Synthesis, characterization, and crystal structures of two dioxovanadium(V) complexes with schiff bases

Article abstract of DOI:10.1080/15533174.2010.522670

Two new dioxovanadium(V) complexes, [VO₂L1]₂ (1) and [VO₂L2] (2), where L1 and L2 are the deprotonated forms of 4-chloro-2-[(2-isopropylaminoethylimino)methyl]phenol and 4-chloro-2-[(2- morpholin-4-ylethylimino)methyl]phen

Full text of DOI:10.1080/15533174.2010.522670

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Synthesis, Characterization, and Crystal Structures
of Two Dioxovanadium(V) Complexes with Schiff
Bases
Shi-Yong Liu a , Ren-Hua Zheng a , Yu-Ping Ma b & Zhonglu You b
a College of Chemistry & Pharmacy , Taizhou University , Taizhou Zhejiang, P. R. China
b Department of Chemistry , Liaoning Normal University , Dalian, P. R. China
Published online: 02 Feb 2011.
To cite this article: Shi-Yong Liu , Ren-Hua Zheng , Yu-Ping Ma & Zhonglu You (2011) Synthesis, Characterization, and
Crystal Structures of Two Dioxovanadium(V) Complexes with Schiff Bases, Synthesis and Reactivity in Inorganic, Metal-
Organic, and Nano-Metal Chemistry, 41:1, 22-25
To link to this article: http://dx.doi.org/10.1080/15533174.2010.522670
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:22–25, 2011
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.522670
Synthesis, Characterization, and Crystal Structures of Two
Dioxovanadium(V) Complexes with Schiff Bases
Shi-Yong Liu,1 Ren-Hua Zheng,1 Yu-Ping Ma,2 and Zhonglu You2
1College of Chemistry & Pharmacy, Taizhou University, Taizhou Zhejiang, P. R. China
2Department of Chemistry, Liaoning Normal University, Dalian, P. R. China
chloro-2-[(2-isopropylaminoethylimino)methyl]phenol and 4-
chloro-2-[(2-morpholin-4-ylethylimino)methyl]phenol, respec-
tively, were synthesized and characterized.
Two new dioxovanadium(V) complexes, [VO2L1]2 (1) and
[VO2L2] (2), where L1 and L2 are the deprotonated
forms of 4-chloro-2-[(2-isopropylaminoethylimino)methyl]phenol
and 4-chloro-2-[(2-morpholin-4-ylethylimino)methyl]phenol, re-
spectively, have been synthesized and characterized by IR spec-
tra and single crystal X-ray diffraction. Complex (1) is a cen-
EXPERIMENTAL
trosymmetric dinuclear dioxovanadium complex, with the V atom Materials and Measurements
six-coordinate in an octahedral geometry. The V· · ·V distance is
All chemicals used were commercially available with AR
˚
3.224(2) A. Complex (2) is a mononuclear dioxovanadium complex,
grade. Elemental analyses (CHN) were performed using a
Perkin-Elmer 240 elemental analyzer. The IR spectra were mea-
sured with a Nicolet FT-IR 170-SX spectrophotometer using
KBr pellets in the 4000–400 cm−1 region.
with the V atom five-coordinate in a distorted square pyramidal
geometry. The steric effects of the terminal groups in the Schiff
base ligands can influence the structures of the complexes.
Keywords synthesis, vanadium complex, Schiff base, crystal struc-
ture
Synthesis of the Schiff Bases HL1 and HL2
The two Schiff bases were synthesized according to
the general method. A methanol solution (50 mL) of 5-
chlorosalicylaldehyde (1.0 mmol, 156.5 mg) was added drop-
wise to a stirred methanol solution (50 mL) of organic amines
(1.0 mmol; N-isopropylethane-1,2-diamine for HL1 and 2-
morpholin-4-ylethylamine for HL2). The mixture was stirred
for 30 minutes and most of the solvent was then evaporated
to give a yellow precipitate. The precipitate was filtered out,
washed with cold methanol, and dried in a vacuum over an-
hydrous CaCl2. Yield: 72% for HL1 and 85% for HL2. Anal.
Calcd. for HL1: C, 59.9; H, 7.1; N, 11.6%. Found: C, 59.7; H,
7.2; N, 11.7%; for HL2: C, 58.1; H, 6.4; N, 10.4%. Found: C,
58.2; H, 6.4; N, 10.2%. Selected i.r. data (KBr, cm−1): HL1,
3230 (νN−H), 1637 (νC=N); HL2, 1635 (νC=N).
INTRODUCTION
Considerable interest has been focused on the Schiff bases
and their metal complexes in the fields of coordination chem-
istry and biological chemistry.[1−3] In the last few years, the
vanadium complexes have been reported to have interesting
biological activities such as normalizing the high blood glu-
cose levels and acting as models of haloperoxidases.[4−6] It
has been known that there exists trigonal bipyramidal vana-
dium within the phosphate-metabolizing enzyme.[7,8] Mokry
and co-workers reported that the steric bulk of the substituent
of the benzene ring can be used to modify the coordination
geometry and/or number of vanadium atoms by preventing
dimerization pathways.[9] To further explore the role in the
synthesis of such complexes, in this article, two new diox-
ovanadium(V) complexes, [VO2L1]2 (1) and [VO2L2] (2),
where L1 and L2 (Scheme 1) are the deprotonated form of 4-
Synthesis of the Complex [VO2L1]2 (1)
A methanol solution (5 mL) of VO(acac)2 (0.1 mmol,
26.5 mg) was added to a methanol solution (10 mL) of HL1
(0.1 mmol, 24.0 mg) under stirring. The mixture was stirred
at room temperature for 30 min to give a yellow solution. The
resulting solution was allowed to stand in air for a few days. The
yellow block-shaped crystals suitable for X-ray single crystal
diffraction were formed at the bottom of the vessel. The isolated
product was washed with cold methanol, and dried in air. Yield:
54%.
Received 8 June 2010; accepted 28 July 2010.
The authors acknowledge the Zhejiang Provincial Natural Science
Foundation of China (project no. Y4090281) for funding this work.
Address correspondence to Shi-Yong Liu, College of Chemistry &
Pharmacy, Taizhou University, Taizhou Zhejiang 317000, P. R. China.
E-mail: liushiyong2010@yahoo.cn
22

TWO DIOXOVANADIUM(V) COMPLEXES WITH SCHIFF BASES
23
SCH. 1. L1 and L2.
˚
Synthesis of the Complex [VO2L2] (2)
with N−H distance restrained to 0.90(1) A, and with Uiso(H) set
2
˚
A methanol solution (5 mL) of VO(acac)2 (0.1 mmol, 26.5
mg) was added to a methanol solution (10 mL) of HL2 (0.1
mmol, 26.8 mg) under stirring. The mixture was stirred at room
temperature for 30 min to give a yellow solution. The result-
ing solution was allowed to stand in air for a few days. The
yellow block-shaped crystals suitable for X-ray single crystal
diffraction were formed at the bottom of the vessel. The isolated
product was washed with cold methanol, and dried in air. Yield:
71%.
to 0.08 A . Other H atoms in the complexes were placed in cal-
culated positions and constrained to ride on their parent atoms.
The crystallographic data for the complexes are summarized in
Table 1. Selected bond lengths and angles are listed in Table 2.
RESULTS AND DISCUSSION
Preparation of the Schiff Bases and the Complexes
The Schiff bases HL1 and HL2 were prepared via the reac-
tion of equimolar quantities of 5-chlorosalicylaldehyde with N-
isopropylethane-1,2-diamine and 2-morpholin-4-ylethylamine,
respectively, in methanol. The two complexes were readily syn-
thesized according to the standard procedure (Scheme 2), crys-
tallized as yellow crystals, which are stable in air at room tem-
perature. The crystals of the complexes are soluble in DMSO,
DMF, MeCN, MeOH and EtOH, insoluble in water.
Crystal Structure Determination
Diffraction intensities for the complex were collected at
298(2) K using a Bruker SMART 1000 CCD area-detector
˚
with MoKα radiation (λ = 0.71073 A). The collected data
were reduced using the SAINT program,[10] and empirical
absorption corrections were performed using the SADABS
program.[11] The structure was solved by direct methods and
refined against F2 by full-matrix least-squares methods using
the SHELXTL package.[12] All of the non-hydrogen atoms were
refined anisotropically. H2 atom attached to N2 in (1) was lo-
Spectra Characterization of the Complexes
The IR spectra of the two materials are similar, but not iden-
cated from a difference Fourier map and refined isotropically, tical. IR spectra of solid complexes show strong bands at 929
SCH. 2. The synthesis of the complexes.

24
S.-Y. LIU ET AL.
TABLE 1
Crystal data for the complexes
TABLE 2
◦
˚
Selected bond lengths (A) and bond angles ( ) for the
complexes
(1)
(2)
(1)
Formula
FW
C24H32Cl2N4O6V2 C13H16ClN2O4V
V1-O1
V1-O3i
V1-N1
1.9275(17)
1.6653(16)
2.162(2)
V1-O2
V1-O3
V1-N2
O2-V1-O1
O2-V1-N1
O1-V1-N1
O3i-V1-N2
N1-V1-N2
O3-V1-O3i
N1-V1-O3
1.6063(18)
2.4152(18)
2.181(2)
645.3
350.7
Crystal shape/color
Crystal system
Space group
Block/yellow
Monoclinic
P21/c
Block/yellow
Monoclinic
P21/c
O2-V1-O3i 106.89(9)
100.27(9)
O3i-V1-O1
O3i-V1-N1 150.99(8)
98.66(8)
100.82(8)
84.51(7)
92.64(8)
76.68(7)
77.18(7)
74.22(6)
˚
a /A
12.455(3)
12.378(3)
9.296(2)
107.518(3)
1366.7(6)
2
20.931(5)
6.098(2)
11.347(3)
97.608(3)
1435.7(6)
4
˚
b /A
O2-V1-N2
O1-V1-N2
O2-V1-O3
O1-V1-O3
N2-V1-O3
94.22(9)
158.12(8)
171.21(8)
86.61(7)
77.67(7)
˚
c /A
β /◦
V /A
3
˚
Z
T /K
298(2)
298(2)
(2)
V1-O1
V1-O4
V1-N2
O4-V1-O3
O3-V1-O1
O3-V1-N1
O4-V1-N2
O1-V1-N2
Dc/g cm−3
F(000)
1.568
1.622
1.9125(15)
1.6127(15)
2.1596(16)
V1-O3
V1-N1
1.6277(16)
2.1476(15)
664
720
µ/mm−1 (Mo-Kα)
Tmin
Tmax
0.926
0.893
0.815
0.821
109.37(9)
O4-V1-O1
O4-V1-N1
O1-V1-N1
O3-V1-N2
N1-V1-N2
102.88(8)
0.836
0.841
98.62(8)
132.64(7)
94.80(7)
116.32(8)
83.22(6)
89.47(7)
75.37(6)
Reflections/parameters 2974/177
Independent reflections 2267
3137/190
2631
Restraints
1
0
156.74(6)
Goodness of fit on F2 1.043
1.038
R1, wR2 [I ≥ 2σ(I)]a 0.0373 0.0950
0.0352 0.0918
0.0429 0.0972
Symmetry code: (i) 1 − x, −y, 1 − z
R1, wR2 (all data)a
0.0532 0.1043
O3 atom is involved in the bridge between V1 and V1A, strongly
ꢀ
ꢀ
ꢀ
aR1
=
||Fo| − |Fc||/ |Fo|, wR2 = [ w(Fo2 − Fc2)2/
˚
coordinated to V1A [1.665(2) A] and weakly coordinated to V1
ꢀ
w(Fo2)2]1/2, w1 = [σ2 Fo2 + (0.0515(Fo2 + 2Fc2)/3)2 + 0.3832
˚
[2.415(2) A]. The coordinate bond lengths are comparable to
(Fo2 + 2Fc2)/3]−1, w2 = [σ2 Fo2 + (0.0512(Fo2 + 2Fc2)/3)2
+
those observed in other similar vanadium complexes.[14−16] The
distortion of the octahedral coordination can be observed by the
coordinate bond angles, ranging from 74.2(1) to 106.9(1)◦ for
0.4249(Fo2 + 2Fc2)/3]−1
.
and 846 cm−1 for (1), and 928 and 827 cm−1 for (2), which may the perpendicular angles, and from 151.0(1) to 171.2(1)◦ for
be assigned to the asymmetric and symmetric ν(O V O) vi- the diagonal angles. There form two intramolecular N−H· · ·O
bration of the VO2groups. The spectra show moreover ν(C N) hydrogen bonds in the molecule of the complex.
vibrations at 1634 cm−1 for (1) and 1628 cm−1 for (2), and one
sharp ν(N-H) vibration at 3221 cm−1 for (1).
In the solid UV-Vis spectra, the complexes (1) and (2) show
bands at 392 nm and 404 nm, respectively, which were attributed
to the intramolecular charge transfer transitions from the pπ
orbital on the phenolate oxygen to the empty d orbitals of the
metal atom.[13]
Structure Description of the Complex (1)
The molecular structure of the complex (1) is shown in
Figure 1. The compound is a centrosymmetric dinuclear dioxo-
vanadium complex, with the inversion center at the midpoint of
˚
the two V atoms. The V· · ·V distance is 3.224(2) A. Each V atom
in the complex is six-coordinated through three bonds to oxo
groups and through bonds to the tridentate Schiff base ligand L1,
FIG. 1. Molecular structure of the complex (1) at 30% probability displace-
ment. Atoms labeled with the suffix A or unlabeled are at the symmetry position
1 – x, – y, 1 – z.
forming an octahedral geometry. The distance between atoms
˚
V1 and O2 is 1.606(2) A, indicating a typical V O bond. The

TWO DIOXOVANADIUM(V) COMPLEXES WITH SCHIFF BASES
25
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Structure Description of the Complex (2)
The molecular structure of the complex (2) is shown in Figure
2. The V atom is five-coordinate in a distorted square pyrami-
dal geometry. The basal plane is composed of the phenolate
O, imine N and amine N atoms of the Schiff base ligand L2,
and an oxo ligand O3. The apical position is occupied by a
˚
second oxo ligand, O4. The V atom lies 0.503(2) A from the
mean plane of the basal atoms, in the direction of the apical oxo
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Structure, Characterization and Photoreactivity of Monomeric Dioxovana-
dium(V) Schiff-Base Complexes of Trigonal-Bipyramidal Geometry. J.
Chem. Soc., Dalton Trans. 1996, 93–97.
14. Li, L.-Z.; Xu, T.; Wang, D.-Q.; Ji, H.-W. Synthesis, Crystal Structure
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Dioxovanadium(V)]. Chinese J. Inorg. Chem. 2004, 20, 236–240.
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CONCLUSIONS
In the present article, two new dioxovanadium complexes
have been synthesized and characterized by X-ray diffraction.
The Schiff bases 4-chloro-2-[(2-isopropylaminoethylimino)-
methyl]phenol and 4-chloro-2-[(2-morpholin-4-ylethylimino)-
methyl]phenol coordinate to the V atoms through the phenolate
O, imine N and amine N atoms. Considering the only difference
between the two Schiff bases is the size of the terminal groups,
so it is easily to conclude that the steric effects of the terminal
groups in the Schiff base ligands can influence the structures of
the vanadium complexes.
SUPPLEMENTARY MATERIALS
Supplementary crystallographic data are available from
the CCDC, Union Road, Cambridge CB2 1EZ, UK on re-
quest quoting the deposition numbers CCDC 779895 for (1)
and 779896 for (2) (fax: +44 1223 336 033; e-mail: de-
posit@ccdc.cam.ac.uk).
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