Synthesis, structure, and catalytic properties of iron complexes with mono- and bisformazans in sulfide oxidation and ethylene oligomerization reactions

Article abstract of DOI:10.1134/S0965544115030068

Metal complexes with different numbers of iron atoms in a predominantly nitrogen-containing coordination environment have been synthesized on basis of benzothiazole mono- and bisformazans. The composition and structures of the resulting iron coordination compounds have been characterized by electronic absorption spectroscopy, elemental analysis, mass spectrometry, electron spin resonance, and magnetochemistry. The catalytic behavior of these metal chelates in the liquid-phase oxidation of sulfides and the oligomerization of ethylene has been studied.

Full text of DOI:10.1134/S0965544115030068

ISSN 0965ꢀ5441, Petroleum Chemistry, 2015, Vol. 55, No. 3, pp. 217–223. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © I.S. Maksakova, I.G. Pervova, G.P. Belov, I.I. Khasbiullin, N.A. Ivanova, E.N. Frolova, I.N. Lipunov, 2015, published in Neftekhimiya, 2015, Vol. 55, No. 3,
pp. 228–235.
Synthesis, Structure, and Catalytic Properties of Iron Complexes
with Monoꢀ and Bisformazans in Sulfide Oxidation
and Ethylene Oligomerization Reactions
I. S. Maksakovaa, I. G. Pervovaa, G. P. Belovb, I. I. Khasbiullinb, c, N. A. Ivanovad,
E. N. Frolovad, and I. N. Lipunova
aUral State Forest Engineering University, Sibirskii trakt 37, Yekaterinburg, Sverdlovsk oblast, 620100 Russia
eꢀmail: biosphera@usfeu.ru
bInstitute of Problems of Chemical Physics, Russian Academy of Sciences,
pr. Akademika Semenova 1, Chernogolovka, Moscow oblast, 142432 Russia
eꢀmail: gbelov@cat.icp.ac.ru
cKazan National Research Technological University, ul. Karla Marksa 68, Kazan, Tatarstan, 420015 Russia
eꢀmail: khailnaz@yandex.ru
dZavoiskii Physicotechnical Institute, Kazan Scientific Center, Russian Academy of Sciences,
Sibirskii trakt 10/7, Kazan, Tatarstan, 420029 Russia
Received October 16, 2014
Abstract—Metal complexes with different numbers of iron atoms in a predominantly nitrogenꢀcontaining
coordination environment have been synthesized on basis of benzothiazole monoꢀ and bisformazans. The
composition and structures of the resulting iron coordination compounds have been characterized by elecꢀ
tronic absorption spectroscopy, elemental analysis, mass spectrometry, electron spin resonance, and magneꢀ
tochemistry. The catalytic behavior of these metal chelates in the liquidꢀphase oxidation of sulfides and the
oligomerization of ethylene has been studied.
Keywords: bisformazans, iron formazanates, liquidꢀphase sulfide oxidation, ethylene oligomerization
DOI: 10.1134/S0965544115030068
Ironꢀcontaining catalytic systems are characterized of oxygenꢀcontaining coordinating substituents in the
by high activity and selectivity for higher linear ethylene structure of the initial formazan ligand, the reactions
oligomers under mild reaction conditions [1–5] and, as with Fe(III) salts give rise to trivalent iron complexes,
such, hold much promise for industry to provide a susꢀ whereas the unsubstituted formazans undergo partial
tainable use of feedstock. Furthermore, both the nature oxidation of the ligand to the tetrazolium salt, thereby
of the ligand itself and the type of substituents that facilitating the reduction of Fe3+ to Fe2+ and the forꢀ
bears, which may affect the course of oligomerization, mation of divalent iron formazanates.
play an important role in the catalytic process. For
example, the presence of chlorine atoms in the coordiꢀ
nation sphere of a complex compound influences the
selectivity of oligomerization and promotes catalytic
ability of the complex [1–5]. A wide range of metal forꢀ
mazanates as chemical objects were well studied in [6].
The catalytic properties of metal complexes with forꢀ
mazan ligands in ethylene oligomerization were previꢀ
ously tested only for nickel formazanates [7]. The cataꢀ
lytic behavior of some Fe(II) formazanates in ethylene
oligomerization in the presence of different organoaluꢀ
minum compounds was shown in [8, 9].
In the present study, we prepared a set of iron comꢀ
plexes 1Fe–10Fe using ligands L1, L2, and L3
described previously [7]. The methoxy group R = OMe
introduced into the structure of both monomeric and
bisformazans possesses potential coordinating ability
toward the metal atom [11]. Thus, differences in the
composition, structure, and arrangement of the metal
coordination sphere will determine to a considerable
extent the catalytic activity of iron chelates in redox
reactions.
EXPERIMENTAL
Methods and Equipment
Nevertheless, particular attention is given to the
iron complexes formed by formazans that bear oxyꢀ
genꢀcontaining coordinating substituents, in which
The purity of the resulting iron complexes was
the metal ion can change its valency as a result of comꢀ monitored using thin layer chromatography (TLC) on
plex formation. It was found [10] that in the presence Silufol UVꢀ254 silica gel precoated sheets.
217

218
MAKSAKOVA et al.
The electron absorption spectra in the visible and
The magnetic characteristics of the compounds
were measured by the Faraday method at 293 K.
near UV regions were recorded on a Shimadzu
UVꢀ1800 spectrophotometer in the wavelength range
of 250–1000 nm. To perform titration, solutions of
The electron spin resonance measurements were
conducted in the Xꢀband and the temperature interval
of 20–300 K on a Bruker EMXplus spectrometer. The
parameters of the spectra and their relative contribuꢀ
tion into the total spectrum were determined on the
basis of model calculations of the line shape using the
program Easyspin.
formazans L1–L3 with a concentration of Сf = 3
×
10–5 mol L–1 were prepared by dissolving analytical
samples of formazans L1–L3 in 25 mL of alcohol.
The resulting solution was titrated with an aqueous
iron(III) perchlorate solution (СFe = 10–3 mol L–1).
The absorption spectra were recorded after each
addition of the salt solution [8].
Synthesis of Iron Metal Complexes
The elemental analysis was carried out with a CHN
PE2400SII automated analyzer (Perkin Elmer Instruꢀ
ments). The analysis for metals was carried out by
rapid gravimetry on Khimlabpribor equipment in the
Laboratory of Elemental Analysis [8].
The initial formazan ligands were synthesized
according to the procedures described elsewhere [7, 9].
Synthesis of iron(III) bisꢀ1ꢀ(2ꢀmethoxyphenyl)ꢀ3ꢀ
thienylꢀ5ꢀ(benzothiazolꢀ2ꢀyl)formazanate (5Fe). A hot
aqueous Fe(ClO4)3 · H2O (0.019 g/0.10 mmol) solution
The mass spectrophotometric investigations of the
formazans and the complexes were performed on a
LCMSꢀ2010 Shimadzu liquid chromatograph–mass
spectrometer in the chemical ionization mode at
ambient pressure and electrospray ionization with
detection of positive and negative ions. The samples
were introduced into the mass spectrometer through
the chromatograph with an SPDꢀM10Avp diode array
detector by direct injection into the ion source.
was added with heating and stirring to a solution of
0.36 g (0.20 mmol) of formazan L2 dissolved in acetone
(30 mL). Depending on the formazan structure, mixing
of the solutions led to a drastic change of color from red
or violet to dark brown, vinous, and green. The resulting
complex was stirred for 30 min and then held in a porꢀ
celain dish until solvent removal. Then, the suspension
was filtered off on a vacuum filter, washed with warm
water (~30
2°C), and dried at room temperature.
Iron(III) formazanates 1Fe–4Fe, 6Fe–10Fe were
synthesized in the same manner. The characteristics of
resulting iron formazanates 1Fe–10Fe are presented
in Tables 1 and 2.
R
N
№ МC:
NH N
Catalytic oxidation of sodium sulfide solution. The
catalytic activity of iron(III) formazanates was studied
in a conventional setup consisting of a microcompresꢀ
sor and a sparger. An analytical sample of 0.0008–
0.0009 g (for complexes 1Fe–6Fe) or 0.0015–0.0017 g
(for bismetal chelates 7Fe–10Fe) was dissolved in ethꢀ
anol (5 mL). After complete dissolution, this mixture
was poured into a frittedꢀglass sparger, then, a solution
1Fe: R = Н,
4Fe: R = OCH3,
7Fe: R = Н,
n = 1
S
N
N
n
= 1
= 1
= 1
n
= 2
O
n
L1
R
of Nа2S ·9Н2О(25 mL) with a concentration of 0.3 g/L
N
S
was added. Air was blown through the sparger with the
reaction mixture using the microcompressor for
30 min. After air blowing, an aliquot (10 mL) was
taken from the sparger and added to a beaker with the
copper chloride solution (15 mL) (the concentration
of CuCl2 was five times higher than that of S2– ions).
Mixing of the solutions resulted in the reaction and
precipitation of dark brown copper sulfide (CuS). The
precipitate was filtered off on a paper filter, the clariꢀ
fied solution was analyzed for residual copper(II) ions,
and the concentration of sulfide ions was calculated on
this basis [12].
NH N
2Fe: R = H,
5Fe: R = OCH3,
8Fe: R = H,
n
= 1
N
N
n
n
= 2
S
n
L2
R
N
S
NH N
3Fe: R = H,
n
= 1
N
N
6Fe: R = OCH3,
9Fe: R = H, = 2
10Fe: R = OCH3,
n
Ethylene oligomerization reaction. Toluene was puriꢀ
fied according to the standard procedure [13] and disꢀ
tilled over molecular sieves 4–5 Å. The catalytic experꢀ
iments were carried out using ethylene of 99.9% purity.
n
n
= 2
N
n
The cocatalyst, Al(C2H5)2Cl in heptane, was used
without further purification. Toluene was used as a
L3
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SYNTHESIS, STRUCTURE, AND CATALYTIC PROPERTIES OF IRON COMPLEXES
219
Table 1. Characteristics of iron complexes based on benzothiazolylformazans
MC
Yield, %
Tmp
,
°
C
λmax (L), nm λmax(M
C), nm
M+, m/z (I, %)*
748 (64)
Mr, g/mol
1Fe
2Fe
3Fe
4Fe
5Fe
6Fe
7Fe
8Fe
9Fe
10Fe
72
63
67
72
58
71
42
53
39
41
252
>250
218
243
197
214
246
191
222
226
470
485
415
490
495
500
500
500
450
570
700
710
680
660
640
740
655
717
705
770
748.84
780.94
888.40
808.88
841.00
830.94
1443.66
1603.92
1698.75
1802.86
780 (100)
889 (98)
808 (100)
840 (100)
830 (100)
442.1 (100)
438 (90), 642.6 (100)
743 (100)
830 (100), 696 (67)
* Molecular peaks of fragment ions with an abundance of more than 20% are presented.
Table 2. Characteristics of iron complexes based on benzothiazolylformazans
Found, %
Empirical formula
H
Calculated, %
MC
C
H
N
Fe
C
H
N
Fe
1Fe
2Fe
57.66
55.31
3.23
3.11
18.68
17.89
7.46 (C18H12N5SO)2 · Fe
7.19 (C18H12N5S2)2 · Fe
57.74
55.36
3.24
3.10
18.71
17.94
7.48
7.17
(C19H13N6S)2 · Fe · ClO24– · H2O
3Fe
51.17
3.19
18.88
6.28
51.37
3.18
18.92
6.30
4Fe
5Fe
6Fe
7Fe
8Fe
56.24
54.30
60.07
60.12
55.53
3.50
3.35
3.81
3.59
3.16
17.25
16.59
19.40
19.35
17.46
6.95 (C19H14N5SO2)2 · Fe
56.42
54.27
57.81
59.90
55.41
3.50
3.36
3.65
3.50
3.15
17.32
16.66
20.23
19.41
17.47
6.92
6.66
6.73
3.88
6.98
6.64 (C19H14N5S2O)2
6.48 (C20H15N6SO)2
⋅
Fe
⋅
Fe
3.88 (C36H25N10S2O2)2
⋅
Fe
6.98 (C36H22N10S4)2
⋅
Fe2 C2H5OH
⋅
Fe · 2ClO24– · H2O
Fe
2ClO24–
9Fe
53.02
55.21
2.97
3.15
19.54
19.16
3.24
53.73
55.29
2.85
3.25
19.79
18.65
3.29
3.12
(C38H24N12S2)2
⋅
10Fe
2.95
(C40H29N12S2O2)2
⋅
⋅
medium to prepare the desired concentration of orgaꢀ lary column with the bonded phase composed of 95%
noaluminum compounds.
of phenylenesiloxane and 5% of phenylpolysilane.
The column had a length of 30 m, an outer diameter of
Ethylene oligomerization was carried out in toluene
in a stainless steel reactor (0.2 L) equipped with a magꢀ
netic stirrer and a pressure gauge, which was used to
control ethylene pressure. The temperature in the
reactor was controlled by supplying thermostated water
into the reactor jacket. The clean reactor purged with
an inert gas was evacuated for 1–2 h at 353 K. Then,
the reactor heated to the required temperature was
charged with calculated amounts of the solvent; ethylꢀ
ene; and sequentially, using metallic syringes according
to the Schlenk technology, solutions of iron formazanꢀ
ate and the cocatalyst, the components of the catalytic.
Ethylene oligomerization was carried out for 1 h.
The products of ethylene oligomerization were
determined by GLC on a CHROM 5 chromatograph
with a flame ionization detector. The mixture was sepꢀ
0.25 mm, and film thickness of the phase of 0.25 m;
µ
helium used as the carrier gas had a flow rate of
15 mL min–1; the flow rates of air and hydrogen were
100 and 25 mL min–1, respectively. The column temꢀ
perature was programmed from 40 to 80°C a heating
rate of 6°C/min and from 80 to 160°C at a rate of
10°C/min. The evaporator and detector temperatures
were maintained at 200°C. The liquid sample of a
0.2
µ
L size was introduced with a microsyringe [13].
The recording and processing of chromatograms
was carried out using a Multikhrom hardwareꢀandꢀ
software complex. The product composition of oligoꢀ
merization was determined by the normalization of
arated on a Thermo Fisher Scientific TRꢀ5MS capilꢀ peak areas to 100%.
PETROLEUM CHEMISTRY Vol. 55
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220
MAKSAKOVA et al.
pseudooctahedral structure with the FeN6 coordinaꢀ
a
b
tion sphere and the methoxy group introduced in the
orthoꢀposition of the aryl moiety being not involved in
the coordination to the iron atom.
d
The complication of the ligand molecules by douꢀ
bling the formazan unit led to the production of coorꢀ
dination compounds with more diverse compositions
depending on the substituent nature in the mesoꢀposiꢀ
tion of the formazan molecule.
1
2
c
Formazanates 9Fe and 10Fe, obtained on the basis
on bisligands L3 bearing the pyridinyl substituent in
the mesoꢀposition of the formazan chain, are paraꢀ
magnetic (μeff = 1.2 mB for compound 9Fe) and have
composition L2M. The ESR spectra of the test samples
of 9Fe and 10Fe represent a superposition of several
types of signals (Fig. 1).
0
100
200
300
400
500
600
H, mT
Fig. 1. ESR spectra of formazanates (
= 9.47 GHz; = 160 K.
1) 9Fe and (2) 10Fe.
ν
T
Signals (a) and (b) belong to the lowꢀspin comꢀ
plexes of Fe(III) ions with a spin of S = 1/2. Signal (c)
can be associated with the existence of a certain
amount of free radicals in the bulk of the sample. Sigꢀ
RESULTS AND DISCUSSION
Synthesis and Characterization
of Iron(II,III) Formazanates
nal (d) with geff
plexes of Fe(III) ions with a spin of
characterized by strong axial (
~ 1/3) distortions. The results of calculations of
≅
4.2 belongs to the highꢀspin comꢀ
= 5/2, which are
) and rhombic
S
It is well known [14] that formazans readily form
D
ꢀ
h
ν
complexes with transition metal ions. The ease of
complexation is shown by spectrophotometric titraꢀ
tion of ethanol solutions of the free ligands with an
aqueous solution of a metal salt; however, we did not
manage to study in detail the complexation of both
monoꢀ and bisformazans with iron(III) ions because
of the absence of a distinct spectral pattern of titration.
Nonetheless, the direct synthesis by heating in accordꢀ
ing with the procedure described above afforded iron
formazanates 1Fe–10Fe in the solid state, which were
characterized by elemental analysis, electron specꢀ
troscopy, mass spectrometry, magnetochemistry, and
electron spin resonance (ESR).
(E/D
the parameters of spectra (a)–(c) and their relative
contributions to the total spectrum are presented in
Table 3 and Fig. 2.
From the above consideration, it follows that the
iron ions in compounds 9Fe and 10Fe are mainly in
the trivalent state and form lowꢀspin centers of
type (a). The gꢀfactors of spectra (a) of the lowꢀspin
Fe(III) complexes were analyzed in the oneꢀelectron
approximation within the lower orbital triplet as had
been done in [16]. The results of the analysis are preꢀ
sented in Table 4.
Unfortunately, the structure of isolated solid
iron(II,III) formazanates could not be determined by
Xꢀray diffraction analysis because of their amorphous
state.
The identity of the ESR parameters of these centers
in both compounds indicates the similarity of the inner
coordination spheres formed by the iron ions. The
structural differences between compounds 9Fe and
According to the elemental analysis and mass specꢀ 10Fe are in the rather remote iron ion coordination
tral data, all 1Fe–6Fe iron chelates based on monoforꢀ spheres and do not affect the crystal field parameters
mazans have the composition L2M. The results of magꢀ (within the experiment accuracy). The lowꢀspin state
netochemical (μeff = 0 mB) and ESR (using the 3Fe, (with the invariable parameters of spectra) is retained in
6Fe compounds as an example) measurement show the the entire range of temperatures (20–300) K, thereby
formation of diamagnetic coordination compounds suggesting the absence of a spin transition. The high
1Fe–6Fe that contain the iron(II) atoms in the lowꢀ value of coefficient
spin state ( = 0). According to published data [15, 16], damental Kramer’s doublet shows that the main state is
B of the wave function for the funꢀ
S
it is obvious that the Fe(II) complexes formed have a the
|
dxy> orbital.
|
Table 3. Parameters of ESR spectra of samples 9Fe and 10Fe
Spectrum (a)
MC
Spectrum (b)
Spectrum (c)
g
g||
na
g1
g2
g3
nb
g
nc
_|
9Fe
2.175
2.175
1.937
1.937
0.62
0.64
2.110
2.122
2.045
2.122
1.937
1.985
0.34
0.35
2.00
2.00
0.04
0.01
10Fe
ni
(i
= a, b, c) are the weight coefficients of (a)–(c) type spectra in the total spectrum.
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SYNTHESIS, STRUCTURE, AND CATALYTIC PROPERTIES OF IRON COMPLEXES
221
9Fe
10Fe
a
a
c
b
b
c
240 260
280
300
320
340
360
380 240 260
, mT
280
300
320
340
360
380
H, mT
H
Fig. 2. Fragments of ESR spectra of samples 9Fe and 10Fe (black and red lines refer to the experimental spectrum and the calcuꢀ
lated total spectrum, respectively).
The presence of type (b) centers in the ESR spectra
The catalytic tests showed that the iron formazanꢀ
of the test samples also does not rule out the formation ates 1Fe–10Fe exhibit activity in this reaction; the calꢀ
of iron complexes in which the axial positions are culated degrees of sulfur conversion (i.e., the ratio of
occupied by the perchlorate ions or solvent molecules. sulfur transformed into sulfates as a result of reaction
to the amount of sulfur in the initial sulfide solution)
vary within 19–42%).
It was noted that the reaction of unsubstituted bisꢀ
formazan L1, which bears the furyl substituent in the
mesoꢀposition, with Fe(III) ions under the aforemenꢀ
tioned conditions leads to the formation of trivalent
iron paramagnetic complex 7Fe (μeff = 2.0 mB) of
L2M composition. Furthermore, the use of thienylꢀ
containing formazan L2 made it possible to prepare
binuclear (L2M2) diamagnetic complex 8Fe, which
was characterized by the data of Mössbauer spectrosꢀ
copy and magnetochemistry (μeff = 0 mB).
Of the unsubstituted (R = H) monomeric benꢀ
zothiazolylformazanates, formazanate 3Fe showed
the highest catalytic activity; the degree of sulfur conꢀ
version on it was 42%. The presence of an additional
group R = ОСН3 in the structures of formazanates
4Fe, 5Fe, and 6Fe compared to their unsubstituted
analogs 1Fe (21%), 2Fe (21%), and 3Fe (32%) did not
substantially affect the catalytic activity: 4Fe (24%),
5Fe (22%), and 6Fe (32%).
The degrees of sulfur conversion in the liquidꢀ
phase sulfide oxidation reaction catalyzed by bisforꢀ
mazanates are comparable with those achieved with
their monomeric analogs. The highest value of 27%
was found for unsubstituted biscomplex 7Fe.
The ethylene reactions leading to the formation of
ethylene dimers, oligomers, and polymers are of parꢀ
ticular interest both from the scientific (novel types of
ligands) and industrial points of view. These reactions
can yield the linear and branched compounds, which
find application in different fields of engineering and
technology, for example, in production of detergents
and polyethylene [18]. Oligomerization processes
Catalytic Activity
The catalytic properties of the resulting metal cheꢀ
lates of diꢀ and trivalent iron were tested in the reacꢀ
tions with different mechanisms, the model reaction
of liquidꢀphase oxidation of sulfides and the industriꢀ
ally important ethylene oligomerization reaction.
In the presence of metalꢀcontaining catalysts 1Fe–
10Fe, the liquidꢀphase oxidation of sodium sulfide at
room temperature (20°C) under conditions of homogeꢀ
neous catalysis proceeds via the following scheme [17]:
Fe(
)
2
formazan
20°С
Na2S + 2O2
Na2SO4.
Table 4. Results of analysis of gꢀfactors for lowꢀspin Fe(III) complexes of type (a) in the test compounds
MC
g
g||
A
B
C
K
Δ
/
ξ
ΔE12/ξ
Δ
E13/
ξ
_|
9Fe, 10Fe
2.175
1.937
0.10906
0.99403
0.0
0.6483
2.289
6.522
7.445
A, B, and C are the coefficients of wave functions for the fundamental Kramer’s doublet, K is the spinꢀorbital coupling suppression
coefficient, is the oneꢀelectron spinꢀorbital coupling constant, is the tetragonal component of the crystal field, and and
are the values of the corresponding energy intervals between the orbital triplet levels.
ξ
Δ
ΔE
Δ
E
13
12
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222
MAKSAKOVA et al.
1.2
1.1
1.0
0.9
0.8
0.7
0.6
1
(а)
(b)
1
2
1.2
1.0
0.8
0.6
0.4
0.2
3
4
2
0
10
20
30
Time, min
40
50
60
0
10
20
30
Time, min
40
50
60
Fig. 3. Kinetic curves of ethylene consumption in oligomerization reaction in the presence of iron formazanates based on
(a) monoligands: ( ) 1Fe, ( ) 2Fe, ( ) 4Fe, ( ) 5Fe and (b) bisligands: ( ) 10Fe, ( ) 9Fe. Reaction conditions: = 80 C,
= 2.0 MPa, = 4 = 60 mL, Al : Fe = 20 : 1 (mol).
1
2
3
4
1
2
Т
°
–5
Р
С
×
10 mol/L, V
Fe
toluene
using predominantly homogeneous catalysts based on the negative effect can be exerted both by oxygen
organometallic complexes bearing transition metals in atoms in the solvent molecules and those in the strucꢀ
their structures in combination with organoaluminum ture of the catalyst itself.
compounds are the most popular.
It was found that the iron(III) catalyst systems
Fe(
formazan
toluene
) + AlEt Cl
2
based on monoformazans 4Fe–5Fe, which contain
the R = ОСН3 group in their structure (Fig. 3a) exhibꢀ
ited a lower activity than unsubstituted benzothiazꢀ
olylformazanates 1Fe–2Fe. At the same time, formaꢀ
zanate 10Fe, which contains the pyridinyl moiety,
showed the highest catalytic activity and the best onꢀ
stream time among iron bisformazanates. The
decrease in ethylene absorption with time can be due
to two factors, a reduction in partial pressure of ethylꢀ
ene in the reactor because of the formation of butenes
and hexenes during the reaction and a possible
decrease in the amount of active sites of the catalyst.
2
nC2H4
higher αꢀolefins.
, 80°С
At the same time, the search for effective and selective
catalytic systems is still an urgent task.
For nickel formazanates tested in this reaction earꢀ
lier [7, 9], the optimal conditions of the process were as
follow:
Т
= 80°C,
Р
= 2.0 MPa,
С
Fe = 4
10–5 mol/L,
×
cocatalyst: diethylaluminum chloride (Al(C2H5)2Cl).
Figure 3 depicts rate curves for ethylene consumpꢀ
tion in the presence of catalytic systems based on some
of the iron(II,III) formazanates obtained in this work.
The performance of a catalytic system using orgaꢀ
noaluminum compounds as a cocatalyst is known [19]
The analysis of reaction products by gas–liquid
to depend on the presence in the reaction mixture of chromatography showed (Table 5) that ethylene oligoꢀ
oxygen atoms that lead to their degradation. Note that merization in the presence of diethylaluminum chloꢀ
Table 5. Catalytic activity of iron formazanates in oligomerization of ethylene (
T
= 80°C,
P
= 2.0 MPa,
CFe = 4
×
10–5 mol/L,
Vtoluene = 60 mL, Al : Fe = 20 : 1 (mol))
Product composition, wt %
1ꢀC6H12
Activity,
kg/g Fe h
MC
1ꢀC4H8
olefins C8+
1Fe
2Fe
9.52
9.52
8.66
8.66
8.22
10.39
42
63
56
29
29
58
3
25
11
7
55
12
33
64
–
4Fe
5Fe
9Fe
71
42
10Fe
–
PETROLEUM CHEMISTRY Vol. 55
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2015

SYNTHESIS, STRUCTURE, AND CATALYTIC PROPERTIES OF IRON COMPLEXES
223
ride proceeds toward the formation of predominantly
ꢀolefins (buteneꢀ1, hexeneꢀ1) with a low amount of
byproducts.
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ACKNOWLEDGMENTS
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This work was supported by the Russian Foundaꢀ
tion for Basic Research, project nos. 11ꢀ03ꢀ90724ꢀ
mob_st and 11ꢀ03ꢀ00181, and program no. 3 of the
Presidium of the Russian Academy of Sciences
“Energy Aspects of Deep Processing of Fossil and
Renewable CarbonꢀContaining Resources.”
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and discussion of the ESR spectra.
Translated by K. Aleksanyan
PETROLEUM CHEMISTRY Vol. 55
No. 3
2015