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J. Chai et al. / Polyhedron xxx (2017) xxx–xxx
Gandara et al. prepared new CPs [InxGa1ꢁx(O2C2H4)0.5(hfipbb)],
which showed how the activity of a heterogeneous catalyst can
be controlled by modulating the ratio of different metals occupying
the same crystallographic position of the framework in one-pot
Strecker reaction [15]. Ji et al. reported that Cu-CPs, featuring Lewis
acid-type catalytic sites, as very efficient and reusable catalysts,
were used for the Strecker reaction of various aldimines [16].
In the process of construction and structural tuning of CPs,
organic ligand plays a crucial role. Benzimidazole-5,6-dicarboxylic
acid (H3bidc) as a bridging ligand possesses two carboxyl groups,
which can be partial or completely deprotonated, inducing rich
coordination modes and allowing interesting structures. H3bidc
has been validated to be a proper polydentate bridging ligand for
the formation of multidimensional CPs [17]. Here, based on the H3-
bidc ligand, we prepare two new In(III)/Sc(III)-based CPs, [InCl(H2-
bidc)2(H2O)]n (1) and [Sc(Hbidc)(OH)(H2O)]n (2). 1 features infinite
1D chains and is constructed to a 3D supramolecular framework
via hydrogen bonds. 2 shows a 3D supramolecular structure, built
from left- and right-handed chiral layers along the c axis with the
washed with distilled water, and dried in air. Yield: 80% for 2
(based on Sc(NO3)ꢀ6H2O). Elemental analysis (%) for 2: Anal. Calc.
C, 38.03; H, 2.46; N, 9.86; Found: C, 37.82; H, 2.55; N, 9.72. IR
(KBr pellet, cmꢁ1) for 2 (4000–400 cmꢁ1): 3487 (s), 1793 (w),
1535 (s), 1420 (s), 1269 (m), 1171 (w), 1045 (w), 956 (m), 809
(m), 773 (w), 615(w) (Fig. S6).
2.3. Single crystal X-ray crystallography
Crystallographic data for 1 were collected on a Rigaku R-AXIS
RAPID IP diffractometer with graphite-monochromated Mo Ka
(0.71073 Å) radiation, while those of 2 were collected on a Bruker
SMART APEX-II CCD diffractometer by using graphite-monochro-
mated Mo Ka radiation (0.71073 Å) radiation at a temperature of
296(2) K. All structures were solved by direct methods and refined
by full-matrix least-squares fitting on F2 by the SHELXTL-97 crystallo-
graphic software package [18]. All non-hydrogen atoms were
refined with anisotropic displacement parameters. The hydrogen
atoms attached to C and N atoms were placed in calculated posi-
tions and refined isotropically using a riding model with an Uiso(H)
equivalent to 1.2 times of Ueq(C) or Ueq(N). The hydrogen atoms on
coordinated water molecules were located in a difference Fourier
map and included in the final refinement by use of geometrical
constraints or restraints with the O–H distances being fixed at
0.85 Å. Crystal detailed data collection and refinement of CPs 1
and 2 are summarized in Table S1.
left- and right-handed chiral spiral chains. Interactions of
p–p
stacking between benzene ring and imidazole rings make the 3D
supramolecular more stable. The heterogeneous catalytic activities
of CPs 1 and 2 for the Strecker reaction of various aldimines under
mild condition have also been investigated. 1 displays good cat-
alytic capability for heterogeneous Strecker reaction with more
than 95% conversion yields after four consecutive runs.
2. Experimental
2.4. Catalytic experiment
2.1. Materials and instrumentation
Samples of 1 and 2 were activated at 200 °C for 12 h, soaked in
CH3OH for 24 h and then heated under vacuum at 80 °C for 12 h
under vacuum before the reaction. The basic framework of 1 and
2 are retained after activation. For the experiments of catalysis,
activated catalyst (0.04 mmol), aldimine (0.14 mmol) and TMSCN
All chemicals were obtained from commercial sources and used
without further purification. Powder X-ray diffraction (PXRD) data
were obtained using SHIMADAZU XRD-6000 diffractometer with
Cu Ka radiation (k = 1.5418 Å), with a step size and count time of
0.06° and 6 s, respectively. Infrared spectra (IR) were recorded on
a Nicolet Impact 410 spectrometer between 400 and 4000 cmꢁ1
using the KBr pellet method. Thermogravimetric analysis (TGA)
was conducted on a Perkin-Elmer TGA 7 thermogravimetric ana-
lyzer with a heating rate of 10 °C minꢁ1 from room temperature
to 800 °C. Elemental analysis was conducted on a Perkin Elmer
2400 elemental analyzer. 1H NMR spectra were measured with a
Bruker Avance 400 console at a frequency of 400 MHz.
(47 ll) in CDCl3 (2.4 l) were sequentially added to a standard 20 l
vial. The reaction mixtures were stirred at room temperature.
The reactions were monitored by 1H NMR spectroscopy and the
conversion yield was determined from the ratio of the integral of
the product signal in relation to the sum of integrals of all signals
(aldimine and product).
3. Results and discussion
3.1. Structural descriptions
2.2. Synthesis
3.1.1. Structural description of [InCl(H2bidc)2(H2O)]n (1)
2.2.1. Synthesis of [InCl(H2bidc)2(H2O)]n (1)
ꢀ
1 crystallizes in a triclinic P1 space group. The asymmetric unit
A mixture of H3bidc (0.0824 g, 0.4 mmol), InCl3ꢀ4H2O (0.2 ml,
0.1 M) was added to CH3CN (4 ml), HNO3 (0.4 ml, 1 M) and H2O
(1 ml) in a 23 ml Teflon-lined autoclave and then heated under
autogenous pressure at 120 °C for 24 h, then cooled to room tem-
perature under ambient conditions. Colorless block crystals were
obtained by filtration and washed with distilled water, and dried
in air. Yield: 85% for 1 (based on InCl3ꢀ4H2O). Elemental analysis
(%) for 1: Anal. Calc. C, 37.47; H, 1.73; N, 9.71; Found: C, 37.35;
H, 1.55; N, 9.78. IR (KBr pellet, cmꢁ1) for 1 (4000–400 cmꢁ1):
3254 (s), 1594 (s), 1384 (s), 1329 (s), 1035 (m), 1235 (m), 921
(w), 847 (w), 786 (s), 639 (m), 500 (m) (Fig. S5).
of 1 contains one crystallographically unique In3+ ion, two H2bidcꢁ
ligands, one coordinated H2O molecule and one terminal chlorine
atom. As shown in Fig. 1a, the In3+ ion with six coordinated envi-
2.2.2. Synthesis of [Sc(Hbidc)(OH)(H2O)]n (2)
A mixture of H3bidc (0.0206 g, 0.1 mmol), Sc(NO3)ꢀ6H2O (0.5 ml,
0.2 M) was added to H2O (9 ml), KOH (20 ll, 1 M) in a 23 ml
Teflon-lined autoclave and then heated under autogenous pressure
at 160 °C for 24 h, then cooled to room temperature under ambient
conditions. Colorless block crystals were obtained by filtration and
Fig. 1. Coordination environment of In3+ ion in 1. Symmetry mode: A = 1 ꢁ x, ꢁy,
ꢁz; B = 1 ꢁ x, ꢁy, 1 ꢁ z.