Oxyfunctionalization of Alkanes Based on a Tricobalt(II)-Substituted Dawson-Type Rhenium Carbonyl Derivative as Catalyst

Article abstract of DOI:10.1021/acs.inorgchem.0c00111

POM-supported metal carbonyl derivatives (PMCDs) represent a family of tremendous potential catalysts owing to their peculiar physical and chemical properties. Yet low-valence transition metal-substituted Dawson-type PMCD catalysts are uncommon. Hence, we synthesized a tricobalt-substituted PMCDs by conventional aqueous solution method, [Na(H2O)5](NH4)7[P2W15O56Co3(H2O)3(OH)3Re(CO)3]·13H2O (1), and characterized by single crystal X-ray diffraction crystallography, IR, and thermogravimetric analyses (TGA), etc. The obtained compound 1 was employed as a catalyst for the oxidation of diphenylmethane (DPM) to benzophenone, giving 96.8percent yield in the presence of tert-butyl hydroperoxide (TBHP) and pyridine. The control experiments indicate that Co metal ion plays an important role in the catalytic reactions. As a side note, the electrospray ionization mass spectrometry (ESI-MS) and UV spectroscopy showed that 1 can retain its integrity in solution, and magnetic measurements indicated that 1 exhibited a weaker ferromagnetic interaction at low temperature.

Full text of DOI:10.1021/acs.inorgchem.0c00111

pubs.acs.org/IC
Article
Oxyfunctionalization of Alkanes Based on a Tricobalt(II)-Substituted
Dawson-Type Rhenium Carbonyl Derivative as Catalyst
Xinyi Ma, Ping Wang, Zhihao Liu, Changhui Xin, Siyu Wang, Jiage Jia, Pengtao Ma, Jingyang Niu,*
and Jingping Wang*
Cite This: https://dx.doi.org/10.1021/acs.inorgchem.0c00111
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: POM-supported metal carbonyl derivatives (PMCDs)
represent a family of tremendous potential catalysts owing to their
peculiar physical and chemical properties. Yet low-valence transition
metal-substituted Dawson-type PMCD catalysts are uncommon.
Hence, we synthesized a tricobalt-substituted PMCDs by conventional
aqueous solution method, [Na(H2O)5](NH4)7[P2W15O56Co3-
(H2O)3(OH)3Re(CO)3]·13H2O (1), and characterized by single
crystal X-ray diffraction crystallography, IR, and thermogravimetric
analyses (TGA), etc. The obtained compound 1 was employed as a
catalyst for the oxidation of diphenylmethane (DPM) to benzophe-
none, giving 96.8% yield in the presence of tert-butyl hydroperoxide
(TBHP) and pyridine. The control experiments indicate that Co metal
ion plays an important role in the catalytic reactions. As a side note, the
electrospray ionization mass spectrometry (ESI-MS) and UV spectroscopy showed that 1 can retain its integrity in solution, and
magnetic measurements indicated that 1 exhibited a weaker ferromagnetic interaction at low temperature.
derivatives (PMCDs), [{Re(CO)3}P2W15Nb3O62]8− and [{Ir-
INTRODUCTION
■
(CO)3}P2W15Nb3O62]8−.19 Inspired by these ideas, our group
Polyoxometalates (POMs), as a class of discrete anionic
metal−oxide clusters, have received much attention in terms of
carried out systematic researches on PMCDs and obtained a
series of satisfactory results.20 In addition, some PMCDs are
their unique properties and promising applications in many
efficient catalysts in many organic reactions, such as
different areas.1−7 Therein, transition metal substituted POMs
sulfoxidation of sulfides,21 epoxidation of olefins,6,22 and
(TMSPs) constitute a large subclass,8,9 and most of the
cycloaddition of CO2.23−26 Recently, a study demonstrated
reported TMSPs are still dominated by sandwich-type
that it is also feasible to catalyze the oxidation of alkanes with a
POMs.10 However, it is worth noting that other structure
Re-containing catalyst.27
motifs have been observed, common examples including
The oxidation of alkanes is a very primary and necessary
[MXW11Om]n−, [M3XW9O40]n− and [M3P2W15O62]n− (X =
transformation in the fine chemical industry,28,29 since the
SiIV, GeIV, PV, AsV, etc.).11,12 Among the above structural
products of C−H oxyfunctionalization, especially ketones, are
key intermediates in the manufacture of high-value chemicals
such as pharmaceuticals, insecticides, photoinitiators, and
perfumes.30,31 Traditionally, various stoichiometric amount
oxidizing agents (e.g., SeO2, CrO3, KMnO4, Na2ClO2, etc.)
have been widely employed in this reaction, but are gradually
phased out due to the production of a mass of environmentally
harmful contaminations.32,33 Therefore, the development of
efficiency and high selectivity catalytic system for C−H
motifs, monomeric Dawson polyoxotungstate [M3P2W15O62]n−
structures are usually assembled from a [α-P2W15O56]12−
precursor (P2W15), where M represents high-valence transition
metal ions such as VV and TaV.13,14 Up until now, the synthesis
of novel monomeric Dawson-type low valence transition
metal-substituted polyoxotungstates are still difficult, which
may be due to the size of the transition metals, the overall
charge of the POMs, and other thermodynamic factors.15
Reviewing the fabrication process of monomer structure
crystals, we found that exemplary synthesis strategies is to graft
or coordinate organic fragments, hexacoordinated modules, or
high-valence metal ions into the lacunary POM to form stable
molecular complexes.16,17 In 1980, Klemperer et al. first
attached M(CO)n+ species to a triangle of oxygen atoms on the
surface of polyoxoanion cluster.18 Later, Finke’s group
successfully synthesized two POM-supported metal carbonyl
Received: January 12, 2020
https://dx.doi.org/10.1021/acs.inorgchem.0c00111
© XXXX American Chemical Society
Inorg. Chem. XXXX, XXX, XXX−XXX
A

Inorganic Chemistry
pubs.acs.org/IC
Article
Table 1. Crystal Data and Structure Refinement for 1
empirical formula
formula weight
T/K
C3N7O76NaP2W15Co3Re
4555.77
296.15
crystal system
space group
a/Å
monoclinic
I2/a
24.9158(19)
b/Å
12.8802(10)
c/Å
52.754(5)
β/deg
V/Å3
98.2950(10)
16753(2)
Z
8
density/g cm−3
μ/mm−1
3.613
22.669
F(000)
15856.0
index ranges
reflections collected
independent reflections
data/restraints/parameters
GOF on F2
R1, wR2 [I ≥ 2σ(I)]
R1, wR2 [all data]
−29 ≤ h ≤ 29, −15 ≤ k ≤ 15, −62 ≤ l ≤ 51
42111
14876
14876/36/888
1.028
R1= 0.0452, wR2= 0.1119
R1= 0.0580, wR2= 0.1199
a
b
R1 = ∑||Fo| − |Fc||/∑|Fo|. wR2 = {∑[w(Fo − Fc2)2]/∑[w(Fo )2]}1/2
.
2
2
4600 spectrometer, and data were analyzed using the Peakview 2.0
software provided. X-ray photoelectron spectra (XPS) were recorded
with an Axis Ultra X-ray photoelectron spectrometer. The magnetic
susceptibility data were obtained on a Quantum Design MPMS-XL-7
magnetometer over the temperature range of 2−300 K at a magnetic
field of 1000 Oe. GC analyses were performed on Bruker 450-GC
with a flame ionization detector equipped with a 30 m column
(GsBP-1, 0.25 mm internal diameter and 0.25 μm film thickness) with
nitrogen as carrier gas.
Synthesis of Compound [Na(H2O)5](NH4)7[P2W15O56Co3-
(H2O)3(OH)3Re(CO)3]·13H2O (1). Re(CO)5Cl (0.036 g, 0.099
mmol) in 3 mL of CH3CN was refluxed in the dark at 70 °C for
0.5 h and then cooled to room temperature (denoted as solution A).
In another beaker, a mixture of P2W15 (0.22 g, 0.05 mmol),
Co(OAc)2·4H2O (0.075 g, 0.3 mmol) and LiOAc (0.05 g) was
dissolved in 12 mL of distilled water (denoted as solution B). After
being stirred at room temperature for about 10 min, the solution
gradually became clear. At this point, the pH value of the solution was
approximately 6.08. Then, solution A was added into the solution B
and stirred at 80 °C for 1 h. After that, NH4Cl (0.2 g) was added to
the resulting solution which continued to be stirred at room
temperature for about another 10 min and then was cooled and
filtered. The filtrate can be placed to evaporate slowly in the dark.
Pink crystals of 1 were collected after 2 weeks. Yield: 0.053 g (ca.
22.6%, based on W). Anal. (%) Calcd for C3H73N7O83NaP2W15Co3Re
(Mr = 4740.77): Co, 3.56; Re, 4.21; P, 1.15; W, 61.66; C, 0.75; H,
1.25; N, 2.04. Found: Co, 3.73; Re, 3.93; P, 1.31; W, 58.17; C, 0.76;
H, 1.54; N, 2.07. IR (KBr, cm−1): 3429 (m), 3196(m), 2016 (vs),
1890 (vs), 1632 (s), 1403 (vs), 1085 (s), 1040 (w), 1007 (w), 937
(w), 906 (s), 823 (s), 733 (vs), 597 (s), 520 (w).
General Procedure for the Oxidation of Alkanes. The
substrates (1 mmol), TBHP (3 equiv, 70 wt % in water), catalyst
(0.3 mol %), pyridine (0.3 equiv), and CH3CN (0.5 mL) were added
into a 50 mL glass reaction tube, and the mixture was heated at 90 °C
for 24 h. The products used qualitative detection by GC-MS. The
yield was monitored by GC with naphthalene as internal standard.
X-ray Crystallography. A suitable crystal of 1 was selected and
placed on a Bruker Apex-II CCD diffractometer. The diffraction
intensity data was collected at a temperature of 296.15 K using a
graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) as the
radiation source. Using Olex2,40 the structure was solved with the
ShelXS-1997 structure solution program using direct methods and
refined with the ShelXL refinement package41 using least squares
oxyfunctionalization with environmentally benign hydroper-
34
oxide oxidants, like H2O2 or TBHP,35 are urgent. Last year,
Hu’s group reported two ionic organic−inorganic hybrid
compounds, TBHP as an oxidant, vanadyl groups, and
[Cu(en)2]2+/[Co(en)2(H2O)2]3+ cocatalyzed the oxidation
reaction.36 Numerous literatures indicate that metal ions can
be regarded as active centers that enhance catalytic
activity.37,38 Hence, the introduction of a transition metal is
of great significance from the perspective of both synthesis
strategy and catalytic properties.
On the basis of the above reports and our group’s previous
works, Re(CO)5Cl and Co(OAc)2 were selected as the
metallic resources, and P2W15 precursor was used as the
building fragment to construct a desired PMCDs. By changing
the reaction parameters, pink rod crystals [Na(H2O)5]-
(NH4)7[P2W15O56Co3(H2O)3(OH)3Re(CO)3]·13H2O (1)
were gathered. Structural analysis revealed that compound 1
exhibited a discrete P2W18-like saturated Wells−Dawson
structure. Additionally, 1 was subjected to catalyze diphenyl-
methane (DPM) to benzophenone with 96.8% yield and >97%
selectivity.
EXPERIMENTAL SECTION
■
Materials and Methods. All reagents were purchased from the
commercial suppliers and used without further purification. Synthesis
of the Na12[(α-P2W15O56)]·24H2O was prepared followed by
literature method39 and further identified by the IR spectrum. The
IR spectrum was obtained on Bruker-Vertex 70 FT-IR spectrometer
through KBr pellet in the range of 400−4000 cm−1 region. Elemental
analyses (C, H, and N) were performed on a PerkinElmer 2400-II
CHNS/O analyzer. ICP-OES analyses (P, Mn, Co, and W) were
performed with a Perkin-Elemer Optima 2000 spectrometer. The
thermal gravimetric analyses (TGA) were measured in flowing N2
atmosphere on a NETZSCH STA 499 F5 thermal analyzer from 25 to
700 °C with a heating rate of 10 °C·min−1. The powder X-ray powder
diffraction (PXRD) patterns were carried out on a Bruker AXS D8
Advance diffractometer with Cu Kα radiation in the angular range 2θ
= 5−45° at 293 K. UV spectra were obtained with a U-4100
spectrometer at room temperature. Electrospray ionization mass
spectroscopy (ESI-MS) was performed on an AB SCIEX Triple TOF
B
https://dx.doi.org/10.1021/acs.inorgchem.0c00111
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
minimization on F2. In the last refinement cycles, the W, Co, Re, Na,
and P heavy atoms were refined anisotropically and the remaining
non-hydrogen atoms were isotropically refined. The lattice water
molecules were located by using a Fourier map and further
determined by TGA results. The crystallographic data and structural
refinement parameters are summarized in Table 1. Selected bond
lengths and angles of 1 are listed in Tables S1and S2.
RESULTS AND DISCUSSION
■
Synthesis and Structural Descriptions. Compound 1
was obtained from the reaction of P2W15, Co(OAc)2·4H2O,
LiOAc, and Re(CO)5Cl in a mixed CH3CN/H2O solvent. The
P2W15 was considered as an ideal framework candidate, the
substitution of CoII for WVI will increase the overall negative
charge of polyoxoanion, resulting in abnormal reactivity of the
O atom at the vacancy, and it is particularly easy to react with
42
+
{Re(CO)3 }. Most significant of all, addition of metal ions
was necessary to get title compound. As the comparative
experiment, P2W15 precursor isomerized into a P2W17 skeleton
in the absence of metal ions.43 Simultaneously, the substitution
positions on the surface of the polyoxoanion cluster changed
due to the different physical and chemical properties of Co and
Ni ions (Figure S1).10 The procedure followed for the
synthesis of 1 is summarized in Scheme 1.
Figure 1. (a) Ball-and-stick and polyhedral representations of the
polyanion [P2W15O56Co3(H2O)3(OH)3Re(CO)3]8− (1a). (b and d)
Ball-and stick representations of the {Re(CO)3} group and {Co3O6}
unit. (c and e) Polyhedral representations of the {P2W15Co3O62}
fragment and P2W15 building block. Color code: Re, rose; Co, rose-
carmine; W, tan; P, orange; O, red; C, black.
Scheme 1. Preparation Process of 1
Single crystal X-ray diffraction reveals that 1 crystallizes in
the monoclinic I2/a space group. Compound 1 possesses a
discrete P2W18-like saturated Wells−Dawson structure,
[P2W15O56Co3(H2O)3(OH)3Re(CO)3]8− (1a), with Na+/
+
NH4 mixed cations compensating for the charge of the
polyanion. As shown in Figure 1, the polyoxoanion 1a can be
considered as grafting a {Re(CO)3} pendants onto the
tricobalt-substituted POM cluster {P2W15Co3O62} building
block (Figure 1, parts b and c). Specifically, the building block
1c consists of a {Co3O6} cap (Figure 1d) embedded in the
defect sites of a P2W15 ligand (Figure 1e) through six Co−O−
W bridged linkages [Co−O, 2.016−2.056 Å; W−O, 1.755−
1.777 Å]. As we know, because the formation of POMs is
kinetically controlled, the sandwich-type structures with a
lower negative charge are preferred over the Dawson
structure.44 However, the accession of the {Re(CO)3} group
not only disrupts the assemblage of sandwich-type structure
but also stabilizes the role of the Dawson-like {P2W15Co3O62}
unit [Re−O, 2.136−2.157 Å, Co−O, 2.071−2.096 Å].
Additionally, the {Co3O6} ring in 1a is generated by the
coordination between one O atom and three {CoO6} units
that are in vertex-sharing and side-sharing. Alternatively, 1a is
also described as a mixed-metal cubane motif {ReCo3O4}
anchored on P2W15 polyanion (Figure 2), the oxygen atoms of
the {ReCo3O4} motif replaces oxygen atoms of the Dawson
structure, which closely resembles previously reported cubane
fragments {MnIII3MnIVO4} by Fang in 2010.45
Figure 2. Left: Ball-and-stick representation of the basic building
blocks {ReCo3O4} and P2W15 species. Right: ball-and-stick
representation of the polyoxoanion 1a. Color code: Re, rose; Co,
rose-carmine; W, tan; P, orange; O, red; C, black.
Besides this, two adjacent 1a afford a dimeric structure
bridged by two [Na(H2O)5]+ linkers (Figure S2). All Co and
Re atoms are six coordinated with octahedral geometry (Figure
S3). The bond valence sum (BVS) calculations46 show that the
three terminal O atoms connected with Co atom are
deprotonated and the three μ3-O atoms (O57, O58, and
O59) linking three adjacent Co atoms are monoprotonated
(Table S4). The XPS spectra of 1 are also recorded to further
testify the chemical valences of W, Co, and Re atoms. The
peaks of W 4f and Co 2p are observed at 35.6, 37.7, 780.9, and
796.8 eV, respectively; these observed values are basically in
agreement with the previously reported literature.47,48 The Re
4f7/2 peak at 41.9 eV is detected, which is consistent with the
Re 4f7/2 binding energy of 42.0 eV for Re(CO)5Cl, above
indicating that the oxidation state may be +1 (Figure S4).49
C
https://dx.doi.org/10.1021/acs.inorgchem.0c00111
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Electrospray Ionization Mass Spectroscopy (ESI-MS).
Single-crystalline samples of 1 were dissolved in the mixed
solvent CH3CN−H2O (3:1, volume ratio) and the observed
ESI mass spectrum was confirmed that 1 maintained its
integrity in solution by comparing the experimental and
simulated isotopic values of m/z (Figure 3). The spectrum
maximum value of 4.46 emu mol−1 at 1.8 K. The value of χMT
at 300 K is 11.84 emu K mol−1, which is much higher than the
theoretical value of 5.63 emu K mol−1 for three noninteracting
high-spin CoII ions calculated from the Van Vleck equation (S
= 3/2, g = 2).50 As the temperature decreases, the value of χMT
reduced to a minimum of 8.64 emu K mol−1 at 25 K.
Afterward, the χMT value increased rapidly to reach a
maximum of 9.39 emu mol−1 K at about 4 K and then
lessened sharply to 8.91 emu mol−1 K at 1.8 K. The decrease in
the 300−25 K temperature range is attributed to spin−orbit
coupling of CoII,51 while the maximum at 4 K is indicative of
the ferromagnetic CoII−CoII interactions within the trinuclear
spin cluster.52 The decrease observed under 4 K can be due to
intermolecular antiferromagnetic interactions, this conclusion
has been confirmed by our group’s prior work.23 In brief, the
magnetic behavior indicates that there exist overall ferromag-
netic interactions between the {Co3O6} triangle at low
temperature. The temperature dependence of the reciprocal
susceptibilities (χM−1) obeys the Curie−Weiss law above 30 K
for 1 with C = 12.31 emu K mol−1 and Θ = −17.66 K, which
further proves the presence of overall ferromagnetic coupling
between {Co3O6} triangles.
Catalytic Oxidation. According to the previous re-
ports,53,54 the activities of many metal complex catalysts
were obviously improved upon addition of additives. When
Na2CO3 and K3PO4 were affiliated to the catalytic system, the
yields of oxidation products were 35.7 and 39.8%, respectively.
However, the organic basic additives, such as triethylenetetr-
amine (TETA), 1,10-phenanthroline (phen), 2.2-bipyridine
(2.2-bpy), and pyridine, provided the highest yield of 48.4%
using pyridine as an additive (Figure 5). To further optimize
Figure 3. Negative-ion ESI-MS mass spectrum of 1 in mixed solvent
of CH3CN/H2O. (a−c) Expansion signals of 1 with four charges. (d)
Expansion signals of 1 with three charges (simulated spectrum in red
and experimental spectrum in black).
displayed some dominant peaks at 1040.11, 1054.36, and
1098.90 with a charge value of 4, corresponding to the formula
of NaH3[P2W15O56Co3Re(CO)2]4− (simulated 1040.17),
H4[P2W15O56Co3(OH)3Re(CO)3]4− (simulated 1054.43)
and (NH4)3H(H2O)5[P2W15O56Co3(H2O)3(OH)2Re-
(CO)3]4− (simulated 1098.97), respectively. Furthermore,
there was a peak located at m/z 1406.87 with a charge value
of 3 which belongs to H5[P2W15O56Co3(H2O)2(OH)Re-
(CO)3]3− (simulated 1406.91).
Magnetic Behavior. The magnetic susceptibility χM and
χMT versus T of 1 were measured at a constant magnetic field
of 1000 Oe in the range of 1.8−300 K, as shown in Figure 4.
The χM value of 1 was 0.04 emu mol−1 at 300 K; with cooling
of the temperature, the χM value of 1 quickly increased to a
Figure 5. Reaction conditions: DPM (1 mmol), TBHP (3 equiv, 70
wt % in water), catalyst (0.1 mol %), additive (0.1 equiv), CH3CN
(0.5 mL), T = 75 °C, and t = 24 h.
reaction conditions, the influences of various reaction
parameters were studied in detail, including the solvent,
temperature, the dosage of catalyst, and oxidant. The results
were summarized in Table 2. First, the impacts of different
solvents on the yields of the reaction were observed. The most
suitable solvent for this reaction was acetonitrile, affording a
superior yield to that of ethyl acetate, acetone, ethanol,
dichloromethane in the presence of 0.3 mol % of catalyst 1 at
−1
Figure 4. Plots of χM, χM and χMT versus T for 1 in the range of
1.8−300 K. The solid red line was generated from the best fit by the
Curie−Weiss expression in the range of 30−300 K with the Curie
constant C = 12.31 emu K mol−1 and the Weiss constant Θ = −17.66
K.
D
https://dx.doi.org/10.1021/acs.inorgchem.0c00111
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
a
Table 2. Optimization of the Oxidation of DPM with 1
b
c
entry
cat./mol %
oxid./equiv.
additive/equiv
T/°C
solvent
yield /%
sel. /%
1
2
3
4
5
6
7
8
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.2
0.4
0.3
0.3
0.3
0.3
TBHP/3
TBHP/3
TBHP/3
TBHP/3
TBHP/3
TBHP/3
TBHP/3
TBHP/3
30% H2O2/3
O2/1 MPa
TBHP/4
TBHP/3
TBHP/3
TBHP/3
TBHP/3
TBHP/3
TBHP/3
−
−
−
−
75
75
75
75
75
75
75
75
75
75
75
75
75
60
90
90
ethyl acetate
acetone
ethanol
20.8
21.3
22.2
2.7
93.5
92.9
92.7
89.4
DCM
−
acetonitrile
acetonitrile
acetonitrile
acetonitrile
acetonitrile
acetonitrile
acetonitrile
acetonitrile
acetonitrile
acetonitrile
acetonitrile
acetonitrile
acetonitrile
34.3
70.0
79.9
90.5
trace
N.R
89.6
47.6
88.8
47.1
96.8
95.6
35.4
>93
pyridine/0.1
pyridine/0.2
pyridine/0.3
pyridine/0.3
pyridine/0.3
pyridine/0.3
pyridine/0.3
pyridine/0.3
pyridine/0.3
pyridine/0.3
pyridine/0.3
pyridine/0.3
>93
>93
>95
N.D
N.D
>93
>93
>93
>93
>97
>95
9
10
11
12
13
14
15
d
16
17
f
90
89.5
a
b
Reaction conditions: DPM (1 mmol), TBHP (3 equiv, 70 wt % in water), t = 24 h. GC yields for target product benzophenone was based on
c
d
f
naphthalene as an internal standard, all of the products were identified by GC−MS spectra. Selectivity for ketone. 72 h. Second round. N.R: no
reaction. N.D: no defect.
75 °C (entries 1−5). The yield improved to 70.0% when 0.1
equiv of pyridine was added; this indicated that pyridine was
indispensable for this system (entry 6). Therefore, different
amounts of pyridine were tested, and 90.5% yield was obtained
until the amount of pyridine was increased to 0.3 equiv
(entries 7 and 8). Meanwhile, 30% H2O2 and O2 were applied
as the oxidants, only trace amount of corresponding product
even no product were defected (entries 9 and 10). Under the
condition of above parameters, even if adding more dosage of
the TBHP and catalyst, but there is no significant change in
yield (entries 11−13). When the temperature was raised from
60 to 90 °C, yields increased from 47.1 to 96.8%, even
extending the time of reaction, and the yield remained basically
constant (entries 14−16). Thus, it can be seen that the
competitive effect of the thermal decomposition (disproportio-
nation) of TBHP on the catalytic system can be neglected at
high temperatures.55
To highlight the benefit of 1, its catalytic activity was
compared to those of raw materials and other catalysts (Table
3). In the first series of experiments, the blank experiment was
carried out without any 1 and pyridine at 90 °C for 24 h,
leading to a yield of 24.4% (entry 1; Figure 6, black square).
When the reactions were conducted with either 1 or pyridine,
the yield of DPM with only 1 was higher than that observed
with only pyridine (entry 2 and 3; Figure 6, red circle and
orange triangle). Accidentally, when both 1 and pyridine were
present in the reaction system, the yield was dramatically
enhanced to 96.8% after 24 h (entry 11; Figure 6, brown
rhombus). Furthermore, the catalytic activities of P2W15
precursor, Re(CO)5Cl and Co(OAc)2 for the oxidation of
DPM, were also independently investigated with pyridine as an
additive. Among them, Re(CO)5Cl and Co(OAc)2 behaved
more active than other raw materials (entries 5−8), which
implied that Lewis acid metal atoms played major roles in this
Table 3. Oxidation of DPM Catalyzed by Different
Catalysts
a
b
c
entry
catalyst
additive
yield /% sel. /%
1
2
3
4
5
6
7
8
−
1
−
P2W15
−
−
24.4
42.8
32.4
26.9
38.9
75.9
63.1
21.5
86.3
84.6
96.8
39.9
57.4
44.0
>98
>93
>93
>97
>93
>93
>94
>94
>97
>95
>97
>89
>82
>82
pyridine
pyridine
pyridine
pyridine
−
Re(CO)5Cl
Co(OAc)2
Co(OAc)2
Re(CO)5Cl
Co(OAc)2 + Re(CO)5Cl
mixture
−
9
pyridine
pyridine
pyridine
pyridine
pyridine
pyridine
10
11
12
13
14
1
[{Re(CO)3}4(Mo4O16)]4−
{[Mn(CO)3]4(Se2W11O43)}8−
[Te2W20O70{Re(CO)3}2]10−
a
Reaction conditions: DPM (1 mmol), TBHP (3 equiv, 70 wt % in
water), catalyst (0.3 mol %), pyridine (0.3 equiv), CH3CN (0.5 mL),
b
T = 90 °C, and t = 24 h. Yield for target product benzophenone was
based on naphthalene as an internal standard. All of the products
c
were identified by GC−MS spectra.
transformation. The control experiments of Re(CO)5Cl and
Co(OAc)2 further proved our speculation (entry 9). In
addition, a simple mixture of them suggested the P2W15
precursor did not have an obvious contribution to the system
(entry 10). In the second series of experiments, several
PMCDs catalysts reported by our group were used for the
E
https://dx.doi.org/10.1021/acs.inorgchem.0c00111
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
oxidation of alkanes (entries 12−14). Among these catalysts, 1
is more active than them, which once again testified that it is
necessary to implant transition metals. Compared with other
catalysts, the catalyst 1 afforded a TOF of 13.44 h−1 within 24
h, which was superior to that of the previously reported POM-
based catalysts, such as [Pd(dpa)(acac)]2[V6O13(OMe)6]
(3.98 h−1) and [CuII(C2N2H8)2]4[CuII(C2N2H8)2(H2O)2]2-
[PNb12O40VVVIVO2]·(OH)2·11H2O (1.17 h−1) (Table
S5).36,56 The fact revealed that 1 was more efficient than
many catalysts.
Scope of Substrates. Inspired by the above good results,
the optimized reaction condition was then tested for other
substrates. The result is shown in Table 4. In general, the
ethylbenzene derivatives gave the corresponding acetophe-
nones in good-to-excellent yields. However, the 4-ethylanisole
resulted in a lower yield (entries 1−5). The aryl group in a
cyclic system gave moderate yield with 90.8% selectivity of 1-
tetralone and 9.2% selectivity of 2,3-dihydronaphthalene-1,4-
dione (entry 6). Excellent yields were obtained for fluorine at 8
h (entry 7). The standard reaction condition was applied to
heteroatom-containing substrates, which were ineffective for 2-
substituted derivatives (entries 8−11). As for cyclohexane and
cyclohexene, the results were not as positive as presented
Figure 6. Kinetic profiles for the oxidation of DPM with pyridine
under optimal conditions.
a
Table 4. Catalytic Oxidation of Different Substrates
a
Reaction conditions: substrate (1 mmol), TBHP (3 equiv., 70 wt % in water), catalyst (0.3 mol %), pyridine (0.3 equiv), CH3CN (0.5 mL), T =
90 °C, t = 24 h. bGC yields for target product benzophenone was based on naphthalene as an internal standard; all of the products were identified
by GC−MS spectra. 9.2% selectivity of 2,3-dihydronaphthalene-1,4-dione.
c
F
https://dx.doi.org/10.1021/acs.inorgchem.0c00111
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
above (entries 12 and 13). What is noteworthy is that the yield
of cyclohexene is greater than cyclohexane because of the
different activation of α-hydrogen.57
AUTHOR INFORMATION
■
Corresponding Authors
Jingyang Niu − Henan Key Laboratory of Polyoxometalate
Chemistry, College of Chemistry and Chemical Engineering,
Henan University, Kaifeng 475004, Henan, P. R. China;
orcid.org/0000-0001-6526-7767; Email: jyniu@
henu.edu.cn
Jingping Wang − Henan Key Laboratory of Polyoxometalate
Chemistry, College of Chemistry and Chemical Engineering,
Henan University, Kaifeng 475004, Henan, P. R. China;
Email: jpwang@henu.edu.cn
Mechanism. To get an insight into the mechanism for the
oxidation of alkanes to ketones, further several comparative
experiments were consequently conducted. First, the recovered
catalyst only acquired 35.4% yield under above condition
(Table 2, entry 17), which may be result from the deactivation
of catalytic sites by coordination of pyridine with the metal
atoms in PMCDs.58,59 As reported earlier, pyridine plays a role
in accelerating the formation of catalytically active substances
and promoting the decomposition of alkyl peroxide in this
reaction,59,60 and pyridine can also form pyridine derivatives
with a hydrocarbyl radical to compete with the alkyl substrate.
However, no pyridine derivatives were detected in our work,
which may be due to the small amount used. In another
experiment, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)
and 2,6-di-tert-butyl-4-methylphenol (BHT) as the free-radical
inhibitors were employed, and the catalytic activities
plummeted to 24.1% and 21.5% yields, respectively (Figure
S11). At 90 °C, decomposition of TBHP generates free alkoxy
groups (RO•) and alkyl peroxy radicals (ROO•), leading to an
increased chain initiation rate. Subsequently, PMCD catalyst
acts as an initiator to promote the decomposition rate of
TBHP and hence the overall reaction rate.61 Generated radical
RO• activates the α-carbon of DPM and to give another alkane
radical, which produces a peroxide intermediate with the
radical ROO•. The discovery of cyclohexene-3-(tert-butyl)-
peroxide intermediate by GC−MS illustrated the rationality of
the above step (Figure S13). Finally, the peroxide intermediate
decomposes to products. The relevant processes have been
displayed in Figure S12.
Authors
Xinyi Ma − Henan Key Laboratory of Polyoxometalate
Chemistry, College of Chemistry and Chemical Engineering,
Henan University, Kaifeng 475004, Henan, P. R. China
Ping Wang − Henan Key Laboratory of Polyoxometalate
Chemistry, College of Chemistry and Chemical Engineering,
Henan University, Kaifeng 475004, Henan, P. R. China
Zhihao Liu − Henan Key Laboratory of Polyoxometalate
Chemistry, College of Chemistry and Chemical Engineering,
Henan University, Kaifeng 475004, Henan, P. R. China
Changhui Xin − Henan Key Laboratory of Polyoxometalate
Chemistry, College of Chemistry and Chemical Engineering,
Henan University, Kaifeng 475004, Henan, P. R. China
Siyu Wang − Henan Key Laboratory of Polyoxometalate
Chemistry, College of Chemistry and Chemical Engineering,
Henan University, Kaifeng 475004, Henan, P. R. China
Jiage Jia − Henan Key Laboratory of Polyoxometalate Chemistry,
College of Chemistry and Chemical Engineering, Henan
University, Kaifeng 475004, Henan, P. R. China
Pengtao Ma − Henan Key Laboratory of Polyoxometalate
Chemistry, College of Chemistry and Chemical Engineering,
Henan University, Kaifeng 475004, Henan, P. R. China
CONCLUSION
■
In summary, a mixed metal-decorated phosphotungstate
rhenium carbonyl derivative has been synthesized and
characterized. Solution behavior examined via ESI-MS showed
that the complex was stable in CH3CN medium. Notably, 1
can efficiently catalyze the oxidation of DPM, achieving a
96.8% yield of the target product benzophenone. In future
work, further efforts will be devoted to constructing novel
POMs with high stability and catalytic properties for oxidation
of alkanes by adjusting different reaction components. This
work is ongoing in our group.
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.inorgchem.0c00111
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
ASSOCIATED CONTENT
■
We gratefully acknowledge financial support from the Natural
Science Foundation of China (Grants 21571050, 21573056,
21771053, 21771054) and the 2019 Student Innovative Pilot
Plan of Henan University (201910475079).
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.inorgchem.0c00111.
Selected bond distances and angles, BVS, available
structural figure, XPRD, IR, XPS, TG, the electro-
chemistry behavior, and the catalytic behavior of 1
(PDF)
REFERENCES
■
(1) Wang, S.-S.; Yang, G.-Y. Recent Advances in Polyoxometalate-
Catalyzed Reactions. Chem. Rev. 2015, 115, 4893−4962.
(2) Long, D.-L.; Tsunashima, R.; Cronin, L. Polyoxometalates:
Building Blocks for Functional Nanoscale Systems. Angew. Chem., Int.
Ed. 2010, 49, 1736−1758.
(3) Du, D.-Y.; Yan, L.-K.; Su, Z.-M.; Li, S.-L.; Lan, Y.-Q.; Wang, E.-
B. Chiral Polyoxometalate-Based Materials: From Design Syntheses
to Functional Applications. Coord. Chem. Rev. 2013, 257, 702−717.
(4) Weinstock, I. A.; Schreiber, R. E.; Neumann, R. Dioxygen in
Polyoxometalate Mediated Reactions. Chem. Rev. 2018, 118, 2680−
2717.
Accession Codes
CCDC 1968412 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
G
https://dx.doi.org/10.1021/acs.inorgchem.0c00111
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
(5) Ma, P.; Hu, F.; Wang, J.; Niu, J. Carboxylate Covalently
Modified Polyoxometalates: From Synthesis, Structural Diversity to
Applications. Coord. Chem. Rev. 2019, 378, 281−309.
(6) Li, J.; Guo, J.; Jia, J.; Ma, P.; Zhang, D.; Wang, J.; Niu, J.
Isopentatungstate-Supported Metal Carbonyl Derivative: Synthesis,
Characterization, and Catalytic Properties for Alkene Epoxidation.
Dalton Trans. 2016, 45, 6726−6731.
New Tellurotungstate(IV)-Supported Rhenium Carbonyl Derivative.
Dalton Trans. 2019, 48, 628−634.
(23) Jia, J.; Niu, Y.; Zhang, P.; Zhang, D.; Ma, P.; Zhang, C.; Niu, J.;
Wang, J. A Monomeric Tricobalt(II)-Substituted Dawson-Type
Polyoxometalate Decorated by a Metal Carbonyl Group:
[P2W15O56Co3(H2O)3(OH)3Mn(CO)3]8−. Inorg. Chem. 2017, 56,
10131−10134.
(7) Proust, A.; Matt, B.; Villanneau, R.; Guillemot, G.; Gouzerh, P.;
Izzet, G. Functionalization and Post-Functionalization: A Step
towards Polyoxometalate-Based Materials. Chem. Soc. Rev. 2012, 41,
7605−7622.
(8) Dolbecq, A.; Dumas, E.; Mayer, C. R.; Mialane, P. Hybrid
Organic−Inorganic Polyoxometalate Compounds: From Structural
Diversity to Applications. Chem. Rev. 2010, 110, 6009−6048.
(9) Bassil, B. S.; Kortz, U. Divacant Polyoxotungstates: Reactivity of
the Gamma-Decatungstates [γ-XW10O36]8− (X = Si, Ge). Dalton
Trans. 2011, 40, 9649−9661.
(10) Gabb, D.; Pradeep, C. P.; Miras, H. N.; Mitchell, S. G.; Long,
D.-L.; Cronin, L. Organic-Soluble Lacunary {M2(P2W15)2}
Polyoxometalate Sandwiches Showing a Previously Unseen Aββα
Isomerism. Dalton Trans. 2012, 41, 10000−10005.
(11) Jorris, T. L.; Kozik, M.; Casan-Pastor, N.; Domaille, P. J.; Finke,
R. G.; Miller, W. K.; Baker, L. C. W. Effects of Paramagnetic and
Diamagnetic Transition-Metal Monosubstitutions on 183W and 31P
NMR Spectra for Keggin and Wells-Dawson Heteropolytungstate
Derivatives. J. Am. Chem. Soc. 1987, 109, 7402−7408.
(24) Lu, J.; Ma, X.; Singh, V.; Zhang, Y.; Wang, P.; Feng, J.; Ma, P.;
Niu, J.; Wang, J. Facile CO2 Cycloaddition to Epoxides by Using a
Tetracarbonyl Metal Selenotungstate Derivate [{Mn-
(CO)3}4(Se2W11O43)]8−. Inorg. Chem. 2018, 57, 14632−14643.
(25) Huo, Z.; Zhao, J.; Bu, Z.; Ma, P.; Liu, Q.; Niu, J.; Wang, J.
Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides
Catalyzed by a Keggin-Type Polyoxometalate-Supported Rhenium
Carbonyl Derivate in Ionic Liquid. ChemCatChem 2014, 6, 3096−
3100.
(26) Huo, Z.; Guo, J.; Lu, J.; Xu, Q.; Ma, P.; Zhao, J.; Zhang, D.;
Niu, J.; Wang, J. A Nona-Vacant Keggin-Type Tricarbonyl Rhenium
Derivative {[PMo3O16][Re(CO)3]4}5− and Its Catalytic Performance
for CO2 Cycloaddition Reactions. RSC Adv. 2015, 5, 69006−69009.
(27) Peng, H.; Lin, A.; Zhang, Y.; Jiang, H.; Zhou, J.; Cheng, Y.;
Zhu, C.; Hu, H. Oxidation and Amination of Benzylic Sp3 C−H Bond
Catalyzed by Rhenium(V) Complexes. ACS Catal. 2012, 2, 163−167.
(28) Song, G.; Wang, F.; Li, X. C−C, C−O and C−N Bond
Formation via Rhodium(III)-Catalyzed Oxidative C−H Activation.
Chem. Soc. Rev. 2012, 41, 3651−3678.
́
́
(12) Clemente-Juan, J. M.; Coronado, E.; Galan-Mascaros, J. R.;
(29) Balcells, D.; Clot, E.; Eisenstein, O. C−H Bond Activation in
Transition Metal Species from a Computational Perspective. Chem.
Rev. 2010, 110, 749−823.
́
Gomez-García, C. J. Increasing the Nuclearity of Magnetic
Polyoxometalates. Syntheses, Structures, and Magnetic Properties of
Salts of the Heteropoly Complexes [Ni3(H2O)3(PW10O39)H2O]7−,
(30) Yamaguchi, J.; Yamaguchi, A. D.; Itami, K. C−H Bond
Functionalization: Emerging Synthetic Tools for Natural Products
and Pharmaceuticals. Angew. Chem., Int. Ed. 2012, 51, 8960−9009.
(31) Chen, K.; Zhang, P.; Wang, Y.; Li, H. Metal-Free Allylic/
Benzylic Oxidation Strategies with Molecular Oxygen: Recent
Advances and Future Prospects. Green Chem. 2014, 16, 2344−2374.
(32) Lam, W. W. Y.; Yiu, S.-M.; Lee, J. M. N.; Yau, S. K. Y.; Kwong,
H.-K.; Lau, T.-C.; Liu, D.; Lin, Z. BF3-Activated Oxidation of Alkanes
1 0 −
[ N i ( H O )
( P W
O
) ]
2
,
a n d
4
2
2
9
3 4
[Ni9(OH)3(H2O)6(HPO4)2(PW9O34)3]16−. Inorg. Chem. 1999, 38,
55−63.
(13) Hou, Y.; Hill, C. L. Hydrolytically Stable Organic Triester
Capped Polyoxometalates with Catalytic Oxygenation Activity of
Formula [RC(CH2O)3V3P2W15O59]6− (R = CH3, NO2, CH2OH). J.
Am. Chem. Soc. 1993, 115, 11823−11830.
(14) Huang, P.; Wang, X.-J.; Qi, J.-J.; Wang, X.-L.; Huang, M.; Wu,
H.-Y.; Qin, C.; Su, Z.-M. Self-Assembly and Photocatalytic H2
Evolution Activity of Two Nanoscale Polytantalotungstates Based
on Unprecedented {Cr3Ta6} and {Cr4Ta12} Clusters. J. Mater. Chem.
A 2017, 5, 22970−22974.
(15) Guo, W.; Lv, H.; Bacsa, J.; Gao, Y.; Lee, J. S.; Hill, C. L.
Syntheses, Structural Characterization, and Catalytic Properties of Di-
and Trinickel Polyoxometalates. Inorg. Chem. 2016, 55, 461−466.
(16) Gouzerh, P.; Proust, A. Main-Group Element, Organic, and
Organometallic Derivatives of Polyoxometalates. Chem. Rev. 1998, 98,
77−112.
(17) Li, S.; Zhou, Y.; Peng, Q.; Wang, R.; Feng, X.; Liu, S.; Ma, X.;
Ma, N.; Zhang, J.; Chang, Y.; Zheng, Z.; Chen, X. Controllable
Synthesis and Catalytic Performance of Nanocrystals of Rare-Earth-
Polyoxometalates. Inorg. Chem. 2018, 57, 6624−6631.
−
by MnO4 . J. Am. Chem. Soc. 2006, 128, 2851−2858.
(33) Muzart, J. Chromium-Catalyzed Oxidations in Organic
Synthesis. Chem. Rev. 1992, 92, 113−140.
(34) Srour, H.; Le Maux, P.; Chevance, S.; Simonneaux, G. Metal-
Catalyzed Asymmetric Sulfoxidation, Epoxidation and Hydroxylation
by Hydrogen Peroxide. Coord. Chem. Rev. 2013, 257, 3030−3050.
(35) Khenkin, A. M.; Neumann, R. Redirection of Oxidation
Reactions by a Polyoxomolybdate: Oxydehydrogenation Instead of
Oxygenation of Alkanes with Tert-Butylhydroperoxide in Acetic Acid.
J. Am. Chem. Soc. 2001, 123, 6437−6438.
(36) Hu, J.; Dong, J.; Huang, X.; Chi, Y.; Lin, Z.; Li, J.; Yang, S.; Ma,
H.; Hu, C. Immobilization of Keggin Polyoxovanadoniobate in
Crystalline Solids to Produce Effective Heterogeneous Catalysts
towards Selective Oxidation of Benzyl-Alkanes. Dalton Trans. 2017,
46, 8245−8251.
(18) Besecker, C. J.; Klemperer, W. G. Polyoxoanion-Supported
Metal Carbonyls: Syntheses of the [(OC)3M(Nb2W4O19)]3− Anions
(M = Re and Mn). J. Am. Chem. Soc. 1980, 102, 7598−7600.
(19) Nagata, T.; Pohl, M.; Weiner, H.; Finke, R. G. Polyoxoanion-
Supported Organometallic Complexes: Carbonyls of Rhenium(I),
Iridium(I), and Rhodium(I) That Are Soluble Analogs of Solid-
(37) Guo, C.-C.; Chu, M.-F.; Liu, Q.; Liu, Y.; Guo, D.-C.; Liu, X.-Q.
Effective Catalysis of Simple Metalloporphyrins for Cyclohexane
Oxidation with Air in the Absence of Additives and Solvents. Appl.
Catal., A 2003, 246, 303−309.
(38) Guo, C.-C.; Liu, X.-Q.; Liu, Y.; Liu, Q.; Chu, M.-F.; Zhang, X.-
B. Studies of Simple μ-Oxo-Bisiron(III)Porphyrin as Catalyst of
Cyclohexane Oxidation with Air in Absence of Cocatalysts or
Coreductants. J. Mol. Catal. A: Chem. 2003, 192, 289−294.
(39) Finke, R. G.; Droege, M. W.; Domaille, P. J. Trivacant
Heteropolytungstate Derivatives. Rational Syntheses, Characteriza-
tion, Two-Dimensional 183W NMR, and Properties of Tungstome-
+
+
Oxide-Supported M(CO)n and That Exhibit Novel M(CO)n
Mobility. Inorg. Chem. 1997, 36, 1366−1377.
(20) Lu, J.; He, P.; Niu, J.; Wang, J. Polyoxometalate-Supported
Metal Carbonyl Derivatives: From Synthetic Strategies to Structural
Diversity and Applications. Inorg. Chem. Front. 2019, 6, 3041−3056.
(21) Lu, J.; Ma, X.; Singh, V.; Zhang, Y.; Ma, P.; Zhang, C.; Niu, J.;
Wang, J. An Isotetramolybdate-Supported Rhenium Carbonyl
Derivative: Synthesis, Characterization, and Use as a Catalyst for
Sulfoxidation. Dalton Trans. 2018, 47, 5279−5285.
10−
16−
tallophosphates P2W18M4(H2O)2O68 and P4W30M4(H2O)2O112
(M = Co, Cu, Zn). Inorg. Chem. 1987, 26, 3886−3896.
(40) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A.
K.; Puschmann, H. OLEX2: A Complete Structure Solution,
Refinement and Analysis Program. J. Appl. Crystallogr. 2009, 42,
339−341.
(22) Lu, J.; Ma, X.; Wang, P.; Feng, J.; Ma, P.; Niu, J.; Wang, J.
Synthesis, Characterization and Catalytic Epoxidation Properties of a
H
https://dx.doi.org/10.1021/acs.inorgchem.0c00111
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
(41) Sheldrick, G. M. Crystal Structure Refinement with SHELXL.
Acta Crystallogr. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3−
8.
(42) Anderson, T. M.; Zhang, X.; Hardcastle, K. I.; Hill, C. L.
Reactions of Trivacant Wells-Dawson Heteropolytungstates Ionic
Strength and Jahn-Teller Effects on Formation in Multi-Iron
Complexes. Inorg. Chem. 2002, 41, 2477−2488.
(43) Lu, J.; Feng, J.; Ma, X.; Wang, P.; Xu, B.; He, P.; Jia, J.; Ma, P.;
Niu, J.; Wang, J. A New Phosphotungstate-Supported Rhenium
Carbonyl Derivative: Synthesis, Characterization and Catalytic
Selective Oxidation of Thiophenes. CrystEngComm 2019, 21,
7322−7328.
(44) Canny, J.; Teze, A.; Thouvenot, R.; Herve, G. Disubstituted
Tungstosilicates. Synthesis, Stability, and Structure of the Lacunary
Precursor Polyanionγ-SiW10O368−. Inorg. Chem. 1986, 25, 2114−
2119.
(58) Lever, A. B. P.; Ogden, D. Haloacetate Complexes of
Cobalt(II), Nickel(II), and Copper(II), and the Question of Band
Assignments in the Electronic Spectra of Six-Co-Ordinate Cobalt(II)
Complexes. J. Chem. Soc. A 1967, 2041−2048.
(59) Shul’pin, G. B.; Kirillova, M. V.; Kozlov, Y. N.; Shul’pina, L. S.;
Kudinov, A. R.; Pombeiro, A. J. L. Decamethylosmocene-Catalyzed
Efficient Oxidation of Saturated and Aromatic Hydrocarbons and
Alcohols with Hydrogen Peroxide in the Presence of Pyridine. J.
Catal. 2011, 277, 164−172.
(60) Gozzo, F. Radical and Non-radical Chemistry of the Fenton-
like Systems in the Presence of Organic Substrates. J. Mol. Catal. A:
Chem. 2001, 171, 1−22.
(61) Raji, V.; Chakraborty, M.; Parikh, P. A. Catalytic Performance
of Silica-Supported Silver Nanoparticles for Liquid-Phase Oxidation
of Ethylbenzene. Ind. Eng. Chem. Res. 2012, 51, 5691−5698.
(45) Fang, X.; Speldrich, M.; Schilder, H.; Cao, R.; O’Halloran, K.
III
P.; Hill, C. L.; Kogerler, P. Switching Slow Relaxation in a Mn 3MnIV
̈
Cluster: An Example of Grafting Single-Molecule Magnets onto
Polyoxometalates. Chem. Commun. 2010, 46, 2760−2762.
(46) Brown, I. D.; Altermatt, D. Bond-Valence Parameters Obtained
from a Systematic Analysis of the Inorganic Crystal Structure
Database. Acta Crystallogr., Sect. B: Struct. Sci. 1985, 41, 244−247.
(47) Yang, G.-P.; Shang, S.-X.; Yu, B.; Hu, C.-W. Ce(III)-Containing
Tungstotellurate(VI) with Sandwich Structure: An Efficient Lewis
Acid-Base Catalyst for the Condensation Cyclization of 1,3-Diketones
with Hydrazines/Hydrazides or Diamines. Inorg. Chem. Front. 2018,
5, 2472−2477.
(48) Tan, B. J.; Klabunde, K. J.; Sherwood, P. M. A. XPS Studies of
Solvated Metal Atom Dispersed (SMAD) Catalysts Evidence for
Layered Cobalt-Manganese Particles on Alumina and Silica. J. Am.
Chem. Soc. 1991, 113, 855−861.
(49) Nefedov, V. I.; Salyn, Y. V.; Shtemenko, A. V.; Kotelnikova, A.
S. X-Ray Photoelectron Study of Trans-Influence of the Re-Re
Multiple Bond. Inorg. Chim. Acta 1980, 45, L49−L50.
(50) Feng, J.-S.; Bao, S.-S.; Ren, M.; Cai, Z.-S.; Zheng, L.-M.
Chirality- and PH-Controlled Supramolecular Isomerism in Cobalt
Phosphonates and Its Impact on the Magnetic Behavior. Chem. - Eur.
J. 2015, 21, 17336−17343.
(51) Bassil, B. S.; Kortz, U.; Tigan, A. S.; Clemente-Juan, J. M.;
Keita, B.; de Oliveira, P.; Nadjo, L. Cobalt-Containing Silicotungstate
Sandwich Dimer [{Co3 (B-ß-SiW9 O3 3 (OH))(B-ß-Si-
W8O29(OH)2)}2]22−. Inorg. Chem. 2005, 44, 9360−9368.
́
̃
o, A.; Gimenez-
(52) Clemente-Juan, J. M.; Coronado, E.; Gaita-Arin
Saiz, C.; Gudel, H.-U.; Sieber, A.; Bircher, R.; Mutka, H. Magnetic
̈
Polyoxometalates: Anisotropic Exchange Interactions in the Moiety of
[(NaOH2)Co3(H2O)(P2W15O56)2]17−. Inorg. Chem. 2005, 44, 3389−
3395.
(53) Kirillov, A. M.; Shul’pin, G. B. Pyrazinecarboxylic Acid and
Analogs: Highly Efficient Co-Catalysts in the Metal-Complex-
Catalyzed Oxidation of Organic Compounds. Coord. Chem. Rev.
2013, 257, 732−754.
(54) Hruszkewycz, D. P.; Miles, K. C.; Thiel, O. R.; Stahl, S. S. Co/
NHPI-Mediated Aerobic Oxygenation of Benzylic C−H Bonds in
Pharmaceutically Relevant Molecules. Chem. Sci. 2017, 8, 1282−1287.
(55) Macedo, A.; Fernandes, S. E.; Valente, A.; Ferreira, R. A.;
Carlos, L.; Rocha, J. Catalytic Performance of Ceria Nanorods in
Liquid-Phase Oxidations of Hydrocarbons with tert-Butyl Hydro-
peroxide. Molecules 2010, 15, 747−765.
(56) Li, J.-K.; Huang, X.-Q.; Yang, S.; Ma, H.-W.; Chi, Y.-N.; Hu, C.-
W. Four Alkoxohexavanadate-Based PdPolyoxovanadates as Robust
Heterogeneous Catalysts for Oxidation of Benzyl-Alkanes. Inorg.
Chem. 2015, 54, 1454−1461.
(57) Jiang, J.; Wang, J.-X.; Zhou, X.-T.; Chen, H.-Y.; Ji, H.-B.
Mechanistic Understanding towards the Role of Cyclohexene in
Enhancing the Efficiency of Manganese Porphyrin-Catalyzed Aerobic
Oxidation of Diphenylmethane. Eur. J. Inorg. Chem. 2018, 2018,
2666−2674.
I
https://dx.doi.org/10.1021/acs.inorgchem.0c00111
Inorg. Chem. XXXX, XXX, XXX−XXX