A New Nitrogen Pd(II) Complex Immobilized on Magnetic Mesoporous Silica: A Retrievable Catalyst for C–C Bond Formation

Article abstract of DOI:10.1007/s10562-020-03458-8

Abstract: A new nitrogen ligand, i.e. 1,3-di-(o-aminophenoxy)-2-propyl propargyl ether (DPPE), has been synthesized and characterized. Magnetic mesoporous silica composite (MNP@SiO₂-SBA) was obtained via embedding magnetite nano-particles (MNPs) between SBA-15 channels. DPPE palladium dichloride (MNP@SiO₂-SBA-DPPE-Pd(II)) was then prepared via click chemistry and fully characterized. The activity and recyclability of supported magnetic Pd(II) catalyst were evaluated in Heck coupling reaction after optimizing the optimal reaction conditions including solvent, amount of catalyst, base and temperature. Aryl iodides and aryl bromides showed enhanced activity compared to those of aryl chlorides in the Heck reaction. The catalyst was easily separated magnetically, reused in five runs sequentially, and no significant loss of activity was observed. Graphic Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-020-03458-8

Catalysis Letters
https://doi.org/10.1007/s10562-020-03458-8
A New Nitrogen Pd(II) Complex Immobilized on Magnetic Mesoporous
Silica: A Retrievable Catalyst for C–C Bond Formation
Samira Mousavi1 · Yagoub Mansoori1 · Ayat Nuri1 · Behzad Koohi‑Zargar2
Received: 15 August 2020 / Accepted: 9 November 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
A new nitrogen ligand, i.e. 1,3-di-(o-aminophenoxy)-2-propyl propargyl ether (DPPE), has been synthesized and charac-
terized. Magnetic mesoporous silica composite (MNP@SiO2-SBA) was obtained via embedding magnetite nano-particles
(MNPs) between SBA-15 channels. DPPE palladium dichloride (MNP@SiO2-SBA-DPPE-Pd(II)) was then prepared via
click chemistry and fully characterized. The activity and recyclability of supported magnetic Pd(II) catalyst were evaluated
in Heck coupling reaction after optimizing the optimal reaction conditions including solvent, amount of catalyst, base and
temperature. Aryl iodides and aryl bromides showed enhanced activity compared to those of aryl chlorides in the Heck
reaction. The catalyst was easily separated magnetically, reused in fve runs sequentially, and no signifcant loss of activity
was observed.
Graphic Abstract
Keywords Click reaction · Magnetic mesoporous silica · Heck reaction · Heterogenized catalyst
1 Introduction
Heck, Hiyama, Suzuki, Sonogashira, and Stille cross-cou-
pling reactions are those reactions that they are widely used
for C–C bond formation in the modern organic synthesis
[1]. The palladium-catalyzed arylation reaction of olefnic
compounds with aryl iodides in the presence of potassium
acetate was independently reported by Mizoroki [2] and
Heck [3] and then developed by Heck, Scheme 1.
* Yagoub Mansoori
ya_mansoori@yahoo.com; ya_mansoori@uma.ac.ir
1
Department of Applied Chemistry, Faculty of Science,
University of Mohaghegh Ardabili, Ardabil, Iran
Aryl, benzyl, and styryl halides were found to undergo
the reaction however, among the aryl compounds only
2
Farabi Chemical and Medical Laboratory, Sarcheshmeh Sq.,
Shams Alley, Farabi Building, Ardabil, Iran
Vol.:(0123456789)
1 3

S. Mousavi et al.
Scheme 1 Mizoroki–Heck
reaction
the iodides reacted rapidly [3]. Among various metals for
catalyzing these reactions, palladium is more preferred and
widely used due to enhanced activity and selectivity [4].
The Heck reaction is one of the most noted transformations
within the Pd-involved organic preparations. Nowadays,
Heck-type chemistry is a known method to assemble mol-
ecules via the formation of C–C bonds in both conventional
and modern organic syntheses [5]. The reaction has a great
potential for industrial applications, however, due to the
properties and activities of the existing catalysts, limited
industrial applications have been observed for the Heck
reaction [6]. During the last decades, the preparation of a
broad spectrum of supported Pd(II) complexes with dif-
ferent ligands as catalysts for coupling reactions have been
reported. Improving the reaction yields and decreasing reac-
tions time, processes costs, and byproducts are some of the
results of these investigations [7].
In recent years, anchoring catalysts on MNPs has been
extensively studied [8–11]. Magnetite nanoparticles are
nontoxic, highly dispersible, biocompatible, and they have a
Scheme 2 Synthesis of DPPE
Fig. 1 Mass spectra of DPPE
1 3

A New Nitrogen Pd(II) Complex Immobilized on Magnetic Mesoporous Silica: A Retrievable Catalyst…
nanocomposite materials. High selectivity and activity by
providing high density of single reaction sites via hetero-
genization of homogenous catalysts, and easy catalyst sepa-
ration and reusability are some of these advantages [19, 20].
There are plenty of reports on the incorporation of
magnetic mesoporous particles as support for catalyst and
preparing magnetically retrievable catalyst supports in the
literature [14, 21]. For example, Fu et al. reported that mag-
netic mesoporous silica functionalized with poly(m-ami-
nothiophenol) can rapidly adsorb Hg(II) ions. They showed
that, the Hg(II)-complexed adsorbent can be used as an
efcient catalyst for transformation of phenylacetylene to
acetophenone [22]. In another work, Jiang et al. supported
the polyoxometalate-based ionic liquid [(C4H9)3NCH3]3PM
o12O40 with short carbon chain onto magnetic mesoporous
silica microspheres with rough surface. The prepared cata-
lyst showed enhanced activity toward oxidative desulfuri-
zation of diesel with H2O2 as an oxidant in compared with
the smooth surface catalyst [23]. Sorokina et al. reported
that, pyridylphenylene dendrons immobilized on to magnetic
mesoporous silica act as efcient stabilizing molecules of
Pd species. Their amphiphilic nanocomposite demonstrates
excellent performance in Suzuki–Miyaura cross-coupling
reaction in the ethanol/water mixture due to the combina-
tion of hydrophilic support and hydrophobic dendrons [24].
Among the Pd-involved organic preparations, the Heck
reaction is one of the most noted transformations. Nowadays,
Heck-type chemistry is a well-known method to assemble
molecules via the formation of C–C bonds in both common
and modern organic syntheses [5, 25]. In recent years, the
preparation of a wide spectrum of supported Pd(II) com-
plexes with diferent ligands as catalysts for coupling reac-
tions has been reported. Improving the reaction yields and
decreasing reactions time, processes costs, and byproducts
are some of the results of these investigations [26, 27].
In the present study, a new ligand, i.e. 1,3-di-(o-
aminophenoxy)-2-propyl propargyl ether (DPPE), has been
synthesized and characterized. The prepared ligand can
be supported on the surface of metal oxides via a simple
click reaction. Separatedly, magnetic mesoporous silica was
obtained via embedding the MNPs between mesoporous
silica channels and then functionalized with azide. The
combination of SBA-15 porous structure with the magnetic
property of MNPs provides high density of catalytic sites
for enhanced activity along with the advantage of simple
magnetic decantation of the catalyst at the end of reaction.
DPPE was grafted onto the surface via click reaction and
then treated with a Pd(II) solution in EtOH to give a new
Pd(II)-supported magnetic catalyst (MNP@SiO2-SBA-
DPPE-Pd(II)). The obtained magnetic catalyst is a quite
efective catalyst in the Heck reaction. Furthermore, it is
compatible with the green chemistry principles and can be
Fig. 2 a 1H NMR (250 MHz) and b 13C NMR spectra (62.5 MHz) of
DPPE in CDCl3
high surface-to-volume ratio. Furthermore, MNP-supported
catalysts enjoy the beneft of easy and rapid magnetic sepa-
ration from diferent reaction mixtures [12–14].
It is highly recommended to coat MNPs prior to any treat-
ment because they agglomerate intrinsically due to strong
magnetic dipole–dipole interactions and high specifc sur-
face area [15, 16]. The most popular method to overcome
this problem is using MNPs in the form of a composite with
other metal oxides. Compositions of MNPs with diferent
forms of mesoporous silica such as MCMs and SBAs have
been widely investigated in recent years [17, 18]. This com-
bination will also give the advantages of both mesoporous
materials and magnetic nanoparticles to the MNP/silica
1 3

S. Mousavi et al.
Scheme 3 Synthesis of MNP@SiO2-SBA-DPPE-Pd(II)
2 Experimental
2.1 Materials
MNP@SiO2-SBA magnetic composite [28] and 3-azi-
dopropyltriethoxysilane [29] were prepared according to
reported methods in the literature. 1,3-Di-(o-nitrophenoxy)-
2-propanol (1) was synthesized via the method described
by Zhang et al. [30] via the reaction of o-nitrophenol and
1,3-dichloro-2-propanol in boiling DMF and in the presence
of K2CO3. Laboratory grade solvents used in this work were
dried according to reported procedures in the literature [31].
The remaining chemicals were obtained from Merck and
used as received.
2.2 Synthesis of 1,3‑Di‑(o‑nitrophenoxy)‑2‑Propyl
Propargyl Ether (3)
To a stirred solution of 1,3-di-(o-nitrophenoxy)-2-propanol
1 (0.830 g, 2.5 mmol) in dry DMF (5 ml) at 0 °C was added
NaH (0.132 g, 3 mmol; 60% dispersion in mineral oil) in
small portions under argon. The mixture was stirred in an ice
bath for 1 h and then propargyl bromide (0.31 ml, 6 mmol)
was added dropwise. The reaction mixture was warmed to
room temperature, stirred for additional 10 h, and quenched
by MeOH (7 ml). The white precipitate was fltered in vac-
uum, washed cold EtOH and dried to give 0.630 g product
[32]. (Yield: 66%, mp: 100–103 °C). FT-IR (KBr, cm–1):
3269 (m), 3061 (w), 2932 (w), 2869 (w), 1607 (m), 1521
(s), 1350 (s), 1280 (m), 1250 (m), 743 (m).
Fig. 3 FT-IR spectra (KBr) of: (a) DPPE; and (b) MNP@SiO2@
SBA-DPPE
Table 1 FT-IR characteristic absorptions of DPPE and MNP@SiO2-
SBA-DPPE-Pd(II)
Entry Functional group
Absorption (cm−1
)
References
1
2
3
4
5
6
7
Fe–O (stretching)
Si–O (stretching)
C=C (stretching, aromatic) 1451, 1520
N–H (bending) 1625
C–H (stretching, aliphatic) 2935
C–H (stretching, aromatic) 3050
NH2 (stretching)
560
1095
[25]
[8]
[40, 41]
[42]
[43]
[44]
[42]
2.3 Synthesis of 1,3‑Di‑(o‑aminophenoxy)‑2‑Propyl
3375
Propargyl Ether (DPPE)
To a rapidly stirred suspension of powdered zinc (1.740 g,
26.6 mmol) in 4.25 ml of 37% aqueous ammonia was added
easily separated from the reaction medium, recycled, and
re-used many times without signifcant loss of activity.
1 3

A New Nitrogen Pd(II) Complex Immobilized on Magnetic Mesoporous Silica: A Retrievable Catalyst…
Fig. 4 EDX analysis of MNP@
SiO2-SBA-DPPE Pd(II)
(62.5 MHz, CDCl3,δ): 141.1 (C–O, Ar.), 136.6 (C–N, Ar.),
122.0, 118.5, 115.4, 112.2, 79.8 (CH–O), 75.5 (≡C–C H2),
75.1 (≡C–H), 68.3 (O–CH2–CH), 57.9 (≡C–C H2). Mass:
(m/z)+: 312.15 (M+, 84%).
2.4 Synthesis of Azide Functionalized Magnetic
Nanocomposite MNP@SiO2‑SBA‑N3
A suspension of MNP@SiO2-SBA (1.000 g) in 50 ml of tol-
uene was irradiated in an ultrasonic bath for 10 min. To this
suspension, 3-azidopropyltriethoxysilane (2.0 ml, 9.7 mmol)
was added, and the mixture was stirred for 16 h at 80 °C
under argon. The reaction mixture was then cooled, fltered
and washed with toluene several times and then dried at
45 °C in a vacuum oven [29]. FT-IR (KBr, cm–1): 2935 (w),
2869 (w), 2104 (m), 1628 (m), 1526 (w), 1448 (w), 1088
(s), 735 (m).
Fig. 5 Wide angle powder XRD patterns of of: (a) MNP@SiO2-SBA;
and (b) MNP@SiO2-SBA-DPPE Pd(II)
a solution of 3 (1.000 g, 2.65 mmol) in 4.25 ml of THF. The
mixture was refuxed for 6 h and then fltered. The fltrate
was extracted with three 15 ml portions of ethyl acetate/
water (50:50) mixture, and the combined extracts evapo-
rated to dryness. The obtained residual orange oil chroma-
tographed on 20 cm×20 cm silica gel covered glass plates
using 75:25 petroleum ether/acetone eluent to aford to give
0.510 g of orange oily product [33]. (Yield: 38%). FT-IR
(KBr, cm–1): 3294 (s), 3048 (w), 2935 (w), 2869 (w), 1648
(s), 1526 (m), 1448 (w), 1310 (w), 1032 (m), 735 (m). 1H-
NMR (250 MHz, CDCl3 δ): 6.85–7.00 (m, 2H); 6.70–6.80
(m, 2H); 4.47–4.50 (m, 2H); 4.40–4.46 (m, 1H); 4.23–4.32
(m, 4H); 3.90 (br, s, 4H); 2.54–2.56 (m, 1H). 13CNMR
2.5 Synthesis of MNP@SiO2‑SBA‑DPPE via Click
Reaction
In a round-bottomed fask MNP@SiO2-SBA-N3 (1.000 g)
was dispersed in 20 ml of t-BuOH/water (1:1) containing
CuSO4 (0.330 g, 1.32 mmol), sodium ascorbate (1.070 g,
5.4 mmol) and DPPE (1.200 g, 4.8 mmol). The mixture was
irradiated in an ultrasonic bath for 15 min and stirred at
80 °C for 24 h under argon. The magnetic particles were then
magnetically decanted, washed with EtOH and then dried in
a vacuum oven at 80 °C [29]. FT-IR (KBr, cm−1): 3397 (br,
s), 3067 (w), 2935 (w), 2869 (w), 2104 (m), 1628 (m), 1526
(w), 1448 (w), 1088 (s), 735 (m).
1 3

S. Mousavi et al.
mixture was stirred at 120 °C. The catalyst was magnetically
decanted as the reaction was completed (followed by TLC)
and the mixture was analyzed by GC. The samples for NMR
analysis were chromatographed on glass plates covered by
silica gel.
3 Results and Discussion
3.1 Preparation and Characterization
of the Catalyst
The new ligand (DPPE) has been prepared in two
steps as shown in Scheme 2. In the frst step, 1,3-di-(o-
aminophenoxy)-2-propanol (1) was etherifed with propargyl
bromide 2 [32]. Selective reduction of nitro groups in the
presence of ethynyl group by conventionl methods such as
Pd/C/hydrazine; Pd/C/NaBH4; Fe/HCl; Sn/HCl, and Zn/HCl
were unsuccessful. This was done by the specifc method
described by Kovar and Arnold for preparation of the ethy-
nyl substuted o-diamines [33].
Common spectroscopy methods were applied to confrm
the structure of DPPE. In the mass spectrum (Fig. 1), molec-
ular ion peak appears at m/e=312.15 (84%).
Figure 2a and b present the 1H NMR and 13C NMR spec-
tra of DPPE, respectively. As Fig. 1a shows, the acetylenic
proton is observed as a multiplet at 2.54–2.56 ppm. The
protons related to amino groups and methylenes adjacent
to oxygens of the aromatic rings appear as a broad singlet
centered at 3.90 ppm, and a multiplet at 4.23–4.32 ppm,
respectively. The protons of chiral carbon and methylene
group adjacent to C≡C bond are seen as two multiplets at
4.40–4.47 ppm and 4.47–4.50 ppm, respectively. The aro-
matic rings protons appear at 6.70–6.80 ppm. In Fig. 2b,
the observed 11 signals are compatible with the structure of
DPPE. The prepared ligand can be supported on the surface
of metal oxides via a simple click reaction.
Fig. 6 TEM images of magnetic SBA
Magnetite nanoparticles were prepared via co-precipi-
tation method and then covered by a silica layer and then
embedded into mesoporous silica (SBA-15) [28]. The com-
bination of SBA-15 porous structure with the magnetic
property of MNPs provides high density of catalytic sites
for enhanced activity along with the advantage of simple
magnetic decantation of the catalyst at the end of reaction.
The as-prepared MNP@SiO2-SBA particles were then
silylated with 3-azidopropyltrimethoxysilane via post-syn-
thesis grafting technique described by Malvi et al. [29]. The
azide functionalized magnetic mesoporous silica was further
functionalized with DPPE via the click methodology, and
then treated with PdCl2 solution in EtOH to aford supported
Pd(II)-complex, Scheme 3.
2.6 Synthesis of MNP@SiO2‑SBA‑DPPE‑Pd(II)
DPPE functionalized magnetic mesoporous silica particles
(1.000 g) were dispersed in a PdCl2 (0.03 g, 0.17 mmol)
solution in EtOH (8 ml) in an ultrasonic bath for 15 min, and
then stirred at room temperature for 12 h. The catalyst was
decanted magnetically, washed several times with EtOH and
then dried in vacuum at 45 °C [34].
2.7 General Procedure for the Heck Reaction
Typically, the supported catalyst (1.10 mol%) was dispersed
in 1 ml N-methyl-2-pyrrolidone (NMP) through 8 min ultra-
sonication. Olefn (1.00 mmol), aryl halide (1.00 mmol),
and K2CO3 (1.5 mmol) were then added and the reaction
The FT-IR spectra of DPPE and MNP@SiO2-SBA-
DPPE are shown in Fig. 3a and b. Figure 3b shows the
1 3

A New Nitrogen Pd(II) Complex Immobilized on Magnetic Mesoporous Silica: A Retrievable Catalyst…
Fig. 7 Magnetization curves for the MNP, MNP@SiO2 and MNP@SiO2-SBA-DPPE-Pd(II)
Table 2 Magnetic properties of the prepared materials
Surface qualitative elemental analysis at random points
by EDX confrmed the presence of palladium atoms, Fig. 4.
In addition, the EDX spectrum shows the signals of car-
bon, nitrogen, oxygen, silicon, and iron, and the presence
of these elements in the supported catalyst. Atomic absorp-
tion spectroscopy revealed that the palladium loading is
0.10 mmol g−1 (1.10 wt%).
Sample
Mas (emu g−1
)
Mbr (emu g−1
)
Hcc (Oe) Mr/Mds
MNPs
MNP@SiO2
MNP@SiO2@
SBA@DPPE-
Pd(II)
78.14
34.52
1.56
4.03
1.91
0.08
18.6
22.2
29.6
0.05
0.06
0.05
Figure 5a and b shows the XRD patterns of MNP and
MNP@SiO2-SBA-DPPE-Pd(II). Both samples exhibit well-
resolved difraction peaks that can be indexed as (220),
(311), (400), (422), (511) and (440) planes associated with
cubic magnetite nanoparticles (JCPDS-ICDD Copyright
1938, fle No. 01–1111) with the Fd−3 m space group [35].
However, due to reposing of MNPs between the channels
of mesoporous silica, intensities of these characteristic dif-
fraction peaks were attenuated in the pattern of supported
catalyst, Fig. 5b.
aSaturation magnetization
bRemanent magnetization
cCoercive force
dRemanence ratio
characteristic peak of magnetite at 560 cm−1. The strong
absorption band observed at 1095 cm−1 (νas Si–O–Si)
reveals the formation of MNP@SiO2 nano-composite [8].
Figure 3b clearly shows the characteristic peaks related to
the ligand. The adsorption bands observed at 1451 cm−1,
and 1520 cm−1 are related to C=C stretching vibrations
of aromatic ring. The N–H bending vibration appeared at
1625 cm−1. The stretching vibrations related to aliphatic
C–H, aromatic C–H, and NH2 groups appear at 2935 cm−1,
3050 cm−1, and 3375 cm−1, respectively. The FT-IR data are
summarized in Table 1.
The image obtained by TEM also confrmed ordered
structure of magnetic SBA (Fig. 6). Highly ordered arrays of
1D mesoporous channels in which MNPs with 20 to 50 nm
diameter are located between the channels of MNP@SiO2@
SBA are seen in this image.
Figure 7 shows the hysteresis loops of MNP, MNP@SiO2
and MNP@SiO2-SBA-DPPE-Pd(II) at room temperature
and the results are tabulated in Table 2. Superparamagnetic
1 3

S. Mousavi et al.
Table 3 Optimization of conditions for Heck reaction
Br
Cat., Base
Solvent,
+
∆
Entry
Solvent
Pd (mol%)
Base
Temperature (°C) Conversion (%)a
TONb/TOF (h−1 c
)
1
2
3
4
5
6
7
8
EtOAc
Ethanol
CHCl3
Acetone
DMF
DMAc
DMSO
H2O
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.07
0.15
0.2
0.1
0.1
0.1
–
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Et3N
60
60
60
Trace
Trace
Trace
Trace
60
53
Trace
22
90
52
22
Trace
61
64
71
36
55
47
Trace
1
88
–
–
–
60
–
120
120
120
60
529/176
–
9
120
120
120
120
120
120
120
120
120
120
80
901/300
520/173
220/73
–
10
11
12
13
14
15
16
17
18
19
20
21
22
Cs2CO3
Pyridine
NaOAc
d
K2CO3e
637/212
709/236
363/121
548/182
472/157
–
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
100
140
120
880/293
–
Optimal reaction conditions are highlighted in bold
Reaction conditions: 1-Bromonaphthalene (1.0 mmol), styrene (1.0 mmol), solvent (1 ml), base (1.5 mmol) and reaction time 3.0 h
aDetermined by GC analysis
bTurn over number: TON=The number of moles of desired product/the number of moles of metal active sites
cTurn over frequency: TOF=The number of moles of reactant converted/(The number of moles of metal active sites × Time in hours)
d1.0 mmol
e2.0 mmol
behavior of the samples is shown by small remanence, hys-
teresis, coercivity values, and narrow width of the loop as
seen in the inset of Fig. 7 [36, 37]. The saturation mag-
netizations of MNP, MNP@SiO2 and MNP@SiO2-SBA-
DPPE-Pd(II) are 78.14, 34.52, and 1.56 emu g−1, respec-
tively. Dropping of the maximal saturation magnetization
of supported catalyst may be due to the entangling of MNPs
between SBA channels.
3.2 Heck Coupling Reaction
Styrene and 1-bromonaphthalene were chosen as the model
compounds for optimizing the Heck coupling reaction condi-
tions. Reaction parameters such as the solvent, base, amount
of base, amount of catalyst, and reaction temperature were
studied. The results are shown in Table 3 and Fig. 8a–c.
According to solvent screening (Entries 1 to 9), the NMP
solvent is the best choice due to the highest yield (Entry
9, 90% yield). The efect of the base and its quantity were
also evaluated (Entries 9 to 13). The highest conversion is
achieved with the K2CO3 base (Entry 9, 90% yield). Higher
1 3

A New Nitrogen Pd(II) Complex Immobilized on Magnetic Mesoporous Silica: A Retrievable Catalyst…
moderate reactivity under the applied reaction conditions
excluding chlorobenzene (Entries 14 to 16).
A possible mechanism for the Heck cross-coupling reac-
tion catalyzed by a supported Pd(II) complex can be pro-
posed as Scheme 4. The mechanism is suggested based on
the mechanism described by Shaw et al. [38, 39], in which
a Pd(II)/Pd(IV) cycle is involved. In the proposed mecha-
nism, olefn coordinates of to the supported Pd(II), and then
an alkyl σ-complex is formed by attacking the nucleophile
−
(KCO3 ) on the coordinated complex. The aryl halide oxi-
dizes the Pd(II) center, the attached nucleophile is released
and the alkene coordinates to the Pd(IV) complex, again.
The catalyst is regenerated via β-hydride elimination and
base-induced removal of hydrogen halide that gives the
desired product.
3.3 Characterization of the Recycled Catalyst
In order to indicate the stability of MNP@SiO2-SBA-DPPE-
Pd(II), after using in the coupling reaction of bromonaph-
thalene and styrene, the catalyst was collected and charac-
terized by FT-IR, Fig. 9a and b. As seen, the spectra of the
recovered catalyst does not show any signifcant changes in
comparison with the fresh catalyst.
3.4 Comparison of the Catalyst
The comparison of the prepared magnetic catalyst with a
few literature reported catalysts in the coupling reaction of
iodobenzene with styrene reveals that our prepared mag-
netic catalyst has enhanced reactivity, Table 5. In addition,
the mesoporous structure of the prepared catlyst provides a
very high srface area in compared with the most catalysts
listed in Table 5. The prepared catlyst has also enjoys the
beneft of magnetic separation and easy recovering process
as the major advantage. High thermal stability is an other
advantage of the our prepared catlyst over the catalysts listed
catalyst in Table 5.
Fig. 8 Optimization of the Heck reaction conditions: a solvent; b cat-
alyst loading; and c Base. Reaction conditions: 1-Bromonaphthalene
(1.0 mmol), styrene (1.0 mmol), solvent (1 ml)
3.5 Recyclability of the Catalyst
or lower quantities of the base than that of 1.5 molar ratio
diminish the reaction conversion (Entries 14 and 15). The
optimization of catalyst dosage shows that using the cata-
lyst containing 0.1 mol% Pd(II) is the optimal value (Entry
9, 90% yield). It should be noted that the reaction does not
proceed properly at the temperatures lower or higher than
120 °C (Entries 19 to 21) and in the absence of the catalyst
(Entry 22).
Supported catalysts are usually prepared via complicated
and expensive routes. Therefore, it is necessary to pay suf-
fcient attention to retrieving of a used catalyst. The sta-
bility and re-usability of the magnetic catalyst were tested
in the Heck coupling reactions of 1-bromonaphthalene and
ethyl acrylate, Fig. 10. After each reaction, the catalyst was
collected magnetically, washed with ethyl acetate, and then
dried. As shown, the conversion reaches to 97.3% in the
frst run and then slightly dropped to 90.1% during fve
consecutive runs of the Heck reaction. Therefore, it can be
concluded that the prepared supported catalyst is active and
recyclable.
Various aryl halides were subjected to the optimized reac-
tion conditions with diferent olefns, Table 4. As shown,
aryl iodides and aryl bromides showed excellent conver-
sions and TOFs (Entries 1 to 13), excluding 2-bromopyri-
dine (Entry 13, conversion 34%). Aryl chlorides showed
1 3

S. Mousavi et al.
Table 4 Heck reaction of aryl halide with olefn catalyzed by the supported Pd(II) complex
X
R'
Cat., Base
+
R'
Solvent, 120°C
R
R
Entry
1
Aryl halide
Olefn
Product
m.p. (°C)
Found Reported [Ref.]
Time (h) TON/TOF (h−1
)
Conversion (%)
96
Oil
Oil [45]
2
2
962/320
971/324
O
O
O
O
I
I
2
3
118–
120
118–121 [46]
97
97
74–76
76–78 [47]
3
965/321
Br
N
N
4
5
Oil
Oil
Oil [48]
Oil
3
2
929/309
865/288
93
87
O
Br
Br
O
O
O
6
7
145–
147
148–150 [49]
151–153 [18]
4
764/254
601/200
76
60
O
Br
O
151–
152
18
H2N
H2N
Br
Br
H2N
8
9
70–72
Oil
72–74 [17]
Oil [45]
4
2
575/191
536/178
58
54
O
O
O
O
H2N
O
O
O
O
Br
1 3

A New Nitrogen Pd(II) Complex Immobilized on Magnetic Mesoporous Silica: A Retrievable Catalyst…
Table 4 (continued)
Entry
Aryl halide
Olefn
Product
m.p. (°C)
Time (h) TON/TOF (h−1
)
Conversion (%)
50
Found Reported [Ref.]
10
118–
120
118–121 [46]
2
501/167
Br
Br
11
71–73
70–71 [49]
3
901/300
90
12
13
78–79
77–78
80–81 [50]
78–79 [26]
4
972/324
335/111
97
34
Br
O
O
O
O
18
N
Br
N
14
151–
152
151–153 [18]
18
427/142
43
H2N
Cl
Cl
H2N
15
16
70–72
37–39
72–74 [17]
36–38 [45]
18
18
408/136
40.8
H2N
O
O
O
O
H2N
–
Trace
O
O
O
O
Cl
Reaction conditions: Aryl halide (1.0 mmol), olefn (1.0 mmol), solvent (1.0 ml), Pd(II) (0.1 mol%), and base (1.5 mmol)
remaining aliquat by atomic absorption which was found to
be 0.0000116 mmol ml−1. The very low Pd concentration
proves that no considerable metal leaching occurred in the
reaction medium. Therefore, the heterogeneous palladium is
responsible for completion of the reaction.
3.6 Leaching Study
In order to confrm the stability and heterogeneous nature of
MNP@SiO2-SBA-DPPE-Pd(II), after using in the coupling
reaction of bromonaphthalene and styrene, the catalyst was
collected. The palladium concentration was measured in the
1 3

S. Mousavi et al.
Scheme 4 The proposed Pd(II)/
Pd(IV) catalytic cycle for the
Heck cross coupling reaction in
the presence of MNP@SiO2-
SBA-DPPE-Pd(II)
4 Conclusion
In summary, the synthesis, characterization, and application
of an efcient and retrievable magnetic catalyst are reported.
The catalyst was obtained by supporting a Pd(II) complex
on magnetic mesoporous silica. For this purpose, DPPE was
synthesized, characterized, and then supported on magnetic
SBA via the click reaction. The supported ligand was treated
with a Pd(II) solution to aford a supported Pd(II) catalyst.
The obtained magnetic catalyst was fully characterized by
the FT-IR, TGA, SEM, TEM, XRD, EDX, BET, and VSM
analyses. It was shown that, the prepared catalyst could ef-
ciently catalyze the Heck cross-coupling reaction of aryl hal-
ides and olefns. Excellent conversions were obtained and
the recovering ability of the catalyst was shown by mag-
netic separation and re-using of the recovered catalyst. The
recovered catalyst was reused several times with signifcant
deactivation.
Fig. 9 FT-IR spectra of: (a) recovered MNP@SiO2-SBA-DPPE-
Pd(II) and; (b) Fresh MNP@SiO2-SBA-DPPE-Pd(II)
1 3

A New Nitrogen Pd(II) Complex Immobilized on Magnetic Mesoporous Silica: A Retrievable Catalyst…
Table 5 Comparison of the prepared catalyst with other catalysts for Heck cross-coupling reactions from iodobenzene with styrene
Entry
Catalyst
Conditions
Time (h)
Yield (%)
TOF (h−1
)
References
1
2
3
4
5
6
7
Agarose-Pd(0)
PdNP-SβCD
Palladacycle
Pd/C particles
Solvent free, Et3N, 120 °C
H2O, K2CO3, 100 °C
DMA, Et3N, 140 °C
2.0
2.0
18.0
24
6.0
1.5
3.0
2
90
99
100
23
92
93
80
96
95
97
87
91
28
0.2
217
62
53
192
78
[51]
[52]
[53]
[54]
[55]
[56]
[57]
[25]
H2O, Et3N, 100 °C
Pd–MPTA-1
H2O, Cs2CO3, 100 °C
PEG-400, CH3COONa, 80 °C
Et3N, DMA, 80 °C
NMP, K2CO3, 120 °C
PEG-400, Na2CO3, 120 °C
NMP, K2CO3, 120 °C
Pd(OAc)2 (ligand Free)
1′-Carbopalladated complexes
The supported NHC Pd(II) complex
Pd-imi@MCM-41/Fe3O4
MNP@SiO2-SBA-DPPE-Pd(II)
8
9a
10
0.8
1.0
[19]
This work
324
aThe investigation was studied for the Heck cross-coupling reaction of iodobenzene and methylacrylate
10. Tayeb Oskoie P, Mansoori Y (2018) J Part Sci Technol 4:1
11. Rahimi L, Mansoori Y, Nuri A, Esquivel D (2020) ChemistrySe-
lect 5:11690
12. Arnaudov M (1999) Spectrosc Lett 32:165
13. Baig RN, Varma RS (2013) Chem Commun 49:752
14. Nuri A, Mansoori Y, Bezaatpour A, Shchukarev A, Mikkola J-P
(2019) ChemistrySelect 4:1820
15. Rutnakornpituk M, Puangsin N, Theamdee P, Rutnakornpituk B,
Wichai U (2011) Polymer 52:987
16. Donescu D, Raditoiu V, Spataru CI, Somoghi R, Ghiurea M,
Radovici C, Fierascu RC, Schinteie G, Leca A, Kuncser V (2012)
Eur Polym J 48:1709
17. Yasuhara A, Kasano A, Sakamoto T (1999) J Org Chem 64:2301
18. Yang J-S, Wang C-M, Hwang C-Y, Liau K-L, Chiou S-Y (2003)
Photochem Photobiol Sci 2:1225
19. Ghorbani-Choghamarani A, Tahmasbi B, Hudson RHE, Heidari
A (2019) Microporous Mesoporous Mater 284:366
20. Tahmasbi B, Ghorbani-Choghamarani A (2019) New J Chem
43:14485
21. Martínez-Edo G, Balmori A, Pontón I, Martí del Rio A, Sánchez-
García D (2018) Catalysts 8:617
Fig. 10 Recycling of MNP@SiO2-SBA-DPPE-Pd(II) for the Heck
cross-coupling reaction of 1-bromonaphthalene and ethylacrylate
22. Fu Y, Sun Y, Chen Z, Ying S, Wang J, Hu J (2019) Sci Total
Environ 691:664
23. Jiang W, Jia H, Fan X, Dong L, Guo T, Zhu L, Zhu W, Li H (2019)
Appl Surf Sci 484:1027
Acknowledgements The financial support provided by Gradu-
ate Council of the University of Mohaghegh Ardabili is gratefully
acknowledged.
24. Sorokina SA, Kuchkina NV, Lawson BP, Krasnova IY, Nemygina
NA, Nikoshvili LZ, Talanova VN, Stein BD, Pink M, Morgan DG,
Sulman EM, Bronstein LM, Shifrina ZB (2019) Appl Surf Sci
488:865
25. Nuri A, Mansoori Y, Bezaatpour A (2019) Appl Organomet Chem
33:e4904
References
26. Kanagaraj K, Pitchumani K (2013) Chem Eur J 19:14425
27. Nuri A, Vucetic N, Smått J-H, Mansoori Y, Mikkola J-P, Murzin
DY (2019) Catal. Lett. 149(7):1941–1951
1. Chen Y, Wang M, Zhang L, Liu Y, Han J (2017) RSC Adv
7:47104
2. Tsutomu M, Kunio M, Atsumu O (1971) Bull Chem Soc Jpn
44:581
28. Wang S, Wang K, Dai C, Shi H, Li J (2015) Chem Eng J 262:897
29. Malvi B, Sarkar BR, Pati D, Mathew R, Ajithkumar TG, Sen
Gupta S (2009) J Mater Chem 19:1409
3. Heck RF, Nolley JP (1972) J Org Chem 37:2320
4. Nasrollahzadeh M, Issaabadi Z, Tohidi MM, Mohammad Sajadi
S (2018) Chem Rec 18:165
30. Zhang W, Liu S, Ma C, Jiang D (1998) Polyhedron 17:3835
31. Armarego WLF, Chai CLL (2003) Purifcation of laboratory
chemicals, 5th edn. Butterworth-Heinemann, Burlington
32. Lv G, Mai W, Jin R, Gao L (2008) Synlett 2008:1418
33. R.F. Kovar, F.E. Arnold, US Patent 3,975,444 (1976)
34. Peng X, Zhao Y, Yang T, Yang Y, Jiang Y, Ma Z, Li X, Hou J, Xi
B, Liu H (2018) Microporous Mesoporous Mater 258:26
35. Hanawalt JD, Rinn HW, Frevel LK (1938) Ind Eng Chem Anal
Ed 10:457
5. Beletskaya IP, Cheprakov AV (2000) Chem Rev 100:3009
6. C.P. Mehnert, J. Y. Ying, Chem Commun, 2215 (1997)
7. Polshettiwar V, Molnár Á (2007) Tetrahedron 63:6949
8. Kang T, Li F, Baik S, Shao W, Ling D, Hyeon T (2017) Biomateri-
als 136:98
9. Moon SH, Noh S-H, Lee J-H, Shin T-H, Lim Y, Cheon J (2017)
Nano Lett 17:800
1 3

S. Mousavi et al.
36. Choubey J, Bajpai AK (2010) J Mater Sci Mater Med 21:1573
37. Basavaraja C, Jo EA, Huh DS (2010) Mater Lett 64:762
38. B.L. Shaw, Chem Commun, 1361 (1998)
50. Prevost MS, Delarue-Cochin S, Marteaux J, Colas C, Van Rent-
erghem C, Blondel A, Malliavin T, Corringer P-J, Joseph D (2013)
J Med Chem 56:4619
39. Shaw B (1998) New J Chem 22:77
51. Firouzabadi H, Iranpoor N, Kazemi F, Gholinejad M (2012) J Mol
Catal A Chem 357:154
40. Nieva Lobos ML, Sieben JM, Comignani V, Duarte M, Volpe MA,
Moyano EL (2016) Int J Hydrogen Energy 41:10695
41. Moradi P, Hajjami M, Tahmasbi B (2020) Polyhedron 175:114169
42. Danon A, Stair PC, Weitz E (2011) J Phys Chem C 115:11540
43. Mansoori Y, Khodayari A, Banaei A, Mirzaeinejad M, Azizian-
Kalandaragh Y, Pooresmaeil M (2016) RSC Adv 6:48676
44. Rahmaninia A, Mansoori Y, Nasiri F, Bezaatpour A, Babaei B
(2019) J Part Sci Technol 5:47
52. Khalaf-Nezhad A, Panahi F (2014) ACS Sustain Chem Eng
2:1177
53. Gruber AS, Zim D, Ebeling G, Monteiro AL, Dupont J (2000) Org
Lett 2:1287
54. Cassez A, Kania N, Hapiot F, Fourmentin S, Monfier E, Ponchel
A (2008) Catal Commun 9:1346
55. Mondal J, Modak A, Bhaumik A (2011) J Mol Catal A Chem
350:40
45. Sun P, Zhu Y, Yang H, Yan H, Lu L, Zhang X, Mao J (2012) Org
Biomol Chem 10:4512
56. Han W, Liu N, Liu C, Jin ZL (2010) Chin Chem Lett 21:1411
57. Rosol M, Moyano A (2005) J Organomet Chem 690:2291
46. Górski B, Talko A, Basak T, Barbasiewicz M (2017) Org Lett
19:1756
47. Inomata S, Hiroki H, Terashima T, Ogata K, Fukuzawa S (2011)
Tetrahedron 67:7263
Publisher’s Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional afliations.
48. Huang S-H, Chen J-R, Tsai F-Y (2010) Molecules 15:315
49. Yu L, Huang Y, Wei Z, Ding Y, Su C, Xu Q (2015) J Org Chem
80:8677
1 3