An isotetramolybdate-supported rhenium carbonyl derivative: Synthesis, characterization, and use as a catalyst for sulfoxidation

Article abstract of DOI:10.1039/c8dt00429c

A novel isotetramolybdate-supported rhenium carbonyl derivative, [(CH₃)₄N]₄[{Re(CO)₃}₄(Mo₄O₁₆)]·H₂O (1), has been successfully synthesized and characterized by single crystal X-ray diffraction crystallography, IR and UV spectroscopy, etc. Results showed that, compound 1 is an efficient catalyst for the oxidation of thioanisole into the corresponding sulfoxide in the presence of hydrogen peroxide with good to excellent conversion (99%) and excellent selectivity (93%). Highly efficient oxygenation of thioanisole can also be achieved with 100% selectivity of sulfone and >99% conversion. Furthermore, optimized conditions were applied to a range of sulfides to obtain the corresponding sulfoxides and sulfones.

Full text of DOI:10.1039/c8dt00429c

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Lu, X. Ma, Y.
Zhang, V. Singh, P. Ma, C. Zhang, J. Niu and J. Wang, Dalton Trans., 2018, DOI: 10.1039/C8DT00429C.
This is an Accepted Manuscript, which has been through the
Volume 45 Number
1 7 January 2016 Pages 1–398
Royal Society of Chemistry peer review process and has been
accepted for publication.
Dalton
Transactions
Accepted Manuscripts are published online shortly after
An international journal of inorganic chemistry
www.rsc.org/dalton
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1477-9226
PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
framework
a Zr-metal–organic
rsc.li/dalton

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021PAlsepaosseePdtyoLtnd.ot adjust margins
Page 1 of 8
Dalton Transactions
View Article Online
DOI: 10.1039/C8DT00429C
Journal Name
ARTICLE
An isotetramolybdate-supported rhenium carbonyl derivative:
synthesis, characterization, and catalysis for sulfoxidation
Received 00th January 20xx,
Accepted 00th January 20xx
Jingkun Lu, Xinyi Ma, Vikram Singh, Yujiao, Zhang, Pengtao Ma, Chao Zhang, Jingyang Niu∗ and
Jingping Wang∗
DOI: 10.1039/x0xx00000x
A novel isotetramolybdate-supported rhenium carbonyl derivative, [(CH3)4N]4[{Re(CO)3}4(Mo4O16)]·H2O (1) has been
successfully synthesized and characterized by single crystal X-ray diffraction crystallography, IR and UV spectroscopy, etc.
Results showed that, compoumd 1 is an efficient catalyst for the oxidation of thioanisole into corresponding sulfoxide in
the presence of hydrogen peroxide with good to excellent conversion (99%) and excellent selectivity (93%). Highly efficient
oxygenation of thioanisole can also be achieved with 100% selectivity of sulfone and >99% conversion. Furthermore, the
optimized conditions were applied to a range of sulfides to obtain the corresponding sulfoxides and sulfones, respectively.
www.rsc.org/
salts. Particularly, the carbonyl manganese/rhenium
derivatives of the POMs, with rich behaviors displayed by the
d6 carbonyl metal compounds and the POMs, are especially
important. From 2008, our group began to study this topic and
successfully synthesized a series of POM-based carbonyl
Introduction
Polyoxometalates (POMs) are nanosized anionic metal‒oxygen
clusters of early transition metals and have stimulated
research in broad fields of science.1 Especially, POM-based
manganese/rhenium
derivatives
(M
(M
such
and
and
as
ReI),5a
ReI),5b
carbonyl metal derivatives, as
a
peculiar class of
[{H2W8O30}{M(CO)3}2]8−
[{H2Mo8O30}{M(CO)3}2]8−
[{PMo3O16}{Re(CO)3}4]5−,5c
=
=
MnI
MnI
organometallic oxides, have received considerable attention
not only because of their unique structural archetypes, but
also due to their potential catalytic properties.2 Immobilization
of metal carbonyl units onto the POMs surface are able to
provide dual advantages of both carbonyl fragment and metal-
oxo anionic scaffold, leading to formation of various number of
diverse functional compounds. Therefore, a great deal of
research deals on their synthetic route, stability aspects, and
their catalytic efficiency have been widely investigated in the
last few years.3 Nevertheless, it is noteworthy to say that most
of the reported POM-based metal carbonyl derivatives are still
dominated by Lindqvist-type POMs.3e,4 POM-based metal
carbonyl derivatives are still challenging from their synthetic
intricacies, primarily as most of the polyoxoanions have not
enough charge density for facile reactivity of metal carbonyl
functional groups, secondary their dissolved incompatibility in
most of the solvents. It is important to mention that some
other factors might disrupt their formation as compared to
other class of organometallic POMs like their radiation or
thermal instability and the expensive prices of carbonyl metal
[(PW11O39){Re(CO)3}3(μ3-O)(μ2-
[{Re(CO)3}4(μ2-OH)(μ3-O)(W5O18)]5−,5e
and
OH)]7−,5d
[P2W15O56Co3(H2O)3(OH)3Mn(CO)3]8−,5f etc.
On the other hand, an increasing amount of attention has
been directed towards the POM-supported rhenium carbonyl
derivatives due to the attractive catalytic properties of both
rhenium atoms and POMs. Sulfoxidation is one of the most
important fundamental reactions in organic synthesis. Many
sulfoxides and sulfones derivatives are widely utilized as
ligands for transition metal asymmetric catalysis,6a−e and as
fine synthetic reagents for the synthesis of new drugs.6f−g
Moreover, sulfoxidation is also the basis for the catalytic
oxidative desulfurisation of crude oil to remove sulfur-based
impurities as the resulting products can be selectively
extracted into a polar solvent under milder conditions than
those traditionally required for industrial catalytic
hydrodesulfurisation.7 Very recently, Song’s group reported
two POM-containing catalysts and discussed their catalytic
efficiencies for the selective oxygenation of sulfides.8 Thus, we
focus on the synthesis of POM-supported rhenium carbonyl
derivatives and expect to discover good efficiency in the
oxidation of sulfides.
a.Henan Key Laboratory of Polyoxometalate Chemistry, Institute of Molecular and
Crystal Engineering, College of Chemistry and Chemical Engineering, Henan
University, Kaifeng, Henan 475004, P. R. China. E-mail: jyniu@henu.edu.cn,
jpwang@henu.edu.cn; Fax: (+86)371-23886876
Herein, we report a first example of isotetramolybdate-
Electronic Supplementary Information (ESI) available: Comments on previous
reported typical organometallic derivatives of POMs (Table S1); structural figure
supported
[(CH3)4N]4[{Re(CO)3}4(Mo4O16)]·H2O (
metal
carbonyl
derivative,
1
), which has the largest
(Fig. S1-S3); IR, UV-vis, XPRD and TGA of
1 (Fig. S4-S8); the ESI-MS spectrum of 1
number of metal carbonyl groups (Table S1). The catalysis of
for the selective sulfoxidation of sulfides with a H2O2 (30%)
1
(Fig. S9-S10); catalytic properties (Tables S5-S6). CCDC 1817070. See
DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021PAlsepaosseePdtyoLtnd.ot adjust margins
Dalton Transactions
Page 2 of 8
ARTICLE
Journal Name
oxidant was studied. Under optimal conditions, thioanisole
was oxidized to the expected methyl phenyl sulfoxide (sulfone)
with 99% (>99%) conversion and 93% (100%) selectivity.
Table 1 Crystal structure data for compound 1
View Article Online
DOI: 10.1039/C8DT00429C
Formula
C28H50N4O29Mo4Re4
Mr (g mol−1)
Crystal system
Space group
a (Å)
2035.28
Tetragonal
I41/acd
16.7770(8)
16.777
Experimental
General methods and materials
b (Å)
c (Å)
39.340(2)
11072.9(12)
8
All chemicals were used as purchased without purification. IR
V (Å3)
spectra were recorded on
a Bruker-Vertex 70 FT-IR
Z
spectrometer using KBr pellets in a range of 4000–450 cm–1.
Elemental analyses (C, H and N) were conducted on a Perkin-
Elmer 2400-II CHNS/O analyzer. UV-vis absorption spectrum
Cryst. size (mm3)
Dc (g cm−3)
μ [mm−1]
0.23 x 0.22 x 0.21
2.442
9.665
was obtained with
a U-4100 spectrometer at room
F (000)
7568
temperature. Thermogravimetry (TG) analysis was carried out
on a Mettler–Toledo TGA/SDTA851e instrument with a heating
rate of 10 °C min–1 heated from 25 to 800 °C under nitrogen. X-
ray powder diffraction (XPRD) patterns were performed on a
Bruker AXS D8 Advance diffractometer instrument with Cu Kα
radiation in the angular range 2θ = 5–40° at 293 K. Inductively
coupled plasma (ICP) spectra were obtained on a Perkin-Elmer
Optima 2000 ICP-OES spectrometer. Electrochemical
measurements were performed with a CHI660 electrochemical
workstation. A conventional three-electrode system was used.
The working electrode was a freshly cleaned glassy carbon disk
electrode, a Pt wire was used as the counter electrode and the
saturated calomel reference electrode (SCE) was used as a
reference electrode. The working electrode was polished with
Al2O3 powders with size down to 0.05 μm. ESI-MS
measurements were performed on an AB SCIEX Triple TOF
4600 spectrometer operating in negative ion mode and data
was analyzed using the Peakview 2.0 software provided. GC
chromatogram was carried out on Bruker 450-GC (flame
ionization detector) instrument equipped with a 30m column
(GsBP-5, 0.25 mm internal diameter and 0.25 um film
thickness) with nitrogen as carrier gas.
Data/restraints/
parameters
Reflns collected
Index ranges
GOF on F2
R1, wR2 [I ≥ 2σ (I)]
R1, wR2 [all data]
2457/29/159
26693
–20 ≤ h ≤ 17, –17 ≤ k ≤ 20, –46 ≤ l ≤ 45
1.037
R1 = 0.0317, wR2 = 0.0770
R1 = 0.0457, wR2 = 0.0858
mmol), and catalyst (11.1 mg, 5.5 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 5 min. The
resulting products were analyzed by GC to determine the
conversion and selectivity with methylbenzene as an internal
standard.
X-ray crystallography
Suitable single crystals of 1 were selected from their respective
mother liquors and airproofed in a glass tube. X-ray diffraction
intensity data were recorded on a Bruker APEX-II CCD
diffractometer with the graphite-monochromated Mo Kα
radiation (λ = 0.71073 Å) at 293 (2) K. Routine Lorentz and
Synthesis of [(CH3)4N]4[{Re(CO)3}4(Mo4O16)]·H2O (1)
polarization corrections were applied, and
a multi-scan
absorption correction was performed using the SADABS
program. Using Olex2,9 the structure was solved with the
SHELXS-1997 structure solution program using Direct Methods
and refined with the SHELXL refinement package using Least
Squares minimisation.10 A combination of elemental analysis
and thermogravimetric analysis confirms the number of water
molecules of crystallization in polyanions. No hydrogen atoms
associated with the water molecules were located from the
difference Fourier map. All H atoms on water molecules were
directly included in the molecular formula. A summary of the
crystal data and structure refinements is listed in Table 1.
Re(CO)5Cl (0.036 g, 0.099 mmol) in 3 mL CH3CN was refluxed in
the dark at 70 °C for 0.5 h, then cooled to room temperature
(denoted as solution A). In a separate beaker, Na2MoO4·2H2O
(0.266 g, 1.099 mmol) and TeO2 (0.0153 g, 0.096 mmol) in 10
mL distilled water were refluxed for 20 min and cooled to
room temperature (denoted as solution B). Subsequently, A
was added dropwise into B, and the resulting solution was
stirred at 80 °C for 1 h. Then additional (CH3)4NCl (0.1 g, 1.0
mmol) was added to the solution while hot, then cooled and
filtrated. The orange filtrate was allowed to stand in the dark
for slow evaporation. Yellow block crystals of
1 were collected
after four days. Yield: ca. 9.82% (based on Re(CO)5Cl). Anal.
calcd (%) for C28H50N4O29Mo4Re4: C, 16.52; H, 2.48; N, 2.75;
Mo, 18.78; Re, 36.60. Found: C, 16.81; H, 2.29; N, 2.88; Mo,
19.60; Re, 35.98. FT-IR (KBr, cm–1): 3442 (s), 3037 (w), 2003
(vs), 1876 (vs), 1625 (m), 1485 (m), 933 (s), 908 (s), 725 (w),
686 (w), 634 (w).
Results and discussion
Synthesis
In the past few years, we have prepared and thoroughly
characterized some POM-based carbonyl metal derivatives by
utilizing negative POM precursors. As part of our continuing
work, we have been attempting to adopt simple inorganic salts
General procedure for the selective oxidation of sulfides
In a typical experiment, sulfides (1 mmol), H2O2 (30 wt.%, 1.2
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Page 3 of 8
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
View Article Online
DOI: 10.1039/C8DT00429C
Scheme 1 The preparation process of 1.
as the starting materials, leading to products with novel
structures and interesting properties. In this context, was
1
synthesized by the reaction of Na2MoO4·2H2O with
tetramethylammonium chloride and Re(CO)5Cl in a mixed
solution (CH3CN : H2O = 3 : 10) at 80 °C. Parallel experiments
Fig. 2 (a) Packing diagram of crystal
and (b) along the c axis. Colour code: Mo (mazarine); Re (pink);
C (black); N (green); H (grey); Non-covalent interactions (cyan).
1
viewed along the b axis
indicate that several factors affect the formation of
1. The
presence of Na2MoO4·2H2O is necessary because compound
1
Single-crystal X-ray diffraction analysis reveals that
crystallizes in the tetragonal system with space group I41/acd.
consists of a discrete [{Re(CO)3}4(Mo4O16)]4−
Compound 1a)
1
could not be obtained by using other simple molybdate salts. It
is worth mentioning that the reaction is particularly sensitive
1
(
to the pH value because no
1 could be isolated outside pH
unit, four [(CH3)4]N+ cations, and one crystal water molecule.
As shown in Fig. 1a, this new polyanion 1a can be described as
grafting the four {Re(CO)3} units onto the {Mo4O4} cubane.
Each {Mo4O16} cubane contains four edge-sharing MoO6
octahedrons. And the bond valence sum (BVS) calculations
show that all Mo atoms are in the +6 oxidation states (Table
S2).12 The POM moiety has eight terminal oxygen atoms and
four μ2-O atoms, providing a large coordination ability for
bonding the Re centers of the rhenium carbonyl clusters, and
forming the stable structure of [{Re(CO)3}4(Mo4O16)]4− (Mo–O:
1.691(8)–2.428(7) Å). The four Re atoms coordinated with
three carbonyl ligands are attached to the {Mo4O16} unit via
four μ3-O atoms (Fig. 1b). In addition, all Re atoms adopt six-
coordinate distorted octahedral geometries (Fig. S1). Each Re
atom is coordinated by three C atoms from the carbonyl
clusters and three O atoms from {Mo4O16} unit. The Re–C bond
lengths in 1a range from 1.853 to 1.859 Å, while the C–O bond
lengths range from 1.168 to 1.179 Å (Table S3). These bond
lengths are consistent with that observed for other Re(I)
carbonyl complexes.3h,13 Moreover, molecular insight revels
supramolecular aggregation via diverse C–H···O and O···O non-
covalent interactions. There are various intermolecular
interactions amongst the oxygen atoms of the carbonyl oxygen
of rhenium carbonyl units (Fig. 2). The methyl hydrogen atoms
of tetramethylammonium cations interact with the oxygen
atoms of polyoxoanions and carbonyl oxygen atoms through
C–H···O interactions (2.50 Å–2.606 Å).
ranging from 6.3 to 7.4, with the pH value 6.5 giving the
highest yield. Another interesting aspect in the molecular
isolation of
1 is the use of TeO2, although no tellurium atom
was observed in the compound. Furthermore, no crystals were
afforded when TeO2 was removed from the reaction. Various
attempts have been made to obtain crystals by changing other
metal oxides, however, all the attempts were fruitless. The
specific role of TeO2 was not well understood, but it is
speculated that TeO2 might play a synergistic action with other
materials in the reaction and the similar phenomena have
been previously reported.11
Structural Descriptions
IR, UV, XPRD and TGA characterizations
IR spectrum between 4000 and 450 cm–1 was used to
investigate the structural characters of compound
1 (Fig. S4).
The terminal Mo–Ot vibrations are seen as prominent bands at
933 and 908 cm–1. The characteristic peaks at 725–634 cm–1
are assigned to Mo–O–Mo bridges vibrations.14 A pair of
Fig. 1 a) Ball-and-stick representation of Re(CO)3 and {Mo4O16}
unit; b) Polyhedral (left) and ball-and-stick (right)
representations of polyanion 1a
.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins