A new oxidovanadium(IV) complex containing an O, N-bidentate Schiff base ligand: Synthesis, characterization, crystal structure determination, thermal study and catalytic activity for an oxidative bromination reaction

Article abstract of DOI:10.1016/j.poly.2013.10.026

A new oxidovanadium(IV) schiff base complex (1) containing an ethyl bromide pendant group was synthesized by the reaction of the related bidentate O, N-Schiff base ligand and VO(acac)₂ in a 2:1 ratio in methanol, under reflux conditions. The Schiff base ligand and its vanadyl Schiff base complex were characterized by ¹H NMR and FT-IR spectra, and CHN analysis. The crystal structure of 1 was also determined by single crystal X-ray analysis. The vanadium center in this structure has a distorted tetragonal pyramidal N₂O₃ coordination sphere. The Schiff base ligand HL acts as a bidentate ligand by coordinating via the nitrogen atom of the imine group and the oxygen atom of the phenolic group, thereby forming a six-membered chelating ring. There are some non-classical inter- and intra-molecular hydrogen bonds of the type C-Ha?O and C-Ha?Br in 1. The catalytic activity of 1 was studied for the oxidative bromination of 2-nitrophenol as a model substrate. Different reaction parameters were studied in this reaction and the oxidative bromination of some organic compounds by a catalytic amount of 1 showed that it was an effective and selective catalyst under optimal conditions. Thermogravimeric analysis of 1 showed that it decomposed in two stages. In addition, complex 1 thermally decomposed in air at 660 C and the XRD pattern of the obtained solid showed the formation of V₂O₅ nanoparticles with an average size of 57 nm.

Full text of DOI:10.1016/j.poly.2013.10.026

Polyhedron 68 (2014) 144–150
Contents lists available at ScienceDirect
Polyhedron
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A new oxidovanadium(IV) complex containing an O, N-bidentate Schiff
base ligand: Synthesis, characterization, crystal structure determination,
thermal study and catalytic activity for an oxidative bromination
reaction
a
b
Gholamhossein Grivani a, , Vida Tahmasebi , Aliakbar Dehno Khalaji
⇑
a School of Chemistry, Damghan University, Damghan 36715-364, Iran
b Department of Chemistry, Faculty of Science, Golestan University, Gorgan, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
A new oxidovanadium(IV) schiff base complex (1) containing an ethyl bromide pendant group was
synthesized by the reaction of the related bidentate O, N-Schiff base ligand and VO(acac)2 in a 2:1 ratio
in methanol, under reflux conditions. The Schiff base ligand and its vanadyl Schiff base complex were
characterized by 1H NMR and FT-IR spectra, and CHN analysis. The crystal structure of 1 was also deter-
mined by single crystal X-ray analysis. The vanadium center in this structure has a distorted tetragonal
pyramidal N2O3 coordination sphere. The Schiff base ligand HL acts as a bidentate ligand by coordinating
via the nitrogen atom of the imine group and the oxygen atom of the phenolic group, thereby forming a
six-membered chelating ring. There are some non-classical inter- and intra-molecular hydrogen bonds of
the type C–HÁ Á ÁO and C–HÁ Á ÁBr in 1. The catalytic activity of 1 was studied for the oxidative bromination
of 2-nitrophenol as a model substrate. Different reaction parameters were studied in this reaction and the
oxidative bromination of some organic compounds by a catalytic amount of 1 showed that it was an
effective and selective catalyst under optimal conditions. Thermogravimeric analysis of 1 showed that
it decomposed in two stages. In addition, complex 1 thermally decomposed in air at 660 °C and the
XRD pattern of the obtained solid showed the formation of V2O5 nanoparticles with an average size of
57 nm.
Received 11 July 2013
Accepted 12 October 2013
Available online 31 October 2013
Keywords:
Oxidovanadium(IV)
Schiff base
Crystal structure
Oxidative bromination
V2O5 nanoparticle
TG
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
molecules for material science, industrial chemicals and bioactive
compounds [32–34]. Different methods have been used in
In recent decades the coordination chemistry of transition
metal Schiff base complexes has increasingly developed in differ-
ent aspects [1–8] because they have high stability, along with
interesting and important properties in different oxidation states.
There has been considerable interest in the coordination chemistry
of vanadium complexes because of their structural features [9–11],
catalytic applications [12–14] and biological roles in a variety of
biochemical processes, such as haloperoxidation [15–17], nitrogen
fixation [18], phosphorylation [19], glycogen metabolism [20–22]
and insulin mimicking [23–26], as well as some biological out-
comes like antimicrobial [27,28] spermicidal [29], anti-leukemia
[30] and antitumor [31] activities.
halogenations, but oxidative halogenation has the potential to be
used in reactions where only one halogen atom is incorporated
into the molecule and the residual HX is regenerated by oxidation
[35]. Haloperoxidases are enzymes that catalyze different
oxidation reactions, like the oxidation of halides to corresponding
hypohalous acids and the oxidation of organic sulfides to
sulfoxides [36–38]. Enzymatic halogenation is still a potentially
effective and environmentally friendly route, but it has not been
commercialized on a large scale because of the low operational
stability of the haloperoxidase enzymes. The active site species in
haloperoxidase enzymes contains a vanadate moiety in a trigonal
bipyramidal or square pyramidal geometry which is covalently
linked to a histidine residue [39]. Thus the design of oxidovanadi-
um(V) and (IV) complexes with a mixed O- and N-donor atoms
coordination sphere can be considered as structural models of
vanadate-dependent haloperoxidases. Here we investigate the
synthesis, characterization, crystal structure determination and
catalytic activity of a new oxidovanadium(IV) Schiff base complex
Halogenated compounds are very essential in organic chemistry
as starting compounds, synthetic intermediates and designer
⇑
Corresponding author. Tel.: +98 232525431; fax: +98 2325235431.
E-mail address: grivani@du.ac.ir (G. Grivani).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.10.026

G. Grivani et al. / Polyhedron 68 (2014) 144–150
145
CH2CH2Br
OH
H
Br
N
Br
Methanol
Ref
O
Br
4h
HBr.H2N
OH
HL
Methanol
Ref/ 2 h
CH2CH2Br
O
O
V
Br
N
O
N
BrH2CH2C
1
Br
Scheme 1. Preparation procedures of (HL) and its vanadyl(IV) complex (1).
(1) derived from 5-bromo-salicylaldehyde and 2-bromoethylamine
(Scheme 1).
(s, 1H, –O–H), 8.29 (s, 1H, HAC@NA)), 7.4 (d, 1H, phenyl–H), 7.3
(d, 1H, phenyl–H), 6.8 (s, 1H, phenyl–H), 4.01 (t, 2H, –CH2Br),
3.65 (t, 2H, –N–CH2–).
2. Experimental
2.2. Synthesis of complex 1
All chemicals and reagents were obtained from Merck Chemical
Company. All solvents were used without further purification. The
infrared spectra were recorded on a Perkin-Elmer RXI spectropho-
tometer with KBr disks (4000–400 cmÀ1). C, H and N determina-
tions were performed on a Heraeus CHN–O-Rapid analyzer. The
1H NMR spectrum of the ligand was measured on a BRUKER
DRX-500 AVANCE spectrometer at 500 MHz. All GC yields based
on the starting materials were obtained using a Teif Gostar Fraz
Co instrument with a silicon-DC 200 column. The TG analysis
was performed on a Perkin Elmer TG/DTA lab system 1 (Technol-
ogy by SII) in air atmosphere with a heating rate of 20 °C/min in
the temperature range 30–600 °C.
In a 100 ml round bottom flask, 5 mmol of HL was dissolved in
40 ml of MeOH and to this solution was added 2.5 mmol of
VO(acac)2 dissolved in 20 ml of MeOH. The contents of the flask
were then refluxed with stirring for 2 h. After evaporating the sol-
vent, the remaining reaction mixture was crystallized in a solvent
mixture of MeOH/CHCl3 (1/1, v/v). The greenish crystals that
formed were filtered off, washed with n-hexane and dried in an
oven. M.p.: 227 °C. Anal. Calc. for C18H16Br4N2O3V: C, 32.05; H,
2.26; N, 4.15. Found: C, 31.83; H, 2.35; N, 4.13%. IR (KBr pellet,
cmÀ1): 2834–2950, and 2994–3070, (w, C–H aliphatic and aro-
matic), 1618 (s, C@N), 1446, 1460, 1538, 1558 (m, C@C), 1268
(m, C–O), 686 (m, C–Br), 984 (V@O).
2.1. Synthesis of 2-{(E)-[2-(bromoethyl)imino]methyl}-4-
2.3. X-ray structure determination
bromophenol (HL)
A green single crystal of 1 with approximate dimensions of
0.20 Â 0.20 Â 0.10 mm was used in the X-ray diffraction experi-
ment. Compound 1 crystallizes in the monoclinic space group Pbca.
The X-ray diffraction measurements were made on a STOE IPDS-II
To a 250 ml round bottom flask containing 150 ml absolute
methanol were added 10 mmol of 4-bromo-2-hydroxy benzalde-
hyde, 10 mmol of 2-bromoethyl ammonium hydrobromide and
10 mmol of NaOH, and the contents were refluxed with stirring
for 4 h. After evaporating the solvent, the yellow precipitate that
formed was collected and washed with slightly cooled water and
then with a 1:1 mixture of n-hexane and dichloromethane. Yield:
2.27 g (83%). Yellow crystals were obtained by the crystallization
of the precipitate in a 1:1 mixture of chloroform and methanol.
M.p.: 78 °C. Anal. Calc. for C9H9Br2NO: C, 35.35; H, 2.75; N, 4.55.
Found: C, 35.18; H, 2.93; N, 4.56%. IR (KBr pellet, cmÀ1):
3350–3450 (br, O–H, phenolic), 2840–3000 (w, C–H aliphatic
and aromatic), 1636 (s, C@N), 1436, 1481, 1581, 1602 (m, C@C),
1269 (m, C–O), 682(m, C–Br). 1H NMR (CDCl3, d (ppm)): 13.00
diffractometer with graphite monochromated Mo K
a radiation.
Cell constants and orientation matrices for data collection were ob-
tained by least-squares refinement of the diffraction data from
7076 unique reflections. Data were collected to a maximum 2h va-
lue of 58.34° in a series of
x scans in 1° oscillations and integrated
using the Stoe X-AREA [40] software package. A numerical absorption
correction was applied using X-RED [41] and X-SHAPE [42] software.
The data were corrected for Lorentz and Polarizing effects. The
structure was solved by direct methods [43] and subsequent differ-
ence Fourier maps and then refined on F2 by a full-matrix least-
squares procedure using anisotropic displacement parameters

146
G. Grivani et al. / Polyhedron 68 (2014) 144–150
Table 1
Table 2
Crystal data and structure refinement parameters of the title compound.
Selected bond distances (Å) and angles (°) of 1.
Empirical formula
Formula weight
Crystal system
Space group
T (K)
C18H16Br4N2O3V
Br1–C4
Br3–C13
V1–N1
V1–N2
N2–C16
N2–C17
O1–C1
1.878(10)
1.899(9)
2.107(7)
2.120(7)
1.284(11)
1.468(10)
1.320(10)
V1–O3
V1–O2
V1–O1
N1–C7
N1–C8
O2–C10
1.586(6)
1.895(6)
1.929(6)
1.270(10)
1.480(9)
1.326(10)
678.87
orthorhombic
Pbca
298
a (Å)
b (Å)
8.0465(16)
22.100(4)
24.317(5)
4324.2(15)
8
7.87
12360
3813
1985
0.117, 0.97
0.066
0.108
253
c (Å)
O3–V1–O2
O3–V1–O1
O2–V1–O1
O3–V1–N1
O2–V1–N1
O1–V1–N1
O3–V1–N2
O2–V1–N2
O1–V1–N2
N1–V1–N2
C1–O1–V1
C16–N2–C17
C16–N2–V1
C17–N2–V1
N2–C17–C18
111.8(3)
O1–C1–C2
O1–C1–C6
120.2(8)
V (Å3)
113.0(3)
135.3(3)
100.1(3)
86.0(3)
86.9(3)
100.0(3)
87.1(3)
121.8(8)
119.3(8)
122.8(8)
126.3(8)
134.4(6)
121.0(7)
118.8(7)
126.4(8)
110.1(8)
120.4(7)
120.3(7)
114.7(7)
125.8(6)
119.4(6)
Z
l
O2–C10–C11
O2–C10–C15
N2–C16–C15
C10–O2–V1
C14–C13–Br3
C12–C13–Br3
N1–C7–C6
(mmÀ1
)
Measured reflections
Independent reflections
Reflection with I > 2
r(I)
Rint, S
R [F2 > 2
r
(F2)]
84.8(3)
wR (F2)
159.9(3)
131.9(5)
115.3(8)
125.6(6)
119.0(6)
113.6(6)
N1–C8–C9
Parameters
maximum, Dqminimum (e ÅÀ3
C5–C4–Br1
C3–C4–Br1
C7–N1–C8
C7–N1–V1
C8–N1–V1
D
q
)
0.50, À0.49
[44]. The atomic factors were taken from the International Tables
for X-ray Crystallography [45]. All refinements were performed
using the X-STEP32 crystallographic software package [46]. The
molecular structure plots were prepared by ORTEP III [47]. Crystallo-
graphic data and details of the data collection, structure solution
and refinements are listed in Table 1. Selected bond distances,
angles and dihedral angles of 1 are listed in Table 2.
3. Results and discussion
3.1. Synthesis and characterization
Scheme 1 shows the preparation procedures for the bidentate
Schiff base ligand, HL, and its vanadyl Schiff base complex. The
Schiff base ligand of HL was synthesized by the simple reaction
of 5-bromo salicyaldehyde with an equimolar amount of 2-bromo-
ethyl ammonium hydrobromide in the presence of NaOH in meth-
anol as a solvent under reflux conditions. In the subsequent
reaction of the prepared Schiff base ligand (HL) and VO(acac)2 in
a molar ratio of 2:1 in methanol under reflux conditions, the van-
adyl Schiff base complex of 1 was prepared. The Schiff base ligand
(HL) and its vanadyl Schiff base complex (1) were characterized by
elemental (CHN) analysis, 1H NMR and FT-IR spectra. The elemen-
tal analysis confirmed the net chemical compositions of HL and 1.
2.4. General procedure for the oxidative bromination reaction
In a 10 ml round bottom flask equipped with a magnetic
stirring bar, 1 mmol of 2-nitro phenol was reacted with different
amounts of the oxidant, acid, bromine source and the vanadyl
Schiff base complex in 4 ml of solvent. The progress of the
reaction was monitored by GLC and all the yields are GC yields.
In addition, all the reactions were checked by TLC as a qualitative
method.
Fig. 1. The 1H NMR spectrum of HL.

G. Grivani et al. / Polyhedron 68 (2014) 144–150
147
The 1H NMR and FT-IR spectra of the ligand were also confirmed its
functional groups. Fig. 1 shows the 1H NMR spectrum of HL. In
agreement with the structure of the HL, two singlet peaks with
an integration of 1: 1 are seen at 13 and 8.29 ppm, due to the phe-
nolic and iminic protons, respectively. The peaks seen in the region
of 6.5–7.5 ppm are attributed to the phenyl protons, with an inte-
gration of 2:1. Two triplet peaks at 4.01 and 3.65 ppm correspond
to the two methylene protons of the pendant group. In the FT-IR
spectrum of the ligand, a sharp band appeared at 1636 cmÀ1, which
is attributed to the C@N vibrations of the imine group. In the FT-IR
spectrum of the vanadyl Schiff base complex this band was shifted
to a lower wavenumber and appeared at 1618 cmÀ1 due to the
coordination of the imine nitrogen to the vanadyl center. Mono-
meric five coordinated vanadyl complexes show a band around
970 cmÀ1 whereas in polymeric six coordinated vanadyl com-
plexes with linear (polymeric) Á Á ÁV@OÁ Á ÁV@OÁ Á Á units this band
shifts to lower wave numbers and appears around 860 cmÀ1 [48–
50]. Thus the sharp band at 984 cmÀ1 in the FT-IR spectrum of
the Schiff base complex of 1 is attributed to V@O vibrations, indi-
cating the monomeric form of the L2V@O Schiff base complex in
the solid state, as confirmed by the single crystal X-ray diffraction.
Fig. 3. The solvent effect in the oxidative bromination of 2-nitrophenol by 1 in the
presence of H2O2 as the oxidant and KBr as the bromide source. Reaction conditions
at room temperature: Substrate (1 mmol), catalyst (0.0073 mmol), H2O2 (2 mmol),
H2SO4 (2 mmol), KBr (4 mmol), solvent (4 mml).
classical C9–H9aÁ Á ÁO3 (133.459°) and C18–H18aÁ Á ÁO3 (127.981°)
hydrogen bonds in 1. In the molecular packing of 1, two molecules
are connected by intermolecular non-classical C–HÁ Á ÁO and C–
HÁ Á ÁBr hydrogen bonds (Fig. 2).
3.2. X-ray structure of 1
An ORTEP view of 1 with the atom-numbering scheme is shown
in Fig. 2. In this complex, the oxidovanadium(IV) unit is coordi-
nated to two bidentate Schiff base ligands with the two nitrogen
and two phenolate oxygen atoms in equatorial positions and one
oxygen in the axial position to complete the distorted tetragonal
pyramidal N2O3 coordination sphere. The bond angles within the
coordination sphere range from 84.8(3)° for (O1–V1–N2) to
135.3(3)° for (O2–V1–O1), which indicates a significant distortion
of the tetragonal pyramid. The V–O [1.895(6) and 1.929(6) Å] and
V–N [2.107(7) and 2.120(7) Å] bond distances in 1 agree well with
the same distances and angles in other oxidovanadium(IV) Schiff
base complexes [13,51–54]. The vandyl (V@O) bond length,
1.586(6) Å, is similar to this bond in other oxidovanadium(IV)
Schiff base complexes [51–55] and gives a strong absorption in
the FT-IR spectrum at 984 cmÀ1. The two Schiff base ligands coor-
dinate to the vanadium center in a trans geometry with respect to
each other. As shown in Fig. 2, there are two intramolecular non-
3.3. Catalytic activity
The catalytic activity of the vanadyl Schiff base complex, 1, was
studied in the oxidative bromination of the phenolic compounds.
2-Nitrophenol was used as a model substrate and different param-
eters, such as solvent, acid, oxidant and bromide salt, were opti-
mized. The oxidative bromination of 2-nitrophenol with
a
catalytic amount of 1 in different solvents was investigated and
the results are illustrated in Fig. 3. The maximum yield (100%)
was obtained in a mixture of H2O/MeOH in a 1:3 ratio due to the
better compatibility of the organic substrate, vanadyl complex
(catalyst) and inorganic reagents, such as acid, oxidant and bro-
mide salt, in this solvent mixture than in the others investigated.
The typical reaction medium for bromoperoxidases is ocean water
[38]. Water, however, is a nucleophile and therefore able to inter-
cept electrophiles, changing the selectivity. In order to achieve a
Table 3
The effect of oxidant, acid and bromide salt in the oxidative bromination of 2-
nitrophenol by the complex of 1a,b,c at room temperature.
Run
1
Saltd
KBr
Acid
Oxidant
H2O2
Time (min)
20
% Yields
100
H2SO4
2 mmol
HNO3
4 mmol
H3PO4
2 mmol
H2SO4
2 mmol
H2SO4
2 mmol
H2SO4
2 mmol
H2SO4
2 mmol
H2SO4
2
3
KBr
H2O2
H2O2
H2O2
TBHP
KHSO4
H2O2
H2O2
120
120
100
100
120
90
25.5
KBr
28
4e
5
KBr
No reaction
No reaction
No reaction
100
KBr
6
KBr
7
NaBr
NH4Br
8
100
40
2 mmol
a
b
c
2-Nitrophenol as substrate (1 mmol).
Solvent (4 ml with a 1:3 ratio of H2O/MeOH).
Catalyst (0.0073 mmol).
4 mmol.
Blank experiment.
d
e
Fig. 2. An ORTEP view of
1 with the atom-numbering scheme with some
intramolecular and intermolecular hydrogen bonding.

148
G. Grivani et al. / Polyhedron 68 (2014) 144–150
oxidants H2O2, tert-butylhydroperoxide (TBHP) and KHSO5, H2O2
was the best oxidant in this reaction (Table 3). The salt effect
was also studied for the oxidative bromination reaction of 2-nitro-
phenol. The catalyst was employed using H2O2 as an oxidant and
MBr (M = Na, K, NH4) as a bromine source (Table 3). Among the
three salts, KBr was found to be the most efficient bromine source
and gives a monoselective product. Sodium bromide and ammo-
nium bromide showed less efficiency and they did not produce
regioselective products. In the presence of homogeneous and en-
zyme catalysts, the liberation of Br2 from KBr by H2O2 is well
known [38,56,57]. Thus it was expected that the same situation
may also prevail in the present case and could be well explained
by the proposed mechanism where the generation of Br2 is much
easier in this case. In the absence of catalyst, the reaction mixture
did not produced any brominated product, demonstrating the cat-
alytic role of the oxidovanadium(IV) complex of 1. The effect of the
oxidant and salt amount is given in Fig. 4 and 5, respectively and 2
and 4 mmol were chosen as the optimal amounts, respectively. All
of the above experiments were investigated at room temperature.
The influence of temperature was also studied. The reaction was
monitored at a temperature 80 °C, but there was no appreciable ef-
fect on the conversion and selectivity of 2-nitrophenol, similar to
Ref. [56]. With an increase in temperature the conversion and
selectivity of 2-nitrophenol was almost the same. Then the oxida-
tive brominations of some organic phenyl substituted compounds
were studied (Table 4). A comparison of the TOFs (mol of substrate/
mol of catalyst  time (h)) of recent vanadyl complexes [57–60] or
other metal mediated catalysts [57,61] with the TOF of the titled
vanadyl complex (1) shows the high activity of 1 in the oxidative
bromination reaction. As seen, almost all of the given organic com-
pounds in Table 4 are brominated effectively and selectively to give
only the mono brominated compounds. 2-Nitrophenol, 2-chloro-
phenol, 2-chloro benzaldehyde, salicylaldehyde, 2-hydroxy-3-
methoxy benzaldehyde and 2-hydroxy acetophenone were
selectively and efficiently converted into their monobromo prod-
ucts in the para-position (with respect to the –OH group), whereas
phenol and benzaldehyde were converted to their monobromo
products in the para- and meta-positions.
Fig. 4. The effect of the oxidant amount in the oxidative bromination of 2-
nitrophenol by 1 in the presence of H2SO4 as an acid source and KBr as a bromide
source. Reaction conditions at room temperature: substrate (1 mmol), catalyst
(0.0073 mmol), H2O2 (1 mmol, 2 mmol, 3 mmol), H2SO4 (2 mmol), KBr (4 mmol),
solvent (4 mml).
Fig. 5. The effect of the salt amount in the oxidative bromination of 2-nitrophenol
by 1 in the presence of H2SO4 as an acid source and H2O2 as an oxidant. Reaction
conditions at room temperature: Substrate (1 mmol), catalyst (0.0073 mmol), H2O2
(2 mmol), H2SO4 (2 mmol), KBr (2 mmol, 3 mmol, 4 mmol), solvent (4 mml).
3.4. Thermal study
Thermal gravimetric analysis (TGA) was carried out to examine
the thermal stability of 1 and the nature of the produced vanadium
oxide. The TG profile of 1 in air with a heating rate of 10 °C minÀ1 is
shown in Fig. 6. The absence of any weight loss up to 100 °C indi-
cates that there are no water molecules in the crystalline solid. The
TGA curve of 1 shows two stages of thermal decomposition. The
first stage occurs within the temperature range 220–470 °C, with
a weight loss of 18.67% due to the loss of one NCH2CH2Br unit from
the Schiff base ligand (calcd. 17.83). The second stage, in the
good reactivity of the metal center for H2O2, with the formation of
the peroxovanadium(IV) complex, and the interaction with hypo-
acid HOBr or BrÀ3 , the lipophilicity of the solvent should be im-
proved [38]. Three inorganic acids were used in the oxidative
bromination of 2-nitrophenol and the results showed that a high
yield was obtained in the case of H2SO4 (Table 3). For the homoge-
neous vanadium bromoperoxidase mimics, appreciable catalytic
activity is invariably observed in strong acid [56]. Among the
Table 4
Oxidative bromination of the organic substrates by catalytic amounts of 1 under optimal conditionsa at room temperature.
Substrate
Time (min)
Product
Selectivity (%)
% Yields
TOFb
2-Nitrophenol
2-Chlorophenol
Phenol
20
80
80
4-Bromo-2-nitrophenol
4-Bromo-2-chlorophenol
4-Bromophenol,
100
100
76
100
89.5
56.5
411.5
102.9
102.9
2-Bromophenol
24
Salicylaldehyde
Benzaldehyde
130
140
5-Bromo-2-hydroxy benzaldehyde
4-Bromo benzaldehyde
100
69
100
100
63.6
58.8
2-Bromo benzaldehyde
31
2-Chloro benzaldehyde
2-Hydroxy-3-methoxy-benzaldehyde
2-Hydroxy acetophenone
120
10
20
4-Bromo-2-chloro benzaldehyde
4-Bromo-2-hydroxy-3-methoxy benzaldehyde
4-Bromo-2-hydroxy acetophenone
100
100
100
43.5
100
100
68.5
826.4
411.5
a
Reaction conditions: substrate (1 mmol), catalyst (0.0073 mmol), oxidant (H2O2: 2 mmol), H2SO4 (2 mmol), KBr (4 mmol), solvent (1:3 ratio of H2O/MeOH, 4 mml).
TOF = mol of substrate/mol of catalyst  time (h).
b

G. Grivani et al. / Polyhedron 68 (2014) 144–150
149
120
100
80
60
40
20
0
Appendix A. Supplementary data
Crystallographic data (excluding structure factors) for the struc-
ture reported in this paper have been deposited with the Cam-
bridge Crystallographic Center, CCDC No. 936687. Copies of the
data can be obtained free of charge on application to The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, fax: +44 1223 336
033, e-mail: deposit@ccdc.cam.ac.uk or http:www.ccdc.cam.ac.uk.
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