Synthesis and crystal structures of two dinuclear Schiff base cadmium(II) complexes

Article abstract of DOI:10.1080/15533174.2011.613435

Two new dinuclear Schiff base cadmium(II) complexes with the formulae [Cd₂(DM)₂(NCS)₂] (1) and [Cd ₂(MP)₂(NO₃)₂] (2) (DM is 2-[(3-dimethylaminopropylimino)methyl]-6-methoxyphenol

Full text of DOI:10.1080/15533174.2011.613435

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Synthesis and Reactivity in Inorganic, Metal-Organic,
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Synthesis and Crystal Structures of Two Dinuclear
Schiff Base Cadmium(II) Complexes
a
a
Chun-Hua Dai & Fu-Lin Mao
a
Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental
Protection Department of Chemistry , Yancheng Teachers University , Yancheng , P. R. China
Accepted author version posted online: 14 Mar 2012.Published online: 01 May 2012.
To cite this article: Chun-Hua Dai & Fu-Lin Mao (2012) Synthesis and Crystal Structures of Two Dinuclear Schiff Base
Cadmium(II) Complexes, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:4, 537-541, DOI:
10.1080/15533174.2011.613435
To link to this article: http://dx.doi.org/10.1080/15533174.2011.613435
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:537–541, 2012
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.613435
Synthesis and Crystal Structures of Two Dinuclear Schiff
Base Cadmium(II) Complexes
Chun-Hua Dai and Fu-Lin Mao
Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection,
Department of Chemistry, Yancheng Teachers University, Yancheng, P. R. China
[Cd2(DM)2(NCS)2] (1) and [Cd2(MP)2(NO3)2] (2), were pre-
Two new dinuclear Schiff base cadmium(II) complexes with the pared and characterized.
formulae [Cd (DM) (NCS) ] (1) and [Cd (MP) (NO ) ] (2) (DM
2 2 2 2 2 3 2
is 2-[(3-dimethylaminopropylimino)methyl]-6-methoxyphenolate,
MP is 2-methoxy-6-[(2-morpholin-4-ylethylimino)methyl]pheno- EXPERIMENTAL
late), were prepared and characterized by physicochemical meth-
ods and single crystal X-ray determination. Complex (1) crystal- Materials and Methods
lizes in orthorhombic system space group Pca2
1
, with a = 16.185(2)
3
-Methoxysalicylaldehyde, N,N-dimethylpropane-1,3-dia-
◦
Å, b = 11.506(2) Å, c = 35.989(3) Å, V = 6702.0(15) , Z = 8,
mine, and 4-(2-aminoethyl)morpholine with AR grade were
available from Alfa Aesar Company (Massachusetts, USA).
The cadmium nitrate and other chemicals with AR grade were
purchased from Beijing Chemical Reagent Company (Beijing,
2
R
(
1
gt(F) = 0.0372, wRref(F ) = 0.0713, and T = 298(2) K. Complex
2) crystallizes in monoclinic system space group P2/c, with a =
◦
8.759(2) Å, b = 8.379(1) Å, c = 22.771(2) Å, β = 113.794(3) , V
◦
2
=
3275.0(6) , Z = 4, Rgt(F) = 0.0739, wRref(F ) = 0.1944, and T =
2
98(2) K. Single-crystal X-ray diffraction analysis reveals that both P. R. China) and were used without further purification. Car-
complexes are structurally similar phenolate O-bridged dinuclear
cadmium compounds. The Cd atoms in (1) are six-coordinated in
octahedral geometry, while those in (2) are seven-coordinated in
distorted pentagonal bipyramidal geometry.
bon, hydrogen and nitrogen were determined on a Perkin-
Elmer 240C microanalyzer (Waltham, MA, USA). IR spectra
−1
(4000–400 cm ), as KBr pellets, were recorded on a Nicolet
(
Yancheng Teachers University) FT-IR 170X spectrophotome-
1
ter. The HNMR spectra of the Schiff bases were recorded on
Bruker AVANCE 400 MHz spectrometer (Madison, WI, USA)
with tetramethylsilane as the internal reference.
Keywords cadmium complex, crystal structure, Schiff base,
synthesis
Synthesis of HDM
INTRODUCTION
A mixture of 3-methoxysalicylaldehyde (1.52 g, 10 mmol)
and N,N-dimethylpropane-1,3-diamine (1.02 g, 10 mmol) in
methanol (100 mL) was refluxed for 30 min. Then three-quarters
of the methanol was evaporated, and the solution was cooled to
room temperature. Yellow deposits were collected by filtration
and recrystallized from methanol. Yield: 93%. Anal. Calcd. for
C13H20N2O2 (%): C, 66.1; H, 8.5; N, 11.8. Found (%): C, 66.3;
In the last few decades, considerable attention has been fo-
cused on Schiff bases and their complexes in the fields of coordi-
nation chemistry and biological chemistry.[
1–3]
A great number
of copper, cobalt, nickel, zinc, and manganese complexes with
[
4–8]
Schiff bases have been reported,
however, the cadmium(II)
complexes with Schiff bases are very rare. In the present
work, two new dinuclear cadmium(II) complexes derived from
the Schiff bases 2-[(3-dimethylaminopropylimino)methyl]-
-methoxyphenolate (DM) and 2-methoxy-6-[(2-morpholin-
-ylethylimino)methyl]phenolate (MP), with the formulae
−1
H, 8.6; N, 11.7. Characteristic IR (cm ): 3323 (w, νOH), 1637
1
(
6
8
s, νC = N). H NMR (CDCl3): δ (ppm) 1.72 (m, 2H), 2.26 (s,
6
4
H), 2.37 (t, 2H), 3.53 (t, 2H), 3.71 (s, 3H), 6.54–7.03 (m, 3H),
.12 (s, 1H), 10.23 (s, 1H).
Synthesis of HMP
Received 2 January 2011; accepted 8 August 2011.
The authors acknowledge the Yancheng Teachers University for a
financial support.
Address correspondence to Fu-Lin Mao, Jiangsu Provincial Key
Laboratory of Coastal Wetland Bioresources and Environmental Pro-
tection, Department of Chemistry, Yancheng Teachers University,
Yancheng 224002, P. R. China. E-mail: xpzhougroup@163.com
A mixture of 3-methoxysalicylaldehyde (1.52 g, 10 mmol)
and 4-(2-aminoethyl)morpholine (1.30 g, 10 mmol) in methanol
(100 mL) was refluxed for 30 min. Then three-quarters of the
methanol was evaporated, and the solution was cooled to room
temperature. Yellow deposits were collected by filtration and
recrystallized from methanol. Yield: 95%. Anal. Calcd. for
537

538
C.-H. DAI AND F.-L. MAO
C14H20N2O3 (%): C, 63.6; H, 7.6; N, 10.6. Found (%): C, 63.4;
TABLE 1
−1
H, 7.6; N, 10.7. Characteristic IR (cm ): 3337 (w, νOH), 1645
Crystal data and refinement parameters for the complexes
1
(
2
1
s, νC = N). H NMR (CDCl3): δ (ppm) 2.34 (t, 4H), 2.71 (t,
(
1)
(2)
H), 3.64 (m 6H), 3.71 (s, 3H), 6.60–7.03 (m, 3H), 8.12 (s, 1H),
0.17 (s, 1H).
Chemical formula
Fw
T (K)
C28H38Cd2N6O4S2 C28H38Cd2N6O12
811.6
298(2)
875.4
298(2)
Synthesis of [Cd2(DM)2(NCS)2] (1)
To a methanolic solution (20 ml) of HDM (0.24 g, 1 mmol)
and ammonium thiocyanate (0.08 g, 1 mmol) was added with
stirring a methanolic solution (10 mL) of cadmium nitrate (0.31
g, 1 mmol). The mixture was then stirred at room temperature for
Crystal shape/color
block/yellow
0.32 × 0.30
block/yellow
0.32 × 0.30
× 0.30
3
Crystal size (mm )
×
0.30
Orthorhombic
Pca21
Crystal system
Space group
a (Å)
Monoclinic
P2/c
2
h. The insoluble impurities were removed by filtration. Block
yellow crystals, suitable for single crystal X-ray diffraction,
were formed by slow evaporation of the filtrate in air for a
few days. Yield: 63%. Anal. Calcd. for C28H38Cd2N6O4S2 (%):
C, 41.4; H, 4.7; N, 10.4. Found (%): C, 41.1; H, 4.9; N, 10.6.
16.185(2)
11.506(2)
35.989(3)
90
90
90
6702.0(15)
8
1.609
1.434
3264
–17/20–
18.759(2)
8.379(1)
22.771(2)
90
113.794(3)
90
3275.0(6)
4
1.775
1.369
1760
–22/23–
10/10–27/29
7091
b (Å)
c (Å)
◦
α ( )
−1
Selected IR (cm ): 2058 (s), 1625 (s), 1455 (s), 1406 (m), 1297
m), 1241 (m), 1214 (s), 1076 (w), 1046 (m), 846 (w), 739 (m),
24 (w), 470 (w), 433 (w).
◦
β ( )
(
6
◦
γ ( )
V (Å )
3
Z
Synthesis of [Cd2(MP)2(NO3)2] (2)
3
Dc (g/cm )
Complex (2) was prepared by the similar method as that
described for (1), with HDM replaced by HMP (2.64 g, 1 mmol).
Yield: 71%. Anal. Calcd. C28H38Cd2N6O12 (%): C, 38.4; H, 4.4;
−1
µ (MoKα) (cm )
F(000)
−1
Index ranges (h, k, l)
N, 9.6. Found (%): C, 38.6; H, 4.5; N, 9.5. Selected IR (cm ):
635 (s), 1448 (s), 1385 (m), 1294 (s), 1219 (m), 1117 (m), 1100
m), 1076 (m), 927 (w), 736 (m), 640 (w), 474(w), 433 (w).
14/14–31/45
1
(
Independent
reflections
11425
X-Ray Crystallography
The single crystals of complexes (1) and (2) suitable for
X-ray diffraction were each mounted on a thin-walled glass T(min)/T(max)
Observed reflections
[I ≥ 2σ(I)]
8972
6419
0.6568/0.6728
11425/1/769
0.6684/0.6841
7091/0/435
capillary and aligned on the Bruker SMART 1000 CCD area Data/restraints/
diffractometer, equipped with graphite-monochromated Mo Kα
parameters
2
radiation (λ = 0.71073 Å). The θ range for data collection is Goodness of fit on F
1.029
1.189
0.0739, 0.1944
0.0787, 0.1964
0.000
◦
◦
a
2
.10–27.00 for (1) and 1.83–27.00 for (2). All data were cor- R1, wR2 [I ≥ 2σ(I)]
0.0372, 0.0713
0.0548, 0.0792
0.000
a
rected for Lorentz and polarization effects and for the effects of R1, wR2 (all data)
absorption. Both structures were solved by the direct method and (ꢀ/σ)max
refined by least-square cycles. The non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were included but not
ꢀ
ꢀ
= [ꢀ
ꢀ
aR
2
2 2
2 2 1/2
1
=
||Fo|-|Fc||/ |Fo|, wR
2
w(Fo -Fc ) / w(Fo ) ]
refined. All calculations were performed using the SHELXTL-
7 package.[ The data collection and refinement parameters
9]
by the steric effects of the terminal groups of the Schiff base
ligands.
9
are summarized in Table 1. Selected bond lengths and angles
are given in Table 2.
Structure Description of (1)
The asymmetric unit of the complex (1) consists of two phe-
nolate O-bridged dinuclear cadmium(II) complex molecules,
RESULTS AND DISCUSSION
The Schiff bases were synthesized by the condensa- as shown by Figure 1. Each Cd atom in the complex is in a
tion of equimolar quantities of 3-methoxysalicylaldehyde distorted octahedral coordination. The Cd1 and Cd3 atoms are
with N,N-dimethylpropane-1,3-diamine for (1), and 3- coordinated by two phenolate O atoms, two imine N atoms
methoxysalicylaldehyde with 4-(2-aminoethyl)morpholine for and two amine N atoms from two DM ligands. The Cd2 and
(
2), respectively, in methanol. The reaction of the Schiff bases Cd4 atoms are coordinated by two phenolate O atoms and two
with cadmium nitrate and ammonium thiocyanate leads to the ether O atoms from two DM ligands, and by two N atoms from
formation of the two cadmium complexes. It is interesting that two terminal thiocyanate ligands. The distortion of the octahe-
the thiocyanate ligands coordinated to the cadmium atoms in dral coordination can be observed from the bond angles. The
(
1), but not coordinated to those in (2), which might be caused coordinate bond lengths in both molecules are similar to each

TWO SCHIFF BASE CADMIUM(II) COMPLEXES
539
TABLE 2
TABLE 2
◦
◦
Selected bond lengths (Å) and bond angles ( ) for the
complexes
Selected bond lengths (Å) and bond angles ( ) for the
complexes (Continued)
(
1)
Cd1-O1
Cd1-N1
Cd1-N3
Cd2-O1
Cd2-O3
Cd2-N9
Cd3-O5
Cd3-N5
Cd3-N7
Cd4-O5
Cd4-O6
Cd4-N11
O1-Cd1-O3
O3-Cd1-N3
O3-Cd1-N1
O1-Cd1-N2
N3-Cd1-N2
O1-Cd1-N4
N3-Cd1-N4
N2-Cd1-N4
N10-Cd2-O1
N10-Cd2-O3
O1-Cd2-O3
N9-Cd2-O2
O3-Cd2-O2
N9-Cd2-O4
O3-Cd2-O4
O5-Cd3-O7
O7-Cd3-N7
O7-Cd3-N5
O5-Cd3-N8
N7-Cd3-N8
O5-Cd3-N6
N7-Cd3-N6
N8-Cd3-N6
N11-Cd4-O5
N11-Cd4-O7
O5-Cd4-O7
N12-Cd4-O6
O7-Cd4-O6
N12-Cd4-O8
O7-Cd4-O8
O2A-Cd1-N1
N1-Cd1-O2
N1-Cd1-O4
O2A-Cd1-N2
O2-Cd1-N2
O2A-Cd1-O5
O2-Cd1-O5
136.7 (3)
74.1 (3)
87.3 (3)
103.4 (3)
127.8 (3)
112.5 (3)
85.7 (3)
136.8 (3)
72.5 (3)
88.3 (4)
105.3 (3)
114.2 (3)
85.5 (3)
O2A-Cd1-O2
O2A-Cd1-O4
O2-Cd1-O4
N1-Cd1-N2
O4-Cd1-N2
N1-Cd1-O5
O4-Cd1-O5
O8-Cd2-N4A
O8-Cd2-O11
74.7 (3)
2.246 (4)
2.292 (5)
2.276 (5)
2.238 (4)
2.269 (4)
2.181 (8)
2.247 (4)
2.301 (6)
2.295 (5)
2.240 (4)
2.446 (5)
2.184 (8)
74.8 (2)
80.2 (2)
152.2 (2)
101.9 (2)
94.4 (2)
91.9 (2)
78.2 (2)
162.2 (2)
117.2 (3)
104.1 (3)
75.0 (2)
87.8 (2)
140.9 (2)
79.0 (3)
65.6 (2)
74.4 (2)
152.1 (2)
79.8 (2)
103.3 (2)
78.6 (2)
91.1 (2)
91.9 (2)
161.2 (2)
115.8 (2)
102.0 (2)
75.1 (2)
86.7 (2)
141.2 (2)
79.5 (2)
65.7 (2)
Cd1-O3
Cd1-N2
Cd1-N4
Cd2-O2
Cd2-O4
Cd2-N10
Cd3-O7
Cd3-N6
Cd3-N8
2.275 (4)
2.447 (5)
2.473 (5)
2.447 (5)
2.543 (5)
2.163 (8)
2.290 (4)
2.459 (5)
2.427 (6)
2.263 (4)
2.521 (5)
2.209 (8)
150.6 (2)
81.1 (2)
126.4 (2)
92.7 (2)
78.7 (2)
101.7 (2)
92.6 (2)
124.3 (3)
110.0 (2)
115.6 (2)
84.4 (3)
135.9 (3)
133.0 (3)
74.0 (3)
85.0 (3)
94.3 (3)
52.5 (3)
134.9 (3)
136.7 (3)
N2-Cd1-O5
O8-Cd2-O8A
N4A-Cd2-O11
O8-Cd2-N5A
O8-Cd2-O10
O8A-Cd2-O10
O8A-Cd2-O11 134.1 (3)
Cd4-O7
Cd4-O8
Cd4-N12
O11A-Cd2-N5
N4A-Cd2-O10
O11-Cd2-O10
83.1 (3)
92.8 (4)
52.5 (3)
O1-Cd1-N3
O1-Cd1-N1
N3-Cd1-N1
O3-Cd1-N2
N1-Cd1-N2
O3-Cd1-N4
N1-Cd1-N4
N10-Cd2-N9
N9-Cd2-O1
N9-Cd2-O3
N10-Cd2-O2
O1-Cd2-O2
N10-Cd2-O4
O1-Cd2-O4
O2-Cd2-O4
O5-Cd3-N7
O5-Cd3-N5
N7-Cd3-N5
O7-Cd3-N8
N5-Cd3-N8
O7-Cd3-N6
N5-Cd3-N6
N11-Cd4-N12
N12-Cd4-O5
N12-Cd4-O7
N11-Cd4-O6
O5-Cd4-O6
N11-Cd4-O8
O5-Cd4-O8
O6-Cd4-O8
N5A-Cd2-O10 134.3 (3)
Symmetry code for A: – x, y, 1/2 – z.
other, and also comparable with those observed in other Schiff
base cadmium(II) complexes.[
10–13]
As expected, the bond in-
volving amine N atoms are longer than those involving imine N
atoms.[ The Cd· · ·Cd distances in both molecules are 3.583(2)
and 3.590(2) Å, respectively, which precludes any significant
metal–metal interactions.
14]
Structure Description of (2)
67.4 (2)
84.0 (3)
The asymmetric unit of the complex (2) consists of two phe-
nolate O-bridged dinuclear cadmium(II) complex molecules,
as shown in Figure 2. Both molecules possess crystallographic
twofold rotation symmetry. Each Cd atom in the complex is
seven-coordinated in a distorted pentagonal bipyramidal geom-
etry, with two phenolate O, one ether O, one imine N, and one
morpholine N atoms from two MP ligands, and with two nitrate
O atoms. The distortion of the pentagonal bipyramidal coordi-
nation can be observed from the bond angles. The coordinate
bond lengths in both molecules are similar to each other, and
139.1 (2)
153.2 (2)
81.4 (2)
149.5 (2)
127.0 (2)
93.3 (2)
94.1 (2)
102.2 (2)
78.5 (2)
126.0 (3)
109.8 (2)
116.6 (2)
85.2 (2)
67.7 (2)
84.3 (2)
also comparable with those observed in (1) and other Schiff base
cadmium(II) complexes.[
10–13]
As expected, the bond involving
morpholine N atoms are longer than those involving imine N
atoms.[ The Cd· · ·Cd distances in both molecules are 3.595(2)
and 3.627(2) Å, respectively, which are similar to those of (1),
and are also precludes any significant metal–metal interactions.
14]
139.1 (2)
152.9 (2)
IR Spectra
(
2)
−1
−1
The weak absorptions at 3323 cm for HDM and 3337 cm
for HMP are attributed to the stretching vibration of ν(OH) in the
free Schiff bases, and are absent in the complexes. The strong
Cd1-O2A
Cd1-O2
Cd1-N2
Cd2-O8
Cd2-O8A
Cd2-N5A
2.171 (6)
2.353 (7)
2.425 (9)
2.186 (7)
2.321 (7)
2.436 (10)
Cd1-N1
Cd1-O4
Cd1-O5
Cd2-N4A
Cd2-O11
Cd2-O10
2.309 (9)
2.417 (9)
2.457 (9)
2.316 (10)
2.392 (10)
2.464 (10)
−1
−1
absorption bands at 1637 cm for HDM and 1645 cm for
HMP are assigned to the azomethine groups, ν(C = N). The
bands are shifted to lower wave numbers in the complexes, viz.
−1 −1
625 cm for (1) and 1635 cm for (2), due to the coordination
1

540
C.-H. DAI AND F.-L. MAO
FIG. 1. (A) One molecular structure of (1) with 30% probability thermal FIG. 2. (A) One molecular structure of (2) with 30% probability thermal
ellipsoids. H atoms are omitted for clarity. (B) The other molecular struc-
ture of (1) with 30% probability thermal ellipsoids. H atoms are omitted for
clarity.
ellipsoids. H atoms are omitted for clarity. Atoms labeled with the suffix A or
unlabelled are at the symmetry positions –x, y, 1/2 – z. (B) The other molecular
structure of (2) with 30% probability thermal ellipsoids. H atoms are omitted
for clarity. Atoms labelled with the suffix A or unlabelled are at the symmetry
positions – x, y, 1/2 – z.
of the azomethine N atoms to the Cd atoms. The intense band CONCLUSION
−
1
indicative of the thiocyanate ligands in (1) is at 2058 cm .
The characteristic bands indicative of the nitrate ligands in (2) clear cadmium(II) complexes with the Schiff bases 2-[(3-
In the present study, two new structural similar dinu-
−1
are at 1448 and 1385 cm . The weak bands in the region dimethylaminopropylimino)methyl]-6-methoxyphenolate and
33–480 cm for the complexes can be assigned to ν(Cd–O) 2-methoxy-6-[(2-morpholin-4-ylethylimino)methyl]phenolate
−1
4
and ν(Cd–N).
were prepared and structurally characterized. The crystal

TWO SCHIFF BASE CADMIUM(II) COMPLEXES
541
structures of both complexes were determined. The Schiff bases
can coordinate to the Cd atoms through the phenolate O, ether
O, imine N, and amine or morpholine N atoms. Both complexes
are the rarely seen dinuclear cadmium(II) complexes derived
from Schiff bases.
tal structure and magnetic properties. Inorg. Chem. Commun. 2007, 10,
210–1213.
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salicylidene)ethanetetracarboxylic acid tetrahydrazide. Synth. React. Inorg.
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7
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SUPPLEMENTARY MATERIALS
Crystallographic data for both complexes have been de-
posited with the Cambridge Crystallographic Data Centre,
CCDC 781081 for (1) and 781082 for (2). Copies of these
information may be obtained free of charge from: the Di-
rector, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
8. Mohamed, G.G.; Omar, M.M.; Ibrahim, A. A. Biological activity studies
on metal complexes of novel tridentate Schiff base ligand. Spectroscopic
and thermal characterization. Eur. J. Med. Chem. 2009, 44, 4801–4812.
9. Sheldrick, G.M. SHELXTL-97, Program for X-Ray Crystal Structure Solu-
tion; University of G o¨ ttingen, Germany, 1997.
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