Three naphthalenedisulfonate polymers with imidazole-containing ligands: Synthesis, structure and heterogeneously catalytic performance in reactions of enamination of β-dicarbonyl compounds

Article abstract of DOI:10.1016/j.ica.2015.03.014

Three new naphthalenedisulfonate polymers, [Cd(2,6-nds)(bib)]_n (1), [Cd(1,5-nds)(bib)]_n (2), and [Cu(2,6-nds)_0.5(tpim)]_n (3), have been successfully synthesized by hydrothermal reactions of corresponding metal salts with naphthalenedisulfonate (nds) and imidazole-containing ligands 1,4-bis(imidazol-1-ylmethyl)benzene (bib) and 2,4,5-tri(4-pyridyl)-imidazole (tpim). The structures of these polymers were determined by single crystal X-ray diffraction analysis. Polymers 1 and 2 crystallize in the same space group and have similar cell parameters, and thus show same three-dimensional (3D) framework architecture. Complex 3 has the same 2D layer structure. The photoluminescent properties of the complexes 1 and 2 were investigated. Catalytic tests indicate that complex 3 has chemo-and regio-selective catalytic activity towards enamination of β-ketoesters.

Full text of DOI:10.1016/j.ica.2015.03.014

Inorganica Chimica Acta 430 (2015) 253–260
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Inorganica Chimica Acta
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Three naphthalenedisulfonate polymers with imidazole-containing
ligands: Synthesis, structure and heterogeneously catalytic performance
in reactions of enamination of b-dicarbonyl compounds
Li Wang , Jing Liu , Hui Guo , Dongsheng Deng b, , Tian Yao , Xingwei Wang , Xinyi Wang ,
a
a
b,
⇑
⇑
a
c
c
b
Hongli Wu
a
Key Laboratory of Pesticide & Chemical Biology, Ministry of Education and School of Chemistry, Central China Normal University, Wuhan 430079, PR China
College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022, PR China
Institute of Resources & Environment, Henan Polytechnic University, Jiaozuo 454150, PR China
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 July 2014
Received in revised form 20 January 2015
Accepted 7 March 2015
Available online 24 March 2015
Three new naphthalenedisulfonate polymers, [Cd(2,6-nds)(bib)] (1), [Cd(1,5-nds)(bib)] (2), and [Cu(2,6-
nds)0.5(tpim)] (3), have been successfully synthesized by hydrothermal reactions of corresponding metal
n
n
n
salts with naphthalenedisulfonate (nds) and imidazole-containing ligands 1,4-bis(imidazol-1-yl-
methyl)benzene (bib) and 2,4,5-tri(4-pyridyl)-imidazole (tpim). The structures of these polymers were
determined by single crystal X-ray diffraction analysis. Polymers 1 and 2 crystallize in the same space
group and have similar cell parameters, and thus show same three-dimensional (3D) framework archi-
tecture. Complex 3 has the same 2D layer structure. The photoluminescent properties of the complexes
Keywords:
Organosulfonate
Crystal structure
Enamination
1
and 2 were investigated. Catalytic tests indicate that complex 3 has chemo- and regio-selective catalytic
activity towards enamination of b-ketoesters.
Ó 2015 Elsevier B.V. All rights reserved.
b-ketoesters
Heterogeneous catalysis
1
. Introduction
and sensitive to the chemical environment [9–11]. As a conse-
quence of this, organosulfonates are not only good candidates to
provide unique opportunities for the combination of the auxiliary
ligands in the construction diverse coordination architectures as
multiple H-bonding acceptors by the three oxygen atoms, but also
for their functional properties demonstrated by the related com-
plexes [12–15]. For example, Monge’s groups have reported a ser-
ies of thermally stable arenedisufonate lanthanide coordination
The design and synthesis of metal–organic hybrid materials
(
MOHMs) have attracted much attention not only because of their
intriguing structural architectures but also owing to their promis-
ing applications in adsorption, guest exchange, magnetism, and
heterogeneous catalysis [1–3]. These MOHMs are normally synthe-
sized by mixing metal salts with organic ligands under solvother-
mal or hydrothermal conditions. The final architecture depends
on several factors such as shape and functionalities of the ligands
as well as coordination number and geometry of the metal cation.
For the organic ligands, the past decade has witnessed the rapid
development of various organocarboxylate acid ligands to which
great efforts have been devoted due to these ligands having strong
coordination capacity and versatile coordination modes [4–7]. In
contrast to the flourishing studies of organocarboxylate, the coor-
dination chemistry of organosulfonate remains relatively rare,
probably due to their weak coordinating ability, although they
2
polymers with CdI -like layer structure and bifunctional catalysis
properties [15]. Most importantly, Cai et al. have evidenced that
the use of auxiliary ligands such as various amines can alter the
À
chemical environment of metal ions, and allow the SO
3
group com-
pete with water molecules and coordinate to metal ions [16,17]. It
is noted that arenedisulfonates have rigid spacers and potential
multiple binding sites, which exhibit various coordination modes
ranging from
1 6 .
l to l [18–20] So far, many transition metal
complexes with arenedisulfonates, with or without the help of
co-ligands have been reported [16–22]. Thus, the efforts of many
groups have produced a plethora of organosulfonate structural
motifs.
have similar structures [8]. In fact, it is noted that the weak coor-
dination nature of SO
À
3
makes its coordination mode very flexible
On the other hand, enamination of b-dicarbonyl compounds,
which provides important synthetic protocols to build significant
subunits in some biologically natural products such as therapeutic
agents and antitumour agents, has recently been attracted
⇑
Corresponding authors. Tel./fax: +86 379 65523821.
E-mail address: dengdongsheng168@sina.com (D. Deng).
http://dx.doi.org/10.1016/j.ica.2015.03.014
020-1693/Ó 2015 Elsevier B.V. All rights reserved.
0

2
54
L. Wang et al. / Inorganica Chimica Acta 430 (2015) 253–260
particular attention [23,24]. In this regard, our groups have
recently demonstrated that a copper-based metal–organic frame-
work can be used as a promising heterogeneous catalyst for
chemo- and regio-selective enamination of b-ketoesters [25]. The
interesting result motivated us to further investigate other hetero-
geneous catalysts for promoting efficiently some organic trans-
formation reactions. In continuation with our ongoing studies on
the development of new catalytic system, herein we report our
studies on an efficient protocol applicable to enamination of
b-dicarbonyl compounds with complex 3 as new heterogeneous
catalyst. Further, the syntheses and crystal structures of three
Table 1
Crystallographic data and structure refinement summary for polymers 1–3.
Complexes
1
2
3
Chemical formula
Formula weight
Crystal system
Space group
a (Å)
C
24
H
20CdN
4
O
S
6 2
C
24
H20CdN
4
O
S
6 2
C
46 2 10 6 2
H32Cu N O S
636.96
Triclinic
P1ꢀ
636.96
Triclinic
P1ꢀ
5.4578(7)
1012.02
Triclinic
P1ꢀ
5.2955(14)
9.241(2)
12.267(3)
89.724(3)
83.419(3)
87.219(3)
595.6(3)
1
1.776
1.143
296(2)
4307
8.5300(17)
10.561(2)
13.458(3)
101.07(3)
103.83(3)
112.72(3)
1029.7(4)
1
1.632
1.201
293(2)
8535
b (Å)
c (Å)
9.6089(13)
11.2103(15)
85.756(10)
88.132(10)
80.950(10)
578.87(13)
1
1.827
1.176
293(2)
4406
a
(°)
b (°)
(°)
c
n n
polymers, namely, [Cd(2,6-nds)(bib)] (1), [Cd(1,5-nds)(bib)] (2),
3
V (Å )
and [Cu(2,6-nds)0.5(tpim)] (3) will be presented.
n
Z
D
À3
calc (g cm
)
À1
l
(mm
)
2
. Experimental section
.1. Materials and physical techniques
All reagents and solvents were obtained from commercial
T (K)
Reflections
collected
2
Unique reflections 2183
2153
0.0131
1.035
3823
0.0285
1.040
R
int
0.0218
1.053
Goodness-of-fit
GOF)
R1(I > 2
wR (I > 2
sources and used without further purification. Elemental analyses
of C, H and N were carried out on a Flash 2000 elemental analyzer.
(
r)
0.0440
0.1172
0.0186
0.0456
0.0438
0.1367
Infrared spectra (IR) were recorded as KBr pellets on
a
2
r)
À1
Nicolet-6700 spectrometer in the 4000–400 cm
region.
Thermogravimetric analyses (TGA) were performed by heating
the crystalline sample from 25 to 800 °C at a rate of 2 °C/min in a
performed. The structures were solved with direct methods and
refined with full-matrix least-squares techniques on F2 using the
N
2
atmosphere on a SDTQ600 differential thermal analyzer.
Powder X-ray diffraction (PXRD) data were recorded on a Bruker
D8-ADVANCE X-ray diffractometer with Cu K (k = 1.5418 Å).
SHELXTL program package [26,27]. All non-hydrogen atoms were
refined anisotropically. The hydrogen atoms were set in calculated
positions and refined as riding atoms with a common isotropic
thermal parameter. The 2,6-nds molecules (N3, C16, C17, O9,
O10) in 2 are disordered and the occupation of these disordered
atoms is 50%, respectively. The crystallographic data for 1–3 are
listed in Table 1.
a
Luminescent spectra were recorded with a Rigaku RIX 2000 fluo-
rescence spectrophotometer.
2.2. Synthesis of the polymers
All three polymers were synthesized by the same method
(
Scheme S1, Supporting Information), as follows: a mixture of
M(CH COO) (M = Cd(1), Cd(2), and Cu(3), 0.1 mmol), naph-
thalenedisulfonate ligand (0.1 mmol), imidazole ligand (0.1 mmol)
and H O (10 mL) was adjusted to the special pH values with HNO
1 M) and NaOH (1 M) (the pH values of 4 for 1, and 4.5 for 2 and 3,
2.4. Typical procedure for the enamination of b-ketoesters
3
2
The enamination of b-ketoesters were carried out under sol-
vent-free conditions. In a typical enamination reaction, ketone
(0.1 mmol) was treated with amine (0.1 mmol) in the presence of
complex 3 (0.01 mmol). The reactions were monitored by the thin
layer chromatography. After the reaction finished, 10 mL of ethyl
acetate was added to the reaction mixture. The mixture was stirred
for another 5 min. Then the catalyst was filtered off, and the filtrate
was concentrated under reduced pressure. The crude product was
purified by flash column chromatography on silica gel using hex-
ane/ethyl acetate mixture (10:1) as the eluent. All isolated pure
2
3
(
respectively), stirred for 0.5 h, and then transferred and was sealed
in a 25 mL Teflon-lined stainless steel vessel and heated at 160 °C
for 3 days. Cooling the vessel to room temperature at a rate of
5
À1
°C h afforded crystals of 1–3 suitable for a single crystal X-ray
diffraction. For 1, yield: 0.497 g, 78% based on Cd. Anal. Calc for
C
3
1
8
7
24
H
20CdN
4
O
6
S
2
: C, 45.25; H, 3.16; N, 8.80. Found: C, 45.39; H,
À1
.24; N, 8.92%. IR (KBr, cm ): 2940 m, 2843 m, 1620 w, 1570 m,
498 m, 1433 m, 1326 m, 1199 s, 1064 s, 1030 s, 987 w, 930 m,
56 m, 831 m, 772 m, 755 m, 718 s, 662 s. For 2, yield: 0.478 g,
1
products were fully characterized by H NMR or otherwise com-
pared with the known compounds. The recovered catalyst was
washed with ethyl acetate, dried, and reused without further pur-
ification or regeneration. Moreover, the recovered catalysts were
characterized by the X-ray powder diffraction and showed identi-
cal results to those of the fresh samples.
5% based on Cd. Anal. Calc for C24
H
20CdN
4
O
6
S
2
: C, 45.25; H, 3.16;
À1
N, 8.80. Found: C, 45.16; H, 3.35; N, 8.97%. IR (KBr, cm ): 2986
m, 2853 m, 1534 m, 1465 w, 1432 m, 1339 s, 1239 m, 1214 s,
1
6
C
3
1
9
096 s, 1070 s, 987 w, 920 m, 834 m, 756 m, 753 m, 721 s, 662 s,
31 s. For 3, yield: 0.557 g, 55% based on Cu. Anal. Calc for
46
H
32Cu
2
N
10
O
6
S
2
: C, 54.59; H, 3.19; N, 13.84. Found: C, 54.72; H,
3
. Results and discussion
À1
.31; N, 14.12%. IR (KBr, cm ): 3138 s, 3115 s, 2989 m, 2858 m,
566 m, 1475 w, 1414 m, 1323 w, 1232 s, 1184 s, 1098 s, 1056 s,
03 w, 830 m, 776 m, 753 m, 718 s, 651 s, 632 s.
3.1. Synthesis and IR spectrum
The previous studies have demonstrated that hydrothermal
2
.3. X-ray structural studies
synthesis is a powerful synthetic strategy to prepare polymeric
solids with better crystallinity [28]. In the process of hydrothermal
synthesis, many factors such as initial reactants, metal-to-ligand
ratio, pH value, and temperature have a profound influence on
the final crystallization outcome. In this work, parallel experiments
show that the pH values of the reaction system are important facts
for improving the yield of the tree coordination polymers. The good
Crystallographic data of 1–3 were collected on a Bruker Smart
Apex-II CCD area detector at room temperature (graphite-
monochromated, Mo K -radiation, - and h-scan technique,
k = 0.71073 Å). Intensity data were corrected for Lorenz and
a
x
polarization effects and a multi-scan absorption correction was

L. Wang et al. / Inorganica Chimica Acta 430 (2015) 253–260
255
Fig. 1. (a) Coordination environment of the Cd atom in 1. The hydrogen atoms are omitted for clarity. Symmetry code: A = Àx + 2, Ày, Àz. B = x + 1, y, z. C = Àx + 1, Ày, Àz. (b)
View of 1D infinite chain along the b axis generated by the Cd(II) ions and the bib ligands. (c) View of 1D infinite chain along the c axis generated by the Cd(II) ions and the
2
,6-nds ligands. (d) View of the 3D polymeric framework of 1.
yields of polymers 1–3 could be obtained in the special pH values
of 4 for 1, and 4.5 for 2 and 3. When the pH value is lower or higher
than that special value, the expected crystals could be obtained in
lower yield. The elemental analyses for all the resulting three poly-
mers are in good agreement with the theoretical values.
3.2. Structure description
3.2.1. Crystal structure of 3D coordination polymers [Cd(2,6-
nds)(bib)] (1)
n
The single-crystal X-ray diffraction reveals that polymer 1 crys-
tallizes in the triclinic space group of P 1ꢀ . The asymmetric unit of 1
consists of half unique Cd(II) ion, half 2,6-nds anion and half bib
ligand. As shown in Fig. 1a, each Cd(II) ion is in a slightly distorted
octahedral coordination geometry coordinated by two nitrogen
from two individual bib ligands, and four oxygen atoms from four
individual 2,6-nds anions. The Cd–N distances are 2.256(3) and the
Cd–O bonds range between 2.339(3) and 2.368(3) Å. In addition,
the bond angles around each Cd(II) range from 84.25(11) to
180.0(8)° (Table 2). They are within the normal range expected
for such complexes [29]. In each bib ligand, the two imidazole rings
All three coordination polymers are stable in air and insoluble
in water and common organic solvents. The IR spectra of com-
plexes of 1–3 show that the aromatic C–H stretching frequencies
À1
extend through the region 2804–3078 cm . The well-resolved fre-
quencies of the aromatic rings span over the regions of 1250–1750
À1
and 500–980 cm
. Bands characteristic of the fundamental
and split
v
3
S–O stretching modes are observed in the range of
À1
1
000–1240 cm . The IR spectrum of 3, the broad and strong
À1
absorption at 3145–3410 cm is attributed to the N–H stretching
vibrations.

2
56
L. Wang et al. / Inorganica Chimica Acta 430 (2015) 253–260
Table 2
a
Selected bond distances (Å) and angles (deg) for the polymers 1–3 .
Complex 1
i
Cd(1)–O(2)ii
Cd(1)–N(1)
Cd(1)–N(1)
2.256(3)
2.256(3)
180.0(2)
84.25(11)
95.75(11)
95.75(11)
84.25(11)
Cd(1)–O(1)
2.339(3)
2.339(3)
2.368(3)
2.368(3)
Cd(1)–O(1)i
Cd(1)–O(2)
iii
i
ii
ii
i
iii
ii
N(1) –Cd(1)–N(1)
N(1)–Cd(1)–O(2)
90.40(11)
86.94(10)
93.06(10)
90.40(11)
89.60(11)
O(2) –Cd(1)–O(2)
180.00(8)
180.00(14)
89.60(11)
93.06(10)
86.94(10)
i
i
N(1) –Cd(1)–O(1)
O(1)–Cd(1)–O(2)
O(1)–Cd(1)–O(1)
i
ii
i
N(1)–Cd(1)–O(1)
O(1) –Cd(1)–O(2)
N(1) –Cd(1)–O(2)
i
i
i
iii
iii
N(1) –Cd(1)–O(1)
N(1) –Cd(1)–O(2)
O(1)–Cd(1)–O(2)
i
iii
i
iii
N(1)–Cd(1)–O(1)
N(1)–Cd(1)–O(2)
O(1) –Cd(1)–O(2)
Complex 2
Cd(1)–N(1)
Cd(1)–N(1)
N(1)–Cd(1)–N(1)
2.2407(16)
2.2407(16)
180.0
94.82(6)
85.18(6)
85.18(6)
94.82(6)
Cd(1)–O(3)#2
2.3279(14)
2.3279(14)
180.0
93.44(6)
86.56(6)
89.66(5)
90.34(5)
Cd(1)–O(1)i
Cd(1)–O(1)
2.3704(14)
2.3704(14)
86.56(6)
93.44(6)
90.34(5)
89.66(5)
180.0(1)
i
Cd(1)–O(3)#3
i
ii
iii
O(3) –Cd(1)–O(3)
N(1)–Cd(1)–O(1)
ii
i
i
N(1)–Cd(1)–O(3)
N(1)–Cd(1)–O(1)
N(1) –Cd(1)–O(1)
i
ii
i
i
ii
N(1) –Cd(1)–O(3)
N(1) –Cd(1)–O(1)
O(3) –Cd(1)–O(1)
iii
ii
i
iii
N(1)–Cd(1)–O(3)
O(3) –Cd(1)–O(1)
O(3) –Cd(1)–O(1)
i
iii
O(3) –Cd(1)–O(1)i
iii
i
N(1) –Cd(1)–O(3)
O(1) –Cd(1)–O(1)
Complex 3
Cu(1)–N(3)
ii
1.935(3)
Cu(1)–N(4)
2.031(3)
Cu(1)–O(2)
2.784(4)
iii
Cu(1)–N(5)
2.004(4)
128.47(15)
124.30(15)
ii
iii
iii
N(5)iii–Cu(1)–O(2)
N(4)–Cu(1)–O(2)
N(3) –Cu(1)–N(5)
N(5) –Cu(1)–N(4)
106.46(14)
98.81(14)
93.89(13)
84.48(13)
ii
ii
N(3) –Cu(1)–N(4)
N(3) –Cu(1)–O(2)
a
Symmetry transformations used to generate equivalent atoms for 1: (i) Àx + 2, Ày, Àz. (ii) x + 1, y, z. (iii) Àx + 1, Ày, Àz. (iv) x À 1, y, z. For 2: (i) Àx + 1, Ày + 1, Àz + 1. (ii)
Àx + 2, Ày + 1, Àz + 1. (iii) x À 1, y, z. For 3: (ii) x, y, z + 1. (iii) x À 1, y À 1, z.
are mutually parallel, and they form a dihedral angle of 58.425(3)°
2
sheets are further cross-linked via the l -1,5-nds ligands in differ-
with the corresponding phenyl ring, respectively.
ent orientation to form a 3D framework, as shown in Fig. 2d.
As depicted in Fig. 1b, the bib ligands adopt the
modes to bind adjacent Cd(II) centers forming a 1D zigzag poly-
meric [Cd(bib)]
chain along the b axis with the adjacent CdÁ Á ÁCd
separation of 15.323 Å. It is also noted that the other one 1D infi-
nite [Cd(2,6-nds)] chain along the c axis is formed by the connec-
2
l -bridging
3.2.3. Crystal structure of 2D coordination polymers [Cu(2,6-
nds)0.5(tpim)]n
n
In polymer 3, the asymmetric unit consists of one Cu(I) atom,
one tpim ligand, and half 2,6-nds, as shown in Fig. 3a. Each Cu(I)
atom sits in a tetracoordinate environment defined by three
N-donors from three individual tpim ligands and one oxygen atom
from one 2,6-nds. The Cu–O bond lengths are 2.784(4), and Cu–N
bonds range from 1.935(3) to 2.031(3) Å (Table 1), respectively,
n
tion of 2,6-nds with the Cd(II) ions, as depicted in Fig. 1c. In the
latter 1D chains, the distances of two adjacent Cd(II) are
5
.295(3) Å. Furthermore, these adjacent 1-D chains are connected
through -2,6-nds ligands to generate a 2-D sheet in the ac plane.
Finally, the resulting 2-D sheets are further linked via the
,6-nds ligands in up and down orientation to form a 3D frame-
work structure, as shown in Fig. 1d.
l
2
1
1
l
2
-g
:g
typical for bond lengths in similar compounds [31].
In the crystal structure, each tpim adopts a l3
-
g
1:
g
1:
g
1
bridg-
2
ing mode to bridge Cu(I) ions affording a 2D sheet, as depicted in
Fig. 3b. The 2D network structure consists of hexagon grids in
which the Cu(I)Á Á ÁCu(I) distances are 10.710(4), 13.458(3) and
3.2.2. Crystal structure of 3D coordination polymers [Cd(1,5-
1
3.651(7) Å, respectively. As shown in Fig. 3c, each 2,6-nds ligand
nds)(bib)] (2)
n
acts as an H-shaped bridge, linking two neighboring Cu(I) ions into
D layers.
The single crystal X-ray diffraction analysis reveals that 2 and 1
crystallize in the same space group and have similar cell parame-
ters (Table 1), indicating that they have similar structures. The
asymmetric unit of 2 consists of half unique Cd(II) ion, half
2
3.3. Fluorescence properties
1
,5-nds anion and half bib ligand. As shown in Fig. 2a, each Cd(II)
ion is in a slightly distorted octahedral coordination geometry
coordinated by two nitrogen from two individual bib ligands, and
four oxygen atoms from four individual 1,5-nds anions, similar to
those found in 1. The Cd–N distances are 2.241(2) Å, and the
Cd–O bonds range from 2.328(2) and 2.370(2) Å. The bond angles
around each Cd(II) range from 85.18(6) to 180.0° (Table 2). They
are in good agreement with those reported complexes [30]. In each
bib ligand, the two imidazole rings are mutually parallel, and they
form a dihedral angle of 70.586(8)° with the corresponding phenyl
ring, respectively.
The photoluminescent properties of 1, 2, and bib in solid state at
room temperature were studied. The emission spectra of polymers
1, 2 and ligand bib are very similar, as shown in Fig. 4. Upon exci-
tation at 275 nm, the strongest emission peak for free ligand bib
⁄
appears at 358 nm, corresponding to the n ?
p
transitions. For 1
and 2, excitation of the microcrystalline samples at 332 nm and
360 nm leads to the generation of intense fluorescent emissions,
with similar maximum peaks observed in the blue region (1,
360 nm and 2, 411 nm). The similarity of the emission and excita-
tion spectra is in agreement with the previous explanation by Chen
⁄
In 2, each bib adopts a
2
l -bridging mode to bridge Cd(II) ions
chain along the a axis
et al. [32], which indicates that a ligand-centered
p
?
p
excitation
generating a 1D zigzag polymeric [Cd(bib)]
n
is responsible for emissions in complexes 1 and 2.
with the adjacent CdÁ Á ÁCd separation of 14.215 Å, as shown in
Fig. 2b. Meanwhile, it is noted that all sulfonate groups act as a
3.4. Thermogravimetric analysis
1
1
2
l -g :g -bridge through its two O atoms. Thus, each 1,5-nds can
also link two adjacent Cd(II) centers to form a 1D infinite chain
along the c axis, as demonstrated in Fig. 2c. The nearest distance
of two adjacent Cd(II) is 5.458(4) Å. Furthermore, the two 1D
To investigate their thermal stabilities, thermogravimetric
analyses of polymers 1–3 were carried out under nitrogen atmo-
sphere. As shown in Fig. 5, polymers 1–3 show similar thermal
behaviors. The three polymers are thermally very stable up to
251 °C, because there are no solvent molecules in the frameworks.
chains are connected through
2
l -1.5-nds ligands to generate a
2
-D sheet in the ac plane, similar to that of 1. The resulting 2D

L. Wang et al. / Inorganica Chimica Acta 430 (2015) 253–260
257
Fig. 2. (a) Coordination environment of the Cd atom in 2. The hydrogen atoms are omitted for clarity. Symmetry code: A = Àx + 1, Ày + 1, Àz. B = Àx + 2, Ày + 1, Àz + 1.
C = x À 1, y, z. (b) View of 1D infinite chain along the b axis generated by the Cd(II) ions and the bib ligands. (c) View of 1D infinite chain along the c axis generated by the Cd(II)
ions and the 1,5-nds ligands. (d) View of the 3D polymeric framework of 2.
Subsequently, it keeps losing weight at 251–355 °C for 1, 258–
10 °C for 2, and 256–490 °C for 3, corresponding to the thermal
decomposition of the organic components.
excellent yield (Table 3, entry 1). To check the generality as well
as the effectiveness of our protocol, a number of aromatic and ali-
phatic amines were screened for this study, and the results are
listed in Table 3. The reaction proceeded with equal ease in the
case of substituted amines containing electron-donating func-
tionalities or not functionalities. This method is also very efficient
for aliphatic amines, such as cyclohexenamine (Table 3, entry 8).
However, probably because of steric reasons, ortho-chloroaniline
and ortho-methylaniline reacted slowly and gave a relatively lower
yield than the corresponding para isomers, respectively (Table 3,
entries 2 and 3, entries 5 and 6). It is noted that this reaction
5
3.5. Enamination of b-ketoesters
Recent studies have shown that some copper coordination com-
plexes exhibit interesting catalytic activities [25,33–35]. To evalu-
ate the catalytic activity of 3, the reaction of ethyl acetoacetate
with aniline was performed in solvent free conditions at room tem-
perature for 1 h, which generated the corresponding product in

2
58
L. Wang et al. / Inorganica Chimica Acta 430 (2015) 253–260
Fig. 3. (a) Coordination environment of the Cu atom in 3 with a labeling scheme and 30% thermal ellipsoids. The hydrogen atoms omitted for clarity. Symmetry operators:
A = x, y, z + 1; B = x À 1, y À 1, z. (b) View of a two-dimensional grid in 3. (c) View of 2D layer structure in 3.
displays the excellent chemoselectivity. The nucleophilic reactant
amine only reacts with the ketone of the b-ketoesters, in all the
cases no reaction with ester was observed to give the correspond-
ing amide, similar to that of our previous report [25].
To prove the heterogeneous mechanism of the condensation
catalyzed by polymer 3, the catalyst was filtered off after 15 min
reaction time and stirring of the filtrate continued at the same con-
1
dition. The reaction was again monitored by HMNR analysis. The

L. Wang et al. / Inorganica Chimica Acta 430 (2015) 253–260
259
Fig. 4. Fluorescence spectra of bib, 1 and 2 in the solid state at room temperature.
Fig. 5. Thermogravimetric analyses (TGA) curve of polymers 1–3.
Table 3
Synthesis of different b-enaminoesters using complex 3 as catalyst under solvent-free conditions.
NH2
R2
catalyst 5%
O
O
NH
O
R
1
r.t
R2
R1
O
O
.
Entry
1
Ketoester
Amine
Product
Time (h)
1
Yielda (%)
O
O
O
O
O
O
H N
96
94
95
2
O
O
O
NH
NH
O
O
O
O
2
3
2
1
H N
2
2
H N
NH
NH
O
O
4
O
O
2
H N
0.5
97
O
O
O
O
O
5
6
O
O
O
O
Cl
2
1
92
94
2
H N
O
O
NH
O
Cl
Cl
O
2
H N
Cl
NH
NH
O
O
O
O
7
8
O
O
O
O
2
H N
1
2
95
Br
O
O
Br
2
H N
90
NH
O
O
(
continued on next page)

2
60
L. Wang et al. / Inorganica Chimica Acta 430 (2015) 253–260
Table 3 (continued)
Entry
9
Ketoester
Amine
H N
Product
Time (h)
1
Yielda (%)
96
O
O
2
O
O
NH O
O
1
0
2
H N
Cl
1
95
O
O
Cl
NH
O
O
a
Isolated yield.
result confirms the assumption of a heterogeneous mechanism
since neither additional ethyl acetoacetate is consumed nor pro-
duct formed after filtration. Further, for a more comprehensive
study of the catalytic activity of 3 in the condensation of
b-ketoesters with primary amines, a recycling test with three
consecutive runs was performed (see Section 2 and Fig. S1). As
mentioned before, a product yield of 96% is achieved in the first
run after 1 h. In the second and the third run the product yields,
determined after the same reaction time (1 h), decrease to 94%
and 92%, respectively. Thus, the recovered materials remained
stable with complete retention of reactivity, which is further
confirmed by PXRD analysis, although the powder pattern for 3
showed the presence of some minor different peaks in the experi-
mental patterns, such as the positions, intensities, etc., compared
with that of the simulated (see Supporting Information, Fig. S1).
uk/data_request/cif. Supplementary data associated with this arti-
cle can be found, in the online version, at http://dx.doi.org/10.
1016/j.ica.2015.03.014.
References
[1] T.R. Cook, Y.R. Zheng, P.J. Stang, Chem. Rev. 113 (2013) 673.
[2] L. Ma, C. Abney, W. Lin, Chem. Soc. Rev. 38 (2009) 1248.
[
3] J. Wu, H.W. Hou, Y.X. Guo, Y.T. Fan, X. Wang, Eur. J. Inorg. Chem. 2009 (2009)
796.
4] G.-Z. Liu, J.-G. Wang, L.-Y. Wang, CrystEngComm 14 (2012) 951.
2
[
[5] F.-J. Liu, D. Sun, H.-J. Hao, R.-B. Huang, L.-S. Zheng, CrystEngComm 14 (2012)
79.
3
[
[
6] D.S. Deng, L.L. Liu, B.M. Ji, G.J. Yin, C.X. Du, Cryst. Growth Des. 12 (2012) 5338.
7] H.-Y. Liu, H. Wu, J.-F. Ma, J. Yang, Y.-Y. Liu, Dalton Trans. (2009) 7957.
[8] A.P. Côté, G.K.H. Shimizu, Coord. Chem. Rev. 245 (2003) 49.
9] J.W. Cai, Coord. Chem. Rev. 248 (2004) 1061.
[
[
[
10] J. Zhang, X.-H. Bu, Chem. Commun. (2008) 444.
11] T.L. Hu, W.P. Du, B.W. Hu, J.R. Li, X.H. Bu, R. Cao, CrystEngComm 10 (2008)
1037.
4
. Conclusions
[
12] C.H. Chen, J.W. Cai, C.Z. Liao, X.L. Feng, X.M. Chen, S.W. Ng, Inorg. Chem. 41
(
2002) 4967.
In this contribution, three new naphthalenedisulfonate poly-
[
13] Z.X. Lian, J.W. Cai, C.H. Chen, H.B. Luo, CrystEngComm 9 (2007) 319.
mers with diverse structures were successfully constructed under
[14] J.P. Zhao, B.W. Hu, F.C. Liu, X. Hu, Y.F. Zeng, X.H. Bu, CrystEngComm 9 (2007)
02.
9
hydrothermal conditions. With the help of multidentate imida-
[
15] N. Snejko, C. Cascales, B. Gomez-Lor, E. Gutiérrez-Puebla, M. Iglesias, C. Ruiz-
Valero, M.A. Monge, Chem. Commun. (2002) 1366.
À
zole-containing ligands, the SO
3
groups can be acted as potential
multidentate ligands and compete with water molecules for metal
ion coordination. More importantly, catalytic investigations have
revealed the polymer 3 to be excellent catalysts for enamination
of b-ketoesters. The polymer 3 shows excellent structural stability,
and retains good catalytic activity over several cycles, and display
chemo- and region-selectivity in the reaction process.
[16] J.S. Zhou, J.W. Cai, L. Wang, S.W. Ng, J. Chem. Soc., Dalton Trans. (2004) 1493.
[
[
[
[
17] J.W. Cai, C.H. Chen, X.L. Feng, C.Z. Liao, X.M. Chen, J. Chem. Soc., Dalton Trans.
2001) 2370.
18] J.-W. Cai, C.-H. Chen, C.-Z. Liao, X.-L. Feng, X.-M. Chen, Acta Crystallogr., Sect. B
57 (2001) 520.
19] A.P. Còté, M.J. Ferguson, K.A. Khan, G.D. Enright, A.D. Kulynych, S.A. Dalrymple,
G.K.H. Shimizu, Inorg. Chem. 41 (2002) 287.
20] G.K.H. Shimizu, G.D. Enright, C.I. Ratcliffe, K.F. Preston, J.L. Reid, J.A.
Ripmeester, Chem. Commun. (1999) 1485.
(
[
[
[
21] J.-W. Cai, J.-S. Zhou, M.-L. Lin, J. Mater. Chem. 13 (2003) 1806.
22] J.-W. Cai, C.-H. Chen, J.-S. Zhou, Chin. J. Inorg. Chem. 19 (2003) 81.
23] A.P. Marcus, R. Sarpong, Org. Lett. 12 (2010) 4560.
Acknowledgment
We gratefully acknowledge the financial support from the
National Natural Science Foundation of China (Grant No.
[24] A.Z.A. Elassar, A.A. El-Khair, Tetrahedron 59 (2003) 8463.
[25] Y. Zhao, D.S. Deng, L.F. Ma, B.M. Ji, L.Y. Wang, Chem. Commun. 49 (2013)
10299.
2
1272109), the Fundamental Research Funds for the Central
[
[
26] Bruker SHELXTL. Version 6.10, Bruker AXS Inc., Madison, Wisconsin, USA, 1997.
27] G.M. Sheldrick, SHELXS97 and SHELXL97, University of Göttingen, Germany, 1997.
Universities (No. CCNU14A05012), and the Foundation of the
Education Department of Henan Province (No. 2011B150021).
[28] B.M. Ji, D.S. Deng, X. He, B. Liu, S.B. Miao, N. Ma, W.Z. Wang, L.G. Ji, P. Liu, X.F. Li,
Inorg. Chem. 51 (2012) 2170.
[
29] N. Palanisami, P. Rajakannu, R. Murugavel, Inorg. Chim. Acta 405 (2013) 522.
Appendix A. Supplementary material
[30] X.Q. Liang, X.H. Zhou, C. Chen, H.P. Xiao, Y.Z. Li, J.L. Zuo, X.Z. You, Cryst. Growth
Des. 9 (2009) 1041.
[
31] C.C. Corrêa, L.B. Lopes, L.H.R. dos Santos, R. Diniz, M.I. Yoshida, L.F.C. de
Oliveira, F.C. Machado, Inorg. Chim. Acta 367 (2011) 187.
The details of X-ray diffraction, analytical and spectral data col-
lections, the corresponding spectra and Tables are given in the
Supplementary material. CCDC 1012200, 1012201, 929895 contain
the supplementary crystallographic data for compounds 1, 2 and 3
respectively. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.
[32] S.L. Zheng, J.H. Yang, X.L. Yu, X.M. Chen, W.T. Wong, Inorg. Chem. 43 (2004)
30.
[
[
8
33] M. Meldal, C.W. Tornøe, Chem. Rev. 108 (2008) 2952.
34] J.E. Hein, V.V. Fokin, Chem. Soc. Rev. 39 (2010) 1302.
[35] Y. Hua, A.H. Flood, Chem. Soc. Rev. 39 (2010) 1262.