Imidazole-directed fabrication of three polyoxovanadate-based copper frameworks as efficient catalysts for constructing C-N bonds

Article abstract of DOI:10.1039/d0dt02162h

A synthetic pathway for the directed preparation of three novel polyoxovanadate-based copper frameworks (POVCFs), i.e., [Cu0.5(1-ipIM)2]2[V4O11] (POVCF 1), [Cu(1-ipIM)2](VO3)2 (POVCF 2) and [Cu(1-pIM)4](HpIM)4[V10O28] (POVCF 3) (1-ipIM = 1-isopropylimidazole; 1-pIM = 1-propylimidazole) using bifunctional imidazole molecules as organic ligands and base has been developed. Systematic studies revealed that the variable base enviroment in the reaction is the key step in the preparation of 1D to 3D supermolecular networks of POVCFs 1-3. Single crystal X-ray diffraction analyses demonstrated that the Cu2+ atoms of POVCFs 1-2 were coordinated with four imidazole derivative molecules and two different polyoxovanadate {[V4O11]2- and [V10O28]6-} clusters, respectively, exhibiting a [CuN4O2] binding set and a distorted octahedral geometry. Specifically, POVCF 1 exhibited adjacent [V4O11]2- that dangle up and down arranged in a parallel 2D network and further coordinated with [Cu(1-ipIM)4]2+ to form a 3D supramolecular structure. However, POVCF 3 presented one tetrahedral coordinated vanadium atom and one four-coordinated copper atom and they further gave rise to a 1D network by the Cu-O and V-O bonds. More importantly, these POVCFs were further studied in the construction of C-N bond reactions of primary amines under mild conditions, and it was found that POVCF 1 displayed efficient heterogeneous catalytic activities in the Chan-Lam reaction (yields up to 89%). This journal is

Full text of DOI:10.1039/d0dt02162h

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DOI: 10.1039/D0DT02162H
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ARTICLE
Imidazole-Directed Fabrication of Three Polyoxovanadates-
based Copper Frameworks as Efficient Catalysts for
Constructing of C-N bonds
Received 00th January 20xx,
Accepted 00th January 20xx
Xianqiang Huang,*a Yuquan Qi,a Yuxiao Gua, Shuwen Gong,*a Guodong Shen,*a Qiang Li,a Jikun Li*b
DOI: 10.1039/x0xx00000x
The synthetic pathway for the directed preparation of three novel polyoxovanadates-based copper
frameworks (POVCFs), i.e., [Cu0.5(1-ipIM)2]2[V4O11] (POVCFs 1) and [Cu(1-ipIM)2](VO3)2 (POVCFs 2) and [Cu(1-
pIM)4](HpIM)4[V10O28] (POVCFs 3) (1-ipIM = 1-isopropylimidazole; 1-pIM = 1-propylimidazole) using
bifuncational imidazole molecules as organic ligands and base has been developed. Systematic studies
revealed the variable of base enviroment in the reaction is the key step in the preparation of 1D to 3D
supermolcular networks of POVCFs 1-3. Single crystal X-ray diffraction analyses demonstrated that the Cu2+
atoms of POVCFs 1-2 were coordinated with four imidazole derivates molecules and two different
polyoxovanadate {[V4O11]2-, [V10O28]6-} clusters, respectivley, exhibiting a [CuN4O2] binding set and the
distorted octahedral geometry. Especially, the POVCFs 1 exhibited the adjacent [V4O11]2- updown linked into a
parallel 2D network and further coordinated with [Cu(1-ipIM)4]2+ into a 3D supramolecular structure. On the
other hand, POVCFs 3 presented one tetrahedral coordinated vanadium atom and one four-coordinated
copper atom and they futher gave rise to a 1D network by the Cu-O and V-O bonds. More importantly, these
POVCFs were further studied in constructing of C-N bonds reactions of primary amines under mild conditions,
and found POVCFs 1 displayed efficient heterogeneous catalytic activities in the Chan-Lam reaction (yields up
to 89%).
www.rsc.org/
limitations of the separation of the products and catalyst recycling. 9-
10
One major challenge for these cross-coupling approaches is the
Introduction
recycling of catalysts. To overcome these limitations, heterogeneous
Construction of C-N bonds is one of the most important organic
reactions as well as formation of C-C bonds and have become a
cornerstone of synthetic, pharmaceutical and medical chemistry. 1,2
Over the past few years, various synthetic strategies for constructing
C-N bonds has been widely reported, such as the famous Buchwald
Hartwig and Ullmann cross-coupling reaction, etc. 3-5 However, these
cases mostly involved with the noble metal Pd salts or Pd complexes.
Compared with the above cross-coupling procedure, low-cost
copper-catalyzed Chan-Lam reaction also represented one of the
most powerful and straightforward tools to construct C-N bonds and
many excellent results have been presented. 6 In terms of Chan-Lam
catalysts including covalent organic framework, metal–organic
framework and functional coordination polymers have been well
11-12
developed.
Very
recently,
the
emerging
polyoxometalates−based frameworks, as
a class of promising
heterogeneous candidate catalysts, have attracted increasing
interest. 13-14
In this context, polyoxovanadates (POVs) as the classical family of
polyoxometalates (POMs) have attracted considerable attention in
regard to their bioinorganic chemistry, single molecular magnets,
and medicine as well as in homogeneous and heterogeneous
15
catalysis.
To achieve the heterogeneity of these catalysts and
reaction, various homogeneous catalysts have been employed for
improve the catalytic activity of POVs, transition-metal species have
been introduced into the POVs systems and led to a varieties of novel
heterogenous catalysts in various organic reactions.16 Recently, our
group reported three Pd-decavanadates have exhibited
7-8
the catalytic generation of C-N bonds.
Nevertheless,
homogeneous catalytic systems generally suffer from the inherent
17
heterogeneous aerobic oxidation of benzylic C-H bonds; lately,
a.Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel
Cell Technology, School of Chemistry & Chemical Engineering, Liaocheng
Wei’s
Group
discovered
with
an
unprecedented
effective heterogeneous
Zn-POVs
{V6O13[ZnC61H58N5O4]2}2-
University,
Liaocheng,
Shandong
252059,
China.
E-mail:
photocatalytic activity toward removal of rhodamine B. 18 To the best
of our knowledge, although several methods of transmit metal-
polyoxovanadates hybrids have been reported, the controllable
synthesis strategy of the POVs−based copper-frameworks with 1D,
2D and 3D structure have been limited and study on the Chan–Lam
hxqqxh2008@163.com
b.College of Chemistry and Chemical Engineering, Taishan University, Tai’an,
271000, P. R. China. E-mail: lijk0212@163.com
†Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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reactions catalysed by these POVs−based copper-frameworks is
rather rare. Hence, there is still a focus of ongoing research on
POVs−based frameworks catalysts for highly effective catalytic
construction of C-N bonds under ambient conditions.
View Article Online
DOI: 10.1039/D0DT02162H
Inspired by these previous works, we tried to introduce transition
metal copper ions into the POVs clusters to obtain hybrid copper-
polyoxovanadates, which might be a feasible way to improve their
catalytic property in the Chan-Lam reaction. Herein, we report three
POVs-based copper frameworks [Cu0.5(1-ipIM)2]2[V4O11] (POVCFs 1)
and [Cu(1-ipIM)2](VO3)2 (POVCFs 2) and [Cu(1-pIM)4](1-
HpIM)4[V10O28] (POVCFs 3), which are assembled by chemical
covalent interactions and formed 3D, 2D and 1D frameworks,
respectively. The three POVCFs were characterized by single crystal
X-ray diffraction (SCXRD), fourier transform infrared spectroscopy
(FT-IR), powder X-ray diffraction (PXRD) and elemental analyses.
Specially, the POVCFs 1 exhibited the two rare [V4O11]2- clusters
which dangle up and down linked into parallel 2D network, and
further coordinated with [Cu(2)(ipIM)4]2+ into 3D supramolecular
structure, it is different from the reported [V4O11]2-polyhedron. 19 In
this study, much attention is devoted to obtain a deep insight into
the catalytic studies of POVCFs towards coupling reaction of
phenylboronic acids with amines derivatives.
Figure 1. The asymmetric unit of POVCFs 1
Results and discussion
Figure 2. Coordination environment of Cu atom in the POVCFs 1
Syntheses
In order to controllable synthesize the various supramolecular
architectures of POVCFs with potential applications, we picked up
the simple vanadium source V2O5 as the starting material along with
1-ipIM to react with CuCl2·2H2O. At first, 1-ipIM as the organic ligand
and organic base bifunctional material was used as solvent and
ligand in the synthetic procedure, POVCFs 1 with 3D network was
obtained. When the amount of 1-ipIM was only reduced, remaining
V2O5 as the vanadium source, the 2D supramolecular network
POVCFs 2 was formed due to the different alkaline environment.
Then, we further used 1-pIM and 25% (CH3)4NOH instead of the I-
ipIM and NEt3 to change the reaction environment, POVCFs 3 was
obtained fortunately in a 1D chain. Based on the above results, the
base environment played a key role in the formation of these 3D, 2D
and 1D frameworks.
Figure 3. 2D network parallel to the bc plane of POVCFs 1
Structure Analysis of POVCFs [Cu0.5(1-ipIM)2]2[V4O11] (1)
SCXRD analysis displayed that the asymmetric unit of compound
[Cu0.5(1-ipIM)2]2[V4O11] (1) comprises two Cu2+ cations (the refined
occupancy factors of both Cu atoms are 0.5), one [V4O11]2- cluster and
four 1-ipIM N-ligands (Fig. 1). The structure of 1 may be described as
built from trans-[Cu(1-ipIM)4O2] octahedron and [VO4] tetrahedra
linked by shared μ2-O oxygen atom vertices. All Cu atoms of POVCFs
1 were six-coordinated by bonding to four N atoms from 1-ipIM
ligands and two O atoms from [VO4] tetrahedron, and presented the
distorted octahedral geometry, and each vanadium atom attains its
distorted tetrahedral geometry by coordinating to one terminal O
atom and three µ2-bridging O atoms. The details of bond distances
and bond angles of 1 are listed in Table S1. The Cu(II)−N bonds vary
from 2.035(4) to 2.037(5) Å, while the lengths of the Cu−O bonds are
2.407(4) Å. The V=O terminal bond distances in the range of 1.593(5)-
1.636(6) Å, which are similar to those of reported POVs clusters. 20
Figure 4. 3D supramolecular structure of POVCFs 1
In addition, the crystal of 1 adopts a 3D covalent network
structure. Such an intriguing structure can be described in the
following three steps: first, the adjacent VO4 tetrahedrons are linked
by the corner-sharing oxygen atoms and formed an intact [V4O11]2-
anion cluster, and then the adjacent [V4O11]2- cluster further connect
with each other to form a 1D chain structure along crystallographic
2 | J. Name., 2012, 00, 1-3
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c-axis by the sharing of oxygen vertices (O6) between [V(2)O4] and Structure Analysis of POVCFs (3) [Cu(1-pIM)4](1-HpIM)4[V10O28]
View Article Online
[V(3)O4] tetrahedrons. Then, the [V4O11]2-cluster formed by [V(1)O4]
and [V(2)O4] tetrahedrons serves as a tetradentate ligand to
coordinate to a [Cu(1)(1-ipIM)4]2+ subunit by its vertex oxygen atom
(O3) to connect the adjacent 1D chains into a 2D network parallel to
the bc plane. At last, the [V4O11]2- cluster formed by [V(3)O4] and
[V(4)O4] tetrahedrons in the 2D network coordinate to [Cu(2)(1-
ipIM)4]2+ subunit along crystallographic a-axis constructing a 3D
supramolecular structure, which is different with those of
Crystal structure analysis reveals thaDt OPIO: 1V0C.1F0s393/Dc0oDnTt0a2i1n6s2Ha
typical [V10O28]6- polyanion, a planar four-coordinated [Cu(1-pIM)4]2+
along with four protonated 1-HpIM+ counteraction parts. The
[V10O28]6- of 3 has a crystallographic inversion center on the midpoint
of the O8 and O8A and is made up of a ten distorted [VO6] octahedra.
The bond distances and angles of the [V10O28]6- anion (Table S1) are
22
comparable with structurally characterized [V10O28]6- units.
As
parts of the [V10O28]6- cluster in 3, the terminal oxygen atom O1 and
O1A form the bridges to two outer-shell [Cu(1-pIM)4]2+ cations.
Remarkably, the observed bond distance of V(1)-O(1) is 1.623(5) Å,
which is expected for the vanadyl oxygen double bonds, 23 whereas
the bond length of Cu(1)-O(1) is 2.491(5) Å, as a result of being the
relatively weak coordination bond. 24
[Ni(phen)2V4O11]
[Ni2(mIM)7·H2O)]V4O12·H2O. 21
Structure Analysis of Compound [Cu(1-ipIM)2](VO3)2 (2)
(phen
=
1,10-Phenanthroline)
and
Figure 5. The asymmetric unit of POVCFs 2
When we reduce the amount of 1-ipIM (ligand/base) and keep other
synthetic conditions the same with POVCFs 1, POVCFs 2 was achieved.
As presented in Fig. 5, the result of SCXRD analysis reveals that
Figure 7 The asymmetric unit of compound of POVCFs 3
POVCFs
2 contains only one crystallographically independent
vanadium atom and it is in a tetrahedral coordination environment.
The [VO4] tetrahedrons are connected to each other through two of
their vertex [O(2) and O(2)#, # represents symmetric code:-x, y+1/2,
In addition, a 1D supramolecular structure of 3 is formed along
crystallographic c-axis by Cu-O-V bridges as shown in Figure 8. The
supramolecular structure was further stabilized by N-H···O strong
hydrogen-bonding interactions between 1-HpIM+ cations and
[V10O28]6- anions (N(6)···O(5) 2.750(6) Å).
n-
-z+1/2], forming [VO3]n chains along crystallographic b-axis. The
adjacent [VO3]nn- chains are further linked together by [Cu(1-ipIM)2]2+
subunits, giving rise to a 2D network, parallel to the bc plane (Fig. 6).
The coordination environment of Cu atoms in 2 is different with that
of POVCFs 1 and the Cu atoms are four-coordinated by two O atoms
derived from two adjacent [VO3]nn- chains and two N atoms from 1-
ipIM ligands and formed a square planar geometry.
Figure 8. 1D network to the bc plane of POVCFs 3
IR analysis
In generally, IR spectrum can provide some important information
for investigation of polyoxovanadates-based copper frameworks. 25
The stretching bands of V = Ot in 1 appear at 941cm−1, 925 cm−1 for
2, 941cm−1 for 3. Absorption bands at 817, 738 and 665 cm−1 for
compound 1 (Fig. S1), 827, 725 and 660 cm−1 for compound 2 and
828, 756 and 625 cm−1 for compound 3 (Fig. S2-3) can be attributable
Figure 6. 2D network parallel to the bc plane of POVCFs 2
26
to the V–O–V stretching vibrations.
The apparent stretch
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absorption bands from 1638 cm−1 to 1514 cm−1 region are assigned Table 1. The effect of different parameters on Chan-Lam coupling reactionsa
View Article Online
b
to C=C and C=N (1-methylimidazole/1-ethylimidazole ligands). 27
DOI: 10.1039/D0DT02162H
Entry Catalyst(mol%)
Base
Solvent
Yield(%)
PXRD analysis
1
2
-
K2CO3
K2CO3
CH3OH
CH3OH
-
To further investigate the repeatability and purity of the three
polyoxovanadates-based copper frameworks, the obtained bulk
POVCOFs 1-3 were grinded to suitable powder for analysis. The
results of PXRD detection endorsed us to acknowledge that the three
synthesized samples were pure phase materials, respectively. As
shown in Fig. S4-6. These peaks positions of the simulated PXRD
patterns of POVCOFs 1-3 were in well agreement with those of as-
synthesized PXRD patterns, which revealed that the phase purity of
POVCOFs 1-3.
CuCl2(3)
28
3
4
1(3)
2(3)
3(3)
1(3)
1(3)
1(3)
1(3)
1(3)
1(3)
1(4)
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
Cs2CO3
K2CO3
CH3OH
CH3OH
CH3OH
EtOH
56
50
45
12
14
0
5
6
7
CH3CN
DMF
8
9
H2O
10
17
20
69
Chan-Lam catalytic reaction
10
11
12
CH3OH
CH3OH
CH3OH
At the outset of the investigation, we focused our attention on the
optimal conditions of Chan-Lam reaction and the reaction between
aniline (1a) and phenylboronic acid (2) was taken as the template
reaction to investigate the catalytic activities of these POVCFs
(Scheme 1).
In the case of the reaction without any catalyst, the reaction failed
to produce any product 3a (Table 1, entry 1). When the soluble
copper salt CuCl2 was used as a catalyst, 28% diphenylamine was
obtained, which suggested that copper species play an important
13
14
15
16
1(5)
1(6)
1(7)
1(6)
K2CO3
K2CO3
K2CO3
-
CH3OH
CH3OH
CH3OH
CH3OH
82
88
87
-
[a] All the reactions were carried out using 1a (0.2 mmol), 2 (0.3 mmol), and base
(0.4 mmol) in the presence of catalyst in solvent (2.0 mL) at room temperature for
16h. [b] Isolated yields.
role in the cross-coupling reaction (Table 1, entry 2), which was
28
With the optimal conditions in hand, the substrate scope of
amines including primary aryl amines and aliphatic amines were
successfully explored and found the variety of substituted amines
was well compatible in the present reaction and gave the desired
products in moderate to good yields (68-89%).
agreement with the previous report.
When the reaction was
performed with 3 mol% POVCFs catalysts, and we found that POVCFs
1-3 facilitated Chan-Lam reaction and the desired product 3a was
initially produced in 56%, 50% and 45% yields, respectively (Table 1,
entries 3-5), which all outperformed the result of using the CuCl2 as
the catalyst (Table 1, entry 2). Utilizing 3 mol % POVCFs 1 gave a
considerably higher yield (56 %) in 16 h, and found POVCFs 1 was
proved to be better catalyst than other two POVCFs 2-3, which
indicated that the different imidazole ligands, the six-coordinated
environment of copper ions and polyoxovantates cluster might affect
their catalytic activity on Chan-Lam coupling reaction, the same
result was observed with that of the previous work. 29
Hence, POVCFs 1 (3 mol %) was chosen as the optimal catalyst for
further screen the conditions for the Chan-Lam reaction. In the next
step, to finalize screening, changing the solvent to either EtOH, H2O
CH3CN or DMF all led to depletion in isolated yields of 3a (Table 1,
entries 6-9), whereas CH3OH proved to be more suitable solvent for
the reaction (Table 1, entry 5). Additionally, when Na2CO3, Cs2CO3
used as the base, respectively, the desired diphenylamine 3a was
obtained in lower yields (Table 1, entries 10-11). When the loading
of the catalyst was increased from 3 mol % to 6 mol %, pleasingly, the
yield of 3a increased significantly from 56% to 88% (Table 1, entries
3, 12-14). Notably, increasing the catalyst 1 loading (7 mol%) had an
First, the Chan-Lam reaction of a series of p-substituted primary
arylamines with phenylboronic acid were studied. The results
showed that the substrates bearing electron-donating groups (4-CH3,
4-OMe) or electron-withdrawing groups (4-Cl, 4-Br) was generally
supported and smoothly gave the desired products in moderate to
good yields (82-89%), and the primary arylamines bearing electron-
donating groups gave slightly better results (Table 2, entries 1-5).
Despite steric hindrance, 2-methylaniline and 3-chloroaniline
successfully afforded the corresponding products 3f-3g in a 72-80%
yields and it is obvious that the substrates with -Cl, -CH3 groups at
ortho- or meta-positions had no significantly effect on the C-N cross-
coupling reaction (Table 2, entries 6-7). Interestingly, in the case of
the reaction of aliphatic amine, cyclohexamine, with phenylboronic
acid, it afforded the desired product 3h in 68% yield under the
standard conditions (Table 2, entry 8). The results showed that
aliphatic amine also successfully afforded the corresponding product
in the presence of the POVCFs 1. The above experiments indicated
that these cross-coupling reactions of corresponding amine
derivatives catalyzed by POVCFs 1 exhibited good functional
tolerance, which could be conveniently applied in organic synthesis
for formation of C-N bonds. In view of the relatively milder reaction
conditions, the observed catalytic efficiency of the POVCFs 1 is
comparable with those of majority of the copper catalysts, even the
PdCu bimetallic nanoparticles catalysts. 30-32
no significant effect on product yield (Table 1, entry 15).
H
N
Catalyst
NH2
B(OH)2
+
rt
1a
2
3
Scheme 1 The Chan-Lam reaction using aniline and phenylboronic
acid as the substrates
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Recycling is very important advantages of heterogeneous
obtained by using a Rigaku D/max-2550 diffractometVeierwwAirttihcleCOun-lKinαe
radiation. The elemental analyses measurDeOmI:e1n0t.s10w39e/rDe0DdTo0n2e162oHn
Perkin-Elmer 240C elemental analyzer. 1H and 13C NMR spectra were
measured on Bruker 500 MHz spectrometer by using
tetramethylsilane (TMS) as the internal standard.
catalysts for their further large-scale applications. Hence, the
recycling of POVCFs 1 is selected to investigate the long-term stability
for constructing C-N bonds performance in a heterogeneous system.
After the completion of the reaction, the catalyst can easily be
separated from the reaction mixture by filtration and reused without
further treatment except drying under vacuum. The catalyst was
recycled for at least 3 runs without significantly losing its catalytic
activity (88% (first run); 86% (second run); 85% (third run)). In
addition, atomic absorption analysis demonstrated that there were
no copper and vanadium elements in the filtrate of the reaction,
which further exhibited that the catalyst 1 is heterogeneous in the
Synthesis
Synthesis of [Cu0.5(1-ipIM)2]2[V4O11] (1): V2O5 (2.75 mmol) and
triethylamine (2.75 mmol) were successively added to 15 mL
water in a clean beaker. The resulting solution was stirred at room
temperature for 60 min, and then CuCl2·2H2O (0.6 mmol), 1-
isopropylimidazole (3.6 mmol) were successively added to the
mixed solution. The resulting mixture was stirred for 12 h and
then heated at 50 °C for 30 min. Finally, the resulting mixture was
filtrated and the resulted filtrate stood for five days, and several
blue crystals suitable for X-ray diffraction were obtained. Yield:
47.8%. Anal. calcd. (%) (found) for C24H39N8O11V4Cu: C, 32.65
(32.47); H, 4.45 (4.49); N, 12.69 (12.53). IR (KBr, cm-1): 3445, 3121,
2984,1631, 1514, 1231, 1113, 983, 941, 862, 817, 738, 665, 492.
Chan-Lam coupling.
Table 2 Substrate scope for Chan-Lam coupling of amines with phenylboronic
acid.
H
POVCFs 1
rt
N
R
R
NH2
B(OH)2
+
3
1
2
En
try
Yield
(%)b
Amines
Product
Synthesis of [Cu(1-ipIM)2](VO3)2 (2): The synthetic procedure of
compound 2 is similar with that of compound 1, except that the
amount of 1-isopropylimidazole reduced from 3.6 mmol to 3.0
mmol. After leaving the resulted solution to stand at ambient
conditions for several days, blue crystals suitable for X-ray
diffraction were obtained. Yield: 35.7%. Anal. calcd. (%) (found)
for C12H20N4O6V2Cu: C, 29.92 (29.81); H, 4.18 (4.25); N, 11.63
(11.56). IR (KBr, cm-1): 3432, 3142, 2997, 2914, 1631, 1514, 1389,
1238, 1106, 971, 950, 897, 831, 756, 625, 474.
H
N
NH2
88
87
1
2
(1a)
(3a)
H
N
H3C
NH2
(1b)
H3C
(3b)
H
N
H3CO
NH2
(1c)
89
84
82
80
72
3
4
5
6
H3CO
(3c)
H
N
Cl
NH2
NH2
Synthesis of [Cu(1-pIM)4](HpIM)4[V10O28] (3): The synthetic
procedure of compound 3 is similar with that of compound 1,
except that the 25% (CH3)4NOH and 1-propylimidazole were used
instead of triethylamine and 1-isopropylimidazole. Yield: 33.5%.
Anal. calcd. (%) (found) for C48H80N16O28V10Cu: C, 30.31 (30.42); H,
4.24 (4.29); N, 11.78 (11.67). IR (KBr, cm-1): 3444, 3102, 2965,
1634,1528, 1398, 1277, 1109,960, 925, 827, 725, 660,452.
(1d)
Cl
Br
(3d)
H
N
Br
(1e)
(3e)
CH3
NH2
CH3
H
N
(1f)
(3f)
Characterization of the POVCFs crystals
Cl
H
Cl
N
SCXRD data for three POVCOFs 1-3 were performed on a Bruker-
AXS CCD diffractometer equipped with a graphite-monochromated
Mo-Ka radiation (λ = 0.71073 Å) at 298 K. All absorption corrections
were applied using multi-scan technique. The crystal structures of
POVCOFs 1-3 were solved by the direct method and refined through
full-matrix least-squares techniques method on F2 using the SHELXTL
2018 crystallographic software package. The crystallographic data
for POVCOFs 1-3 are summarized in Table 1.
NH2
7
8
(1g)
(3g)
H
N
NH2
68
(1h)
(3h)
[a] Reactions conditions: amines 1 (0.2 mmol), phenylboronic acid 2 (0.4 mmol),
and K2CO3 (0.4 mmol) POVCFs 1 (6 mol%) in CH3OH (2.0 mL) at room
temperature for 16h. [b] Isolated yields.
General Procedure for Chan-Lam Coupling Reactions of Amines
with phenylboronic Acids.
Experimental
Materials and instruments
Amines (0.2 mmol), phenylboronic acid (0.4 mmo), K2CO3 (0.4
mmol), POVCOFs (6 mol%) and CH3OH (2.0 mL) were added to a 25
mL Schlenk Tube. Then the tube was sealed and the reaction mixture
was subsequently stirred at room temperature in a Wattecs Parallel
Reactor for 16 h. After finished, the mixture was extracted with ethyl
acetate (3×5mL). The organic phase was combined and
concentrated. The resulting residue was purified by preparative thin
V2O5, 1-isopropylimidazole, 1-propylimidazole, triethylamine
copper (II) chloride dihydrate and other solvents and reagents
purchased from Aladdin Co., Ltd.
,
The FT-IR spectra of POVCFs 1-3 were recorded on Nicolet 170
SXFT/IR spectrometer in the range 4000–400 cm-1. PXRD data was
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
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ARTICLE
Journal Name
16 J. K. Li, X. Q. Huang, S. Yang, Y. Q. Xu and CV.ieWw.AHrtiucle, COrnylinset
layer chromatography using petroleum ether/ethyl acetate as
developing solvent to afford the desired products 3.
Growth Des., 2015, 15, 1907.
DOI: 10.1039/D0DT02162H
17 X. Q. Huang, J. K. Li, G. D. Shen, N. N. Xin, Z. G. Lin, Y. N.
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Conclusions
In summary, we have demonstrated the facile synthesis of three
new copper-polyoxovanadate with 3D, 2D and 1D frameworks
by employing various imidazole ligands and base environment.
Importantly, POVCFs 1 showed efficient catalytic activities
(yields up to 89%) in the Chan-Lam at room temperature. Work
is underway to explore the synthesis of new POVCFs and expand
this approach to other potential catalytic reactions for these
catalysts.
19 Y. Li, D. Zhang, L. Liu, W. Zhang, J. Zhang, Y. Cong, X. Li
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Conflicts of interest
There are no conflicts to declare.
24 D. Mendoza-Espinosa, G. E. Negrón-Silva, D. Ángeles-
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Acknowledgements
The work was financially supported by the National Natural
Science Foundation of China (21871125, 21802062, 21871026
and 21401094) and the Natural Science Foundation of
Shandong Province (No. ZR2019MB043, ZR2019QB022 and
ZR2017MB060).
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View Article Online
DOI: 10.1039/D0DT02162H
Three polyoxovanadates-based copper frameworks with 3D, 2D and 1D network using bifuncational imidazole
molecules as organic ligands and base has been developed. More importantly, these polyoxovanadates-based copper
frameworks displayed efficient heterogeneous catalytic activities in the Chan-Lam reaction under mild conditions.