Inorganica Chimica Acta
Research paper
Pd-PVP-Fe (palladium-poly(N-vinylpyrrolidone)-iron) catalyzed
S-arylation of thiols with aryl halides in aqueous media
Parvaneh Ghaderi-Shekhi Abadi b, Ezzat Rafiee a,b, Mohammad Joshaghani a,b,
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a Department of Inorganic Chemistry, Faculty of Chemistry, Razi University, Kermanshah 67149, Iran
b Institute of Nano Science and Nano Technology, Razi University, Kermanshah 67149, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 May 2016
Received in revised form 20 June 2016
Accepted 1 July 2016
Available online 2 July 2016
Pd-PVP-Fe (palladium-poly(N-vinylpyrrolidone)-iron) nano catalyst catalyzes selective C–S
cross-coupling (S-arylation) reactions of thiols with aryl halides and avoids the formation of S–S
(disulfide) homocoupling byproducts. The reactions were carried out in aqueous media using only
0.23 mol% palladium with high selectivity and short reaction time. The effects of the Pd0 and Fe0 moieties
on the C–S cross-coupling reaction mechanism, yield, and selectivity were investigated. The yield and
selectivity can be controlled by adjusting the order of adding the reactants and catalyst into the reaction
medium. The X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), electron
backscatter diffraction (EBSD) microscopy, energy dispersive X-ray (EDX) spectroscopy, and thermal
gravimetric analysis (TGA) tools were used to characterize the catalyst. The C–S cross-coupling reaction
process could be repeated up to six times without losing effectiveness. The metals leaching of Pd-PVP-Fe
nanocatalyst after reusing cycles were investigated by atomic absorption spectroscopic (AAS) and EDX
spectroscopy. The nature of Pd metal after the first run of the C–S cross-coupling reaction was studied
by UV–vis spectrophotometry. The morphology of bimetallic nanocatalyst after the first run of the C–S
cross-coupling reaction was investigated by SEM, EBSD, and EDX microscopy.
Keywords:
Palladium
Iron
Selectivity
C–S cross-coupling reactions
Electron backscatter diffraction (EBSD)
microscopy
Ó 2016 Published by Elsevier B.V.
1. Introduction
metal catalyst due to the coordination of organosulfur compounds
[20,21]; (iii) inevitability harsh reaction conditions and/or expen-
Nanomaterials have attracted more attention recently because
they now can be synthesized with great control and they show
distinct chemical structure, size, and shape-dependent properties
[1–5].
The C–S cross-coupling reactions are of great importance in the
manufacture of the sulfur compounds with a broad spectrum of
therapeutic activities such as antidiabetes, anti-inflammatory,
anti-Alzheimer’s, anti-Parkinson’s, anticancer, and anti-HIV [6].
Historically, homogeneous and heterogeneous catalysts including
Pd [7], Pd/Fe [8], Pd/Zn [9], Pd/In [10], Co/Zn/ligand [11], Fe/ligand
sive, toxic, and flammable organic solvents [22–27].
It is reported that bimetallic nanoparticles are capable to stabi-
lize collagen better than individual metal constituents [8,9]. In
addition, efficient bimetallic Pd-base catalysts were introduced
for the cross-coupling reactions [8–10].
Recently, we have employed Pd-PVP-Fe (palladium-poly(N-
vinylpyrrolidone)-iron) nano catalyst in the Mizoroki-Heck
coupling reactions [28]. The Fe0 is a suitable catalyst for catalytic
steps involve the coordination of ligands [12,29–32]. On the other
hand, palladium is
a well-known catalyst in most coupling
[12], Bi/ligand [13], Cu/ligand [14], Pd/C [15], CuI/
L
-proline [16],
reactions involving the oxidative addition reactions [19,33–36].
Therefore, we encouraged to study the C–S cross-coupling reaction
of aryl halides and thiols with an appropriate arrangement of
Pd and Fe particles in the catalyst network, we hoped that the iron
act as an electrophilic buffer to protect the palladium center from
attack of the thiols. In order to avoid pollution, water was used as a
low cost and green solvent with greater chemoselectivity in the
coupling reaction [37–41]. In addition, the separation of the water
insoluble organic products from the aqueous phase could easily be
achieved [42–45].
and FeSO4Á7H2O/phen [17] have been widely used in the C–S
cross-coupling reactions. Along with the appreciated results, there
are some drawbacks include: (i) formation of unwanted S–S homo-
coupling byproduct (Scheme 1) [18–20]; (ii) deactivation of the
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Corresponding author at: Department of Inorganic Chemistry, Faculty of
Chemistry, Razi University, Kermanshah 67149, Iran.
0020-1693/Ó 2016 Published by Elsevier B.V.