Nickel-metalated porous organic polymer for Suzuki-Miyaura cross-coupling reaction

Article abstract of DOI:10.1039/c9ra03679b

A new Ni(ii)-α-diimine-based porous organic polymer, namely Ni(ii)-α-diimine-POP, was constructed in high yield via the Sonogashira coupling reaction between the metallo-building block of Ni(ii)-α-diimine and 1,3,5-triethynylbenzene. Besides the high thermal and chemical stability, the obtained Ni(ii)-α-diimine-POP can be a highly active reusable heterogeneous catalyst to promote the Suzuki-Miyaura coupling reaction. The obtained results indicate that the Ni(ii)-α-diimine-POP herein is a promising sustainable alternative to the Pd-based catalysts for catalysing the C-C formation in a heterogeneous way.

Full text of DOI:10.1039/c9ra03679b

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Nickel-metalated porous organic polymer for
Suzuki–Miyaura cross-coupling reaction†
Cite this: RSC Adv., 2019, 9, 20266
*
Ying Dong,‡ Jing-Jing Jv,‡ Yue Li, Wen-Han Li, Yun-Qi Chen, Qian Sun,
*
Jian-Ping Ma
and Yu-Bin Dong
A new Ni(II)-a-diimine-based porous organic polymer, namely Ni(II)-a-diimine-POP, was constructed in
high yield via the Sonogashira coupling reaction between the metallo-building block of Ni(II)-a-diimine
and 1,3,5-triethynylbenzene. Besides the high thermal and chemical stability, the obtained Ni(II)-a-
diimine-POP can be a highly active reusable heterogeneous catalyst to promote the Suzuki–Miyaura
coupling reaction. The obtained results indicate that the Ni(II)-a-diimine-POP herein is a promising
sustainable alternative to the Pd-based catalysts for catalysing the C–C formation in a heterogeneous way.
Received 16th May 2019
Accepted 21st June 2019
DOI: 10.1039/c9ra03679b
rsc.li/rsc-advances
methane,8 chemical bond activation,9 bimetallic catalysis,10
reductive cross-coupling reaction,11 and reductive amination.12
Introduction
On the other hand, porous organic polymers (POPs), as
a typical class of porous organic materials, have been broadly
applied in the eld of gas storage and separation,13 drug
delivery,14 water treatment15 and heterogeneous catalysis.16 On
account of their high surface area, controllable porosity and
ability to be functionalized, both crystalline and amorphous
POPs, such as covalent organic frameworks (COFs),17 hyper-
crosslinked polymers (HCP),18 porous aromatic frameworks
(PAFs),19 polymers of intrinsic microporosity (PIMs),20 conju-
gated microporous polymers (CMP),21 are an promising class of
carriers to upload active catalytic species. So far, the metal
nanoparticle (M NP) loaded and metalated POPs by post-
synthetic approach have been the main theme in the fabrica-
tion of POP-supported metal-solid catalysts.22 In principle, the
POP-based and metal-involved catalytic materials could also be
prepared by in situ one-pot assembly of metal-containing
building blocks. By doing so, the POPs with high-density and
evenly distributed metal catalytic sites would be generated. So
far, the metalated POPs obtained in this way, however, are very
rarely reported.23
Homogeneous metal catalysts play a leading role in C–C bond-
forming reactions.1a Due to the increasing environmental issues
and need for sustainable development, the metal-involving
heterogeneous catalysts for C–C coupling such as in the
Suzuki–Miyaura cross coupling reaction have drawn more and
more attention during the past several decades. Among them,
the precious palladium-based catalysts have been the protago-
nist.1b To date, various solid carriers such as metal–organic
frameworks (MOFs), covalent organic frameworks (COFs),
carbon-based nanomaterials (CNMs), silica, and so on were
employed to support precious Pd complex,2 Pd NP3 and Pd-
bimetallic alloy4 for the fabrication of Pd heterogeneous cata-
lysts. In contrast, the rst row transition metals such as Ni are
rarely used to fabricate the solid carrier-supported heteroge-
neous catalysts. Compared to Pd, Ni is more reactive, low-cost
and earth-abundant. As a sustainable alternative to Pd, the Ni-
based catalysts, especially solid carrier supported Ni metal
catalysts, for the C–C cross-coupling reactions are extremely
appealing.5
The a-diimine-based metal catalysts have gained remarkable
attention because of their easy synthesis, air stability, and high
catalytic activity.6 For example, a-diimine Ni(II) complexes have
been widely used in polymerization,7 dry CO2 reforming of
In this contribution, we report, the rst of its kind, a Ni(II)-
POP which was generated from the metallo-building block of
Ni(II) a-diimine and 1,3,5-triethynylbenzene via Sonogashira
cross-coupling reaction under solvothermal conditions. The
obtained Ni(II)-a-diimine-POP can be a highly active and reus-
able heterogeneous catalyst to promote Suzuki–Miyaura cross-
coupling reactions.
College of Chemistry, Chemical Engineering and Materials Science, Collaborative
Innovation Centre of Functionalized Probes for Chemical Imaging in Universities of
Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education,
Shandong Normal University, Jinan 250014, P. R. China. E-mail: dongyinggreat@
163.com; yubindong@sdnu.edu.cn
Results and discussion
Structural and morphological characterization
† Electronic
supplementary
information
(ESI)
available:
additional
characterization of Ni(II)-a-diimine-POP, and product characterization. CCDC
1906672. For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c9ra03679b
Ni(II)-a-diimine-POP was successfully synthesized through
‡ These authors contributed equally to this work.
a Sonogashira coupling reaction following the route outlined in
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Fig. 1 (a) IR spectra of Ni(II)-a-diimine-POP and its precursors. (b)
Solid-state 13C NMR of Ni(II)-a-diimine-POP.
also supported this POP formation. As indicated in Fig. 1b, the
peak for the aliphatic carbon atoms of –CH3 and –CH(CH3)2
groups was located at 19.03 ppm.24 The broad signals centred at
74.58 and 132.40 ppm were respectively ascribed to the bridging
–C^C– and phenyl moieties.25 The signal at 163.62 ppm was
associated with carbon atom in the imine group.26
The TGA trace indicated that the obtained Ni(II)-a-diimine-
ꢀ
POP remained intact till temperature over 250 C, implying its
good thermal stability (Fig. 2a). Notably, no Ni NP was gener-
ated during POP formation process, which demonstrated by the
high-resolution transmission electron microscopy (HRTEM,
Fig. 2b). The existed Ni species valence was demonstrated by the
X-ray photoelectron spectroscopy (XPS) measurement. As shown
in Fig. 3a, the observation of 2p3/2 and 2p1/2 peaks at 855.97 and
873.28 eV conrmed that the nickel species in Ni(II)-a-diimine-
POP existed as Ni(II).27 The other observed doublet was attrib-
uted to intensive shake-up satellites that always occurs for Ni(II)
during acquiring XPS.27 On the other hand, the single N 1s peak
in B (399.03 eV) and Ni(II)-a-diimine-POP (398.96 eV) shied to
higher binding energy compared to that of A (398.88 eV), sug-
gesting that Ni(II) species in B and Ni(II)-a-diimine-POP was
chelated by N donors (Table 1).28 Inductively coupled plasma
(ICP) analysis showed that the nickel content in Ni(II)-a-dii-
mine-POP was up to 7.6 wt% (calcd 8.3 wt%).
As mentioned above, the Ni(II)-a-diimine-POP herein was
prepared by metallo-building block via in situ one-pot approach,
so it should feature the uniform texture. As shown in Fig. 3b, the
C, N, Ni and Br species evenly distributed in the POP matrix, as
evidenced by the SEM-energy dispersive X-ray (EDX) mapping.
The crystalline nature of the Ni(II)-a-diimine-POP was char-
acterized by PXRD measurement (Fig. S2, ESI†). A observed
broad peak from 20 to 25ꢀ suggested its amorphous nature. The
N2 sorption analysis at 77 K was used to measure its specic
Scheme 1 Synthesis of ligand A, metallo-building block B and Ni(II)-a-
diimine-POP. The photograph and SEM image of Ni(II)-a-diimine-POP
are inserted.
Scheme 1. The diiodine-substituted ligand A was prepared as
the bright yellow crystalline solids by double Schiff-base
condensation between 4-iodo-2,6-diisopropylbenzenamine and
butane-2,3-dione in good yield. The metallo-building block B
was synthesized as the brick-red crystalline solids by metalation
of A with DME(NiBr2) in moderate yield. Besides routine char-
acterizations, the molecular structure of A was further deter-
mined by the X-ray single crystal analysis (CCDC 1906672,
Fig. S1, Tables S1 and S2, ESI†). Aer combination of B and
1,3,5-triethynylbenzene, the Ni(II)-a-diimine-POP was generated
through Sonogashira cross-coupling reaction under sol-
vothermal conditions (toluene, 80 ꢀC, 72 h, 86%). Aer the
reaction, the resulting precipitate was treated by Soxhlet
extraction with CH2Cl2, methanol and acetone to remove any
ꢀ
possible residues. Aer dried in vacuo at 110 C for 12 h, the
target POP was obtained as deep brown solids (Scheme 1, inset).
The obtained POP was the irregular granular particle which was
well evidenced by the scanning electron microscopy (SEM,
Scheme 1, inset).
IR spectra (Fig. 1a) showed that the characteristic peaks at
3278 cmꢁ1 attributed to the nC–H (–C^C–H) in 1,3,5-triethy-
nylbenzene basically disappeared in Ni(II)-a-diimine-POP aer
coupling reaction, meanwhile the band at 2109 cmꢁ1 that cor-
responded to the –C^C– in 1,3,5-triethynylbenzene moved to
2206 cmꢁ1, indicating that the precursors of B and 1,3,5-trie-
thynylbenzene in POP were successfully connected to each other
via covalent C–C bond. Furthermore, the solid-state 13C NMR
Fig. 2 (a) TGA trace of Ni(II)-a-diimine-POP. (b) HRTEM image of
Ni(II)-a-diimine-POP.
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Table 2 Optimization of the model Suzuki coupling reaction between
iodobenzene and phenylboronic acida
Cat. (Ni mol%
Entry equiv.)
Base
Solvent T (ꢀC) T (h) Yieldb (%)
1
2
3
4
5
6
7
8
5
5
5
5
5
5
5
5
5
5
5
5
5
2
3
4
5
5
5
5
5
—
K3PO4$3H2O DMF
K3PO4$3H2O IPA
K3PO4$3H2O Dioxane 100
K3PO4$3H2O Acetone 100
K3PO4$3H2O Toluene 100
100
100
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
4
6
6
41
70
67
27
99
23
8
94
85
38
12
0
K3PO4$3H2O THF
K3PO4$3H2O CH3CN 100
100
K3PO4
K2CO3
TEA
DBU
Pyridine
Piperidine
Toluene 100
Toluene 100
Toluene 100
Toluene 100
Toluene 100
Toluene 100
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Fig. 3 (a) XPS spectrum of Ni species in Ni(II)-a-diimine-POP. (b) SEM-
EDX spectrum of Ni(II)-a-diimine-POP and it after five catalytic runs.
(c) N2 sorption isotherm of Ni(II)-a-diimine-POP.
0
K3PO4$3H2O Toluene 100
K3PO4$3H2O Toluene 100
K3PO4$3H2O Toluene 100
K3PO4$3H2O Toluene r.t.
K3PO4$3H2O Toluene 50
K3PO4$3H2O Toluene 80
K3PO4$3H2O Toluene 100
K3PO4$3H2O Toluene 100
K3PO4$3H2O Toluene 100
45
68
89
12
53
85
58
79
0
surface area with architectural rigidity and permanent porosity
(Fig. 3c). Brunauer–Emmett–Teller (BET) analysis of Ni(II)-a-
diimine-POP indicated its surface area was up to 265.3 m2 gꢁ1
.
Also, the pore size of the POP was determined based on the N2
sorption isotherm by employing the nonlocal density functional
theory (NLDFT) method, and a series of sharp and broad peaks
were observed. It was found to be mostly mesoporous having
the major contribution of the pore width at ca. 2.7 nm (Fig. S2,
ESI†).
a
Reaction conditions: iodobenzene (1.0 mmol), phenylboronic acid (1.1
mmol), base (2.0 mmol), solvent (2 mL), in N2. b Yields were determined
by GC analysis (Fig. S4, ESI).
K3PO4$3H2O was better than the other inorganic and organic
bases (Table 2, entries 8–13). Furthermore, when the reaction was
carried out with less catalyst loading, 2 (Table 2, entry 14), 3
(Table 2, entry 15) or 4 mol% (Table 2, entry 16) instead of
5 mol%, the coupled product was obtained in signicantly lower
45–89% yields. On the other hand, the reaction temperature
appeared to be crucial to the catalytic efficiency. As indicated in
Table 2, the catalytic activity of Ni(II)-a-diimine-POP was signi-
cantly diminished at lower temperature (from r.t. to 80 ꢀC, Table
2, entries 17–19). Also, shortening reaction time of 4–6 h would
also lead to the signicantly reduced 58–79% yields under the
given reaction conditions (Table 2, entries 20–21). We did not
observe any coupled product formation in the absence of the
nickel source (Table 2, entry 22), further conrming the loaded Ni
served as the catalytic active sites.
Catalytic properties
Next, we examined the catalytic activity of Ni(II)-a-diimine-POP
for the Suzuki–Miyaura cross coupling reactions, in which the
iodobenzene and phenylboronic acid coupling was chosen as the
model reaction (Fig. S3, ESI†). As shown in Table 2, the solvent
screening revealed that toluene is the best one among the other
solvents such as N,N-dimethylformamide (DMF), iso-propyl
alcohol (IPA), dioxane, acetone, tetrahydrofuran (THF), and
CH3CN that we tested (Table 2, entries 1 to 7). In addition, various
bases, including K3PO4$3H2O, K2CO3, triethylamine (TEA), 1,8-
diazabicyclo[5.4.0]undec-7-ene (DBU), pyridine, and piperidine,
were used to performed the reaction, and we found that
Table 1 XPS spectra of A, B, NiBr2, Ni(II)-a-diimine-POP and it after five catalytic runs
Compound
N 1s1/2 (eV)
Ni 2p3/2 (eV)
Ni 2p1/2 (eV)
A
398.88
—
399.03
398.96
398.92
—
—
NiBr2
B
855.40
856.28
855.97
856.16
872.98
872.79
873.28
873.68
Ni(II)-a-diimine-POP
Ni(II)-a-diimine-POP aer 5 runs
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Based above result, the optimized reaction conditions for the
model coupling reaction were determined as: iodobenzene,
1.0 mmol; phenylboronic acid, 1.1 mmol; Ni(II)-a-diimine-POP,
5 mol% Ni equiv.; K3PO4$3H2O, 2.0 mmol; temperature, 100 ꢀC;
reaction time, 8 h; toluene, 2 mL.
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Table 3 Cross-coupling reactions of various aryl halides and aryl boric
acids catalysed by Ni(II)-a-diimine-POPa
To verify the heterogeneous nature of this POP-based cata-
lyst, the hot leaching test was conducted. As shown in Fig. 4a,
no further reaction occurred aer ignition of the reaction at
4.0 h when it reached the yield of ca. 65%, at which point the
heterogeneous particles were centrifuged out of the reaction
mixture, and the reaction was performed for additional 4 h. GC
analysis indicated that the yield of the reaction did not change
during the prolonged reaction time, indicating that the Ni(II)-a-
diimine-POP exhibited a typical heterogeneous catalyst nature
herein.
Entry
R1
X
R2
t (h)
Product
Yieldb (%)
1
2
3
4
5
6
7
8
9
H
Br
Br
Br
Br
Br
Br
Br
Br
Br
I
I
I
I
I
I
I
I
I
H
H
H
H
H
H
H
H
12
12
12
12
12
12
12
12
12
8
8
8
8
8
8
8
8
8
i
ii
94
97
98
92
90
90
93
92
90
4-NO2
4-COCH3
4-OCH3
4-CO2CH3
2-CN
2-CH3
3-NO2
H
iii
iv
v
vi
vii
viii
iv
i
ix
viii
iv
x
Once we conrmed the heterogeneous nature of the catalyst,
we also tested its recyclability. Aer each catalytic run, the solid
4-OCH3
H
H
H
H
H
H
H
catalyst was separated by centrifugation, washed with toluene (3 10
H
99
ꢀ
11
12
13
14
15
3-CH3
3-NO2
4-OCH3
4-CN
4-CO2CH3
2-OCH3
2-CF3
3-NO2
4-CN
H
>99
>99
>99
>99
>99
92
90
99
>99
>99
98
ꢂ 2 mL), CH3CN (3 ꢂ 2 mL), and dried at 110 C for 12 h in
vacuum. The recycling catalytic runs were conducted by
combining the recovered catalyst with inorganic base, iodo-
benzene, and phenylboronic acid in toluene. As shown in
v
Fig. 4b, the solid catalyst of Ni(II)-a-diimine-POP still showed 16
excellent activity and the cross-coupling yield was even up to
90% aer ve catalytic cycles (Fig. S5, ESI†). Aer multiple
catalytic cycles, ICP measurement demonstrated that the Ni
content in Ni(II)-a-diimine-POP was 6.3 wt%, suggesting a 17%
Ni leaching occurred aer ve catalytic runs. This catalyst loss 22
might be responsible for this slight yield decrease. On the other
hand, no valence change for Ni species was observed (Table 1),
xi
xii
xiii
xiv
vii
iii
v
17
18
19
20
H
4-F
I
I
I
I
I
Cl
3-OCH3
2-CH3
4-COCH3
4-CO2CH3
4-OCH3
H
8
8
8
8
8
12
21
H
H
H
H
98
90
26
23
24
iv
i
a
implying that the Ni species in POP was stable during the
Reaction conditions: aryl halide (1.0 mmol), arylboronic acid (1.1
mmol), K3PO4$3H2O (2 mmol, 0.533 g), Ni(II)-a-diimine-POP (5 mol%
reusable processes under the given conditions. In addition, the
POP morphology and elemental distribution were well main-
tained aer the recycle (Fig. 3b and S6†).
b
Ni equiv.), toluene (2 mL), 100 ꢀC, N2. Yields were determined by GC
analysis (Fig. S7, ESI).
To test the available scope of this catalyst, we performed
coupling reactions of phenylboronic acid with a series of
substituted aryl halides under optimized conditions (Table 3). It
is noteworthy that the catalytic system was tolerant to a wide
range of functional groups such as –CF3, –NO2, –COCH3, –CH3,
–OCH3, –CO2Me, and –CN at different substituted positions.
Aryl bromides with both electron-donating and electron-
withdrawing groups at para-, meta- or ortho-substituted posi-
tion afforded cross-coupling products of i–viii (Table 3, entries
1–9) with good-to-excellent yields (90–98%). Compared to aryl
bromides, the aryl iodides for the cross-coupling reaction were
more active. As shown in Table 3 (entries 10–15), the yields for
the target coupled products of i, iv, v and viii–x based on iodo-
benzene and para- or meta-substituted aryl iodides were more
than 99%. Meanwhile, the ortho-substituted iodobenzene
provided the products of xi and xii in slightly lower 90–92%
yields (Table 3, entries 16 and 17). On the other hand, the
crossing-coupling reactions between aryl iodide and phenyl-
boronic acids with both electron- donating and electron-
withdrawing groups at para-, meta- or ortho-substituted posi-
tion still afforded excellent 98 to >99% yields (Table 3, entries
18–22, compounds iii, v, vii, xiii and xiv). The slightly lower 90%
yield for iv from para-methoxyphenylboronic acid with aryl
iodide was also observed (Table 3, entry 23). However, the
chlorobenzene and phenylboronic acid coupling gave a low 26%
yield of i in 12 h (Table 3, entry 24), indicating that the Ni(II)-a-
diimine-POP cannot signicantly activate the ArCl-based
Suzuki–Miyaura cross-coupling reactions.
Compared to the reported Ni-loaded solid catalytic systems
(Table 4), which usually contained coexistent such as PPh3 or
other metal oxides, for the Suzuki–Miyaura coupling reaction, it
Fig. 4 (a) Reaction time examination and leaching test for the model
Suzuki cross-coupling reaction. (b) Catalytic cycle for the model
Suzuki cross-coupling reaction.
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Table 4 Comparison of Ni(II)-a-diimine-POP with the reported Ni-loaded solid catalysts for the Suzuki cross-coupling reaction between
iodobenzene/bromotoluene and arylboronic acid
Cat. (mol%)
Conditions
Substrate/yield (%)
Run
Ref.
Ni/Cg (8)
PPh3/dioxane/THF, n-BuLi/KF/LiOH, reux, 9 h
MeOH/H2O, K2CO3, 60 ꢀC, 8 h
CH3CN, K2CO3, 65 ꢀC, 12 h
4-BrPhMe/PhB(OH)2/87
PhI/PhB(OH)2/97
2
6
—
—
—
7
33
34
35
35
35
35
Ni-PVP/TiO2–ZrO2 (20)
UiO-66(L1)/NiCl2/PPh3 (3)
UiO-66(L2)/NiCl2/PPh3 (3)
UiO-66(L3)/NiCl2/PPh3 (3)
UiO-66(L3)/Ni(COD)2/PPh3 (3)
Ni(II)-a-diimine-POP (5%)
Ni(II)-a-diimine-POP (5%)
PhBr/PhB(OH)2/71
PhBr/PhB(OH)2/84
PhBr/PhB(OH)2/90
PhBr/PhB(OH)2/96
PhI/PhB(OH)2/99
CH3CN, K2CO3, 65 ꢀC, 12 h
CH3CN, K2CO3, 65 ꢀC, 12 h
CH3CN, K2CO3, 65 ꢀC, 12 h
Toluene, K3PO4$3H2O, 100 ꢀC, 8 h
Toluene, K3PO4$3H2O, 100 ꢀC, 12 h
5
5
This work
This work
PhBr/PhB(OH)2/94
exhibited an impressive catalytic performance. On the other ask. Then, 10 mL cyclohexane and 4 mL saturated Na2CO3
hand, we believe the Ni-catalysed Suzuki–Miyaura cross- solution added in succession. Aer stirred at room temperature
coupling reaction herein went through the same mechanism for 12 h, the mixture was diluted with EtOAc (20 mL) and
as the reported one,33–35 which should involve the initial washed with saturated Na2S2O3 (3 ꢂ 40 mL). The combined
oxidative addition of the aryl halide to a Ni(0) species, followed organic layer was dried with anhydrous MgSO4. The crude
by trans-metalation and subsequent reductive elimination step product was puried by column chromatography (petroleum
to afford the expected coupling product, meanwhile the cata- ether/EtOAc ¼ 10/1) to give 4-iodo-2,6-diisopropylbenzenamine
1
lytically active nickel(0) species was regenerated (Fig. S8, ESI†). as a black liquid (3.90 g, 96%). H NMR (400 MHZ, CDCl3) d:
7.37 (s, 2H), 3.82 (s, 2H), 2.94 (2m, 2H), 1.37 (m, J ¼ 8 Hz, 12 H);
13C NMR (400 MHz, CDCl3), d: 22.4 (4c), 28.0 (2c), 81.2, 131.8
(2c), 135.1 (2c), 140.2.; IR (KBr): 3486 (w), 3404 (w), 2961 (vs),
Experimental
Materials and measurements
2870 (m), 1618 (s), 1570 (w), 1460 (s), 1438 (vs), 1384 (m), 1364
(m), 1350 (m), 1299 (w), 1250 (m), 1208 (m), 1125 (w), 1061 (w),
924 (w), 865 (m), 832 (w), 765 (w), 746 (w), 716 (w), 555 (w).
HRMS (ESI-TOF) calcd for C12H19IN ([M + H]+), m/z 304.0517;
found, m/z 304.0592.
All chemicals and solvents were at least of analytic grade and
employed as received without further purication. The
elemental analysis was conducted on a PerkinElmer Model 2400
analyzer. MS spectra were obtained by Bruker maxis ultra-high
resolution-TOF MS system. NMR data were collected using an
AM-400 spectrometer. 13C CP/MAS NMR experiments were
performed on Agilent 600 DD2 spectrometer at a resonance
frequency of 150.15 MHz. 13C NMR spectra were recorded on
a spinning rate of 15 kHz with a 4 mm probe at room temper-
ature. 13C CP/MAS experiments were performed with a delay
time of 5 s and a contact time of 1 ms. Infrared spectra were
obtained in the 400–4000 cmꢁ1 range using a Bruker ALPHA FT-
IR spectrometer. Powder X-ray diffraction (PXRD) measure-
ments were performed at 293 K on a D8 ADVANCE diffractom-
A mixture of 4-iodo-2,6-diisopropylbenzenamine (3.7 g, 14
mmol), butane-2,3-dione (0.603 mL, 7 mmol) and 0.5 mL formic
acid in 15 mL methanol was charged in 50 mL Schlenk ask.
Aer stirred at room temperature for 6 h, the precipitate was
ltered and recrystallized from ethanol to afford A as a bright
1
yellow solid (4.4 g, 81%). H NMR (400 MHz, CDCl3) d 7.46 (s,
2H), 2.63 (m, 2H), 2.07 (s, 3H), 1.18 (d, 12H); 13C NMR (400 MHz,
CDCl3) d 168.5 (2c), 145.8 (2c), 137.8 (2c), 137.8 (2c), 132.3 (4c),
88.3 (2c), 28.5 (2c), 22.8 (8c), 22.5 (4c), 16.7 (2c). IR(KBr):
3486(w), 3403(w), 2961(vs), 2870(m), 1648(s), 1570(w), 1460(s),
1438(s),1384(w), 1364(s), 1324(m), 1242(s), 1186(s), 1126(s),
1072(w), 937(m), 883(w), 864(w), 819(w), 792(m), 711(m), 638(w),
559(w), 539(w), 467(w). HRMS (ESI-TOF) calcd for C28H39I2N2
([M + H]+), m/z 658.1191; found, m/z 658.1206.
˚
eter (Cu Ka, l ¼ 1.5406 A). ICP analysis was performed on an
IRIS InterpidII XSP and NU AttoM. XPS spectra were obtained
from PHI Versaprobe II. Thermogravimetric analyses were
carried out on a TA Instrument Q5 simultaneous TGA under
owing nitrogen at a heating rate of 10ꢀC minꢁ1. HRTEM (high
resolution transmission electron microscopy) analysis was
performed on a JEOL 2100 Electron Microscope at an operating
voltage of 200 kV. The scanning electron microscopy (SEM)
micrographs were recorded on a Gemini Zeiss Supra TM scan-
ning electron microscope equipped with energy-dispersive X-ray
detector (EDX). The elemental analysis was conducted on
a PerkinElmer Model 2400 analyzer. The crystal data were ob-
tained by Agilent SuperNova X-ray single crystal diffractometer.
Synthesis of B30,31
A mixture of A (1.1 mmol, 0.722 g) and DME(NiBr2)32 (1 mmol,
0.308 g) in 50 mL dry dichloromethane was charged in a 100 mL
Schlenk ask. Aer stirred at room temperature for 2 day in N2,
the reaction system was ltered though a pad of Celite. The
resulting solids were further washed with anhydrous diethyl
ether, and then dried in vacuo to afford complex B as brick-red
solid (0.59 g, 68.0%). IR(KBr): 3439(s), 3326(s), 2965(s), 2929(m),
2868(w), 1636(w), 1567(m), 1462(m), 1441(m), 1408(w), 1382(m),
1364(w), 1346(w), 1323(m), 1306(w), 1256(w), 1240(w), 1207(s),
Synthesis of A29
A mixture of 2,6-diisopropylbenzenamine (2.54 g, 14.3 mmol) 1168(w), 1153(w), 1069(w), 1006(w), 985(w), 940(w), 887(w),
and I2 (4 g, 15.7 mmol) was charged in 50 mL round-bottom 863(m), 791(m), 742(w), 636(w), 554(w), 480(w). Anal. calcd: for
20270 | RSC Adv., 2019, 9, 20266–20272
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C28H38Br2I2NiN2, C 37.92, H 4.61, N 3.17, Br 17.31. I 30.4%, Ni construction of many more new metalated POP-based hetero-
6.6% (I and Ni wt% were determined by ICP measurement).
geneous catalytic materials for various organic transformations.
Synthesis of Ni(II)-a-diimine-POP
Conflicts of interest
A mixture of the compound B (0.5 mmol, 0.488 g), 1,3,5-trie-
thynylbenzene (0.5 mmol, 75 mg), Pd(PPh3)4 (0.25 mmol, 30
mg), CuI (0.1 mmol, 20 mg) and triethylamine (25 mL) in 50 mL
toluene was heated at 80 ꢀC for 72 h in N2. Aer cooled to room
temperature, the obtained crude product was completely
washed with water (30 mL), ethanol (30 mL) and dichloro-
methane (30 mL) respectively. The resulted solids were further
Soxhlet extracted with mixed solution of dichloromethane,
methanol and acetone (50 mL: 50 mL: 50 mL) and then dried at
110 ꢀC in vacuo to afford Ni(II)-a-diimine-POP as dark gray solids
(0.31 g, 86.4%). IR(KBr): 3390(s), 3030(w), 2924(vs), 2852(s),
2041(w), 1705(s), 1595(m), 1518(w), 1492(m), 1463(s), 1377(m),
1225(m), 1085(m), 1015(m), 830(m), 749(w), 616(w). Anal. calcd:
C 58.2, H 4.93, N 3.11, Br 19.62. I 5.67%, Ni 7.6% (I and Ni wt%
were determined by ICP measurement).
There are no conicts to declare.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (21671122, 21475078, 21802091), Taishan
scholar’s construction project.
Notes and references
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General procedure for the Suzuki–Miyaura cross-coupling
reaction between iodobenzene and arylboronic acid
A mixture of iodobenzene (1.0 mmol, 116 mL), phenylboronic
acid (1.1 mmol, 0.134 g), K3PO4$3H2O (2 mmol, 0.533 g) and
Ni(II)-a-diimine-POP (52 mg) in 2 mL toluene was stirred at
100 ꢀC for 8 or 12 h in N2 to afford the corresponding product.
Yield was determined by the GC analysis.
General procedure for the Suzuki–Miyaura cross-coupling
reaction between bromobenzene and arylboronic acid
A mixture of bromobenzene (1.0 mmol, 104 mL), phenylboronic
acid (1.1 mmol, 0.134 g), K3PO4$3H2O (2 mmol, 0.533 g) and
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100 ꢀC for 8 h or 12 h in N2 to afford the corresponding product.
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centrifugation, washed with toluene (3 ꢂ 2 mL), acetonitrile (3
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ꢂ 2 mL) and dried at 110 C for 12 h in vacuum and then was
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In summary, we report herein a new Ni(II)-a-diimine decorated
porous organic polymer Ni(II)-a-diimine-POP by assembly of
metallo-building block and its polymerized partner via in situ
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