Formation of PdNiZn thin film at oil-water interface: XPS study and application as Suzuki-Miyaura catalyst

Article abstract of DOI:10.1002/aoc.4187

Nanosheet of PdNiZn and nanosphere of PdNiZn/reduced-graphene oxide (RGO) with sub-3?nm spheres have been successfully synthesized through a facile oil-water interfacial strategy. The morphology and composition of the films were determined by X-ray diffra

Full text of DOI:10.1002/aoc.4187

Received: 18 August 2017
DOI: 10.1002/aoc.4187
Revised: 17 October 2017
Accepted: 18 October 2017
F U L L P A P E R
Formation of PdNiZn thin film at oil‐water interface: XPS
study and application as Suzuki‐Miyaura catalyst
Parvin Fatahi | S. Jafar Hoseini
Department of Chemistry, Faculty of
Nanosheet of PdNiZn and nanosphere of PdNiZn/reduced‐graphene oxide
Sciences, Yasouj University, Yasouj
7591874831, Iran
(RGO) with sub‐3 nm spheres have been successfully synthesized through a fac-
ile oil‐water interfacial strategy. The morphology and composition of the films
were determined by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy
Correspondence
S. Jafar Hoseini, Department of Chemistry,
Faculty of Sciences, Yasouj University,
Yasouj 7591874831, Iran.
(
(
XPS), transmission electron microscopy (TEM), scanning electron microscopy
SEM), energy dispersive analysis of X‐ray (EDAX) and elemental mapping. In
Email: jhosseini@yu.ac.ir;
sjhoseini54@yahoo.com
the present study, we have developed a method to minimize the usage of pre-
cious Pd element. Due to the special structure and intermetallic synergies, the
PdNiZn and PdNiZn/RGO nanoalloys exhibited enhanced catalytic activity
and durability relative to Pd nanoparticles in Suzuki‐Miyaura C‐C cross‐cou-
pling reaction. Compared to classical cross‐coupling reactions, this method
has the advantages of a green solvent, short reaction times, low catalyst loading,
high yields and reusability of the catalysts.
KEYWORDS
graphene oxide, oil‐water interface, Suzuki‐Miyaura catalyst, thin film, trimetallic alloy nanosheets
1
| INTRODUCTION
encouraged our group to investigate new strategies for
the synthesis of ultrathin trimetallic alloy structures like
Trimetallic nanoparticles (NPs) alloy have attracted
increasing interest due to their special morphology, size
and high surface‐ to‐ volume ratios. Enormous effort
nanosheets or nanospheres. Nanosheets have attracted
intensive interest due to their wide range of applica-
tions. To obtain these structures, generally specific con-
[1]
[7]
has been dedicated to the synthesis of multimetal alloys
ditions should be applied such as using stabilizers or
capping agents to control the growth process. Bao and
[2]
[8]
due to their various advantages. A higher degree of
selectivity, higher activity and chemical/physical stability
are some of the advantages of trimetallic nanoalloys com-
pare to their monometallic or even bimetallic counter-
Tang et al. have synthesized ultrathin Pd nanosheets by
[
9,10]
using surfactants.
Till now, there are limited reports
on the one‐step synthesis of ultrathin trimetallic nano-
sheets or NPs in the absence of stabilizers. Kang et al.
have synthesized Au@PdPt NPs with high catalytic activ-
[3,4]
parts.
Ultrathin noble metal nanocrystals have a
potential to exhibit novel properties, especially in the area
of catalysis which is related to their high specific surface
[11]
ity in the presence of ascorbic acid and hydrazine.
Wu
[5]
area. Tremendous efforts have been dedicated to the
synthesis of ultrathin nanostructures of noble metals
which is limited in comparison with nanostructures of
et al. have synthesized Au nanostructures on pre‐formed
[
12]
PtNi nanostructures in two steps.
Among trimetallic
nanocrystals, Pd‐based nanocatalysts have attracted atten-
[6]
metal hydroxides or sulfides.
The importance of
tion because of their physical and chemical performances
[
13]
trimetallic alloys as a catalyst in one hand and the impor-
tance of ultrathin nanostructures on the other hand,
compare to pure Pd or its bimetallic nanoalloys.
Palla-
dium components are the best choice catalysts for various
Appl Organometal Chem. 2017;e4187.
wileyonlinelibrary.com/journal/aoc
Copyright © 2017 John Wiley & Sons, Ltd.
1 of 11
https://doi.org/10.1002/aoc.4187

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FATAHI AND JAFAR HOSEINI
[
33]
cross‐coupling reactions, such as the Suzuki–Miyaura
reaction (one of the most important synthetic transforma-
tions developed in the twentieth century) which exhibits a
key role for the synthesis of symmetrical and unsymmet-
reported procedure.
The powder X‐ray diffraction pat-
terns (XRD) were obtained by a Bruker AXS (D8,
Advance) instrument employing the reflection Bragg–
Brentano geometry with Cu‐Kα radiation. Transmission
electron microscopy (TEM) images were collected with a
JEOL JEM‐3010 with an accelerating voltage of 300 kV.
The elemental composition of the compounds and scan-
ning electron microscopy (SEM) images were obtained
from Nova Nano SEM 600, FEI company. X‐ray photo-
electron spectroscopy (XPS) spectra were recorded in an
Omicron Nanotechnology Spectrometer with Mg Kα as
[14]
rical biaryl compounds.
Pd components have a high
activity for a wide range of substrates but they suffer from
leaching or aggregation after few cycles of the reaction
[15]
progress.
Furthermore, high‐cost and scarcity of Pd
encourage the researchers to replace Pd partially or
completely with low‐costing metals. Several recent inves-
tigations evidenced the importance of bimetallic NP cata-
lysts, such as PdAu, PdNi, PdZn and PdCu as effective
1
the X‐ray source. H NMR spectra were obtained with a
[16–19]
catalysts for the Suzuki–Miyaura reaction.
Among
Bruker 400 MHz Ultra‐shield spectrometer in CDCl3.
Infrared spectra were recorded with a JASCO FT/IR‐680
plus spectrometer.
the Pd alloy catalysts, alloys with lower metal costs and
abundantly available metals (Ni and Zn) are extracted
more attention. In C‐C cross‐coupling catalytic reactions,
the main facts that affect the catalytic activity are struc-
ture and electronic properties. Therefore, besides the com-
ponents, the size and surface morphology facts have an
2
.2 | Preparation of the PdNiZn/RGO thin
film at toluene–water interface
[20]
important role.
Nanostructures with different mor-
phologies exhibit different atomic arrangements on the
surface resulting in distinct electronic and geometric
Graphene oxide (GO) was synthesized from graphite pow-
der by using modified Hummers method (supporting
[21]
[34,35]
structures which improve the catalytic activity.
In this
information file)
and characterized by FE‐SEM,
study, we highlight a new developed method for the syn-
thesis of ultrathin trimetallic alloys with promising cata-
lytic activity in Suzuki‐Miyaura reaction as expanded by
XRD and FT‐IR techniques (Figures S1‐S3). In the case
of formation of PdNiZn/RGO at the interface of two
immiscible liquids, according to Scheme 1a, in the first
step GO (10 mg) was exfoliated and dispersed in 25 mL
of distilled water by using ultrasonic waves for 10 min.
Toluene solution (25 ml) contain an equimolar solution
of [PdCl (cod)], [Ni(acac) ] and [Zn(acac) ] (acac = ace-
[22–32]
Rao's group and us.
2
2
2
2
2
| EXPERIMENTAL
tylacetonate) (0.33 mM) was prapared and sonicated for
0 min (Scheme 1a, yellow solution). This solution was
1
.1 | Materials and methods
contacted with aqueous solution contain GO in a beaker
(100 ml) (Scheme 1b). After the stabilization of toluene
and water layers, sodium borohydride aqueous solution
(10 ml, 0.1 M) was injected by a syringe (Scheme 1c).
All of the chemical compounds were purchased from
Merck and Sigma‐Aldrich Companies. The [PdCl (cod)]
2
(cod = cis, cis‐1,5‐cyclooctadiene) was synthesized using
SCHEME 1 Schematic illustration of
the formation of PdNiZn/RGO trimetallic
nanoalloy thin film at the interface
between toluene and water, (a) dispersion
of GO in water and metallic precursors in
toluene, (b) stabilized mixture of
2 2 2
[PdCl (cod)], [Ni(acac) ] and [Zn(acac) ]
complexes in toluene (top phase, yellow)
and GO in water (bottom phase, brown),
(
c) addition of the reducing agent to the
stabilized mixture, (d) movement of RGO
sheets and metallic NPs toward the
interface, (e) formation of the PdNiZn/
RGO thin film at the toluene‐water
interface after 24 h, (f) extraction of the
catalyst by removing the toluene (top
phase) by a dropper

FATAHI AND JAFAR HOSEINI
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1
Addition of NaBH leads to the reduction of both two
characterized using FT‐IR and H NMR spectra which is
in good agreement with the reported data. The details
are given in the Supporting Information file.
4
phases: metallic precursor reduction and GO reduction.
The functional groups on GO, which makes this com-
pound dispersible homogeneously in water, decreases
and makes it insoluble in water. This is the reason for
the movement of RGO sheets toward the interface
3
3
| RESULTS AND DISCUSSION
(
Scheme 2d). The produced RGO sheets and reduced
metallic NPs are self‐assembled at the interface
Scheme 2d). The reduction was begun by the color
.1 | Physicochemical characterization of
(
the catalysts
change of the toluene phase from yellow to colorless
which leads to the formation of the gray thin layer at
the interface. Finally, the aqueous and organic phases
below and above of the gray film were transparent
The as‐synthesized trimetallic nanoalloy Thin films were
characterized by XRD, XPS, FE‐SEM, TEM and EDAX‐
elemental mapping analysis. Figure 1(a, b) shows the
XRD patterns for the PdNiZn and PdNiZn/RGO thin
films, respectively. The five main diffraction peaks can
be assigned to [(111), (200), (220), (311) and (222)] indices
of face‐centred cubic (fcc) Pd(0) at 2θ = 40°, 48°, 68°, 82°,
The diffraction peaks with indices [(002), (100),
(101), (102), (103), (110) and (004)] confirm the presence
Other diffraction peaks, [(111), (200), (220)
and (311)] correspond to the Ni(0).
(Scheme 1e). For the extraction of the catalyst from the
interface, the toluene phase is removed by using a dropper
after 24 h, ethanol is added to the aqueous phase and cen-
trifuged (Scheme 1f). The obtained product can apply as
an efficient catalyst for the Suzuki‐Miyaura reaction. This
procedure is continued similarly for the synthesis of
PdNiZn trimetallic alloy thin film in the absence of GO
as a stabilizer in the aqueous phase. Also, the amount of
[
34]
86°.
[
18]
of Zn(0).
[
36]
Furthermore, in
aqueous NaBH is (5 ml, 0.1 M) in this step.
the XRD pattern of PdNiZn/RGO (Figure 1b), a clear dif-
4
fraction band was observed at 2θ ~ 25°, corresponding to
[
34]
the (002) plane of RGO.
Figure 2 (a, b) shows the FE‐SEM images of the
PdNiZn and PdNiZn/RGO trimetallic nanoalloy thin
films, respectively. Interestingly, PdNiZn has a sheet‐like
morphology which is consistent throughout the sample.
In the presence of RGO, the morphology of PdNiZn
trimetallic nanoalloy changes from nanosheet to ultrathin
nanospheres stabilized on RGO surface which is further
confirmed by TEM images. Figure 3a shows the TEM
image of PdNiZn alloy which has nanosheet like mor-
phology while in the case of PdNiZn/RGO (Figure 3b),
spherical ultrathin NPs is observable on the RGO surface
with the mean diameter of 3 nm (Figure 3c). It is interest-
ing that presence of GO changes the morphology of
2
.3 | General procedure for Suzuki‐
Miyaura reaction
Aryl halide (1.0 mmol) and phenylboronic acid (1.5 mmol)
were added to a round bottom flask containing the
trimetallic nanoalloy catalyst and K CO (2.0 mmol) in
distilled water (5.0 ml). The mixture was stirred in 80 °C
oil bath. After completion of the reaction (monitored by
thin layer chromatography (TLC)), dichloromethane (3
2
3
×
5 ml) was added to the reaction vessel. The organic
phase was separated and dried over anhydrous MgSO4.
Evaporation of the solvent leads to the formation of the
pure desired product. The obtained compounds were
SCHEME 2 Schematic illustration of formation of PdNiZn nanosheets and PdNiZn/RGO ultrathin spherical NPs at toluene‐water interface

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FATAHI AND JAFAR HOSEINI
FIGURE 1 XRD patterns of the (a) PdNiZn and (b) PdNiZn/RGO
trimetallic nanoalloy thin films deposited on a glass
FIGURE 2 FE‐SEM images of the (a) PdNiZn and (b) PdNiZn/
RGO trimetallic nanoalloy thin films
PdNiZn from nanosheet to spherical ultrathin NPs.
Scheme 2 exhibits the proposed mechanism.
reduction was followed by the reduction of the second
metal, (Ni(II)) (Scheme 2c), and Zn(II) to Zn (0) as a
third metal (Scheme 2d) due to their standard
electrode potentials. After the nucleation process
3.2 | Proposed mechanism for the
(
Scheme 2b,c,d), two routs are exist: In the case of
synthesis of PdNiZn nanosheets and
PdNiZn/RGO ultrathin spherical NPs
PdNiZn thin film (in the absence of GO), reduced Pd,
Ni and Zn were self‐assembled (Scheme 2e) and grew
In this study, PdNiZn thin film exhibits nanosheet struc-
ture whereas PdNiZn/RGO shows ultrathin spherical
NPs stabilized on RGO at the interfaces. Due to the dif-
ferent lattice structures of Pd and Ni (fcc), and Zn
with each other to form a nanosheet structure
(Scheme 2f) (route 1). In the case of PdNiZn/RGO,
simultaneous to nucleation process (Scheme 2b,c,d), GO
sheets are also reduced. GO sheets with hydroxyl, epox-
ide and carboxyl functional groups which make this
component hydrophile, lose its hydrophilicity due to
the reduction of these functional groups. The decrease
in the polar functionality is the driving force for the
(
hcp), different assembly and growth will happen. In
general, according to Scheme 2a, the reduction was initi-
ated by dropwise addition of NaBH and Pd precursor
4
reduced in the form of a sphere (Scheme 2b). This

FATAHI AND JAFAR HOSEINI
5 of 11
adsorb on the RGO surface at a time they formed and
stabilize on the RGO surface (Scheme 2h).
The composition of the PdNiZn nanosheets was inves-
tigated by EDAX analysis and elemental mapping
(
Figure 4a‐d). Also, Figure 4e shows the EDAX spectra
of PdNiZn/RGO trimetallic nanoalloy which shows the
presence of Pd, Ni, Zn and C in the sample.
PdNiZn alloy was further characterized by XPS. Figure 5
shows XPS spectra of Pd, Ni and Zn in PdNiZn alloy, the sig-
nal at 335.5 and 340.8 eV can be assigned corresponding to
the d5/2 and d3/2 states of Pd, respectively. The signal at
853.0 eV is corresponding to Ni 2p orbital, whereas signal
at 1020.16 is due to the Zn 2p orbitals (Figure 5a‐c).
The Pd, Ni and Zn loadings in the catalysts was obtained
using ICP that was 6.69% for Pd, 6.97% for Ni and 5.84% for
Zn in the case of PdNiZn nanosheets. Also, in the case of
PdNiZn/RGO ultrathin spherical NPs, the loading of Pd,
Ni, and Zn is 1.21%, 4.08% and 5.09%, respectively.
3
.3 | Investigating the catalytic activity of
trimetallic nanoalloy thin films
The PdNiZn nanosheet and PdNiZn/RGO ultrathin
spherical NP thin films were investigated for the Suzuki‐
Miyaura C‐C cross‐coupling reaction as the efficient
recoverable catalysts (Scheme 3).
To optimize the reaction conditions of the cross‐cou-
pling reaction of phenylboronic acid and bromobenzene,
PdNiZn/RGO ultrathin spherical NPs is used in different
solvents and temperatures (Table 1).
K CO was used as a base for optimizing the condi-
2
3
tions of the reaction. According to Table 1, the biphenyl
product is obtained in a high yield (97 %) when the reac-
tion is progressed in water at 80 °C (Table 1, entry 2).
The reactions were performed with various amounts of
catalyst to test the reaction feasibility with catalyst con-
centration. Due to the high cost of Pd, the optimum
amount of Pd in alloy catalyst was investigated for the
reaction of phenylboronic acid with bromobenzene at
optimized solvent and temperature condition (Table 2).
As shown in Table 2, the optimum amount of the Pd in
alloy catalyst was found to be 1.74 mol% of Pd in the case
of PdNiZn nanosheet, whereas interestingly for the
PdNiZn/RGO catalyst, 0.29 mol% of Pd was found to be
optimum. It is noteworthy that presence of RGO increases
the reaction yield and decreases the cost of catalyst.
More studies were focused on the application of the
optimized reaction conditions to Suzuki‐Miyaura cross
coupling reactions of aryl halides. As shown in Table 3,
various substrates including those with electron‐with-
drawing and electron‐donating groups can be coupled in
good reaction yields (70‐97 %) in short reaction times.
Also, the study of the efficacy of the present catalysts
FIGURE 3 (a) TEM images of the (a) PdNiZn nanosheet, (b)
PdNiZn/RGO ultrathin spherical NPs and (c) diagram of particles
size distribution for PdNiZn/RGO
movement of GO toward the interface (Scheme 2g). The
prepared spherical NPs from nucleation process do not
have time for self‐assembly and crystal growth. They

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FATAHI AND JAFAR HOSEINI
FIGURE 4 (a) EDAX elemental mapping analysis of (a) Pd, (b) Ni and (c) Zn nanosheet EDAX spectra of PdNiZn and (b) PdNiZn/rGO
nanocomposite
compared with previous reports in the coupling of
phenylboronic acid and bromobenzene in Table 4.
According to the following reasons, PdNiZn nano-
sheet and PdNiZn/RGO ultrathin spherical NPs are better
catalysts for Suzuki‐ Miyaura C‐C coupling reaction:
PdNiZn/RGO ultrathin spherical NPs, the Suzuki‐
Miyaura reaction was progressed in milder and green
condition. Also, PdNiZn/RGO ultrathin spherical
NPs exhibits a better catalytic activity than PdNiZn
due to its high surface‐to‐volume ratio which is due
to the small particle size and presence of RGO.
iii. Stabilization of the metal atoms on the RGO
support: GO with its large surface area can apply
as an effective stabilizer for fabrication of less aggre-
gated ultrathin spherical NPs. Furthermore, the syn-
ergistic catalytic interaction can be obtained between
graphene and metal NPs.
iv. Preparation strategy: The PdNiZn nanosheets and
PdNiZn/RGO spherical NPs are ultrathin films that
prepared at the toluene‐water interface. These struc-
tures contain a large number of surface atoms that
lead to a higher catalytic activity. This is the reasons
for their better catalytic activity. Also, PdNiZn/RGO
ultrathin spherical NPs exhibit better catalytic activ-
ity in Suzuki‐Miyaura reaction even than PdNiZn
due to the small particle size (3 nm), large surface‐
to‐volume ratio and presence of RGO with its large
specific surface area.
i. Synergistic effects: The as‐prepared trimetallic
ultrathin nanoalloy thin films exhibit superior cata-
lytic performance than their monometallic analo-
gous. This behavior is due to the interesting
synergistic interactions between the metals. The
excellent synergic interactions between Ni, Pd, and
Zn in trimetallic PdNiZn nanocatalysts are consid-
ered to play an important role in the observed high
catalytic activity. Scheme 4 exhibits the synergic
effect between the three metals (Pd, Ni, Zn) and for-
mation of PdNiZn trimetallic alloy with higher cata-
lytic activity, stability and new properties.
ii. The number of active sites and specific surface
area of the catalyst: The morphology, shape and
size of nanostructures play an important role in the
field of catalysis. Different atomic arrangements on
the surface are the result of nanostructures with dif-
ferent morphologies which leads to distinct geomet-
v. Accelerating the oxidative‐addition and reduc-
tive‐elimination steps by using trimetallic cata-
lysts: In general, three steps are present in the
catalytic cycle of each Suzuki‐Miyaura C‐C coupling
reaction: (1) oxidative addition, (2) transmetallation
[
45]
ric structures and improve the catalytic activity.
Nanosheets exhibit higher catalytic activity due to
their large specific surface area and more active sites
(Table 4). In the presence of PdNiZn nanosheets and

FATAHI AND JAFAR HOSEINI
7 of 11
SCHEME 3 PdNiZn nanosheet and PdNiZn/RGO spherical NPs
thin films catalyzed Suzuki‐Miyaura cross‐coupling reaction of aryl
halide with phenylboronic acid in water
TABLE 1 Suzuki‐Miyaura cross‐coupling reaction in various sol-
vents and temperatures in the presence of PdNiZn/RGO ultrathin
a
spherical NPs
b
Entry
Solvent
Temp (°C)
Yields (%)
1
H
H
H
H
2
2
2
2
O
r.t.
80
2
3
4
5
6
7
O
80
97
65
75
60
70
25
O/EtOH (1:1)
O/EtOH (1:1)
r.t.
80
EtOH
r.t
EtOH
70
Toluene
100
a
Reaction conditions: 1.0 mmol of bromobenzene, 1.50 mmol of
phenylboronic acid, 2.0 mmol of K CO , 5.0 ml of solvent, reaction time
2
3
0.25 h;
b
Isolated yield.
TABLE 2 Investigating the effect of catalyst amount in the syn-
thesis of biphenyl from phenylboronic acid and bromobenzene at
80 °C in water
a
a
PdNiZn/mol% ;
Entry yields (%)
PdNi/Zn/RGO/mol% ;
yields (%)
b,c
b,c
1
2
3
0.58; 80
1.74; 90
5.22; 90
0.10; 90
0.29; 97
0.87; 97
a
mol% of Pd;
b
Isolated yields;
c
Reaction time 0.25 h.
occurs in the order I > Br >> Cl, which is due to
the carbon‐halogen bond strength. Another impor-
tant fact is that electron‐withdrawing groups on the
aryl halide structure enhance the reactivity com-
pared to electron‐donating groups. This observation
is due to this fact that the oxidative addition step is
often the rate‐determining step (RDS) in the catalytic
cycle. Consider to this fact that Pd(0) acts as a nucle-
ophile and preferentially attacks the most electron‐
deficient position in the oxidative addition step; So,
the presence of high electron density groups on Pd
nanocatalysts increase the rate of oxidative addition.
Therefore, the presence of Ni and Zn with Pd(0) can
FIGURE 5 XPS spectra of (a) Pd 3d, (b) Ni 2p and (c) Zn 2p
[19]
and (3) reductive elimination (Scheme 5).
From
Table 3, it is obvious that the oxidative addition of
the Pd‐based catalysts into a carbon‐halogen bond

8
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FATAHI AND JAFAR HOSEINI
TABLE 3 Suzuki‐Miyaura C‐C cross‐coupling reactions of aryl halides with phenylboronic acid in the presence of PdNiZn nanosheet and
PdNiZn/RGO ultrathin spherical NPs
a
TOF (h‐1)
Entry
Substrate
Product
Catalyst
Time (min)
Yields (%)
TON
1
C
6
H
5
I
[1a]
PdNiZn
PdNi/Zn/RGO
10
5
90
98
51.72
337.92
323.25
4071.32
2
3
4
5
6
C
6
H
5
Br
[1a]
[1b]
[1a]
[1d]
[1c]
PdNiZn
PdNi/Zn/RGO
15
10
90
97
51.72
334.47
206.88
2090.43
4‐MeC
6
H
4
Br
PdNiZn
PdNi/Zn/RGO
100
80
80
80
45.97
275.85
27.69
207.41
C
6
H
5
Cl
PdNiZn
PdNi/Zn/RGO
70
55
73
78
41.95
268.95
36.16
295.54
4‐NO
2
C
6
H
4
Cl
PdNiZn
PdNi/Zn/RGO
60
45
70
75
40.22
258.61
40.22
344.81
C
5
H
4
NCl
PdNiZn
PdNi/Zn/RGO
280
145
80
82
45.97
282.75
9.86
117.32
a
Isolated yields;
b
See section 3.5 for the calculation of TONs and TOFs.
TABLE 4 Catalytic performance of different Pd‐based catalysts in the coupling of phenylboronic acid and bromobenzene
Entry
Catalyst
Solvent
Base
Temp (°C)
Time (h)
Yield (%)
Ref.
[
37]
1
PdNi NPs
(H
(H
2
2
O/EtOH 1:1)
O/EtOH 1:3)
K
K
K
2
2
3
CO
CO
3
3
50
7
65
a
[38]
[38]
[38]
[38]
2
3
4
5
6
7
8
9
Pd/SBA‐15
85
10
88
86
42
93
87
87
93.8
95
95
90
95
94
94
96
58
75
90
97
b
Pd/SiO
2
/TEG
toluene
PO
4
110
reflux
60
12
c
d
Pd‐G‐3
EtOH
NaOAc
24
e
f
Pd NPs
PdCu
Ionic liquid
NBu
4
OH
1.5
1.33
0.5
10
[
[
[
[
[
[
[
[
[
19]
19]
39]
40]
41]
42]
42]
19]
18]
H
H
2
2
O
O
K
2
2
CO
CO
3
3
80
PdCu/RGO
Pd Ni
Pd/Fe
Pd‐Ni/Fe
Pd thin film
K
80
1
2
DMF
NaOH
140
60
3
O
4
NPs
MeOH
EtOH
K
3
K
2
K
2
K
2
K
2
K
2
K
2
K
2
K
3
K
2
K
2
PO
4
18
10
11
12
13
14
15
16
17
18
19
3
O
4
CO
CO
CO
CO
CO
CO
CO
3
3
3
3
3
3
3
80
0.5
1.5
0.5
0.42
1
H
H
H
2
2
2
O
O
O
80
Pd/RGO thin film
PtPdCu
80
80
PdZn
(H
2
O/EtOH 1:1)
80
g
[18]
[43]
[44]
PdPtZn
H2O‐CTAB
80
0.75
1
h
Diimine/Pd(II)
DMA
80
i
NHC‐Pd
EtOH
PO
CO
CO
4
reflux
80
0.5
0.25
0.16
PdNiZn
H
H
2
2
O
O
3
3
This work
This work
PdNiZn/RGO
80
a
SBA‐15: Santa Barbara amorphous type silica;
b
TEG: tetra(ethylene glycol);
c
generation‐3 palladium NP‐cored dendrimer;
d
NaOAc: sodium acetate;
e
f
tetraalkylammonium‐based ionic liquids;
tetrabutylammonium hydroxide;
g
:
CTAB: cetyltrimethylammonium bromide;
h
DMA: dimethyl acetamide.

FATAHI AND JAFAR HOSEINI
9 of 11
SCHEME 4 Schematic illustration of
synergistic effect between three metals
(
Pd, Ni, and Zn)
SCHEME 5 Important steps in the
catalytic cycle of the Suzuki‐Miyaura C‐C
coupling reaction
Miyaura reaction) is facilitated by using elements of the
first‐row of transition metals such as Ni and Zn. So, the
addition of non‐precious Ni and Zn elements to the Pd
film can accelerate the reductive elimination reaction
in the last step of the reaction, additionally, reduces
the expensive Pd dosage in the catalyst.
3
.4 | Calculating the turnover number
(TON) and turnover frequency (TOF)
The turnover number (TON = mole of product per mole
of catalyst) and turnover frequency (TOF = TON per time
(
h)) were calculated for the as‐prepared catalysts applied
in Suzuki‐Miyaura reaction. By comparing the TOF value
of different catalysts, the efficiency of a catalyst can be
measured. Fox et al., reported that the Suzuki‐Miyaura
C‐C coupling reaction over Pd‐NP‐cored G‐3 dendrimer
FIGURE 6 Isolated yields for recycling of PdNiZn nanosheet and
PdNiZn/RGO ultrathin spherical NPs as catalyst in the coupling
reaction of phenylboronic acid with bromobenzene at 80 °C in water
‐
1 [46]
catalyst gives TOF = 1942 h .
In this study, not only
lead to increase the catalytic activity due to the donation
of electron to Pd centre. Furthermore, it is reported that
the reductive elimination step (the final step in Suzuki‐
the cost of catalyst is decreased by using non‐precious
metals alloying with Pd, but also ultrathin spherical NPs
is synthesized with high active sites and better catalytic

10 of 11
FATAHI AND JAFAR HOSEINI
activity. PdNiZn/RGO catalyst exhibits higher TOF
the synthesis of high‐performance catalysts for Suzuki‐
Miyaura C‐C cross‐coupling reaction.
‐
1
(2090.43 h ) for the Suzuki‐Miyaura reaction of
phenylboronic acid with bromobenzene.
ACKNOWLEDGEMENTS
3
.5 | Catalysts stability and reusability
We thank the Yasouj University Research Council and
the Iranian Nanotechnology Initiative Council for their
support.
The stability and reusability of the catalysts were examined
in the reaction of phenylboronic acid with bromobenzene
at 80 °C. In this step, the catalysts were separated by centri-
fugation and purified by washing with distilled water and
diethyl ether. The catalysts were recycled at least seven
times without any considerable loss of activity (Figure 6).
The Pd loading of the catalysts was also obtained using
ICP that confirms no leaching happens.
ORCID
S. Jafar Hoseini http://orcid.org/0000-0003-2703-5441
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Formation of PdNiZn thin film at oil‐water
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