Self-assembled NiO-ZrO2 nanocrystals with mesoscopic void space: An efficient and green catalyst for C-S cross-coupling reaction in water

Article abstract of DOI:10.1039/c2dt30343d

New NiO-ZrO₂ nanocrystals (MNZ-1) with mesoscopic self-assembly have been synthesized by using a non-ionic surfactant as the structure directing agent (SDA) via evaporation induced self-assembly (EISA) method. Powder X-ray diffraction (PXRD), N

Full text of DOI:10.1039/c2dt30343d

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Self-assembled NiO–ZrO2 nanocrystals with mesoscopic void space:
An efficient and green catalyst for C–S cross-coupling reaction in water†
Nabanita Pal and Asim Bhaumik*
Received 15th February 2012, Accepted 12th April 2012
DOI: 10.1039/c2dt30343d
New NiO–ZrO2 nanocrystals (MNZ-1) with mesoscopic self-assembly have been synthesized by using a
non-ionic surfactant as the structure directing agent (SDA) via evaporation induced self-assembly (EISA)
method. Powder X-ray diffraction (PXRD), N2 sorption study and transmission electron microscopic
(TEM) image analyses revealed the cubic structure, mesoporosity and mesoscopic self-assembly of ca.
7.0 nm sized tiny nanocrystals in the material. MNZ-1 catalyzes the aerobic aryl–sulfur cross-coupling
reactions for a series of aryl-iodides with 4-chlorothiophenol in environment friendly water medium at
elevated as well as room temperature. Pure ZrO2 mesoporous nanocrystals are inactive, whereas pure NiO
nanocrystals showed much lower catalytic activity under similar reaction conditions. The MNZ-1
nanocatalyst is completely non-air sensitive, inexpensive and effective for the synthesis of a series of
essential biomolecules derived from diaryl sulfides.
It is pertinent to mention that since the oxide based nanocrys-
tals self-assemble to form mesoporous material in the presence
Introduction
In recent decades, self-aggregation of nanoparticles to form
nanostructures of different dimensions has drawn wide-scale
attention among researchers of various disciplines.1 Weak non-
covalent intermolecular forces like van der Waals forces,2 hydro-
gen bonding interaction,3 host–guest interaction4 etc. are
responsible for the formation of self-assembled nanostructures.
Their advanced applications in a number of pioneering research
areas like optics, microelectronics, nanodevices, magnetism,
catalysis and biological science are explored.5 Moreover, due to
their large surface to volume ratio some exceptional properties
like quantum effect, macroscopic quantum tunnel effect etc.
are observed in those self-assembled nanoparticles (having par-
ticle size below 10 nm), which are absent in their corresponding
bulk materials.6 There are numerous chemical methods like
hydrothermal,7 evaporation induced self-assembly (EISA),8
microwave assisted heating,9 microemulsion etc. which are
known for the fabrication of various nanoparticles of metal,
metal oxides, metal sulfides, selenides and chalcogenides etc.
with uniform size.10 But comparatively less attention has been
paid to the self-assembled mixed oxide nanoparticles11 having
sizes less than 10 nm and specially their use in eco-friendly cata-
lytic reactions. Organized superstructures of the mixed oxide
nanoparticles may play a key role in the field of catalysis
technology.
of block copolymer surfactants, the removal of the template mol-
ecules from the solid composite materials could generate meso-
scopic void spaces. Thus, the porosity and surface area generated
through this process can play a very crucial role in the gas
storage, ion-adsorption, ion-exchange, biomolecule separation,
catalysis, drug delivery etc.12 To date reports on the self-aggre-
gated oxide nanoparticles into crystalline mesoporous framework
are limited to TiO2,5e CeO2,13 ZrO2,14 SnO2,15 SrTiO3,16
WZrO2,17 etc. Gawande et al. has recently reported the synthesis
of MgO–ZrO2 nanoparticles through ultra-dilution method,
which produces a tetragonal zirconia phase.18 Hence, the syn-
thesis of mixed metal oxide nanoparticles containing cubic ZrO2
as an integral part of the superstructure and their self-assembly is
very challenging and highly desirable.
Diaryl sulfides formed via C–S cross-coupling reaction
from aryl halides bearing different nucleophilic phenyl rings
have significant roles in biological, pharmaceutical, and
material research.19 Transition metals like Fe, Ni, Pd, Cu, Co
based salts mediated C–S coupling reactions in various organic
solvents and an inert atmosphere offer a homogeneous media for
those catalytic reactions. But these reactions suffer from the dis-
advantage of catalyst separation, environmental hazards, etc.20
Moreover, formation of diaryl disulfides as a byproduct due to
additional S–S bond formation decreases the yield of the desired
product as well as makes the reaction more difficult. Very
recently we have developed Cu-grafted functionalized mesopor-
ous catalyst, which can be successfully employed for a series of
facile C–S cross-coupling reactions in different polar organic sol-
vents.21 Ranu et al. has reported a microwave-assisted Cu nano-
particle catalyzed aryl–sulfur coupling reaction in less than
Department of Materials Science, Indian Association for the Cultivation
of Science, Jadavpur, Kolkata–700 032, India.
E-mail: msab@iacs.res.in
†Electronic supplementary information (ESI) available. See DOI:
10.1039/c2dt30343d
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Scheme 1 General scheme for C–S cross coupling reaction.
10 min.22 But the reaction was conducted at relatively higher
General procedure for aryl–sulfur coupling reaction over cubic
MNZ-1 nanoparticles
temperature and in organic solvent DMF. Different Ni complexes
applied for this coupling reaction by various research groups,
showed better activity in hazardous organic solvents and homo-
geneous medium.23 To the best of our knowledge, there is no
report on the aryl–sulfur coupling reactions using heterogeneous
Ni based nanocatalyst and in completely non-polluting water as
reaction medium.
In this report, we describe the synthesis of self-assembled
NiO–ZrO2 nanoparticles having cubic structure via an EISA
method using a non-ionic Pluronic F127 template and citric acid
(CA). CA helps the ordered assembling of the nanoparticles to
form mesoscale structures by minimizing the hydrolysis and con-
densation rate of the metal precursors.24 The highly crystalline
stable nanomaterials thus formed showed good catalytic activity
in the coupling of iodoaryl compounds with thiol compounds at
moderately elevated temperature in aqueous media containing
mild base, K2CO3 (Scheme 1). The aerobic synthesis on this
mixed oxide nanoparticles and easy catalytic reactions reported
herein is completely green and thus environment friendly.
A mixture of iodoaryl compound (Sigma-Aldrich, 1.0 mmol)
and 4-chlorothiophenol (Sigma-Aldrich, 1.2 mmol) in 3 mL of
water was taken in a round-bottomed flask, K2CO3 (E-Merck,
280 mg, 2.0 mmol) and 50 mg catalyst were added in the
mixture. The mixture was then heated at 353 K in a temperature
controlled oil bath fitted with a water condenser and the progress
of the reaction was monitored by TLC. After completion of the
reaction, the reaction mixture was allowed to cool and the cata-
lyst was separated by simple filtration. The catalyst was then
washed and the filtrate was extracted with Et2O. The combined
organic layer was repeatedly washed with water followed by
10% aqueous NaOH and brine solution. Then the organic layer
was dried over anhydrous Na2SO4 (E-Merck) and evaporated to
dryness to give the crude product diphenylsulfide derivatives as
a solid product. The product was further dissolved in n-hexane
and purely crystalline product was separated from that mixture.
1
The isolated crude product was characterized by H, 13C NMR
and FT IR analysis, respectively. The general scheme for aryl–
sulfur cross coupling reaction over MNZ nanoparticles is shown
in Scheme 1.
Experimental section
Synthesis of MNZ-1 nanoparticles
Characterizations
We have prepared the mixed oxide nanomaterial MNZ-1 using
non-ionic block copolymer Pluronic F127 (Mav = 12 600,
EO106PO70EO106, Sigma-Aldrich) as structure directing agent
(SDA), 35 wt% hydrochloric acid (HCl, E-Merck) to maintain
the acidity of the medium, citric acid (CA, Loba Chemie),
nickel(II) nitrate Ni(NO3)2 (Loba Chemie) as the source of nickel
and zirconium(IV) butoxide [Zr(OC4H9)4, Sigma-Aldrich] as the
source of zirconium. In a typical synthesis of this self-assembled
nanoparticle, 1.65 g HCl was added and stirred well in 20 mL
absolute ethanol. Then, 1 g Pluronic F127 template was added to
the acidic solution and allowed to stir for 10–15 min until dissol-
ution. This is followed by the addition of 0.63 g of CA with
vigorous stirring for about 1.5 to 2 h at room temperature (RT).
Then, 2.95 g (10 mmol) Ni(NO3)2 was added to the mixture and
after dissolution 3.85 g (10 mmol) Zr(OC4H9)4 was put drop-
wise in the green solution. The resulting mixture was kept on
stirring covering with PE film for overnight and finally aged
without stirring at RT for solvent evaporation during 2 to 3 days
(depending on the concentrations) to get solid green powder.
Calcination was carried out at 773 K for 5–6 h in the presence of
air to obtain a deep green template free mesoporous NiO–ZrO2
(named MNZ-1).
The small and wide angle powder X-ray diffraction (XRD) pat-
terns of the MNZ-1 material were recorded on a Bruker AXS
D-8 Advance diffractometer operated at 40 kV voltage and
40 mA current and calibrated with a standard silicon sample,
using Ni-filtered Cu Kα (λ = 0.15406 nm) radiation. Nitrogen
adsorption–desorption isotherms were achieved using
a
Beckman Coulter SA 3100 surface area analyzer at a temperature
of 77 K. Prior to this analysis the sample was degassed at 423 K.
For recording TEM (transmission electron microscopy) and HR
TEM (high resolution transmission electron microscopy) images
a JEOL JEM 2010 transmission electron microscope was used.
JEOL JEM 6700F field emission scanning electron microscope
(FE SEM) with an energy dispersive X-ray spectroscopic (EDS)
attachment was used to analyze the morphology of the sample
and its surface chemical composition. UV-visible diffuse reflec-
tance spectrum was recorded using a Shimadzu UV 2401PC
spectrophotometer with an integrating sphere attachment and
1
using BaSO4 pellet as background standard. H and 13C NMR
experiments were carried out on a Bruker DPX-300 NMR spec-
trometer. Fourier transform infrared (FT IR) spectrum was
recorded on KBr pellets by using a Nicolet MAGNA-FT IR 750
spectrometer Series-II. The Ni content in the sample was
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N2 sorption study
measured using Shimadzu AA-6300 atomic absorption spectro-
photometer (AAS) using the aqueous solution of the sample
digested in a minimum quantity of HF/HNO3.
Nitrogen adsorption–desorption isotherms of the self-assembled
NiO–ZrO2 is shown in Fig. 3. Brunauer–Emmett–Teller (BET)
surface area, average pore diameter, and pore volume of the
material estimated from sorption study are exhibited in Table 1.
The sorption isotherms are of type IV pattern, characteristic of
typical mesoporous materials.27 The prominent desorption hys-
teresis at higher P/P0 indicates capillary condensation within the
Results and discussions
Powder XRD analysis
The small powder X-ray diffraction pattern of the calcined
MNZ-1 sample is shown in Fig. 1. One relatively stronger peak
near 2θ = 0.75° indicates the distribution maximum of the dis-
tance of two nearest particle centers. The peak corresponds to
the inter-nanoparticle separation i.e. the distance of particle
center to particle center of ca. 12.61 nm (Table 1). The wide
angle XRD pattern of the highly crystalline MNZ-1 sample
depicted in Fig. 2b exhibits well-resolved highly intense peaks
characteristics of the cubic phase of ZrO2 nanoparticles along
with highly aligned cubic phase of NiO. Peaks at 2θ = 30.3°,
35.14°, 50.48° and 60.2° reveal the presence of (111), (200),
(220) and (311) planes, respectively of cubic ZrO2 according to
JCPDS CAS number 27-0997; with a lattice parameter of
0.509 nm.25 On the other hand, diffraction peaks at 2θ = 37.28°,
43.28°, 62.9° and 75.44° as well as their relative intensities cor-
respond well with the (111), (200), (220) and (311) crystal
planes of face-centered cubic NiO (JCPDS No. 04-0835),
respectively with a lattice parameter 0.418 nm.26 The diffraction
peaks of MNZ-1 sample has been compared with the powder
XRD patterns of pure NiO and ZrO2. There is no impurity of
any other phases of both the oxides. Presence of this type of
mixed phase for multimetal oxide nanoparticles is particularly
important in catalytic reactions.18
Fig. 2 Wide angle XRD pattern of (a) pure NiO, (b) MNZ-1, (c)
MNZ-1 used (after the catalytic reaction) and (d) pure ZrO2 samples.
Fig. 3 N2
adsorption
(●)–desorption
(◯)
isotherms
of
MNZ-1 measured at 77 K. The corresponding pore size distribution is
shown in the inset.
Fig. 1 Small angle XRD pattern of the MNZ-1 sample.
Table 1 Physicochemical data of the mesoporous material MNZ-1
Ni : Zr
synthesis gel
Ni : Zr product
(EDS)
d spacing from
XRD (nm)
BET surface area
Pore volume
Pore width
(nm)
Average particle
size (nm)
Ni percentage
(AAS)
(m2 g−1
)
(cc g−1
)
1 : 1
1.15 : 1
12.61
77.00
0.15
6.90
5.71
9.13
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large mesopores.28 Pore size distribution plot shown in the
inset of Fig. 3 obtained by applying the NLDFT (non-local
density functional theory) method29 gives a sharp peak with
an average pore width value of 6.9 nm, which could be
attributed to the interparticle mesoporosity. Thus the average
Fig. 5 Particle size distribution plot of MNZ-1 obtained from TEM image.
Fig. 6 FE SEM image of MNZ-1 nanoparticles.
Fig. 4 A: TEM image of aggregated MNZ-1 nanoparticles. B: HR
TEM image of the sample with FFT pattern in inset. C: SAED pattern of
MNZ-1.
Fig. 7 UV-visible diffuse reflectance spectrum of the mesoporous
mixed oxide MNZ-1.
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Table 2 C–S coupling reaction over MNZ-1 sample
Entry
1
Aryl Iodide
Thiol
Product
Yield (%)
62.0
2
3
89.0
68.0
4a
39.0
5
—
—
6b
—
—
7c
15.6
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Table 2 (Contd.)
Entry
Aryl Iodide
Thiol
Product
Yield (%)
36.4
8d
Reaction conditions: aryl iodide = 1 mmol, thio compound = 1.2 mmol, solvent: water = 3 ml, K2CO3 = 2 mmol, catalyst = 0.05 g, time =
24 h.a Reaction was carried out at room temperature for 36 h. b Reaction was carried out in the absence of any catalyst. c NiO material alone (in
absence of ZrO2 support) was used as catalyst. d Reaction was carried out with 1 : 1 (wt) mixture of pure NiO and ZrO2.
in the ZrO2 lattice is quite low,30 this strong surface interaction
could stabilize the cubic ZrO2 phase in the MNZ-1 nanocrystal.
Selected area electron diffraction pattern (SAED) of the sample
depicted in Fig. 4C shows a number of diffraction rings of
several planes, which resemble well the d-spacings of the cubic
nickel and zirconium oxide phases as obtained from PXRD. The
particle distribution plot obtained from the TEM analysis shows
a maximum ca. 7.00 nm signifying that the average size of most
of the particles is 7.0 nm (Fig. 5). The textural property investi-
gated by the FE SEM image (Fig. 6) indicates that small spheri-
cal particles are aggregated throughout the specimen. The
uniform spherical texture of the nanocrystals and their self-
assembly is similar to that observed in TEM analysis. The EDS
analysis data (Table 1) reveals the atomic percentage ratio of Ni
and Zr in the calcined product is 1.15 : 1, which is similar to the
molar ratio of those in the synthetic gel.
Fig. 8 FT IR spectrum of the isolated C–S coupling product (Table 2,
entry 2).
UV-visible spectroscopic study
The UV-visible diffuse reflectance spectrum of NiO–ZrO2 mixed
oxide nanoparticles is shown in Fig. 7. Strong absorbance
maxima near 218 nm could be attributed to the oxygen to metal
particle size obtained by subtracting this pore width value from
charge transfer transition of octahedral Zr(IV) in ZrO2.31 Whereas
the value of inter-nanoparticle separation (from PXRD) is
no peak for d–d transition is seen there since Zr(IV) has elec-
ca. 5.71 nm.
tronic configuration d0. On the contrary, the UV band near
247 nm could be assigned to the O → Ni2+ charge transfer tran-
sition in the NiO phase. In addition to that the presence of d–d
Electron microscopic analyses
transition bands of octahedrally coordinated Ni(II) are evident
from peaks near 415, 643 and 718 nm.32 Thus the UV-visible
The transmission electron microscopy (TEM) image of the
aggregated nanoparticle is displayed in Fig. 4A. From this image
it is evident that the average particle size of MNZ-1 is ca.
5–8 nm with an interparticle porosity (low electron density
spots) of ca. 5–6 nm. Thus the size of the particle resembles
well with the data obtained from the N2 sorption study. The
nanocrystalline feature of the pore walls of the tiny self-
assembled MNZ-1 nanoparticles is clear from the representative
HR TEM image of the sample shown in Fig. 4B. The well-
resolved crystal lattice fringes agree well with the d spacing
value of both NiO and ZrO2 oxides. The FFT pattern in the inset
confirms the cubic nature of the highly crystalline mixed oxide.
Further, this HR TEM image (Fig. 4B) suggested intergrowth of
the nanocrystals with very strong surface interactions between
nickel oxide and zirconia. Although, the solubility of Ni2+ ions
diffuse reflectance spectrum of MNZ-1 suggested the presence
of ZrO2 and NiO phases.
Catalytic activity of MNZ-1 in C–S coupling reaction
Here, we have explored the catalytic efficiency of the NiO–ZrO2
mixed oxide nanoparticles in C–S cross-coupling reactions of
different iodoaryl substrates with the thio compound 4-chloro-
thiophenol in green solvent water using K2CO3 as a mild base.
Different diarylsulfides obtained with moderately high yield
ranging from 62% to 89% are summarized in Table 2.33 Almost
no product formation was observed in case of strongly deacti-
vated aromatic substrate containing –NO2 substituent. It is
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Scheme 2
benzene ring i.e. the formation of coupled product increases with
the increasing electron donating ability of the substituent in the
iodobenzene ring. The FT IR spectrum of the isolated crude
product (of entry 2) shown in Fig. 8 reveals that there is no
stretching vibration band for the S–S bond near 500–540 cm−1
,
which indicates very little possibility of diaryl disulfide for-
mation. Moreover, the absence of the stretching frequency of the
S–H bond near 2550–2600 cm−1 proves the splitting of this
bond together with the formation of a C–S bond. The reaction
was carried out both at room temperature (Table 2, entry 4) as
well as at elevated temperature. Although, the yield is lower at
low temperature and requires more time for the completion of
the reaction. At higher temperature improved yields of the pro-
ducts are obtained. The reaction could not proceed in the
absence of catalyst (Table 2, entry 6), which proves the catalytic
role of MNZ-1 in this reaction. Pure ZrO2 nanocrystals were also
found to be completely inactive, whereas pure NiO nanoparticles
(BET surface area of 24 m2 g−1 and devoid of mesoscopic void
space, synthesized under similar conditions in the absence of
ZrO2) showed a very poor cross-coupling product (Table 2, entry
7). This result suggests that the surface area and the mesoporo-
sity of our MNZ-1 plays a crucial role in this catalytic reaction.
To understand the active species involved in this reaction, we
have also used a physical mixture of pure NiO and ZrO2 in 1 : 1
Fig. 9 FT IR spectra of A: 4-chlorothiophenol and B: MNZ-1 catalyst
isolated during the reaction.
further evident that under similar reaction conditions the product
yield is higher in case of those iodobenzenes containing electron
donating groups (OCH3/CH3), which have a more activated
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proportion as catalyst. This physical mixture is also quite less
efficient in this C–S coupling reaction (Table 2, entry 8, 36.4%
yield). Synergic effects between both species could be respon-
sible for little increase in product yield vis-à-vis NiO alone.
Since, the reaction proceeds in aqueous medium and under
aerobic conditions over our self-assembled mixed oxide nano-
catalyst, the method described herein provides a green protocol
towards the synthesis of diaryl sulfides.
green catalyst developed herein is highly stable and provides a
convenient route, which could play an imperative role in the syn-
thesis of numerous target sulfur containing compounds in
organic synthesis.
Acknowledgements
AB wishes to thank Department of Science and Technology
(DST), New Delhi for financial support. NP is thankful to
Council of Scientific and Industrial Research (CSIR), New Delhi
for the senior research fellowship.
A probable reaction mechanism for the C–S coupling reaction
has been suggested in Scheme 2.34 We have taken FT IR spectra
of the catalyst during the catalytic reactions. As soon as the cata-
lyst is added to the reaction medium a red colored complex has
been formed between 4-chlorothiophenol and the Ni atom of the
catalyst (I) which is proved from the disappearance of the
stretching frequency of the S–H bond of the 4-chlorothiophenol
in the thio-Ni complex near 2550–2600 cm−1 (Fig. 9).35 The red
complex does not react with iodobenzene in the absence of base
B here K2CO3. Thus K2CO3 plays a pivotal role in this reaction
and it is proposed that a six membered ring (II) forms during
oxidative addition of iodo compound to the catalyst–thiol
complex. The other oxide ZrO2 helps to increase the effective
surface area of the catalyst bed and stabilize the active tiny NiO
nanocrystals at its surface so that the reaction can proceed more
efficiently. Further, inactivity of pure ZrO2 in this reaction
suggests the complex formation of thiol only occurs at the Ni-
sites and not on Zr-sites. Electron donating substituent facilitates
the coordination of the metal to π-bond of the aromatic ring pro-
viding higher conversion. Finally intermediate (II) on reductive
elimination via species (III) gives the desired product with regen-
eration of the catalyst during the catalytic reaction process.
References
1 (a) A. M. Kalsin, M. Paszewski, S. K. Smoukov, K. J. M. Bishop and
B. A. Grzybowski, Science, 2006, 312, 420; (b) J. Zhang, S. Ohara,
M. Umetsu, T. Naka, Y. Hatakeyama and T. Adschiri, Adv. Mater., 2007,
19, 203; (c) Y. X. Zhang and H. C. Zeng, J. Phys. Chem. C, 2007, 111,
6970.
2 R. P. Andres, J. D. Biefield, J. I. Henderson, D. B. Janes,
V. R. Kolagunta, C. P. Kubiak, W. J. Mahoney and R. G. Osifchin,
Science, 1996, 273, 1690.
3 A. K. Boal, F. Ilhan, J. E. DeRouchey, T. Thurn-Albrecht, T. P. Russell
and V. M. Rotello, Nature, 2000, 404, 746.
4 J. Liu, S. Mendoza, E. Roman, M. J. Lynn, R. Xu and A. E. Kaifer,
J. Am. Chem. Soc., 1999, 121, 4304.
5 (a) A. N. Shipway, E. Katz and I. Willner, ChemPhysChem, 2000, 1, 18;
(b) M. Zhou, S. Chen and S. Zhao, J. Phys. Chem. B, 2006, 110, 4510;
(c) H.-B. Xia, J. Yi, P.-S. Foo and B. Liu, Chem. Mater., 2007, 19, 4087;
(d) O. Taratula, A. M. Chen, J. Zhang, J. Chaudry, L. Nagahara,
I. Banerjee and H. He, J. Phys. Chem. C, 2007, 111, 7666; (e) S. K. Das,
M. K. Bhunia and A. Bhaumik, Dalton Trans., 2010, 39, 4382.
6 P. V. Kamat, J. Phys. Chem. C, 2007, 111, 2834.
7 (a) S. Ajaikumar and A. Pandurangan, Appl. Catal., A, 2009, 357, 184;
(b) H. Chen, J. Gu, J. Shi, Z. Liu, J. Gao, M. Ruan and D. Yan, Adv.
Mater., 2005, 17, 2010.
8 F. Bosc, A. Ayral, P.-A. Albouy, L. Datas and C. Guizard, Chem. Mater.,
2004, 16, 2208.
Recovery and recycling of the catalyst
9 V. Polshettiwar and R. S. Varma, Green Chem., 2010, 12, 743–754.
10 (a) H. Cölfen and M. Antonietti, Angew. Chem., Int. Ed., 2005, 44, 5576;
(b) F. Raimondi, G. G. Scherer, R. Kötz and A. Woraun, Angew. Chem.,
Int. Ed., 2005, 44, 2190.
11 (a) M. Zhang, G. Sheng, J. Fu, T. An, X. Wang and X. Hu, Mater. Lett.,
2005, 59, 3641; (b) G. K. Pradhan and K. M. Parida, Int. J. Eng. Sci.
Technol., 2010, 2, 53.
12 (a) A. Bibby and L. Mercier, Green Chem., 2003, 5, 15;
(b) H. Yoshitake, T. Yokoi and T. Tatsumi, Chem. Mater., 2003, 15, 1713;
(c) M. Fujiwara, S. Terashima, Y. Endo, K. Shiokawa and H. Ohue,
Chem. Commun., 2006, 4635; (d) G. Sun, Y. Chang, S. Li, Q. Li, R. Xu,
J. Gu and E. Wang, Dalton Trans., 2009, 4481; (e) S. L. Jain, B. S. Rana,
B. Singh, A. K. Sinha, A. Bhaumik, M. Nandi and B. Sain, Green
Chem., 2010, 12, 374.
After completion of the reaction between 4-iodoanisole and 4-
chlorothiophenol in the presence of MNZ-1, the solid catalyst
has been filtered off the reaction mixture, washed with water and
acetone. Finally it was dried and activated by heating at 673 K in
air. The catalyst was then ready for further use for another C–S
coupling reaction. Yield of the diaryl sulfide decreased margin-
ally from 89.0 to 87.2% in the second cycle. The wide angle
powder XRD data of this sample (Fig. 2c) shows the same
pattern as that of the fresh sample. After reusing, the Ni content
of MNZ-1 was discovered from AAS analysis. It is observed that
8.5% Ni is present compared to 9.1% as observed before the cat-
alytic reaction. Minor loss in Ni-content is within the range of
experimental error.
13 J.-Y. Chane-Ching, F. Cobo, D. Aubert, H. G. Harvey, M. Airiau and
A. Corma, Chem.–Eur. J., 2005, 11, 979.
14 H. Chen, J. Gu, J. Shi, Z. Liu, J. Gao, M. Ruan and D. Yan, Adv. Mater.,
2005, 17, 2010.
15 J. Ba, J. Polleux, M. Antonietti and M. Niederberger, Adv. Mater., 2005,
17, 2509.
16 D. Grosso, C. Boissíere, B. Smarsly, T. Brezesinski, N. Pinna,
P. A. Albouy, H. Amenitsch, M. Antonietti and C. Sanchez, Nat. Mater.,
2004, 3, 787.
17 M. S. Wong, E. S. Jeng and J. Y. Ying, Nano Lett., 2001, 1, 637.
18 M. B. Gawande, P. S. Branco, K. Parghi, J. J. Shrikhande, R. K. Pandey,
C. A. A. Ghumman, N. Bundaleski, O. M. N. D. Teodorod and
R. V. Jayaram, Catal. Sci. Technol., 2011, 1, 1653.
19 (a) D. N. Jones, in Comprehensive Organic Chemistry, ed. D. H. Barton
and D. W. Ollis, Pergamon, New York, 1979, vol. 3; (b) H. J. Cristau,
B. Chabaud, A. Chene and H. Christol, Synthesis, 1981, 892;
(c) W. Y. Wu, J. C. Wang and F. Y. Tsai, Green Chem., 2009, 11, 326;
(d) S. Ranjit, Z. Y. Duan, P. F. Zhang and X. G. Liu, Org. Lett., 2010, 12,
4134; (e) S. W. Cheng, M. C. Tseng, K. H. Lii, C. R. Lee and
Conclusions
Self-assembled NiO–ZrO2 nanocatalyst has been synthesized via
evaporation induced self-assembly method, which shows meso-
scopic assembly of ca. 7 nm size nanoparticles. The calcined
material is highly crystalline with a cubic crystal structure. This
nanocatalyst exhibits good catalytic activity in the C–S cross-
coupling reaction in aqueous medium under aerobic conditions
using commercially available base K2CO3, together with ease of
product isolation and recovery. Various diaryl sulfides are
formed over this NiO–ZrO2 nanocatalyst in excellent yields. The
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S. G. Shyu, Chem. Commun., 2011, 47, 5599; (f) S. Mallick, S. Rana
and K. M. Parida, Dalton Trans., 2011, 40, 9169; (g) I. P. Beletskaya and
V. P. Ananikov, Chem. Rev., 2011, 111, 1596.
Soc., 2006, 128, 5304; (c) A. Modak, J. Mondal, M. Sasidharan and
A. Bhaumik, Green Chem., 2011, 13, 1317–1341.
28 P. Yang, D. Zhao, D. L. Margolese, B. F. Chmelka and G. D. Stucky,
Nature, 1998, 396, 152.
29 P. I. Ravikovitch and A. V. Neimark, Langmuir, 2002, 18, 1550.
30 G. Stefanic, M. Didovic and S. Music, J. Mol. Struct., 2007, 834–836,
435.
20 (a) J. Hassan, M. Sevignon, C. Gozzi, E. Schulz and M. Lemaire, Chem.
Rev., 2002, 102, 1359; (b) C. Mispelaere-Canivet, J.-F. Spindler, S. Perrio
and P. Beslin, Tetrahedron, 2005, 61, 5253; (c) Y.-C. Wong, T. T. Jayanth
and C.-H. Cheng, Org. Lett., 2006, 8, 5613; (d) L. Rout, T. K. Sen and
T. Punniyamurthy, Angew. Chem., Int. Ed., 2007, 37, 2046.
21 J. Mondal, A. Modak, A. Dutta and A. Bhaumik, Dalton Trans., 2011,
40, 5228.
22 B. C. Ranu, A. Saha and R. Jana, Adv. Synth. Catal., 2007, 349, 2690.
23 (a) J. Langer, R. Fischer, H. Görls and D. Walther, J. Organomet. Chem.,
2004, 689, 2952; (b) M. J. Iglesias, A. Prieto and M. C. Nicasioa, Adv.
Synth. Catal., 2010, 352, 1949.
24 Q. Yuan, A.-X. Yin, C. Luo, L.-D. Sun, Y.-W. Zhang, W.-T. Duan,
H.-C. Liu and C.-H. Yan, J. Am. Chem. Soc., 2008, 130, 3465.
25 S. K. Das, M. K. Bhunia, A. K. Sinha and A. Bhaumik, J. Phys. Chem.
C, 2009, 113, 8918.
26 H. Qiao, Z. Wei, H. Yang, L. Zhu and X. Yan, J. Nanomater., 2009,
795928–795925.
31 G. Katz, J. Am. Ceram. Soc., 1971, 54, 531.
32 D. Srinivas, C. V. V. Satyanarayana, H. S. Potdar and P. Ratnasamy, Appl.
Catal., A, 2003, 246, 323.
33 1H and 13C NMR chemical shifts for different diaryl sulfides reported
1
in Table 2 (for spectra see ESI†). Entry 1: H NMR (300 MHz, CDCl3)
δ = 6.96–7.01 (1H, t), 7.15–7.30 (7H, m), 7.57–7.60 (1H, d). 13C NMR
(300 MHz, CDCl3) δ = 127.5, 129.5, 130.3, 133.7, 135.2. Entry 2: 1H
NMR (300 MHz, CDCl3) δ = 3.62 (3H, s), 6.53–6.54 (2H, d), 7.12–7.13
(2H, d), 7.25–7.26 (2H, d), 7.40–7.42 (2H, d). 13C NMR (300 MHz,
CDCl3) δ = 55.3, 116.4, 129.3, 133.6, 135.2, 138.2, 159.4. Entry 3:
1H NMR (300 MHz, CDCl3) δ = 2.30 (3H, s), 6.91–6.93 (2H, d),
7.26–7.30 (2H, d), 7.40–7.43 (2H, d), 7.55–7.57 (2H, d). 13C NMR
(300 MHz, CDCl3) δ = 21.2, 129.7, 131.3, 133.7, 135.2, 137.3, 137.5.
34 S. Bhadra, B. Sreedhar and B. C. Ranu, Adv. Synth. Catal., 2009, 351,
2369.
27 (a) C. T. Kresge, M. E. Leonowicz, W. J. Roth, J. C. Vartuli and
J. S. Beck, Nature, 1992, 359, 710; (b) H. Peng, J. Tang, L. Yang,
J. Pang, H. S. Ashbaugh, C. J. Brinker, Z. Yang and Y. Lu, J. Am. Chem.
35 D. W. Scott and J. P. McCullough, J. Am. Chem. Soc., 1958, 80, 3554.
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