Aqua complex of iron(III) and 5-chloro-3-(2-(4,4-dimethyl-2,6- dioxocyclohexylidene) hydrazinyl)-2-hydroxybenzenesulfonate: Structure and catalytic activity in Henry reaction

Article abstract of DOI:10.1016/j.molstruc.2013.05.041

A water-soluble iron(III) complex [Fe(H₂O)₃(L)] ·5H₂O (1) was prepared by reaction of iron(III) chloride with 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl) -2-hydroxy-benzenesulfonic acid (H₃L

Full text of DOI:10.1016/j.molstruc.2013.05.041

Journal of Molecular Structure 1048 (2013) 108–112
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Aqua complex of iron(III) and 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocy-
clohexylidene)hydrazinyl)-2-hydroxybenzenesulfonate: Structure and
catalytic activity in Henry reaction
Kamran T. Mahmudov , Maximilian N. Kopylovich , Matti Haukka , Gunay S. Mahmudova a,b,
a,b
a,
⇑
c
b,d
b
a,
⇑
Espandi F. Esmaeila , Famil M. Chyragov , Armando J.L. Pombeiro
a
Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049–001 Lisbon, Portugal
Baku State University, Department of Chemistry, Z. Xalilov Str. 23, Az 1148 Baku, Azerbaijan
University of Jyväskylä, Department of Chemistry, P.O. Box 35, FI-40014 University of Jyväskylä, Finland
Independent Islam University, Garaj Filial, Tehran, Iran
b
c
d
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
New aqua soluble FeIII complex with arylhydrazone of 5,5-dimethylcyclohexane-1,3-dione.
Intermolecular charge-assisted halogen bonding.
The complex acts as a catalyst in the nitroaldol (Henry) reaction.
a r t i c l e i n f o
a b s t r a c t
Article history:
A water-soluble iron(III) complex [Fe(H O) (L)]Á5H O (1) was prepared by reaction of iron(III) chloride
2
3
2
Received 16 January 2013
Received in revised form 20 May 2013
Accepted 21 May 2013
with
5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxy-benzenesulfonic
L). The complex was characterized by IR, 1H NMR and ESI-MS spectroscopies, elemental and
3
acid (H
X-ray crystal structural analyses. The coordination environment of the central iron(III) is a distorted octa-
Available online 28 May 2013
3À
hedron, three sites being occupied by L ligand, which chelates in O,N,O fashion, while three other sites
are filled with the water molecules. The uncoordinated water molecules are held in the channels of the
Keywords:
3À
overall 3D supramolecular structure by the carbonyl and sulfonyl groups of L and the ligated waters.
Arylhydrazone of 5,5-dimethylcyclohexane-
Apart from the multiple hydrogen bonds, an intermolecular charge-assisted OÁÁÁCl halogen bonding with
1
,3-dione
3.044 Å distance was described. 1 acts as an effective catalyst in the Henry reaction producing nitroaldols
Water-soluble iron(III) complex
Halogen bonding
Henry reaction
from nitroethane and various aldehydes with yields up to 90% and threo/erythro diastereoselectivity
ranging from 3:1 to 1:1.
Crown Copyright Ó 2013 Published by Elsevier B.V. All rights reserved.
1
. Introduction
higher than those of metal complexes with simple b-diketones
[
2]. In spite of the fact that in solution iron(III) forms the most sta-
Arylhydrazones of b-diketones (AHBD) are versatile
ble complexes with AHBD ligands, only two such complexes were
isolated in solid state and structurally characterized [8]. It was
demonstrated that these complexes perform high catalytic activity
in peroxidative oxidation of cycloalkanes [8]. The catalytic activity
intermediates in organic chemistry [1]; the coordination chemistry
of AHBD is also of interest [2]. The AHBD ligands interact with
many metal ions in various fashions, thus allowing one to create
different confined and overall geometries in solution and in solid
phase. Different types of complexes can be easily prepared depend-
ing on the position of substituents in AHBD and on the nature of
metal ions [2–12]. It was demonstrated, that in solution the
stabilities of metal complexes with AHBDs increase in the order
III
of the complexes can be related to the fact that the central Fe ion
is, on the one hand, protected by the chelating AHBD ligand, and,
on the other hand, possesses labile sites with coordinated water
molecules [8]. Similar Zn(II) complexes were found to be catalyti-
cally active in another type of reaction, namely CAC bond forma-
tion [5]. Thus, it worth to extend a number of the structurally
characterized Fe(III)-AHBD complexes and check their catalytic
activity in other relevant reactions.
II
II
II
II
II
II
II
II
2
II
III
Ca < Mg < Mn < Cd < Zn < Co < Ni < UO < Cu < Fe and are
⇑
Corresponding authors.
E-mail addresses: kopylovich@yahoo.com (M.N. Kopylovich), pombeiro@ist.
utl.pt (A.J.L. Pombeiro).
The selective and efficient functionalization of CAH bonds has
attracted much attention from both academia and industry.
0
022-2860/$ - see front matter Crown Copyright Ó 2013 Published by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2013.05.041

K.T. Mahmudov et al. / Journal of Molecular Structure 1048 (2013) 108–112
109
Although great progress has been made in this area, more effective
processes for the construction of CAC bonds starting from CAH
bonds are still highly desirable. The synthesis of 2-nitroalcohols
from an enolizable nitroalkane and a carbonyl compound, known
as Henry or nitroaldol reaction, is an important synthetic tool for
the creation of CAC bond [13]. The development of new catalysts
and procedures for the Henry reaction has been constantly elabo-
rated in view of the reduction of toxic by-products and the increase
of yield and diastereoselectivity. Several organic and inorganic cat-
alysts have been described for the reaction [14–20], however, the
catalytic activity of Fe(III)-AHBD complexes has not yet been
reported.
Taking in mind all the above considerations, in this contribution
we describe the synthesis and structural details of the iron(III)
complex with 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylid-
3
ene)hydrazinyl)-2-hydroxybenzenesulfonic acid (H L) and evalu-
ate its activity and diastereoselectivity in production of 2-
nitroalcohols by the Henry reaction.
ments were carried out using SHELXL-97 [23]. The H
2
O hydrogen
atoms were located from the different Fourier map but constrained
to ride on their parent atom with Uiso = 1.5 Ueq(parent atom). Other
hydrogen atoms were positioned geometrically and constrained to
ride on their parent atoms with Uiso = 1.2–1.5 Ueq (parent atom).
The crystallographic details are summarized in Table 1. CCDC
919328 contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/da-
ta_request/cif.
2.4. General procedure for the reaction of nitroethane and various
aldehydes
The solvent (2 mL) was added to a flask which contained the
Fe(III) catalyst 1 (typically 3.01 mol%) and the mixture was agi-
tated for 5 min. Then aldehyde (1 mmol) and nitroethane (4 mmol)
were added and the reaction mixture was stirred for the appropri-
ate amount of time, after which the solvent was evacuated. The
residue was dissolved in DMSO-d6 and analyzed by 1H NMR
2
. Experimental
[
5,19]. The yield of b-nitroalkanol was related to the amount of
2
.1. Materials and instrumentation
aldehydes; the adequacy of this procedure was verified by blank
H NMR analyses with 1,2-dimethoxyethane as an internal refer-
ence. The threo and erythro isomers were distinguished from the
1
The H and 13C NMR spectra were recorded at room temperature
1
on a Bruker Avance II + 300 (UltraShield™ Magnet) spectrometer
operating at 300.130 and 75.468 MHz for proton and carbon-13,
respectively. The chemical shifts are reported in ppm using tetra-
values of vicinal coupling constants between the
the -OACAH protons, being J = 7–9 or 3.2–4 Hz for the threo or
erythro isomers, respectively [5,19].
a-NACAH and
a
methylsilane as the internal reference. The infrared spectra
À1
(
4000–400 cm ) were recorded on a BIO-RAD FTS 3000MX instru-
3
. Results and discussion
ment in KBr pellets. Carbon, hydrogen, and nitrogen elemental
analyses were done using a ‘‘2400 CHN Elemental Analyzer’’ by Per-
kin Elmer. Electrospray mass spectra (ESI-MS) were run with an
ion-trap instrument (Varian 500-MS LC Ion Trap Mass Spectrome-
ter) equipped with an electrospray ion source. For electrospray ion-
ization, 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 100 to 1200 in methanol solution. The
compounds were observed in the positive mode (capillary volt-
age = 80–105 V).
3.1. Synthesis and characterization of 1
The synthesis and characterization of 5-chloro-3-(2-(4,
-dimethyl-2,6-dioxocyclo-hexylidene)hydrazinyl)-2-hydroxyben-
4
zenesulfonic acid (H
be discussed herein. Treatment of Fe chloride hexahydrate with
L in water (pH 2) with the subsequent work-up led to the brown
compound [Fe(H O) O (1, Scheme 1) in 50% yield. The IR
(L)]Á5H
spectrum of 1 displays 3323 and 3082 (s, br) (OH), 1659 (s)
(C@O) and d(OH), 1562 (s) (C@N) lines, the peaks are significantly
shifted in relation to the spectrum of free ligand (3504 (OH), 3385
(NH), 1647 (C@O), 1597 (C@N)) [8]. The proton signals of the
3
L) was reported earlier [8] and hence will not
III
H
3
2
3
2
m
m
m
2.2. Syntheses of 1
m
m
m
m
About 373 mg (1 mmol) of H
pH 2), then 270 mg (1 mmol) of FeCl
temperature giving (after ca. 2 d) a brown precipitate of the prod-
uct. The precipitate was filtered off and recrystallized from ethanol
giving brown crystals suitable for X-ray structural analysis.
3
L was dissolved in 15 mL water
O was added at room
(
3
Á6H
2
Table 1
Crystal data and structure refinement for 1.
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
14 2 14
C H28ClFeN O S
[
Fe(H O)
2
3
(L)]Á5H
2
O(1). Yield, 50% (based on Fe). Calcd. for C14-
571.74
100(2)
0.71073
Triclinic
P 1ꢀ
H
2
(
28ClFeN O14S (M = 571.74): C 29.41, H 4.94, N 4.90. Found C
9.13, H 4.63, N 4.74. MS (ESI): m/z: 428.01 [M–8H
KBr), cm : 3323 and 3082 (s, br)
d(OH), 1562 (s)
2
+
2
O + H] . IR
(C@O) and
(C@N). 1H NMR (300.13 MHz, DMSO-d ) d: 1.06
).
À1
m
(OH), 1659 (s)
m
m
6
11.0372(19)
11.2243(19)
11.2715(17)
67.357(7)
78.198(7)
89.434(7)
1257.8(4)
2
CH
.3. X-ray measurements
The crystals of 1 was immersed in cryo-oil, mounted in a Nylon
3
, 4.11 CH
2
, 7.43–7.54 (2H, C
6
H
2
b (Å)
c (Å)
a
(°)
b (°)
(°)
2
c
3
Volume (Å )
Z
loop, and measured at the temperature of 100 K. The X-ray diffrac-
tion data was collected on a Bruker Smart Apex II [21] diffractom-
3
Density (mg/m )
1.510
Absorption coefficient
Goodness-of-fit on F2
Final R indices [I > 2sigma(I)]
R indices (all data)
0.854 mm-1
eter using Mo K
a
radiation (k = 0.71073 Å). The APEX2 program
1.021
R1 = 0.0421, wR2b = 0.0984
R1 = 0.0686, wR2 = 0.1112
1.274 and À0.318 e Å
a
package was used for cell refinements and data reductions. The
structures were solved by direct methods using the SHELXS-97 pro-
gram with the WinGX graphical user interface [22–24]. A semi-
empirical multi-scan absorption correction based on equivalent
reflections (SADABS) [25] was applied to all data. Structural refine-
À3
Largest diff. peak and hole
a
R1 =
wR2 = [
R
||F
R
o
| À |F
c o
||/R|F |.
b
2
2
2
[w(F ) ]]1/2.
2
o
2
[w(F À F ) ]/
R
o
c

1
10
K.T. Mahmudov et al. / Journal of Molecular Structure 1048 (2013) 108–112
Table 2
H O
2
H O
OH2
O
Hydrogen bond interactions in 1 (Å, °).
2
H C
H
3
2
O
C
D–HÁ Á ÁA
Distances (Å)
Angles (°)
D–HÁ Á ÁA
Fe
N
C
C
C
SO3
H C
3
D–H
HÁ Á ÁA
DÁ Á ÁA
H C
2
5H O
2
O(1S)AH(1W)Á Á ÁO(8)#1
O(1S)AH(1S)Á Á ÁO(6)#2
O(2S)AH(2W)Á Á ÁO(9)
O(2S)AH(2S)Á Á ÁO(1S)#3
O(3)AH(3O)Á Á ÁO(5S)
O(3)AH(3P)Á Á ÁO(1S)
0.85
0.84
0.84
0.84
0.85
0.86
0.83
0.83
0.88
0.86
0.87
0.85
0.86
0.86
0.85
0.84
0.85
1.85
1.88
1.88
1.86
1.80
1.81
2.25
2.61
2.64
1.84
1.86
2.04
1.93
1.87
1.85
2.02
2.10
2.692(3)
2.710(3)
2.726(3)
2.686(3)
2.654(4)
2.649(3)
2.847(4)
3.040(4)
3.140(4)
2.689(4)
2.723(4)
2.839(3)
2.788(3)
2.718(4)
2.671(3)
2.860(4)
2.919(4)
175.5
168.8
176.3
165.4
173.3
167.2
128.7
113.2
117.2
174.5
174.7
155.6
177.5
167.2
159.9
171.9
161.7
N
C
O
Cl
Scheme 1. Schematic representation of 1.
O(3S)AH(3W)Á Á ÁO(6)
O(3S)AH(3W)Á Á ÁO(1)
O(3S)AH(3S)Á Á ÁO(4S)#4
O(4)AH(4O)Á Á ÁO(2S)#5
O(4)AH(4P)Á Á ÁO(3S)
O(4S)AH(4W)Á Á ÁO(7)
O(4S)AH(4S)Á Á ÁO(7)#4
O(5)AH(5O)Á Á ÁO(4S)
O(5)AH(5P)Á Á ÁO(2S)#6
O(5S)AH(5W)Á Á ÁO(9)#7
O(5S)AH(5S)Á Á ÁO(3S)#2
Symmetry codes: #1 x,y + 1,z; #2 Àx,Ày + 1,Àz + 1; #3 x + 1,y,z; #4 Àx,Ày,Àz + 2; #5
x À 1,y,z; #6 Àx + 1,Ày + 1,Àz + 2; #7 Àx + 1,Ày + 1,Àz + 1
coordination environment of iron(III) is best described as a dis-
torted octahedron (4 + 2); three sites (O1N1O2) of the axial plane
3À
being occupied by the chelating L ligand while the coordinated
water molecules are in the forth axial site (O4) and two apical posi-
tions (O3O5). The FeAO bond lengths range from 1.910(2) to
2
.052(2) Å, whereas the Fe(1)AN(1) distance is 2.122(3) Å.
The coordinated water molecules are involved in the multiple
Fig. 1. Thermal ellipsoid plots, drawn at the 50% probability level, of the complex 1.
Selected bond lengths (Å) and angles (°): Fe(1)AO(1) 1.910(2), Fe(1)AO(2) 1.957(2)
Fe(1)AO(3) 2.025(3), Fe(1)AO(4) 2.035(2), Fe(1)AO(5) 2.052(2), Fe(1)AN(1)
hydrogen bonds with the non-coordinated water molecules
Fig. 2a). Thus, the [Fe(H O) (L)] units are associated in layers sep-
2
.122(3),
O(1)AFe(1)AN(1) 80.33(10), O(2)AFe(1)AN(1) 83.82(10), O(4)AFe(1)AN(1)
73.92(11).
O(1)AFe(1)AO(2)
164.11(10),
O(3)AFe(1)AO(5)
179.50(11),
(
2
3
arated by the water molecules. The packing structure is deter-
mined by coordination behavior of the water molecules, leading
to OAHÁ Á ÁO bonded zigzag strands which are further associated
1
by the edge-to-face aromatic interactions. The average H
2
OÁ Á ÁO
1
distances of the hydrogen bonds in 1 fall within the 2.649(3)–
.140(4) Å range (Table 2), consistent with formation of a strong
3
AOH and @NANHA groups of H L disappear in the H NMR spec-
3
trum of 1 thus indirectly confirming the complex formation. Ele-
hydrogen bonding [26,27]. The neighboring iron units are posi-
mental analysis and ESI-MS in methanol (peak at m/z 428.01 [M–
+
tioned in relative proximity to each other (FeÁ Á ÁFe separation of
8
H
2
O + H] ) support the proposed formulation of 1 as a monomer,
5
.812 Å) as result of their linkage via strong H-bonds. The overall
the common composition for many AHBD complexes [2].
The molecular structure of 1 has been established by single-
crystal X-ray diffraction which discloses the chelating coordination
structure can be described as a 3D network with channels, in
which the solvate water molecules are interconnected with car-
bonyl and sulfonyl oxygen atoms of the L ligands and the coordi-
nated water molecules. In accord with geometry of the complex,
the channels incorporating the coordinated water have a nearly
3À
3
À
of the basic L ligand (Scheme 1, Fig. 1). The positive charge of the
III
Fe ion is compensated by the negative charges of the deproto-
3À
nated N1, O4 and O7 (from the sulfo group) atoms of L . The
Fig. 2. Intermolecular hydrogen (a) and halogen (b) bonding in 1. Hydrate water molecules are omitted for clarity in b.

K.T. Mahmudov et al. / Journal of Molecular Structure 1048 (2013) 108–112
111
OH
OH
catalyst
R
CHO +
NO2
R
+
R
NO2
NO2
threo
erythro
Scheme 2. Formation of nitroaldols by the Henry reaction.
Table 3
Catalytic activity of 1 in Henry reaction.
a
Entry
Catalyst
Time (h)
Amount of catalyst (mol%)
Temp. (°C)
Solvent
Yield (%)b
Selectivityc threo/erythro
1
2
3
4
5
6
7
8
9
0
1
2
3
1
1
1
24
24
24
24
24
24
24
24
5
10
15
24
24
2.0
2.0
2.0
À
20
20
20
20
20
20
20
20
20
20
20
35
45
H
MeOH
MeCN
2
O
88.1
77.0
52.1
À
72:28
64:36
49:51
À
Blank
FeCl3
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
O
O
O
O
O
O
O
O
O
O
1.0
1.0
3.0
4.0
3.0
3.0
3.0
3.0
3.0
À
À
1
1
1
1
1
1
1
1
76.7
90.2
90.4
41.4
57.5
68.3
92.3
94.6
72:28
73:27
72:28
72:28
73:27
73:27
73:27
74:26
1
1
1
1
a
Reaction conditions: 1.0–4.0 mol% (0.1–0.4
1 mmol).
2
lmol) of catalyst precursor (typically 3 mol%), solvent (H O, MeOH, MeCN) (2 mL), nitroethane (4 mmol) and benzaldehyde
(
b
Determined by 1H NMR analysis.
c
Calculated by 1H NMR.
Table 4
Henry reaction of various aldehydes and nitroethane with catalyst 1.
amount, time, temperature and solvent (Table 3). The reaction was
carried out at room temperature in different solvents such as
water, methanol and acetonitrile (Table 3, entries 1–3). Surpris-
ingly, the use of water as a solvent (entry 1) gave high yields up
to 88%, and good diastereoselectivity (72:28, threo:erythro), the re-
sults better than those in methanol and acetonitrile. Possibly this is
related to the tighter ion pairing in the course of reaction [5] and
higher solubility of 1 in water. No reaction was observed in the ab-
sence of 1 (entries 4 and 5), while the increase of the catalyst
amount enhances the product yield (from 76% to 90% for the
respective amounts of 1 and 4 mol% of catalyst 1) with similar dia-
stereoselectivities (entries 1,6–8). The increase of reaction time led
to higher conversions (entries 7 and 9–11). The heating in the 20–
a
Yield (%)b
Threo/erythro ratioc
Entry
1
Substrate
90.2
73:27
2
3
4
93.4
82.5
81.6
75:25
71:29
72:28
4
5 °C range gave no significant improvement in productivity, and
only small change of yield (from 90.2% to 94.6% for 24 h reaction
time) was observed (entries 7, 12, and 13).
5
6
CH
CH
3
CHO
CH CHO
92.1
87.9
73:27
70:30
Having the reaction conditions optimized, we investigated the
reactivity of a variety of aldehydes, and the appropriate 2-nitroal-
cohols were generally obtained in good yields (Table 4). The deriv-
3
2
a
Reaction conditions: 3.0 mol% of catalyst 1, water (2 mL), nitroethane (4 mmol)
and benzaldehyde (1 mmol), reaction time: 24 h.
b
c
1
Determined by H NMR analysis (see Section 2).
ative of benzaldehyde with an electron-withdrawing para-NO
group was more reactive than that with an electron-donating
para-OCH substituent (entries 2 and 3). In the case of 2-methyl-
2
Calculated by 1H NMR.
3
quadratic cross-section, whereas those containing the hydrate
water molecules have an elongated profile.
It should be noted, that a strong charge-assisted halogen bond is
formed between an oxygen atom of the sulfo group and the chlo-
benzaldehyde, the lowest yield was observed (entry 4), probably
due to some steric hindrance. It should be noted that 1 can readily
catalyze the nitroaldol addition of nitroethane to aliphatic alde-
hydes such as acetaldehyde and propionaldehyde (entries 5 and
3À
rine atom of L with O(8)Á Á ÁCl(1) distance of 3.044 Å (Fig. 2b),
6
). As can be seen, the nature of substrates generally influences
which is typical for this type of bonding [28,29]. As result, the
the yields but not diastereoselectivities.
[
Fe(H
2 3
O) (L)] units are additionally interconnected by the halogen
We believe the reaction mechanism is similar to the previously
proposed one [5,30–32], and involves the following key steps: (a) 1
behaves as a Lewis acid and activates both nitroethane (increasing
its acidity) and aldehyde (increasing its electrophilic character); (b)
the AHBD ligand performs a Brönsted base function promoting the
deprotonation of the acidic nitroethane with formation of the reac-
tive nitronate species which adds to the ligated benzaldehyde via a
bonds in chains along the a-plane.
3
.2. Catalytic activity of 1 in Henry reaction
Firstly, we examined the reaction of benzaldehyde and nitroe-
thane (Scheme 2) in the presence of catalyst 1, varying the catalyst

1
12
K.T. Mahmudov et al. / Journal of Molecular Structure 1048 (2013) 108–112
nucleophilic intramolecular attack with formation of a CAC bond
to give a b-nitroalkanol.
[4] M.N. Kopylovich, A.C.C. Nunes, K.T. Mahmudov, M. Haukka, T.C.O. Mac Leod,
Dalton Trans. 40 (2011) 2822.
[
[
[
[
[
5] M.N. Kopylovich, T.C.O. Mac Leod, K.T. Mahmudov, M.F.C. Guedes da Silva, A.J.L.
Pombeiro, Dalton Trans. 40 (2011) 5352.
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A.J.L. Pombeiro, Eur. J. Inorg. Chem. 27 (2011) 4175.
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4
. Conclusions
Novel iron(III) complex [Fe(H
prepared by reaction of iron(III) chloride with 5-chloro-3-(2-(4,4-
dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxy-ben-
2
O)
3
(L)]Á5H
2
O (1) was easily
3
zenesulfonic acid (H L). 1 was isolated in solid state and fully
structurally characterized, reveling its monomeric structure with
iron(III) being in distorted octahedral coordination environment,
where three coordinative positions are occupied by a nitrogen
[10] M.N. Kopylovich, M.J. Gajewska, K.T. Mahmudov, M.F.C. Guedes da Silva, M.V.
Kirillova, P.J. Figiel, J. Sanchiz, A.J.L. Pombeiro, New J. Chem. 36 (2012) 1646.
[
[
11] M.N. Kopylovich, M.F.C. Guedes da Silva, Polyhedron 50 (2013) 374.
12] M.N. Kopylovich, K.T. Mahmudov, M. Haukka, K.V. Luzyanin, A.J.L. Pombeiro,
Inorg. Chim. Acta 374 (2011) 175.
atom of hydrazone, alkoxy and carbonyl oxygen atoms of the che-
lating L3À ligand and three other – by the coordinated water mol-
[13] C.C.C. Johansson, T.J. Colacot, Angew. Chem. Int. Ed. 49 (2010) 676.
[
14] M.N. Kopylovich, A. Mizar, M.F.C. Guedes da Silva, T.C.O. Mac Leod, K.T.
Mahmudov, A.J.L. Pombeiro, Chem. A Eur. J. 19 (2013) 588.
ecules. The charge-assisted halogen bonding with distance of
OÁ Á ÁCl 3.044 Å is found in the supramolecular structure of 1. 1
was successfully applied as a green catalyst for the diastereoselec-
tive Henry reaction in water with good yields and diastereoselec-
tivities for both aromatic and aliphatic aldehydes.
[15] M.D. Jones, C.J. Cooper, M.F. Mahon, P.R. Raithby, D. Apperleyc, J. Wolowska, D.
Collison, J. Mol. Catal. A Chem. 325 (2010) 8.
[
[
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Chem. Soc. 125 (2003) 12692.
[
[
18] G.Q. Zhang, E. Yashima, W.D. Woggon, Adv. Synth. Catal. 351 (2009) 1255.
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Mahmudov, A.J.L. Pombeiro, Dalton Trans. 42 (2013) 399.
Acknowledgements
[
[
20] B.M. Trost, V.S.C. Yeh, Angew. Chem. Int. Ed. Engl. 41 (2002) 861.
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This work has been partially supported by the Foundation for
Science and Technology (FCT), Portugal (PEst-OE/QUI/UI0100/
[
2
011 project, and ‘‘Science 2007’’ program), as well as the Baku
State University, Azerbaijan.
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