Synthesis, characterization and catalytic performance of Pd(II) complex immobilized on Fe3O4@SiO2 nanoparticles for the ligand-free cyanation of aryl halides using K4Fe(CN)6

Article abstract of DOI:10.1002/aoc.4730

This work shows the preparation of a novel magnetic catalyst via immobilization of Pd(II)-N-benzyl-N-(4-bromophenyl)-5-amino-1H-tetrazole complex on the Fe₃O₄@SiO₂ nanoparticles (NPs). The application of Fe₃O₄@SiO₂ NPs supported Pd(II)-N-benzyl-N-(4-bromophenyl)-5-amino-1H-tetrazole complex [Fe₃O₄@SiO₂-BAT-Pd(II)] nanocatalyst is described for the cyanation of aryl iodides and bromides to the corresponding aryl nitriles using potassium hexacyanoferrate(II) [K₄Fe(CN)₆] as a non-toxic and economic cyanating agent under ligand- and additive-free conditions. Some aryl nitriles were efficiently synthesized from the corresponding aryl bromides and iodides in the presence of Fe₃O₄@SiO₂-BAT-Pd(II) nanocomplex. The core-shell nanocomplex demonstrated the superior catalytic performance for the synthesis of synthetically valuable aryl nitriles within good to excellent yields. This process eliminates the need to handle highly toxic metal cyanides, and it can be easily recovered and reused for six consecutive runs with no decreasing of its catalytic capability. Highlights: Preparation of Pd(II) complex immobilized on Fe₃O₄@SiO₂ nanoparticles [Fe₃O₄@SiO₂-BAT-Pd(II) nanocomplex]. Characterization of Fe₃O₄@SiO₂-BAT-Pd(II) nanocomplex using XRD, FT-IR, EDS, VSM, TEM and FESEM analyses. Catalytic cyanation of the various aryl halides with K₄Fe(CN)₆ under ligand-free conditions. The nanocomplex can be recovered and isolated six times with no significant loss of its catalytic ability.

Full text of DOI:10.1002/aoc.4730

Received: 11 September 2018
DOI: 10.1002/aoc.4730
Revised: 28 October 2018
Accepted: 1 November 2018
F U L L P A P E R
Synthesis, characterization and catalytic performance of
Pd(II) complex immobilized on Fe3O4@SiO2 nanoparticles
for the ligand‐free cyanation of aryl halides using K4Fe(CN)6
Mahmoud Nasrollahzadeh1
Ebrahim Mehdipour2
| Mahboobe Maryami2 | Mohaddeseh Sajjadi1 |
1 Department of Chemistry, Faculty of
Science, University of Qom, Qom 37185‐
359, Iran
2 Department of Chemistry, Faculty of
Science, Lorestan University,
This work shows the preparation of a novel magnetic catalyst via immobiliza-
tion of Pd(II)‐N‐benzyl‐N‐(4‐bromophenyl)‐5‐amino‐1H‐tetrazole complex on
the Fe3O4@SiO2 nanoparticles (NPs). The application of Fe3O4@SiO2 NPs sup-
ported Pd(II)‐N‐benzyl‐N‐(4‐bromophenyl)‐5‐amino‐1H‐tetrazole complex
[Fe3O4@SiO2‐BAT‐Pd(II)] nanocatalyst is described for the cyanation of aryl
iodides and bromides to the corresponding aryl nitriles using potassium
hexacyanoferrate(II) [K4Fe(CN)6] as a non‐toxic and economic cyanating agent
under ligand‐ and additive‐free conditions. Some aryl nitriles were efficiently
synthesized from the corresponding aryl bromides and iodides in the presence
of Fe3O4@SiO2‐BAT‐Pd(II) nanocomplex. The core‐shell nanocomplex demon-
strated the superior catalytic performance for the synthesis of synthetically
valuable aryl nitriles within good to excellent yields. This process eliminates
the need to handle highly toxic metal cyanides, and it can be easily recovered
and reused for six consecutive runs with no decreasing of its catalytic
capability.
Khorramabad 68137‐17133, Iran
Correspondence
Mahmoud Nasrollahzadeh, Department of
Chemistry, Faculty of Science, University
of Qom, Qom 37185‐359, Iran.
Email: mahmoudnasr81@gmail.com
Highlights
• Preparation of Pd(II) complex immobilized on Fe3O4@SiO2 nanoparticles
[Fe3O4@SiO2‐BAT‐Pd(II) nanocomplex].
• Characterization of Fe3O4@SiO2‐BAT‐Pd(II) nanocomplex using XRD, FT‐
IR, EDS, VSM, TEM and FESEM analyses.
• Catalytic cyanation of the various aryl halides with K4Fe(CN)6 under ligand‐
free conditions.
• The nanocomplex can be recovered and isolated six times with no significant
loss of its catalytic ability.
KEYWORDS
aryl nitriles, cyanation, Fe3O4@SiO2‐BAT‐Pd(II), K4Fe(CN)6, palladium nanocomplex
Appl Organometal Chem. 2019;e4730.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
1 of 12
https://doi.org/10.1002/aoc.4730

2 of 12
NASROLLAHZADEH ET AL.
Thus far, due to the easy recovery, low toxicity,
greater available catalytic surface and high catalytic activ-
ity, heterogeneous systems have been more and more
developed to fabrication of nanostructures.[26–31] Among
nanostructures, magnetic core‐shell complexes are prom-
ising candidates because of their different applications in
optical, medicinal, environmental, biological, material
and chemical areas.[32–38] Further, core‐shell magnetic
nanoparticles (MNPs) can merge the properties of mag-
netic core and various functional shells to show many
superior characteristics, such as chemical stability, good
biocompatibility, low toxicity, large pore volumes, mag-
netic susceptibility, high surface areas, rigidity and con-
trollable surface functionalization.[36,39–41]
Recently, the use of core‐shell nanocomplexes as
effective heterogeneous nanocatalysts has been rapidly
increased in a widespread variety of organic transforma-
tions.[42] Most recently, our laboratory designed the syn-
thesis of nanocomplexes using core‐shell MNPs
supported ionic liquids or copper and palladium com-
plexes with various tetrazoles as nitrogen‐rich heterocy-
cles.[43–45] Thus, the synthesis and surface modification
of MNPs has attracted an ever growing attention due to
all these mentioned advantages in organocatalysis
applications to propose new windows in an active
research area.
Through this study, for the first time, we have
designed an effective, heterogeneous and novel magnetic
nanocomplex using N‐benzyl‐N‐(4‐bromophenyl)‐5‐
amino‐1H‐tetrazole as a new ligand for the synthesis of
aryl nitriles through cyanation of aryl iodides or bromides
using K4Fe(CN)6 under ligand‐free conditions (Scheme 1).
The Fe3O4@SiO2‐BAT‐Pd(II) catalyst is synthesized via
immobilization of Pd(II)‐N‐benzyl‐N‐(4‐bromophenyl)‐5‐
amino‐1H‐tetrazole complex on the surface of
Fe3O4@SiO2 nanostructure. It is noteworthy that there
is no report on the synthesis of magnetic nanocomplex‐
based aminotetrazoles. Therefore, this report can create
1 | INTRODUCTION
Nitriles are a valuable molecular scaffold of organic mate-
rials. These compounds are versatile intermediates for the
synthesis of organic moieties, such as esters, amines,
amides, carboxylic acids, ketones and especially
tetrazole‐containing compounds as key synthetic precur-
sors of various natural products, agricultural chemicals,
pharmaceuticals, herbicides and dyes.[1–4] Besides, nitriles
are not only important as biologically active substances in
the synthesis of several drugs, but also are the industrial
key solvent to carry out plentiful organic reactions.[4]
The synthesis of aryl nitriles attracted the attention of
many researchers, because of their useful properties and
potential applications. A number of groups have developed
synthetic procedures in the literature for the preparation of
the substituted aryl nitriles. Aryl nitriles can be conven-
tionally synthesized via the reaction of aryl halides
(Rosenmund–von Braun reaction) and aryl diazonium
salts (Sandmeyer reaction) with a stoichiometric amount
of CuCN, and also transition metal‐catalyzed cyanation
of aryl halides with toxic cyanide sources such as Me3SiCN,
Zn(CN)2 and alkali‐metal cyanides.[5–9] However, all of
them have serious disadvantages, such as high reaction
temperature (150–250°C), long reaction times, use of toxic,
sensitive and metal cyanide sources, low yields, difficulty
or little availability in preparing the starting reagents or
catalysts, formation of high amounts of heavy metal
wastes, and environmental pollutions that limit their
applications.[10–14] Thus, the development of improved
synthetic methods for the synthesis of these compounds
to eliminate or reduce such limitations is much required.
These limitations can be partially controlled with cer-
tain specific measures relevant to cyanide source. Later
on, significant improvement for the cyanation reaction of
aryl halides was obtained with introduction of a safe, inex-
pensive and non‐flammable K4Fe(CN)6 reagent as cyanide
source.[15–20] This reagent is non‐toxic compared with for-
mer cyanide sources as which all cyanide groups of the iron
center could be coupled with various aryl halides. For these
reasons, K4Fe(CN)6 has received much interest as a safe
cyanide source for the synthesis of aryl nitriles.[15,18–20]
Over the last years, various ligands (e.g.
ethylenediamine and N,N′‐dimethylethylenediamine)
and homogeneous catalytic systems have been
developed for the preparation of aryl nitriles using
K4Fe(CN)6,[13,21–25] although difficulties and challenges
in recovering and reusing the nanocatalysts limited their
widespread application in industry. Therefore, the devel-
opment of new, efficient and convenient techniques for
the preparation of aryl nitriles under heterogeneous cata-
lytic systems and ligand/additive‐free conditions is still
demanding in wide areas of research and industry.
a
new approach to the production of magnetic
nanocomplex‐based aminotetrazole. The results show
that the Fe3O4@SiO2‐BAT‐Pd(II) catalyst has excellent
catalytic activity in the cyanation of aryl halides. This
procedure has advantages, such as short reaction times,
high yields, simple methodology and work‐up process,
high catalytic activity, easy preparation, separation, sta-
bility and reusability of the catalyst.
SCHEME 1 Catalytic cyanation of aryl halides under ligand‐free
conditions

NASROLLAHZADEH ET AL.
3 of 12
SCHEME 2 Synthesis of N‐(4‐
bromophenyl) cyanamide (1), N‐benzyl‐N‐
(4‐bromophenyl) cyanamide (2) and N‐
benzyl‐N‐(4‐bromophenyl)‐5‐amino‐1H‐
tetrazole (3)
Thus, aryl nitriles were successfully prepared in the pres-
ence of the Fe3O4@SiO2‐BAT‐Pd(II) nanocomplex using
K4Fe(CN)6 as an available and inexpensive cyanide
source without using ligand or additive that lead to good
atom efficiency.
2 | RESULTS AND DISCUSSION
2.1 | Preparation and characterization of
the Fe3O4@SiO2‐BAT‐Pd(II) nanocomplex
In continuation of our previous studies on the synthesis
of arylcyanamides, N‐benzyl‐arylcyanamides and
arylaminotetrazoles, herein, we were interested in design-
ing a novel magnetic complex as which the N‐benzyl‐
arylaminotetrazole was immobilized on the Fe3O4@SiO2
NPs surface. In the present study, the N‐(4‐bromophenyl)
cyanamide (1), N‐benzyl‐N‐(4‐bromophenyl) cyanamide
(2) were prepared from the 4‐bromoaniline according to
Scheme 2. As shown in Scheme 2, for the first time we
reported the synthesis of N‐benzyl‐N‐(4‐bromophenyl)‐5‐
amino‐1H‐tetrazole (3) using ZnCl2 in water under reflux
conditions. In view of the present findings, the catalytic
activity of Pd(II)‐N‐benzyl‐N‐(4‐bromophenyl)‐5‐amino‐
1H‐tetrazole complex immobilized on the Fe3O4@SiO2
NPs was evaluated to the synthesis of aryl nitriles through
the cyanation of aryl halides with K4Fe(CN)6 at 120°C.
The synthetic procedure of the Fe3O4@SiO2‐BAT‐
Pd(II) complex is schematically shown in Scheme 3. The
first step involves the fabrication of Fe3O4@SiO2 NPs (4)
using coating
a
non‐porous SiO2 shell around
superparamagnetic Fe3O4 NPs through self‐assembly,
condensation and hydrolysis of tetraethylorthosilicate
FIGURE 1 Fourier transform‐infrared (FT‐IR) spectrum of the
Fe3O4@SiO2‐BAT‐Pd(II) (7) nanocomplex
FIGURE 2 X‐ray diffraction analysis (XRD) pattern of the
Fe3O4@SiO2‐BAT‐Pd(II) (7) nanocomplex
SCHEME 3 Preparation of Fe3O4@SiO2‐BAT‐Pd(II) (7)

4 of 12
NASROLLAHZADEH ET AL.
(TEOS).[9] In the next step, further modification
Then, grafting of Fe3O4@SiO2@(CH2)3Cl (5) with N‐
benzyl‐N‐(4‐bromophenyl)‐5‐amino‐1H‐tetrazole (3) via
was
performed
using
grafting
with
of
the
3‐
chloropropyltriethoxysilane
Fe3O4@SiO2.
a
nucleophilic substitution process, and finally
Fe3O4@SiO2‐BAT‐Pd(II) (7) was prepared using
incorporation of Fe3O4@SiO2@(CH2)‐N‐benzyl‐N‐(4‐
bromophenyl)‐5‐amino‐1H‐tetrazole (6) with palladium
ions under reflux conditions. To date, this is the only
report wherein a magnetic complex‐based N‐benzyl‐N‐
arylaminotetrazole was used in catalysis.
The Fe3O4@SiO2‐BAT‐Pd(II) (7) catalyst then was
identified by using field emission scanning electron
microscopy (FESEM), X‐ray diffraction analysis (XRD),
Fourier transform‐infrared (FT‐IR), vibrating‐sample
magnetometer (VSM), transmission electron microscopy
(TEM) and energy‐dispersive X‐ray spectroscopy (EDS)
analyses.
The FT‐IR spectrum of as‐prepared complex is shown
in Figure 1. The peaks at about 3550–1600 cm−1 are
assigned to the O‐H and N‐H groups of the Fe3O4 MNPs.
Additionally, the peaks at 575 and 632 cm−1 are due to
FIGURE 3 Energy‐dispersive X‐ray spectroscopy (EDS) spectrum
of the Fe3O4@SiO2‐BAT‐Pd(II) (7) nanocomplex
FIGURE 4 Transmission electron microscopy (TEM) images of the Fe3O4@SiO2‐BAT‐Pd(II) (7) nanocomplex

NASROLLAHZADEH ET AL.
5 of 12
the Fe‐O stretching vibration in the Fe3O4 MNPs. The
fabrication of Fe3O4@SiO2 core‐shell was confirmed by
the peaks that appeared at 454, 800 and 1083 cm−1, which
are attributed to Si‐O‐Si bending, Si‐O bending, and Si‐O‐
Si stretching, respectively. Also, the peaks at 1353 and
1644 cm−1 correspond to the N¼N and C¼N stretching
bands of tetrazole ligand, indicating the grafting of ligand
on the surface of Fe3O4@SiO2‐CH2Cl.
the crystallographic structure of magnetite complex
(Figure 2). As shown in Figure 2, seven sharp diffraction
peaks located at 2θ = 12.60°, 28.20°, 36.00°, 43.20°,
51.80°, 57.20° and 63.1° were assigned to (110), (220),
(311), (400), (422), (511) and (440) crystal planes of the
cubic spinel structures of MNPs. The diffraction peaks
at 2θ = 40.2°, 47.0°, 68.1° and 82.2° can be indexed to
(111), (200), (220) and (311) Bragg's reflections of face‐
centered Pd. The particle's size can be found by applying
Sherrer's equation, where the average particle size is
found to be 27 nm.
For further convenience, the XRD pattern of
Fe3O4@SiO2‐BAT‐Pd(II) (7) was performed to identify
FIGURE 6 Magnetization curve for the Fe3O4@SiO2‐BAT‐Pd(II)
(7) nanocomplex
TABLE 1 Optimization of the reaction conditions for the
a
cyanation of phenyl iodide with K4Fe(CN)6
Fe3O4@SiO2‐BAT‐
Entry Pd(II) (7) (mg)
Solvent Base
Yieldb (%)
1
0.0
DMF
DMF
DMSO
Na2CO3
0.0
2
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.035
0.07
Na2CO3 89
Na2CO3 86
3
4
Toluene Na2CO3 16
5
H2O
Na2CO3 15
Na2CO3 28
6
NMP
DMF
DMF
DMF
DMF
DMF
DMF
7
K2CO3
Et3N
79
19
24
77
8
9
NaF
10
11
12
KOAc
Na2CO3 63
Na2CO3 89
aReaction conditions: phenyl iodide (1.0 mmol), K4Fe(CN)6 (0.17 mmol),
base (1.0 mmol), DMF (7.0 mL), 120°C, 5 hr.
bIsolated yield. DMF, dimethylformamide; NMP, N‐Methyl‐2‐pyrrolidone.
FIGURE
5
Field emission scanning electron microscopy
(FESEM) images of the Fe3O4@SiO2‐BAT‐Pd(II) (7) nanocomplex

6 of 12
NASROLLAHZADEH ET AL.
Besides, the EDS spectrum of Fe3O4@SiO2‐BAT‐
the successful synthesis of Fe3O4@SiO2‐benzylaminotet‐
Pd(II) magnetic complex.
Pd(II) (7) catalyst clearly shows the presence of corre-
sponding elements in its chemical structure (Figure 3).
In the EDS analysis of Fe3O4@SiO2‐BAT‐Pd(II) (7), iron
Fe, O, Si, N, Cl, C and Pd peaks were illustrated, indicat-
ing that the Pd(II)‐N‐benzyl‐N‐(4‐bromophenyl)‐5‐amino‐
1H‐tetrazole complex grafted on the Fe3O4@SiO2 NPs
surface (Figure 3). The aforementioned results proved
The surface morphology, size and structure of the
nanocomplex was investigated by TEM and FESEM
images (Figures 4 and 5, respectively). As revealed in
Figure 4, the TEM analysis of the complex confirmed that
Fe3O4@SiO2 MNPs with the spherical shape and the
nanometer size particles were prepared with low ten-
dency to agglomeration. The FESEM images of as‐
prepared nanocomplex are shown in Figure 5. It can also
be concluded that the surface of Fe3O4@SiO2 nanostruc-
ture is covered with Pd(II)‐N‐benzyl‐N‐(4‐bromophenyl)‐
5‐amino‐1H‐tetrazole complex (Figure 5). Based on the
aforesaid analyses, the structure of the novel fabricated
catalyst was entirely confirmed.
The hysteresis loop of Fe3O4@SiO2‐BAT‐Pd(II) (7)
nanocomplex was achieved in the applied magnetic field
at room temperature, with the field sweeping from −15
000 to +15 000 Oe using a SQUID magnetometer
(Figure 6). As shown in Figure 6, the saturation magneti-
zation (Ms) values of the Fe3O4 and Fe3O4@SiO2‐BAT‐
Pd(II) (7) nanocomplex were measured to be about 60.0
TABLE 2 Cyanation of aryl halides with K4Fe(CN)6 in the pres-
ence of Fe3O4@SiO2‐BAT‐Pd(II) (7) nanocomplexa
Time Yieldb
Entry ArX
Product
(hr)
(%)
1
5
89
2
3
4
5
6
7
7
5
5
6
90
90
95
93
91
7
8
5
5
91
93
9
5
5
92
94
10
11
12
5
7
94
89
13
14
15
16
7
7
7
7
91
90
91
92
aReaction conditions: Fe3O4@SiO2‐BAT‐Pd(II) (7) (0.05 g), aryl halide (1.0
mmol), K4Fe(CN)6 (0.17 mmol), Na2CO3 (1.0 mmol), DMF (7.0 mL), 120°C.
bIsolated yield.
SCHEME 4 The cyanation of aryl halides under different
reaction conditions

NASROLLAHZADEH ET AL.
7 of 12
and 25.0 emu g−1
,
respectively. The Ms of the
0.05 g of Fe3O4@SiO2‐BAT‐Pd(II) (7) as an effective cata-
lyst in DMF (Table 1, entry 2). Larger amounts of catalyst
did not improve the reaction yield (Table 1, entry 12),
while smaller amounts of catalyst clearly decrease the
reaction yield (Table 1, entry 11).
nanocomplex is smaller than Fe3O4 NPs owing to surface
modification of the Fe3O4 core with SiO2 shell and tetra-
zole ligand. These results clearly verified the synthesis of
Fe3O4@SiO2‐BAT‐Pd(II) as a nanomagnetic complex.
Upon optimization of reaction conditions, a series of
aryl halides possessing electron‐withdrawing or
electron‐donating substituents were subsequently sub-
jected to ligand‐free cyanation reaction, and the results
were shown in Table 2. A widespread variety of aryl bro-
mides and aryl iodides were transformed into the corre-
sponding substituted aryl nitriles. It was observed that
aryl halides bearing electron‐donating substituents gave
corresponding aryl nitriles in similar excellent yields
compared with electron‐withdrawing substituents. Acti-
vated and non‐activated aryl halides were reacted under
2.2 | Preparation of aryl nitriles using
Fe3O4@SiO2‐BAT‐Pd(II) (7) nanocomplex
After characterization of novel magnetic catalyst, the cat-
alytic
activity
of
Fe3O4@SiO2‐BAT‐Pd(II)
(7)
nanocomplex was evaluated for the synthesis of aryl
nitriles via cyanation reaction of aryl iodides and bro-
mides with K4Fe(CN)6 as a suitable cyanide source. Ini-
tial studies were tested in order to examine the reaction
conditions for the cyanation of phenyl iodide with
K4Fe(CN)6 in the presence of the Fe3O4@SiO2‐BAT‐
Pd(II) (7) catalyst as a model process (Table 1). The opti-
mization of the effect of catalyst amount was assessed. As
shown in Table 1, the reaction cannot be carried out in
the absence of Fe3O4@SiO2‐BAT‐Pd(II) (7) catalyst (entry
1). However, addition of the nanocatalyst to the mixture
has quickly increased the synthesis of benzonitrile in
higher yields. The effect of base and solvent on the
cyanation of phenyl iodide was also investigated.
Dimethylformamide (DMF) as solvent and Na2CO3
(sodium carbonate) as base are clearly the best choices
to give an excellent yield of product (Table 1, entry 2).
The optimum amount of Fe3O4@SiO2‐BAT‐Pd (II) (7)
was obtained as 0.05 g (Table 1, entry 2). The best result
can be achieved with iodobenzene (1.0 mmol), K4Fe(CN)6
(0.17 mmol) and Na2CO3 (1.0 mmol) in the presence of
FIGURE 8 Energy‐dispersive X‐ray spectroscopy (EDS) spectrum
of reused Fe3O4@SiO2‐BAT‐Pd(II) catalyst after sixth recycle
FIGURE 7 Fourier transform‐infrared
(FT‐IR) spectrum of 4‐
methoxybenzonitrile
a
TABLE 3 Reusability and recoverability of Fe3O4@SiO2‐BAT‐Pd(II) nanocomplex for cyanation of phenyl iodide with K4Fe(CN)6
Recycle
First
Second
Third
Fourth
Fifth
Sixth
Yieldb(%)
89
89
88
87
86
85
aReaction conditions: Fe3O4@SiO2‐BAT‐Pd(II) (0.05 g), phenyl iodide (1.0 mmol), K4Fe(CN)6 (0.17 mmol), Na2CO3 (1.0 mmol), DMF (7.0 mL), at 120°C, 5hr.
bIsolated yield.

8 of 12
NASROLLAHZADEH ET AL.
ligand‐ and additive‐free conditions. In addition, apart
from aryl halides, we tested heteroaromatic iodides
(Table 2, entries 10 and 11). All products can be success-
fully obtained in high yields and characterized by FT‐IR
and NMR spectra.
nanocatalysts. For this goal, the catalytic capability of the
recycled Fe3O4@SiO2‐BAT‐Pd(II) was tested. As shown in
Table 3, the cyanation of phenyl iodide with K4Fe(CN)6
was monitored to investigate the reusability of
Scheme 4 shows some reported methods in the litera-
ture [equations (1–11)][17,20,46–54] for the cyanation of aryl
halides with K4Fe(CN)6, and also presents synthetic
methods (equation 12) under different reaction conditions
in order to further understand the efficiency and advan-
tages of our method. The following items can be inferred
from the literature about different procedures for the
cyanation of aryl halides with different cyanide sources:
• harsh reaction conditions and tedious work‐up;
• usage of toxic, expensive and explosive reagents;
• formation of by‐products and impurities within long
reaction times;
• usage of ligand (difficulties in availability and prepa-
ration of substrate);
• the use of homogeneous catalysts that cannot be easily
recycled and recovered; and
• column chromatography was required for the purifi-
cation of the aryl nitriles.
Among all the reported methods for the preparation
of aryl nitriles in the literature,[17,20,46–54] our method
(equation 12) was completely the best type of protocol
due to preparation of an effective, novel and magnetically
separable heterogeneous catalyst, avoidance of the toxic
ligands, wide substrate scope and generality, simpler
work‐up, higher yields, shorter reaction time and conve-
nient reaction system, which make it an attractive and
beneficial strategy for the cyanation of aryl halides.
Besides, in contrast with other nanocatalysts,
Fe3O4@SiO2‐BAT‐Pd(II) (7) can be easily recovered from
the reaction using an external magnet and reused several
times. None of the above‐mentioned disadvantages was
also observed.
All products were characterized by 1H‐NMR, 13C‐
NMR and FT‐IR spectra, and melting points. Addition-
ally, the physical data of the known aryl nitriles were
identical with those reported in the literature.[17,20,46–54]
In FT‐IR spectra, the appearance of one absorption peak
of a CN stretching band of the nitriles in the range of
2225–2360 cm−1 can clearly confirm the preparation of
the products (Figure 7).
3 | CATALYST REUSABILITY
FIGURE
9
Field emission scanning electron microscopy
One of the most industrial applications of heterogeneous
catalytic systems is reusability and recyclability of
(FESEM) images of recovered Fe3O4@SiO2‐BAT‐Pd(II) catalyst
after sixth recycle

NASROLLAHZADEH ET AL.
9 of 12
FIGURE 10 Transmission electron microscopy (TEM) images of reused Fe3O4@SiO2‐BAT‐Pd(II) catalyst after sixth recycle
Fe3O4@SiO2‐BAT‐Pd(II) catalyst under optimized condi-
tions. When the cyanation reaction was completed,
Fe3O4@SiO2‐BAT‐Pd(II) could be easily recovered and iso-
lated after every run by using magnetic decantation
followed by washing with water and ethanol, then could
be dried and finally reused for the consecutive run
(Table 3). The Pd(II) complex was recycled for six consecu-
tive runs with no decreasing of its catalytic capability. After
the sixth run, the structure stability and morphology of
recycled Fe3O4@SiO2‐benzylaminotet‐Pd(II) was charac-
terized by EDS, FESEM and TEM (Figures 8–10). How-
ever, some core‐shell NP aggregations were observed.
bromophenyl)‐5‐amino‐1H‐tetrazole complex. So far
there has been no report about N‐benzyl‐
arylaminotetrazole stabilized on the Fe3O4@SiO2 MNPs
surface. A beneficial series of analytical techniques was
utilized to characterize a novel magnetic catalyst. The
resulting Fe3O4@SiO2‐BAT‐Pd(II) nanocomplex was uti-
lized as an effective heterogeneous catalyst for the
cyanation of aryl iodides and bromides to the correspond-
ing aryl nitriles by using K4Fe(CN)6 as a cyanating agent
under additive/ligand‐free conditions. Compared with
conventional methods, the advantages of this novel proto-
col are simple procedure, the use of environmentally
benign and safe cyanide source, high yields of the prod-
ucts, high activity and recovery of the catalyst, and the
elimination of ligand. Furthermore, the nanocomplex
can be easily recovered and isolated from the reaction
mixture using a magnetic decantation for at least six
consecutive runs with no noticeable decreasing of its
catalytic capability.
4 | CONCLUSIONS
In the present work, we reported successful synthesis of
an effective and novel magnetic catalyst composed of a
Fe3O4 NPs core, SiO2 shell and a Pd(II)‐N‐benzyl‐N‐(4‐

10 of 12
NASROLLAHZADEH ET AL.
water and 85.0 mL of ethanol (98%) were mechanically
dispersed using sonication for 25 min. Then, 3.0 mL of
TEOS as coating agent was added to the reaction solution,
and finally the above mixture was refluxed to afford core‐
shell NPs.
5 | EXPERIMENTAL
5.1 | Instruments and reagents
All materials, reagents and solvents of commercial grade
were from Merck (Germany) and Sigma‐Aldrich (USA).
All materials are used in the current work without fur-
ther purification. Structural confirmation of the aryl
6.3 | Preparation of
Fe3O4@SiO2@(CH2)3Cl
1
nitriles was performed using FT‐IR, H‐NMR and 13C‐
NMR spectra. The purity determination of the substrates
and reaction monitoring were accomplished by thin‐layer
chromatography (TLC) on silica gel PolyGram
SILG/UV254 plates. The NMR spectra were recorded on
a Bruker (Avance DRX‐400 MHz) spectrometer. The
phase composition of nanocomplex was investigated by
XRD (Philips type PW 1373 goniometer). The X‐ray wave-
length is Cu Kα radiation = 0.15406 nm, and the scan-
ning speed was 2° per min in the 2θ range (10–80).
Elemental analysis of Fe3O4@SiO2‐BAT‐Pd(II) was mea-
sured using EDS performed in FESEM. The FT‐IR (KBr)
spectrum of the samples was measured using a Nicolet
370 FT/IR spectrometer (Thermo Nicolet, USA). The
morphology and particle dispersion of Pd nanocomplex
was investigated by TEM (Philips EM208) at an accelerat-
ing voltage of 90 kV and FESEM (Hitachi S‐4700). VSM
measurements were recorded using a SQUID magnetom-
eter at 298 K (Quantum Design MPMS XL).
In a 250‐mL flask, 3.0 g of Fe3O4@SiO2, 80.0 mL of dry
toluene
and
10.0 mmol
of
(3‐chloropropyl)
trimethoxysilane were stirred and refluxed under nitro-
gen for 12 hr. The as‐prepared Fe3O4@SiO2@(CH2)3Cl
was cooled at room temperature then separated using a
magnet, and washed several times with deionized water
and dry toluene. The resulting product was dried at
75°C for 7 hr in a vacuum.
6.4 | Preparation of Fe3O4@SiO2@(CH2)3‐
benzylaminotet
In the next step, further modification was performed
using
the
immobilization
of
N‐benzyl‐N‐(4‐
bromophenyl)‐5‐amino‐1H‐tetrazole on the as‐prepared
Fe3O4@SiO2@(CH2)3Cl via a nucleophilic substitution
reaction. N‐Benzyl‐N‐(4‐bromophenyl)‐5‐amino‐1H‐tetra-
zole (5.0 mmol) and K2CO3 (5.0 mmol) in DMF (55.0
mL) were added to the Fe3O4@SiO2@(CH2)3Cl (2.0 g),
and then the above‐mentioned mixture was mixed and
refluxed for 24 hr. Next, the resulting solid was collected
by external magnet, washed with DMF and distilled
water, and then dried.
6 | SYNTHESIS OF N‐(4‐
BROMOPHENYL)CYANAMIDE
N‐benzyl‐N‐(4‐bromophenyl) cyanamide was prepared
according to the literature.[55]
6.5 | Preparation of Fe3O4@SiO2‐BAT‐
Pd(II)
6.1 | Synthesis of N‐benzyl‐N‐(4‐
bromophenyl)‐5‐amino‐1H‐tetrazole
Finally, a solution of PdCl2 (0.4 g) was added to
Fe3O4@SiO2@(CH2)3‐benzylaminotet (1.0 g) in 50.0 mL
of ethanol, and the reaction mixture was stirred under
reflux conditions for 24 hr. Finally, with similar steps of
separating, washing and drying, the resulting
Fe3O4@SiO2‐BAT‐Pd(II) as a novel and magnetically het-
erogeneous catalyst was obtained.
A mixture of N‐benzyl‐N‐(4‐bromophenyl) cyanamide
(2.0 mmol), ZnBr2 (2.0 mmol), sodium azide (3.0 mmol)
in H2O (15 mL) was stirred under reflux conditions for
24 hr. After completion of the reaction (monitored by
TLC), the solid residue was filtered, washed with water
treated with 4.0 mL of HCl (3 M), and the resulting prod-
uct was recrystallized using aq. EtOH.
6.6 | General protocol for the synthesis of
aryl nitriles
6.2 | Preparation of Fe3O4@SiO2 core‐shell
NPs
Typically, a mixture of Fe3O4@SiO2‐BAT‐Pd(II) (0.05 g),
aryl halides (1.0 mmol), Na2CO3 (1.0 mmol) and
K4Fe(CN)6 (0.17 mmol) in DMF (7.0 mL) was stirred at
120°C for the appropriate time. After consumption of aryl
The silica‐coated Fe3O4 NPs were obtained via the
reported routes in the literature.[9,41] Firstly, 1.0 g of the
Fe3O4 NPs, 3.0 mL of NH3 (25%), 25.0 mL of deionized

NASROLLAHZADEH ET AL.
11 of 12
[15] Y. L. Ren, Z. F. Liu, S. A. Zhao, X. Z. Tian, J. J. Wang, W. P.
halides (as monitored by TLC), the reaction mixture was
cooled and the core‐shell nanocatalyst could be recovered
using an external magnetic separator. Then, H2O and
ethyl acetate (EtOAc) were added to the reaction mixture
while shaking vigorously. The organic layer was
extracted, dried over MgSO4, filtered and then evaporated
to give the products in excellent yields. The resulting
products were purified by using recrystallization. All the
physical and spectral data of the synthesized nitriles were
found to be identical in comparison with those reported
in the literature.[17,20,46–54]
Yin, S. B. He, Catal. Commun. 2009, 10, 768.
[16] M. Nasrollahzadeh, Tetrahedron Lett. 2016, 57, 337.
[17] D. Saha, L. Adak, M. Mukherjee, B. C. Ranu, Org. Biomol.
Chem. 2012, 10.
[18] M. Nasrollahzadeh, M. Atarod, S. M. Sajadi, J. Colloid Interface
Sci. 2017, 486, 153.
[19] A. Schareina, A. Zapf, M. Beller, J. Organomet. Chem. 2004,
689, 4576.
[20] M. Nasrollahzadeh, Tetrahedron Lett. 2016, 57, 337.
[21] A. Pongratz, Monatsh. Chem. 1927, 48, 585.
[22] Y. L. Ren, Z. F. Liu, S. Zhao, X. Z. Tian, J. J. Wang, W. P. Yin,
ACKNOWLEDGEMENTS
S. B. He, Catal. Commun. 2009, 10, 768.
[23] Y.‐Z. Zhu, C. Cai, Synth. Commun. 2008, 38, 2753.
The authors are grateful to the Iranian Nano Council and
the University of Qom for the support of this work.
[24] A. Littke, M. Soumeillant, R. F. I. I. I. Kaltenbach, R. J.
Cherney, C. M. Tarby, S. Kiau, Org. Lett. 2007, 9, 1711.
[25] N. S. Nandurkar, B. M. Bhanage, Tetrahedron 2008, 65, 3655.
ORCID
[26] F. Soofivand, F. Mohandes, M. Salavati‐Niasari, Mater. Res.
Bull. 2013, 48, 2084.
Mahmoud Nasrollahzadeh
4539-3544
Ebrahim Mehdipour
1181
https://orcid.org/0000-0002-
[27] S. Zinatloo‐Ajabshir, M. Salavati‐Niasari, J. Mol. Liq. 2016,
2016, 545.
https://orcid.org/0000-0001-7479-
[28] S. Zinatloo‐Ajabshir, M. Salavati‐Niasari, M. Hamadanian, RSC
Adv. 2015, 5(43), 33 792.
[29] M. Salavati‐Niasari, Inorg. Chem. Commun. 2005, 8(2), 174.
REFERENCES
[30] M. Salavati‐Niasari, F. Davar, M. Mazaheri, J. Alloy. Compd.
2009, 470, 502.
[1] C. P. Jasperse, D. P. Curran, T. L. Fevig, Chem. Rev. 1991, 91,
1247.
[31] M. Salavati‐Niasari, P. Salemi, F. Davar, J. Mol. Catal. A: Chem.
2005, 238, 215.
[2] A. Kleemann, J. Engel, B. Kutscher, D. Reichert, Pharmaceuti-
cal Substance:Synthesis, Patents, Applications, 4th edn, Georg
Thieme, Stuttgart, 2001.
[32] J. X. Zhang, W. Sun, L. Bergman, J. M. Rosenholm, M. Lindén,
G. Wu, H. Xu, H. Gu, Mater. Lett. 2012, 67, 379.
[3] D. J. Augeri, J. A. Robl, D. A. Betebenner, D. R. Magnin, K.
Ashish, J. G. Robertson, W. Aiying, L. M. Simpkins, T. Prakash,
H. Qi, J. Med. Chem. 2005, 48, 5025.
[33] B. Liu, W. X. Xie, D. P. Wang, W. H. Huang, M. J. Yu, A. H.
Yao, Mater. Lett. 2008, 62, 3014.
[34] S. H. Xuan, S. F. Lee, J. T. F. Lau, X. M. Zhu, Y. X. J. Wang, F.
[4] R. C. Larock, Comprehensive Organic Transformations, VCH,
New York, 1989, 819.
Wang, Appl. Mater. Interfaces 2012, 4, 2033.
[35] Y. H. Deng, D. W. Qi, C. H. Deng, X. M. Zhang, D. Y. Zhao,
[5] K. W. Rosenmund, E. Struck, Ber. Dtsch. Chem. Ges. 1919, 52,
J. Am. Chem. Soc. 2008, 130, 28.
1749.
[36] M. Sajjadi, M. Nasrollahzadeh, S. M. Sajadi, J. Colloid Interface
Sci. 2017, 497, 1.
[6] G. P. Ellis, T. M. Romney‐Alexander, Chem. Rev. 1987, 87, 779.
[7] T. Sandmeyer, Ber. Dtsch. Chem. Ges. 1884, 17, 2650.
[37] Y. H. Deng, Y. Cai, Z. K. Sun, J. Liu, C. Liu, J. Wei, W. Li, Y.
Wang, D. Y. Zhao, J. Am. Chem. Soc. 2010, 132, 8466.
[8] D. Habibi, S. Heydari, M. Nasrollahzadeh, J. Chem. Res. 2013,
573, 36.
[38] M. F. Shao, F. Y. Ning, J. W. Zhao, M. Wei, D. G. Evans, X.
Duan, J. Am. Chem. Soc. 2012, 134, 1071.
[9] W. Stober, A. Fink, E. Bohn, J. Colloid. Interf. Sci. 1968, 26, 62.
[39] M. J. Nasab, A. R. Kiasat, RSC Adv. 2016, 6(48), 41 871.
[10] H. J. Cristau, A. Ouali, J. F. Spindler, M. Taillefer, Chem. Eur. J.
2005, 11, 2483.
[40] A. H. Lu, E. L. Salabas, F. Schuth, Angew. Chem. Int. Ed. 2007,
46, 1222.
[11] B. Mariampillai, D. Alberico, V. Bidau, M. Lautens, J. Am.
Chem. Soc. 2006, 128, 14 436.
[41] M. Nasrollahzadeh, S. M. Sajjadi, H. A. Khonakdar, J. Mol.
Struct. 2018, 1161, 453.
[12] M. Hatsuda, M. Seki, Tetrahedron 2005, 61, 9908.
[42] M. Massi, S. Stagni, M. I. Ogden, Coord. Chem. Rev. 2018, 375,
[13] J. Zanon, A. Klapars, S. L. Buchwald, J. Am. Chem. Soc. 2003,
125, 2890.
164.
[43] M. Nasrollahzadeh, Z. Issaabadi, H. A. Khonakdar, U.
[14] H. H. Hodgson, Chem. Rev. 1947, 40, 251.
Wagenknecht, Sep. Purif. Technol. 2018, 203, 185.

12 of 12
NASROLLAHZADEH ET AL.
[44] M. Nasrollahzadeh, Z. Issaabadi, R. Safari, Sep. Purif. Technol.
2019, 209, 136.
[53] Q. Wen, J. Jin, L. Zhang, Y. Luo, P. Lu, Y. Wang, Tetrahedron
Lett. 2014, 55, 1271.
[45] M. Nasrollahzadeh, Z. Issaabadi, Sep. Purif. Technol. 2019, 211,
[54] L. Zhang, P. Lu, Y. Wang, Chem. Commun. 2015, 51, 2840.
809.
[55] M. Nasrollahzadeh, M. Sajjadi, S. M. Sajadi, Appl Organomet
Chem. 2019, 33(2), e4705.
[46] T. Schareina, A. Zapf, M. Beller, Chem. Commun. 2004, 12,
1388.
[47] S. M. Sajadi, M. Maham, Lett. Org. Chem. 2014, 11, 136.
[48] M. Maham, S. Bahari, J. Chem. Res. 2014, 38, 291.
How to cite this article: Nasrollahzadeh M,
Maryami M, Sajjadi M, Mehdipour E. Synthesis,
characterization and catalytic performance of
Pd(II) complex immobilized on Fe3O4@SiO2
nanoparticles for the ligand‐free cyanation of aryl
halides using K4Fe(CN)6. Appl Organometal Chem.
2019;e4730. https://doi.org/10.1002/aoc.4730
[49] S. A. Weissman, D. Zewge, C. Chen, J. Org. Chem. 2005, 70, 1508.
[50] D. Zhang, H. Sun, L. Zhang, Y. Zhou, C. Li, H. Jiang, K. Chen,
H. Liu, Chem. Commun. 2012, 48, 2909.
[51] J. Schulz, I. Císarˇová, P. Šteˇpnicˇka, Organometallics 2012, 31,
729.
[52] T. Chatterjee, R. Dey, B. C. Ranu, J. Org. Chem. 2014, 79, 5875.