N′-(3-Bromo-2-hydroxybenzylidene)isonicotinohydrazide and its oxovanadium(V) complex: Synthesis, structures, and catalytic properties

Article abstract of DOI:10.1080/00958972.2014.963065

A new hydrazone N′-(3-bromo-2-hydroxybenzylidene)isonicotinohydrazide (H₂L) and its oxovanadium(V) complex, [VOLL′]·2H₂O (L′ = 2-hydroxybenzohydroxamate), were prepared and structurally characterized by physico-chemical, spectroscopic methods, and single-crystal X-ray determination. The hydrazone coordinates to V through the phenolate oxygen, imino nitrogen, and enolate oxygen. The hydroxamate coordinates to V through the carbonyl oxygen and deprotonated hydroxyl oxygen. Vanadium in the complex is octahedral. The oxidation of olefins with the complex as catalyst was evaluated, which indicated that the complex showed catalytic efficiency in oxidation of several aliphatic and aromatic substrates under mild conditions, using tert-butyl hydrogen peroxide as oxidant.

Full text of DOI:10.1080/00958972.2014.963065

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N′-(3-Bromo-2-
hydroxybenzylidene)isonicotinohydrazide
and its oxovanadium(V) complex:
synthesis, structures, and catalytic
properties
a
a
Yan Xiong & Wen-Hui Li
a
College of Chemical Engineering and Pharmacy, Jingchu
University of Technology, Jingmen, PR China
Accepted author version posted online: 08 Sep 2014.Published
online: 25 Sep 2014.
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To cite this article: Yan Xiong & Wen-Hui Li (2014) N′-(3-Bromo-2-
hydroxybenzylidene)isonicotinohydrazide and its oxovanadium(V) complex: synthesis,
structures, and catalytic properties, Journal of Coordination Chemistry, 67:20, 3279-3287, DOI:
10.1080/00958972.2014.963065
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Journal of Coordination Chemistry, 2014
Vol. 67, No. 20, 3279–3287, http://dx.doi.org/10.1080/00958972.2014.963065
N′-(3-Bromo-2-hydroxybenzylidene)isonicotinohydrazide and
its oxovanadium(V) complex: synthesis, structures, and
catalytic properties
YAN XIONG and WEN-HUI LI*
College of Chemical Engineering and Pharmacy, Jingchu University of Technology, Jingmen,
PR China
(Received 14 June 2014; accepted 21 August 2014)
A
new hydrazone N′-(3-bromo-2-hydroxybenzylidene)isonicotinohydrazide (H
2
L) and its
oxovanadium(V) complex, [VOLL′]·2H O (L′ = 2-hydroxybenzohydroxamate), were prepared and
2
structurally characterized by physico-chemical, spectroscopic methods, and single-crystal X-ray
determination. The hydrazone coordinates to V through the phenolate oxygen, imino nitrogen, and
enolate oxygen. The hydroxamate coordinates to V through the carbonyl oxygen and deprotonated
hydroxyl oxygen. Vanadium in the complex is octahedral. The oxidation of olefins with the complex
as catalyst was evaluated, which indicated that the complex showed catalytic efficiency in oxidation
of several aliphatic and aromatic substrates under mild conditions, using tert-butyl hydrogen
peroxide as oxidant.
Keywords: Schiff base; Oxovanadium complex; X-ray diffraction; Catalytic property; Coordination
1. Introduction
The catalytic epoxidation of olefins has been a subject of growing interest in the production
of chemicals and fine chemicals since epoxides are key starting materials for a wide variety
of products [1–3]. Great work has been carried out to explore new and efficient catalysts for
these reactions. H O has been used as the oxidant in these reactions because of its
2
2
environment-friendly characteristic. Vanadium enzymes, such as vanadium-nitrogenases and
*
Corresponding author. Email: liwh066@163.com
2014 Taylor & Francis
©

3
280
Y. Xiong and W.-H. Li
vanadate-dependent haloperoxidases, have been found in nature [4–6]. Vanadium complexes
with various organic ligands have shown interesting catalytic properties in many organic
reactions [7–10]. Hydrazones are a polydentate ligand in coordination chemistry. The syn-
thesis, characterization, and reactivity studies of oxovanadium complexes with hydrazone
ligands have been reported [11–14]. Some of the complexes show interesting catalytic
properties [15–17]. As an extension of work on such fields, and to explore more efficient
oxidization catalysts, in the present article, a new hydrazone, N′-(3-bromo-2-hydroxybenzy-
lidene)isonicotinohydrazide (H L), and its oxovanadium(V) complex, [VOLL′]·2H O
2
2
(L′ = 2-hydroxybenzohydroxamate), were prepared and characterized (scheme 1).
2
2
. Experimental
.1. Materials and physical measurements
All chemical reagents were of analytical reagent grade, purchased from Xiya Chemical
Reagent Company. Microanalyses (C, H, and N) were performed using a Perkin Elmer
2
4
400 elemental analyzer. Infrared spectra were carried out using a JASCO FT-IR model
20 spectrophotometer with KBr disks from 4000 to 200 cm . UV–vis spectra were
−
1
measured with a Perkin Elmer Lambda 18 spectrophotometer. GC analyses were carried out
1
using a Shimadzu GC-2014C gas chromatograph. H NMR spectra were recorded on a
Bruker instrument at 400 MHz.
2
.2. Synthesis of H2L
A hot methanol solution (30 mL) of 3-bromosalicylaldehyde (10 mM, 2.01 g) was added to
a hot methanol solution (30 mL) of isonicotinohydrazide (10 mM, 1.37 g). The mixture
was stirred for 30 min at reflux, and the solvent was evaporated to dryness. Recrystalliza-
tion from methanol gave single crystals of the compound. Yield: 93%. M.p. 163.0–165.0.
Anal. Calcd for C H BrN O (H L): C, 48.8; H, 3.1; N, 13.1. Found: C, 48.7; H, 3.2; N,
1
3
10
3
2
2
1
1
7
3.3%. H NMR (DMSO-d ): δ: 12.61 (s, 1H), 12.39 (s, 1H), 8.82 (s, 2H), 8.61 (s, 1H),
6
.86 (d, 2H), 7.66 (dd, J = 7.9, 1.3 Hz, 1H), 7.57 (dd, J = 7.7, 1.4 Hz, 1H), 6.93 (t, 1H).
2
.3. Synthesis of [VOLL′]·2H O
2
A hot methanol solution (15 mL) of VO(acac) (1 mM, 0.26 g) was added to a hot metha-
2
nol solution (15 mL) of H L (1 mM, 0.32 g). Then, 2-hydroxybenzohydroxamic acid
2
(1 mM, 0.15 g) dissolved in 10 mL of water was added to the solution. The mixture was
stirred for 30 min at reflux, and then cooled to room temperature, to give a brown solution.
Single crystals of the complex, suitable for X-ray diffraction, were formed by slow evapora-
tion of the methanol solution containing the complex in air for few days. Yield: 55%. Anal.
Calcd for C H BrN O V: C, 41.9; H, 3.2; N, 9.8. Found: C, 41.7; H, 3.1; N, 9.9%.
2
0
18
4 8
2
.4. X-ray diffraction
X-ray diffraction was performed using a Bruker APEX2 CCD diffractometer with graphite
monochromated MoKα radiation (λ = 0.71073 Å) using the ω-scan technique. Determina-
tion of the Laue class, orientation matrix, and cell dimensions were performed according to

Oxovanadium(V) complex
3281
the established procedures where Lorentz polarization and absorption corrections were
applied. Absorption corrections were applied by fitting a pseudoellipsoid to the ψ-scan data
of selected strong reflections over a wide range of 2θ angles. The positions of non-hydrogen
atoms were located with direct methods. Subsequent Fourier syntheses were used to locate
the remaining non-hydrogen atoms. All non-hydrogen atoms were refined anisotropically.
The amino H in H L and the water H in the complex were located from difference Fourier
2
maps and refined isotropically. The remaining hydrogens were placed in calculated
positions and constrained to ride on their parent atoms. The analysis was performed with
the aid of SHELXS-97 and SHELXL-97 suite of codes [18, 19]. Crystallographic data for
the complexes are summarized in table 1. Selected bond lengths and angles are given in
table 2.
2
.5. Catalytic oxidation
Catalytic experiments were carried out in a 50 mL glass round-bottom flask fitted with a
reflux condenser and placed in an oil bath at prearranged temperature under continuous stir-
ring. The oxidation was carried out as follows: the complex (0.032 mM) was dissolved in
1
3
0 mL of 1,2-dichloroethane. Then, 10 mM alkene was added to the reaction mixture and
0 mM TBHP was added. The reaction mixture was refluxed for 1 h. The reaction products
were monitored at periodic time intervals using gas chromatography. The oxidation prod-
ucts were identified by comparison with authentic samples (retention times in GC).
2
Table 1. Crystal data for H L and the complex.
1
2
Chemical Formula
Fw
Crystal shape/color
Crystal size (mm)
T (K)
λ (MoKα) (Å)
Crystal system
Space group
a (Å)
C
320.2
Block/colorless
0.20 × 0.20 × 0.17
298(2)
0.71073
Monoclinic
1
P2 /n
10.773(1)
16.131(2)
15.020(2)
109.318(4)
2463.2(4)
8
3.339
1280
0.5548
0.6007
1.727
13
H
10BrN
3
O
2
C
20
H
4 8
18BrN O V
573.2
Block/brown
0.17 × 0.16 × 0.13
298(2)
0.71073
Monoclinic
I2/a
19.8749(3)
11.5570(2)
19.4798(4)
93.179(2)
4467.5(1)
8
2.288
2304
0.6970
0.7552
1.705
b (Å)
c (Å)
β (°)
V (Å )
3
Z
−
1
μ (MoKα) (cm
F (0 0 0)
T (min)
)
T (max)
−
3
D
Calcd (g cm )
Collected reflections
Unique reflections
24,700
4586
28,579
5554
Observed reflections [I ≥ 2σ(I)]
Parameters
3877
351
4322
335
Restraints
Goodness of fit on F
2
9
2
1.040
1.062
R
wR
R
wR
1
[I ≥ 2σ(I)]
[I ≥ 2σ(I)]
(all data)
2
(all data)
0.0276
0.0646
0.0370
0.0683
0.0389
0.0946
0.0587
0.1036
2
1

3
282
Y. Xiong and W.-H. Li
Table 2. Selected bond lengths (Å) and angles (°) for H
2
L and the complex.
2
H L
Bond lengths
C7–N1
N2–C8
C20–N4
N5–C21
1.275(3)
1.353(3)
1.274(3)
1.355(3)
N1–N2
C8–O2
N4–N5
C21–O4
1.379(2)
1.212(3)
1.380(2)
1.209(3)
The complex
Bond lengths
V1–O1
V1–O3
V1–O6
1.8754(13)
1.8719(13)
1.5868(14)
1.287(3)
V1–O2
V1–O4
V1–N1
N1–N2
C8–O2
1.9679(13)
2.1849(13)
2.0884(17)
1.399(2)
C7–N1
N2–C8
1.299(3)
1.301(2)
Bond angles
O6–V1–O3
O3–V1–O1
O3–V1–O2
O6–V1–N1
O1–V1–N1
O6–V1–O4
O1–V1–O4
N1–V1–O4
93.37(7)
109.66(6)
89.18(6)
94.55(7)
83.90(6)
168.03(6)
80.70(5)
97.12(6)
O6–V1–O1
O6–V1–O2
O1–V1–O2
O3–V1–N1
O2–V1–N1
O3–V1–O4
O2–V1–O4
97.94(7)
102.94(6)
150.95(6)
163.18(6)
74.59(6)
76.07(5)
82.83(5)
3. Results and discussion
The hydrazone ligand H L was readily prepared by condensation of equimolar quantities of
2
3
-bromosalicylaldehyde with isonicotinohydrazide in methanol. The complex was
synthesized by reaction of VO(acac) with H L and 2-hydroxybenzohydroxamic acid in
2
2
methanol in a 1 : 11 M proportion at reflux. Chemical formulas of the compounds have
been confirmed by elemental analyses, IR spectra, and X-ray single-crystal structure
determination.
3
.1. Structure description of H L and the complex
2
Molecular structures of H L and the complex are presented in figures 1 and 2, respectively.
2
There are two independent molecules in the asymmetric unit of H L. In both molecules of
2
H L, the intramolecular O–H⋯N hydrogen bonds (table 3) make S(6) ring motifs [20]. The
2
dihedral angles between the benzene and the pyridine rings of both molecules are 15.2(3)°
and 22.5(3)°. The hydrazone coordinates to V through the phenolate oxygen, imino nitro-
gen, and enolate oxygen. The 2-hydroxybenzohydroxamate ligand coordinates through the
carbonyl oxygen and hydroxy oxygen. The coordination geometry around V can be
described as distorted octahedral, with the three donors of the hydrazone and the hydroxy
oxygen of 2-hydroxybenzohydroxamate ligand defining the equatorial plane, and with the
carbonyl oxygen of 2-hydroxybenzohydroxamate occupying one axial position. The other
axial position of the octahedral coordination is furnished with an oxo. The hydrazone ligand
coordinates to V in a meridional fashion forming five- and six-membered chelate rings with
bite angles of 74.59(6)° and 83.90(6)°, which are similar to those observed in similar vana-
dium complexes [21, 22]. The displacement of V from the equatorial mean plane towards
the axial oxo is 0.233(2) Å. The hydrazone is coordinated in its dianionic enolate form,
which is evident from the bond lengths of C8–O2 [1.301(2) Å] and C8–N2 [1.299(3) Å] in

Oxovanadium(V) complex
3283
Figure 1. Molecular structure of H
2
L with 30% probability thermal ellipsoids.
Figure 2. Molecular structure of the complex with 30% probability thermal ellipsoids.
the complex. The C8–O2 bond is much longer than the corresponding bonds (1.21 Å) in
H L. The C8–N2 bond in the complex is much shorter than the corresponding bonds (1.35
2
Å) in H L. In addition, the C7–N1 [1.287(3) Å] in the complex is much longer than the
2
corresponding value (1.27 Å) in H L. This indicates coordination through the imino
2
nitrogen. The dihedral angle between the benzene and the pyridine rings of the hydrazone
ligand of the complex is 13.8(3)°. The V–O, V–N, and V=O bonds in the complex are
within normal ranges and similar to those observed in oxovanadium complexes with
octahedral coordination [21–23].

3
284
Y. Xiong and W.-H. Li
Table 3. Distances (Å) and angles (°) involving hydrogen bonding of H
2
L and the complex.
D–H⋯A
d(D–H)
d(H⋯A)
d(D⋯A) Angle (D–H⋯A)
2
H L
O1–H1⋯N1
O3–H3⋯N4
N5–H5⋯N3
N2–H2⋯N6
0.82
0.82
0.90(1)
0.90(1)
1.92
1.95
2.26(1)
2.28(1)
2.641(2)
2.665(2)
3.152(3)
3.160(3)
146
146
174(3)
169(3)
i
The complex
O9–H9B⋯N2
O8–H8B⋯N2
ii
0.96
0.96
0.96
0.96
0.96
0.96
0.84
0.88
0.88
2.128(2)
1.845(7)
2.21(1)
1.878(2)
2.022(2)
1.998(2)
1.75
3.000(2)
2.755(2)
3.032(2)
2.828(2)
2.871(2)
2.832(2)
2.591(2)
3.099(2)
2.587(2)
151
158
143
171
147
144
173
132
131
iii
O8–H8A⋯O4
iv
O7–H7B⋯N3v
O7–H7A⋯O9
iii
O7–H7A⋯O9
vi
O5–H5⋯O7
vii
N4–H4⋯O2
2.44
1.92
N4–H4⋯O5
Note: Symmetry codes: (i) −1 + x, y, z; (ii) 3/2 + x, 1/2 + y, 3/2 + z; (iii) 1 − x, 1 − y, 1 − z; (iv) 1 − x, 1/2 + y,
/2 − z; (v) −1/2 + x, 1 − y, z; (vi) x, −1 + y, z; (vii) 1 − x, −y, 1 − z.
3
2
Figure 3. Molecular packing of H L. Hydrogen bonds are drawn as thin dashed lines.
In the crystal structures of both H L and the complex, molecules are linked through
2
intermolecular hydrogen bonds (table 3), to form 3-D networks (figure 3 for H L, figure 4
2
for the complex).
3.2. IR and UV–vis spectra
The hydrazone shows stretching bands attributed to C=O, C=N, C–OH, and NH at 1685,
−1
1
617, 1146, and 3203 cm , respectively. For the complex, the weak and sharp band

Oxovanadium(V) complex
3285
Figure 4. Molecular packing of the complex. Hydrogen bonds are drawn as thin dashed lines.
N
N
H
N
N
N
N
O
O
O
OH
V
O
Br
VO(acac)2
+
Br
2H O
2
O
+
O
O
NH
OH
N
OH
H
OH
Scheme 1. The preparation of the complex.
−
1
indicative of the NH vibration is at 3277 cm , and the weak and broad band indicative of
−
1
the OH vibrations of water is centered at 3445 cm . The strong band indicative of the
−
1
C=N group of the complex is located at 1605 cm . The V=O stretch occurs as a single
−
1
sharp band at 985 cm
(
[24]. The weak peaks observed at low wave numbers
−1
400–600 cm ) may be attributed to the V–O and V–N vibrations.
In the UV–vis region, H L shows bands at 215, 295, and 335 nm, and the complex
2
shows bands at 221, 260, 350, and 450 nm. Weak bands at 400–500 nm were attributed to
ligand-to-metal charge transfer from the p orbital on the phenolate oxygen to the empty d
π
orbitals of the vanadium ion [25]. The bands in the region 310–350 nm for H L and the
2
complex were assigned to n–π* transitions [26]. The intense bands at 210–300 nm were
assigned to intra-ligand π–π* transitions [26].

3
286
Y. Xiong and W.-H. Li
a
Table 4. Catalytic oxidation of olefins catalyzed by the complex.
b
Substrate
Product
Conversion (%)
7
4
6
8
7
0
7
8
7
7
9
9
0
6
9
1
a
The molar ratio of catalyst : substrate : TBHP is 1 : 300 : 1000. The reactions were
OH/CH Cl (V: V = 6 : 4; 1.5 mL).
The GC conversion (%) was measured relative to the starting substrate after 1 h.
performed in the mixture of CH
3
2
2
b
3.3. Catalytic oxidation results
The catalytic results are listed in table 4. Effective epoxide yields and 100% selectivity were
observed for all aliphatic and aromatic substrates. In general, oxidation of aromatic sub-
strates gave the corresponding epoxides in over 85% yields, while in the oxidation of
aliphatic substrates, the conversion is lower than 80%. Based on this, isolated double bonds
are less reactive than conjugated ones. For the aliphatic substrates, the conversion for the
chloro-substituted methyloxirane is higher than the methyl or ethyl substituted species. For
the aromatic substrates, the same phenomenon was observed. Thus, the complex has good
catalytic properties on the chloro-substituted substrates.
4
. Conclusion
A new hydrazone N′-(3-bromo-2-hydroxybenzylidene)isonicotinohydrazide was prepared
and characterized. Based on this compound, a new oxovanadium(V) complex with
2
-hydroxybenzohydroxamate as the co-ligand was prepared and characterized. Coordination
of the ligand to V was discussed. The hydrazone ligand coordinates through the phenolate

Oxovanadium(V) complex
3287
oxygen, imino nitrogen, and enolate oxygen. The complex is an effective catalyst for the
oxidation of various aliphatic and aromatic olefins, especially for the chloro-substituted
substrates.
Supplementary material
CCDC 1006767 for H L and 1006768 for the complex contain the supplementary crystallo-
2
graphic data. These data can be obtained free of charge via http://www.ccdc.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data Center, 12 Union Road,
Cambridge CB2 1EZ, UK; Fax: +44 1223 336 033; or Email: deposit@ccdc.cam.ac.uk.
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