Formation and properties of Ziegler systems based on nickel bis(dimethylglyoximate) in catalysis of hydrogenation reactions

Article abstract of DOI:10.1134/S1070363214120111

The effect of the nature of the acidoligand in the nickel precursor on the activity of Ziegler systems in hydrogenation of alkenes was characterized qualitatively. The key steps of the reaction of nickel bis (dimethylglyoximate) with triethylaluminum determined by the methods of IR, NMR, and ESR spectroscopy include the reaction between AlEt₃ and the OH group of the dimethylglyoximate ligand, formation of the product of C-alkylation as a result of addition of AlEt₃ to the C=N bond, and the reduction of Ni(II) to Ni(0) complexes. The absence of nickel clusters and a low concentration of coordinatively unsaturated Ni(0) complexes is the most probable reason of low catalytic activity of the studied system in hydrogenation catalysis.

Full text of DOI:10.1134/S1070363214120111

ISSN 1070-3632, Russian Journal of General Chemistry, 2014, Vol. 84, No. 12, pp. 2413–2420. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © Yu.Yu. Titova, L.B. Belykh, F.K. Shmidt, 2014, published in Zhurnal Obshchei Khimii, 2014, Vol. 84, No. 12, pp. 1996–2002.
Formation and Properties of Ziegler Systems Based
on Nickel Bis(dimethylglyoximate) in Catalysis
of Hydrogenation Reactions
Yu. Yu. Titova, L. B. Belykh, and F. K. Shmidt
Irkutsk State University, pr. K. Marksa 1, Irkutsk, 664003 Russia
e-mail: fkschmidt@chem.isu.ru
Received July 17, 2014
Abstract—The effect of the nature of the acidoligand in the nickel precursor on the activity of Ziegler systems
in hydrogenation of alkenes was characterized qualitatively. The key steps of the reaction of nickel bis
(
dimethylglyoximate) with triethylaluminum determined by the methods of IR, NMR, and ESR spectroscopy
include the reaction between AlEt and the ОН group of the dimethylglyoximate ligand, formation of the
product of С-alkylation as a result of addition of AlEt to the С=N bond, and the reduction of Ni(II) to Ni(0)
3
3
complexes. The absence of nickel clusters and a low concentration of coordinatively unsaturated Ni(0)
complexes is the most probable reason of low catalytic activity of the studied system in hydrogenation
catalysis.
Keywords: Ziegler systems, nickel, hydrogenation, mechanism of formation
DOI: 10.1134/S1070363214120111
Ziegler systems consisting of transition metal
complexes and organoaluminum compounds are one of
the most important groups of industrial catalysts not
only for oligo- and polymerization of lower alkenes
gives nanoclusters predominantly of 1.5–3.5 nm diameter
[4, 6–8]. In [7–10] the model of nanoparticles was
suggested according to which the formed by a redox
process AlR (аcac) was adsorbed on the surface of nano-
2
[1–3] but also for hydrogenation [3, 4]. For example,
clusters thus increasing their stability to aggregation:
relatively cheap Ziegler catalysts based on Co and Ni
compounds are used for the synthesis of hydrogenated
styrene block-copolymers, whose production approaches
Et
acac
Et
Et
2
00000 tons per year [5]. In spite of industrial use of
Al Et
these metal complex catalysts, there is a necessity for
further investigation of the Ziegler systems for a
purposeful control of the processes of formation of
catalytically active species and a design of more
effective catalysts. According to [3, 4], nowadays
fundamental problems of investigation of the Ziegler
hydrogenation catalysts are determination of the
influence of the conditions of formation on the catalytic
properties, especially on the activity and stability of
the catalysts; investigation of the reactions between the
precursors based on transition metal compounds and
the components of the cocatalyst; compositional and
structural nature of the catalytically active compounds;
mechanisms of catalytic hydrogenation.
Al
Et
Et
Et
Al
acac
Et
( ) denotes free space.
Note that up to now the question of the nature of
nanoclusters stabilizers in Ziegler systems has no
unequivocal experimental proof. Taking into account
the poisoning effect of excess AlR on the turnover
frequency in hydrogenation of alkenes, as stabilizers of
3
Most researchers agree that the reaction of VIII
group metal acetylacetonates with trialkylaluminum
nanoclusters along with AlR (аcac) trialkylaluminum
is also postulated, whose reaction with the transition
2
2
413

2
414
TITOVA et al.
Scheme 1.
H
R
Et
M
AlEt3
M
AlEt2
M
AlEt2
M
AlEt2
Et
Et
metal atoms under the conditions of hydrogenation
catalysis can result in the formation of surface com-
pounds of the types [7] (Scheme 1).
In spite of these visual changes, hydrogenation of
styrene in the presence of catalytic system Ni(dmg)2–
nAlEt
~2 h) indicative of a low rate of transformation of the
at 30°С occurs with a long inductive period
3
(
Stabilization of nanoclusters with alkoxy aluminum
derivatives, which can be formed in the presence of
traces of oxygen and/or water due to high reactivity of
organoaluminum compounds, cannot be ruled out,
either [11]. Experimental support of the hypotheses on
the nature of stabilizing effect of the catalytically
active species will provide a solution of the problem of
Ziegler systems stability under the conditions of
hydrogenation catalysis.
nickel precursor to the catalytically active species
under mild conditions. The average activity of the
system Ni(dmg) –AlEt ([Al] : [Ni] = 5) in hydro-
2
3
–
1
genation of styrene does not exceed 0.08 min . The
maximum catalytic activity in hydrogenation of
cyclohexene was 0.03 min , which is much worse
than the activity of the Ziegler systems based on nickel
bis(acetylacetonate) for which the turnover frequency
–
1
–1
in hydrogenation of terminal alkenes reached 140 min .
At the increase of the temperature to 50 and 70°С the
inductive period was shortened and the catalytic
activity increased 2 and 8 times respectively. A charac-
teristic feature of the Ziegler systems in hydrogenation
catalysis is the extremal shape of the dependence of
specific catalytic activity on the ratio [Al] : [М] when
trialkylaluminum is used as a cocatalyst [3, 7, 8]. For
the system Ni(dmg) –nAlEt , the ratio of the com-
With the aforesaid in mind, an important problem
of the Ziegler catalysis is establishing of the influence
of the nature of acidoligand in the precursor of the
transition metal complex on the catalytic properties.
Formation of complexes (nanoclusters) active in
hydrogenation in the Ziegler type systems is connected
with substitution by alkyl groups of ligands, which are
covalently or coordinatively bound with the transition
metal. Therefore, a decrease of activity of these
systems with the increase of stability of the starting
transition metal complexes can be expected [3].
However, taking into account various functions of a
cocatalyst, the nature of acidoligand in the precursor
2
3
ponents at which the activity is maximal ([Al] : [Ni] ≈
1
5) is 3–4 times higher than at the use of Ni(acac) as a
2
precursor under the same conditions (Fig. 1).
The results of investigation of the effect of the
nature of nickel precursors on the activity of catalytic
(
MX ) may affect not only the rate of reduction but
n
also the stabilization of the formed particles
complexes) with organoaluminum compounds and,
systems NiX –AlEt in hydrogenation of cyclohexene
2 3
(
are presented in the Table. According to the table,
there is a reverse dependence between the catalytic
hence, their catalytic properties. Most studied as the
precursors in the Ziegler systems are acetylacetonates
and 2-ethylhexanates of transition metals [3–10]. Here
we present the results of investigation of catalytic
properties and the reaction between the components of
the catalytic system on the basis of triethylaluminum
activity of systems NiX –AlEt [Х = acetylacetonate
2 3
(I), о-aminophenolate (II), salicylaldoximate (III), 8-
oxyquinolate (IV), and dimethylglyoximate (V)] and
the constants of stability of the nickel complexes. With
the increase of the constant of stability the turnover
number decreases by more than three orders of
magnitude. The effect of thermodynamic and kinetic
stability of transition metal compounds on the
hydrogenation activity of the Ziegler type catalysts
was first established in [12].
and nickel bis(dimethylglyoximate) [Ni(dmg) ]. The
2
choice of the latter as a precursor was due to the
presence in the acidoligand various heteroatoms (O, N)
capable of complexation with the transition metal, and
its diimine structure.
Ni(dmg) is poorly soluble in organic solvents, but
the addition of triethylaluminum to the suspension of
To evaluate the validity of the hypotheses on such a
strong effect of the nature of acidoligand on quan-
titative characteristics of Ziegler systems in hydro-
genation catalysis, we have studied the model system
2
Ni(dmg) in benzene leads to homogenization of the
2
system in the course of 1–2 min with the formation of
a dark-red solution and evolution of gaseous products.
Ni(dmg) –AlEt using spectral methods.
2 3
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FORMATION AND PROPERTIES OF ZIEGLER SYSTEMS
A characteristic absorption band of Ni(dmg) in the
2415
2
–
1
IR spectrum is the ν(С=N) band at 1568 cm [13]. In
the spectrum of Ni(dmg) intense bands of stretching
2
–1
–1
vibrations of the N–O bond (ν 1238 cm , ν 1098 cm )
as
s
are also present. The bands of stretching and defor-
mational vibrations of the bridging О–Н groups
–
1
–1
(
ν 3200 cm ; δ 1785 cm ) in the dimethylglyoximate
s
ligand Ni(dmg) have low intensity.
2
Upon the reaction of suspension of Ni(dmg) in
2
benzene with triethylaluminum ([Al] : [Ni] = 2) under
argon the reaction system becomes homogeneous. The
process is followed by evolution of a gas in the amount
of 1.9 mol/mol Ni, which consists mainly of ethane
Al : Ni
on the catalytic
activity of the system Ni(dmg) –nAlEt in hydrogenation
(
98%) and traces of ethylene and butene-1. In the IR
3 2
Fig. 1. Effect of the ratio AlEt : Ni(dmg)
spectrum of the system Ni(dmg) –2AlEt taken after
2
3
2
3
of cyclohexene. Conditions of the reaction: 30°C, р(H
2
) =
2
0 min from the beginning of the reaction the band
–
1
2 at, volume of solution 18 mL, solvent – benzene, [Ni] =
ν(С=N) at 1568 cm is shifted to higher frequencies
by 25 cm and the band at 1785 cm corresponding to
–
2
–
1
–1
1.4 × 10 mol/L; [Al] : [Ni] = 15.
deformational vibrations of the bridging О-Н groups of
reaction between AlEt and the bridging hydroxy
groups of the dimethylglyoximate ligand:
Ni(dmg) is lacking (Fig. 2). These changes as well as
3
2
the data of volumetry are indicative of the predominant
H C
CH3
H
3
C
CH3
3
C C
C C
O
N
N
O
O N N O
Ni
H
Ni
H
+ 2 AlEt3
Et Al
2
AlEt2 + 2 C H
2 6
(1)
O N N O
C C
O N N O
C C
H C
CH3
H C
CH3
3
3
I
The absorption band ν(С=N) in free oximes usually
2AlEt we assigned to the stretching vibrations of the
3
–
1
appears at 1685–1650 cm although its position
depends on the strain in the ring [13]. The band at
С=N bond in complex I. Its intensity depends on the
molar ratio of the components. When [Al] : [Ni] is
increased from 2 to 5, its intensity is decreased by an
–
1
1
593 cm in the spectrum of the system Ni(dmg)2–
a
Effect of acidoligand on the turnover frequency in hydrogenation of cyclohexene in the catalytic system NiX
–AlEt
2 3
Parameter
X
I
II
O _
III
IV
V
_
O
OH
O
H3C
CH3
O
_
_
_ _
N
C C
H C C=CH C CH
_
3
3
_
HO _
N_
O
NH2
CH=NO
N
TOF, min‒
1
b
120
25
11.41
15
3
0.03
24.64
c
pK
10.77
‒
21.38
a
–2
b
Reaction conditions: 30°C, р(H
2
) = 2 at, volume of solution 18 mL, solvent – benzene, [Ni] = 1.4 × 10 mol/L; [Al] : [Ni] = 6. [Al] :
c
[Ni] = 15. pK = –log K (K is an instability constant).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 12 2014

2
416
TITOVA et al.
–1
ν, cm
1
800 1750 1700 1650 1600 1550 1500 1450 1400 1350 1300 1250 1200 1150 1100 1050
3
2
1
3
2
1
Fig. 2. IR spectra of the system Ni(dmg)
2
–nAlEt
3
in benzene for the ratio [Al] : [Ni] = (1) 2; (2) 5; and (3) 10.
order of magnitude, and for 10-fold excess of AlEt3,
2 times (Fig. 2, curves 2, 3). Along with this, a new
signals at 0.55 and 1.67 ppm correspond to the protons
1
of the ethyl group of the O–AlEt fragment. The
2
–
1
band appears at 1633 cm , which apparently belongs
to ν(С=N) absorption band in the product of AlEt3
addition to one double bond С=N. This assumption is
based on published data, according to which the
ν(С=N) band of the isolated С=N bond in Ph–N=C·
singlet at δ 1.48 ppm having the same intensity as the
signal at 1.67 ppm was assigned to the methyl group
protons СН С=N in the acidoligand of the nickel
3
1
complex. The analysis of the Н NMR spectroscopy
data is consistent with the results of IR monitoring of
the system Ni(dmg) –2AlEt and confirms the
(
CH )–C(CH )(Et)–N(AlEt )Ph is shifted to high fre-
3 3 2
2
3
–
1
–1
quencies by 25 cm (from 1635 to 1660 cm ) relative
to the starting diimine Ph–N=C(CH )–C(CH )=N–Ph
formation of complex I in the reaction of Ni(dmg)2
3
3
with two moles of AlEt according to scheme (1).
3
[
14]. Taking all this into account the observed decrease
Note that complex I is not the only product of the
–
1
of intensity of the band at 1593 cm with the increase
of the [Al] : [Ni] ratio ([Al] : [Ni] > 2) is indicative of
a partial addition of AlEt to the С=N bond. Additional
information about the products of the reaction of the com-
ponents of the catalytic system Ni(dmg) –nAlEt was ob-
reaction of Ni(dmg) with AlEt at [Al] : [Ni] = 2. In
2
3
1
the Н NMR spectrum of the system Ni(dmg) –2AlEt ,
2
3
3
apart from the described above, the signals at 1.35 ppm
t, J = 8.2 Hz, СН ) and 0.22 ppm (q, J = 8.2 Hz, СН )
(
3
2
2
13
3
were registered in the ratio 3 : 2 (Fig. 3). They suggest
the formation of a different fragment Al–Et. The
intensity of these signals is ~3 times less than that of
1
tained from the analysis of the Н and С NMR spectra.
1
In the Н NMR spectrum of the system Ni(dmg) –
2
2
0
AlEt the signals of free triethylaluminum (δ, ppm:
the signals of the OAlEt fragment of complex I.
3
2
.41, q, J = 8.2 Hz, AlСН CH ; δ 1.22 t, J = 8.2 Hz,
2
3
It is known that AlEt can react with imines [15] or
3
AlСН CH ) are practically lacking. This is an
indication of a nearly quantitative transformation of
AlEt (Fig. 3). Most intense are the signals at 0.55 ppm
2
3
diazobutadienes [14, 16] by the donor-acceptor type
.
with the formation of the adduct R C=NH AlEt . In
2
3
3
many cases, the reaction is not stopped at this stage but
(
q, J = 8.2 Hz) and 1.67 ppm (t, J = 8.2 Hz) in the
further addition of AlEt to the С=N bond takes place
3
ratio 2 : 3 belonging to the protons of the ethyl group
at the aluminum atom, as well as a singlet at 1.48 ppm.
The downfield shift of the signals of СН (Δ =
with the formation of the product of С-alkylation. The
reaction of reduction with imines can be followed also
by the formation of alkenes [14, 16]:
3
0
.45 ppm) and СН (Δ = 0.14 ppm) relative to free
2
AlEt is indicative of the fact that the aluminum atom
is bound to a more electronegative element. For
example, in Al(acac)Et , the protons of the methylene
and methyl groups resonate at δ 0.45 ppm (q, J =
R'N=CR
Al ← NR'=CR
Al ← NR'=CR' → R
For compounds where the AlEt
the nitrogen atom with covalent bond, as well as for
2
' + AlR
3
⇄ R
' → R
AlNR'–C(H)R
3
Al ← NR'=CR
2
',
(2)
(3)
(4)
3
R
3
2
2
AlNR'–C(R)R
2
',
2
R
3
2
2
2
' + R–H.
8
.2 Hz, СН ) and δ 1.47 ppm (t, J = 8.2 Hz, СН )
group is bound to
2
2
3
respectively [7]. From this, it can be concluded that the
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FORMATION AND PROPERTIES OF ZIEGLER SYSTEMS
2417
2
.0
1.7
1.4
1.1
0.8
0.5
0.2
δ, ppm
7
.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
δ, ppm
1
Fig. 3. H NMR spectra of Ni(dmg)
2
–2AlEt
3
system in benzene–d
6
.
adducts of AlEt to nitrogen-containing compounds,
AlEt
3
+ –C(CH
3
)=N– → –C(CH
3
)(Et)–N(AlEt
2
)–. (5)
3
the protons of the methylene group are usually shifted
Then, the signal at 0.97 ppm (t, J = 6.8 Hz, СН ) in
3
upfield with respect to the СН group in free AlEt to
1
2
3
the Н NMR spectrum can be assigned to the methyl
group protons [СН СН –С(СН )–N–AlEt ]. Unfor-
the region 0–0.2 ppm [17, 18]. Therefore, the quartet at
.22 ppm can belong to the CH group either in the
3
2
3
2
0
2
tunately, the signals of the methylene group protons
СН СН –С(СН )–N–AlEt ] cannot be identified
.
13
N–AlEt fragment or in the adduct N AlEt . In the С
2
3
[
3
2
3
2
NMR spectrum of the system Ni(dmg) –2AlEt , along
2
3
because of superposition of multiplets in the region
.3–1.7 ppm (Fig. 3).
with the signal at 158.2 ppm (C=N), a signal of low
intensity appeared at δ 58.7 ppm, whose position
corresponds to a quaternary carbon atom [19]. This
1
1
In the Н NMR spectrum of the system Ni(dmg) –
2
1
3
2
0
8
3
1
AlEt the poorly resolved low intensive signals at
fact, as well as the presence in the С NMR spectrum
along with the methyl carbons (17.7 and 13.5 ppm) the
signals at 24.7 and 8.7 ppm, which can be assigned to
the carbons of ethyl groups not directly bound to
aluminum [δ 24.7 ppm, Н С–СН –С(СН )–N–AlEt ;
3
.48 ppm (q, J = 8.3 Hz, СН ); 0.28 ppm (q, J =
2
.3 Hz, СН ) are also present, as well as the signals at
2
3
.52 ppm (q, JНН 7.1 Hz, –Al–ОСН СН ) and
2
3
.06 ppm (t, J = 7.1 Hz, –Al–ОСН СН ). The latter
2
3
3
2
3
2
two signals correspond to the protons of the ethoxy
group at aluminum (the result of partial oxidation with
traces of oxygen). Their concentration with respect to
the ethyl groups of diethylaluminum in complex 1 does
not exceed ~7%.
δ 8.7 ppm, Н С–СН –С(СН )–N–AlEt ] allows a
conclusion that the reaction of the dimethylglyoximate
3
2
3
2
ligand with AlEt , as in the case of diazabutadienes,
3
results in reduction of the С=N bond with the
formation of the product of С-alkylation. The intensity
of the signals increases with the ratio [Al] : [Ni]. Based
on this, the signals at 1.35 and 0.22 ppm were assigned
to the ethyl fragments at aluminum formed by addition
Therefore, IR and NMR analysis of the products of
the reaction of the components of the system Ni(dmg)2–
2
AlEt is indicative of two predominant processes:
3
of AlEt to the С=N bond:
3
reaction of AlEt with OH group of the dimethyl-
3
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2
418
TITOVA et al.
Ni(dmg) –nAlEt at various ratios of the components,
2
3
including the excess of AlEt , the signals of
3
ferromagnetic nickel or complexes of Ni(I) are lacking.
Consequently, the reduction of Ni(dmg) with triethyl-
2
2
1 E
aluminum, apparently, leads to the formation of com-
plexes of zero-valence nickel. The ESR spectrum of
the system Ni(dmg) –nAlEt shows only low intense
2
3
signal consisting of three lines with g-factor of
.026 (Fig. 4). Taking into account that this value is
2
Fig. 4. ESR spectra of the system Ni(dmg)
2 3
–5AlEt in
close to that of free electron and the spin of nitrogen
atom equal to 1 we suggested that the unshared
electron is localized on the nitrogen atom. The shape
of the simulated spectrum with localization of electron
on one nitrogen atom confirms this assumption.
benzene-d at room temperature.
6
glyoximate ligand, and addition to the С=N bond. The
reaction of AlEt with ОН group can lead only to the
3
formation of the O–AlEt fragment and ethane. Ho-
2
1
wever, from the H NMR data, in the reaction system
The above analysis of the spectral data allows to
suggest the following scheme of the reaction of Ni(dmg)2
ethylene and butene-1 are also present in trace
amounts. The presence of ethylene, whose formation
can be considered as a transfer of ethyl group from
AlEt3 to nickel with subsequent β-hydride shift,
suggests a partial contribution of the redox process
between Ni(dmg) and AlEt even at [Al] : [Ni] = 2.
with AlEt . In the first step, triethylaluminum reacts
3
with the bridging OH group of the dimethylglyoximate
ligand to give complex I. Quantitative proceeding of
this process requires consumption of 2 mol of AlEt3/
mol Ni without a change in the degree of oxidation of
Ni(II). Subsequent transformation of complex I with
2
3
The increase of the yield of gaseous products at
Al] : [Ni] = 5 to 2.2 mol/mol Ni and the fraction of
[
excess AlEt depending on the reaction route can lead
3
ethylene in gaseous phase points to the increase of
contribution of the redox process between the
components, whose rate at room temperature is low.
either to addition of the latter to the C=N double bond
(complex II) or to reduction of Ni(II) to complexes of
Ni(0) (complex III) (Scheme 2).
With increase of the [Al] : [Ni] ratio the spectral
picture is changed. In the Н NMR spectrum of the
Evidently, the coordinatively saturated complexes
of Ni(0) cannot exhibit hydrogenating properties.
Under the conditions of hydrogenation catalysis the sub-
stitution of nitrogen-containing ligands in the coordi-
nation sphere of Ni(0) by a substrate would lead to the
formation of complexes of Ni(0) capable of activation
of molecular hydrogen and of catalysis in the hydro-
genation. The absence of nickel nanoclusters in the
system Ni(dmg) –AlEt and a low concentration of coor-
dinatively unsaturated complexes of Ni(0) cause a
sharp decrease of the hydrogenating activity of this
system relative to the Ziegler catalysts based on the
VIII group metal acetylacetonates under mild
conditions.
1
system Ni(dmg) -5AlEt the intensity of signals of
2
3
complex I (0.55 q, 1.67 t and 1.48 s ppm) is
considerably decreased; broaden signals of the
methylene (δ 0.43 ppm, q, AlСН СН ) and methyl
2
3
group (δ 1.29 ppm, t, AlСН СН ) predominate.
2
3
Broadening of the signals can be caused by the
presence of radicals, inter- or intramolecular exchange
or formation of microheterogeneous system. Since no
broadening of the other signals is observed the most
probable reason for broadening of the signals is inter-
2
3
or intramolecular exchange of AlEt coordinated to
3
1
3
nitrogen. In the С NMR spectrum of the system
Ni(dmg) –5AlEt the intensity of the signals of the
2
3
product of C-alkylation (58.7, 24.7, 17.7, 13.5, 8.7 ppm)
increases. The signals of carbon atoms of the ethyl
group at aluminum appear at 8.5 and 0.6 ppm
EXPERIMENTAL
Solvents (benzene, toluene) were purified by
standard procedures [20], distilled over LiAlH on a
(
AlCH CH and AlCH CH ) respectively.
4
2
3
2
3
rectification column, and stored in argon atmosphere in
sealed ampules over molecular sieves 4А. Content of
water in the solvents measured by Fisher method [21]
was ca. 1 mmol/L.
It is known [3–11] that the reduction of transition
metal acetylacetonates with trialkylaluminum gives
nanoclusters. In the ESR spectra of the system
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 12 2014

FORMATION AND PROPERTIES OF ZIEGLER SYSTEMS
2419
Scheme 2.
H C
CH3
H C
CH3
3
3
C C
C C
H C
CH3
_
3
C C
Ni0
N
N
O
O
O
N
N O
O
O
_
_
_
+
AlEt3
C H
+AlEt3
O AlEt2
Ni2+
Et Al O N
N
Ni2+
2
H
H
Et Al
2
AlEt2
_
_
_ _
−
−C H , C H
2
6
2
6
2
4
N
N O AlEt2
CH3
Et Al O
2
N
N
O
N
N
O
C C
C C
C C
H C
3
H C
CH
3
H C
CH3
3
3
III
I
+AlEt3
C=C
Et Et
_ _
H
3
C
CH3
C C
_
H C C C CH
_
_
_
_
3
3
Et Al O N
N O AlEt
2
Ni0
2
_
_
Et Al N
N AlEt2
O
2
O
C=C
Ni2+
Et Al
AlEt2
2
O
+
O
_
_
Et Al N
N AlEt
_
_
2
2
Et AlON=C(CH )C(CH )=NOAlEt
2 3 3
2
_
H C C C CH
3
3
Et Et
II
Monitoring of the products of the reaction of the
components of catalytic systems on the basis of
Ni(dmg)2 and AlEt3 in argon atmosphere was
performed by the methods of NMR, IR, and ESR
spectroscopy. IR spectra of the reaction system placed
in a hermetic, flushed with argon, KBr cell with the
thickness of the absorbing layer of 0.112 mm were
analyzed on a FT-801 spectrometer. ESR spectra were
taken on a ESP 70-03 XD/2 spectrometer (KBST),
working frequency 9.3 GHz with diphenylpicrylhyd-
filled with hydrogen temperature-controlled vessel was
successively charged in the flow of hydrogen with
Ni(dmg) (74.1 mg, 0.25 mmol), benzene (15 mL) and
2
stirred for 30 min to obtain red-dark suspension. To the
obtained suspension the substrate (8.7 mmol) and
solution of AlEt in octane (2 mL) was added varying
3
the ratio [Al] : [Ni] from 2 to 15. The vessel was
closed with Teflon stopper with rubber septum for
sampling by syringe, excess hydrogen pressure was created
and hydrogenation was carried out at vigorous stirring.
The reaction was followed manometrically by a
decrease of pressure and by GC analysis of the samples.
The catalyzate was analyzed on a Chromatek-Crystal
1
13
razyl as a standard. Н, C NMR spectra were
registered on a DРX 400 Bruker spectrometer.
Synthesis of nickel bis(dimethylglyoximate) Ni(dmg)2
was performed according to [22]. To the solution of
nickel diacetate (8.8 g, 0.25 mol) in 200 mL of ethanol
dimethylglyoxime (11.6 g; 0.5 mol) in 200 mL of
ethanol was added, the mixture was heated on a water
bath for 0.5 h, and cooled. The precipitate was filtered
off on a Büchner funnel, washed with ethanol, and
dried (3 mmHg, 40°С). Yield 13 g (90%).
5
000.2 chromatograph with flame-ionization detector,
capillary column SGE BPX5 30 m, diameter 0.53 mm,
and on mass-spectrometer GCMS-QP-2010 Shimadzu.
ACKNOWLEDGMENTS
This work was performed under the contract no.
2
014/51 as a part of the basic section of the State
Program of the Ministry of Education and Science of
Russian Federation (project code 627).
Ni(II) compounds with 8-oxyquinoline, salicylald-
oxime, о-aminophenol were prepared similarly.
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