Mononuclear nickel(II) complexes with arylhydrazones of acetoacetanilide and their catalytic activity in nitroaldol reaction

Article abstract of DOI:10.1016/j.ica.2017.09.037

The new mononuclear nickel(II) complexes [Ni(HL¹)(H₂O)₂(CH₃OH)] (1, NaH₂L¹ = sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzenesulfonate) and [Ni(H₂L

Full text of DOI:10.1016/j.ica.2017.09.037

Inorganica Chimica Acta 469 (2018) 197–201
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
Mononuclear nickel(II) complexes with arylhydrazones of
acetoacetanilide and their catalytic activity in nitroaldol reaction
Atash V. Gurbanov a,b,c, Fatali E. Huseynov , Ghodrat Mahmoudi , Abel M. Maharramov ,
c,d
e
b
a
a,c,d,
⇑
a,
⇑
Fátima C. Guedes da Silva , Kamran T. Mahmudov
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
Organic Chemistry Department, Baku State University, Z. Xalilov Str. 23, Az 1148 Baku, Azerbaijan
Organic Chemistry Department, RUDN University, 6 Miklukho-Maklaya Str., Moscow 117198, Russian Federation
Department of Ecology and Soil Sciences, Baku State University, Z. Xalilov Str. 23, Az 1148 Baku, Azerbaijan
Department of Chemistry, Faculty of Science, University of Maragheh, P.O. Box 55181-83111, Maragheh, Iran
, Armando J.L. Pombeiro
a
b
c
d
e
a r t i c l e i n f o
a b s t r a c t
1
1
Article history:
Received 30 July 2017
Accepted 13 September 2017
Available online 18 September 2017
The new mononuclear nickel(II) complexes [Ni(HL )(H O) (CH OH)] (1, NaH L = sodium (Z)-2-(2-(1,3-
2
2
3
2
2
dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzenesulfonate)
(CH ) S@O) ] (2, H L = (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzoic acid)
3 2 2 3
were synthesized and characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal struc-
and
2 2 2 4
[Ni(H L ) (H O) ]
2
[
tural analyses. Both compounds 1 and 2 act as homogenous catalysts for the diastereoselective nitroaldol
Keywords:
Ni(II) complexes
Arylhydrazones of acetoacetanilide
Henry reaction
(Henry) reaction of aliphatic and aromatic aldehydes with nitroethane in different solvents such as ace-
tonitrile, methanol or water. Complex 1 was found to be the more efficient catalyst for the Henry reaction
in aqueous medium, providing b-nitroalcohols with good yields (67–82%) and diastereoselectivities (syn/
anti 59:41–70:30).
Ó 2017 Elsevier B.V. All rights reserved.
1
. Introduction
The use of nickel complexes as catalysts in homogeneous catal-
wave conditions [8] or in ionic liquids [9]. Thus, the search for effi-
cient and environmentally friendly homogenous protocol for CAC
coupling of nitroethane with aldehydes is still highly desirable.
Hence, on the basis of the above considerations, we focused this
work on the following aims: i) to synthesize new Ni(II)-arylhydra-
ysis has received much attention in recent years [1,2]. Interest-
ingly, the catalytic properties of nickel complexes can be
manipulated and tuned by selecting organic ligands [1,2]. Our
group has been interested in exploring the catalytic applications
of transition metal complexes of arylhydrazone ligands in the oxi-
dation or CAC coupling reaction [3]. Whereas, several Ni(II)-aryl-
hydrazone complexes are reported [3], their catalytic behavior
for CAC coupling reaction has not been investigated. Herein, we
report the synthesis and structural characterization of two
mononuclear Ni-arylhydrazone complexes and their use as the cat-
alysts in CAC coupling reaction of nitroethane with aldehydes
1
1
zone complexes, [Ni(HL )(H
2 2 3 2
O) (CH OH)] (1, NaH L = sodium (Z)-
2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)ben-
2
2
2 2 2 4 3 2 2 3
zenesulfonate) and [Ni(H L ) (H O) ] [(CH ) S@O) ] (2, H L = (Z)-
2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)ben-
zoic acid); ii) to evaluate the catalytic activity of the prepared new
Ni(II) complexes in the Henry reaction.
2. Experimental
(
Henry reaction). To the best of our knowledge, in comparison to
Cu(II) complexes [4], only limited numbers of nickel(II) complexes
have been applied in the Henry reaction under different conditions,
namely in homogeneous systems [5–7], under solvent free micro-
2.1. Materials and instrumentation
All the chemicals were obtained from commercial sources
1
2
(
2 3
Aldrich) and used as received. The NaH L and H L were synthe-
sized according to the reported procedures [10,11]. Infrared spec-
tra (4000–400 cm ) were recorded on a Vertex 70 (Bruker)
⇑
Corresponding authors at: Centro de Química Estrutural, Instituto Superior
Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal (K.T.
Mahmudov).
ꢀ1
instrument in KBr pellets. Carbon, hydrogen, and nitrogen elemen-
tal analyses were done using a ‘‘2400 CHN Elemental Analyzer”
E-mail addresses: kamran_chem@yahoo.com, kamran_chem@mail.ru (K.T.
Mahmudov), pombeiro@tecnico.ulisboa.pt (A.J.L. Pombeiro).
1
13
(Perkin Elmer). The H and C NMR spectra were recorded at room
http://dx.doi.org/10.1016/j.ica.2017.09.037
0
020-1693/Ó 2017 Elsevier B.V. All rights reserved.

1
98
A.V. Gurbanov et al. / Inorganica Chimica Acta 469 (2018) 197–201
temperature on a Bruker Avance II + 300 (UltraShieldTM Magnet)
spectrometer operating at 300.130 and 75.468 MHz for proton
and carbon-13, respectively. The chemical shifts are reported in
ppm using tetramethylsilane as the internal reference. Electro-
spray mass spectra (ESI-MS) were run with an ion-trap instrument
Table 1
Crystallographic data and structure refinement details for 1 and 2.
1
2
Empirical formula
fw
Temperature (K)
Cryst. Syst.
Space group
a (Å)
C
17
H
21
N
3
8
NiO S
C
38 48 6 2
H N NiO14S
486.14
296(2)
935.65
100(2)
Orthorhombic
Pbca
19.7783(9)
9.6876(5)
22.0023(10)
90
90
90
4215.7(3)
4
1.474
(
Varian 500-MS LC Ion Trap Mass Spectrometer) equipped with an
Monoclinic
P 21/n
14.471(4)
7.838(2)
18.439(6)
90
92.048(11)
90
2090.1(10)
4
1.545
1.077
1008
0.0284
0.0684
1.081
electrospray ion source. For electrospray ionization, the drying gas
and flow rate were optimized according to the particular sample
with 35 p.s.i. nebulizer pressure. Scanning was performed from
m/z 0 to 1100 in methanol solution. The compounds were observed
in the positive mode (capillary voltage = 80–105 V).
b (Å)
c (Å)
a
, °
b, °
, °
c
1
2
.2. Synthesis of [Ni(HL )(H
O)
2 2
3
(CH OH)] (1)
3
V (Å )
Z
L1 were dissolved in 20 mL of metha-
COO) 4H O were added. The
ꢀ3
0
.1 mmol (38 mg) of NaH
2
qcalc (g cm
)
ꢀ
1
l(Mo K ) (mm
a
)
0.633
1960
0.0774
0.1954
1.207
nol, then 0.1 mmol (25 mg) of Ni(CH
3
2
2
F (0 0 0)
mixture was stirred for 5 min and left for slow evaporation. Green-
ish crystals of the product started to form after ca. 2 d at room tem-
perature; they were filtered off and dried in air.
a
R1 (I ꢁ 2
r
)
b
wR2 (I ꢁ 2
r)
GOOF
1
: Yield, 52% (based on Ni). Calcd. for C17
H
21
N
3
NiO
8
S (Mr.
a
R1 =
wR2 = [
R
||F
R
o c o
| – |F ||/R|F |.
=
486.12): C 42.00, H 4.35, N 8.64; found C 41.92, H 4.17, N 8.57.
b
2
2
2
[w(F2
)2]]1/2.
[w(F
o
– F
c
) ]/
R
o
+
MS (ESI, positive ion mode), m/z: 455.06 [MrꢀCH
3
OH + H] . IR
(
m
KBr): 3380 (s, br)
m
(OH), 3118 m(NH), 1676 (s) m(C@O), 1598 (s)
–
1
(C@N) cm
.
Table 2
Selected bond distances (Å) and angles (°) for 1 and 2.
2
2
.3. Synthesis of [Ni(H
2
L )
2
(H
2
O)
4
] [(CH
3 2 2
) S@O) ] (2)
1
2
Ni1ꢀO1
1.9847 (15)
2.0550 (15)
2.0445 (17)
2.0848 (17)
2.0700 (16)
2.0302 (18)
89.79 (6)
94.15 (6)
90.76 (7)
175.54 (7)
92.78 (6)
89.46 (6)
92.97 (6)
177.04 (6)
87.98 (7)
84.54 (6)
85.49 (7)
92.09 (7)
177.13 (6)
90.77 (6)
89.19 (7)
Ni1–O1
Ni1–O1
Ni1–O5
Ni1–O5
Ni1–O6
Ni1–O6
2.036 (3)
2.036 (3)
2.080 (3)
2.080 (3)
2.061 (3)
2.061 (3)
180.0
91.05 (12)
88.95 (12)
88.95 (12)
91.05 (12)
180.0
93.57 (11)
86.43 (11)
89.28 (11)
90.72 (11)
86.43 (11)
93.57 (11)
90.72 (11)
89.28 (11)
180.0
0
.1 mmol (37 mg) of H
3
L2 were dissolved in 25 mL of methanol,
COO) 4H O were added and the
0
0
0
Ni1ꢀO4
then 0.1 mmol (25 mg) of Ni(CH
3
2
2
Ni1ꢀO5
Ni1–O6
system was stirred for 10 min. After ca. 3 d at room temperature,
greenish crystals precipitated, which were then filtered off and
dried in air.
Ni1–O8
Ni1–N3
O1–Ni1ꢀN3
O1–Ni1ꢀO5
N3–Ni1ꢀO5
O1–Ni1ꢀO4
N3–Ni1ꢀO4
O5–Ni1ꢀO4
O1–Ni1ꢀO8
N3–Ni1ꢀO8
O5–Ni1ꢀO8
O4–Ni1ꢀO8
O1–Ni1ꢀO6
N3–Ni1ꢀO6
O5–Ni1ꢀO6
O4–Ni1ꢀO6
O8–Ni1ꢀO6
O1–Ni1ꢀO1
O1–Ni1ꢀO6
O1–Ni1ꢀO6
O1–Ni1ꢀO6
O1–Ni1ꢀO6
O6–Ni1ꢀO6
O1–Ni1ꢀO5
O1–Ni1ꢀO5
O6–Ni1ꢀO5
O6–Ni1ꢀO5
O1–Ni1ꢀO5
O1–Ni1ꢀO5
O6–Ni1ꢀO5
O6–Ni1ꢀO5
O5–Ni1ꢀO5
2
: Yield, 48% (based on Ni). Calcd. for C38
H
48
N
6
NiO14
S
2
(Mr.
0
0
=
935.64): C 48.78, H 5.17, N 8.98; found C 48.67, H 5.06, N 8.79.
+
MS (ESI, positive ion mode), m/z: 780.36 [Mrꢀ2(CH
3 2
) S@O + H] .
IR (KBr): 3437 (s, br) (OH), 3212 (NH), 1669 (s) (C@O), 1611 m
m
m
m
–
1
(
C@N) cm .
0
2
.4. Crystal structure determination
0
0
X-ray diffraction patterns of 1 and 2 were collected using a Bru-
ker SMART APEX-II CCD area detector equipped with graphite-
monochromated Mo-K radiation (k = 0.71073 Å) at room temper-
a
ature. Absorption correction was applied by SADABS [12,13]. The
structure was solved by direct methods and refined on F2 by full-
matrix least-squares using Bruker’s SHELXTL-97 [14]. All non-
hydrogen atoms were refined anisotropically. The details of the
crystallographic data, selected bond distances and angles for 1
and 2 are summarized in Tables 1 and 2. Crystallographic data
for the structural analysis have been deposited to the Cambridge
Crystallographic Data Center (CCDC 1564002 for 1 and 1564001
for 2). Copy of this information can be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax:
to the aldehyde) and the ratio between syn and anti isomers were
established by H NMR as reported previously [11,15–17]. The ade-
quacy of this procedure was proved by blank H NMR analyses
with 1,2-dimethoxyethane as an internal reference.
1
1
3. Results and discussion
(
+44) 1223–336033; E-mail: deposit@ccdc.cam.ac.uk or www.
3.1. Synthesis and characterization of 1 and 2
ccdc.cam.ac.uk/data_request/cif).
The known NaH
2
L1 and H
3
L2 were prepared according to our
1
2.5. General procedure for the study of catalytic activity
3 2 2 2
earlier works [10,11]. Reaction of Ni(CH COO) 4H O with NaH L
2
or H
3
L in methanol in the absence or presence of dimethylsulfox-
1
To a 10 mL vial were added the catalyst (1.0–4.0 mol%) and
ide led to the mononuclear Ni(II) complexes [Ni(HL )(H
OH)] (1) or [Ni(H L ) (H O) ] [(CH ) S@O) ] (2), respectively
2 2 3
O) (CH -
2
2
2
mL solvent (H O, MeOH or MeCN) and the solution was stirred
2 2 2 4 3 2 2
for 2 min at room temperature. Then, the aldehyde (1 mmol) and
nitroethane (4 mmol) were added and the resulting transparent
homogeneous solution was stirred at room temperature for the
appropriate time. After evaporation of the solvent, the residue
(Scheme 1). These complexes were characterized by both X-ray
structural determination and spectroscopic methods. In the IR
spectra of 1 and 2, the
m(C@O) and m(C@N) signals appear at
–
1
1676 and 1598, 1669 and 1611 cm , respectively, values that are
was dissolved in CDCl
lyzed by H NMR. The yield of the b-nitroalkanol product (relative
3
and this blurry solution filtrated, then ana-
significantly shifted in relation to the corresponding signals of
NaH L or H L [10,11]. Mass spectrometry of a methanol solution
2 3
1
1
2

A.V. Gurbanov et al. / Inorganica Chimica Acta 469 (2018) 197–201
199
and the hydrazone hydrogen atoms participate in intramolecular
RAHB system, O3C8C7N2N1H(N1) (Fig. 1). This can conceivably
be due to the involvement of coordinated carboxylic group in the
intra- and intermolecular hydrogen bonding. Generally, both com-
pounds present inter- and intramolecular noncovalent interactions
[
19] involving the NH, sulfonic, carboxylic groups as well as aro-
matic moieties of coordinated ligands (Fig. 2). In addition, the
dimethylsulfoxide molecule in 2 contacts with coordinated water
molecules and donor (CaromaticAH) or acceptor (Ccarboxylic@O) moi-
2
2 ꢀ
eties of (H L ) (Fig. 2).
Scheme 1. Schematic representation of 1 and 2.
3.2. Catalytic activity of 1 and 2 in the Henry reaction
of 1 and 2 shows relevant peaks at m/z = 455.06 [MrꢀCH
3
OH + H]+
Initially, benzaldehyde was chosen as a test substrate to deter-
+
(
for 1) and 780.36 [Mrꢀ2(CH
3
)
2
S@O + H] (for 2). Elemental analy-
mine the best conditions for the Henry reaction with nitroethane
to afford the corresponding b-nitroalcohol, i.e. (1R,2R)- or (1R,2S)-
2-nitro-1-phenylpropan-1-ol (Scheme 2). During the first step in
the optimization of the reaction conditions, the catalyst and sol-
vent effects were examined and the observed results are summa-
rized in Table 3. The obtained results clearly shows that the
reaction is highly sensitive to the nature of the solvent employed
and water is the best reaction media in terms of yield and diaste-
rioselectivity (Table 3). Thus, catalyst 1 behaves as the most active
ses and X-ray crystallography are also in agreement with the pro-
posed formulations.
In both crystal structures, the nickel ion has a distorted octahe-
dral coordination geometry with the chelating hydrazone and
water (or methanol in the case of 1) ligands occupying the four
equatorial positions and the apical sites being engaged with the
water molecules (Fig. 1). Despite the fact that a nickel(II) acetate
were used for the synthesis of 1 and 2, the resonance assisted
2
2 ꢀ
1
hydrogen bond (RAHB) system [18] was not destroyed in (H L )
and diastereoselective catalyst among Ni(CH COO) ꢂ4H O, NaH L ,
3
2
2
2
Fig. 1. Molecular structures of 1 and 2.
Fig. 2. Packing structures of 1 and 2. Noncovalent interactions are shown as dashed blue lines. In 2 H atoms are omitted. Symmetry codes to generate equivalent atoms: (1) i)
x, y, z; ii) ꢀx, ꢀy, ꢀz; (2) i) x, y, z; ii) ꢀx, ꢀy, ꢀz.

2
00
A.V. Gurbanov et al. / Inorganica Chimica Acta 469 (2018) 197–201
in temperature led to decrease of yield and diasteroselectivity
entries 8, 10–12, Table 4). From the observed results, higher
(
chemical yield and diasteroselectivity were obtained at room tem-
perature (entry 8, Table 4). Due to poor solubility of 1 in
nitroethane (solvent-free conditions, entry 13), a lower yield
(
49%) was observed.
Scheme 2. The nitroaldol (Henry) reaction.
Next, based on the above optimized results, we tested a variety
3 2 3 3 2
of para-substituted [N(CH ) , OCH , CH , Cl and NO ] aromatic and
H
3
L2, 1 and 2 in the water medium as well as under catalyst- and
aliphatic aldehydes to determine the generality of the method, in
water at room temperature (Table 5). Thus, the electron-withdraw-
ing substituents on the phenyl ring of the aromatic aldehydes
favour the reaction, whereas electron-donating ones decrease the
yield of b-nitroalcohols (entries 1–6, Table 5). To test the electronic
and steric effects of the substrate on the reaction, aromatic aldehy-
des such as 2-nitrobenzaldehyde, 2-methylbenzaldehyde and
2,4,6-trimethylbenzaldehyde as the substrates (entries 7–9,
Table 3) were employed. The slight decrease on the yields for the
ortho-nitro or -methyl benzaldehyde relative to those for the
solvent-free conditions (entry 16, Table 3). In the next step, to
establish the optimized conditions, the variations of catalyst
amount, reaction time and temperature were studied using 1 as
a catalyst in water (Table 4). The increase of reaction time from
0
.5 h to 24 h led to higher conversion (entries 1–5, Table 4), how-
ever the 5 h appears to be the optimal reaction time. The variation
of the catalyst amount (entries 6–9, Table 4) allowed to conclude
that 3 mol% loading is optimal for the given reaction conditions
and thus this amount was used for the further studies. The increase
Table 3
a
Catalyst screening and optimization.
Entry
1b
Catalyst
Blank
Solvent
Yield, %c
Selectivity, syn/antid
No solvent
ꢀ
ꢀ
2
3
4
Blank
MeCN
MeOH
H O
2
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
5
6
7
Ni(CH
3
COO)
2
ꢂ4H
2
O
MeCN
MeOH
ꢀ
ꢀ
5
60:40
62:38
H
2
O
6
8
9
1
NaH
2
L1
MeCN
MeOH
H O
2
9
27
39
57:43
60:40
60:40
0
1
1
1
1
2
3
H
1
2
3
L2
MeCN
MeOH
H O
2
5
26
35
59:41
59:41
60:40
14
15
16
MeCN
MeOH
H O
2
33
47
62
62:38
63:37
69:31
17
18
19
MeCN
MeOH
H O
2
29
36
51
61:39
63:37
69:31
a
Reaction conditions: catalyst precursor: Ni(CH
3
COO)
2
ꢂ4H
2 2 2
O, NaH L, 1 and 2 (1.0 mol%), acetonitrile, methanol or H O (2 mL), nitroethane (4 mmol) and benzaldehyde
(
1 mmol), reaction time: 24 h, reaction temperature: 20 °C.
b
Solvent-free conditions, using nitroethane as solvent (2 mL).
c
1
Determined by H NMR, based on the starting benzaldehyde.
d
Calculated by 1H NMR (see Experimental).
Table 4
Optimization of the Henry reaction condition catalyzed by 1.a
Entry
Time, h
Amount of catalyst, mol%
Temp., °C
Yield, %b
Selectivity, syn/antic
1
2
3
4
5
6
7
8
9
1
1
1
1
0.5
1
3
5
24
5
5
5
5
5
1.0
1.0
1.0
1.0
1.0
1.0
2.0
3.0
4.0
3.0
3.0
3.0
3.0
20
20
20
20
20
20
20
20
20
35
55
75
20
27
35
29
62
62
62
69
74
74
74
73
70
49
68:32
68:32
69:31
69:31
69:31
69:31
70:30
70:30
70:30
71:29
64:36
59:41
61:39
0
1
2
3
5
5
5
d
a
b
c
Reaction conditions: 1.0–4.0 mol% of catalyst precursor (typically 3.0 mol%), H
2
O (2 mL), nitroethane (4 mmol) and aldehyde (1 mmol).
1
Determined by H NMR analysis (see Experimental).
Calculated by 1H NMR.
d
Solvent-free conditions, using nitroethane as solvent (2 mL).

A.V. Gurbanov et al. / Inorganica Chimica Acta 469 (2018) 197–201
201
Table 5
The work was also supported by the Ministry of Education and
Science of the Russian Federation (Agreement number 02.
a03.21.0008). GM acknowledges to the University of Maragheh
for the financial support of this research. Authors are thankful to
the Portuguese NMR Network (IST-UL Centre) for access to the
NMR facility and the IST Node of the Portuguese Network of
mass-spectrometry for the ESI-MS measurements.
a
Henry reaction of nitroethane with various aldehydes catalyzed by 1.
Entry
Substrate
Yield, %b
Selectivity, syn/antic
1
2
3
4
5
6
7
8
9
4-(Dimethylamino)benzaldehyde
4-Methoxybenzaldehyde
4-Methylbenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
4-Nitrobenzaldehyde
2-Nitrobenzaldehyde
2-Methylbenzaldehyde
2,4,6-Trimethylbenzaldehyde
Propionaldehyde
67
71
72
74
76
80
73
73
70
82
81
81
69:31
69:31
70:30
70:30
69:31
71:29
69:31
69:31
66:34
74:26
73:27
73:27
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Reaction conditions: 3.0 mol% of catalyst 1, H
2
O (2 mL), nitroethane (4 mmol)
and aldehyde (1 mmol), reaction time: 5 h.
b
c
1
Determined by H NMR analysis (see Experimental part).
Calculated by 1H NMR.
[
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Two new mononuclear Ni(II) complexes bearing an ortho-sul-
fonate (in 1) or ortho-carboxylate (in 2) functionalized arylhydra-
zone of acetoacetanilide have been synthesized and
characterized. In both crystal structures, the nickel ion has a dis-
torted octahedral coordination geometry. These Ni(II)-arylhydra-
zone complexes catalyze the Henry reaction between nitroethane
and various aromatic and aliphatic aldehydes, providing in an
efficient and simple method the desired b-nitroalkanols in moder-
ate to good yields (up to 82%) and syn/anti diastereoselectivities
[
[
[
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2
(
up to 74:26%) in water at room temperature.
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Acknowledgements
Authors are grateful to the Fundação para a Ciência e a Tecnolo-
gia: (project UID/QUI/00100/2013), Portugal, for financial support.