Palladium-melamine complex anchored on magnetic nanoparticles: A novel promoter for C-C cross coupling reaction

Article abstract of DOI:10.1016/j.jorganchem.2019.02.010

A palladium-melamine complex deposited on Fe₃O₄@SiO₂ nanoparticles (MNPs-Mel-Pd) was considered as an effective catalyst for C-C cross-coupling (Mirozoki-Heck) reaction. Surface and magnetic properties of the prepared core-shell hybrid nanocatalyst was characterized using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray, vibrating sample magnetometry, transmission and scanning electron microscopy techniques and ICP/OES analysis. It was found that the heterogeneous nanocatalyst could be recovered simply and reused numerous times without loss of its catalytic activity. The advantages of this new methodology are: isolation of highly pure products without chromatography techniques, reusability of the catalyst using a magnet, easy workup procedure and negligible leaching of palladium.

Full text of DOI:10.1016/j.jorganchem.2019.02.010

Accepted Manuscript
Palladium-melamine complex anchored on magnetic nanoparticles: A novel promoter
for C-C cross coupling reaction
Mohammad Ali Bodaghifard
PII:
S0022-328X(18)30937-9
DOI:
https://doi.org/10.1016/j.jorganchem.2019.02.010
JOM 20712
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 27 October 2018
Revised Date: 24 January 2019
Accepted Date: 6 February 2019
Please cite this article as: M.A. Bodaghifard, Palladium-melamine complex anchored on magnetic
nanoparticles: A novel promoter for C-C cross coupling reaction, Journal of Organometallic Chemistry
(2019), doi: https://doi.org/10.1016/j.jorganchem.2019.02.010.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Palladium-melamine complex anchored on magnetic nanoparticles: A novel promoter
for C-C cross coupling reaction
Mohammad Ali Bodaghifarda,b*
* a Correspondence to: Mohammad Ali Bodaghifard, Department of Chemistry, Faculty of Science, Arak
University, 38156-88349, Arak, Iran. b Institute of Nanosciences & Nanotechnology, Arak University, Arak, Iran
E-mail: mbodaghi2007@yahoo.com or m-bodaghifard@araku.ac.ir
Abstract
A palladium-melamine complex deposited on Fe3O4@SiO2 nanoparticles (MNPs-Mel-Pd)
was considered as an effective catalyst for C-C cross-coupling (Mirozoki-Heck) reaction.
Surface and magnetic properties of the prepared core-shell hybrid nanocatalyst was
characterized using Fourier transform infrared spectroscopy, X-ray diffraction,
thermogravimetric analysis, energy-dispersive X-ray, vibrating sample magnetometry,
transmission and scanning electron microscopy techniques and ICP/OES analysis. It was
found that the heterogeneous nanocatalyst could be recovered simply and reused numerous
times without loss of its catalytic activity. The advantages of this new methodology are:
isolation of highly pure products without chromatography techniques, reusability of the
catalyst using a magnet, easy workup procedure and negligible leaching of palladium.
Keywords:
Palladium; Nanocatalyst; Magnetic separation; Heck reaction; Magnetic nanoparticles
1. Introduction
One of the significant structural motifs in organic compounds, bioactive materials,
pharmaceuticals and natural products are olefins.[1] These alkene derivatives ordinarily
demonstrated anti-inflammatory,[2] cardioprotective,[3] antitumor[4] and neuroprotective[5]
properties. Due to importance of the preparation of olefins, a wide range of synthetic methods
have been developed. Palladium(0) catalyzed Mizoroki-Heck cross-coupling reaction, a Nobel
thought, is among the most widely used procedures for the formation of C(sp2)-C(sp2) bonds
in organic synthesis,[6] which allows the alkylation, arylation or vinylation of numerous
alkenes via their reaction with vinyl, aryl, benzyl or allyl halides in the presence of a base.[7]
Homogeneous palladium catalysts have been widely considered in synthetic organic
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[8]
chemistry due to their high selectivity and catalytic activity.
Recycling of the catalyst,
purification of the products and deactivation of the catalyst are numerous disadvantages of
homogeneous catalysts. Furthermore, because of high cost and toxicity of Pd, its removal
from synthetic products is highly appropriate.[9] Isolation and separation of the final products
is attained by centrifugation or simple filtration when immobilized catalytically active
molecule on a solid material is used. Moreover, these methods reduce heavy metal
environmental contamination and barricade the loss of trace amounts of the catalysts which is
beneficial in the usage of costly catalysts.[10] Although, heterogeneous catalysts can be easily
recovered and reused, their active sites are not as attainable as in homogeneous catalysts, and
therefore, the catalytic activity is regularly reduced. Nanocatalysts bridge the gap between
heterogeneous and homogeneous catalysis, keeping the appropriate attributes of both
systems.[11] Recently, solid supported palladium nanoparticles has attracted great attention in
provision of stable and active catalytic systems. Several supports such as silica-based
materials,[12] metal oxides,[13] dendrimers,[14] polymers,[15] carbon nanotubes,[16] ionic
liquids,[17]
gelatin,[18]
polyaniline,[19]
carbohydrate-based
materials[20]
and
polyvinylpyrrolidone[21] have been employed. Magnetic nanoparticles (MNPs) have attracted
increasing attention in catalysis, magnetic fluids, adsorbent, biotechnology data storage,
environmental remediation and biomedicine applications.[22] Magnetite (Fe3O4) is quite
attractive due to its low-cost, unique magnetic features and strong absorption
characteristics[23]; though, pure Fe3O4 applications are limited by its ease of oxidation, poor
flame retardant effect and fast heat transfer. Several polymeric and inorganic substances have
been described as carriers of magnetic materials to solve these problems.[24] Among them, the
creation core-shell nanostructures have been recognized as the most efficient method.[25] Due
to non-toxicity, biocompatibility, excellent stability, and easy modification by organosilane
coupling agents, the silica coating is a good surface modifier.[26] In this paper, the preparation
and characterization of a novel and heterogeneous nanocatalyst was focused on, using Fe3O4
magnetic nanoparticles coated with SiO2 as a convenient support for palladium with
melamine as an appropriate ligand, and this reusable catalyst was applied for the Heck
reaction (Scheme 1).
2. Experimental
2.1.Preparation of palladium-melamine stabilized on Fe3O4@SiO2 MNPs (MNPs-
Mel-Pd)
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Fe3O4 MNPs were synthesized in alkali solution of Fe(III) and Fe(II) (2:1) at 80˚C using the
chemical co-precipitation technique.[27] The Fe3O4 magnetic nanoparticles coated with SiO2
were prepared using the Stober method.[28] Aminopropyl-modified silica-coated MNPs
(Fe3O4@SiO2-Pr-NH2) was obtained via a described method in the literature.[29] Triazine
dichloride-functionalized silica-coated MNPs (MNPs-TDCl) were synthesized according to
the authors’ recently reported procedure.[30] N-ethyldiisopropylamine, as a base (0.7 mL), was
added to a mixture of the oven-dried Fe3O4@SiO2-Pr-NH2 MNPs (1 g) and dried THF (10
mL) in a 50 mL round-bottomed flask. The mixture was stirred in ice bath for 15 min at 5°C,
and then, cyanuric chloride (1 g) was added to the reaction mixture and stirred for 24 h at this
temperature. The ligand grafted silica-coated MNPs were isolated by an external magnet and
washed with hot THF to remove unreacted cyanuric chloride. Using an ultrasonic bath,
MNPs-TDCl nanoparticles (1.0 g) were dispersed in 40 mL dioxane in a 100 mL round-
bottomed flask and 15 mL ammonia (25%) was added to the suspension. The reaction mixture
was refluxed at 80°C for 24 h. The Melamine grafted on Fe3O4@SiO2 MNPs (MNPs-Mel)
was separated using a magnet, washed with dioxane and dried under vacuum. Palladium-
melamine stabilized on Fe3O4@SiO2 MNPs(MNPs-Mel-Pd) catalyst was prepared in a typical
procedure as follows: MNPs-Mel (1 g) and PdCl2 (0.034 g, 0.2 mmol) were stirred in DMF (5
ml) at 100°C for 24 h. Magnetic nanocatalyst was separated with an external magnet and
washed with deionized water to remove the excess PdCl2 and dried under vacuum to obtain
the final catalyst (MNPs-Mel-Pd) which was then used in the Heck coupling reaction.
2.2. General procedure for Heck reaction
A mixture of aryl halide (1 mmol), alkene (1.2 mmol), K2CO3 (2 mmol) and MNPs-Mel-Pd
(0.02 g) was stirred in DMF at 100°C and the progress of the reaction was monitored by TLC.
After completion of the reaction, the catalyst was separated using an external magnet, the
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mixture was cooled to room temperature and the product was solidified by addition of water
to the mixture and pure products were obtained in yields of 76-99%.
3. Results and Discussion
3.1.Characterization of novel MNPs-Mel-Pd catalyst
The nanocatalyst was prepared using a simple route, which is shown in Scheme 1 and was
characterized using Fourier transform infrared (FT-IR) spectroscopy, scanning electron
microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD),
energy-dispersive X-ray spectroscopy (EDS), vibrating sample magnetometry (VSM),
thermogravimetric (TGA) and ICP/OES analysis.
Fe3O4 MNPs
Fe3O4
Fe3O4@SiO2
SiO2
NH3
TEOS
APTMS
toluene
reflux
Fe2+
Fe3+
Fe3O4
+
EtOH/H2O
H2O
r.t.
))))
80 ºC
Cl
N
N
NH2
Cl
N
Cl
H2N
Si
O
OMe
O
NH
N
N
SiO2
OMe
Si
O
Si
O
O
Fe3O4
O
Cl
N
Cl
NH3
SiO2
Fe3O4
OMe
N-ethyldiisopropylamine
dioxane
reflux
O
O
THF
r.t.
MeO
Si
MNPs TDCl
Fe3O4@SiO2-Pr-NH2
H2N
NH
Cl2Pd
PdCl2
NH
N
H2N
N
N
NH
N
Cl2Pd
PdCl2
N
N
N
N
NH2
N
Si
N
O
N
Pd
Cl2
HN
OMe
O
NH
SiO2
OMe
Si
Si
O
O
O
Fe3O4
Pd
Cl2
O
SiO2
Fe3O4
PdCl2
OMe
O
O
DMF
MeO
Si
100 ºC
MNPs-Mel
MNPs-Mel-Pd
N
Cl2Pd
PdCl2
NH
N
N
N
HN
Pd
Cl2
Scheme 1. Synthesis of palladium-melamine stabilized on Fe3O4@SiO2 MNPs (MNPs-Mel-Pd)
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FT-IR spectra can be used to demonstrate successful functionalization of the MNPs. The FT-
IR spectra for Fe3O4 nanoparticles, Fe3O4@SiO2, Fe3O4@SiO2-Pr-NH2, MNPs-TDCl, MNPs-
Mel and MNPs-Mel-Pd are shown in Figure 1. The strong band at 584 cm-1 shows the
characteristic Fe-O bonds of Fe3O4 (Figure 1a). The spectrum of Fe3O4 shows that a band
appeared at 1631 cm-1 corresponding to the stretching vibrational mode of H-O-H adsorbed
layer. Furthermore, stretching vibration bands in the range of 3200-3500 cm-1 include both
symmetric and asymmetric modes of O-H bonds. Fe3O4@SiO2 shows characteristic FT-IR
asymmetric stretching bands at 1082 cm-1 and symmetric stretching at 964, 806 and 457 cm-1
for the Si-O-Si group and supports the creation of SiO2 shell (Figure 1b). The immobilization
of the attached alkyl groups was indicated by the weak bands at 2926 and 2972 cm-1 related to
C-H stretching modes (Figure 1c). In heterocyclic rings, C=C and C=N bonds are indicated by
the bands at 1490-1620 cm-1 (Figure 1d, e). Furthermore, the broad band change in the range
of 1400-1650 cm-1 of MNPs-Mel-Pd spectrum is attributed to the formation of palladium
complex (Figure 5f). All these bands show that the surface of the MNPs was successfully
modified with grafted functional groups.
Figure 1. FT-IR spectra of (a) Fe3O4 MNPs, (b) Fe3O4@SiO2, (c) Fe3O4@SiO2-Pr-NH2, (d) MNPs-TDCl, (e)
MNPs-Mel and (f) MNPs-Mel-Pd.
As shown in Figure 2a, the SEM image of MNPs-Mel-Pd reveal that these nanoparticles have
been formed with a mean diameter of about 20-30 nm and a spherical structure. Moreover, no
significant change in the surface morphology occurred with the bonding of the palladium onto
MNPs-Mel. The morphology of MNPs-Mel-Pd was studied using TEM. The dark nano Fe3O4
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cores are surrounded by grey silica shell about 5-10 nm thick, and the mean size of the
synthesized nanoparticles grain size is about 20-25 nm (Figure 2b).
Figure 2. (a) FE-SEM image and (b) TEM image of MNPs-Mel-Pd nanoparticles.
The EDS analysis of the MNPs-Mel-Pd (Figure 3) indicates that Pd particles are loaded
onto the MNPs-Mel surface. The EDS spectrum also showed characteristic signals for Fe, O,
Si, C and N. The exact amount of palladium in MNPs-Mel-Pd was measured using the
ICP/OES technique. Based on ICP/OES analysis, the amount of palladium in the catalyst is
1.79 × 10-3 mol g-1.
Figure 3. EDS spectrum of MNPs-Mel-Pd.
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Purity and crystalline nature of synthesized nano Fe3O4, MNPs-Mel and MNPs-Mel-Pd were
investigated using XRD (Figure 4). These diffractograms display seven characteristic Bragg’s
peaks appearing at 2θ = 30.3, 35.6, 43.3, 53.8, 57.3, 62.9 and 74.5° which correspond to the
(220), (311), (400), (422), (511), (440) and (533) crystal planes of the cubic inverse spinel
structured magnetite and these match well with the standard Fe3O4 sample (JCPDS card no.
85-1436) (Figure 4a). The emergence of a broad hump around 2θ = 24° is consistent with an
amorphous silica phase Fe3O4@SiO2 (Figure 4b).[31] The presence of the new peaks at 2θ =
40.1, 46.9 and 69.1 which correspond to the (111), (200) and (220) are attributed to the Pd
species (Figure 4c). Similar characteristic Bragg’s peaks indicate that the surface modification
of the nanoparticles does not have any influence on its crystallographic phase. Besides, the
Scherrer’s equation that establishes a relationship between broadening and peak position has
been used to estimate average crystallite size of the nanoparticles using the peak of highest
[32]
intensity, that is, the (311) peak in this case and it has been calculated to be 20.1 nm
which is in the range of the size determined by FE-SEM and TEM analysis (Figure 2).
,
Figure 4. XRD diffraction pattern of (a) Fe3O4 MNPs (b) MNPs-Mel and (C) MNPs-Mel-Pd.
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The functionalization of Fe3O4 MNPs with organic layers and Melamine complex of
palladium and its stability is inferred using thermogravimetric analysis (TGA) and derivative
thermogravimetry (DTG) (Figure 5). The weight loss at temperatures below 200 °C (4%) is
due to the removal of physically adsorbed solvent and surface hydroxyl groups on the catalyst
support. The organic fractions are decomposed in the range of 200-580°C. The main weight
loss of the organic grafting is about 17%, which is similar to the elemental analysis, and
obvious thermal degradation occurs at 220°C, which reveals acceptable stability. According to
this weight loss, 0.57 mmol of organic compounds were loaded on 1 gr of MNPs-Mel-Pd.
Figure 5. TG-DTG analyses for MNPs-Mel-Pd.
The magnetic properties of nanoparticles were characterized using vibrating sample
magnetometer (VSM). Figure 6 shows the typical room temperature magnetization (M) versus
magnetic field (H) (M-H curves or hysteresis loops) of Fe3O4 MNPs and MNPs-Mel-Pd. The
nanoparticles display a typical superparamagnetic behavior. The saturation magnetization of
the Fe3O4 MNPs (Figure 6a) is 57.9 emu/g, which is lower than its bulk counter parts (92.0
emu/g).[33] The saturation magnetization of MNPs-Mel-Pd was 35.8 emu/g, which is lower
than that of Fe3O4 MNPs (Figure 6b). This might be due to the creation of a silica shell and
organic shell around the Fe3O4 core.
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Figure 6. Magnetic hysteresis loops of (a) Fe3O4 MNPs and (b) MNPs-Mel-Pd.
3.2. Catalytic Study
After characterization of the MNPs-Mel-Pd catalyst, its catalytic activity was evaluated in C-
C coupling Heck reaction (Scheme 2).
Scheme 2. MNPs-Mel-Pd catalyzed Heck reaction.
Firstly, using iodobenzene and styrene, a model reaction was selected to optimize carbon-
carbon coupling bond formation in the presence of MNPs-Mel-Pd as an effective and
magnetically separable nanocatalyst. To provide appropriate reaction media, several solvents
such as toluene, DMSO, EtOH, H2O, DMF and water were examined. It was shown that DMF
provided the best yield of the desired product (Table 1, entries 1-5). Afterwards, the effect of
the base on the yield of the Heck reaction was examined and it was found that K2CO3 gave a
better result than Et3N, KOH and Na2CO3 (Table 1, entries 6-9). In order to increase the
product yield and reduce the reaction time, the model reaction was tested at various
temperatures, and at 100°C, a marked increase in the reaction yield and decrease in reaction
time was observed (Table 1, entries 10-12). Comparable yields were obtained when the
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activity of the nanocatalyst in numerous amounts was tested. The best result was obtained
with 20 mg of MNPs-Mel-Pd and in the absence of the nanocatalyst, no product was formed
(Table 1, entries 13-20).
(Table 1)
Under the optimized reaction conditions, the scope of catalytic efficacy of the MNPs-Mel-Pd
catalyst in Heck reaction was extended to the various electron-releasing and electron-
withdrawing aryl iodides and bromides with styrene, methyl and ethyl acrylate (Table 2). As
shown in Table 2, in the efficient coupling reactions of aryl iodides bearing electron‐donating
or ‐withdrawing substituents with olefins at 100°C for 8 h, products in good to excellent
yields (76 to 99%) were obtained. Also, the MNPs-Mel-Pd catalyst displayed good activity
towards bromobenzene with electron-withdrawing aryl bromides and acceptable yields (80-
91%) were obtained when the Heck coupling reactions was carried out at 100°C for 8 h. In
general, methyl and ethyl acrylate are more active than styrene and a substituent such as nitro
at the ortho position of aryl halides slightly reduces the yield of the desired product due to its
steric effect. The product yield for the aryl iodides are higher than aryl bromides, and the
product yields for the aryl halides with electron-withdrawing groups were higher than that
with electron-donating groups. As a result, it is concluded that the MNPs-Mel-Pd is an
effective catalyst for Heck reaction and also displays wide range of functional group
tolerance.
It is reasonable to believe that the Pd grafting with organic functional groups on inorganic
support efficiently limit Pd leaching and particle growth, which permitted this hybrid
nanocatalyst to be reused several times with only a slight loss of its activity. Clearly, the
functionalized catalysts were more stable than the nonfunctionalized catalysts, which lost
their activity gradually because of metal leaching and Pd particle growth.
(Table 2)
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3.3. Reusability of catalyst and heterogeneity test
Recovery of the palladium catalyst at the termination of the reaction is the essential part of the
Heck coupling reaction. Therefore, the reusability and recovery of MNPs-Mel-Pd catalyst was
examined in the reaction of iodobenzene and styrene under the optimized condition. After
completion of the reaction, the catalyst was collected by an external magnet, washed
with ethanol several times, dried under vacuum and reused for the next run. The recycled
MNPs-Mel-Pd catalyst was reused eight times with little loss of activity (Figure 7).
Heterogeneity and palladium leaching of this hybrid nanocatalyst for the model Heck reaction
were examined by the modified ‘hot filtration’ test. The reaction was stopped at 50%
conversion. The solid nanocatalyst was deposited on the magnetic bar. Half of the liquid
reaction mixture was placed into another reaction tube. After an additional 1 hour heating at
100 °C, the catalyst-free portion showed no additional conversion, evidently proving the
heterogeneity of catalyst.
Potential Pd leaching into the reaction mixture was also analyzed with ICP/OES analysis after
eight runs. The amount of palladium in the catalyst is found to be 1.73 × 10-3 mol g-1 after
eight cycles based on ICP/OES measurements. The palladium content in MNPs-Mel-Pd after
six runs is comparable to that of fresh catalyst (1.79 × 10-3 mol g-1 for fresh MNPs-Mel-Pd),
confirming that the leaching of palladium in the reaction mixture is negligible.
Also it is apparent from comparison of the FT-IR spectrum, XRD diffraction patterns of the
reused catalyst (MNPs-Mel-Pd), after eight runs, the recovered catalyst had no understandable
variation in structure (Figure 8). Therefore, these studies suggesting that the prepared hybrid
nanocatalyst possessed good reusability and stability.
Figure 7. Recyclability of catalyst in the coupling reaction of iodobenzene and styrene {Condition: MNPs-TDA-
Pd (20 mg), K2CO3 (2 mmol), DMF, 100 ºC, 8 h}
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Figure 8. FT-IR spectra (left) and XRD diffraction pattern (right) of the fresh catalyst (a) and the six times
reused catalyst (b).
3.4. Comparison of Catalyst
In order to examine the efficiency of the present procedure in comparison with previously
reported protocols, the results of the Heck coupling reaction of iodobenzene with styrene in
the presence of other Pd catalysts were compared. As shown in Table 3, in contrast to
previously reported systems, the catalytic system in this project does not suffer from the harsh
reaction conditions such as high temperature, high amount of catalyst and long reaction time.
In addition, the recyclability and recoverability of this nanocatalyst are more quick and easier
than those of the other catalysts. Furthermore, the Palladium leaching is negligible.
(Table 3)
4. Conclusions
In this work, a palladium-melamine complex stabilized on Fe3O4@SiO2 MNPs (MNPs-Mel-
Pd) catalyst was prepared, which displays superb catalytic efficiency towards Heck reaction.
The synthesized catalyst was confirmed by FT-IR, XRD, TGA, ICP/OES, VSM, TEM, FE-
SEM and EDS techniques. The efficiency of the nanocatalyst was tested in Heck reaction for
preparation of target products in good to excellent yields under moderate to mild experimental
conditions. The good catalytic activity after eight runs due to the negligible leaching of
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palladium (analyzed by ICP/OES technique) from the support during the reaction, confirming
high stability of the catalyst. This reported method offers numerous significant advantages
such as isolation of highly pure products without chromatography technique, simple product
separation procedure, reusability of the catalyst using a magnet and reuse without loss of its
catalytic activity.
Acknowledgements
The authors gratefully acknowledge the financial support of this work (Grant No. 95/1150) by
the Research Council of Arak University.
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Table 1. Optimization of reaction conditions for C-C coupling reaction a
Temp. Yield
Entry Solvent
Base
catalyst (mg)
(ºC)
100
100
reflux
reflux
100
100
100
100
100
80
(%)b
17
45
23
0
1
2
3
Toluene K2CO3 MNPs-TDA-Pd (20)
DMSO
EtOH
H2O
K2CO3 MNPs-TDA-Pd (20)
K2CO3 MNPs-TDA-Pd (20)
K2CO3 MNPs-TDA-Pd (20)
K2CO3 MNPs-TDA-Pd (20)
Et3N
KOH
4
5
6
7
8
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
93
52
56
47
0
77
51
75
89
72
-
MNPs-TDA-Pd (20)
MNPs-TDA-Pd (20)
Na2CO3 MNPs-TDA-Pd (20)
MNPs-TDA-Pd (20)
9
-
10
11
12
13
14
15
16
17
18
19
20
K2CO3 MNPs-TDA-Pd (20)
K2CO3 MNPs-TDA-Pd (20)
K2CO3 MNPs-TDA-Pd (20)
K2CO3 MNPs-TDA-Pd (40)
K2CO3 MNPs-TDA-Pd (10)
K2CO3
K2CO3 Fe3O4 (20)
K2CO3 Fe3O4@SiO2 (20)
K2CO3 Fe3O4@SiO2-Pr-NH2 (20)
K2CO3 Fe3O4@SiO2-TDCl (20)
K2CO3 Fe3O4@SiO2-Mel (20)
60
120
100
100
100
100
100
100
100
100
-
-
-
-
-
-
a
Reaction conditions: iodobenzene (1 mmol), styrene (1.2 mmol), base (2
mmol), 8 h.
b Isolated yield.
17

ACCEPTED MANUSCRIPT
Table 2. Diversity of Heck reaction using MNPs-Mel-Pd under optimal conditions a
M.P. (°C)
Yield
(%)b
86
84
96
88
88
99
91
85
92
80
89
90
81
87
97
86
79
90
84
89
93
93
76
95
86
83
91
83
88
Entry
R1
R2
X
Found
Reported
-
1
2
3
4
5
6
7
8
2,4,6-(Cl)3C6H2 CO2Me
2,4-(Cl)2C6H3
C6H5
I
I
I
100-103
96-99
33-36
32-35
87-90
159-160
159-160
Oil
CO2Me
CO2Me
CO2Me Br
CO2Me
CO2Me
CO2Me Br
CO2Me
CO2Me
CO2Me Br
CO2Me
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
Ph
-
35-37[34]
35-37[34]
88-91[35]
161[36]
C6H5
4-OMeC6H4
4-NO2C6H4
4-NO2C6H4
2-NO2C6H4
4-ClC6H4
4-ClC6H4
4-MeC6H4
C6H5
I
I
161[36]
I
I
Oil[37]
9
73-75
74-77
55-56
Oil
74-75[38]
74-75[38]
56-58[39]
Oil[40]
10
11
12
13
14
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
I
I
Br
I
I
Br
I
I
Br
I
I
I
I
I
Br
I
I
Br
I
C6H5
Oil
Oil[40]
4-OMeC6H4
4-NO2C6H4
4-NO2C6H4
2-NO2C6H4
4-ClC6H4
4-ClC6H4
4-MeC6H4
C6H5
48-50
138-141
138-141
Oil
45-46[41]
138-140[42]
138-140[42]
Oil[43]
Oil
Oil
Oil[43]
Oil[43]
53-55
120-123
120-123
133-136
158-160
158-160
79-82
127-130
128-131
117-119
50-52[43]
123-125[44]
123-125[44]
133-134[45]
158[46]
C6H5
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
4-OMeC6H4
4-NO2C6H4
4-NO2C6H4
2-NO2C6H4
4-ClC6H4
4-ClC6H4
4-MeC6H4
158[46]
68-70[47]
131-132[48]
131-132[48]
119-120[49]
a Reaction conditions: iodobenzene (1 mmol), styrene (1.2 mmol), base (2 mmol),
MNPs-Mel-Pd (0.02 g), DMF, 8 h, 100 °C.
b Isolated yield.
18

ACCEPTED MANUSCRIPT
Table 3. Comparison of results for MNPs-Mel-Pd with those for other catalysts in the coupling of iodobenzene
with styrene
Yield (%)
Entry
Catalyst (mol% of Pd)
Conditions
a
1
2
Pd/MFC (30 mg, Pd: 0.308 mol %)
Fe3O4/SiO2/HPG-OPPh2-PNP (1.14 mol%
of Pd)
K2CO3, DMF, 120 ºC, 1 h
K2CO3, DMF, 100 ºC, 1 h
66[50]
87[13a]
71[51]
NaOAc, CH3CN/H2O, reflux, 12
h
3
Fe3O4/SiO2/NH2-Pd (30 mg)
4
5
6
7
[Pd(NH3)4]2+-NaY (0.1mol % Pd)
[MePPh3]2[Pd2Br2Cl4] (0.04 mmol)
Pd/Fe3O4@C (30 mg, Pd: 0.308 mol %)
palladium supported/PAEIP (30mg)
NaOAc, DMF, 140 ºC, 20 h
NaHCO3, DMF, 140 ºC, 12 h
K2CO3, DMF,120 ºC, 2 h
Et3N, Dioxane, 100ºC, 24 h
triethanolamine, 100 ºC, reflux,
10 h
85[52]
58[53]
66[50]
84[54]
8
9
Pd-LHMS-3 (50 mg Pd)
MNPs-TDA-Pd (20 mg)
85[55]
93
K2CO3, DMF,100 ºC, 8 h
This work
a Isolated yield.
19

ACCEPTED MANUSCRIPT
1. Synthesis and characterization of a new hybrid metal-organic nanoparticles (core/shell
nanostructure)
2. Highly efficient C-C cross-coupling (Mizoroki-Heck) reaction
3. Good to excellent yields alongside the simplicity of the methodology
4. Isolation of highly pure products without chromatography techniques
5. High efficiency and reusability of catalyst