Cellulose as an efficient support for Mn(salen)Cl: Application for catalytic oxidation of sulfides to sulfoxides

Article abstract of DOI:10.1039/c4ra06450j

Supported Mn(salen)Cl was prepared by immobilization of a homogeneous Mn(salen)Cl complex onto cellulose and characterized by FT-IR, TGA and atomic absorption spectroscopy. This heterogeneous catalyst is able to effectively catalyze the oxidation of aromatic sulfides in good yield under mild conditions. The catalytic activity of Mn(salen)Cl and [Mn(salen)Cl-cellulose] in this reaction was investigated. The heterogeneous catalyst showed higher catalytic activity with respect to the neat Mn(salen)Cl complex. The key advantages of this process are cost effectiveness of the catalyst, reusability of the catalyst and easy work-up. This journal is

Full text of DOI:10.1039/c4ra06450j

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Cellulose as an efficient support for Mn(salen)Cl:
application for catalytic oxidation of sulfides to
sulfoxides
Cite this: RSC Adv., 2014, 4, 39870
*
Arezou Mohammadinezhad, Mohammad Ali Nasseri and Mehri Salimi
Supported Mn(salen)Cl was prepared by immobilization of a homogeneous Mn(salen)Cl complex onto
cellulose and characterized by FT-IR, TGA and atomic absorption spectroscopy. This heterogeneous
catalyst is able to effectively catalyze the oxidation of aromatic sulfides in good yield under mild
conditions. The catalytic activity of Mn(salen)Cl and [Mn(salen)Cl–cellulose] in this reaction was
investigated. The heterogeneous catalyst showed higher catalytic activity with respect to the neat
Mn(salen)Cl complex. The key advantages of this process are cost effectiveness of the catalyst,
reusability of the catalyst and easy work-up.
Received 30th June 2014
Accepted 22nd August 2014
DOI: 10.1039/c4ra06450j
www.rsc.org/advances
important and fascinating biopolymer and an almost inex-
haustible and renewable raw material.18 It was widely applied as
Introduction
an efficient support and/or template for the synthesis of inor-
ganic materials. For example, palladium nanoparticles were
synthesized on the cellulose matrix and employed as an active
catalyst for the hydrogenation reaction of phenol and the Heck
coupling of styrene and iodobenzene.19 In recent years, cellulose
has gained renewed signicance as a raw material and still
possesses a high potential for future applications.20–22
In this work, we synthesized [Mn(salen)Cl–cellulose] as an
efficient, green and new catalyst for the oxidation of suldes.
Also, we reported comparison of the catalytic activity of homo-
geneous Mn(salen)Cl complex and heterogeneous Mn(salen)Cl
complex in the oxidation reaction. Oxidation reaction carried
out using a variety of oxidants. Among these oxygen donors,
oxone is the best oxidant.23–30
Sulfones are valuable synthetic intermediates for the construc-
tion of chemically and biologically important molecules.1–5
Aromatic sulfones have been shown to be useful in therapy, in
particular as antipsychotic agents.6 A number of drugs closely
related to the sulfonamides (e.g. dapsone) have been used
effectively in the long-term treatment of leprosy.7 Thiosulfo-
nates, on the other hand, are powerful sulfenylating agents,8–11
with antimicrobial and fungicidal activities12,13 and some
industrial uses.14 Application of functionalized carbon nano-
tube-poly(arylene sulfone) composite membranes for direct
methanol fuel cells has been reported.15
The immobilization of catalysts has several important
potential advantages such as recycle and reuse ability, relatively
safe handling, reduced environmental impact upon work-up,
good thermal and chemical stabilities and good dispersion of
the active catalytic site.16 Thus, search for suitable supports in
order to immobilize salen complex is still a tempting challenge
in the eld of heterogeneous catalysis. A number of solid
materials as supports, carbon nanober, graphene, ionic
liquids, mesoporous silica, zeolite, SBA-15, metal oxides and
polymers have broadly been investigated.
Experimental
Materials and methods
All chemicals and solvents were purchased from Merck or Fluka
and were used without purication.
The structure of Mn(salen)Cl–cellulose was obtained by
interpretation of the spectra TGA50 (Shimadzu-Japan) on a
platinum cell, FT-IR 4300 (Shimadzu-Japan) on a range from
400 to 4000 cmꢀ1 and atomic absorption spectroscopy (AA-6300
Shimadzu-Japan).
Many attempts have been focused on the development of
new ligand-derived polymeric supports for the attachment of
metals and the design of new approaches to increase the cata-
lytic activity.17 An important material within this group is
cellulose. Cellulose is the most widely spread organic polymer
found in nature, since it constitutes the main component of the
membrane of plant cell. It is well-known that cellulose is a very
Preparation of catalyst
3-trimethoxysilylpropylamine (10 mmol, 1.76 ml) was added to
a suspension of salicylaldehyde (10 mmol, 1.044 ml) in absolute
ethanol (10 ml) in ambient temperature. The solution instantly
became yellow, indicating the formation of the schiff base. Aer
Department of Chemistry, College of Sciences, University of Birjand, Birjand
97175-615, Iran. E-mail: manaseri@birjand.ac.ir; malinasseri@yahoo.com; Fax:
+98 561 2502065; Tel: +98 561 2502065
39870 | RSC Adv., 2014, 4, 39870–39874
This journal is © The Royal Society of Chemistry 2014

View Article Online
Paper
RSC Advances
30 min, Mn(CH3COO)2$4H2O (5 mmol, 1.225 g) was added to
the solution, and the mixture was further stirred for 2 h to
formation Mn(salen) complex. LiCl (29.15 mmol, 1.224 g) was
then added. Aer adding 3 g cellulose and stirring the mixture
overnight at room temperature, product was isolated by
removing the solvent. The crude product was washed with
water, EtOH and ether, respectively. Further drying of the solid
ꢁ
product was carried out in an oven at 80 C for 8 h.
Fig. 1 Derivative TG (DTG) curve Mn(salen)Cl–cellulose.
General procedure for catalytic oxidation of methyl phenyl
sulde
A mixture of 1 mmol methyl phenyl sulde (MPS) and oxone (1
mmol, 0.614 g) was added to a stirring solution of Mn(salen)Cl–
cellulose (0.3 g) in H2O (3 ml) at room temperature for the
required period of time (30 min). Aer completion of the reac-
tion (TLC), the catalyst was ltered and the mixture was
extracted with diethyl ether (3 ꢂ 5 ml), the organic layer was
washed with brine (5 ml), dried over MgSO4, and concentrated.
Purity determinations of the products were accomplished by
TLC on silica-gel polygram SILG/UV 254 plates.
Fig. 2 shows the FT-IR spectra of the cellulose, Mn(salen)Cl
and supported complexes of Mn. The spectrum of Mn(salen)Cl
shows a band at 1632 cmꢀ1 is due to imine n(C]N) and another
band at 1596 cmꢀ1 attributed to the aromatic ring vibrations
(Fig. 2C). The peak at 646 cmꢀ1 is assigned to the stretching
vibrations of the Mn–O bond of the complex. In addition, the
observed peaks in the region of 1300–1600 cmꢀ1 are due to C–O,
C–N and aromatic ring. In Fig. 2B, cellulose exhibited bands at
Results and discussion
Characterization of catalyst
The synthetic procedure is shown in Scheme 1. Spectroscopic
techniques including FT-IR, TGA and atomic absorption anal-
ysis were used to study the structural of the manganese(III)–
salen complex. A series of calculations on the catalyst were
performed with the Gaussian 98W.
The loading of Mn on cellulose was 0.266 mmol gꢀ1 esti-
mated by AAS. The derivative TG (DTG) curve of Mn(salen)Cl–
cellulose is shown in the Fig. 1. The recorded curve showed two-
step weight loss at temperatures ranging from 30 to 800 ꢁC. The
rst derivative peak is observed at 332.25 ꢁC and its area found
60% of the total. The total weiꢁght loss is aꢁbout 87.709%. The
ꢁ
ꢁ
mass loss from 265 C to 420 C and 440 C to 575 C is the
result of the thermal decomposition of cellulose.31 On the other
hand, the weight loss from 440 ꢁC to 575 ꢁC can also attribute to
the decomposition of schiff base groups. Covalent bands are
responsible for high thermal stability of catalyst and it caused
ꢁ
that the catalyst stable up to 300 C.
Fig. 2 FT-IR spectra of: (A) [Mn(salen)Cl–cellulose] (B) Cellulose and
Scheme 1 Preparation of cellulose supported Mn(III) catalyst.
(C) [Mn(salen)Cl].
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 39870–39874 | 39871

View Article Online
RSC Advances
Paper
3200–3500 cmꢀ1 and 1000–1300 cmꢀ1 that related to OH, C–O
and an anomeric carbon. There were some differences between
the FT-IR spectra of the pure catalyst (Fig. 2C) and supported
catalyst (Fig. 2A). In the spectrum of Mn(salen)Cl–cellulose
(Fig. 2A), the vibration intensity of bonds became very weak.
In the present study, the molecular equilibrium geometry
was computed with the Gaussian 98W soware system. The
results of this study show that the Si–O distance in the
catalyst is about 1.69798 ꢁA and Si–O–C valence angle in this
system is about 120.48961ꢁ. We also calculate the charge
distribution in the present catalyst. Our study shows that the
electron densities at Si and O are 1.43 and ꢀ0.793 respec-
tively. This charge distribution indicates that the Si–O bond
is electrostatic.
Table 1 Effect of solvent on the oxidation of methyl phenyl sulfide
catalyzed by [Mn(salen)Cl–cellulose]a
Entry
Solvent
Sulfone%
Sulfoxide%
Time (min)
1
2
3
4
5
6
7
8
H2O
Toluene
CH3CN
CH3OH
CH3CH2OH
CH3CH2OCOCH3
1,4-Dioxane
DMF
Acetone
DMSO
n-Hexane
Dichloromethane
THF
Chloroform
Solvent free
0
5
10
5
10
24
15
10
20
35
5
98
10
60
80
70
45
0
60
50
53
20
10
65
10
0
30
180
30
30
30
120
180
180
120
60
180
180
120
180
180
9
10
11
12
13
14
15
5
14
15
0
The effect of solvent on the oxidation of methyl phenyl sulde
with oxone catalyzed by Mn (salen)Cl–cellulose
a
Reaction conditions: methyl phenyl sulde (1 mmol), catalyst (0.3 g),
solvent (2 ml), oxone (1 mmol), T ¼ 25 ꢁC.
To nd the optimized conditions, methyl phenyl sulde was
used as a model substrate. The oxidation reactions were carried
out in various solvents at room temperature. According to the
Table 1, H2O is the best solvent with a high yield (entry 1). The
reaction in the methanol, ethanol and other polar solvent
carried out in moderate to good yield that can be attributed to
the polarity of solvents.
Oxidation of sulde with oxone catalyzed by Mn(salen)Cl–
cellulose
Aer optimization of the reaction conditions, we extended
substrates to aromatic suldes (Table 3). We have observed that
the formation of sulfoxide is favored along with sulfone in H2O
media (Table 1, entry 1). We have therefore decided to explore
the possibility of achieving selective oxidation of suldes to
sulfoxide by conducting the reaction in H2O. Our initial
attempts to obtain pure sulfoxide using MPS in oxone (0.5
mmol) as a model substrate were unsuccessful. On the other
hand, sulfoxide could be achieved from MPS, in excellent yield
at room temperature within a reasonably short reaction time by
using 1 mmol oxone. A substrate/oxidant molar ratio of 1 : 1 was
optimized for better yield of MPS into sulfoxide under the
reaction conditions. We have also compared the catalytic
activity of Mn(salen)Cl and Mn(salen)Cl–cellulose in this reac-
tion. As shown in Table 3, the TOF (hꢀ1) for Mn(salen)Cl–
cellulose was higher than a neat complex.
The effect of different oxidants on the oxidation of methyl
phenyl sulde with oxone catalyzed by Mn(salen)Cl–cellulose.
The effect of different oxidants on the catalytic activity of
Mn(salen)Cl–cellulose in the oxidation of methyl phenyl sulde
was studied. We chose different oxidants such as oxone, KIO4,
UHP and H2O2. The results are summarized in Table 2. When
KIO4, UHP and H2O2 were used as the oxygen source in H2O,
Mn(salen)Cl–cellulose, produced low methy phenyl sulfoxide.
Oxone is a strong, cheap and versatile oxidizing agent. The
results showed that in the presence of oxone as a oxygen source
higher yield was obtained.
Comparison of catalytic activity of Mn(salen)Cl and Mn(salen)
Cl–cellulose
In order to show the effect of immobilization on the catalytic
activity of Mn(salen)Cl in the sulde oxidation with oxone, we
Table 2 Effect of different oxidants on the oxidation of methyl phenyl
sulfide catalyzed by [Mn(salen)Cl–cellulose]a
Entry
Oxidant
Yield of sulde (%)
Time (min)
1
2
3
4
5
Oxone
UHP
H2O2
KIO4
None
98
40
40
10
7
30
600
600
600
600
a
Reaction conditions: methyl phenyl sulde (1 mmol), catalyst (0.3 g),
solvent (2 ml), oxone (1 mmol), T ¼ 25 ꢁC.
Fig. 3 Reusability of catalyst in the oxidation reaction. Reaction time ¼
30 min.
39872 | RSC Adv., 2014, 4, 39870–39874
This journal is © The Royal Society of Chemistry 2014

View Article Online
Paper
RSC Advances
Table 3 Oxidation of aromatic sulfides with oxone catalyzed by Mn(salen)Cl and [Mn(salen)Cl–cellulose]a
Yield (%)
TOF(hꢀ1
)
Mn(salen)Cl–
Mn(salen)Cl
Sulfoxide
cellulose
Entry
1
Suldes
Time (min)
30
Sulfone
5
Sulfoxide
98
Sulfone
0
Mn(salen)Cl
10
Mn(salen)Cl–cellulose
40
45
24.5
2
240
3
90
5
1.406
2.812
3
4
240
240
33
42
2
70
76
10
12
1.031
1.312
2.187
2.375
10
5
30
37
5
90
0
9.25
22.5
6
7
30
60
41
49
13
2
80
96
14
0
10.25
6.125
20
12
8
300
36
4
73
6
0.9
1.825
a
Reaction conditions: suldes (1 mmol), oxone (1 mmol), catalyst (0.3 g), H2O (2 ml), T ¼ 25 ꢁC.
repeated all reactions under optimization conditions. The
We have additionally analysed the liquid phase for traces of
results are summarized in Table 3. Our results showed that the Mn by atomic absorption spectroscopy, but failed to nd any
TOF (hꢀ1) (Turn Over Frequency) for the Mn(salen)Cl–cellulose traces of Mn. Further, we have utilised Sheldon's hot ltration
catalyst was higher than the Mn(salen)Cl catalyst. One probable test. The Sheldon test shows that in the case of [Mn(salen)Cl–
explanation is that the ligands of Mn(salen)Cl complex is not cellulose] we observed 6% of leached Mn aer four consecutive
oxidized when complex attach to cellulose, and therefore the times of reaction. The results showed that the catalytic activity
catalytic activity of Mn(salen)Cl does not reduce.
of Mn(salen)Cl–cellulose is appropriate for more than four time
reuse.
Conclusions
Catalyst reusability and stability
It is important to verify the stability of the heterogeneous Mn(salen)Cl complex was successfully immobilized on to
catalyst since metal leaching from catalyst becomes responsible cellulose. Owing to the abilities of support to highly disperse the
for decreasing of the catalytic activity in successive cycles. To active complexes, and to control the local concentrations of the
assess long-term stability and reusability of [Mn(salen)Cl– reactant and product around active sites, the immobilization
cellulose], oxidation of methyl phenyl sulde was chosen as led to an increase in catalytic performance in the oxidation
model reaction, and recycling experiments were carried out reactions. It observed that the catalytic activity of Mn(salen)Cl
with a single sample of the catalyst. Aer each experiment, the complex can be modied by attaching to cellulose through
catalyst was ltered, washed with H2O, dried and reused. Aer covalent bonding. So that, in comparison with the unhybridized
reusing catalyst for four consecutive times, the yield was 92% Mn(salen)Cl, the oxidation of suldes catalyzed by Mn(salen)
(Fig. 3).
Cl–cellulose with oxone showed higher yield. The
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 39870–39874 | 39873

View Article Online
RSC Advances
Paper
heterogeneous catalyst also remarkably alters ratio of sulfoxide/ 16 (a) F. Coccia, L. Tonucci, N. Alessandroc, P. D'Ambrosioc and
sulfone that was attributed to the immobilization mode and
support effect of heterogeneous catalyst. The immobilized
catalyst could be easily recovered.
M. Bressanc, Inorg. Chim. Acta, 2013, 399, 12–18; (b)
E. Ramirez, S. Jansat, K. Philippot, P. Lecante, M. Gomez,
A. M. Masdeu-Bulto and B. Chaudret, J. Organomet. Chem.,
2004, 689, 4601–4610; (c) D. E. De Vos, M. Dams, B. F. Sels
and P. A. Jacobs, Chem. Rev., 2002, 102, 3615–3640.
17 (a) B. Clapham, T. S. Reger and K. D. Janda, Tetrahedron,
2001, 57, 4637–4663; (b) N. E. Leadbeater and M. Marco,
Chem. Rev., 2002, 102, 3217–3274.
Acknowledgements
The authors are thankful to the University of Birjand Research
Council for the support of this work.
18 A. Lejeune and T. Deprez, Cellulose: Structure and Properties,
Derivatives and Industrial Uses, Nova Science Publishers Inc,
New York, USA, 2010.
19 K. Srinivasan, P. Michaud and J. K. Kochi, J. Am. Chem. Soc.,
1986, 108, 2309.
20 R. L. Hammonds, M. S. Harrison, T. C. Cravanas,
W. H. Gazzola, C. P. Stephens and R. S. Benson, Cellulose,
2012, 19, 1923–1932.
21 R. J. Maurer, A. F. Sax and V. Ribitsch, Cellulose, 2012, 20, 25–
42.
Notes and references
1 E. N. Prilezhaeva, Russ. Chem. Rev., 2000, 69, 367–408.
2 Z. Jin, P. C. Vandort and P. L. Fuchs, Phosphorus, Sulfur
Silicon Relat. Elem., 1994, 95, 1–19.
3 S. Patai and Z. Rappoport, Synthesis of Sulfones, Sulfoxides
and Cyclic Suldes, John Wiley, Chichester, 1994.
4 N. S. Simpkins, Sulfones in Organic Synthesis, Pergamon
Press, Oxford, 1993.
5 M. Mikolajczyk, Tetrahedron, 1986, 42, 5459–5495.
6 G. Andrew, F. Ian, L. Andrew, P. Andrew, W. Graham,
G. Vincenzo, European Patent, EP1511727, 2007.
7 G. A. Ellard, P. T. Gammon, H. S. Helmy and R. J. W. Rees,
Nature, 1972, 239, 159–160.
8 T. F. Parsons, J. D. Buckman, D. E. Pearson and L. Field, J.
Org. Chem., 1965, 30, 1923–1926.
9 G. Palumbo, C. Ferreri, C. D'Ambrocio and R. Caputo,
Phosphorus, Sulfur Silicon Relat. Elem., 1984, 19, 235–238.
10 K. Fujiki and E. Y. Yoshida, Synth. Commun., 1999, 29, 3289–
3293.
11 K. Fujiki, S. Akieda, H. Yasuda and Y. Sasaki, Synthesis, 2001,
7, 1035–1042.
12 J. P. Weidner and S. S. Block, J. Med. Chem., 1964, 7, 671–673.
13 S. S. Block and J. P. Weidner, Mech. React. Sulfur Compd,
1967, 2, 235.
22 B. Duchemin, A. Thuault, A. Vicente, B. Rigaud,
C. Fernandez and S. Eve, Cellulose, 2012, 19, 1837–1854.
23 P. Malik and D. Chakraborty, Tetrahedron Lett., 2012, 53,
5652–5655.
24 S. P. Das, J. J. Boruah, H. Chetry and N. S. Islam, Tetrahedron
Lett., 2012, 53, 1163–1168.
25 V. Mirkhani, M. Moghadam, S. Tangestaninejad, I. M. poor-
Baltork and N. Rasouli, Catal. Commun., 2008, 9, 2411–2416.
26 B. R. Travis, M. Sivakumar, G. O. Hollist and B. Borhan, Org.
Lett., 2003, 5, 1031–1034.
27 T. W. Bell, Y. M. Cho, A. Firestone, K. Healy, J. Liu, R. Ludwig
and S. D. Rothenberger, Org. Synth., 1993, 87, 87.
28 M. Uyanik, M. Akakura and K. Ishihara, J. Am. Chem. Soc.,
2009, 131, 251–262.
29 A. P. Thottumkara, M. S. Bowsher and T. K. Vinod, Org. Lett.,
2005, 7, 2933–2936.
14 N. S. Zerov, N. V. Zyk, E. K. Beloglazkina and
A. G. Kutateladze, Sulfur Rep., 1993, 14, 223.
15 S. H. Joo, C. Pak, E. A. Kim, Y. H. Lee, H. Chang, D. Seung,
Y. S. Choi, J. B. Park and T. K. Kim, J. Power Sources, 2008,
180, 63–70.
30 C. Bolm, A. S. Magnus and J. P. Hildebrand, Org. Lett., 2000,
2, 1173–1175.
31 Y. P. Chauhan, R. S. Sapkal, V. S. Sapkal and G. S. Zamre, Int.
J. Chem. Sci., 2009, 7(2), 681–688.
39874 | RSC Adv., 2014, 4, 39870–39874
This journal is © The Royal Society of Chemistry 2014