Development of dipyridine-based coordinative polymers for reusable heterogeneous catalysts

Article abstract of DOI:10.1002/jccs.201900191

Poly(di(pyridin-2-yl)methyl acrylate) (PDPyMA), which was obtained by the free radical polymerization of designed coordinative monomer of di(pyridin-2-yl)methyl acrylate, is able to coordinate with various metal ions to form heterogeneous catalysts for diverse catalytic reactions. The Pd and Cu complexes supported by PDPyMA were developed for the heterogeneous Suzuki-Miyaura reaction and Friedel-Crafts alkylation, respectively. The PDPyMA-based catalysts showed no significant decline of reactivity after five times recycling. However, the hydrolysis of the PDPyMA backbone under alkaline conditions limited the catalytic efficiency of this heterogeneous catalyst so that the coordinative monomer was redesigned as 1,1-di(pyridine-2-yl)-2-(4-vinylphenyl)ethan-1-ol and then 2,2′-(1-methoxy-2-(4-vinylphenyl)ethane-1,1-diyl)dipyridine (MVPhDPy). With copolymerization of N-isopropyl acrylamide (NIPAM), the efficiency of polymer-based heterogeneous catalysts could be further raised, demonstrated by the increased turn over number in the Suzuki-Miyaura reaction, which approached 5,260 by using the catalyst formed from poly(MVPhDPy-co-NIPAM) and Pd(OAc)₂. poly(MVPhDPy-co-NIPAM) copolymer, therefore, could be a versatile platform to support different metal ions for various heterogeneous catalytic reactions.

Full text of DOI:10.1002/jccs.201900191

Received: 10 May 2019
Revised: 18 June 2019
Accepted: 26 June 2019
DOI: 10.1002/jccs.201900191
S P E C I A L I S S U E P A P E R
Development of dipyridine-based coordinative polymers
for reusable heterogeneous catalysts
1
1
1
1
Hsiang-Chun Chang | Jia-Qi Li | Ching-Kai Lin | Yu-Jung Hsu
|
1
1
1
2
Tsung-Han Tu | Yi-Liang Hsieh | Hsiu-Hao Hsu | Gene-Hsiang Lee
|
2
1
Yi-Hung Liu | Chi-How Peng
1
Department of Chemistry and Frontier
Abstract
Research Center on Fundamental and
Applied Sciences of Matters, National Tsing
Hua University, Hsinchu, Taiwan
Poly(di(pyridin-2-yl)methyl acrylate) (PDPyMA), which was obtained by the free
radical polymerization of designed coordinative monomer of di(pyridin-2-yl)
methyl acrylate, is able to coordinate with various metal ions to form heteroge-
neous catalysts for diverse catalytic reactions. The Pd and Cu complexes supported
by PDPyMA were developed for the heterogeneous Suzuki-Miyaura reaction and
Friedel-Crafts alkylation, respectively. The PDPyMA-based catalysts showed no
significant decline of reactivity after five times recycling. However, the hydrolysis
of the PDPyMA backbone under alkaline conditions limited the catalytic efficiency
of this heterogeneous catalyst so that the coordinative monomer was redesigned
2
Instrumentation Center, National Taiwan
University, Taipei, Taiwan
Correspondence
Chi-How Peng, Department of Chemistry
and Frontier Research Center on
Fundamental and Applied Sciences of
Matters, National Tsing Hua University,
Hsinchu, 30013, Taiwan.
Email: chpeng@mx.nthu.edu.tw
0
as 1,1-di(pyridine-2-yl)-2-(4-vinylphenyl)ethan-1-ol and then 2,2 -(1-methoxy-
Funding information
Ministry of Science and Technology,
Taiwan, Grant/Award Number: MOST
2-(4-vinylphenyl)ethane-1,1-diyl)dipyridine (MVPhDPy). With copolymerization
of N-isopropyl acrylamide (NIPAM), the efficiency of polymer-based heteroge-
neous catalysts could be further raised, demonstrated by the increased turn over
number in the Suzuki-Miyaura reaction, which approached 5,260 by using the cata-
1
07-2113-M-007-014
lyst formed from poly(MVPhDPy-co-NIPAM) and Pd(OAc) . poly(MVPhDPy-co-
2
NIPAM) copolymer, therefore, could be a versatile platform to support different
metal ions for various heterogeneous catalytic reactions.
K E Y W O R D S
coordinative polymer, heterogeneous catalyst, reusable catalyst
1
| INTRODUCTION
systems, there are still some challenges such as low catalytic
efficiency and gradually declined activity after reuse.
[
22–24]
Development of reusable heterogeneous catalysts is one of
the most important subjects in organic synthesis and organo-
metallic catalysis due to the economic and environmental
The coordinating site of the substrates is another issue that
limits the application of these heterogeneous catalysts
because many valuable reactions can only be mediated by
the organometallic complexes with unique ligands. Herein, a
series of coordinative monomers were designed for the poly-
meric backbone that can bind to the metal ions (Scheme 1).
The polymeric palladium and copper complexes coordinated
by poly(di(pyridin-2-yl)methyl acrylate) (PDPyMA) were
[
1–12]
concerns.
als or particles,
crosslinked polymers
Different substrates such as porous materi-
[
13,14]
[15,16]
metal–organic-frameworks,
and
[
17–21]
have been used to carry metal
ions or particles as solid catalysts for the mediation of vari-
ous reactions. However, compared with homogeneous
©
2019 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J Chin Chem Soc. 2019;1–15.
http://www.jccs.wiley-vch.de
1

2
CHANG ET AL.
capable of catalyzing the Suzuki-Miyaura reaction and
Friedel-Crafts alkylation, respectively, without significant
decline in reactivity after five times recycling. 1,1-di(pyri-
dine-2-yl)-2-(4-vinylphenyl)ethan-1-ol (DPyVPhE) was then
synthesized to avoid the hydrolysis of ester bond in
di(pyridin-2-yl)methyl acrylate (DPyMA) and thus increased
the turn over number (TON) in the Suzuki-Miyaura reaction
from 26 to 62. The TON in the Suzuki-Miyaura reaction cat-
alyzed by the polymeric palladium complex could be further
improved to 136 by using the copolymer of DPyVPhE and
conditions and thus the heterogeneous catalyst based on the
copolymer of MVPhDPy and NIPAM could catalyze the
Suzuki-Miyaura reaction without a significant decrease in
activity after five times recycling and approached the TON
of 5,260. These coordinative polymers could be a versatile
platform to carry different metal ions for the heterogeneous
catalysis of varied reactions.
2
2
| RESULTS AND DISCUSSION
.1 | Synthesis and characterization of
N-isopropyl acrylamide (NIPAM) as the polymer backbone.
0
2
,2 -(1-methoxy-2-(4-vinylphenyl)ethane-1,1-diyl)dipyridine
DPyMA, PDPyMA, and their metal complexes
(MVPhDPy), which was obtained from the methylation of
The synthetic steps of PDPyMA-based heterogeneous cata-
lysts are shown in Scheme 2. The di(pyridin-2-yl)methyl
DPyVPhE, showed a higher stability under various reaction
[
25]
acrylate
was obtained as a yellowish liquid from the acet-
ylation of dipyridinyl methanol, which was prepared from
a halogen-metal exchange of 2-bromopyridine and
n-butyllithium followed by nucleophilic addition to the alde-
hyde. Crystal structure of the complex of DPyMA and
CuBr indicated that DPyMA could coordinate to the metal
2
ion by pyridinyl groups with the formula of [(DPyMA)CuBr
(
μ-Br)] (Figure 1), in which the copper atoms locate in a
2
square pyramidal environment. The nitrogen atoms of pyri-
dinyl groups are at the square base and coordinate to copper
centers with an average Cu-N bond length equal to
[
26]
2
.03 Å.
The DPyMA and copper formed a six-
membered ring with the boat conformation. The bromides
at square base coordinate to the copper center as a regular
[
26,27]
Cu(II)-Br bond with bond lengths around 2.41 Å.
However, the bridged bromides at the apex position show a
bond length larger than 3.00 Å, indicating a weak coordina-
tion. Free radical polymerization of DPyMA initiated by
azobisisobutyronitrile (AIBN) in Dimethylformamide
ꢀ
(
DMF) at 60 C gave PDPyMA, which was characterized by
1
gel permeation chromatography (GPC) and the H NMR
spectrum (Figure 2). A representative PDPyMA product was
SCHEME 1 The evolution of heterogeneous catalysts based on
coordinative polymers in this study
a
yellow powder with molecular weight equal to
SC HEME 2 Synthetic steps of
DPyMA, poly(di(pyridin-2-yl)methyl
acrylate) (PDPyMA), and their metal
complexes

CHANG ET AL.
3
2
3,400 g/mol and Đ value equal to 1.80 (Figure 2b). The
to the combination of polar metal center and nonpolar poly-
mer chain or the formation of a polymer network architec-
ture cross-linked via metal ions. The yellow powder formed
reaction of PDPyMA and metal salts in dichloromethane at
room temperature provided insoluble powders that could
hardly be dissolved in CH Cl , EtOAc, MeOH, and H O
2+
from PDPyMA and Pd(OAc)
(Catalyst 1a), and the pale blue powder formed from
with 138.8 ppm of Pd
2
2
2
2
(
[
Figure S5–S6). According to the single-crystal structure of
(DPyMA)CuBr(μ-Br)] , the insolubility could be attributed
2+
PDPyMA and Cu(OTf)
b) were used as the heterogeneous catalysts for the Suzuki-
Miyaura reaction and Friedel-Crafts alkylation, respectively.
with 76.7 ppm of Cu (Catalyst
2
2
1
2
.2 | Suzuki-Miyaura reaction catalyzed by
PDPyMA-Pd(OAc)2
[
28–32]
Suzuki-Miyaura reaction
is one of the most versatile
and well-developed methods in organic synthesis for
carbon–carbon bond formation using palladium complexes
and thus was selected to evaluate the performance of hetero-
geneous catalyst of PDPyMA-Pd(OAc)2 (Table 1). The
coupling reaction of 4-tolyboronic acid and bromobenzene
ꢀ
[33,34]
in o-xylene at 90 C
was applied to optimize the cata-
lyst loading. The yield reached 70% within 4 hr when 0.02 g
of PDPyMA-Pd(OAc) was used in the reaction and could
2
be improved to 94% by increasing the loading of Catalyst 1a
to 0.10 g (Table 1, Entries 1 and 2). The reuse of Catalyst 1a
for another four times showed almost no difference in the
yield and the palladium leakage in the solution detected by
inductively coupled plasma atomic emission spectroscopy
(ICP-AES) was around 0.004 mg in average, which was
equal to 0.029%. The same reaction was also catalyzed by
2
FIGURE 1 Crystal structure of [(DPyMA)CuBr(μ-Br)] depicted
with ellipsoids at the 50% probability. Selected bond lengths (Å) and
ꢀ
angles ( ) for [(DPyMA)CuBr(μ-Br)]
2
: Cu(1)-N(1) 2.031(5), Cu(1)-N
(
(
(
2) 2.037(5), Cu(1)-Br(2) 2.3936(10), Cu(1)-Br(1) 2.4306(9), Cu(1)-Br
3) 3.0736(12), Cu(2)-N(3) 2.023(5), Cu(2)-N(4) 2.058(5), Cu(2)-Br
3) 2.4128(9), Cu(2)-Br(4) 2.4360(10), Cu(2)-Br(1) 3.0152(12), C(13)-
C(14) 1.329(10), C(27)-C(28) 1.327(10), N(1)-Cu(1)-N(2) 86.0(2), N
1)-Cu(1)-Br(2) 89.67(15), N(2)-Cu(1)-Br(2) 160.97(16), N(1)-Cu(1)-
Br(1) 175.68(17), N(2)-Cu(1)-Br(1) 93.05(14), Br(2)-Cu(1)-Br
1) 92.59(3), N(1)-Cu(1)-Br(3) 90.18(16), N(2)-Cu(1)-Br(3) 91.36(16),
the monomeric complex of DPyMA-Pd(OAc) to give a
2
(
9
9% yield with a lower TON (Table 1, Entry 3), which
implied that the polymeric structure and heterogeneity of
(
PDPyMA-Pd(OAc) did not damage the activity of individ-
2
Br(2)-Cu(1)-Br(3) 107.18(4), Br(1)-Cu(1)-Br(3) 85.64(3), N(3)-Cu(2)-
N(4) 85.3(2), N(3)-Cu(2)-Br(3) 175.41(15), N(4)-Cu(2)-Br(3) 90.33
ual palladium center. The electron-withdrawing group such
as ─NO on the reactant was expected to promote the reac-
tion to a higher yield and thus a better TON number.
Indeed, the yield of the Suzuki-Miyaura reaction catalyzed
(
14), N(3)-Cu(2)-Br(4) 88.12(15), N(4)-Cu(2)-Br(4) 161.23(17), Br(3)-
Cu(2)-Br(4) 95.63(3), N(3)-Cu(2)-Br(1) 94.69(16), N(4)-Cu(2)-Br
1) 98.07(16), Br(3)-Cu(2)-Br(1) 87.27(3), Br(4)-Cu(2)-Br(1) 99.97(3),
2
[
35–38]
(
Cu(1)-Br(1)-Cu(2) 94.09(3), and Cu(2)-Br(3)-Cu(1) 93.00(3)
by PDPyMA-Pd(OAc) approached 99% within 4 hr with a
2
1
FIGURE 2 (a) H NMR (CDCl
3
,
4
00 MHz) spectrum and (b) GPC trace of
the representative poly(di(pyridin-2-yl)
n
methyl acrylate). M = 23,400 g/mol
and Đ = 1.80

4
CHANG ET AL.
TABLE 1 Suzuki-Miyaura reactions
of different bromo-benzene and
4
-tolyboronic acid mediated by
a
Catalyst 1a
b
R = ─H, Yield, Pd leakage : first cycle: 99%, 0.014%. Fourth cycle: 99%, 0.014%
Second cycle: 99%, 0.058%. fifth cycle: 92%, 0.029%
Third cycle: 99%, 0.029%
R = ─NO , Yield, Pd leakage: first cycle: 99%, 0.036%. Fourth cycle: 99%, 0.036%
2
Second cycle: 99%, 0.036%. Fifth cycle: 92%, 0.05%
Third cycle: 99%, 0.043%
R = ─OMe, Yield, Pd leakage: first cycle: 70%, 0.086%. Fourth cycle: 75%, 0.086%
Second cycle: 70%, 0.065%. Fifth cycle: 68%, 0.094%
Third cycle: 65%, 0.086%
c
d
e
TOF (h−1
6.5
Entry
R
Loading (g)
Yield (%)
TON
26
)
1
2
H
0.02
0.1
0.1
0.1
0.1
70
94
99
99
70
H
7.3
4.6
7.6
5.3
1.8
f
3
H
1.2
4
5
NO
2
1.9
OMe
1.3
a
Conditions: R-bromobenzene (1.00 mmol), 4-tolyboronic acid (1.5 mmol), PDPyMA-Pd(OAc)
2
(0.10 g,
ꢀ
1
3.88 mg Pd on the polymer), K
2
CO
3
(0.28 g, 1.95 mmol), o-xylene (2 mL), 90 C, 4 hr.
b
Metal leakage was determined by ICP-AES.
The quantity of the catalyst.
c
d
1
The yield was calculated by the H NMR spectrum with the internal standard of mesitylene.
e
Turnover number (TON) was determined from the quantity of product and catalyst.
f
2
Using DPyMA-Pd(OAc) as a catalyst.
TON equal to 7.6 when 1-bromo-4-nitrobenzene was used
as the reactant (Table 1, Entry 4). The activity of Catalyst 1a
showed no observable difference after five times recycling
with an average loss of palladium as 0.009 mg (0.065%). On
the other hand, when bromobenzene had an electron-
donating group like ─OMe, the catalytic efficiency in the
Suzuki-Miyaura reaction would be decreased as shown by
the declined yield of 70% in the coupling reaction of
raised from 0 to 80% as the PDPyMA-Cu(OTf)2 was
increased from 0.02 to 0.50 g (Table 2, Entries 1–3). Cata-
lyst 1b was then recycled by filtration and then reused to
mediate the reaction for another four times, which showed a
constant yield around 80% and the average metal leakage as
0.024 mg that was equal to 0.063% loss of copper species.
The reaction catalyzed by the monomeric complex of
DPyMA-Cu(OTf) , which was performed as a control study,
2
4
-bromoanisole and 4-tolyboronic acid catalyzed by
reached 99% yield but showed a lower TON (Table 2, Entry
4), implying that the transformation from homogeneous to
heterogeneous catalysis of Friedel-Crafts alkylation using
PDPyMA platform does not significantly affect the catalytic
activity. These results demonstrated that PDPyMA can be a
multifunctional matrix to carry various metal ions for the
catalysis of different reactions.
PDPyMA-Pd(OAc) (Table 1, Entry 5).
2
2
.3 | Friedel-Crafts alkylation catalyzed
by PDPyMA-Cu(OTf)2
Friedel-Crafts alkylation is another well-known organic
reaction mediated by Lewis acid catalysts for the formation
of carbon–carbon bonds.
catalyst of PDPyMA-Cu(OTf) was applied to mediate the
Friedel-Crafts reaction of indol and methyl 3,3,3-
trifluoropyruvate in ether at 0 C for 20 hr to demonstrate
that PDPyMA could be a platform carrying different metal
ions to catalyze the corresponding reactions. The yield was
[39–42]
Therefore, the heterogeneous
2
.4 | Synthesis of DPyVPhE and its palladium
2
complex
ꢀ
A common strategy to improve the catalytic efficiency of a
Suzuki-Miyaura reaction was the addition of strong base,
which causes the hydrolysis of the ester bond in DPyMA.

CHANG ET AL.
5
TABLE 2 Friedel-Craft alkylation of
indole and methyl 3,3,3-trifluoropyruvate
a
mediated by Catalyst 1b
b
Yield, Pd leakage : First cycle: 80%, 0.097%. Fourth cycle: 81%,
.037%
0
Second cycle: 82%, 0.052%. Fifth cycle: 80%, 0086%
Third cycle: 80%, 0.044%
c
d
e
TOF (h−1
0
Entry
Loading (g)
0.02
Yield (%)
TON
0
)
1
2
3
0
50
80
99
0.30
1.4
1.3
0.7
0.07
0.50
0.065
0.035
f
4
0.50
a
Conditions: Indole (0.55 mmol), methyl 3,3,3-trifluoropyruvate (50 μL, 0.5 mmol), Et
2
O (2 mL), PDPyMA-Cu
ꢀ
(
OTf)
2
(0.5 g, 38.25 mg Cu on the polymer), 0 C, 20 hr.
b
Metal leakage was determined by ICP-AES.
c
The quantity of the catalyst.
d
1
The yield is calculated by the H NMR spectrum.
e
f
Turnover number (TON) was determined from the quantity of product and catalyst.
Using DPyMA-Cu(OTf) as a catalyst.
2
SCHEME 3 The synthetic process of the coordinative monomers
0
of 1,1-di(pyridine-2-yl)-2-(4-vinylphenyl)Ethan-1-ol and 2,2 -
(([4-vinylbenzyl]oxy)methylene)dipyridine (4-VBMDPy)
FIGURE 3 ORTEP diagram of DPyVPhE depicted with
ellipsoids at the 50% probability. Selected bond lengths (Å) and angles
ꢀ
Therefore, we redesigned the monomer by replacing the
ester group using the benzyloxide group and targeted to the
( ) for DPyVPhE: O(1)-C(1) 1.411(3), N(1)-C(11) 1.322(5), N(1)-C
(15) 1.341(5), N(2)-C(20) 1.333(5), N(2)-C(16) 1.335(4), C(9)-C
(10) 1.234(7), C(11)-N(1)-C(15) 118.4(3), C(20)-N(2)-C(16) 117.3(3),
O(1)-C(1)-C(16) 109.2(2), O(1)-C(1)-C(11) 108.9(2), O(1)-C(1)-C
0
new monomer of 2,2 -(((4-vinylbenzyl)oxy)methylene)
[43]
dipyridine (4-VBMDPy).
dipyridinyl methanol and 4-vinylbenzyl chloride generated
-VBMDPy as the minor product but DPyVPhE as the
However, the reaction of
(
(
(
2) 108.3(2), N(1)-C(11)-C(12) 122.8(3), N(1)-C(11)-C(1) 114.4(3), N
1)-C(15)-C(14) 123.0(4), N(2)-C(16)-C(17) 122.6(3), N(2)-C(16)-C
1) 115.8(3), and N(2)-C(20)-C(19) 124.1(3)
4
major product (Scheme 3), which was rarely reported. The
structure of the major product was further confirmed by X-
ray crystallography (Figure 3). The ORTEP diagram clearly
showed that the new coordinative monomer has a vinyl
group and two pyridines linked by a 2-phenylethan-1-ol seg-
ment. To rationalize this unexpected result, a series of reac-
tions using benzyl halide and varied methanol derivatives as
the model compounds were performed (Table 3).
4-VBMDPy should be synthesized via the O-alkylation
pathway and DPyVPhE was obtained via the C-alkylation
pathway. Given by the reactions with various methanol
derivatives, it was realized that two 2-pyridine groups were
required for the generation of DPyVPhE (Table 3, Entries
1–5). When there was only 0.5 equivalent of NaH, the

6
CHANG ET AL.
TABLE 3 Summary of various conditions and results for the synthesis of DPyVPhE and 4-VBMDPy
ꢀ
Entry
R
1
R
2
R
3
Base (equiv.)
NaH (1.2)
NaH (1.2)
NaH (1.2)
NaH (1.2)
NaH (1.2)
NaH (0.5)
NaH (0.9)
NaH (1.6)
NaH (2.2)
NaH (1.6)
NaH (1.6)
T ( C)
25
Conv. Of O-alkylation (%)
Conv. Of C-alkylation (%)
1
2
3
4
5
6
7
8
9
2-Pyridine
Phenyl
2-Pyridine
Phenyl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Br
I
15
60
20
41
42
21
22
10
—
54
30
—
5
77
—
—
—
—
18
62
83
92
32
2
25
3-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
3-Pyridine
Phenyl
25
25
H
25
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
2-Pyridine
25
25
25
25
10
11
12
13
14
15
16
17
25
25
a
Cl
Cl
Cl
Cl
Cl
Cl
LDA (1.2)
25
—
47
49
—
—
78
t-BuOK (1.2)
25
b
TMS
2
NNa (1.2)
25
5
c
TEA (1.2)
NaH (1.2)
NaH (1.2)
25
—
—
—
−20
60
a
Lithium diisopropylamide.
Sodium bis(trimethylsilyl)amide.
b
c
Triethylamine.
ꢀ
conversion of O-alkylation and C-alkylation pathways were
comparable but the total conversion was low (Table 3, Entry
that at 25 C (Table 3, Entry 17). Because the organic synthe-
sis and mechanism are not the main concern in this study
and the optimized conditions for the generation of
4-VBMDPy may not be achieved within a predictable time
period, DPyVPhE, which is also a vinyl monomer that can
coordinate to metal ions, was used in the following study.
6). The increase of NaH raised the efficiency of C-alkylation
as well as the total conversion (Table 3, Entries 7 and 8).
The product of C-alkylation became the only product with
92% conversion when 2.2 equivalent of NaH was added
(Table 3, Entry 9). The O-alkylation could dominate the
The complex of DPyVPhE-Pd(OAc)
was then synthe-
2
reaction when benzyl bromide or benzyl iodide was used,
however, the total conversion decreased (Table 3, Entries
sized and characterized using X-ray crystallography to rec-
2+
ognize the possible coordination of PDPyVPhE to Pd ions
(Figure 4). DPyVPhE-Pd(OAc) was found to be a triclinic
10 and 11). Changing the base only lowered the total con-
2
version but could not reverse the majority from C-alkylation
to O-alkylation (Table 3, Entries 12–14). The temperature
did not affect the reaction pathway significantly. When the
temperature was too low, reaction does not occur (Table 3,
Entry 16), but when the temperature increased to 60 C, C-
alkylation is the only pathway with comparable conversion to
crystal with the P-1 space group (Table S1). The palladium
center was coordinated by two pyridines of DPyVPhE and
two acetate groups to form a square planar configuration.
The bond lengths of Pd-N and Pd-O are 2.007 and 2.016 Å,
respectively, which matched the range reported in the litera-
ꢀ
[
44,45]
ture.
This square planar N, N, O, O coordinated

CHANG ET AL.
7
SCHEME 4 Synthetic steps of
PDPyVPhE-Pd(OAc) (Catalyst 2)
2
TABLE 4 Suzuki-Miyaura reaction
catalyzed by heterogeneous catalyst of
2
PDPyVPhE-Pd(OAc) with different
a
bases in varied solvents
b
c
TOF (h−1
)
Entry
X
R
Solvent
o-Xylene
DMF
Base
Yield (%)
TON
50
1
2
Br
Br
Br
Br
Br
Br
Br
Br
I
H
K
2
K
2
K
2
K
2
CO
CO
CO
CO
3
3
3
3
78
28
76
64
96
89
99
99
89
13
5
H
18
d
3
H
H
2
O
49
12
10
15
15
16
16
58
4
5
6
7
8
H
Toluene
41
H
o-Xylene
o-Xylene
o-Xylene
o-Xylene
o-Xylene
KOH
KOH
KOH
KOH
KOH
62
OMe
CN
58
64
NO
H
2
64
e
9
116
a
Conditions: bromobenzene (1 mmol), 4-tolylboronic acid (1.5 mmol), base (0.95 mmol), solvent (2 mL), Catalyst
ꢀ
2
(1.6 mol%), 90 C, 4 hr.
b
1
The yield was calculated by the H NMR spectrum with the internal standard of mesitylene.
Turnover number (TON) was determined from the quantity of product and catalyst.
c
d
e
TBAB (2 mmol).
Catalyst 2 (0.77 mol%), 2 hr.
configuration of DPyVPhE-Pd(OAc)2 provides a suitable
environment for the catalysis of the Suzuki-Miyaura
reaction.
per polymer chain). This heterogeneous catalyst was then
used to mediate the Suzuki-Miyaura reaction of
4-tolyboronic acid and bromobenzene with different bases in
varied solvents. The reaction in o-xylene using potassium
hydroxide (KOH) as the base demonstrated the highest yield
as 96% as well as the highest TON as 63 compared to the
values of reactions in DMF, H O, and toluene using K CO
3
[
46]
2
.5 | Suzuki-Miyaura reaction catalyzed by
PDPyVPhE-based palladium complexes
2
2
The synthetic steps of PDPyVPhE-Pd(OAc) (Catalyst 2)
as the base (Table 4, Entries 1–5). The electron-donating
substituent on bromobenzene led to a lower catalytic effi-
ciency (Table 4, Entry 6) and reversely, the electron-
withdrawing group raised the conversion and TON of the
2
are similar to that of PDPyMA-Pd(OAc) . PDPyVPhE
2
(
M = 69,200 g/mol, Đ = 4.3), which was obtained from the
n
free radical polymerization of DPyVPhE initiated by AIBN
ꢀ
in toluene at 60 C for 48 hr, was reacted with Pd(OAc) in
reaction (Table 4, Entries 7 and 8), which matched the trend
2
ꢀ
[35–38]
CH Cl at 25 C for 2 hr to obtain the orange powder of het-
reported in the literature.
The TON could approach a
2
2
erogeneous catalyst of PDPyVPhE-Pd(OAc) (Scheme 4).
The palladium content of Catalyst 2 was measured by ICP-
AES as 17.0% (wt/wt) (1.70 mg, 2 monomer per Pd, 111 Pd
higher value of 116 in the reaction of 4-tolyboronic acid and
iodobenzene with a shorter reaction time (Table 4, Entry
2
[
47,48]
9).
However, the leakage of Pd species was significant

8
CHANG ET AL.
during the recycling process and thus we tried to improve
Catalyst 2 by the modification of the polymer backbone.
The addition of NIPAM into the polymer backbone was
reported to be able to improve the reactivity of polymer-
catalyst (Catalyst 3). The palladium content of Catalyst
3 was also measured using ICP-AES as 8.1% (0.81 mg,
DPyVPhE/Pd = 1.4, 66 Pd per polymer chain). Compared to
Catalyst 2, the palladium content was decreased but the
DPyVPhE/Pd ratio was increased, which was a more eco-
nomical way for the utilization of coordinative monomer.
The condition of the Suzuki-Miyaura reaction of
4-tolyboronic acid and bromobenzene catalyzed by Catalyst
3 was also optimized by verifying the solvent and base
(Table 5, Entries 1–7). Similar to Catalyst 2, Catalyst
3 showed the highest catalytic activity as the TON equal to
136 when the reaction was performed using KOH as a base
[49,50]
based heterogeneous catalyst
so that free radical copo-
lymerization of DPyVPhE and NIPAM was performed
under the condition of (AIBN) /(DPyVPhE) /(NIPAM)
0
0
0
ꢀ
=
1/3.3/6.7 in toluene at 60 C for 48 hr (Scheme 5). The
copolymer (M = 86,300 g/mol, Đ = 1.6), which was char-
n
1
acterized by GPC and H NMR to confirm the coexistence
of DPyVPhE and NIPAM (Figure S3), was then mixed with
Pd(OAc) to form a new DPyVPhE-based heterogeneous
2
SC HEME 5 Synthetic steps of
poly(DPyVPhE-co-NIPAM)-Pd(OAc)
Catalyst 3)
2
(
TABLE 5 Suzuki-Miyaura reaction
catalyzed by Catalyst 3 with varied
a
solvents and bases
R = ─H, X = ─Br, Yield: First cycle: 99%
Second cycle: 86%
Third cycle: 64%
b
c
TOF (h−1
)
Entry
X
R
Solvent
o-Xylene
DMF
Base
Yield (%)
72
TON
95
1
2
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
I
H
K
K
K
K
2
CO
2
CO
2
CO
2
CO
3
3
3
3
24
19
14
21
34
4
H
56
74
d
3
H
H
2
O
42
55
4
5
6
7
8
9
H
Toluene
64
85
H
o-Xylene
o-Xylene
o-Xylene
o-Xylene
o-Xylene
o-Xylene
o-Xylene
KOH
Na CO
PO
99
136
16
H
2
3
12
NO
2
K
3
4
30
40
10
34
34
34
68
OMe
CN
KOH
KOH
KOH
KOH
99
136
136
136
136
99
1
0
1
NO
H
2
99
e
1
99
a
Conditions: bromobenzene (1 mmol), 4-tolylboronic acid (1.5 mmol), K
2
CO
3
(0.95 mmol), solvent (2 mL),
ꢀ
Catalyst 3 (0.76 mol%), 90 C, 4 hr.
b
1
The yield was calculated by the H NMR spectrum with the internal standard of mesitylene.
c
Turnover number (TON) was determined from the quantity of product and catalyst.
d
TBAB (2 mmol).
hr.
e
2

CHANG ET AL.
9
in o-xylene (Table 5, Entry 5). However, the TON of Cata-
lyst 3 for Suzuki-Miyaura reaction should be higher because
the different substituents on bromobenzene did not affect the
TON values of reactions mediated by Catalyst 3 (Table 5,
Entries 8–10), and the reaction of 4-tolyboronic acid and
iodobenzene also showed a TON value of 136 but the con-
version approached 99% with a shorter time of 2 hr (Table 5,
Entry 11) Nevertheless, the decreased yield with recycling
times indicated that the Catalyst 3 was lost during the
recycling test. Therefore, we decided to design the next
coordinative monomer rather than identify the highest TON
of Catalyst 3 or measure the Pd leakage (Figure 4).
MVPhDPy and NIPAM with the condition of (AIBN) /
0
ꢀ
(MVPhDPy) /(NIPAM) = 1/1.6/8.2 in toluene at 60 C for
0
0
48 hr (Scheme 7). The polymeric product was characterized
1
by GPC (M = 6,300 g/mL, Ð = 5.22) as well as H NMR
n
(Figure 6) and then reacted with Pd(OAc)2 to form the
brown powder of heterogeneous catalyst of poly
(MVPhDPy-co-NIPAM)-Pd(OAc) (Catalyst 4). The palla-
2
dium content of Catalyst 4 was also measured by ICP-AES
to be 10.2% (0.51 mg, MVPhDPy /Pd = 2.7, 6 Pd per poly-
mer chain).
The heterogeneous catalyst of poly(MVPhDPy-co-
NIPAM)-Pd(OAc) was then used to mediate the Suzuki-
2
Miyaura reaction of 4-tolyboronic acid and bromobenzene
derivatives with different bases in o-xylene for the optimized
conditions (Table 6). Five bases were used and the reaction
with Cs CO showed the highest yield as 99%, followed by
2
.6 | Suzuki-Miyaura reaction catalyzed by
poly(MVPhDPy-co-NIPAM)-Pd(OAc)
2
2
3
The loss of poly(DPyVPhE-co-NIPAM)-Pd(OAc)2 was
attributed to the hydroxyl group on DPyVPhE and thus we
converted the hydroxyl group of DPyVPhE to the methoxyl
group via the methylation to generate the new coordinative
[25]
monomer of MVPhDPy
Scheme 6). The conversion from DPyVPhE to MVPhDPy
for higher catalytic activity
(
could approach 72% within 5.5 hr and was recognized by
1
the H NMR spectrum (Figure S4). The ORTEP diagram
further confirmed that the structures of DPyVPhE and
MVPhDPy are quite similar and could be only differentiated
by the hydroxyl group and the methoxyl group (Figure 5).
Given by the experience of Catalyst 3, the polymer back-
bone was obtained from free radical polymerization of
SCHEME 6 Synthesis of MVPhDPy monomer from DPyVPhE
via methylation
FIGURE 5 ORTEP diagram of MVPhDPy depicted with
ellipsoids at the 50% probability. Selected bond lengths (Å) and angles
ꢀ
(
) for MVPhDPy: O(1)-C(21) 1.4220(16), O(1)-C(1) 1.4340(14), N
FIGURE 4 ORTEP diagram of DPyVPhE-Pd(OAc)
2
depicted
(1)-C(7) 1.3371(16), N(1)-C(11) 1.3374(18), N(2)-C(2) 1.3313(16), N
(2)-C(6) 1.3360(18), C(19)-C(20) 1.303(2), C(21)-O(1)-C(1) 115.76
(9), C(7)-N(1)-C(11) 117.28(12), C(2)-N(2)-C(6) 117.08(11), O(1)-C
(1)-C(7) 105.55(9), O(1)-C(1)-C(2) 109.17(9), O(1)-C(1)-C(12) 112.27
(10), N(2)-C(2)-C(3) 122.31(12), N(2)-C(2)-C(1) 118.42(10), N(2)-C
(6)-C(5) 124.66(13), N(2)-C(6)-H(6) 117.7, N(1)-C(7)-C(8) 122.81
(12), N(1)-C(7)-C(1) 114.67(10), N(1)-C(11)-C(10) 123.87(14), N(1)-
C(11)-H(11) 118.1, O(1)-C(21)-H(21A) 109.5, O(1)-C(21)-H(21B)
109.5, and O(1)-C(21)-H(21C) 109.5
with ellipsoids at the 50% probability. Selected bond lengths (Å) and
ꢀ
angles ( ) for DPyVPhE-Pd(OAc)
2
: Pd-N(1) 2.004(3), Pd-N(2) 2.009
(
(
(
(
3), Pd-O(1) 2.016(2), Pd-O(3) 2.016(2), O(5)-C(1) 1.409(4), C(19)-C
20) 1.306(6), N(1)-Pd-N(2) 86.68(11), N(1)-Pd-O(1) 175.59(11), N
2)-Pd-O(1) 92.76(10), N(1)-Pd-O(3) 92.02(11), N(2)-Pd-O(3) 170.78
11), O(1)-Pd-O(3) 89.22(10), C(21)-O(1)-Pd 119.9(2), C(23)-O(3)-Pd
1
23.5(3), C(2)-N(1)-Pd 121.0(2), C(6)-N(1)-Pd 119.5(2), C(11)-N(2)-
Pd 120.2(2), and C(7)-N(2)-Pd 119.9(2)

1
0
CHANG ET AL.
SC HEME 7 Synthesis of
poly(MVPhDPy-co-NIPAM)-Pd(OAc)
Catalyst 4)
2
(
1
FIGURE 6 The (a) H NMR
spectrum and (b) GPC traces of
poly(MVPhDPy-co-NIPAM)
the reaction with KOH, K CO , N(C H ) , and Na CO
3
reaction have been identified by X-ray photoelectron spec-
troscopy (Figure 7), which demonstrated that Pd(II) is the
major species but the accumulation of Pd(0) could be
observed after five times recycling. The trend in the substitu-
ent effect and the occurrence of accumulated Pd(0) matched
the observation of the typical mechanism of the Suzuki-
2
3
2
5 3
2
(Table 6, Entries 1–5). The versatility of Catalyst 4 was
demonstrated by the mediation of the Suzuki-Miyaura reac-
tion with varied bromobenzene derivatives, which all
achieved high yield with a TON larger than 200 (Table 6,
Entries 6–11). After the reaction of 4-tolyboronic acid and
bromobenzene, Catalyst 4 was recycled by simple filtration
and then used to mediate the same reaction for another four
times. The leakage of palladium in the recycling test was not
detectable and the yield was higher than 94%, implying that
the structure of MVPhDPy was more stable and thus the
heterogeneous catalyst of poly(MVPhDPy-co-NIPAM)-Pd
[
30]
Miyaura reaction.
3
3
| EXPERIMENTAL
.1 | Materials
(
OAc) can be applied to the Suzuki-Miyaura reaction under
Solvents were dried by refluxing for 24 hr with
sodium/benzophenone (Tetrahydrofuran [THF], ether) or
2
a harsh condition. The highest TON value for Catalyst 4 was
then evaluated by the reaction of 4-tolyboronic acid and
iodobenzene as 5,260 (Table 6, Entry 12).
The mechanism of the Suzuki-Miyaura reaction mediated
by these polymeric heterogeneous catalysts is proposed to be
similar to that reported for homogeneous catalysis
CaH
(toluene, CH
Cl
,
pyridine, DMF, CH CN,
3
2
2
2
o-xylene). 2-bromopyridine (>99%, Aldrich), n-BuLi
(2.5 M in hexanes, Aldrich), 2-pyridinecarboxaldehyde
(>99%, Aldrich), sodium hydride (60%, ACROS), acryloyl
0
chloride (96%, Alfa Aesar), 2,2 -azobis(isobutyronitrile)
[
28–30]
(Scheme 8).
The Pd(II) coordinated by the polymer
(AIBN, Showa), benzylalcohol (99%, ACROS),
2,2,6,6-Tetramethyl-1-piperidinyloxy (98%, Alfa Aesar),
KOH (85%, Aldrich), phenylethanol (98%, Aldrich), and
potassium carbonate (K CO ) (99%, Aldrich) were used as
backbone is transformed into Pd(0) and reacts with aryl
halide via oxidative addition. After the replacement of halide
by the nucleophile, the aryl group on 4-tolyboronic acid
exchanges with nucleophile. Two aryl groups on the
Pd(II) center then form the product via the reduction elimi-
nation and Pd(II) is reduced to Pd(0) to start the next cata-
lytic cycle. The palladium species before and after the
2
3
received. Copper(II) bromide (CuBr2), copper(II)
trifluoromethanesulfonate (Cu(OTf) ), palladium acetate (Pd
2
(OAc)2),
4-tolyboronic
acid,
bromobenzene,
4-bromobenonitrile, 4-bromoanisole, indole, and methyl

CHANG ET AL.
11
TABLE 6 Suzuki-Miyaura reaction
catalyzed by poly(MVPhDPy-co-
2
NIPAM)-Pd(OAc) (Catalyst 4) with
varied solvents and bromobenzene
a
derivatives
b
R = ─H, Yield, Pd leakage : First cycle: 99%, 0%. Fourth cycle: 98%, 0%
Second cycle: 99%, 0%. Fifth cycle: 94%, 0%
Third cycle: 99%, 0%
R = ─CN, Yield, Pd leakage: First cycle: 99%, 0%. Fourth cycle: 99%, 0.2%
Second cycle: 99%, 0%. Fifth cycle: 99%, 0.2%
Third cycle: 99%, 0%
c
d
TOF (h−1
)
Entry
X
R
Time (hr)
Base
Na CO
CO
KOH
Cs CO
N(C
Yield (%)
Trace
68
TON
1
2
3
4
5
6
7
8
9
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
I
H
5
5
2
3
—
—
28
36
42
5
H
K
2
3
141
179
208
23
H
5
86
H
5
2
3
99
H
5
2
H
5
3
3
3
3
3
3
3
)
3
11
OMe
5
Cs
Cs
Cs
Cs
Cs
Cs
Cs
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
98
206
206
206
208
208
208
5,260
41
41
41
52
52
52
263
NH
CH
CH(CH
2
5
98
3
5
99
)
3 2
4
99
1
1
1
0
1
2
NO
CN
H
2
4
99
4
99
e
20
95
a
Conditions: bromobenzene (1 mmol), 4-tolylboronic acid (1.5 mmol), Catalyst 4 (0.48 mol%), base (0.95 mmol),
ꢀ
o-xylene (2 mL), 90 C.
b
Metal leakage was determined by ICP-AES.
c
1
The yield was calculated by the H NMR spectrum with the internal standard of mesitylene.
d
e
Turnover number (TON) was determined from the quantity of product and catalyst.
Catalyst 4 (0.018 mol%).
FIGURE 7 XPS, X-ray photoelectron spectroscopy spectrum of
Catalyst 4 in fresh and after the fifth mediation of the Suzuki-Miyaura
reaction
SCHEME 8 Proposed mechanism of the Suzuki-Miyaura
reaction

1
2
CHANG ET AL.
3,3,3-trifluoropyruvate were purchased from Alfa Aesar and
After H -evolution stopped (1.5 hr), 4.66 mL (57.6 mmol,
2
used as received without further purification. Deuterated sol-
vents (Aldrich) were dried over molecular sieves before use.
1.2 eq.) of acryloyl chloride was added slowly into the solu-
ꢀ
tion at 0 C followed by the addition of NH Cl to quench the
4
excess NaH after 60 min. The crude product was partitioned
into CH Cl2 and water layers. The aqueous layer was
2
3
.2 | Instrumentation
washed twice with CH Cl and all CH Cl solution was
2
2
2
2
1
13
H NMR and C NMR spectra were recorded by Mercury-
dried by anhydrous MgSO . The product of DPyMA was
4
4
00 spectrometers, using deuterated solvents (CDCl3)
obtained after chromatography (CH Cl /MeOH = 15/1) as a
2
2
1
obtained from Aldrich and internal standard of mesitylene
slightly yellow oil (3 g, 26%). H NMR (400 MHz, CDCl )
3
1
(0.1 mL) if necessary. The H NMR spectrum was used to
δ 8.54 (d, 2H), 7.68 (t, J = 12.8 Hz, 2H), 7.57 (d,
J = 7.8 Hz, 2H), 7.18 (t, 2H), 6.96 (s, 1H), 6.51 (d, 1H),
characterize the DPyMA and PDPyMA as well as calculate
the conversion of reactions. Chemical shifts were calibrated
13
6.30 (ddd, J = 17.3 Hz, 1H), and 5.89 (d, 1H). C NMR
by δ 7.24 ppm (CDCl ). The Ultraviolet–vis spectrum was
(101 MHz, CDCl ) δ 157.9, 149.5, 136.8, 131.9, 128.0,
3
3
measured by a SHIMADZU UV-1800 instrument from
122.9, 122.0, 78.8, 77.3, and 77. Anal. Calcd. (found) for
1,100 to 190 nm. GPC was carried out by the DMF–LiBr
C H N O : N, 11.66 (11.59); C, 69.99 (69.55); and H,
1
4 12 2 2
eluent using the Waters 600 liquid chromatograph equipped
with a 101 refractive index detector and styragel HR col-
umns (HR2; HR5). The signal was collected by a DIONEX
Shodex RI-101 refractometer (RI) detector and an UltiMate
5.03 (4.98).
3.5 | Synthesis of DPyVPhE
3
000 variable wavelength detector operated at 254 nm for
A 60 mL THF solution of 9.0 g (48 mmol, 1.0 eq.) BPyOH
was added to another 60 mL THF solution of 2.3 g
the DMF system. The calibration was based on narrow linear
poly(ethylene oxide) standard for the DMF system. The
metal quantity of heterogeneous catalysts and residual solu-
tions were analyzed on an Agilent 725 ICP-AES.
[
43]
(96 mmol, 2.0 eq.) NaH at room temperature under N
After H -evolution stopped (1.0 hr), 8.27 mL (57.6 mmol,
.
2
2
1.2 eq.) of 4-vinylbenzyl chloride was added slowly into
ꢀ
the solution at 0 C followed by the addition of NH Cl to
4
quench the excess NaH after 5 hr. The crude product was
3
.3 | Synthesis of di(pyridin-2-yl)methanol
partitioned into CH Cl2 and water layers. The aqueous
2
Di(pyridin-2-yl)methanol (BPyOH) was synthesized by fol-
layer was washed twice with CH Cl and all CH Cl solu-
2
2
2
2
[51]
lowing the reported procedure.
2-bromopyridine (9.5 mL,
tion was dried by anhydrous MgSO . The product of
4
1
00 mmol) and n-BuLi (62.5 mL, 100 mmol, 1.6 M in hex-
DPyVPhE was obtained after chromatography (Hexane/
EtOAc = 7/1) as a slightly yellow oil (10.4 g, 72%). H
ꢀ
1
ane) were mixed at −78 C in anhydrous Et O (200 mL)
2
under a N2 atmosphere for 20 min. The reaction was
NMR (400 MHz, CDCl ) δ 8.48 (ddd, J = 4.9, 1.8, 0.8 Hz,
3
then quenched with 2-pyridinecarboxaldehyde (9.5 mL,
2H), 7.87 (dt, J = 8.0, 1.0 Hz, 2H), 7.62 (td, J = 7.8,
1.8 Hz, 2H), 7.16–7.05 (m, 4H), 6.95 (d, J = 8.2 Hz, 2H),
6.59 (dd, J = 17.6, 10.9 Hz, 1H), 6.43 (s, 1H), 5.61 (dd,
J = 17.6, 1.0 Hz, 1H), 5.11 (dd, J = 10.9, 1.0 Hz, 1H), and
1
3
00 mmol) at the same temperature. After reacting for
0 min, the mixture was diluted by 2.0 M HCl (160 mL)
and then pH value of the mixture was tuned to 8 by solid
13
NaOH. The solution was then extracted with Et O. The
3.67 (s, 2H). C NMR (101 MHz, CDCl ) δ 162.65
2
3
organic layer was washed by brine and dried over MgSO4.
The residual mixture was purified by chromatography using
(s, 2H), 147.26 (s, 7H), 136.76 (d, J = 5.5 Hz, 12H),
135.22 (s, 1H), 130.83 (s, 7H), 125.32 (s, 7H), 122.06
(s, 8H), 121.35 (s, 7H), 112.79 (s, 4H), 78.36 (s, 1H), and
47.36 (s, 4H).
silica gel (petroleum ether-EtOAc) to afford BPyOH (10.8 g,
1
6
0%). H NMR (400 MHz, CDCl ) δ 8.54 (d, 2H), 7.64
3
(
(
(
t, J = 7.7 Hz, 2H), 7.51 (d, J = 7.9 Hz, 2H), 7.17
t, J = 7.4 Hz, 2H), and 5.87 (s, 1H), 5.78 (br, 1H). C NMR
13
3.6 | Synthesis of MVPhDPy
101 MHz, CDCl ) δ 160.72, 148.19, 136.85, 122.58, 121.13,
3
and 75.18. Anal. Calcd. (found) for C H N O: N, 15.04
A 85 mL THF solution of 11.9 g (40 mmol, 1.0 eq.) DPyVE
was added to another 85 mL THF solution of 3.84 g
1
1 10 2
(14.94); C, 70.95 (70.56); and H, 5.41 (5.32).
[
25]
(160 mmol, 2.0 eq.) NaH at room temperature under N2.
After H -evolution had stopped (2.5 hr), 3.0 mL (48 mmol,
2
3
.4 | Synthesis of DPyMA
ꢀ
1
.2 eq.) of CH I was added slowly into the solution at 0 C
3
A 60 mL THF solution of 9.0 g (48 mmol, 1.0 eq.) BPyOH
was added to another 60 mL THF solution of 2.3 g
followed by the addition of NH Cl to quench the excess
4
NaH after 5.5 hr. The crude product was partitioned into
CH Cl and water layers. The aqueous layer was washed
[
25]
(96 mmol, 2.0 eq.) NaH at room temperature under N2.
2
2

CHANG ET AL.
13
twice with CH Cl and all CH Cl solution was dried by
in CH Cl (20.0 mL) and then recrystallized by the addition
2
2
2
2
2
2
anhydrous MgSO . The product of MVPhDPy was obtained
of hexane (200.0 mL).
4
after chromatography (Hexane/EtOAc = 4/1) as a slightly
1
yellow oil (9.1 g, 72%). H NMR (400 MHz, CDCl ) δ 8.58
3
(
7
ddd, J = 5.8, 1.8, 0.9 Hz, 2H), 7.52 (td, J = 7.8, 1.7, 2H),
.35 (dt, J = 8.0, 1.0 Hz, 2H), 7.16–7.06 (m, 4H), 6.77 (d,
3.11 | Synthesis of DPyMA-coordinated metal
complexes
J = 8.2 Hz, 2H), 6.58 (dd, J = 22.6, 10.9 Hz, 1H), 5.60 (d,
J = 17.6 Hz, 1H), 5.11 (d, J = 10.7 Hz, 1H), 3.99 (s, 2H),
The synthesis of monomeric complex of [(DPyMA)CuBr
(
μ-Br)] was described as an example. A CH Cl solution of
13
2
2
2
and 3.27 (s, 3H). C NMR (101 MHz, CDCl ) δ 162.66
3
DPyMA (0.54 g, 2.20 mmol) and CuBr (0.25 g, 1.10 mmol)
2
(
1
(
8
s, 2H), 148.46 (s, 10H), 137.25 (s, 2H), 136.69 (s, 5H),
36.15 (s, 10H), 135.00 (s, 1H), 130.28 (s, 9H), 125.34
s, 9H), 122.19 (s, 11H), 121.87 (s, 11H), 112.73 (s, 6H),
6.18 (s, 1H), 51.18 (s, 3H), and 38.24 (s, 6H).
was stirred for 24 hr at room temperature. The solution was
then vacuumed to obtain the precipitation of black powder
as the product of DPyMA-CuBr2.
3
.7 | Synthesis of PDPyMA
3.12 | Synthesis of PDPyMA-Pd(OAc)
2
(
Catalyst 1a)
A DMF solution (15 mL) of DPyMA (3.00 g, 12.50 mmol)
and AIBN (0.21 g, 1.25 mmol) was heated to 60 C and
ꢀ
PDPyMA (0.24 g, DPyMA to Pd(OAc)2 = 1:1) and
stirred for 36 hr. The residual liquid including monomer and
DMF was removed under vacuum. The pale yellow powder
Pd(OAc)2 (0.22 g, 1.00 mmol) were mixed in a CH Cl2
solution (15 mL) at room temperature for 24 hr. PDPyMA-
2
was dissolved in CH Cl (10.0 mL) and then recrystallized
2
2
Pd(OAc) was gradually precipitated during the reaction and
2
by the addition of hexane (100.0 mL).
was obtained by filtration.
3
2
.8 | Synthesis of poly(1,1-di(pyridin-2-yl)-
3
.13 | Synthesis of PDPyMA-Cu(OTf)2
-(4-vinylphenyl)Ethan-1-ol) (PDPyVPhE)
(
Catalyst 1b)
A toluene solution (11.5 mL) of DPyVPh (1.20 g,
PDPyMA (0.36 g, DPyMA to Cu(OTf)2 = 1.5:1) and
Cu(OTf)2 (0.48 g, 1.00 mmol) were mixed in a CH Cl2
solution (20 mL) at room temperature for 24 hr. PDPyMA-
Cu(OTf) was gradually precipitated during the reaction and
4
.00 mmol) and AIBN (0.07 g, 0.40 mmol) was heated
ꢀ
2
to 60 C and stirred for 48 hr. The residual liquid includ-
ing monomer and toluene was removed by vacuum. The
white powder was dissolved in CH Cl (10.0 mL) and
2
2
2
was obtained by filtration.
then recrystallized by the addition of hexane
100.0 mL).
(
3
.14 | Synthesis of PDPyVPhE-Pd(OAc)2
3
.9 | Synthesis of poly(DPyVPhE-co-NIPAM)
(
Catalyst 2)
A toluene solution (34.3 mL) of DPyVPhE (1.20 g,
PDPyVPhE (0.30 g, DPyVPhE to Pd(OAc)2 = 1:1) and
4
.00 mmol), NIPAM (0.91 g, 8.00 mmol), and AIBN
Pd(OAc)2 (0.22 g, 1.00 mmol) were mixed in a CH Cl2
2
ꢀ
(0.19 g, 1.20 mmol) was heated to 60 C and stirred for
solution (15 mL) at room temperature for 24 hr.
48 hrs. The residual liquid including monomer and toluene
PDPyVPhE-Pd(OAc) was gradually precipitated during the
2
was removed by vacuum. The white powder was dissolved
in CH Cl (20.0 mL) and then recrystallized by the addition
reaction and was obtained by filtration.
2
2
of hexane (200.0 mL).
3
.15 | Synthesis of poly(DPyVE-co-NIPAM)-
3
.10 | Synthesis of poly(MVPhDPy-co-
Pd(OAc) (Catalyst 3)
2
NIPAM)
Poly(DPyVPhE-co-NIPAM) (0.87 g, DPyVPhE to
Pd(OAc) = 1:1) and Pd(OAc) (0.22 g, 1.00 mmol) were
mixed in a CH Cl solution (15 mL) at room temperature for
24 hr. Poly(DPyVPhE-co-NIPAM)-Pd(OAc) was gradually
A toluene solution (61.7 mL) of MVPhDPy (1.14 g,
2
2
3.60 mmol), NIPAM (2.04 g, 18.00 mmol), and AIBN
2
2
ꢀ
(0.35 g, 2.20 mmol) was heated to 60 C and stirred for
2
4
8 hr. The residual liquid including monomer and toluene
precipitated during the reaction and was obtained by
filtration.
was removed by vacuum. The white powder was dissolved

1
4
CHANG ET AL.
3
.16 | Synthesis of poly(MVPhDPy-co-
4 could approach the TON as 5,260. The Pd leakage was
undetectable and the yield was constantly higher than 94%
after 5 times recycling. In the literature, the range of TON
NIPAM)-Pd(OAc) (Catalyst 4)
2
Poly(MVPhDPy-co-NIPAM) (0.88 g, MVPhDPy to
Pd(OAc) = 1:1) and Pd(OAc) (0.22 g, 1.00 mmol) were
mixed in a CH Cl solution (15 mL) at room temperature for
for heterogeneous catalysis of Suzuki-Miyaura coupling
2
2
[47,52–54]
is generally around 30 to 20,000.
Although
2
2
poly(MVPhDPy-co-NIPAM)-Pd(OAc) showed a moderate
2
24 hr. Poly(MVPhDPy-co-NIPAM)-Pd(OAc)2 was gradu-
catalytic activity, the ease of catalyst recycle and the little
leakage of metal ions along with the versatility of polymeric
platform that could coordinate with different metal ions to
catalyze varied reactions provide this copolymer a great
potential for future applications.
ally precipitated during the reaction and was obtained by
filtration.
3
.17 | General process for the Suzuki reaction
The catalyst (0.01 g), bromobenzene (1.00 mmol), 4-tolyboronic
ACKNOWLEDGMENTS
(
1.50 mmol), and various base (0.95 mmol) were mixed in
ꢀ
various solvents (2 mL) at 90 C for 4 hr. The conversion
was calculated by the H NMR and the internal standard is
We thank the Ministry of Science and Technology, Taiwan,
1
(MOST 107-2113-M-007-014) for support of this research.
mesitylene (0.1 mL).
The highest TON was obtained by the reaction of catalyst
(
(
0.018 mol%), iodobenzene (1.00 mmol), 4-tolyboronic
1.50 mmol), and Cs2CO3 (0.95 mmol) in o-xylene (2 mL)
ORCID
Chi-How Peng https://orcid.org/0000-0002-8305-8624
ꢀ
1
at 90 C for 20 hr. The conversion was calculated by H
NMR with the internal standard of mesitylene (0.1 mL).
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.18 | General process for Friedel-Craft
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How to cite this article: Chang H-C, Li J-Q,
Lin C-K, et al. Development of dipyridine-based
coordinative polymers for reusable heterogeneous
catalysts. J Chin Chem Soc. 2019;1–15. https://doi.
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