According to Xꢀray analysis data for a variety of
mononuclear Ni(II) complexes with formazan tion unit.
PETROLEUM CHEMISTRY Vol. 52
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30
ZAIDMAN et al.
Table 1. Structure of synthesized formazan ligands
Formazan no.
R1
R2
R3
R4
R5
Metal complex no.
1
2
3
4
5
6
7
8
9
CH3
C6H5
CH3
H
Cl
Cl
Cl
Br
H
H
H
H
H
H
H
H
H
H
H
F
Cl
H
Cl
H
H
Br
H
H
H
H
Cl
H
H
H
H
H
I
II
III
IV
V
VI
VII
VIII
IX
C6H4ꢀ4ꢀOCH3
C2H5
C7H15
CH2Br
C6H4ꢀ4ꢀOCH3
C3H7
F
F
F
10
11
12
13
14
15
16
C6H3ꢀ2ꢀOHꢀ5ꢀBr
CH(CH3)2
C4H9
H
F
F
H
NO2
H
H
H
NO2
H
SO3H
H
H
X
XI
OH
OH
OH
H
H
H
H
H
H
H
H
H
XII
XIII
XIV
XV
XVI
CH3
C6H5 (n = 1)
C6H5 (
C5H4N (
n
n
= 2)
= 1)
H
H
H
All metal complexes synthesized in this work were moiety or a change in geometric size of the peripheral
tested for catalytic activity in ethylene oligomerizaꢀ substituents in the C3 position. In the previous paper
tion. According to GC data (Table 3) the products [4], we noted that the presence of a relatively small
form a mixture consisting of higher olefins. The alkyl substituent in the C3 position of the formazan
amount of ꢀolefins, butaneꢀ1 and hexaneꢀ1, in the ligand is preferred to the presence of a bulky aryl moiꢀ
α
mixture is 30–50%.
ety. Thus, the activity of formazanate II (phenyl subꢀ
stituent at C3) is 25% lower in comparison with comꢀ
Among Ni(II) metal complexes I–IV, compounds
plex
containing the bulky
the C3 position of the formazan chain decreases by
more than a factor of 4 compared with complex III
I
and the catalytic activity of metal chelate IV
III and
I synthesized from chlorosubstituted formaꢀ
pꢀmethoxyphenyl substituent in
zans containing the methyl group at the C3 atom
exhibit a high catalytic activity. Among all chloropheꢀ
nylꢀcontaining Ni(II) formazanates, compound III in
which chlorine atoms simultaneously present in the
.
At the same time, it was noted that it is the presence
orthoꢀ and paraꢀpositions on the phenyl ring at N1 of substituents in the aryl moiety at N1 for bromineꢀ
(Fig. 1a) has the highest activity. In the case of metal containing complexes VII that plays the determining
complexes and II synthesized from monoꢀchloroꢀ role in the change in catalyst activity (Fig. 2a). For
V–
I
substituted formazans, it is difficult to determine what example, the substitution of bromine into the
factor has a greater effect on the change in activity: C3 position of VII decreases the activity by a factor of
stereoposition of chlorine substituent in the phenyl 2–4 as compared with bromophenylꢀsubstituted comꢀ
(b)
(a)
VIII
IX
X
I
3.5
3.5
3.0
2.5
2.0
1.5
1.0
0.5
3.5
3.0
2.5
2.0
1.5
1.0
0.5
II
III
IV
0
10
20
30
Time, min
40
50
60
0
10
20
30
40
50
60
Time, min
Fig. 1. Ethylene consumption rate curves during oligomerization in the presence of catalytic systems based on Ni(II) formazanꢀ
ates (a) IV and (b) VIII
I–
–X.
PETROLEUM CHEMISTRY Vol. 52
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CATALYTIC ACTIVITY OF NEW NICKEL(II) FORMAZANATES
Table 2. Characterization of benzothiazolylformazans and their Ni(II) complexes
Found, %
31
Calculated, %
H
No.
Mp,
°
C
Empirical formula
MW, g/mol
C
H
N
C
N
1
I
174
54.74
50.31
61.42
57.30
49.40
45.92
55.34
52.12
49.50
46.23
55.72
52.01
48.20
44.87
59.63
55.86
56.80
52.70
49.31
45.80
53.21
46.55
54.43
47.60
46.12
40.55
62.71
59.14
63.26
59.60
59.65
55.97
3.68
3.15
3.65
3.32
3.06
2.69
3.36
2.98
3.68
3.21
5.31
4.86
3.31
2.89
3.68
3.21
4.23
3.78
2.56
2.50
4.36
3.39
4.72
3.74
3.40
2.68
4.32
4.02
4.25
3.96
3.78
3.61
21.20 C15H12N5ClS
329.81
716.44
391.89
840.46
364.26
785.20
456.36
969.40
388.29
833.26
458.43
973.54
374.26
805.20
423.45
903.58
359.40
775.48
488.32
1033.32
384.42
441.13
398.45
455.16
391.43
448.11
804.98
1723.52
819.01
1751.58
806.97
1727.48
54.63
50.29
61.30
57.16
49.46
45.89
55.27
52.03
49.49
46.12
55.02
51.81
48.14
44.75
59.57
55.82
56.81
52.66
49.19
45.49
53.12
46.28
54.26
47.50
46.03
40.20
62.66
58.52
63.06
58.95
59.53
55.61
3.67
3.10
3.60
3.12
3.04
2.57
3.31
2.92
3.63
3.15
5.28
4.77
3.23
2.76
3.57
3.13
4.21
3.65
2.48
2.15
4.20
3.21
4.55
3.55
3.35
2.48
4.02
3.52
4.19
3.68
3.75
3.27
21.23
19.56
17.87
16.67
19.23
17.84
15.35
14.45
18.04
16.81
15.28
14.39
18.71
17.40
16.54
15.50
19.49
18.07
14.34
13.56
21.86
19.06
21.09
18.46
17.89
15.63
17.40
16.25
17.11
16.00
20.83
19.46
195
212
263
156
205
183
208
197
231
182
238
208
250
143
186
157
205
168
224
190
201
184
219
175
196
232
240
215
244
180
246
19.67 C30H22N10NiCl2S2
17.96 C20H14N5ClS
2
II
16.80 C40H26N10NiCl2S2
19.20 C15H11N5Cl2S
17.90 C30H20N10NiCl4S2
15.48 C21H15N5Cl2SO
14.63 C42H28N10NiCl4S2O2
18.50 C16H14N5BrS
3
III
4
IV
5
V
16.87 C32H26N10NiBr2S2
15.40 C21H24N5BrS
6
VI
7
14.55 C42H46N10NiBr2S2
18.84 C15H12N5BrS
VII
8
17.60 C30H22N10NiBr2S2
16.70 C21H15N5F2SO
15.64 C42H28N10NiF4S2O2
19.57 C17H15N5F2S
VIII
9
IX
10
X
18.22 C34H28N10NiF4S2
14.59 C20H12N5BrF2SO
14.05 C40H22N10NiBr2F4S2O2
21.97 C17H16N6SO3
11
XI
12
XII
13
XIII
14
XIV
15
XV
16
XVI
19.28 C17H14N6NiSO3
21.23 C18H18N6SO3
18.68 C18H16N6NiSO3
17.82 C15H13N5S2O4
15.50 C15H11N5NiS2O4
17.56 C42H32N10S4
16.70 C84H60N20Ni2S8
17.21 C43H34N10S4
16.52 C86H64N20Ni2S8
20.92 C40H30N12S4
19.80 C80H56N24Ni2S8
PETROLEUM CHEMISTRY Vol. 52
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32
ZAIDMAN et al.
Table 3. Catalytic activity of Ni(II) formazanates in ethylene oligomerization reaction (Vreac.mix = 60 ml; T = 80°C, cocatꢀ
alyst, AlC2H5Cl2;
heptane)
p
ethylene = 0.4 MPa;
C
Ni = 3
×
10–4 mol/l, AlC2H5Cl2 : nickel chelate molar ratio = 100 : 1; solvent,
nꢀ
Olefin composition, wt %
Metal complex no.
L : M
Activity, kg/(gNi h)
Σ
C4 (C4ꢀ1)
Σ
C6 (C4ꢀ1)
Σ
C8
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
XIII
XIV
XV
XVI
L2Ni
L2Ni
L2Ni
L2Ni
L2Ni
L2Ni
L2Ni
L2Ni
L2Ni
L2Ni
LNi
LNi
LNi
L2Ni2
L2Ni2
L2Ni2
21.1
16.5
26.5
7.3
11.0
23.8
5.5
7.4
33.8
8.2
11.1
5.5
4.6
8.2
7.4
15.7
1
2.1
3
41.3
18.6
72
50
5.4
71
72
63
73 (41)
88.4 (48)
39.6 (36)
60 (40)
27.5 (31)
55.8 (52)
16 (38)
27 (31)
39.4 (48)
15 (41)
12 (35)
14 (43)
21 (30)
25 (24)
19 (21)
14 (32)
11.3 (44)
10.6 (35)
58.3 (49)
37 (51)
31.3 (42)
25.6 (54)
12 (41)
23 (34)
55.2 (31)
14 (28)
16 (34)
23 (34)
32 (39)
31 (30)
28 (25)
30 (31)
47
46
53
46
9.2
plexes
V–VI (Table 3). The greatest activity in this reacꢀ (PE) was noted by Ivancheva et al. [10], who used pheꢀ
noxyimine complexes of titanium as an example to
show that replacement of the methyl substituent in the
paraꢀposition of the phenoxy group by the tertꢀbutyl
radical decreases the activity by a factor of 2.5. But even
in this case, the cited authors admit the existence of the
optimal volume of substituents above which their stimꢀ
ulating influence on the activity of the catalytic system
decreases or is absent at all. Figure 1b depicts the
obtained kinetic curves of ethylene oligomerization in
tion catalyzed by fluorosubstituted complexes VIII
–X
was displayed by compound IX. This is believed [9] to be
due to the electronꢀdonating effect of fluorineꢀcontainꢀ
ing substituents, which increase the electrophilicity of
the nickel center thus, in turn, decreasing the activation
energy of ethylene insertion. However, the introduction
of rather bulky pꢀmethoxyphenyl substituent in the
C3 position of fluorineꢀcontaining ligand (VIII), as in
the case of chlorineꢀcontaining complex IV, results in a
sharp decrease in activity of the catalytic system. A simꢀ
ilar influence of peripheral substituents on the activity
the presence of metal complexes VIII
–X.
The presence of fluorine atoms in the phenyl subꢀ
and molecular weight (MW) of product polyethylenes stituent at N1 along with the 2ꢀhydroxyꢀ5ꢀbromopheꢀ
V
VI
VII
(a)
3.0
2.5
2.0
1.5
1.0
0.5
(b)
IX
XII
XIII
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
10
20
30
Time, min
40
50
60
0
10
20
30
Time, min
40
50
60
Fig. 2. Ethylene consumption rate curves during oligomerization in the presence of catalytic systems based on Ni(II) formazanꢀ
ates (a) VII and (b) XI XIII
V–
–
.
PETROLEUM CHEMISTRY Vol. 52
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CATALYTIC ACTIVITY OF NEW NICKEL(II) FORMAZANATES
33
nyl substituent in the C3 position facilitates an tronically flexible ligands based on
Nꢀ(
oꢀphenoxypheꢀ
increase in activity of the catalytic system based on nyl)pyridaldimine derivatives. The catalytic activity of
metal complex as compared with VII. It may be these complexes in ethylene oligomerization at MAO
X
assumed that the stereoposition of substituents on the activation in toluene was found to be very low or
phenyl group at N1 of the formazan chain plays a sigꢀ absent altogether.
nificant role in varying the activity of the complex in
It is known [12] that compounds with different
comparison with the steric volume of substituents in
amounts of active metal sites can be highly efficient
the C3 position.
catalysts in ethylene oligomerization. The denticity of
formazan ligands makes it possible to synthesize biꢀ
and polynuclear complexes having higher activity in
this reaction. The interest in binuclear complexes
As it was stated previously [3] the introduction of
hydroxyl group in the orthoꢀposition of the phenyl
substituent of ligands 11–13 favors the formation of
mononuclear LNi complexes XI
–XIII with the
based on novel bisformazans is also due to the fact that
besides the properties inherent in mononuclear comꢀ
plexes they can exhibit unique catalytic behavior due
to the presence of several active centers. According to
[13], it is expected that binuclear complexes are more
active as the greater steric loading of the molecule
must more effectively prevent the contacts of active
centers with each other. The use of binuclear comꢀ
plexes for oligomerization makes it possible to obtain
absolutely new polymeric materials (that cannot be
obtained on mononuclear analogues) owing to the
cooperative effect of different active centers [14],
which is observed only in the case of olefin polymerꢀ
ization on binuclear metallocenes [15].
NiN3O coordination unit.
R
O
Ni
N
N
N
N
S
N
R1
Judging from the structure of metal complexes, it
might be expected that they would exhibit a high cataꢀ
lytic activity due to easy accessibility of the metal site
to substrate. However, the results of the experiments
showed that most mononuclear Ni(II) formazanate
complexes exhibited the lowest activity (Fig. 2b). This
Bisligands 14–16 and binuclear Ni(II) complexes
fact is consistent with published data [11] on structurꢀ on their basis (XIV
–XVI) were synthesized according
ally close Ni(II) complexes with unsymmetrical elecꢀ to the scheme 2:
14–16
N2
N2
S
n
S
S
S
n
N
S
N N
+
N2
N N
+
N2
NH
N
1R
R1
N NH
HN N
CH
S
N
S
N
R1
R1
R1
S
n
S
N
N
N
N
N
N
S
S
N
N
N
N
Ni
Ni
N
S
N
S
N
N
N
N
N
N
N
N
S
S
n
R1
R1
Scheme 2.
PETROLEUM CHEMISTRY Vol. 52
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34
ZAIDMAN et al.
XV
XIV
XVI
influence on the activity of the catalytic complex and
0.6
0.5
0.4
0.3
0.2
0.1
the product composition. The steric volume of periphꢀ
eral substituents in the C3 position can alter the cataꢀ
lytic activity of the system. In order to produce highly
efficient catalysts on the basis of binuclear complexes
containing bisformazan ligands, it is necessary to conꢀ
tinue studies on the synthesis of ligands with different
modes of conjugation of the formazan fragments in the
molecule and to subsequently examine their complexes
in the ethylene oligomerization reaction.
ACKNOWLEDGMENTS
0
10
20
30
40
50
60
This work was supported by the Russian Foundaꢀ
tion for Basic Research, project no. 10ꢀ03ꢀ90726ꢀ
mob_st.
Time, min
Fig. 3. Ethylene consumption rate curves during oligomerꢀ
ization in the presence of catalytic systems based on Ni(II)
formazanates XIV–XVI.
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PETROLEUM CHEMISTRY Vol. 52
No. 1
2012