Synthesis, characterization, and crystal structure of a novel acetato-bridged trinuclear cadmium(II) complex with 4-Nitro-2-[(2- isopropylaminoethylimino)methyl]phenol

Article abstract of DOI:10.1080/15533174.2010.522647

A novel acetato-bridged centrosymmetric trinuclear Schiff base cadmium(II) complex, [Cd{CdL(μ₂ - O, O'-CH₃COO)(μ₃- O, O, O'-CH₃COO)}₂], where L is the deprotonated form of 4-nitro-2-[(2-isopropylamino

Full text of DOI:10.1080/15533174.2010.522647

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:843–846, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.522647
Synthesis, Characterization, and Crystal Structure of a
Novel Acetato-bridged Trinuclear Cadmium(II) Complex
with 4-Nitro-2-[(2-isopropylaminoethylimino)methyl]phenol
Rui-Hua Hui,1 Peng Zhou,1 and Zhong-Lu You2
1Department of Chemistry, Anshan Normal University, Anshan, P. R. China
2Department of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, P. R. China
1
carried out using a Perkin-Elmer model 240 analyzer. The H
NMR spectrum was recorded on Bruker AVANCE 500 MHz
spectrometer with tetramethylsilane as the internal reference. 5-
Nitrosalicylaldehyde and N-isopropylethane-1,2-diamine were
purchased from Lancaster Company, and other chemicals were
of analytical grade quality and used without further purification.
A novel acetato-bridged centrosymmetric trinuclear Schiff
base cadmium(II) complex, [Cd{CdL(µ2 − O,Oꢀ-CH3COO)(µ3−
O,O,Oꢀ-CH3COO)}2], where L is the deprotonated form of
4-nitro-2-[(2-isopropylaminoethylimino)methyl]phenol, has been
synthesized and characterized by elemental analysis, IR spec-
trum, and single crystal X-ray diffraction. The acetate groups
bridge adjacent Cd atoms through both µ2 − O,Oꢀ-acetato and
µ3 − O,O,Oꢀ-acetato bridging modes. The Cd atoms adopt octa-
˚
hedral coordinations. The Cd· · ·Cd distance is 3.434(2) A.
Synthesis of HL
To a methanol solution (10 ml) of 5-nitrosalicylaldehyde
(1.0 mmol, 167 mg) was added a methanol solution (10 ml)
of N-isopropylethane-1,2-diamine (1.0 mmol, 102 mg), with
continuous stirring at room temperature. The mixture was stirred
for about 10 minutes and most of the solvent was evaporated
to give yellow solid, which was filtered out and dried in air.
Yield: 233 mg (93%). M.p. 72.0–73.5◦C. Analysis: calcd. for
C12H17N3O3: C, 57.4; H, 6.8; N, 16.7%. Found: C, 57.1; H, 6.9;
N, 17.0%. Selected IR data (KBr, cm−1): 3422 (w, br), 3300 (m,
sh), 3067 (w), 2956 (m), 2894 (w), 2833 (w), 1637 (vs), 1540
(s), 1523 (s), 1439 (s), 1376 (m), 1307 (vs), 1228 (s), 1171 (m),
1132 (m), 1093 (s), 1041 (w), 892 (w), 837 (w), 736 (w), 680
(w), 629 (w), 487 (w). 1H NMR data (CDCl3, ppm): δ = 1.05
(d, 6H), 2.13 (s, 1H), 2.93 (t, 2H), 2.98 (m, 1H), 3.58 (t, 2H),
7.09 (d, 1H), 8.07 (d, 1H), 8.12 (s, 1H), 8.36 (s, 1H).
Keywords acetate, cadmium complex, crystal structure, Schiff base,
synthesis
INTRODUCTION
Schiff bases have been widely used as chelating ligands in
the field of coordination chemistry for their versatile struc-
tures and potential applications.[1−3] The acetate anions can
link two or more metal atoms through µ2-acetato-O,[4,5] µ2-
acetato-O,Oꢀ,[6,7] and µ3-acetato-O,O,Oꢀ[7,8] bridging modes
(Scheme 1), yielding various polynuclear and one-, two-
, or three-dimensional species of different topologies. In
the present work, a novel centrosymmetric trinuclear cad-
mium complex, [Cd{CdL(µ2−O,Oꢀ-CH3COO)(µ3−O,O,Oꢀ-
CH3COO)}2], where L is the deprotonated form of 4-nitro-2-
[(2-isopropylaminoethylimino)methyl]phenol (HL, Scheme 2),
has been synthesized and structural characterized.
Synthesis of [Cd{CdL(␮2 − O, Oꢀ-CH3COO)
(␮3 − O, O, Oꢀ-CH3COO)}2]
To a methanol solution (30 ml) of HL (0.5 mmol, 125 mg)
was added a methanol solution (10 ml) of Cd(CH3COO)2·2H2O
(1.0 mmol, 266 mg), with continuous stirring at room temper-
ature. The final clear solution was allowed to stand at room
temperature for several days. Colorless crystals suitable for X-
ray diffraction were collected and dried in air. Yield: 172 mg
(64% with respect to the HL). M.p. > 300◦C. Analysis: Calcd.
for C32H44Cd3N6O14: C, 35.8; H, 4.1; N, 7.8%. Found: C, 35.1;
H, 4.3; N, 8.2%. Selected IR data (KBr, cm−1): 3447 (w, br),
3213 (m, sh), 1648 (s), 1599 (s), 1402 (s), 1310 (s), 1105 (m).
EXPERIMENTAL
Materials and Instrumentation
Infrared spectra were recorded in a Bruker IFS-125 model
FT-IR spectrophotometer as KBr pellets. C, H, N analyses were
Received 17 November 2009; accepted 2 August 2010.
Address correspondence to Rui-Hua Hui, Department of Chem-
istry, Anshan Normal University, Anshan 114007, P. R. China. E-mail:
ruihua hui@126.com
843

844
R.-H. HUI ET AL.
TABLE 1
Crystallographic and experimental data for the complex
M
M
O
O
O
M
O
O
M
O
M
Formula
C32H44Cd3N6O14
M
FW
1073.9
µ2-acetato-O
µ2-acetato-O,O’
µ3-acetato-O,O,O’
Crystal shape / color
Crystal size / mm
Crystal system
Space group
Block/colorless
0.32 × 0.29 × 0.27
Triclinic
P-1
10.2169(13)
10.4570(13)
11.1057(14)
114.444(1)
105.449(2)
91.724(2)
1027.7(2)
1
SCH. 1. The bridging modes of the acetate groups.
˚
H
a/A
N
O2N
˚
b/A
N
˚
c/A
α /◦
β /◦
γ /◦
OH
SCH. 2. The Schiff base HL.
3
˚
V /A
Crystal Structure Determination
Z
A selected high quality crystal of the complex was mounted
on a glass fiber and aligned on the Bruker SMART 1000 CCD
diffractometer, equipped with graphite-monochromated Mo Kα
T /K
298(2)
0.71073
1.735
4550/254
3808
0.0172
0
534
0.6275
0.6709
µ / mm−1(Mo-Kα)
Dcalc/g cm−3
Reflections/parameters
Independent reflections
Rint
˚
radiation (λ = 0.71073 A). The θ range for data collection
is 2.09–27.50◦ for the complex. All data were corrected for
Lorentz and polarization effects and for the effects of absorp-
tion. The structure was solved by the direct method and re-
fined by least-square cycles. The non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were placed in geo-
metrically idealized positions and constrained to ride on their
Restraints
F(000)
Tmin
Tmax
Goodness of fit on F2
R1, wR2 [I ≥ 2σ(I)]a)
R1, wR2 (all data)a)
ꢀ
1.043
0.0264, 0.0702
0.0323, 0.0724
˚
parent atoms, with C−H distances in the range 0.93−0.97 A,
˚
N−H distances of 0.91 A, and with Uiso(H) set at 1.2Ueq(C, N)
and 1.5Ueq(methyl C). All calculations were performed using
the SHELXTL-97 package.[9] The data collection and refine-
ment parameters are summarized in Table 1. Selected bond
lengths and angles are given in Table 2.
ꢀ
ꢀ
R1
=
||Fo| – |Fc|| /
|Fo|, wR2 = [ w(Fo2– Fc2)2/
ꢀ
w(Fo2)2]1/2
different bridging modes, viz. µ2-acetato-O,Oꢀ and µ3-acetato-
O,O,Oꢀ.
RESULTS AND DISCUSSION
Synthesis
The Cd1 atom is six-coordinated by two oxygen bridges, O1
and O1A, from two Schiff base ligands, and by four O atoms
from four acetate bridges, forming an octahedral geometry. The
coordination around the central metal atom displays only slight
distortion. The bond distances are relatively similar and range
The Schiff base HL was readily synthesized by the conden-
sation of equimolar quantities of 5-nitrosalicylaldehyde with
N-isopropylethane-1,2-diamine in methanol, with high yield
and purity. The cadmium complex was synthesized by reaction
of HL with cadmium acetate in methanol (Scheme 3).
To our knowledge, only one copper(II) complex[10] and one
zinc(II) complex[11] with the Schiff base ligand L were reported.
Both complexes are mononuclear. We have tried to use the CdCl2
and Cd(NO3)2 as the starting material in the preparation of the
complex; however, it is difficult to obtain the single crystals.
˚
from 2.212(2) to 2.320(2) A. The greatest deviation of the bond
angles from those expected for an ideal octahedral geometry
is found for O1-Cd1-O6 with 79.0(1)◦, which is caused by the
strain created by the four-membered chelate ring Cd1-O1-Cd2-
O6.
The coordination around the inversion-related terminal Cd2
atoms is also octahedral for the complex, but with severe dis-
tortion. The octahedron of each terminal Cd2 atom is formed
X-ray Crystal Structure of the Complex
The molecular structure of the complex is shown in Figure 1. by one phenolate O, one imine N and one amine N atoms of L,
The complex is an acetato-bridged centrosymmetric trinuclear and by three O atoms from two acetate ligands. The distortion
cadmium(II) complex, with the Cd1 atom lying on the inversion of the octahedral geometry is mainly caused by the strain cre-
center. It is very interesting that the acetate ligands adopt two ated by the four-membered chelate rings Cd1-O1-Cd2-O6 and

ACETATO-BRIDGED TRINUCLEAR CADMIUM(II) COMPLEX
845
TABLE 2
◦
˚
Selected bond lengths (A) and angles ( ) for the complex
Bond lengths
Cd1-O1
Cd1-O6
Cd2-N1
Cd2-O4
Cd2-O7
2.320(2)
2.299(2)
2.263(2)
2.231(2)
2.497(2)
Cd1-O5
Cd2-O1
Cd2-N2
Cd2-O6
2.212(2)
2.321(2)
2.323(2)
2.297(2)
Bond angles
O5-Cd1-O5A
O5-Cd1-O6A
O5-Cd1-O1A
O5-Cd1-O1
O1-Cd1-O1A
O4-Cd2-O6
O4-Cd2-O1
O6-Cd2-O1
N1-Cd2-N2
O1-Cd2-N2
N1-Cd2-O7
O1-Cd2-O7
180
O5-Cd1-O6
O6-Cd1-O6A
O6-Cd1-O1A
O6-Cd1-O1
O4-Cd2-N1
N1-Cd2-O6
N1-Cd2-O1
O4-Cd2-N2
O6-Cd2-N2
O4-Cd2-O7
O6-Cd2-O7
N2-Cd2-O7
87.0(1)
180
93.0(1)
91.5(1)
88.5(1)
180
90.4(1)
93.4(1)
79.0(1)
76.6(1)
155.2(1)
107.1(1)
98.8(1)
101.0(1)
78.9(1)
114.4(1)
147.5(1)
78.9(1)
92.9(1)
125.0(1)
138.3(1)
53.8(1)
92.4(1)
FIG. 1. Molecular structure of the complex with 30% probability displace-
ment. H atoms are omitted for clarity.
[(2-isopropylaminoethylimino)methyl]phenol was synthesized
and characterized. The crystal structure of the complex was
investigated. The Schiff base coordinates to the Cd atom through
the phenolate O, imine N and amine N atoms. The acetate anions
adopt two different bridging modes, viz. µ2-acetato-O,Oꢀ and
µ3-acetato-O,O,Oꢀ.
Cd2-O6-C16-O7, and the five-membered chelate ring Cd2-N1-
C8-C9-N2.
The coordinate bond lengths in the complex are comparable
to the similar Schiff base cadmium(II) complexes.[12−14] The
˚
Cd· · ·Cd distance is 3.434(2) A, which precludes any significant
metal-metal interaction.
In the crystal structure of the complex, molecules are linked
through intermolecular N−H· · ·O hydrogen bonds, forming
chains running along the c axis, as shown in Figure 2.
SUPPLEMENTARY MATERIAL
Crystallographic data for the complex has been deposited
with the Cambridge Crystallographic Data Centre, CCDC ref-
erence number 638094. Copies of these information may be
obtained free of charge from: the Director, CCDC, 12 Union
Road, Cambridge, CB2 1EZ, UK (fax: +44-1223-336033; E-
mail: deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
SUMMARY
In the above study, a novel acetato-bridged centrosymmetric
trinuclear cadmium(II) complex with the Schiff base 4-nitro-2-
O2N
O
N
H
O2N
N
MeOH
O
N
O
Cd(CH3COO)2
+
O
N
O
Cd
N
Cd
N
OH
O
Cd
O
O
O
O
NO2
SCH. 3. Synthesis of the complex.

846
R.-H. HUI ET AL.
FIG. 2. Molecular packing of the complex, viewed along the b axis. Hydrogen bonds are shown as dashed lines.
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