Copper(II) complexes with an arylhydrazone of methyl 2-cyanoacetate as effective catalysts in the microwave-assisted oxidation of cyclohexane

Article abstract of DOI:10.1016/j.ica.2017.12.001

Reaction of sodium (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzene-sulfonate (NaHL) with copper(II) nitrate hydrate in the presence of imidazole (im) in methanol affords [CuL(im)(H₂O)] (1). Complex 1 is characterized by IR spec

Full text of DOI:10.1016/j.ica.2017.12.001

Inorganica Chimica Acta 471 (2018) 658–663
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Research paper
Copper(II) complexes with an arylhydrazone of methyl 2-cyanoacetate
as effective catalysts in the microwave-assisted oxidation of cyclohexane
Raja Jlassi a,b, Ana P.C. Ribeiro a, , Elisabete C.B.A. Alegria a,c, , Houcine Naïli b, , Gonçalo A.O. Tiago a,
⇑
⇑
⇑
Tobias Rüffer d, Heinrich Lang d, Fedor I. Zubkov e, Armando J.L. Pombeiro a, Walid Rekik b
a Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
b Laboratoire de physico-chimie de l’Etat Solide, Département de Chimie, Faculté des Sciences de Sfax, Université de Sfax, BP 1171, 3000 Sfax, Tunisia
c Chemical Engineering Departament, ISEL-Instituto Superior de Engenharia de Lisboa, Instituto Politecnico de Lisboa, 1959-007 Lisboa, Portugal
d Technische Universität Chemnitz, Fakultät für Naturwissenschaften, Institut für Chemie, Anorganische Chemie, D-09107 Chemnitz, Germany
e Organic Chemistry Department, RUDN University, 6 Miklukho-Maklaya str., Moscow 117198, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 12 October 2017
Received in revised form 28 November 2017
Accepted 1 December 2017
Available online 5 December 2017
Reaction of sodium (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzene-sulfonate
(NaHL) with copper(II) nitrate hydrate in the presence of imidazole (im) in methanol affords [CuL(im)
(H2O)] (1). Complex 1 is characterized by IR spectroscopy and ESI-MS spectrometry, elemental and single
crystal X-ray crystal structural analyses. The coordination environment of the central copper(II) is nearly
intermediate between ideal square-based pyramidal and trigonal bipyramidal geometry, three sites being
occupied by the L2À ligand, which chelates in the O, N, O fashion, while two other sites are filled with the
water and imidazole molecules. Extensive intermolecular hydrogen bonds between the L2À, water and
imidazole ligands lead to a 3D supramolecular network. 1 and known Cu(II) complexes [Cu(H2O)2L]Á
H2O (2), [Cu(H2O)(py)L]ÁH2O (3) and [Cu3(m3-OH)(NO3)(CH3OH)(m2-X)3(m2-HL)] (4) act as effective cata-
lysts in the oxidation of cyclohexane to cyclohexanol and cyclohexanone, using low power microwave
(MW) irradiation, under mild conditions. Without a promoter, the activity of the catalyst reached a turn-
over number of 1.44 Â 103 and a turnover frequency of 1.98 Â 103 hÀ1, after 2 h, at 50 °C.
Ó 2017 Elsevier B.V. All rights reserved.
Keywords:
COPPER(II) complexes
Arylhydrazones of active methylene
compounds (AHAMC)
Catalytic activity
Microwave irradiation
Cyclohexane oxidation
1. Introduction
to AHAMC can increase the solubility of the obtained complexes
and provide an acidic medium in the peroxidative oxidation of
Arylhydrazones of active methylene compounds (AHAMC) bear
hydrazone, carbonyl and cyano moieties and thus provide a rich
organic and coordination chemistry [1,2]. Usually the AHAMC
ligands are prepared by the Japp-Klingemann reaction [3]. Nucle-
ophilic additions to cyano group(s) of the obtained hydrazone
compounds lead to new AHAMC ligands [4]. AHAMC and their
complexes have been found to possess a wide variety of useful
properties, such as sensor or analytical reagents, spin-coating
films, optical storage media, catalysts, etc [1,5]. The modification
of the active methylene fragment or aromatic moiety can be used
as a synthetic approach for the regulation of properties of those
ligands and their coordination compounds. For instance, introduc-
tion of hydrophilic polar groups, such as sulfo or carboxy group(s),
alkanes [6].
Acidic medium can also be created/organized by using an axil-
lary ligand which has an acidic proton, for example, imidazole (im).
Their application in the functionalization of inert CAH bonds of
hydrocarbons with a metal catalyst and an oxidant is a promising
area of catalysis [2f,4a,4b,6]. Alkanes are attractive substrates for
added value organic chemicals (alcohols, ketones, aldehydes and
carboxylic acids). Unfortunately, their low reactivity constitutes a
considerable limitation towards their broad application for direct
syntheses of oxygenated products under relatively mild
conditions [7]. However, the use of an appropriate metal catalyst,
namely a copper complex [8], that promotes the catalytic function-
alization of the non-activated CAH bonds of hydrocarbons has
been one of the goals of some of us [7,9]. We chose cyclohexane
oxidation as the model reaction to test our complexes, which con-
stitutes an important step for Nylon 6 and Nylon 6,6 production, a
main industrial process [10].
⇑
Corresponding authors at: Centro de Química Estrutural, Instituto Superior
Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal (E.C.B.
A. Alegria).
Thus, in this work we combine the above mentioned
approaches towards the following aims: i) to synthesize a new
E-mail addresses: apribeiro@tecnico.ulisboa.pt (A.P.C. Ribeiro), ebastos@deq.isel.
ipl.pt (E.C.B.A. Alegria), houcine_naili@yahoo.com (H. Naïli).
https://doi.org/10.1016/j.ica.2017.12.001
0020-1693/Ó 2017 Elsevier B.V. All rights reserved.

R. Jlassi et al. / Inorganica Chimica Acta 471 (2018) 658–663
659
copper(II) complex, [CuL(im)(H2O)] (1), derived from sodium (E/Z)-
2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl) benzene-
sulfonate (NaHL) and imidazole (im) ligands and ii) to apply 1
and known Cu(II) complexes, [Cu(H2O)2L]ÁH2O (2), [Cu(H2O)(Py)
L]ÁH2O (3), [Cu3(m3-OH)(NO3)(CH3OH)(m2-X)3(m2-HL)] (4) [4], as cat-
alysts for the peroxidative oxidation of cyclohexane.
2. Results and discussion
2.1. Synthesis and characterization of 1
The synthesis and characterization of sodium (E/Z)-2-(2-(1-
cyano-2-methoxy-oxoethylidene)hydrazinyl)
benzenesulfonate
(NaHL) (Scheme 1) was reported earlier by us [4a] and will not
be discussed here. Reaction of copper(II) nitrate hydrate with
NaHL in the presence of imidazole (im) in a methanol solution
leads to the mononuclear compound [CuL(im)(H2O)] (1)
(Scheme 1).
spectroscopy, ESI-MS and single crystal X-ray diffraction. The IR
spectrum of 1 displays bands at 3448 (O–H), 2222 (C„N),
1646 (C@O) and 1579
(C@N) cmÀ1 which are significantly
shifted in relation to those of the free ligand [3475 (OH), 2209
(C„N), 1710 (C@O), 1628 (C@N)] [4a].
1 was characterized by elemental analysis, IR
Fig. 1. Asymmetric unit of 1.
m
m
the two ideal coordination geometries. The apical positions are
occupied by the N donor atoms N1 and N4; the bond lengths are
located at 1.976(3) Å and 1.956(3) Å, respectively. The angle of
N4–Cu1–N1 is with 179.12(11)° close to 180°. The equatorial posi-
tions of the trigonal plane are occupied by the O donor atoms O4,
OW1 and O1 (Fig. 2). The bond lengths are Cu1–O1 = 1.991(2),
Cu1–O4 = 1.978(2) and Cu1–OW1 = 2.234(2) Å.
m
m
m
m
m
m(C@OÁ Á ÁH), 1596
m
Elemental analysis and ESI-MS in methanol (peak at m/z 431.7
[Mr+H]+) support the proposed formulation of 1 as a monomer.
2.2. Description of the X-ray crystal structure
The copper ion forms two fused six-membered metallacycles,
Cu1-O1-S1-C1-C2-N1 and Cu1-O4-C9-C7-N2-N1. Consistent with
electron delocalization in these metallacycles are the N1–N2, C7–
N2, and C9@O4 bond lengths of 1.295(3), 1.344(4), and 1.241(4)
Å (see Table S1), respectively. The crystal structure is stabilized
by weak intermolecular hydrogen bonding interactions (Fig. 3;
Table S2) between the coordinated water molecule, the imidazol
entities and the nitrile or sulfonate bridging group. Within the
intermolecular hydrogen bonds; O1W À H2ÁÁÁN3ii, N5–H5AÁ Á ÁO3iii
and O1W–H1Á Á ÁO2i, the donor-acceptor distances are equal to
2.873(1), 3.047(1) and 2.744(1) Å, respectively.
The asymmetric unit of the title compound (Fig. 1) contains one
monomeric unit of the title compound, in which the Cu(II) ion is
coordinated by the L2À ligand together with one water molecule
and one imidazole ligand. The Cu atom adopts a five-coordinated
geometry defined by three oxygen atoms O1, O4 and OW1 belong-
ing to the sulfonate group, ester group and water molecule and two
nitrogen atoms N1 in the hydrazo group and N4 of imidazole
entity.
The geometry around the CuII centre in the monomeric unit can
be described as distorted trigonal bipyramidal. Considering that
the complex presents a coordination number of 5, the parameter
was calculated for the complex to measure the grade of distortion,
and its value varies from 0 (in regular square-based pyramidal
geometry) to 1 (in regular trigonal bipyramidal geometry) [11].
2.3. Catalytic oxidation of cyclohexane
The catalytic study focused on the use of cyclohexane as model
substrate for the investigation of the catalytic performance of 1 and
known Cu(II) complexes, [Cu(H2O)2L]ÁH2O (2), [Cu(H2O)(py)L]ÁH2O
(3) and [Cu3(m3-OH)(NO3)(CH3OH)(m2-X)3(m2-HL)] (4), derived from
the same ligand (Scheme 2) [4a], in oxidation reactions of
cycloalkanes using tert-butyl hydroperoxide (TBHP, 70% aq.
In the title complex the calculated
s value is equal to 0.40. This
value is lower than 0.5 and shows that in the title compound the
geometry around the copper atom is nearly intermediate between
Scheme 1. Synthesis of 1.
Fig. 2. Schematic drawing of coordination geometry of Cu(II) in 1.

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R. Jlassi et al. / Inorganica Chimica Acta 471 (2018) 658–663
(Fig. 4 for complex 1, Table 1). The oxidation reaction proceeds
even if a very small relative amount of catalyst is used leading
to rather high TONs up to 1.44 Â 103 (Table 1, entry 12, for com-
plex 1) and TOFs up to 1.98 Â 103hÀ1 were observed for the low-
est amount of catalyst (Table 1, entry 9, complex 1). The effect of
the catalyst amount on the overall yield and TON is illustrated in
Fig. 4a and b, respectively, for complex 1. An increase of the cat-
alyst amount leads to an enhancement of the product yield but
to a decrease of TON.
The combination of a considerable good yield (up to 12%,
Table 1, entry 1), with TON and TOF values up to 110 and 220,
respectively, (Table 1, entry 1), reached in a short reaction time
(30 mins) and under mild conditions, is indicative of an remarkable
activity of the catalytic system based on complex 1.
Cyclohexanol is the main product under our experimental con-
ditions (after treatment of the final reaction mixture with triph-
enylphosphine) with selectivity values up to ca. 89% (Table 1,
entry 9) for complex 1.
Although complexes 1 and 4 have similar catalytic activities
after 120 min reaction at same conditions (17 and 15%, entries 4
and 25, Table 2, respectively for 1 and 4,), it is noteworthy to men-
tion the existence of 3 metal centers in the latter whereas in the
former this activity is ensured only by one copper metal center.
These transformations (Scheme 3) are expected to occur mainly
via cyclohexyl hydroperoxide (CyOOH), as reported for other cop-
per (II) catalysts [7,8], which, upon addition of PPh3, converts into
the CyOH. Hence, the measured alcohol predominates significantly
over the ketone (cyclohexanone) for all catalyst concentrations
(Fig. 5).
Fig. 3. H-bond interactions in compound 1 which lead to a 3D framework. Ball-and-
stick model of a selected part of the 3D network formed by 1 in the solid state due
to intermolecular hydrogen bonds, indicated by green coloured dashed bonds.
It deserves to be highlighted that the levels of activity and ratio
towards the formation of cyclohexanol are high. No traces of
byproducts were detected by gas chromatography–mass spec-
trometry (GC-MS) analysis of the final reaction mixtures. In com-
parison with the industrial process, our yields and selectivities
are much higher [10f,12]. Our system also achieves higher yields
than those reported Cu(II) complexes with arylhydrazone of
acetylacetone, [Cu(H2O){(CH3)2NCHO}(HL)] and [Cu2(CH3OH)2(m-
HL)2] [6], where a total yield of 14% is reached after 4.5 h of reac-
tion, using hydrogen peroxide as oxidant (H2O2, 50% aq. solution)
and performing the reaction at 50 °C.
Our yields are comparable to those reported Cu(II) complexes
with arylhydrazones of barbituric acid [Cu(H2L1)(H2O)(im)]Á3H2O
and [Cu(H2L2)(im)2]ÅH2O (im = imidazole; H4L1 = 5-(2-(2-hydrox-
yphenyl)hydrazono)pyrimidine-2,4,6(1H,3H,5H)-trione; H4L2 = 2-
(2-(2,4,6-trioxotetra-hydropyrimidin-5(2H)-ylidene) hydrazinyl)
benzenesulfonic acid) (yields up to 21% and TON up to 213) in
the peroxidative (with H2O2) oxidation of cyclohexane after 6 h
reaction at room temperature [13].
Scheme 2. Structures of 2–4.
3. Conclusions
solution) as oxidant and acetonitrile (CH3CN) as solvent at 50 °C
(Scheme 3). The results are shown in Table 1. The systems based
on 1 and 4 exhibit the highest catalytic activity toward the
oxidation of cyclohexane to cyclohexanol and cyclohexanone,
according to Scheme 3 and Table 2.
In this study we have successfully used AHAMC chelating
ligands bearing the –SO3H group in ortho-position of the aro-
matic part and imidazole (im) to synthesize a new mononuclear
copper(II) complex, [CuL(im)(H2O)] (1). Both ligands and the
coordinated water molecule play a crucial structural role in the
organization of the hydrogen bonded assemblies, influencing
the overall 3D supramolecular structure and increasing the water
solubility of the complex. The catalytic activity of 1 was com-
pared with known copper(II) arylhydrazone complexes 2–4
derived from the same ligand (NaHL). The work has shown that
1 acts as a good catalyst for the oxidation of cyclohexane to
cyclohexanol and cyclohexanone, under mild conditions and in
the presence of tert-butyl hydroperoxide (TBHP, 70% aq. solution)
as oxidant, under low power microwave irradiation. The effects
The influence of the amount of catalyst was studied for 1 in
the range of concentrations from 4.0 Â 10À4 to 4.0 Â 10À6
M
Scheme 3. Peroxidative oxidation of cyclohexane catalysed by 1–4.

R. Jlassi et al. / Inorganica Chimica Acta 471 (2018) 658–663
661
Table 1
Oxidation of cyclohexane using 1–4 as catalyst precursors.a
Entry
Catalyst precursor
Catalyst concentration
mol LÀ1
Yields, (%)b
Total TONd
Total TOFe
Conversionf(%)
Selectivityg(%)
Time (min)
CyO
CyOH
Totalc
1
2
3
4
1
4 Â 10À4
30
60
90
120
1.9
2
2.3
2.7
10.3
12.1
13.7
14.4
12.2
14.1
16
110
127
126
154
220
127
84
14.1
15.1
19.0
22.1
73.3
80.4
72.0
65.2
17.1
77
5
6
7
8
1
1
4 Â 10À5
4 Â 10À6
30
60
90
120
1.5
1.6
1.8
2.1
4.1
6.3
7.1
9.3
5.6
7.9
8.9
11.4
504
711
1.01 Â 103
6.0
8.5
9.9
12.1
68.4
74.2
71.9
76.9
711
801
534
513
1.98 Â 103
1.08 Â 103
840
1.03 Â 103
9
30
60
90
120
0.1
0.1
0.1
0.1
1.0
1.1
1.3
1.5
1.1
1.2
1.4
1.6
990
1.1
1.5
1.6
1.7
89.3
75.3
82.8
87.6
10
11
12
13h
1.08 Â 103
1.26 Â 103
1.44 Â 103
720
1
4 Â 10À4
4 Â 10À4
120
1.6
3.8
5.4
49
24
5.9
64.3
14
15
16
17
2
30
60
90
120
0
0
0
0
0.6
0.6
1.0
3.3
0.6
0.6
1
5
5
9
30
10
5
6
0.7
0.7
1.2
4.2
92.3
88.1
83.3
78.6
3.3
15
18
19
20
21
3
4
–
4 Â 10À4
4 Â 10À4
Blank
30
60
90
120
0
0
0
0
5.3
6.3
7.5
8.8
5.3
6.3
7.5
8.8
49
40
69
35
99
40
46
17
5.7
6.7
8.0
93.5
94.0
93.5
87.1
10.1
22
23
24
25
30
60
90
120
0
0
0
0
11.2
11.4
12.0
15.2
11.2
11.4
12
10
208
105
74
12.0
12.2
13.3
19.2
93.5
93.4
90.2
79.2
105
111
141
15.2
70
26
30
–
–
–
–
–
–
–
a
Reaction conditions, unless stated otherwise: [cyclohexane]0 = 0.36 mol LÀ1, [TBHP]0 = 1.8 mol LÀ1, MeCN (up to 5 mL total volume), 50 °C, using 10 W of microwave
irradiation
b
Moles of product/100 mols of C6H12, based on GC analysis, after treatment with PPh3.
Moles of products [cyclohexanol (CyOH) + cyclohexanone (CyO)]/100 mol of cyclohexane, determined by GC after treatment with PPh3.
Total turnover number = moles of products per mol of catalyst.
Turnover frequency (moles of products per mol of catalyst per hour).
Conversion = moles of converted (reacted) substrate per mole of substrate.
Selectivity = moles of cyclohexanol per mole of converted substrate.
c
d
e
f
g
h
For comparative purposes, Cu(NO3)2 was used as the catalyst.
Table 2
Crystallographic data for 1.
4. Experimental
Empirical formula
C13H13CuN5O6S
4.1. Equipment and materials
Formula weight (g/mol)
430.88
All chemicals were obtained from commercial sources and
used as received. NaHL was prepared according to a published
Temperature (K)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
100 K
Monoclinic
P21/c
16.1553(6)
7.1108(3)
14.2457(5)
103.153(4)
1593.57(11)
4
procedure [4a]. The infrared spectrum (4000–400 cmÀ1
) was
recorded on a Nicolet FTIR Nexus spectrophotometer on KBr
pellets. Chromatographic analyses were undertaken by using a
FISONS Instruments GC 8000 series gas chromatograph (Fisons
Instruments), equipped with an Flame Ionization Detector FID
detector, a DB-WAX capillary column (length: 30 m; internal
diameter: 0.32 mm) (Agilent Technologies, Santa Clara, CA,
USA), and He as the carrier gas, and run by the Jasco-Borwin
v.1.50 software (Jasco, Tokyo, Japan). The temperature of
injection was 240 °C. The column was initially maintained at
100 °C for 1 min, and heated up to 180 °C with the heating
rate of 10 °C/min, and held at this temperature for 1 min. The
attribution of the peaks observed in GC was carried out on the
basis of calibration curves obtained with known concentrations
of pure samples. The catalytic tests were performed under MW
irradiation in a focused microwave Anton Paar Monowave 300
reactor (10 W), using a 10 mL capacity reaction tube with a 13
mm internal diameter, fitted with a rotational system and an
IR temperature detector.
b (°)
V (Å3)
Z
Calculated density
1.796
k (MoK
Measured reflections Independent reflections
Reflections [I > 2 (I)]
a
) (Å)
0.71073
6185 2777
2415
2.928–24.993
876
244
0.0385
0.0905
1.079
r
h range for data collection (°)
F (0 0 0)
Number of parameters
R1 [I > 2
wR2 [I > 2
r
(I)]
(I)]
r
GOOF
of various parameters have been investigated and allowed us to
achieve total yields and TONs up to 17% and 1.44 Â 103,
respectively.

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R. Jlassi et al. / Inorganica Chimica Acta 471 (2018) 658–663
(a)
(b)
Fig. 4. Effect of the amount of catalyst and of the reaction time on a) the total yield (cyclohexanol + cyclohexanone) and b) the total turnover number (TON) (cyclohexanol +
cyclohexanone) in the oxidation of cyclohexane by TBHP, catalysed by complex 1 in different concentrations. Reaction conditions: [cyclohexane]0 = 0.36 mol L–1, CH3CN up to
5 mL total volume, 50 °C, 10 W,
[1]0 = 4 Â 10À4 mol L–1
;
[1]0 = 4 Â 10À5 mol L–1
;
[1]0 = 4 Â 10À6 mol L–1
.
angles calculated from the final atomic coordinates, as well as
hydrogen bonds, are listed in Tables S1 and S2, respectively. The
drawings were made with Diamond program [15]. CCDC
1448651 contains the supplementary crystallographic data for this
paper.
4.4. Catalytic studies
The catalytic tests under MW irradiation (MW) were performed
in a focused microwave CEM using a 10 mL capacity glass reactor
tube with a 13 mm internal diameter, fitted with a rotational sys-
tem and an IR temperature detector. The cyclohexane oxidations
were carried out using MeCN as solvent (up to 5.0 mL of total vol-
ume), and the catalyst precursors 1–4 were introduced into the
reaction mixture in the form of a stock solution of acetonitrile (1
 10À3 mol LÀ1). The cyclohexane (1.82 mmol) was then intro-
duced, and the reaction started when 8.8 mmol of tert-butyl
hydroperoxide (TBHP, 70% aq. solution) were added in a single por-
tion. The final concentrations of the reactants in the reaction mix-
ture were as follows: catalyst precursor 1 (4 Â 10À6 to 4 Â 10À4
mol LÀ1), substrate (0.36 mol LÀ1) and TBHP (1.8 mol LÀ1). The
reaction mixture was stirred for 0.25 to 2 h at 50 °C under MW
Fig. 5. Effect of the reaction time on the yields of oxygenated products (cyclohex-
anol and cyclohexanone) in the oxidation of cyclohexane by TBHP, catalysed by
complex 1.
Total (Cyclohexanol + Cyclohexanone);
Cyclohexanol;
Cyclohexanone. Reaction conditions: [cyclohexane]0 = 0.36 mol L–1, CH3CN up to 5
mL total volume, 50 °C, 10 W, [1]0 = 4 Â 10À4 mol L–1
.
4.2. Synthesis and characterization of 1
0.305 g (1.0 mmol) of NaHL were dissolved in 15 mL methanol,
whereafter 0.233 g (1.0 mmol) of Cu(NO3)2Á2.5H2O and 0.068 g
(1.0 mmol) imidazole were added. The mixture was stirred for
30 min at 80 °C and left for slow evaporation; green crystals of
the product started to appear after ca. 3 days at room temperature.
Finally, the crystals were filtered off and dried in air.
irradiation (10 W), then 90 lL of cycloheptanone (as internal stan-
dard) and 10 mL of diethyl ether (to extract the substrate and the
products from the reaction mixture) were added. The resulting
mixture was stirred for 15 min and then PPh3 was added to the
final organic phase (to reduce the cyclohexyl hydroperoxide, if
formed) and the mixture was analyzed according to Shul’pin’s
method [16,17]. Blank experiments were performed and confirmed
that no cyclohexane oxidation products were obtained in a consid-
erable yield in the absence of the metal catalyst precursor.
1: Yield, 78% (based on Cu). The pale green crystalline com-
pound is soluble in ethanol, methanol, acetonitrile and water. Anal.
Calcd for C13H13CuN5O6S (Mr = 430.88): C, 36.24; H, 3.04; N, 16.25.
Found: C, 36.13; H, 2.95; N, 16.18. ESI-MS: m/z: 431.7 [Mr+H]+. IR
(KBr, selected bands, cmÀ1): 3448
(C@O), 1579 (C@N).
m(O–H), 2222 m(C@N), 1646 m
Acknowledgements
m
This work has been partially supported by the Foundation for
Science and Technology (FCT), Portugal (UID/QUI/00100/2013 and
also for the PTDC/QEQ-QIN/3967/2014). G.A.O.T. and A.P.C.R. are
thankful to the CATSUS doctoral and post-doctoral programs of
FCT for their PhD (SFRH/ PD/BD/106015/2014) and post-doc
(SFRH/BPD/90883/2012) grants, respectively. The authors acknowl-
edge the IST Node of the Portuguese Network of Mass-spectrometry
for the ESI-MS measurements. This work also was supported by the
’’RUDN University Program 5-100’’, Russian Federation.
4.3. Crystallographic structure determination
A suitable crystal of the title compound was immersed in cryo-
oil, mounted in a Nylon loop, and measured at 110 K. All data were
collected on an Oxford Gemini S diffractometer. For data collection,
cell refinement and data reduction the software CrysAlisPro was
used [14a]. All structures were solved by direct methods using
SHELXS-2013 and refined by full-matrix least-squares procedures
on F2 using SHELXL-2013 [14b]. All non-hydrogen atoms were
refined anisotropically. All C- and N-bonded hydrogen atoms
were refined using a riding model. The positions of N-bonded
hydrogen atoms were taken from difference Fourier maps and
refined isotropically. Crystallographic data and structural
refinements are summarized in Table 2. Bond distances and
Appendix A. Supplementary data
X-ray analysis. Selected bond distances (Å) and angles (°) for 1.
Hydrogen-bonding geometry (Å) for 1. Supplementary data associ-

R. Jlassi et al. / Inorganica Chimica Acta 471 (2018) 658–663
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