Air-Stable Fe3O4@SiO2-EDTA-Ni(0) as an Efficient Recyclable Magnetic Nanocatalyst for Effective Suzuki-Miyaura and Heck Cross-Coupling via Aryl Sulfamates and Carbamates

Article abstract of DOI:10.1002/aoc.5662

The synthesis of inexpensive and novel air-stable Ni(0) nanoparticles immobilized on the EDTA-modified Fe₃O₄@SiO₂ nanocatalyst was investigated in Suzuki-Miyaura and Heck cross-coupling reactions. This catalytic system displayed a greatly improved substrate scope for the carbon–carbon bond formations starting from a wide range of green and economical electrophiles aryl and heteroaryl carbamates and sulfamates via highly efficient method under mild, operationally simple reaction conditions. The synthesized heterogeneous catalyst was also fully characterized by FT-IR, TEM, XRD, DLS, FE-SEM, UV–Vis, EDX, XPS, TGA, NMR, VSM, ICP and elemental analysis techniques. The heterogeneous magnetic nanocatalyst can easily be recovered by an external magnetic field and reused for the next reactions for at least seven times with negligible leaching of catalyst and no substantial decrement in the activity. All these highlights have made the present protocol an interesting, simple and environmentally benign process with low catalyst loading and easy manipulations.

Full text of DOI:10.1002/aoc.5662

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Received: 23 November 2019
DOI: 10.1002/aoc.5662
Revised: 15 February 2020
Accepted: 29 February 2020
F U L L P A P E R
Air-Stable Fe3O4@SiO2-EDTA-Ni(0) as an Efficient
Recyclable Magnetic Nanocatalyst for Effective Suzuki-
Miyaura and Heck Cross-Coupling via Aryl Sulfamates and
Carbamates
Iman Dindarloo Inaloo1
Mohsen Esmaeilpour1
| Sahar Majnooni2 | Hassan Eslahi1
|
1Chemistry Department, College of
The synthesis of inexpensive and novel air-stable Ni(0) nanoparticles
immobilized on the EDTA-modified Fe3O4@SiO2 nanocatalyst was investi-
gated in Suzuki-Miyaura and Heck cross-coupling reactions. This catalytic sys-
tem displayed a greatly improved substrate scope for the carbon–carbon bond
formations starting from a wide range of green and economical electrophiles
aryl and heteroaryl carbamates and sulfamates via highly efficient method
under mild, operationally simple reaction conditions. The synthesized hetero-
geneous catalyst was also fully characterized by FT-IR, TEM, XRD, DLS,
FE-SEM, UV–Vis, EDX, XPS, TGA, NMR, VSM, ICP and elemental analysis
techniques. The heterogeneous magnetic nanocatalyst can easily be recovered
by an external magnetic field and reused for the next reactions for at least
seven times with negligible leaching of catalyst and no substantial decrement
in the activity. All these highlights have made the present protocol an interest-
ing, simple and environmentally benign process with low catalyst loading and
easy manipulations.
Sciences, Shiraz University, Shiraz, Iran
2Department of Chemistry, University of
Isfahan, Isfahan, 81746-73441, Iran
Correspondence
I. Dindarloo Inaloo, Chemistry
Department, College of Sciences, Shiraz
University, Shiraz, Iran.
Email: iman.dindarlooinaloo@gmail.com
K E Y W O R D S
C-O activation, cross-couplings, magnetic nanoparticles, nickel Nanocatalyst; carbamates;
Sulfamates
1 | INTRODUCTION
nucleophiles and aryl halides (I, Br, Cl) as the electro-
phile.[4] In the view of polyfunctionalized aromatics
Transition metal catalyzed cross-coupling reactions have
become one of the most useful achievements for the
synthesis of aromatic compounds in the last century.[1]
Having the importance of these compounds, they ubiqui-
tously are observed in pharmaceuticals, agrochemicals,
electronics and dyes.[2] In addition, the discovery and
development of effective and eco-friendly methods for
the C-C bond formation are of researcher's priority.[3]
The most common and popular techniques to access such
couplings are the usage of Pd catalyzed reaction between
importance in our lives, the high cost and toxicity of pal-
ladium metal and the stoichiometric quantity of halide
waste generated from these reactions, their application is
limited in both academic researches and industrial pro-
ductions importantly in medicinal and agricultural appli-
cations.[5] In recent years, the promising approach for the
development of sustainable and environmentally benign
cross-coupling processes has been noted using aryl
halides, nontoxic and safe electrophiles, and significantly
low cost and non-toxicity metals.[6] Thus, a wide library
Appl Organomet Chem. 2020;e5662.
wileyonlinelibrary.com/journal/aoc
© 2020 John Wiley & Sons, Ltd.
1 of 17
https://doi.org/10.1002/aoc.5662

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
2 of 17
DINDARLOO INALOO ET AL.
of Nickel-catalyzed C-C bond formations starting from
aryl boronic acids as nucleophilic coupling partners and
aromatic rings such as aryl ethers,[7] esters,[8] tosylates,[9]
sulfamates,[10] triflates,[11] phosphates,[12] carbonates[13]
and carbamates[14] as aryl halide surrogates have been
intensely investigated (Figure 1). As a result of these
studies, aryl carbamates and sulfamates were considered
ideal precursors because of their extensive derivatives,
availability, high stability and more efficiency under a
variety of reaction conditions.[15]
Despite these significant advances that happened in
recent years,[16–19] however, this reaction suffers from
several limitations including high catalyst loading, long
reaction times, elevated temperature regime and the
necessity to employ additional quantities of the phos-
phine ligands.[17] It should be noted that the use of large
quantities of ligands and metals as catalytic systems cre-
ate a remarkable complexity in the purification, increase
waste materials, decrease the safety of reaction and low
to modest yields have resulted in the most cases.[18]
Besides, most of the phosphorus ligands that are neces-
sary for doing these reactions have some drawbacks such
as thermal and air instability, high prices and difficulty
in the synthesis which are the main reasons for the grow-
ing interests in phosphine-free coupling reactions.[19]
In the world ahead, we can follow the progress of
nanotechnology especially nanomaterials in biomedicine,
biodetections, bioimaging, and drug delivery systems due
to their modified structure, increased activity, and surface
area to volume ratio.[20] They have also many appealing
applications in advanced industries such as textile, medi-
cine, and cosmetic industries.[21]
hyperthermia,[24] data storage,[25] magnetic resonance
imaging (MRI),[26] biomedical protection,[27] sensor
applications,[28] magnetic inks for jet printing,[29] and
catalysis.[30]
Scientists are commonly faced to the aggregation of
MNPs resulting from anisotropic dipolar attractions that
make them unstable in the reaction conditions.[31] To
surmount such drawbacks, they need some stabilizers as
protecting layer to solve the difficulty stabilizing of
which. These protection layers are vital to improve the
dispersibility of Fe3O4 NPs and to ensure the chemical
stability of them.[32] Magnetic core-shells, bearing both
advantages of cores and a wide spectrum of shells, have
absorbed much attention in the intensive researches.[33]
So far, many stabilizers have been reported as the
shell for this challenge such as Fe3O4/carbon,[34] Fe3O4/
meso-silica,[35] Fe3O4/polymer,[36] Fe3O4/MOF,[37] and
Fe3O4@SiO2.[38]
Abundant reports have been published in the litera-
ture using Fe3O4@SiO2 core-shells as ingredient of het-
erogeneous catalysts.[39] Although the heterogeneous
catalysts are usually less reactive than homogeneous
ones, they removed many limitations attributed to homo-
geneous catalysts including tedious workup and separa-
tion, contamination by the residual catalyst, low
reusability, expensive reaction conditions, and high-cost
preparation.[40] As a result, we found such heterogeneous
catalysts based on magnetic nanoparticles as applicable
catalysts for our ongoing researches.[41] Therefore, in this
work, we reported nickel nanoparticles immobilized on
EDTA-modified
Fe3O4@SiO2
(Fe3O4@SiO2-EDTA-
Ni(0) NPs) to catalyze the Suzuki-Miyaura and Heck
cross-couplings via aryl carbamates and sulfamates with-
out using any external ligand and the reducing agents
(Scheme 1).
Magnetic Fe3O4 nanoparticles (MNPs) are non-toxic,
biodegradable, and biocompatible particles that have
been attracted much attention giving to surface func-
tionalization ability makes them an exciting option for
the separation point of view.[22] They are interesting can-
didates for ongoing researches owing to their unique
physiochemical properties and outstanding usages
including medical diagnostics and therapeutics,[23]
2 | EXPERIMENTAL
2.1 | Chemicals and instrumentation
All chemicals and solvents were purchased from Sigma-
Aldrich and Merck chemicals and were used with no
more purifications. The purity of the products and the
FIGURE 1 Conventional phenol derivatives in cross-coupling
SCHEME 1 Suzuki-Miyaura and Heck Cross-Couplings of
reactions
Aryl Carbamates and Sulfamates

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
DINDARLOO INALOO ET AL.
3 of 17
progress of reactions were accomplished by TLC on
silica-gel Polygram SILG/UV254 plates. The FT-IR spec-
tra were recorded in the range of 500–3800 cm−1 using a
potassium bromide matrix with a Shimadzu FTIR-8300
spectrophotometer. NMR spectra were recorded on a
Bruker Advance DPX 250 MHz spectrometer using deu-
terated CDCl3 as solvent and TMS as the internal stan-
dard. X-ray diffraction patterns of the powder samples
are obtained with a Bruker AXS D8-advance X-ray dif-
fractometer using Cu Kα (λ = 1.5418) radiation. Trans-
mission electron microscopy (TEM) was performed on a
Philips EM208 transmission electron microscope at an
acceleration of 100 kV. Field emission scanning electron
microscopy (FESEM) pictures were observed on a Philips
XL-30ESEM. Dynamic light scatterings (DLS) were per-
formed using a HORIBA-LB550. The X-ray photoelectron
spectra (XPS) were analyzed on the PHI 5300x
multi-technique system with an Mg Kα X-ray source. N2
adsorption–desorption isotherms were measured at
was magnetically separated, washed with ethanol several
times and dried at 80 C for 10 hr. The coating of the
ꢀ
magnetic nanoparticles with silica was performed
according to the Stöber method. Briefly, in a typical pro-
cess, prepared Fe3O4 particles (0.5 g) were dispersed in a
mixture of deionized water (5 ml), ethanol (50 ml), and
tetraethoxy silane (TEOS) (0.20 ml) by ultrasonication for
0.5 min. Subsequently, 5.0 ml of NaOH (10 wt%) was
added dropwise. After being stirring for 30 min, the
obtained magnetic particles (Fe3O4@SiO2) were sepa-
rated with the magnet, washed with deionized water and
ethanol 3 times and dried at 80 ꢀC for 10 hr.
2.2.2 | Preparation of Fe3O4@SiO2 coated
by (3-aminopropyl)-triethoxysilane
(Fe3O4@SiO2-NH2 MNPs)[41]
The obtained Fe3O4@SiO2 NPs powder (1 g) was dis-
persed in 10 ml ethanol by sonicating for 5 min, and
then, 3-aminopropyl (triethoxy)silane (0.25 ml, 1 mmol)
was added to the mixture. After mechanical agitation
under the reflux conditions for 12 hr, the obtained
amino-functionalized Fe3O4@SiO2 NPs were separated
by magnetic decantation, washed with distilled water and
ethanol several times and finally, dried at 80 ꢀC for 6 hr.
ꢀ
−196 C using a Micromeritics ASAP 2000 instrument.
UV–vis spectra were recorded on a PerkinElmer Lambda
25 UV/Vis spectrometer having a quartz cuvette. The ele-
ments in the samples were probed by an energy-
dispersive X-ray (EDX) spectroscopy accessory to the
Philips scanning electron microscopy (SEM). The mag-
netic property of the catalyst was measured with a BHV-
55 vibrating sample magnetometer from −6000 Oe to
+6000 Oe at room temperature. Thermogravimetric anal-
ysis (TGA) was performed withꢀa TGA/SDTA851e under
air atmosphere from 50 to 700 C, with a heating rate of
20 ꢀC min−1 and an airflow rate of 30 ml min−1. Elemental
analysis was done on a Thermo Finnigan Flash EA-1112
CHNSO rapid elemental analyzer. The nickel content was
measured by inductively coupled plasma (ICP, Varian,
Vista-pro). Melting points were determined in open
capillaries using an Electrothermal 9100 apparatus.
2.2.3 | Preparation of Fe3O4@SiO2-
TCT NPs
The synthesis procedure for the magnetic Fe3O4@SiO2-
TCT composite nanoparticles is schematically illustrated
in Scheme 1. At the first, 1 g of Fe3O4@SiO2-NH2 (1 g)
and cyanuric chloride (TCT, 1 mmol, 0.185 g) were mixed
with 10 mL of THF using mechanical stirring to
produce a homogeneous suspension. Then, 0.17 mL
diisopropylethylamine (DIPEA, 1 mmol) was added to
which by using a syringe. In the next, the reaction was
stirred at room temperature for 16 hr with continuously
mechanical stirring. The functionalized cyanuric chloride
by Fe3O4@SiO2 NPs were separated by the magnet and
subsequently washed with deionized water and hot etha-
nol to remove the residue substrates. Finally, the sample
was dried in an oven at 60 ꢀC for 4 hr.
2.2 | General procedure
2.2.1 | Preparation of silica-coated
magnetic nanoparticles (Fe3O4@SiO2NPs)
Naked Fe3O4 nanoparticles were prepared by chemical
coprecipitation based on our previous report.[41] In a typi-
cal procedure, 1.3 g of FeCl3.6H2O (4.8 mmol) was dis-
solved in 30 ml of water to form a clear solution. Then,
1.0 g of polyvinyl alcohol (PVA 15000) as a surfactant and
0.9 g of FeCl2.4H2O were added and the resultant mixture
was stirred for 0.5 hr at 80 ꢀC. Next, hexamethylenetetra-
mine (HMTA) (1.0 mol/L) was added drop by drop with
vigorous stirring until pH 10 and a black product was
obtained. Afterward, the resulting nanomaterial (Fe3O4)
2.2.4 | Preparation of Fe3O4@SiO2-TCT-
NH2 NPs
1 g of Fe3O4@SiO2-TCTnanoparticles were dispersed in
5 ml of DMF in a 25 ml single-necked flask. Then,
0.25 ml of bis(3-aminopropyl)amine (2 mmol) and

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
4 of 17
DINDARLOO INALOO ET AL.
0.35 ml of DIPEA (2 mmol) were added to the mixture
and it was stirred at 80 C for 12 hr. The final particles
were separated from the solution with an external mag-
netic field, washed three times with ethanol and water,
and dried at 70 ꢀC for 4 hr.
evaporator. The product was purified by column chroma-
tography on silica gel using petroleum ether/ethyl acetate
(9:1) as the solvent or recrystallized (See supporting infor-
mation for 1H and 13C NMR of the products).
ꢀ
2.4 | General procedure for the cross-
coupling reaction of aryl carbamate and/or
aryl Sulfamates with olefins (heck cross-
coupling) (5a-5 t)
2.2.5 | Preparation of Fe3O4@SiO2-EDTA-
Ni(0) NPs
For the synthesis of Fe3O4@SiO2-EDTA NPs, 0.58 g of
EDTA (2 mmol) was dispersed in 20 ml of DMSO and
then, thionyl chloride (SOCl2, 2 mmol) was added
dropwise over 10 min through a constant pressure drop
funnel. Next, 1.5 g of Fe3O4@SiO2-TCT-NH2 was added
to the mixture and stirred for 2 hr at room temperature.
The functionalized ethylenediaminetetraacetic acid by
Fe3O4@SiO2-TCT-NH2 nanomaterial was then isolated
by an external magnet, washed with sodium carbonate
solution (0.1 mol L−1), acetone and deionized water, and
dried under vacuum at 60 ꢀC for 2 hr. The resultant
Fe3O4@SiO2-EDTA (1.5 g) was dispersed in 10 ml metha-
nol. Afterward, 1 g of nickel (II) acetate tetrahydrate
(4 mmol) was added to the mixture and stirred for 2 hr
under the reflux conditions. In the next step, 15 ml of
N2H4·H2O (1 equiv.) was slowly added to the obtained
mixture and it was allowed to be stirred for more 2 hr.
The resulting solid of Fe3O4@SiO2-EDTA-Ni(0) was sepa-
rated from the reaction mixture by an external magnet,
washed with ethanol and THF for three times, and dried
at 60 ꢀC for 3 hr to afford the final catalyst.
Aryl carbamate and/or aryl sulfamate (1.0 mmol), olefin
(1.0 mmol), potassium phosphate (2.0 mmol, 430 mg),
Fe3O4@SiO2-EDTA-Ni(0) NPs (0.018 g, 1 mol %) and eth-
ylene glycol (3.0 ml) were added into a round-bottomed
ꢀ
flask and stirred at 120 C for 6 hr under the air atmo-
sphere. The reaction process was monitored by TLC using
petroleum ether/ethyl acetate and/or GC. After the com-
pletion of the reaction, the reaction mixture was cooled to
room temperature and the nanocatalyst was separated
from the mixture with an external magnetic field. Then,
10 ml of distilled water was added and the reaction mix-
ture was subsequently extracted with ethyl acetate
(3 × 10 ml). The organic phases were dried over anhydrous
MgSO4 and the crude product was obtained after removing
the ethereal solution by a rotary evaporator. The product
was purified by column chromatography on silica gel
using petroleum ether/ethyl acetate (9:1) (See supporting
information for 1H and 13C NMR of the products).
3 | RESULTS AND DISCUSSION
2.3 | General procedure for the cross-
coupling reaction of aryl carbamate and/or
aryl Sulfamates with aryl Boronic acids
(Suzuki-Miyaura cross-couplings) (3a-3x)
The whole preparation route to Fe3O4@SiO2-EDTA-
Ni(0) NPs includes five steps is illustrated in Scheme 2.
The Fourier transform infrared (FT-IR) spectra of all syn-
thetic approaches of the final catalyst are shown in
Figure 2a-g. The FT-IR spectrum of Fe3O4 MNPs demon-
strates a band at 570 cm−1 due to the stretching vibration
of Fe-O and also, a broad band at 3441 cm−1 is attributed
to the presence of surface hydroxyl groups (Figure 2a).
The broad and intense band at 1090 cm−1 in the spec-
trum of Fe3O4-SiO2 is assigned to the asymmetric
stretching bands of Si-O-Si in the silica shell. Further-
more, the band at 801 cm−1 is assigned to the Si-O-Si
symmetric stretch (Figure 2b). The presence of the
anchored NH2 and CH2 groups, originating from the
amino-propyl moiety of APTES was confirmed by
stretching vibrations at 3300–3370 cm−1 and
2810–2986 cm−1, respectively (Figure 2c). After the modi-
fication with cyanuric chloride (Fe3O4@SiO2-TCT,
Figure 2d), the appearance of new bands at 1511, 1564
and 1711 cm−1 correspond to C=N stretching vibration.
Aryl carbamate and/or aryl sulfamate (1.0 mmol),
arylboronic acid (1.0 mmol), potassium phosphate
(2.0 mmol, 430 mg), Fe3O4@SiO2-EDTA-Ni(0) NPs
(0.018 g, 1 mol %) and ethylene glycol (3.0 ml) were
ꢀ
added into a round-bottomed flask and stirred at 120 C
for 6 hr under the air atmosphere. The reaction process
was monitored by TLC using petroleum ether/ethyl ace-
tate and/or GC. After the completion of the reaction, the
reaction mixture was cooled to room temperature and
the nanocatalyst was separated from the mixture with an
external magnetic field. Then, 10 ml of distilled water
was added and the crude was subsequently extracted
with ethyl acetate (3 × 10 ml). The organic phase was
dried over anhydrous MgSO4 and the crude product was
obtained after removing the ethereal solution by a rotary