Pd nanoparticles supported on reduced graphene oxide as an effective and reusable heterogeneous catalyst for the Mizoroki–Heck coupling reaction

Article abstract of DOI:10.1002/aoc.5524

A general method for the synthesis of palladium nanoparticles loaded on reduced graphene oxide functionalized with diethylenetriamine (PdNPs/rGO-NH₂) using a sonochemical procedure is described. The heterogeneous nanocomposite was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, thermogravimetric analysis, high-angle annular dark field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, UV–visible absorption, and inductively coupled plasma optical emission spectrometry. The PdNPs/rGO-NH₂ was very effective for the Mizoroki–Heck coupling reaction of several aryl iodide compounds with different alkenes in the presence of triethylamine. The reaction provides the coupling products in good to excellent yields (59–100%). Additionally, the PdNPs/rGO-NH₂ catalyst can be reutilized for six successive runs without any apparent diminution of its catalytic reactivity.

Full text of DOI:10.1002/aoc.5524

Received: 29 October 2019
DOI: 10.1002/aoc.5524
Revised: 12 December 2019
Accepted: 29 December 2019
F U L L P A P E R
Pd nanoparticles supported on reduced graphene oxide as
an effective and reusable heterogeneous catalyst for the
Mizoroki–Heck coupling reaction
1
1
2
Maryam Mirza-Aghayan
| Marzieh Mohammadi | Ahmed Addad
|
3
Rabah Boukherroub
1
Chemistry and Chemical Engineering
A general method for the synthesis of palladium nanoparticles loaded on
reduced graphene oxide functionalized with diethylenetriamine (PdNPs/rGO-
Research Center of Iran, PO Box
14335-186, Tehran, Iran
2
University of Lille, CNRS, UMR 8207 –
NH ) using a sonochemical procedure is described. The heterogeneous
2
UMET, F-59000, Lille, France
nanocomposite was characterized by Fourier transform infrared spectroscopy,
X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, ther-
mogravimetric analysis, high-angle annular dark field scanning transmission
electron microscopy, X-ray photoelectron spectroscopy, UV–visible absorption,
and inductively coupled plasma optical emission spectrometry. The
3
University of Lille, CNRS, Centrale Lille,
ISEN, Univ. Valenciennes, UMR 8520 -
IEMN, F-59000, Lille, France
Correspondence
Maryam Mirza-Aghayan, Chemistry and
Chemical Engineering Research Center of
Iran, PO Box 14335-186. Tehran, Iran.
Email: m.mirzaaghayan@ccerci.ac.ir
PdNPs/rGO-NH was very effective for the Mizoroki–Heck coupling reaction
2
of several aryl iodide compounds with different alkenes in the presence of
triethylamine. The reaction provides the coupling products in good to excellent
yields (59–100%). Additionally, the PdNPs/rGO-NH catalyst can be reutilized
2
for six successive runs without any apparent diminution of its catalytic reactivity.
K E Y W O R D S
diethylenetriamine, Mizoroki–Heck coupling reaction, palladium nanoparticles, reduced
graphene oxide
[
11a]
1
| INTRODUCTION
Schiff base-derived Pd catalysts
as homogenous cata-
lysts, mobil composition of matter-48 (MCM-48)
[13]
C–C bond formation is of essential importance in organic
synthesis
literature for this chemical process. Most of the useful
procedures for C–C bond formation involve Grignard,
supported 2-pyridinylmethanimine Pd catalyst,
supported ionic liquid phase Pd (SILP-Pd) catalysts,
and Pd nanoparticles loaded onto graphene derivatives
like heterogeneous catalysts have been investigated for
cross-coupling reactions. However, homogeneous Pd cat-
alysts face many difficulties, such as toxicity and low sta-
bility, difficulty in recovering, and a catalytic activity loss
due to their precipitation and aggregation in the form of
[1–3]
[14]
15]
and several methods are described in the
[
[
4]
[5]
[[6]
[7]
aldol,
Michael,
alkylation,
and cross-coupling
reactions mediated by metal catalysts, such as the
Suzuki–Miyaura,
Heck
extensively considered for cross-coupling reactions, but
the use of palladium catalysts has generated great atten-
tion because of their remarkable performance for this
reaction. Several homogenous and heterogeneous
palladium catalysts,
ter-bis(diphenylphosphinomethyl)amino ligands,
[8]
[9]
Sonogashira,
and Mizoroki–
[10]
reactions. Several metallic catalysts have been
[
16]
metallic palladium.
To overcome these serious hur-
dles, heterogeneous catalysts have been successfully
[
13–15]
employed in recent years.
Graphite oxide and graphene derivatives have been
successfully applied as efficient heterogeneous materials
for various chemical transformations.
[11]
+2
such as Pd
complex with
[12]
[17–22]
and
For instance,
Appl Organometal Chem. 2020;e5524.
wileyonlinelibrary.com/journal/aoc
© 2020 John Wiley & Sons, Ltd.
1 of 12
https://doi.org/10.1002/aoc.5524

2
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MIRZA-AGHAYAN ET AL.
Pd nanoparticles (PdNPs) loaded on graphene turned out
to be an effective catalyst in the Suzuki–Miyaura cou-
[15]
pling reaction.
Recently, we have investigated the use
of the palladium nanoparticles loaded on reduced
graphene oxide (PdNPs/rGO) nanocomposite in the pres-
ence of triethylsilane for the reduction of alcohol com-
SCHEME 2 Mizoroki–Heck coupling reaction
[
23]
pounds to their respective methylene derivatives.
In
[
19–22]
continuation of our investigation of graphite oxide
[23]
and its derivatives,
we report a general method for the
temperature. The resulting solution was centrifuged
and washed sequentially with ethanol, methanol, and
preparation of PdNPs loaded on reduced graphene oxide
functionalized with diethylenetriamine (PdNPs/rGO-
NH ). The PdNPs/rGO-NH material was identified by
acetone. The rGO-NH was obtained by dehydration at
2
room temperature overnight.
2
2
different analytical tools and its catalytic activity was
examined for C–C bond formation via the Mizoroki–
Heck coupling reaction (Schemes 1 and 2).
2
.2 | Preparation of PdNPs/rGO-NH2
material
A suspension of 200 mg of rGO-NH2 in 200 ml of
2
2
| EXPERIMENTAL
deionized H O was dispersed by an ultrasonic cleaning
unit for 120 min at room temperature. Then 10 ml of GO
2
.1 | Preparation of rGO-NH2
dispersion in 100 ml of deionized H O was mixed for
2
20 min using an ultrasonic cleaning unit. Next, 4 ml of
A mixture of diethylenetriamine (500 mg, 5 mmol) and
GO (50 mg) in 50 ml of ethanol was sonicated using an
Elmasonic P ultrasonic cleaning unit for 3 hr at ambient
H PdCl4 solution, obtained by fully dissolving PdCl2
(177 mg) in 100 ml of 20 mM HCl solution, was intro-
duced into this mixture and sonicated for 40 min by an
2
SCHEME 1 Preparation of heterogeneous PdNPs loaded onto rGO functionalized with diethylenetriamine nanocomposite

MIRZA-AGHAYAN ET AL.
3 of 12
ultrasonic homogenizer. PdNPs/rGO-NH was obtained
be noted that ultrasound can generate a cavitation bubble
where the reactants that entered during its formation are
subjected to extreme conditions of temperature and pres-
sure on collapse, leading to chemical reaction between
them. This cavitation bubble collapse provides the energy
needed for a chemical reaction. As shown in Scheme 1,
2
by centrifugation, washed with deionized H O, filtered,
2
ꢀ
and dehydrated in an oven at 80 C for 120 min.
2
.3 | General method for the Mizoroki–
rGO-NH was synthesized from the direct reaction of GO
2
Heck reaction
with diethylenetriamine using ultrasonic irradiation. The
mechanical effect of ultrasound provides the energy
needed for this chemical reaction. By addition of H PdCl
−3
PdNPs/rGO-NH nanocomposite (4 mg, 6.4 × 10 mmol)
2
was added to a solution of aromatic iodide compound
2
4
(
(
0.5 mmol), alkene (1 mmol), and triethylamine (Et N)
to rGO-NH2, the heterogeneous PdNPs/rGO-NH2
nanocomposite was effectively formed. The PdNPs/rGO-
3
2 mmol) in dimethylformamide (DMF) (2 ml) as solvent.
ꢀ
The resulting solution was reacted at 120 C for 4 hr prior
to gas chromatographic analysis. For catalyst separation,
the mixture was centrifuged and washed with ethanol and
then dried under vacuum for reuse. The organic solution
was extracted with ethyl acetate (3 × 20 ml) and dried over
MgSO . The solvent was evaporated and the crude mixture
was isolated by column chromatography with hexa-
ne/ethyl acetate (8/1). The known products were identified
NH material was fully identified by FT-IR, X-ray diffrac-
2
tion (XRD), scanning electron microscopy (SEM), energy
dispersive X-ray (EDX), thermogravimetric analysis
(TGA), high-angle annular dark field scanning transmis-
sion electron microscopy (HAADF-STEM), X-ray photo-
electron spectroscopy (XPS), transmission electron
spectroscopy (TEM), UV–visible absorption, and induc-
tively coupled plasma optical emission spectrometry
(ICP-OES).
4
1
by H NMR and the unknown products were fully identi-
1
13
fied by H and C NMR, mass spectroscopy and Fourier
transform infrared (FT-IR) spectroscopy. All data are pres-
ented in the Supporting Information Data S1 file.
The FT-IR spectra of the starting GO, rGO-NH , and
2
PdNPs/rGO-NH2 nanocomposite are depicted in
Figure 1. The FT-IR spectrum of GO displays characteris-
tic stretching vibrations at 1726 cm– (C=O in carbonyl
1
Methyl (E)-3-(ferrocenyl)acrylate (entry 5, Table 2);
1
–1
H NMR (500 MHz, CDCl ): δ = 3.78 (s, 3H, OCH ), 4.17
and carboxylic acid groups), 1622 cm (C=C in an
3
3
–
1
–1
(
6
s, 5H, (C H ), 4.42 (m, 2H, C H ), 4.50 (m, 2H, C H ),
aromatic ring), 1380 cm (C–OH), 1200 cm , and
5
5
5
4
5
4
1045 cm– (C–O in epoxy and alkoxy groups, respectively)
1
.05 (d, J = 15.7 Hz, 1H, CH), 7.59 (d, J = 15.7 Hz, 1H,
13
[24]
CH); C NMR (125 MHz, CDCl ): δ = 51.74, 68.89,
6
(
(Figure 1a).
The spectrum of rGO-NH reveals broad
3
2
–1
9.92, 70.92, 114.69, 146.20, 150.77, 167.53; MS
peaks at about 2918, 2863, and 1453 cm ascribed to the
stretching vibrations of the CH2 groups in die-
thylenetriamine. The presence of new peaks at 1112 and
1063 cm– (C–N stretching vibrations) in the FT-IR spec-
+
EI) (70 eV), m/z (%): 270 (100) [M] , 239 (6) [M-
+
OCH ] , 205 (63), 175 (32), 147 (7), 121 (25), 89 (12),
3
1
5
1
6 (14); IR (KBr): v = 2946, 1713, 1630, 1435, 1352, 1307,
–
1
193, 1158, 1030, 975, 805, 475 cm .
E)-3-(Ferrocenyl)acrylate (entry 7, Table 2); H NMR
500 MHz, CDCl ): δ = 1.36 (t, J = 7.1 Hz, 3H, CH ), 4.17
trum of rGO-NH indicates amide and/or amine bond
2
1
[25]
(
formation (Figure 1b).
A significant decrease in the
peaks at 1726 and 1200 cm– was observed, suggesting
partial elimination of the oxygen groups and restoration
of the graphenic structure. This is corroborated by the
1
(
3
3
(s, 5H, (C H ), 4.24 (q, J = 7.1 Hz, 2H, OCH ), 4.42 (m,
5 5 2
2
H, C H ), 4.50 (m, 2H, C H ), 6.04 (d, J = 15.7 Hz, 1H,
5 4 5 4
13
–1
CH), 7.58 (d, J = 15.7 Hz, 1H, CH); C NMR (125 MHz,
presence of a band at 1636 cm that can be attributed to
CDCl ): δ = 167.55, 145.87, 115.79, 70.95, 69.98, 68.54,
C=C stretching vibrations in aromatic ring, indicating
incomplete restoration of the graphene network in this
procedure (Figure 1b). The FT-IR spectrum of the
3
+
6
2
2
5
1
0.14, 14.33; MS (EI) (70 eV), m/z (%): 284 (100) [M] ,
+
+
56 (32) [M-1-C H ] , 239 (9) [M-OC H ] , 219 (23),
2
5
2
5
07 (35), 191 (23), 175 (24), 145 (11), 121 (26), 89 (17),
PdNPs/rGO-NH material depicts typical bands at 3408,
2
1620, 1404, and 1040 cm– ascribed to the stretching
vibrations of OH, C=C, NH, and C–O groups, respec-
tively (Figure 1c). It should be noted that the
bonding between Pd and rGO can take place through
hydrogen bonding or van der Waals forces with the –OH,
1
6 (15); IR (KBr): v = 2918, 2850, 1703, 1636, 1464, 1366,
–1
314, 1205, 1037, 812, 479 cm .
3
3
| RESULTS AND DISCUSSION
.1 | Characterization of the
–
COOH, –NH, and C=O groups on the functionalized
[
26,27]
rGO-NH2.
PdNPs/rGO-NH material
2
Figure 2 displays the XRD patterns of rGO-NH and
2
Ultrasonic irradiation was successfully applied for the
PdNPs/rGO-NH2 nanocomposite. The XRD pattern of
GO exhibits a distinct and characteristic peak at
synthesis of PdNPs/rGO-NH nanocomposite. It should
2

4
of 12
MIRZA-AGHAYAN ET AL.
FIGURE 1 FT-IR transmission spectra of
(
a) GO, (b) rGO-NH
2 2
, and (c) PdNPs/rGO-NH
nanocomposite
the reaction of GO with diethylenetriamine using ultra-
sonic irradiation (Figure 3d–f). The EDX spectrum of
rGO-NH2 clearly shows the presence of nitrogen
(
11.72 at%), which indicates the grafting of amino groups
on the rGO sheet using this procedure (Figure 3e). EDX
examination of the PdNPs/rGO-NH material reveals the
2
presence of Pd (Figure 3f). The palladium loading on
PdNPs/rGO-NH2 nanocomposite is estimated to be
25.46 wt% by EDX analysis (Figure 3f). This value is
slightly higher than the 17.86 wt% (1.60 mmol/g) deter-
mined by ICP-OES analysis.
Figure 4 shows the thermogravimetric analysis (TGA)
curves of GO and rGO-NH materials. The weight loss of
2
GO takes place in three consecutive steps: a weight loss
ꢀ
of ~6% at around 106 C (desorption of H O molecules),
2
ꢀ
3
0% at 106–210 C (decomposition of organic functional
groups), and 22% in the temperature range of 210–900 C
ꢀ
due to the decomposition of the carbon skeleton
[
23]
2
FIGURE 2 XRD patterns of (a) rGO-NH and (b) PdNPs/rGO-
(
Figure 4a).
The weight loss of rGO-NH material,
2
NH
2
nanocomposite
which is very similar to GO, also comprises three consec-
utive steps: a weight loss of ~6% at ~106 C which can be
attributed to the dehydration of adsorbed H O molecules,
a second weight loss of 22% (106–210 C) due to the
ꢀ
ꢀ
[28]
2
θ = 11.8 (data not shown).
The XRD pattern of rGO-
2
ꢀ
ꢀ
NH depicts a characteristic peak at 2θ = 11.8 for GO
and a wide peak at about 2θ = 26 due to the presence of
2
ꢀ
decomposition of the labile functional groups such as
reduced graphene oxide (rGO) by elimination of oxygen-
epoxy, OH, C=O, COOH, and NH, and a final step of a
weight loss of 21% (210–900 C), which can be attributed
to the combustion of the carbon frame (Figure 4b).
HAADF-STEM images of PdNPs/rGO-NH2 are
depicted in Figure 5. High-angle annular dark field scan-
ning transmission electron microscopy (HAADF-STEM)
and high-angle annular dark field scanning transmission
electron microscopy and energy dispersive X-ray
(HAADF-STEM-EDX) elemental mapping were investi-
gated to explore the elemental distribution of
[29,30]
ꢀ
ated functional groups
(Figure 2a). The XRD of
ꢀ
ꢀ
PdNPs/rGO-NH consists of peaks at 2θ = 40.01 , 46.54 ,
2
ꢀ
and 67.93 attributed, respectively, to the (111), (200),
and (220) crystalline planes of Pd (Figure 2b), confirming
0
[29,30]
the presence of Pd in the nanocomposite.
It also
ꢀ
includes a wide peak at 2θ = 26 , indicating the existence
of rGO by elimination of oxygenated functional
[31]
groups.
Figure 3 depicts SEM images along with EDX analy-
sis. The comparison of the EDX analyses of GO and rGO-
PdNPs/rGO-NH nanocomposite. The results showed five
2
NH reveals that chemical changes have occurred during
dominant elements (Pd, C, O, Cl, and N) present in the
2

MIRZA-AGHAYAN ET AL.
5 of 12
2 2
FIGURE 3 The SEM images of (a) GO, (b) rGO-NH , and (c) PdNPs/rGO-NH material, and (d)–(f) their relevant EDX spectra
PdNPs/rGO-NH material. The presence of N and Pd
2
indicates that diethylenetriamine and palladium are
homogeneously distributed on the rGO surface, in com-
plete agreement with EDX analysis.
TEM imaging of the synthesized PdNPs/rGO-NH2
revealed exfoliated rGO sheets which are coated homoge-
neously with PdNPs of 2.1 nm average size (Figure 6). By
focusing on the nanocomposite, crystallized PdNPs were
observed. Additionally, high resolution transmission elec-
tron microscopy (HRTEM) analysis of a single Pd nano-
particle revealed lattice fringes with a d-spacing of
0
.23 nm, which correspond to the {111} lattice planes of
the face-centered cubic (fcc) structure of Pd.
The elemental composition of
nanocomposite was identified by XPS (Figure 7). The
rGO-NH2
2
FIGURE 4 TGA analysis of (a) GO and (b) rGO-NH material

6
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MIRZA-AGHAYAN ET AL.
FIGURE 5 (a) HAADF-STEM image and (b)–(f) HAADF-STEM-EDX elemental mapping of Pd, C, O, Cl, and N elements in
PdNPs/rGO-NH nanocomposite
2
2
FIGURE 6 The TEM imaging of PdNPs/rGO-NH nanocomposite. The inset corresponds to HRTEM of a single Pd nanoparticle
XPS wide-scan of rGO-NH2 composite contains three
peaks at ~285, 400, and 533 eV assigned to C , N , and
and 19.98 at%, respectively. This result confirms the pres-
ence of N in this composite and is in complete agreement
with EDX analysis. The XPS wide-scan spectrum of
PdNPs/rGO-NH2 nanocomposite contains six peaks at
about 200, 285, 342, 400, 533 and 565 eV due to Cl , C ,
1s
1s
[25]
O , respectively (Figure 7a).
1s
The atomic composition
of rGO-NH composite consists of carbon (71.0 at%), oxy-
2
gen (21.4 at%), and nitrogen (7.5 at%). As presented in
Figure 7b, the XPS high resolution of the N1s spectrum
2
p
1s
[
32]
Pd , N , O , and Pd p, respectively (Figure 7c),
in
3d
1s
1s
3
was deconvoluted into three peaks attributed to C–N
agreement with EDX analysis. The atomic percentages
are 69.12 at% (C), 24.33 at% (O), 4.45 at% (N), and
2.09 at% (Pd). The XPS high-resolution spectrum of the
+
(
397.7 eV), N–H (399.8 eV), and NH
(401.8 eV)
3
[25]
bonds,
with atomic percentages 32.50 at%, 47.61 at%,

MIRZA-AGHAYAN ET AL.
7 of 12
FIGURE 7 (a) The XPS wide-
scan and (b) the high-resolution
spectrum of the N1s of rGO-NH
c) the XPS wide-scan and (d) the
high-resolution spectrum of the Pd3d
of PdNPs/rGO-NH nanocomposite
2
,
(
2
2
+
0[14,38]
Pd3 is deconvoluted into two components assigned to
mixture of Pd /Pd
reaction.
catalyst for the Mizoroki–Heck
d
2
+
0
Pd
(337.3 and 342.9 eV) and Pd (335.4 and
[33]
2+
0
3
40.4 eV)
with a Pd /Pd ratio of 3.02, suggesting that
The UV–visible (UV–Vis) absorption spectra of GO,
palladium is dominantly in 2+ form along with a quan-
tity of metallic Pd (Figure 7d). The XPS results
rGO-NH , PdCl , and PdNPs/rGO-NH are shown in
2
2
2
0
Figure 8. The UV–Vis spectrum of GO dispersion in H O
2
established the presence of palladium in PdNPs/rGO-
shows one major peak at ~230 nm and a weak peak at
NH nanocomposite, which is in total accordance with
~310 nm due to π–π* absorption of C=C bonds and n–π*
2
[
39,40]
the EDX analysis. It should be noted that there have been
absorption of C=O bonds, respectively
(Figure 8a).
2+[12,34–37]
several reports concerning the use of Pd
or a
The UV–Vis spectrum of rGO-NH dispersion (Figure 8b)
2
FIGURE 8 UV–Vis spectra of (a) GO,
(
2 2
b) rGO-NH , (c) PdCl , and (d) PdNPs/rGO-
NH material
2

8
of 12
MIRZA-AGHAYAN ET AL.
depicts a peak at ~260 nm, which confirms the chemical
carbonate as base for this coupling reaction (entries 1–7,
Table 1). The results reveal that the C–C coupling reac-
tion is dependent on the nature of the solvent; the yield
[29,30]
change in this material with respect to GO.
The
UV–Vis spectrum of PdCl2 displays peaks at ~210,
[41]
2
40, 300, and 425 nm (Figure 8c).
The UV–Vis spec-
of methyl cinnamate was higher when the reaction was
ꢀ
ꢀ
trum of PdNPs/rGO-NH2 nanocomposite comprises
peaks at ~210 and 240 nm (Figure 8d). The disappearance
of the peak at 425 nm as a result of the interaction of the
surface of the substrate with the metal confirms the com-
conducted in DMF as a polar solvent and Et N at 120 C
3
(entry 5, Table 1). Reducing the temperature to 100 C
leads to a decrease of the yield of methyl cinnamate to
ꢀ
90% (entry 8, Table 1), indicating that 120 C is optimal
[42]
plexation of palladium by the substrate.
for the Mizoroki–Heck coupling reaction under our
experimental conditions. Decreasing the amount of
PdNPs/rGO-NH nanocomposite catalyst to 3 mg was
2
3
.2 | Catalytic performance of
accompanied by a decrease in the reaction yield to 80%
(entry 7, Table 1), suggesting that 4 mg of PdNPs/rGO-
NH2 nanocomposite is required for this coupling
reaction.
Using the optimized conditions, several aromatic iodo
compounds (0.5 mmol), including iodobenzene,
4-iodotoluene, 4-iodoanisole, 2-iodothiophene, and
iodoferrocene, reacted with different alkenes (1 mmol)
such as methyl, ethyl, and butyl acrylate, acrylic acid,
and styrene in the presence of PdNPs/rGO-NH2
PdNPs/rGO-NH nanocomposite
2
In
continuation
of
our
investigation
in
[
19–23,28,41]
catalysis,
we assessed the efficacy of
PdNPs/rGO-NH nanocomposite as a heterogeneous cat-
2
alyst for C–C bond formation via the Mizoroki–Heck
cross-coupling reaction of aromatic halides with alkenes.
The synthesis of methyl cinnamate from the reaction of
iodobenzene (0.5 mmol) with methyl acrylate (1 mmol)
in the presence of PdNPs/rGO-NH2 nanocomposite
nanocomposite (4 mg) in DMF (2 ml) and Et N (2 mmol)
3
ꢀ
(4 mg) was selected to optimize the coupling reaction.
at 120 C to give the corresponding coupling compounds
The results obtained for this reaction, under several
conditions, are shown in Table 1. We first examined the
influence of methanol, ethanol, acetonitrile, water,
N-methyl-2-pyrrolidone (NMP), and DMF as solvent and
via the Mizoroki–Heck coupling reaction (Table 2).
The results reveal that the reaction of iodobenzene,
4-iodotoluene, 4-iodoanisole, 2-iodothiophene, and
iodoferrocene with methyl acrylate was successfully per-
formed and the related coupling compounds were formed
in high yields (69–100%) (entries 1–5, Table 2). It should
be noted that the reaction of iodoferrocene with methyl
acrylate takes place in high yield via the Mizoroki–Heck
coupling reaction to produce new C–C bonds between
the ferrocene group and methyl acrylate (entry 5, Table 2).
We examined this coupling reaction for ethyl acrylate.
The results indicate the high yield (95 and 83%) of cou-
pling products for the reaction of 4-iodotoluene and
iodoferrocene with ethyl acrylate, respectively (entries
6–7, Table 2). Next, we investigated the coupling reaction
of butyl acrylate with aryl iodide using PdNPs/rGO-NH2
nanocomposite. We observed the formation of C–C bonds
via Mizoroki–Heck coupling of butyl acrylate with
iodobenzene, 4-iodotoluene, and 4-iodoanisole in 96%,
2
mmol of Et N, sodium hydroxide or potassium
3
TABLE 1 Different conditions for the Mizoroki–Heck
coupling reaction
a
Temperature
( C)
GC yield
(%)
ꢀ
Entry Solvent Base
1
2
3
4
5
6
7
8
9
MeOH
EtOH
Et
Et
Et
Et
Et
3
3
3
3
3
N
N
N
N
N
Reflux
Reflux
Reflux
120
38
61
CH
3
CN
90
94%, and 98% yield, respectively (entries 8–10, Table 2). It
NMP
DMF
DMF
DMF
DMF
DMF
97
should be noted that the reaction of iodoferrocene with
butyl acrylate provided the corresponding coupling
compound in trace even after a prolonged time of 17 hr
120
100
89
NaOH
CO
120
ꢀ
K
2
3
120
81
at 120 C.
Similarly, the reaction of acrylic acid with
Et
3
N
N
100
90
b
iodobenzene and 4-iodotoluene produced cinnamic acid
and 3-(p-tolyl)acrylic acid in 95% and 92% yield, respec-
tively (entries 11–12, Table 2). Finally, we investigated
the cross-coupling of styrene with iodobenzene and
4-iodoanisole; the results revealed the synthesis of the
Et
3
120
80
DMF, dimethylformamide; GC, gas chromatography; NMP,
N-methyl-2-pyrrolidone.
a
Obtained by GC analysis with 1,4-dimethylbenzene as internal standard.
b
Using 3 mg of catalyst.

MIRZA-AGHAYAN ET AL.
9 of 12
TABLE 2 Mizoroki–Heck cross-coupling reaction of iodo and bromo compounds and different alkenes catalyzed by heterogeneous
PdNPs/rGO-NH
2
nanocomposite
a,b
Entry
Ar
X
R
Product
GC yield (%)
1
C
6
H
5
I
COOMe
100
2
3
4
4-Me-C
6
H
5
I
I
I
COOMe
COOMe
COOMe
95
4-OMe-C
6
H
5
98
C
4
SH
3
69
5
(C
5
H
5
)Fe(C
5
H
4
)
I
COOMe
91
6
7
4-Me-C
6
H
5
I
I
COOEt
COOEt
95
83
(C
5
H
5
)Fe(C
5
H
4
)
c
8
C
6
H
5
I
I
I
I
I
I
COOBu
COOBu
COOBu
COOH
COOH
96
94
98
95
92
c
9
6 5
4-Me-C H
c
1
1
1
1
0
1
2
3
4-OMe-C
6
H
5
c
c
c
6 5
C H
4-OMe-C
6
H
5
d
C
6
H
5
C
6
H
5
96 (15/1)
(
Continues)

10 of 12
MIRZA-AGHAYAN ET AL.
TABLE 2 (Continued)
a,b
Entry
Ar
4-OMe-C
X
R
Product
GC yield (%)
c
d
1
4
6
H
5
I
C
6
H
5
76 (12/1)
e
f
1
5
6
C
C
6
6
H
H
5
5
Br
Br
COOMe
COOBu
59
64
1
GC, gas chromatography.
a
ꢀ
Reaction conditions: aromatic iodo compound (0.5 mmol), alkene (1 mmol), Et
3
N (2 mmol), and 4 mg PdNPs/rGO-NH
2
catalyst in 2 ml of DMF at 120 C for
4
b
hr.
Obtained by GC analysis with 1,4-dimethylbenzene as internal standard.
c
0.75 mmol of alkene was used.
d
The number in parentheses corresponds to the ratio of trans/cis coupling compound.
e
The reaction was performed with bromobenzene for 8 hr.
The reaction was performed with bromobenzene for 10 hr.
f
related coupling compounds in 96% and 76% yield,
respectively (entries 13–14, Table 2).
otherwise identical conditions, the corresponding product
was formed in trace after 24 hr. We conclude that our
method is better suited for aromatic iodo compounds.
This observation is in line with literature data indicating
that the Mizoroki–Heck coupling reaction yield is high
To broaden the scope of the reaction, we investigated
the Mizoroki–Heck coupling reaction of methyl and butyl
acrylate with bromobenzene under our optimized condi-
tions. The results indicated that the coupling products,
that is, methyl and butyl cinnamate, were formed in 59%
and 64% yield after 8 and 10 hr, respectively (entries
[
43–46]
for iodo compounds.
The results obtained using PdNPs/rGO-NH2
nanocomposite catalyst are comparable to those reported
[
12,34–36,47]
1
5–16, Table 2). It should be noted that when the cou-
in the literature.
co-workers
For example, Basak and
[
47]
pling reaction was performed with chlorobenzene under
prepared methyl and butyl (E)-
FIGURE 9 Recycling efficiency of
heterogeneous PdNPs/rGO-NH nanocomposite
catalyst in a coupling reaction between
2
ꢀ
iodobenzene with methyl acrylate at 120 C for
hr
4

MIRZA-AGHAYAN ET AL.
11 of 12
3
-(4-methoxyphenyl)acrylate in 85% yield by a coupling
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ꢀ
1
00 C after 4 hr. The same products were synthesized
[
using PdNPs/rGO-NH nanocomposite catalyst in 98%
yield (entries 3 and 10) in the presence of Et N after 4 hr
at 120 C.
To estimate the reusability of the catalyst, the
coupling reactions were executed several times with
methyl acrylate and iodobenzene in DMF catalyzed by
2
3
ꢀ
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2
catalyst. When the reaction was complete, the catalyst
was recovered by centrifugation and washed with ethanol
and dried in vacuum for reuse. The recovered heteroge-
neous catalyst was consecutively exposed to the a further
five runs of the cross-coupling reaction using identical
reaction conditions to the initial run. The results indicate
[
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14] B. Urbán, D. Srankó, G. Sáfrán, L. Ürge, F. Darvas, J. Bakos,
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that the recovered PdNPs/rGO-NH catalyst is competent
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for the cross-coupling reaction of methyl acrylate and
iodobenzene into methyl cinnamate in 91% yield even
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| CONCLUSION
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18] M. Spiro, Catal. Today 1990, 7, 167.
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R. Boukherroub, Ultrason. Sonochem. 2015, 22, 359.
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Tetrahedron Lett. 2014, 55, 342.
A general and efficient procedure was established for the
preparation of palladium nanoparticles loaded onto
diethylenetriamine-functionalized rGO (PdNPs/rGO-
[
NH ) nanocomposite using an ultrasonic method. The
[21] M. Mirza-Aghayan, M. Alizadeh, M. M. Tavana,
2
R. Boukherroub, Tetrahedron Lett. 2014, 55, 6694.
structure and chemical composition of the PdNPs/rGO-
[
[
22] M. Mirza-Aghayan, M. M. Tavana, R. Boukherroub,
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NH nanocomposite were fully characterized by several
2
methods. The PdNPs/rGO-NH material was successfully
2
utilized as a heterogeneous catalyst for the coupling
reaction of several aromatic iodo and bromo compounds
with different alkenes via the Mizoroki–Heck reaction.
Furthermore, the heterogeneous catalyst was reused for
six successive runs without a significant diminution in its
catalytic reactivity. This novel and simple procedure is
valuable as the coupling reaction proceeds in great yields
in short times.
[
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