Two new oxovanadium(V) complexes with hydrazone ligands: Synthesis, characterization, and structure

Article abstract of DOI:10.1080/15533174.2011.555873

The reaction of [VO(acac)₂] with 3-methyl-N'-[1-(2- hydroxynaphthyl)ethylidene]benzohydrazide (H₂L¹) and 3-methyl-N'-[(2-hydroxy-1-naphthyl)methylidene]benzohydrazide (H ₂L²), respectively, in methanol affords two new oxovanadium(V) complexes, [VO(OMe)L¹]₂ (1) and [VO(OMe)(HOMe)L²] (2). Both complexes have been characterized by elemental analysis, I.R., and single crystal X-ray diffraction methods. Complex (1) is a methoxide-bridged dinuclear oxovanadium(V) compound, while complex (2) is a mononuclear oxovanadium(V) compound. The dinegative hydrazone ligands coordinate to the metal atoms through phenolate, imine, and deprotonated amine donor atoms. The geometry around each vanadium atom is a distorted VNO5 octahedron in both complexes. Copyright Taylor & Francis Group, LLC.

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Synthesis and Reactivity in Inorganic, Metal-Organic,
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Two New Oxovanadium(V) Complexes with
Hydrazone Ligands: Synthesis, Characterization, and
Structure
Ning Wang a
a Department of Chemical Engineering , Henan University of Urban Construction ,
Pingdingshan, P. R. China
Published online: 22 Apr 2011.
To cite this article: Ning Wang (2011) Two New Oxovanadium(V) Complexes with Hydrazone Ligands: Synthesis,
Characterization, and Structure, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:4,
378-383
To link to this article: http://dx.doi.org/10.1080/15533174.2011.555873
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:378–383, 2011
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.555873
Two New Oxovanadium(V) Complexes with Hydrazone
Ligands: Synthesis, Characterization, and Structure
Ning Wang
Department of Chemical Engineering, Henan University of Urban Construction, Pingdingshan,
P. R. China
EXPERIMENTAL
The reaction of [VO(acac)2] with 3-methyl-Nꢀ-[1-(2-
Materials and Methods
hydroxynaphthyl)ethylidene]benzohydrazide (H2L1) and 3-
methyl-Nꢀ-[(2-hydroxy-1-naphthyl)methylidene]benzohydrazide
(H2L2), respectively, in methanol affords two new oxovanadium(V)
complexes, [VO(OMe)L1]2 (1) and [VO(OMe)(HOMe)L2] (2).
Both complexes have been characterized by elemental analysis,
I.R., and single crystal X-ray diffraction methods. Complex (1)
is a methoxide-bridged dinuclear oxovanadium(V) compound,
while complex (2) is a mononuclear oxovanadium(V) compound.
The dinegative hydrazone ligands coordinate to the metal atoms
through phenolate, imine, and deprotonated amine donor atoms.
The geometry around each vanadium atom is a distorted VNO5
octahedron in both complexes.
2-Acetyl-1-naphthol, 2-hydroxy-1-naphthaldehyde, and 3-
methylbenzhydrazide were purchased from Aldrich Chemical
Co. All other reagent-grade chemicals and reagents were pur-
chased commercially and used without further purification. El-
emental analyses (C, H, N) were obtained with a Perkin-Elmer
model 240C instrument. I.R. spectra were recorded in KBr discs
on a Nicolet 170SX spectrophotometer.
Synthesis of the Hydrazone Compounds
H2L1: A mixture of 2-acetyl-1-naphthol (1.86 g, 10 mmol)
and 3-methylbenzhydrazide (1.50 g, 10 mmol) in 100 mL of
methanol was refluxed for 1 h. After reducing the solvent to
20 mL by distillation, and cooling to room temperature, the
precipitated white solid was filtered off, washed with methanol,
and dried in air. Recrystallization from methanol yielded pure
product of H2L1. Yield 2.70 g (85%). Found: C, 75.37, H, 5.78;
N, 8.72. Calc. for C20H18N2O2: C, 75.45; H, 5.70; N, 8.80. IR
(KBr, cm−1): 3437 (br, w), 3223 (m), 1640 (s), 1611 (m), 1602
(w), 1583 (m), 1560 (w), 1468 (m), 1413 (w), 1393 (w), 1364
(w), 1332 (m), 1291 (s), 1242 (w), 1213 (m), 1181 (m), 1137
(w), 963 (m), 845 (w), 827 (m), 787 (m), 747 (s), 672 (w), 663
(w).
Keywords crystal structure, hydrazone, synthesis, vanadium
INTRODUCTION
Oxovanadium(V) complexes with N- and O-containing
ligands have been extensively investigated in recent years
with respect to their remarkable efficiency as insulin mimetic
compounds.[1−3] The interaction of simple vanadium species
with ligands having pharmacological activity is of particular
interest. Hydrazone compounds have been widely used as
versatile ligands in coordination chemistry,[4−6] and they have
shown interesting biological properties, such as antibacterial,
antitumor, and antifungi activities.[7−9] In the present article,
we describe the synthesis, spectroscopic characterization, and
crystal structure determination of two new oxovanadium(V)
complexes with similar tridentate hydrazone ligands, 3-
methyl-Nꢀ-[1-(2-hydroxynaphthyl)ethylidene]benzohydrazide
(H2L1) and 3-methyl-Nꢀ-[(2-hydroxy-1-naphthyl)methylidene]
benzohydrazide (H2L2) (Scheme 1).
H2L2: This compound was prepared by following the same
procedure outlined for H2L1. The pure product was obtained as
a white solid. Yield 2.65 g (87%). Found: C, 74.82, H, 5.36;
N, 9.27. Calc. for C19H16N2O2: C, 74.98; H, 5.30; N, 9.20. IR
(KBr, cm−1): 3448 (br, w), 3210 (m), 1645 (s), 1624 (m), 1602
(w), 1582 (m), 1560 (w), 1469 (m), 1415 (w), 1392 (w), 1364
(w), 1336 (m), 1297 (s), 1243 (w), 1215 (m), 1189 (m), 1143
(w), 1102 (w), 1031 (w), 960 (m), 859 (w), 822 (m), 799 (m),
745 (s), 689 (w), 651 (w), 546 (w).
Synthesis of the Vanadium(V) Complexes
[VO(OMe)L1]2 (1): [VO(acac)2] (0.263 g, 1.0 mmol) dis-
solved in 20 mL methanol was added dropwise to a methanol
solution (10 mL) of H2L1 (0.318 g, 1.0 mmol) with stirring,
and then the mixture was heated at reflux with stirring for
Received 3 September 2010; accepted 6 October 2010.
Address correspondence to Ning Wang, Department of Chemical
Engineering, Henan University of Urban Construction, Pingdingshan
467044, P. R. China. E-mail: wangning7903@yahoo.com.cn
378

TWO NEW OXOVANADIUM(V) COMPLEXES
379
TABLE 1
R
Crystallographic data for the complexes
H
N
N
(1)
(2)
O
Formula
Mr
C42H38N4O8V2
828.6
C21H21N2O5V
432.3
OH
Crystal size (mm)
Crystal system
Space group
0.23 × 0.20 × 0.20 0.30 × 0.27 × 0.27
R = Me for H2L1 and R = H for H2L2
Triclinic
P -1
Monoclinic
P 21/n
SCH. 1. The hydrazone ligands.
˚
a (A)
7.8730(16)
10.962(2)
11.360(2)
87.03(3)
86.20(3)
73.35(3)
936.7(3)
1
12.796(2)
8.6638(14)
18.840(3)
90
108.208(2)
90
˚
b (A)
˚
c (A)
α (◦)
β (◦)
γ (◦)
1 h and cooled to room temperature. When the solution was
allowed to stand at room temperature for a few days to slow
evaporation of the solvent, X-ray quality deep-red block-shaped
single crystals were collected by filtration. The crystals were
washed with methanol and dried in air. Yield 0.372 g (90%).
Found: C, 60.67; H, 4.73; N, 6.83. Calc. for C42H38N4O8V2:
C, 60.88; H, 4.62; N, 6.76. IR (KBr, cm−1): 1617 (w), 1592
(s), 1570 (s), 1538 (s), 1509 (m), 1449 (w), 1425 (s), 1371 (s),
1356 (m), 1337 (m), 1298 (w), 1287 (w), 1246 (s), 1214 (m),
1025 (s), 984 (s), 965 (m), 823 (m), 804 (w), 783 (w), 766 (w),
748 (m), 723 (s), 678 (w), 617 (s), 598 (s), 514 (w), 468 (w),
426 (w).
3
˚
V (A )
Z
1984.1(6)
4
Dc (g/cm3)
1.469
1.447
µ (mm−1
F (000)
)
0.560
0.536
428
896
Temperature (K)
Tmin
298(2)
298(2)
0.8820
0.8559
Tmax
0.8962
0.8689
Reflections measured
Independent reflections (Rint
Observed reflections
Goodness of fit on F2
Final R indices [I ≥ 2σ(I)]a
7790
15450
)
3888
4241
3338
3376
[VO(OMe)(HOMe)L2] (2): This complex was prepared by
following the same procedure outlined for (1). The X-ray qual-
ity deep-red block-shaped single crystals were obtained. Yield
0.323 g (75 %). Found: C, 58.16, H, 4.97; N, 6.60. Calc. for
C21H21N2O5V: C, 58.34; H, 4.90; N, 6.48. IR (KBr, cm−1):
3469 (br, w), 1616 (m), 1599 (s), 1546 (s), 1511 (s), 1478 (w),
1452 (m), 1421 (m), 1385 (m), 1361 (w), 1327 (s), 1284 (m),
1244 (w), 1223 (w), 1193 (w), 1143 (w), 1093 (w), 1046 (s),
1020 (m), 973 (s), 865 (m), 832 (m), 785 (w), 755 (s), 726 (m),
682 (w), 636 (s), 589 (s), 517 (w), 425 (w).
1.015
1.034
R1 = 0.0388
wR2 = 0.1004
R1 = 0.0456
wR2 = 0.1046
R1 = 0.0461
wR2 = 0.1112
R1 = 0.0608
wR2 = 0.1196
R indices (all data)a
ꢀ
ꢀ
ꢀ
aR1
w(Fo2)2]1/2
=
||Fo| − |Fc||/ |Fo|, wR2 = [ w(Fo2 − Fc2)2/
ꢀ
RESULTS AND DISCUSSION
The hydrazone compounds were prepared by the con-
densation of similar carbonyl-containing compounds with 3-
methylbenzhydrazide in methanol. Each of them has two disso-
ciable protons at the phenolic-OH and the amide functionality.
The reaction of bis(acetylacetonato)oxovanadium(IV) with sto-
ichiometric amounts of the hydrazone ligands in methanol in
air afforded the two vanadium(V) complexes as deep-red crys-
talline solids. It should be pointed out that the vanadium in the
starting materials is in V(IV) oxidation state, but it appears to
be V(V) in both complexes, indicating that it was oxidized by
air during the reaction procedures. Elemental analyses of the
complexes are satisfactory with the empirical formulae.
X-ray Structure Determination
The crystal and instrumental parameters used in the unit cell
determination and data collection are summarized in Table 1.
Diffraction measurements were made at room temperature on a
Bruker SMART APEX II X-ray diffractometer using graphite-
monochromated Mo Kα radiation using ω scan mode. Unit-cell
dimensions were determined and refined in the range 1.80–
27.00◦ for (1) and 1.71–27.00◦ for (2). Both structures were
solved by the direct methods using SHELXS-97 and refined
by full-matrix least-squares techniques on F2 with SHELXL-
97.[10] The empirical absorption corrections were applied by
the multi-scan method.[11] All non-hydrogen atoms were re-
fined with anisotropic displacement parameters. The methanol
H atom in (2) was located in a difference Fourier map, and
Spectra Characterization of the Complexes
The I.R. spectra of the ligands exhibit two bands in the re-
gions 3210–3230 and 1640–1645 cm−1 due to the ν(N-H) and
v(C=O) stretches.[12] The absence of these bands in the spec-
tra of the complexes is consistent with the enolisation of the
amide functionality and subsequent proton replacement by the
vanadium atom. A broad and weak band observed at 3469 cm−1
in the infrared spectrum of (2) due to the O-H stretch of the
refined isotropically, with O–H distance restrained to 0.85(1)
2
˚
˚
A, and with Uiso restrained to 0.08 A . The remaining hydro-
gen atoms were included in their idealized positions an◦d refined
˚
isotropically. Selected bond distances (A) and angles ( ) for the
complexes are listed in Table 2.

380
N. WANG
FIG. 1. Molecular structure of (1) with 30% thermal ellipsoids. Unlabelled atoms are related to the symmetry operation – x, 1 – y, 2 – z.
. . .
coordinated MeOH is absent in the spectrum of (1). A new band
appearing in the 1244–1287 cm−1 range is assigned to the ν(C-
O)(enolic) mode. The strong bands at 1592 and 1599 cm−1 in
complexes (1) and (2), respectively, with shoulders are assigned
to the conjugate C=N-N=C moieties.[13]The bands observed at
984 and 973 cm−1 for (1) and (2), respectively, are assigned to
the V=O stretch.[12,14]
˚
vanadium(V) compound. The V V distance is 3.363(2) A.
The dianionic tridentate hydrazone ligand binds the metal atom
through the phenolate-O, imine-N, and deprotonated amide-O
atoms, forming a six- and a five-membered chelate rings, which
are inclined to each other by 15.5(3)◦. Each V atom is in a dis-
torted NO5 octahedral coordination, with the three donor atoms
of the hydrazone ligand and one methoxide O atom defining the
equatorial plane, and with one oxo O and one symmetry-related
methoxide O atom occupying the axial positions. The mean de-
viation of the four equatorial donor atoms from the least-squares
Structure Description of (1)
The molecular structure of (1) is shown in Figure 1. The com-
plex is a methoxide oxygen-bridged centrosymmetric dinuclear
˚
plane is 0.010(3) A. The displacement of the V atom towards
FIG. 2. Molecular packing of (1), viewed along the a axis.

TWO NEW OXOVANADIUM(V) COMPLEXES
381
FIG. 3. Molecular structure of (2) with 30% thermal ellipsoids.
˚
the oxo group from the plane is 0.355(2) A. The distances of
V=O and other coordination bonds in the complex are within
the range of similar vanadium(V) complexes.[15,16]
TABLE 2
◦
˚
Selected bond lengths (A) and bond angles ( ) for the
complexes
In the crystal structure of (1), molecules are stacked along
the a axis, with no obvious short contacts (Figure 2).
(1)
(2)
V1-O1
V1-O2
V1-O3
V1-O4
V1-O4A
V1-N1
1.8361(15)
1.9210(16)
1.5844(16)
2.3556(15)
1.8261(15)
2.0941(17)
150.00(7)
101.05(8)
100.55(8)
103.22(8)
103.46(6)
91.53(7)
97.14(8)
157.23(7)
82.24(7)
74.63(7)
176.76(6)
73.64(6)
V1-O1
V1-O2
V1-O3
V1-O4
V1-O5
V1-N1
1.8649(17)
1.9579(16)
1.5795(17)
2.3422(18)
1.7646(18)
2.1041(19)
151.82(7)
99.16(9)
Structure Description of (2)
The molecular structure of (2) is shown in Figure 3. The
methoxide ligand lies trans to the imine-N atom. The methanol
ligand is coordinated trans to the oxo group. The dianionic
tridentate hydrazone ligand binds the metal atom through the
phenolate-O, imine-N, and deprotonated amide-O atoms, form-
ing a six- and a five-membered chelate rings, which are inclined
to each other by 11.4(3)◦. The V atom is in a distorted NO5
octahedral coordination, with the three donor atoms of the hy-
drazone ligand, and one methoxide O atom defining the equa-
torial plane, and with one oxo O and one methanol O atom
occupying the axial positions. The mean deviation of the four
equatorial donor atoms from the least-squares plane is 0.017(3)
O1-V1-O2
O3-V1-O1
O3-V1-O2
O3-V1-O4A
O4A-V1-O1
O4A-V1-O2
O3-V1-N1
O4A-V1-N1
O1-V1-N1
O2-V1-N1
O3-V1-O4
O4-V1-O4A
O1-V1-O4
O2-V1-O4
N1-V1-O4
O1-V1-O2
O3-V1-O1
O3-V1-O2
O3-V1-O5
O5-V1-O1
O5-V1-O2
O3-V1-N1
O5-V1-N1
O1-V1-N1
O2-V1-N1
O3-V1-O4
O5-V1-O4
O1-V1-O4
O2-V1-O4
N1-V1-O4
98.61(8)
102.09(9)
102.85(8)
94.57(8)
94.63(8)
161.16(8)
82.74(7)
74.17(7)
174.72(8)
82.25(7)
82.65(7)
77.90(7)
˚
A. The displacement of the V atom towards the oxo group from
˚
the plane is 0.296(2) A. The distances of V=O and other coor-
dination bonds in the complex are within the range of similar
vanadium(V) complexes.[17−19]
In the crystal structure of (2), adjacent two molecules are
linked through intermolecular O–H· · ·N hydrogen bonds (O4–
79.12(6)
80.48(6)
86.10(6)
˚
˚
H4A = 0.847(10) A, H4A· · ·N2 = 1.994(12) A, O4· · ·N2
80.64(7)
◦
˚
= 2.833(3) A; O4-H4A-N2 = 170(3) ), forming a dimer
Symmetry code for A: – x, 1 – y, 2 – z.
(Figure 4).

382
N. WANG
FIG. 4. Hydrogen bonded dimers of (2), viewed along the b axis.
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