Hiyama cross-coupling reaction using Pd(II) nanocatalyst immobilized on the surface of Fe3O4@SiO2

Article abstract of DOI:10.1002/aoc.3978

We report a simple process for the synthesis of Fe₃O₄@SiO₂/APTMS (APTMS?=?3-aminopropyltrimethoxysilane) core–shell nanocatalyst support. The new nanocatalyst was prepared by stabilization of Pd(cdha)₂ (cdha?=?bis(2-chloro-3,4-dihydroxyacetophenone)) on the surface of the Fe₃O₄@SiO₂/APTMS support. The structure and composition of this catalyst were characterized using various techniques. An efficient method was developed for the synthesis of a wide variety of biaryl compounds via fluoride-free Hiyama cross-coupling reactions of aryl halides with arylsiloxane, with Fe₃O₄@SiO₂/APTMS/Pd(cdha)₂ as the catalyst under reaction conditions. This methodology can be performed at 100°C through a simple one-pot operation using in situ generated palladium nanoparticles. High catalytic activity, quick separation of catalyst from products using an external magnetic field and use of water as green solvent are attributes of this protocol.

Full text of DOI:10.1002/aoc.3978

Received: 16 April 2017
DOI: 10.1002/aoc.3978
Revised: 29 May 2017
Accepted: 20 June 2017
F U L L P A P E R
Hiyama cross‐coupling reaction using Pd(II) nanocatalyst
immobilized on the surface of Fe3O4@SiO2
Kazem Karami1
| Nasrin Jamshidian1 | Mohammad Mehdi Nikazma1 | Pablo Hervés2 |
Amir Rezaei Shahreza3 | Ali Karami3
1 Department of Chemistry, Isfahan
We report a simple process for the synthesis of Fe3O4@SiO2/APTMS (APTMS = 3‐
University of Technology, Isfahan 84156/
83111, Iran
aminopropyltrimethoxysilane) core–shell nanocatalyst support. The new
nanocatalyst was prepared by stabilization of Pd(cdha)2 (cdha = bis(2‐chloro‐
3,4‐dihydroxyacetophenone)) on the surface of the Fe3O4@SiO2/APTMS support.
The structure and composition of this catalyst were characterized using various
techniques. An efficient method was developed for the synthesis of a wide variety
of biaryl compounds via fluoride‐free Hiyama cross‐coupling reactions of aryl
halides with arylsiloxane, with Fe3O4@SiO2/APTMS/Pd(cdha)2 as the catalyst
under reaction conditions. This methodology can be performed at 100°C through
a simple one‐pot operation using in situ generated palladium nanoparticles. High
catalytic activity, quick separation of catalyst from products using an external
magnetic field and use of water as green solvent are attributes of this protocol.
2 Department of Chemistry, University of
Vigo, 36310 Vigo, Spain
3 Faculty of Mechanical Engineering,
Dehaghan branch, Islamic Azad
University, Isfahan, Iran
Correspondence
Kazem Karami, Department of Chemistry,
Isfahan University of Technology, Isfahan
84156/83111, Iran.
Email: karami@cc.iut.ac.ir
Funding information
Iranian Nanotechnology Initiative Coun-
cil; Department of Chemistry, Isfahan
University of Technology
KEYWORDS
green solvent, heterogeneous catalyst, Hiyama cross‐coupling reaction, nanocatalyst
1 | INTRODUCTION
biaryls, a palladium–phosphinous acid‐catalysed and
NaOH‐promoted coupling of arylsiloxanes in water. How-
ever, due to the unreactivity of organosilanes, the reaction
must be performed in the presence of fluoride as a nucleo-
philic promoter to activate the stable Si―C bond to form a
pentavalent silicon centre which is labile enough to allow
for the breaking of the Si―C bond during the transmeta
llation step.[5–7] In the pentacoordinate complex, trans
metallation is facilitated by the enhanced polarization of
the Si―C bond. The fluoride ion is also a strong base, so
base‐sensitive protecting groups, acidic protons and func-
tional groups may be affected by the addition of this activa-
tor, and therefore the replacement of inorganic bases such
as KOH and NaOH[8] in an aqueous solvent has been sug-
gested.[9–11] Some of this solvent0s advantages are environ-
mental friendliness, non‐flammability and cheapness,
which are in agreement with basic principles of green chem-
istry. The organic product is simply separated from the aque-
ous phase, and one of the important traits of catalysts is their
The palladium‐catalysed C–C cross‐coupling reactions of
aryl halides and organometallic reagents have been devel-
oped to produce symmetric and asymmetric biaryl com-
pounds. Among organometallic compounds, organo
stannanes[1] (Stille reaction) and organoborons[2] (Suzuki
reaction) are broadly employed as useful transmetallating
reagents, due to their high functional group tolerances. But
organosilicon compounds with organic halides have become
the best alternative to the use of other reagents from an envi-
ronmental point of view, ease of preparation, stability, low
cost and accessibility.[3,4] Generally, organosilanols can cou-
ple via two mechanistically distinct processes. One is opera-
tive under basic conditions and requires only formation of
silanolates, while the second pathway involves the use of a
fluoride activator that can form an active fluorosiliconate.
Recent developments in silicon‐based cross‐coupling include
the application of triallyl(aryl)silanes for the synthesis of
Appl Organometal Chem. 2017;e3978.
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https://doi.org/10.1002/aoc.3978

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KARAMI ET AL.
reuse in the aqueous solvent.[12] In addition, anionic surfac-
tants, like sodium dodecylsulfate (SDS), have been used for
increasing the yields of reactions. SDS acts as a reductant
and it is a good stabilizer for the formation of palladium
nanoparticles.[13]
Because of the high surface‐to‐volume ratio of nano-
particles, they provide a large number of active sites per
unit area compared to their heterogeneous analogues.
Although most homogeneous catalysts exhibit excellent
high activity, the high expense, metal pollution and diffi-
culty of product purification cannot be ignored.[14]
In the last few decades, magnetic nanoparticles have
been employed as an effective replacement for heteroge-
neous catalyst supports because they have many advan-
tages such as ease of availability, chemical stability and
simple preparation.[15–20] Most importantly, Fe3O4‐sup-
ported metal catalysts can be separated from a reaction
system using an external permanent magnet.
In the work reported here, Fe3O4@SiO2/APTMS/
Pd(cdha)2 (APTMS = 3‐aminopropyltrimethoxysilane;
cdha = bis(2‐chloro‐3,4‐dihydroxyacetophenone)) catalyst
nanoparticles were prepared and applied in the fluoride‐
SCHEME 1 Preparation of Fe3O4@SiO2/APTMS/Pd(cdha2)

KARAMI ET AL.
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free Hiyama cross‐coupling reaction of phenyltrimetho
xysilane with aryl halides in water.
product was filtered and washed several times with
acetone and ethanol and dried at 60°C under vacuum
for 12 h.
2 | EXPERIMENTAL
2.1 | General
All reactants were purchased from Aldrich and Merck.
Solvents were used without any modification or change.
Fe3O4@SiO2/APTMS/Pd(cdha)2 catalyst was pre-
pared and characterized using Fourier transform infra-
red (FT‐IR) spectra (in KBr tablets with a JASCO FT/
IR 680), scanning electron microscopy (SEM; Philips
model XL‐30) and transmission electron microscopy
(TEM; Philips model CM30). Powder X‐ray diffraction
(XRD) patterns were measured using a Scintag X‐ray
diffractometer with a 1.54 Å (Cu Kα) X‐ray radiation
source and atomic absorption spectra were obtained
with a PerkinElmer 2380 spectrophotometer. Palladium
content of the catalyst was measured with an induc-
tively coupled plasma (ICP) analyser (Varian‐vista‐pro‐
CCD simultaneous ICP‐OES inductive genoppeltes
plasma).
The Fe3O4 nanoparticles were synthesized using the
co‐precipitation method,[21] with 20 mmol of FeCl2·
4H2O and 20 mmol of FeCl3·6H2O in 50 ml of 0.5 M
HCl solution. Then, the suspension was added dropwise
into 500 ml of a 1.5 M NaOH solution at 80°C with vig-
orous stirring under nitrogen atmosphere. Finally the
black precipitate was washed with deionized water sev-
eral times and dried at 60°C for 12 h to afford Fe3O4
nanoparticles.
SCHEME 2 FT‐IR spectra of catalyst and support
2.2 | Preparation of silica‐coated Fe3O4
nanoparticles (Fe3O4@SiO2)
Fe3O4 nanoparticles (2 g) were dispersed in 400 ml of
deionized water and heated to 80°C under nitrogen atmo-
sphere. Then, the suspension was added dropwise into
40 ml of a 1.0 M sodium silicate solution with vigorous
stirring and the mixture pH was adjusted to 6.0 in 2 h with
2 M HCl. The reaction was then further stirred for 3 h.
The Fe3O4@SiO2 precipitate was completely washed with
deionized water and collected using a permanent magnet,
and finally dried at 60°C for 6 h.
FIGURE
Fe3O4@SiO2/APTMS/Pd(cdha)2
1
Powder XRD patterns of (a) Fe3O4 and (b)
2.3 | Preparation of modified silica‐coated
Fe3O4 nanoparticles (Fe3O4@SiO2–NH2)
Fe3O4@SiO2 (2 g) and toluene (50 ml) were placed to a
250 ml flask and dispersed with sonication, after which
4 ml of APTMS was added. The mixture was refluxed
at 100°C for 12 h under nitrogen atmosphere. The
FIGURE 2 SEM image of Fe3O4@SiO2/APTMS/Pd(cdha)2

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KARAMI ET AL.
2.4 | Preparation of Fe3O4@SiO2/APTMS/
Pd(cdha)2
2.6 | Recycling procedure for palladium
magnetic nanoparticles
The recyclability of Fe3O4@SiO2/APTMS/Pd(cdha)2 was
tested in the Hiyama cross‐coupling reaction of
iodobenzene with phenyltrimethoxysilane. After the first
run, the nanocatalyst was separated using an external
magnet. Then it was washed with acetone several times
to remove adsorbed organic compounds and salt. The cat-
alyst was dried at 60°C for 12 h and it was used for a sec-
ond time without further activation and the same process
was repeated.
For adding to amino‐functionalized substrate, a mixture
of Fe3O4@SiO2–NH2 nanoparticles (2 g), cdha (1 g) and
ethanol (50 ml) was placed to a 100 ml flask. The mixture
was refluxed at 60°C for 24 h and, after washing with hot
ethanol and toluene, was dried at 110°C for 12 h. Finally,
2 g of the product with 0.5 g of palladium chloride and
50 ml of anhydrous acetone was transferred to a flask
and stirred at room temperature for 24 h. The mixture
was washed with anhydrous acetone and then was dried
at 60°C for 6 h. The immobilization of palladium on the
magnetic nanoparticles is shown in Scheme 1.
After preparation of Fe3O4@SiO2/APTMS/Pd(cdha)2,
the amount of palladium in a 5 ppm solution of the
catalyst was determined using atomic absorption spec-
trophotometry and ICP analysis. According to calcula-
tions, the amount of palladium in the catalyst was
0.224 mol%.
3 | RESULTS AND DISCUSSION
3.1 | Characterization of Fe3O4@SiO2/
APTMS/Pd(cdha)2
Scheme 1 shows the synthetic procedure in which Fe3O4
(magnetite) nanoparticles were used as magnetic cores.
For this, the washed Fe3O4 nanoparticles were added to
a solution of sodium silicate by adjusting the pH. To allow
binding of Pd(cdha)2 on the surface of the Fe3O4@SiO2
nanoparticles, an amine‐terminated surface silanizing
agent (APTMS) was used to functionalize the SiO2 sur-
face. The obtained Fe3O4 nanoparticles were capped by
APTMS with hydrophilic surfaces, as shown in Scheme 1.
The washed Fe3O4@SiO2–NH2 nanoparticles including
amino‐functionalized substrate were added to a solution
of cdha in ethanol. Finally, the product was added to a
suspension of palladium chloride in anhydrous acetone
2.5 | General procedure for Fe3O4@SiO2/
APTMS/Pd(cdha)2‐catalysed Hiyama cross‐
coupling reaction
A mixture of aryl halide (0.50 mmol), phenyltrimetho
xysilane (0.75 mmol), SDS (0.1 mmol), NaOH (0.3 mmol)
and Fe3O4@SiO2/APTMS/Pd(cdha)2 catalyst (0.224 mol%
Pd) in water (4.0 ml) was stirred for 5 min at 100°C (oil
bath temperature). The product was extracted with ethyl
acetate (5 ml).
FIGURE 3 TEM images of (a) Fe3O4@SiO2/APTMS and (b) Fe3O4@SiO2/APTMS/Pd(cdha)2

KARAMI ET AL.
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and refluxed for 24 h, resulting in the formation of
Fe3O4@SiO2/APTMS/Pd(cdha)2 nanoparticles.
The changes of functional groups on Fe3O4@SiO2
were investigated using the FT‐IR spectroscopic tech-
nique. In the spectrum of Fe3O4@SiO2 shown in
Scheme 2, the peaks at 3200 and 575 cm−1 correspond to
the O―H and Fe―O vibrations of Fe3O4, respectively.
In the FT‐IR spectra of Fe3O4@SiO2 and Fe3O4@SiO2/
APTMS, the absorption intensity of Fe―O group is
decreased by silica addition. The strong absorption bands
at 1095, 804 and 581 cm−1 can be ascribed to the
stretching and deformation vibrations of SiO2 (Scheme 2,
curve II). The observed peaks at 1499 and 691 cm−1 are
ascribed to stretching and bending vibrations of amino
group, respectively. For Fe3O4@SiO2/APTMS (Scheme 2,
curve III), the aliphatic group is confirmed by C―H
stretching band at 2939 cm−1 and C―H scissoring band
at 1393 cm−1. The FT‐IR spectrum of Fe3O4@SiO2/
APTMS/(cdha)2 shows characteristic bands at 1623 cm−1
belonging to C―N group (Scheme 2, curve IV). After
addition of PdCl2 to the ligand, the characteristic band
of C―N appears at 1638 cm−1 (Scheme 2, curve V).
Figure 1 shows typical XRD patterns of Fe3O4 and
Fe3O4@SiO2/APTMS/Pd(cdha)2 nanocatalyst powders. It
is apparent from the XRD data cards that standard Fe3O4
crystal with spinel structure has six diffraction peaks. The
relatively strong diffraction peaks at 2θ = 30.3°, 35.5°,
43.2°, 53.7°, 57.3° and 62.7° could be assigned to the
(220), (311), (400), (422), (511) and (440) planes belonging
to Fe3O4 crystalline structure (Figure 1a).[22–24] All the dif-
fraction peaks were consistent with a face‐centred cubic
structure. In the case of Fe3O4@SiO2/APTMS/Pd(cdha)2,
in addition a weak and wide diffraction peak correspond-
ing to the (111) reflection of the Pd(II) crystal can be
observed (Figure 1b). Moreover, no crystalline microstruc-
ture was evident for the silica phase because of its amor-
phous structure.
FIGURE 4 Particle size distributions of (a) support and (b)
catalyst
1
3‐Methylbiphenyl. H NMR (300 MHz, CDCl3, δ,
ppm): 7.7 (m, 2H), 7.5 (m, 6H), 7.3 (m, 1H), 2.5 (s, 3H).[26]
1
1‐Phenylnaphthalene. H NMR (300 MHz, CDCl3,
δ, ppm): 7.90–7.8 (m, 3H), 7.51–7.36 (m, 9H). 13C NMR
(75 MHz, CDCl3, δ, ppm): 140.9, 140.4, 134.0, 131.8,
130.2, 128.4, 127.7, 127.3, 127.0, 126.1, 125.9, 125.5.[27]
4‐Nitrobiphenyl. 1H NMR (300 MHz, CDCl3, δ,
ppm): 8.29 (d, 2H), 7.73 (d, 2H), 7.62 (dd, 2H), 7.52–
7.41 (m, 3H). 13C NMR (75 MHz, CDCl3, δ, ppm):
147.7, 147.2, 138.9, 129.3, 129.0, 127.9, 127.5, 124.2.[27]
SEM images confirmed the uniform distribution of Pd
nanoparticles onto Fe3O4@SiO2/APTMS (Figure 2).
According to the TEM images (Figure 3). the Pd nanopar-
ticles were formed and dispersed through the support sur-
face. The average sizes of Fe3O4 in Fe3O4@SiO2/APTMS
and palladium in Fe3O4@SiO2/APTMS/Pd(cdha)2 nano-
particles are about 23.8 nm (Figure 4a) and 15.8 nm
(Figure 4b) respectively. The aggregation of the
nanocatalyst and substrate can be discerned clearly.
3.2 | Characterization of products of
Hiyama cross‐coupling reactions
Biphenyl. A white solid. 1H NMR (300 MHz, CDCl3,
δ, ppm): 7.35–7.37 (m, 2H, ArH), 7.4–7.5 (m, 4H, ArH),
7.6 (m, 4H, ArH).[25]
SCHEME 3 Hiyama cross‐coupling reaction cycle

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KARAMI ET AL.
TABLE 1 Optimizing reaction conditions for Hiyama cross‐coupling reactions of iodobenzene with phenyltrimethoxysilane
Entry
Catalyst (g)
Solvent
Activator (g)
Temp. (°C)
Time (min)
Conversion (%)a
1
0.02
Toluene
TBAB (0.04)
60
3600
<5
2
0.02
0.02
0.02
0.02
0.02
0.02
0.01
0.01
0.01
0.02
0.02
0.02
0.02
0.02
0.01
0.01
0.01
Toluene
Toluene
THF
TBAB (0.04)
90
3600
3600
3600
3600
3600
4200
4200
4200
4200
5
8
3
TBAB (0.04)
120
90
48
<5
—
—
22
18
29
32
20
—
—
52
73
65
83
100
4
TBAB (0.04)
5
Acetone
Water
TBAB (0.04)
60
6
TBAB (0.04)
60
7
Toluene
Toluene
Toluene
Toluene
Water
TBAB (0.02) + NaOH (0.04)
TBAB (0.01) + NaOH (0.05)
TBAB(0.01) + NaOH(0.01)
TBAB (0.015) + NaOH (0.025)
NaOAc (0.01)
85
8
85
9
85
10
11
12
13
14
15
16
17
18
85
100
100
100
100
100
100
100
100
Water
NaHCO3 (0.009)
5
Water
KOH (0.005)
5
Water
NaOH (0.005)
3
Water
NaOH (0.005)
5
Water
NaOH (0.005)
5
Water
NaOH (0.004) + SDS (0.001)
NaOH (0.004) + SDS (0.003)
5
Water
5
aReaction conditions: aryl halide (0.50 mmol), phenyltrimethoxysilane (0.75 mmol), NaOH (0.3 mmol), SDS (0.1 mmol), H2O (4 ml), catalyst (0.224 mol% Pd),
100°C, 5 min, in air. Reactions were monitored using GC.
Biphenyl‐2‐carboxaldehyde. A white solid. 1H
NMR (300 MHz, CDCl3, δ, ppm): 10.01 (d, 1H, CHO),
8.05 (dd, 1H, Ar), 7.7 (dt, 1H, Ar), 7.55–7.39 (m, 7H, Ar).[28]
(Table 1, entries 5 and 6). We used various amounts of
NaOH to increase the efficiency of the reaction, but finally
the reaction did not show a good efficiency in organic sol-
vents (Table 1, entries 7–10). Based on the obtained
results and to achieve conditions of green chemistry, the
reaction was optimized in water with various bases in
the absence of TBAB.
The reaction in the presence of KOH and NaHCO3 as
bases gave no yields (Table 1, entries 12 and 13), and use
of NaOAc led to only 20% yield (Table 1, entry 11), but the
use of NaOH gave 52% of initial materials converted to
product at 100°C for 3 min. The yield of product increased
to 73% during 5 min (Table 1, entries 14 and 15).
According to our studies, using SDS as an additive to
the reaction mixture, the yield could be increased to
100% in 5 min (Table 1, entries 17 and 18).
The Fe3O4@SiO2/APTMS/Pd(cdha)2‐catalysed Hiyama
cross‐coupling reactions of various aryl halides with
phenyltrimethoxysilane were investigated under the opti-
mized conditions. The results are summarized in Table 2.
The cross‐coupling reaction is tolerant of functional
groups in the case of aryl halides. The reactions with both
electron‐withdrawing and electron‐donating groups
3.3 | Optimized conditions for Hiyama
cross‐coupling reactions
Fe3O4@SiO2/APTMS/Pd(cdha)2 was used as a catalyst for
the Hiyama cross‐coupling reactions of aryl halides with
arylsiloxane. The critical step for the Hiyama cross‐cou-
pling reaction is polarization of the Si―C bond. The
silane must be activated with a fluoride ion or a base to
form a pentavalent silicon compound[13] that is necessary
in the first step (Scheme 3). We examined the ability of
Fe3O4@SiO2/APTMS/Pd(cdha)2 to catalyse the Hiyama
cross‐coupling reaction. First, the reaction was optimized
in various solvents and in the presence of tetra‐n‐
butylammonium bromide (TBAB) at different tempera-
tures. Solvents have considerable effects on C―C bond
formation. Toluene showed better results than other
solvents in the presence of TBAB (Table 1, entries 1–4),
but the reaction did not progress in water and acetone

KARAMI ET AL.
7 of 10
TABLE 2 Hiyama cross‐coupling reaction of various aryl halides
with phenyltrimethoxysilane
good yields (Table 2, entry 10). Finally, benzyl chloride
was reacted with phenyltrimethoxysilane and 72% yield
was obtained (Table 2, entry 11). However, the obtained
results showed that in the Hiyama cross‐coupling reac-
tion, aryl chlorides led to lower yields than aryl bromides
and aryl iodides.
Conversion
(%)a
TOF
Entry
R1
X
(h−1 b
)
1
H
I
100
98
78
100
84
63
96
98
68
82
72
5357
3.4 | Recycling of Fe3O4@SiO2/APTMS/
Pd(cdha)2
2
H
Br
Br
Br
Br
Br
Br
Br
Cl
Cl
Cl
5250
4179
5357
4500
3375
5143
5250
3643
4393
3857
3
3‐NO2 (meta)
3‐CH3 (meta)
2‐pyridine
2‐Thiophene
1‐naphthalene
4‐CHO (para)
H
The Hiyama cross‐coupling reaction was performed in the
presence of iodobenzene and phenyltrimethoxysilane.
The catalyst was then removed using a magnet and it
was washed with acetone. After drying, the cycle was
repeated four times, and in each cycle the catalyst showed
good activity due to good dispersion of it and the active
sites on the surface (Figure 5). The recycling process
shows that the prepared catalyst has a good stability.
The time course of the Hiyama cross‐coupling reac-
tion (Figure 6) was studied by sampling of the reaction
at various time intervals and analysing using GC. It was
4
5
6
7
8
9
10
11
4‐NO2 (para)
Benzyl
aReaction conditions: aryl halide (0.50 mmol), phenyltrimethoxysilane
(0.75 mmol), NaOH (0.3 mmol), SDS (0.1 mmol), H2O (4 ml), catalyst
(0.224 mol% Pd), 100°C, 5 min, in air. Reactions were monitored using GC.
bTOF = (moles of products/moles of catalyst)/time.
substituents led to the corresponding biaryl products in
good yields.
In most cases, the cross‐coupling reaction with aryl
iodides such as iodobenzene afforded the corresponding
product in excellent yield (Table 2, entry 1). This result
is better than that using some other catalysts such as
NHC‐Pd/SBA‐15/IL.[29]
Bromobenzene and aryl bromides that contain alkyl
substituents at the meta position showed almost quantita-
tive yields. However, for our catalytic system, for aryl bro-
mides, all electron‐withdrawing or electron‐donating
groups such as ―NO2 and ―CH3 afford the correspond-
ing products in high yields (Table 2, entries 3 and 4).
Aryl halides with ortho substitution are poor sub-
strates because of their steric hindrance. This is seen in
the case of 2‐bromopyridine and 2‐bromothiophene. 2‐
Bromopyridine reacted with phenyltrimethoxysilane in
the Hiyama cross‐coupling reaction, and 84% yield was
obtained. But for 2‐bromothiophene, the yield was
decreased to 63%, because of the possibility of the S–Pd
coordination (Table 2, entries 5 and 6).
FIGURE 5 Recyclability of catalyst in Hiyama cross‐coupling
reaction
Bromonaphthalene and aryl bromides with carbonyl
substituents at the para position also led to the corre-
sponding cross‐coupled products in excellent yields
(Table 2, entries 7 and 8).
1‐Chloro‐4‐nitrobenzene and phenyltrimethoxysilane
coupled to afford the corresponding biaryl products in
FIGURE 6 Time course of the Hiyama cross‐coupling reaction

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KARAMI ET AL.
TABLE 3 Comparison with reported results for Hiyama cross‐coupling reaction using Pd catalysts
Entry
Catalyst
R1
X
Activator
Temp. (°C)
Time
TOF (h−1
)
Ref.
1
Fe3O4@SiO2/APTMS/Pd(cdha)2
H
I
NaOH
100
5 min
5357
This work
2
3
4
5
6
7
8
9
Fe3O4@SiO2/APTMS/Pd(cdha)2
PdCl2
H
H
H
H
H
H
H
H
Br
Br
Br
I
NaOH
TBAF
100
100
100
100
90
5 min
10 h
5 min
5 min
6 h
5250
1.92
768
752
75.83
18.8
4.9
This work
[30]
[31]
[31]
[15]
[32]
[33]
[34]
Na2PdCl4
NaOH
NaOH
NaOH
TBAF
Na2PdCl4
Pd/Fe3O4
Br
I
SiO2@Fe3O4–Pd
Pd(acac)2
60
10 h
4 h
Br
I
TBAF
80
PS‐tsu‐Pd(II)
LiOH.H2O
100
10 h
16
observed that the peak of iodobenzene disappeared
completely after 5 min and biphenyl was identified as
the sole coupling product (Figure 6a). After using the cat-
alyst in the reaction, it was removed after 2 min and the
resulting filtrate was monitored for an additional reaction
time, but no cross‐coupling product was observed after
the removal of the catalyst (Figure 6b). This showed that
this catalytic system defines an efficient method for the
Hiyama cross‐coupling reaction of aryl halides in a green
solvent.
cross‐coupling reaction with these conditions could pro-
duce a wide variety of symmetric and asymmetric biaryl
compounds.
ACKNOWLEDGEMENTS
We gratefully acknowledge the financial support from the
Iranian Nanotechnology Initiative Council. This work
was supported by the Department of Chemistry, Isfahan
University of Technology.
ORCID
3.5 | Comparison with reported results for
Hiyama cross‐coupling reaction
Kazem Karami http://orcid.org/0000-0003-4488-1148
The optimized reaction conditions were chosen for the
Hiyama cross‐coupling reactions of iodobenzene and
bromobenzene with phenyltrimethoxysilane giving 100
and 98% yields in 5 min with a turnover frequency
(TOF) of 5357 and 5250 h−1 (Table 3, entries 1 and 2).
The catalytic performance was compared with that for
some previously reported types of supports and ligands.
In comparison with other palladium catalysts,
Fe3O4@SiO2/APTMS/Pd(cdha)2 nanoparticles exhibit
comparable yields with low catalyst loading in short reac-
tion times and high TOF under green solvent conditions.
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How to cite this article: Karami K, Jamshidian
N, Nikazma MM, Hervés P, Shahreza AR, Karami
A. Hiyama cross‐coupling reaction using Pd(II)
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