Synthesis and characterization of a Sb(v)-containing polyoxomolybdate serving as a catalyst for sulfoxidation

Article abstract of DOI:10.1039/c8dt01273c

A Sb-containing Anderson-based polyoxomolybdate cluster, [(CH₃)₄N]₄H₈[Na₅Sb₃(Sb₂Mo₁₂O₅₇)]·17H₂O [1; (CH₃)₄N⁺ = TMA⁺], has been successfully synthesized by using an aqueous solution method and structurally characterized. In particular, UV-Vis spectroscopy has been employed to elucidate the stability of the polyoxoanions. Under mild conditions, the catalyst demonstrates high activity and selectivity for the sulfoxidation of various sulfides in the presence of hydrogen peroxide. For example, thioanisole undergoes up to 100% conversion and 100% sulfone selectivity at 25 °C in aqueous solution.

Full text of DOI:10.1039/c8dt01273c

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PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
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a Zr-metal–organic
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Synthesis,
characterization
of
a
Sb(V)-containing
polyoxomolybdate serving as a catalyst for sulfoxidation
Received 00th January 20xx,
Accepted 00th January 20xx
+
+
Jingkun Lu, Yaping Wang, Xinyi Ma, Yanjun Niu, Vikram Singh, Pengtao Ma, Chao Zhang, Jingyang
∗
∗
Niu and Jingping Wang
DOI: 10.1039/x0xx00000x
+
+
3 4 4 8 5 3 2 2 3 4
A Sb-containing Anderson-based polyoxomolybdate cluster, [(CH ) N] H [Na Sb (Sb Mo12O57)]·17H O [1; (CH ) N = TMA ],
www.rsc.org/
has been successfully synthesized by using an aqueous solution method and structurally characterized. In particular, UV-
Vis spectroscopy has been employed to elucidate the stability of polyoxoanion. Under mild conditions, the catalyst
demonstrates high activity and selectivity for the sulfoxidation of various sulfides in the presence of hydrogen peroxide.
For example, thioanisole undergoes up to 100% conversion and 100% sulfone selectivity at 25 °C in aqueous solution.
7
mandatory to implement in daily concerns. It will be a
Introduction
meaningful approach to accomplish green industrial goals if
insoluble organic substrates could be oxidized with hydrogen
Sulfoxidation is one of the basic and important reactions in
organic synthesis. Sulfoxides and sulfones as the oxidation
products are widely utilized as fine synthetic reagents for the
peroxide in water at mild conditions.
As is well known, the polyoxometalates (POMs) possess
interesting electronic properties that implied them as a unique
class of molecules having great potential applications in
diverse areas such as catalysis, medicine, magnetism,
1
synthesis of new drugs, as ligands for transition metal
2
asymmetric catalysis, and as oxotransfer reagents in oxidation
3
processes. Moreover, sulfoxidation is also the basis for the
8
electronics and photochemistry. In addition, one of the most
catalytic oxidative desulfurisation of crude oil to remove
sulfur-based impurities as the resulting sulfones can be
selectively extracted into a polar solvent under milder
conditions than those traditionally required for industrial
interesting aspects of POM chemistry lies with the fact that
they can be viewed as promising hetro- and homogeneous
catalysts because of their reusability, corrosiveness, high
9
4
thermal stability and oxidative redox properties. It is to be
catalytic hydrodesulfurisation. Hereto, a wide variety of
noted that Anderson-based polyoxoanions are considered as
an important class of POMs family, due to its abundant
terminal oxygen atoms with high reactivity since they consist
oxidizing agents have been used in those preparative
processes such as nitric acid, K FeO , oxone, hypervalent
2
4
5
iodine, UHP, solid oxidizing agents, etc. Unfortunately, most
of the systems reported so far often suffer numerous
drawbacks in terms of low yields, poor E-factors, complex
handling procedures and extreme reaction conditions. With
the increasing environmental and economical concerns in
of a single metal atom supported by six-edge sharing MO
6
(M =
For example, an Anderson-supported
N] Mo 24 reported by X. Yang et al
was found to be a highly efficient catalyst in the oxidation
1
0,11
W or Mo) octahedra.
polyoxometalate [(C
4
H
9
)
4
6
7
O
1
1a
reaction of sulfides. A single-sided triol-functionalized iron-
centered Anderson polyoxometalate, [[N(C
[FeMo {(OCH CNH }], can efficiently catalyze the
aerobic oxidation of aldehydes in water for the green
recent years, benign oxidization reaction using H O2 as
2
4 9 4 3
H ) ] -
terminal oxidant would be promising because only water is
6
produced as the sole by-product. Additionally, as part of
6
O18(OH)
3
2
)
3
2
“
green” concept, toxic organic solvents are expected to be
8
a
preparation of carboxylic acids.
replaced by alternative non-toxic media. Water undoubtedly is
a unique solvent thus oxidations of sulfides in aqueous media
rather than in common poisonous organic solvents are highly
On the other hand, Sb-containing polyoxomolybdates
emerging as a unique branch of POMs, have recently become
an area of significant interest on account of their important
1
2
role in oxidation catalysis systems. Till now, antimony-
containing POMs have been extensively studied, however
among them mostly are Sb(III)-containing polyoxotungstates
1
2– 13a
III
(14–2n)–
such as [Sb
3
2
W
22
2+
O
74(OH)
2
]
2+
,
[Sb
2+ 13a
2
W
20
M
2
O
70(H
2
O)
6
]
(M
(α-
+
2+
=
Fe , Co , Mn , Ni , Zn ),
and [Cs
2
2 3
Na(H O)10Pd
III
Sb W
9–
]
13j
9
O
33
)
2
et al. Compared to the numerous Sb(III)-
containing polyoxotungstates, there are very few Sb(V)-
polyoxomolybdates become apparent since the advent of first
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an Axis Ultra X-ray photoelectron spectrometer. GC
chromatogram was carried out on Bruker 450-GC (flame
ionization detector) instrument equipped with a 30m column
Table 1 Summary of Sb-containing POMs
Ref. Formulas
(GsBP-5, 0.25 mm internal diameter and 0.25 um film
III
12–
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
3a [Sb
3a [Sb
3b [Zn
2
2
3
W
W
22
O
74(OH)
2
]
thickness) with nitrogen as carrier gas.
III
(14–2n)–
12–
3+
2+
2+
2+
2+
20
M
2
O
70(H
2
O)
6
]
(M = Fe , Co , Mn , Ni , Zn )
Synthesis of TMA [Na Sb (Sb
O (3.2 g, 16.32 mmol) was dissolved in 9 ml
O and heated to 50 °C (denoted as solution A). In a separate
(0.607 g, 2.08 mmol) was dissolved in 3 mL of
dilute HCl (3.0 M), and then Sb (0.605 g, 1.87 mmol) was
4
H
8
5
3
2 2
Mo12O57)]·17H O (1)
III
(H
2
O)
3
9 33 2
(α-Sb W O ) ]
4 6 7 2
(NH ) Mo O24·4H
III
12–
]
3c [Cu
3
(H
2
O)
3
(α-Sb W
9
O
)
33 2
H
2
III
W
26–
]
3d [Sb
3e [Fe
3f [(Mn(H
3g [Na Sb
Sb
6
65
O
217(H
2
O)
7
2 3
beaker, Sb O
III
6–
]
4
(H
2
O)10(β-Sb W
9
O
33
)
2
2 5
O
III
12–
]
2
O))
3
(Sb W
9
O
)
33 2
added (denoted as solution B). When all the solid materials
had been completely dissolved, B was added dropwise to A.
After cooling to room temperature, TMAOH (2 mL, 1.1 M) was
added to the resulting cyan solution. Subsequently, the pH
value of the mixture was carefully adjusted to 5.44 using NaOH
III
22–
]
2
4
(H
2
O)
4
(Sb W
9
O
)
33 4
III
19–
3h [Ce
3
4
W
2
O
8
(H
2
O)10(Sb W
9
O
33
)
4
]
III
12–
3i [(VO)
3
(α-Sb W
9 33 2
O ) ]
III
9–
3j [Cs
3k [(MnCl)
3l [{Na(H O)
2
Na(H
2
O)10Pd
3
(α-Sb W
9
O
33
)
2
]
(
6.0 M) solution. Then after that, the resulting reaction
mixture was heated to 60 °C and stirred for 30 min followed by
the addition of FeSO solution (2 mL, 0.07 M). Subsequently,
III
12–
6
(Sb W O ) ]
9 33 2
III
9–
2+
2+
2+
2+
2
2
6
}
3
3 4 2 3 9 33 2
{M(C H N )} (Sb W O ) ] (M = Co , Mn , Ni , Zn )
4
V
5–
]
4
[H
2
Sb Mo
III
5a [PSb (H
O
24
the reaction mixture was heated at 60 °C and stirred 30 min
again, and then allowed to cool down at room temperature. A
clear cyan solution was obtained and filtered to stand for
crystallization. Colorless block-shaped crystals were collected
after six weeks. Yield: 0.325g. [49.9 % Based on Mo] Elemental
analysis (%) calcd: C, 5.66; H, 2.67; N, 1.65; Na, 3.38; Sb, 17.92;
4–
]
2
O)Mo11
O
39
V
4
10–
5b [Sb
5c [Sb
6 48
Mo12(OH) O ]
V
4
III
12–
]
Sb
2
Mo18
O
73(H
2
O)
2
V
Sb Mo
5–
Sb(V)-containing polyoxomolybdate [H
2
6
O
24
]
reported
1
4,15
by Sasaki et al in 1982.
of Sb-containing POMs is shown in Table 1.
A comprehensive literature survey Mo 33.88. Found: C, 5.88; H, 2.66; N, 1.52; Na, 3.18; Sb, 18.12;
Mo 34.06. IR (KBr pellet): 3434 (vs), 3040 (vs), 1670(s), 1484(s),
403(s), 951(s), 925(vs), 899(sh), 817(w), 656(s), 476(w).
1
Thus, the Sb(V)-containing
Anderson-based
polyoxomolybdates serving as potential catalysts grab our General procedure for the selective oxidation of sulfides
great attention. As expected, a new Sb-containing Anderson-
2 2
In a typical experiment, sulfides (1 mmol), H O (30 wt.%, 3
supported
[Na Sb (Sb
polyoxomolybdate
cluster,
TMA
4
mmol), and catalyst (5 μmol) were added into a 50 mL round-
bottom tube equipped with a reflux condenser. The reaction
mixture was charged in the tube at the set temperature, and
was stirred vigorously for 1 h. The resulting products were
extracted with ethyl acetate, and analyzed by GC to determine
the conversion and selectivity with n-dodecane as an internal
standard.
H
8
5
3
2
Mo12
O57)]·17H O, has been firstly isolated. As an
2
oxidative catalyst, it could be used to the simple, mild, and
efficient oxidation of sulfides for the first time. Furthermore,
the homogeneous catalyst system can be reused in successive
reactions for eleven times.
X-ray crystallography
Experimental
3
A crystal with dimensions 0.25 × 0.18 × 0.15 mm for
1 was
General methods and materials
selected and stuck on a glass fiber. X-ray diffraction intensity
data were recorded at 296 (2) K on a Bruker Apex-II CCD
diffractometer with the graphite-monochromated Mo Kα
radiation (λ = 0.71073 Å) (Table 2). Routine Lorentz and
polarization corrections were applied, and a multi-scan
absorption correction was performed using the SADABS
All chemical reagents were commercially procured and were
used without further purification. The Infrared spectra (using
KBr in pellets) were recorded on a Bruker VERTEX 70 IR
–1
spectrometer in the range of 4000–450 cm . Elemental
analyses (C, H, and N) were conducted on a PerkinElmer 2400-
II CHNS/O analyzer. Inductively coupled plasma (ICP) analyses
were performed on a Perkin-Elmer Optima 2000 ICP-OES
spectrometer. UV absorption spectra were obtained with a U-
16
17
program. Using Olex2, the structure was solved with the
18
SHELXS-97 structure solution program using Direct Methods
19
and refined with the SHELXL refinement package using Least
4100 spectrometer at room temperature. Thermogravimetry
Squares minimisation. In the final refinement, the Sb, Mo, and
Na atoms were refined anisotropically. No hydrogen atoms
associated with the water molecules were located from the
difference Fourier map. The lattice water molecules were
determined by CHN element analysis and TGA results. All H
atoms on water molecules were directly included in the
molecular formula.
analysis (TGA) was carried out under a nitrogen gas
e
atmosphere on a Mettler–Toledo TGA/SDTA851 instrument
–1
with a heating rate of 10 °C min from 25 to 800 °C. X-ray
powder diffraction (XPRD) measurement was performed on a
Bruker AXS D8 Advance diffractometer instrument with Cu Kα
radiation (λ = 1.54056 Å) in the angular range 2θ = 5–40° at
293 K. X-ray photoelectron spectra (XPS) were recorded with
2
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Table 2 Crystal structure data for compound 1
Formula
−
C
16
H
48Mo12
N
4
Na
5 5
O66Sb
1
r
M (g mol )
3227.56
Crystal system
Space group
a (Å)
orthorhombic
Cmcm
12.2380(8)
23.8258(16)
13.8810(9)
4047.4(5)
2
b (Å)
C (Å)
3
V (Å )
Z
−
3
Dc (g cm
)
2.648
−
1
μ (mm
F (000)
θ range (deg)
)
3.564
3028.0
2
3.742 to 50.194
10401
Fig. 1 (a) Polyanion structure of cluster
ellipsoids at the 50% probability level; (b) The ball-and-stick
polyhedral representation of polyoxoanion; (c) The space
1 with thermal
Reflections collected
Index ranges
-14 ≤ h ≤ 14, -28 ≤ k ≤ 25, -16 ≤ l ≤ 15
/
Data/restraints/
parameters
filling presentation of polyoxoanion. Color code: Sb, cyan;
SbNa, turquoise; Mo, purple, O, red, Na, yellow; SbO , pink;
MoO , blue.
6
1
965/0/146
1.087
6
2
GOF on F
R
1, wR
2
[I>=2σ (I)]
[all data]
R
1
1
= 0.0517, wR = 0.1422
2
R
1, wR
2
R
= 0.0646, wR = 0.1536
2
Results and discussion
Synthesis
As well known, Sb-containing POMs with unique structures
and fascinating properties have been widely reported during
the last decades. However, in contrast to the Sb-containing
polyoxotungstates, their molybdate analogues are much less
explored,
especially
for
the
Sb(V)-containing
polyoxomolybdates. In this paper, an interesting Sb(V)-
containing Anderson-based cluster was synthesized using
Fig. 2 Packing of
1 in the solid state showing the porous
conventional aqueous method by reaction of Sb
2 3 2 5
O , Sb O ,
coordination framework due to connection of the corners of
the cluster anion by antimony/sodium-directed molecular
assembly through oxo and hydroxo bridges. Color code: Sb,
cyan; SbNa, turquoise; Mo, purple, O, red, Na, yellow.
Hydrogen atoms are omitted for clarity.
(
NH Mo O and FeSO . It is noteworthy that relatively
7
4
)
6
O
24·4H
2
4
minor variations in reaction conditions can profoundly
influence the identities of the products. (I) The reaction pH is a
critical determinant in the syntheses of the crystals.
Reasonable yields of crystalline products were obtained in the
pH range of 5.2-5.6. Lower pH resulted in no products, while
higher pH correlated with some amorphous precipitates. (II)
Parallel experiments show that using NaOH solution to adjust
pH value is especially important. Its presence is necessary to
obtain pure bulk samples and no crystals suitable for single-
Structural Descriptions
The molecular structure of compound
single crystal X-ray diffraction. Compound
orthorhombic system with space group Cmcm and consists of
1
has been confirmed by
1
crystallizes in the
+
+
four TMA cations, five Na cations, eight protons, seventeen
water molecules and the polyoxoanion
(Sb 57)] . And all the Sb and Mo atoms were six-
crystal X-ray diffraction could be obtained when NaOH solution lattice
was replaced by LiOH, KOH, or CsOH solution. (III) The [Na Sb
8
–
5
3
2
Mo12O
presence of Sb
is also crucial during the isolation coordinated with octahedral geometry. It is noteworthy that
there are serious crystallographic disorders in polyoxoanion.
2 3 4
of . Notably, although Sb O and FeSO were used as starting
O
3
and FeSO
2
4
1
As shown in Fig. 1, the adjacent Anderson-type {SbMo
in are linked alternatively via disordered Sb/Na and Na ions
into a one-dimension (1D) chain. Interestingly, the adjacent
SbMo } units gave a mirror-symmetry representation as
shown in Fig. S1. Additionally, shows a porous solid-state
6
} units
materials in the system, no Sb(III) and Fe ions were observed in
the compound. Furthermore, no crystals were afforded when
1
3
+
2+
Sb and Fe were removed from the reaction. They may play
a synergistic action with other materials in the reaction and
{
6
1
2
0
the similar phenomena have been previously reported.
framework, since the Anderson-based polyoxoanions further
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Fig. 3 XPS spectra of
1 for (a) Sb 3d3/2 and Sb 3d5/2; (b) Mo
3d3/2 and Sb 3d5/2.
form supramolecular coordination polymeric chains through
the Sb/Na–O-directed molecular assembly in which the
corners of the units are connected through Sb/Na oxo or
hydroxo bridges (Fig. 2). Furthermore, considering the charge
balance of compound 1, eight protons need to be added. The
Fig. 4 a) UV spectra of
stability of
values on the stability of
1
; b) The influence of time on the
bond valence sum calculations of all the oxygen atoms in this
compound indicate that all of these protons are delocalized,
which is common in POM chemistry.
1
in the aqueous solution; Influence of the pH
in aqueous solution: c) The UV
2
1
1
spectral evolution in the acidic direction; d) The UV spectral
evolution in the alkaline direction.
XPS Analyses and XRPD Patterns
The bond valence sum (BVS) calculation of
1 manifests that the
oxidation states of all Sb and Mo atoms are assigned to +5 and
crucial parameters like solvents, concentration and pH value.
To investigate the influence of pH on the stability of the
2
2
+
6, respectively (Table S1). The XPS spectra of
recorded to further consolidate the chemical valences of Sb
and Mo atoms (Fig. 3). The XPS spectrum of for Sb atoms
1 were also
compound in aqueous solution, compound
1 has been
1
elaborately probed by means of UV spectra. In addition, the
pH values in the acidic direction were adjusted using diluted
HCl solution while the pH values in the alkaline direction were
adjusted by using diluted NaOH solution. The initial pH value of
gives two peaks with binding energies (BEs) of 530.6 and 540.1
eV, attributed to Sb 3d5/2 and Sb 3d3/2 of the Sb (V) center (Fig.
3a). The Sb 3d5/2 and Sb 3d3/2 BE values in
1 are consistent with
those [530.5 (Sb 3d5/2) and 540.1 eV (Sb 3d3/2)] observed in the
2
−5
−1
1
in water (5 × 10 mol L ) was 4.6. As is shown in Fig. 4c, the
3
2 5
pure Sb O crystal. Besides, the two apparent signals
absorbance bands at 233 nm and 206 nm are gradually red-
shifted and become weaker and weaker at pH 3.7, which is a
clear indication for the decomposition of the POM skeleton.
appearing at 236.2 and 235.7 eV are ascribed to Mo (VI) ions,
respectively (Fig. 3b). The purity of the phases has been
checked by comparison of the experimental X-ray powder
pattern with the powder pattern calculated from the structure
solved from single-crystal X-ray diffraction data (Fig. S5 in the
ESI†). The differences in intensity between the experimental
and simulated XPRD patterns might be due to the variation in
preferred orientation of the powder sample during collection
of the experimental XPRD.
The reason for the red-shift of the Ot
→Mo band may be due
to the protonation of the terminal oxygen atoms of
24b
polyoxoanions. In contrast, from the aforementioned results,
the UV spectra of
increased to 10.6 (Fig. 4d). The above analyses show that
compound is quite stable in the broad pH range of 3.7–10.6
1 do not change at all even the pH value is
1
in aqueous solution.
FT−IR and TG analyses
The IR spectrum of
region of 450–1000 cm , which is in good agreement with the
result of single-crystal X-ray structural analysis. The IR
UV spectra
The UV spectrum in aqueous solution in the region of 200−400
1
shows the skeletal vibrations in the
nm of
1
reveals two characteristic peaks (Fig. 4a), suggesting
–1
24a
the presence of polyoxoanions. The higher energy band at
2
06 nm is mainly anticipated due to the pπ–dπ charge-transfer spectrum shows the O–H and N–H absorption bands as well as
transition of the O Mo bonds. Whereas, the lower energy typical frequencies for Mo–O bands (Fig. S6). The characteristic
absorption band at round 233 nm, can be attributed to the absorptions of the polyanions below 1000 cm appear at ca.
pπ–dπ charge-transfer transitions of the Ob,c
Mo bonds. In 951(s), 925(vs), 899(sh), 817(w), 656(s), 476(w). The signal
order to investigate the stability of in solution, in situ
t
→
–
1
→
–1
appearing at 951 cm can be ascribed to the characteristic
absorption of v(Mo–O ). The characteristic peaks at 925, 899
and 817 cm are derived from the v(O –Mo–O ) and v(Mo–O )
1
t
spectroscopic measurement was performed in the aqueous
system (Fig. 4b). The unchanged position and strength of the
–
1
b
b
–1
c
2
5
vibrations. And another peak at 656 cm is probably
attributed to the absorptions of Sb–O stretching and bending
vibrations.
absorption bands indicate that the aqueous system of
1 can
stably exist at ambient temperature for at least 16 hours. As it
is a well-known fact that POMs are pH sensitive and their
stability is primarily depended on a particular reaction media,
thus their studies are mainly specific and restricted on several
26
To investigate the thermal stability of 1, thermogravimetric
analysis (TGA) was performed under a nitrogen flow as shown
4
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in Fig. S7. The thermal decomposition process of
1 is defined in Table 3 Effect of reaction parameters on model reaction of the sulfoxidation
a
two steps. The first step corresponds to a weight loss of 9.34 % catalyzed by 1
from 25 to 200 °C is mainly attributed to seventeen lattice
water molecules (calcd 9.01 %). Subsequently, the rest of the
observed weight loss (42.08 %) in the range of 200–900 °C,
.
mainly due to the removal of eight protons (in the form of
+
constitutional water moleculars), four TMA cations and the
c
Catalyst
(mol%)
—
Con.
(%)
8.3
100
92
Sel.(3a)
(%)
b
Entry
Solvent
2 2
H O
partial sublimation of MoO
3
.
1
2
3
4
5
6
7
8
9
H
2
O
13.2
100
99
Catalytic Oxidation
0.5
H
2
O
Optimization of the catalyst
0.5
CH
3
CN
Based on literature investigation, Mo based catalysts are active
7a,b
0.5
MeOH
3
85
>99
>99
>99
73
2
and selective in sulfoxidation of thioethers.
Moreover,
0.5
acetone
65
Mo–Sb oxides catalysts can also show high activities with good
stabilities in sulfoxidation of two different thioethers, reported
0.5
CH
2
Cl
O
O
O
O
O
O
O
O
O
2
28
0.25
1.0
H
2
97
2
7c,d
H
2
100
38
>99
97
by Pârvulescu et al. In view of this, the catalytic
performance of catalyst was evaluated in the oxidation of
2 2
various sulfides by H O under homogeneous conditions at
0.5
H
2
1
2
4
5
1
1
1
1
0
1
2
0.5
H
2
88
98
0.5
H
2
100
100
100
100
94
100
100
100
100
98
25°C. The effects of several reaction parameters on the
0.5
H
2
oxidation reaction were studied in detail. To begin with,
thioanisole, 1a was chosen as a model substrate for catalytic
sulfoxidation reactions (Table 3). It is observed that the
d
1
3
4
0.5
H
2
e
f
1
0.5
H
2
3
1
5
0.5
H
2
reaction is almost not feasible in the absence of the catalyst
Table 3, entry 1). For the sake of comparison, we also
envisaged antimony trioxide, antimony pentoxide and
NH Mo
oxidation of thioanisoles and found them to be less active
catalysts compared to
(Table S3). As seen in Fig. S8, the POM Investigation of the solvents effect on 1a by using catalyst
compounds will convert to the active polyoxoperoxo species in showed that conversions of 92%, 85%, 65%, 28% in
the presence of H
and then sulfur-containing substrates acetonitrile, methanol, acetone and dichloromethane,
1
a
Reaction conditions: substrate (1 mmol), catalyst 1, solvent (2 mL), 1 h, 25
(
b
c
°
C. Unless otherwise noted.
2 2
H O /substrate ratio. Determined by GC
d
e
f
analyses based on initial substrate. 35 °C. 45 °C. Conversion and selectivity
7 2
O24·4H O independently as a catalyst for the of the 11th cycle in the recycling studies.
(
4
)
6
1
1
2
O
2
were oxidized to the corresponding sulfoxides and sulfones. respectively, could be obtained (entries 3–6). The conversion
Next, we considered it imperative to examine the performance of 1a reached 85% in a high protic solvent i.e using methanol
of the catalyst in a variety of solvents other than water, since (entry 4). It was found that acetone, an aprotic solvent, proved
solvents have been known to have immense influence on the to be inefficient corresponding to its 65% conversion (entry 5).
activity and selectivity of catalyst in the sulfoxidation reaction.
Additionally, the use of a less-polar solvent toluene afforded
the phenyl methyl sulfone in the lowest conversion (entry 6).
Surprisingly, strong proton donating solvent, water, not only
exhibited its inherently greener characteristics compared to
common organic solvents but also showed excellent
conversion and selectivity. Henceforth, the oxidation of 1a was
performed in water after much experimentation on optimizing
solvent. In addition, the effect of catalyst dosage is also very
important in the reaction optimization process because the
concentration of the catalytically active species increased with
2
8
higher catalyst dosage. Fig. 5a illustrates the kinetic profile of
the oxidation of thioanisole with different catalyst dosages
under otherwise identical conditions. Noting that conversion
of 1a gradually increases as the catalyst dosage is increased
from 0.25 mol% to 1 mol% (entries 2, 7–8). In addition, the
reaction time for a complete conversion can be shortened to
3
0 minutes with 1 mol% catalyst amount (Fig. 5a). Catalyst
with 0.25 mol% loading led to a low selectivity of 73% of
corresponding sulfone (entry 7) (Fig. 5b). However, catalyst
1
1
Fig. 5 (a, b, c, d) Effect of catalyst amounts on the reaction of exhibited a higher selectivity of 3a with increasing the catalyst
thioanisole (data were obtained by carrying out parallel amount (Fig. 5c, d). Therefore, the optimized catalyst dosage
experiments under the same experimental conditions).
was proved to be 0.5 mol%, at which moderate conversion and
excellent selectivity were achieved (entry 2).
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run, the reaction converted 100% of 3a in 1 h. Then the
product was extracted with ethyl acetate and the catalyst
existing in the aqueous medium was used for next catalytic
run. The results (Fig. S11 in the ESI†) showed that the catalyst
could be reused at least eleven times with a general decline
a
2 2
Table 4 Oxidation of various sulfides in water using H O catalyzed by 1.
Time
Conv. b
(%)
Sel.
(%)
Product
Entry
Substrate
(h)
(entry 15).
Sulfoxidation with different substrates
1
2
3
4
5
6
7
8
9
c
1
100
100
100
100
99
100
100
100
99
Having established the optimized reaction conditions for
selective sulfoxidation of the model substrate, we extended
the study to a range of structurally diverse sulfides and the
results of which are summarised in Table 4. Under the
optimized reaction conditions, both aryl and alkyl sulfides
could be oxidized to the corresponding sulfones using 1 mmol
0.8
3
of the substrate, 3 mmol of H
C in H O. Ethyl methyl sulfide (entry 2) exhibited the highest
activity among the sulfides surveyed. When dipropyl sulfides
were used as substrates, the catalyst exhibited excellent
catalytic performance on prolonged reaction time of 3 hours
entry 3). Furthermore, the dibutyl sulfide was efficiently
2 2
O and 5 μmol of catalyst at 25
°
2
3
1
(
converted to the corresponding sulfone with 100% conversion
and 99% selectivity over a further 3 h (entry 4). It is worth
noting that some aryl sulfides could also be converted into the
corresponding sulfones in high conversions and selectivities
3
99
4
97
96
(entries 5–7). On the other hand, the steric hindrance effect of
aryl−aryl thioethers appears to be the main factor affecꢀng the
yield of oxygenated products. On increasing the reaction
temperature to 50 °C, phenyl sulfide (entry 8) was confirmed
as a less-reactive substrate, with 98% over a further 10 h. The
reaction system resulted in a dibenzothiophene (entry 9) of
39% conversion and 85% selectivity. In the case of 4,6-
dimethyldibenzothiophene (entry 10), significantly sluggish
reactivity was detected after 10 hours. We could say that the
present catalytic system could be applied to catalyze a wide
range of sulfides.
4
95
97
10
10
98
95
39
85
Conclusions
1
0
trace
−
−
In summary, a Sb-containing polyoxomolybdate cluster has
been synthesized and characterized. Selective oxidation of
a
Reaction conditions: sulfides (1 mmol), catalyst (0.5 mol%), H
2
O (3 mL), 25 °C.
various sulfides to the corresponding sulfones by using
homogeneous catalyst was demonstrated in the presence of
under mild conditions with excellent conversions and
1 as a
b
Unless otherwise noted. Determined by GC analyses based on initial substrate.
c
5
0 °C.
2 2
H O
selectivity. Additionally, this homogeneous catalytic system
not only catalyzed the oxidation of thioanisole with 100%
conversion and 100% selectivity, but also could be reused in
successive reactions with retention of the catalytic
performance. Our further research will be focus on exploring
the synthesis of novel structural analogues and their
interesting catalytic properties.
2 2
As shown in Fig. S9, when the H O / substrate (O/S) molar
ratio was varied from 1:1 to 2:1 to 3:1 to 4:1 to 5:1, the degree
of conversion ranged from 38%–88% to 100%–100%–100%,
respectively (entries 2, 9–12). Based on these results, the O/S
molar ratio of 3:1 was used for the following studies.
Moreover, we have screened different temperatures for the
oxidation of thioanisole. The conversions of 1a at three
different temperatures (25 °C, 35 °C and 40 °C) are a function
of time (entries 2, 13–14). Obviously, there is an increase on
the reaction rate with rising temperature (Fig. S10). However,
Conflicts of interest
from the view point of saving energy, we choose 25 °C for There are no conflicts to declare.
further investigation of the oxidation reaction of thioanisole.
To confirm the recyclability of the homogeneous system, entry
worked as an example in the successive reactions. In the first Acknowledgements
2
6
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Plea sDe a dl t oo nn oT tr aa nd sj ua cs tt i om nasrgins
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ARTICLE
We are grateful to the National Science Foundation of China (), 13 (a) M. Bösing, I. Loose, H. Pohlmann and B. Krebs, Chem. –
Eur. J., 1997,
Savelieff, N. A. Al Kadi and M. Sadakane, Inorg. Chem., 2001,
, 4742; (c) M. Bösing, A. Nöh, I. Loose and B. Krebs, J. Am.
Chem. Soc., 1998, 120, 7252; (d) U. Kortz, M. G. Savelieff, B.
S. Bassil and M. H. Dickman, Angew. Chem. Int. Ed., 2001, 40
384; (e) U. Kortz, M. G. Savelieff, B. S. Bassil, B. Keita and L.
Nadjo, Inorg. Chem., 2002, 41, 783; (f) D. Volkmer, B.
Bredenkötter, J. Tellenbröker, P. Kögerler, D. G. Kurth, P.
Lehmann, H. Schnablegger, D. Schwahn, M. Piepenbrink and
B. Krebs, J. Am. Chem. Soc., 2002, 124, 10489; (g) M.
Piepenbrink, E. M. Limanski and B. Krebs, Z. Für Anorg. Allg.
Chem., 2002, 628, 1187; (h) G. Xue, J. Vaissermann and P.
Gouzerh, J. Clust. Sci., 2002, 13, 409; (i) Drewes D., Limanski
E. M., Piepenbrink M. and Krebs B., Z. Für Anorg. Allg. Chem.,
3, 1232; (b) U. Kortz, N. K. Al-Kassem, M. G.
the Foundation of Education Department of Henan Province ().
4
0
Notes and references
,
3
1
(a) J. Legros, J. Dehli and C. Bolm, Adv. Synth. Catal., 2005,
47, 19; (b) J. M. Shin, Y. M. Cho and G. Sachs, J. Am. Chem.
Soc., 2004, 126, 7800; (c) R. Bentley, Chem. Soc. Rev., 2005,
, 609.
3
34
2
(a) L. Du, P. Cao, J. Xing, Y. Lou, L. Jiang, L. Li and J. Liao,
Angew. Chem., Int. Ed., 2013, 125, 4301; (b) W.-Y. Qi, T.-S.
Zhu and M.-H. Xu, Org. Lett., 2011, 13, 3410; (c) S.-S. Jin, H.
Wang and M.-H. Xu, Chem. Commun., 2011, 47, 7230; (d) J.
Chen, J. Chen, F. Lang, X. Zhang, L. Cun, J. Zhu, J. Deng and J.
Liao, J. Am. Chem. Soc., 2010, 132, 4552; (e) Q.-A. Chen, X.
Dong, M.-W. Chen, D.-S. Wang, Y.-G. Zhou and Y.-X. Li, Org.
Lett., 2010, 12, 1928.
2
003, 630, 58; (j) L.-H. Bi, M. Reicke, U. Kortz, B. Keita, L.
Nadjo and R. J. Clark, Inorg. Chem., 2004, 43, 3915; (k) T.
Yamase, K. Fukaya, H. Nojiri and Y. Ohshima, Inorg. Chem.,
2
006, 45, 7698; (l) R.-R. Cui, H.-L. Wang, X.-Y. Yang, S.-H. Ren,
H.-M. Hu, F. Fu, J.-W. Wang and G.-L. Xue, Chin. J. Chem.,
007, 25, 176.
3
4
A. M. Khenkin and R. Neumann, J. Am. Chem. Soc., 2002,
124, 4198.
(a) C. Li, Z. Jiang, J. Gao, Y. Yang, S. Wang, F. Tian, F. Sun, X.
2
1
1
4 Sasaki, Y. & Ogawa, A. Some Recent DeVelopments in the
Chemistry of Chromium, Molybdenum and Tungsten,
Dilworth, J. R., Lappert, M. F., Eds. Royal Society of Chemistry,
Sun, P. Ying and C. Han, Chem. - Eur. J., 2004, 10, 2277; (b) J.
Palomeque, J. Clacens and F. Figueras, J. Catal., 2002, 211,
1
03; (c) V. Hulea, F. Fajula and J. Bousquet, J. Catal., 2001,
98, 179; (d) Y. Ding, W. Zhu, H. Li, W. Jiang, M. Zhang, Y.
Duan and Y. Chang, Green Chem., 2011, 13, 1210.
5
9 (London 1982).
1
5 (a) A. M. Khenkin, L. J. W. Shimon and R. Neumann, Eur. J.
Inorg. Chem., 2001, 2001, 789; (b) D. Drewes, G. Vollmer and
B. Krebs, Z. Für Anorg. Allg. Chem., 2004, 630, 2573; (c) G.
Xue, X. Liu, H. Xu, H. Hu, F. Fu and J. Wang, Inorg. Chem.,
5
(a) P. S. Tam, J. R. Kittrell and J. W. Eldridge, Ind. Eng. Chem.
Res., 1990, 29, 321; (b) S. Liu, B. Wang, B. Cui and L. Sun, Fuel,
2
008, 87, 422; (c) B. Yu, A.-H. Liu, L.-N. He, B. Li, Z.-F. Diao
2
008, 47, 2011.
and Y.-N. Li, Green Chem., 2012, 14, 957; (d) J. N. Moorthy, K.
Senapati and K. N. Parida, J. Org. Chem., 2010, 75, 8416; (e) R.
S. Varma and K. P. Naicker, Org. Lett., 1999, 1, 189; (f) P. De
1
6 G. M. Sheldrick, SADABS Bruker AXS area detector scaling
and absorption, version 2008/2001, University of Göttingen,
Germany, 2008.
7 O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard
and H. Puschmann, J. Appl. Crystallogr., 2009, 42, 339.
8 G. M. Sheldrick, Acta Crystallogr., Sect. A: Fundam.
Crystallogr., 2008, 64, 112.
9 G. M. Sheldrick, Acta Crystallogr., Sect. C: Cryst. Struct.
Commun., 2015, 71, 3.
0 (a) P. Ma, G. Chen, G. Wang and J. Wang, Russ. J. Coord.
Chem., 2011, 37, 772; (b) L. Li, Y. Niu, K. Dong, P. Ma, C.
Zhang, J. Niu and J. Wang, RSC Adv., 2017, 7, 28696.
Filippis and M. Scarsella, Ind. Eng. Chem. Res., 2008, 47, 973.
S. Barroso, P. Adão, F. Madeira, M. T. Duarte, J. C. Pessoa
and A. M. Martins, Inorg. Chem., 2010, 49, 7452.
W. Zhao, C. Yang, Z. Cheng and Z. Zhang, Green Chem., 2016,
18, 995.
(a) H. Yu, S. Ru, G. Dai, Y. Zhai, H. Lin, S. Han and Y. Wei,
Angew. Chem., Int. Ed., 2017, 129, 3925; (b) Y.-Q. Jiao, H.-Y.
Zang, X.-L. Wang, E.-L. Zhou, B.-Q. Song, C.-G. Wang, K.-Z.
Shao and Z.-M. Su, Chem. Commun., 2015, 51, 11313; (c) H.
1
1
1
2
6
7
8
Gao, A. Virya and K. Lian, J. Mater. Chem. A, 2015,
(
3, 21511;
d) S. Omwoma, W. Chen, R. Tsunashima and Y.-F. Song,
2
1 (a) P. Mialane, A. Dolbecq, L. Lisnard, A. Mallard, J. Marrot
and F. S´echeresse, Angew. Chem., Int. Ed., 2002, 41, 2398;
Coord. Chem. Rev., 2014, 258, 58; (e) S.-S. Wang and G.-Y.
Yang, Chem. Rev., 2015, 115, 4893; (f) L. Cronin and A.
Müller, Chem. Soc. Rev., 2012, 41, 7333; (g) H. N. Miras, J.
Yan, D.-L. Long and L. Cronin, Chem. Soc. Rev., 2012, 41, 7403;
(h) A. Proust, B. Matt, R. Villanneau, G. Guillemot, P. Gouzerh
and G. Izzet, Chem. Soc. Rev., 2012, 41, 7605.
(
b) H.-Y. An, E.-B. Wang, D.-R. Xiao, Y.-G. Li, Z.-M. Su and L.
Xu, Angew. Chem., Int. Ed., 2006, 45, 904; (c) E. M. Villa, C. A.
Ohlin, E. Balogh, T. M. Anderson, M. D. Nyman and W. H.
Casey, Angew. Chem., Int. Ed., 2008, 47, 4844.
2 I. D. Brown and D. Altermatt, Acta Crystallogr., Sect. B:
Struct. Sci., 1985, 41, 244.
3 T. Ji, M. Tang, L. Guo, X. Qi, Q. Yang and H. Xu, Solid State
Commun., 2005, 133, 765.
4 (a) S. Li, J. Zhao, P. Ma, J. Du, J. Niu and J. Wang, Inorg. Chem.,
2009, 48, 9819; (b) S. Li, Y. yuan Guo, D. Zhang, P. Ma, X. Qiu,
J. Wang and J. Niu, Dalton Trans., 2012, 41, 5235.
5 (a) X. Sun, Z. Liang, P. Ma, R. Ban, M. Jiang, D. Zhang, J. Wang
and J. Niu, Dalton Trans., 2015, 44, 17544; (b) J. Wang, Y.
Liang, P. Ma, D. Zhang, J. Niu and J. Wang, CrystEngComm,
2
2
2
9
1
(a) B. Zhang, M.-D. Zhou, M. Cokoja, J. Mink, S.-L. Zang and F.
E. Kuhn, RSC Adv., 2012, 2, 8416; (b) W. Zhu, H. Li, X. Jiang, Y.
Yan, J. Lu and J. Xia, Energy Fuels, 2007, 21, 2514; (c) W. Zhu,
W. Huang, H. Li, M. Zhang, W. Jiang, G. Chen and C. Han, Fuel
Process. Technol., 2011, 92, 1842; (d) T. Li, W. Zhang, W.
Chen, H. N. Miras and Y.-F. Song, ChemCatChem, 2018, 10
88; (e) L. Hong, P. Win, X. Zhang, W. Chen, H. N. Miras and
Y.-F. Song, Chem.–Eur. J., 2016, 22, 11232.
0 (a) M. A. Rezvani, M. A. Nia Asli, M. Oveisi, R. Babaei, K.
Qasemi and S. Khandan, RSC Adv., 2016, , 53069; (b) C.
Yvon, A. Macdonell, S. Buchwald, A. J. Surman, N. Follet, J.
Alex, D.-L. Long and L. Cronin, Chem Sci, 2013, , 3810.
1 (a) H. Lü, C. Deng, W. Ren and X. Yang, Fuel Process. Technol.,
014, 119, 87; (b) C. Yang, Q. Jin, H. Zhang, J. Liao, J. Zhu, B.
Yu and J. Deng, Green Chem., 2009, 11, 1401.
2 (a) H. Tsuji and Y. Koyasu, J. Am. Chem. Soc., 2002, 124
608; (b) J. S. Paul, R. Janssens, J. F. M. Denayer, G. V. Baron
and P. A. Jacobs, J. Comb. Chem., 2005, , 407; (c) H. Tsuji, K.
Oshima and Y. Koyasu, Chem. Mater., 2003, 15, 2112.
,
2
2
2
1
2
017, 19, 207.
6
6 (a) S. J. Gilliam, J. O. Jensen, A. Banerjee, D. Zeroka, S. J.
Kirkby and C. N. Merrow, Spectrochim. Acta. A. Mol. Biomol.
Spectrosc., 2004, 60, 425; (b) G. Xue, X. Liu, H. Xu, H. Hu, F.
Fu and J. Wang, Inorg. Chem., 2008, 47, 2011.
7 (a) W. Zhu, H. Li, X. Jiang, Y. Yan, J. Lu, L. He and J. Xia, Green
Chem., 2008, 10, 641; (b) X. Zhang, Y. Shi and G. Liu, Catal.
4
1
1
2
,
Sci. Technol., 2016,
Câmpeanu, F. Bertinchamps, E.M. Gaigneaux and V.I.
Pârvulescu, Catal. Commun., 2003, , 5; (d) F. Bertinchamps,
6, 1016–1024; (c) D.C. Radu, V.
5
7
4
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V. Cimpeanu, E. M. Gaigneaux and V. I. Pârvulescu, Appl.
Catal. Gen., 2007, 325, 283.
Journal Name
2
8 (a) X. Jiang, H. Li, W. Zhu, L. He, H. Shu and J. Lu, Fuel, 2009,
88, 431; (b) W. Zhu, H. Li, X. Jiang, Y. Yan, J. Lu, L. He and J.
Xia, Green Chem., 2008, 10, 641.
8
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