Multinuclear transition metal-containing polyoxometalates constructed from Nb/W mixed-addendum precursors: synthesis, structures and catalytic performance

Article abstract of DOI:10.1039/d1dt00924a

Four new transition metal-containing Nb/W mixed-addendum POM trimers with the formula H₁₉[M₄(H₂O)_x(P₂W₁₅Nb₃O₆₂)₃]·m(HCOOH)·nH₂O (M = Cu,x= 15,m=

Full text of DOI:10.1039/d1dt00924a

Dalton
Transactions
View Article Online
View Journal
PAPER
Multinuclear transition metal-containing
polyoxometalates constructed from Nb/W
mixed-addendum precursors: synthesis,
structures and catalytic performance†
Cite this: DOI: 10.1039/d1dt00924a
a
a
a
a
a
a
Wanru Xiao, Shujun Li, * Yue Zhao, Yubin Ma, Na Li, Jie Zhang
and
a,b
Xuenian Chen
*
Four new transition metal-containing Nb/W mixed-addendum POM trimers with the formula
(H O) (P ]·m(HCOOH)·nH O (M = Cu, x = 15, m = 0, and n = 21, Cu-POM; M = Co, x
7, m = 0, and n = 15, Co-POM; M = Mn, x = 7, m = 6, and n = 18, Mn-POM; and M = Zn, x = 7, m = 0,
H
19[M
4
2
x
2
W15Nb
3
O
62
)
3
2
=
and n = 23, Zn-POM) have been synthesized by a solvothermal method in a water–ethanol mixed solvent.
All the four compounds were characterized by single-crystal X-ray diffraction, powder X-ray diffraction
(XRD), IR spectroscopy, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS).
These compounds can serve as efficient heterogeneous catalysts for the cyanosilylation of different car-
bonyl compounds under ambient temperature and solvent-free conditions, and Cu-POM shows much
better catalytic performance than the other three compounds. The cycle experiment showed that Cu-
POM can be reused for at least five cycles without significant loss of catalytic activity. The IR spectroscopy
and XRD analysis revealed that Cu-POM can retain its integrity after catalysis.
Received 21st March 2021,
Accepted 28th April 2021
DOI: 10.1039/d1dt00924a
rsc.li/dalton
1
0−
wich-type polyoxometalate [Co
1
4
(H
2
O)
2
(B-α-PW
9
O
34
)
2
]
in
Introduction
1
9
973. In addition, the self-assembly of metal salts or metal
Transition-metal-substituted POMs (TMSPs) as a large subclass oxides (e.g. Na WO and WO ) with TMs was also used to con-
2
4
3
of polyoxometalates (POMs) are attracting considerable atten- struct the TMSP structure. Mialane and co-workers obtained
1
–3
10−
tion in recent years. The replacement of 3d transition metal two Fe-substituted compounds [Fe
4
(H
by the reaction of Na WO
4
2
O)
2
(FeW
9
O
34
)
2
]
and
1
9−
(
TM) ions Mn, Co, Ni, Cu, etc. in POMs results in abundant [(Fe W O (H O)) (FeW O )]
structure diversity, for instance mono- and multi-substituted and FeCl
4 9 34 2 2 6 26
2
2
0
3
.
From the experimental point of view, convention-
and high-nuclear metal-substituted derivatives, and fascinat- al aqueous solution synthesis and hydrothermal synthesis are
4
–7
8–11
ing properties applicable to magnetism,
electrochemistry,
catalysis,
the most common methods for these TMSPs due to their rela-
tively simple synthesis process. However, a solvothermal
1
2–14
15–17
medicine and materials science.
An effective synthesis approach to TMSPs is utilizing the method was rarely used in the synthesis of TMSPs.
reactions of lacunary POM precursors (such as lacunary Keggin
Mixed-addendum POMs as a branch of POMs have received
9
/10−
V
IV
IV
12−
[
XW
9
O
34
]
(X = P /Si /Ge ) or Dawson [P
2
W
15
O
56
]
) and increasing attention because they can serve as excellent precur-
1
8
TM ions. A typical example is the synthesis of the first sand- sors to react with nucleophilic reagents. The substitution of
V
V
VI
Nb /Ta for W will raise the charge of the whole polyoxoa-
nion and endow the POMs with high reactivity due to the
increased nucleophilicity and basicity of the O atoms con-
a
School of Chemistry and Chemical Engineering, Henan Key Laboratory of Boron
Chemistry and Advanced Energy Materials, Key Laboratory of Green Chemical Media
and Reactions, Ministry of Education, Collaborative Innovation Centre of Henan
Province for Green Manufacturing of Fine Chemicals, Henan Normal University,
Xinxiang, 453007, China. E-mail: lisj@htu.edu.cn
21
nected to Nb or Ta. Utilizing these features, a series of com-
pounds based on Nb (Ta)/W mixed-addendum POMs have
been synthesized, for example, Nb/W mixed-addendum POM-
b
22–24
College of Chemistry and Molecular Engineering Zhengzhou University, Zhengzhou,
supported organometallic complexes,
lanthanide-func-
2
1,25
26
450001, China. E-mail: xnchen@htu.edu.cn
tional POMs,
boronic acid covalent functionalized POMs,
†
Electronic supplementary information (ESI) available: Experimental pro-
27
and boronic acid modified Ln–POMs.
cedures, crystallographic structures, FTIR spectroscopy, thermal analyses, PXRD
patterns, and catalytic data for the title compounds. CCDC 2044367–2044370.
For ESI and crystallographic data in CIF or other electronic format see DOI:
In this work, we obtained four POM trimers, which were
synthesized by the reaction of the Nb/W mixed-addendum
9
−
2+
2+
2+
2+
10.1039/d1dt00924a
POM [P
2
W
15Nb
3
O
62
]
and TM ions (Cu , Co , Mn , Zn )
This journal is © The Royal Society of Chemistry 2021
Dalton Trans.

View Article Online
Paper
Dalton Transactions
under solvothermal conditions. The resulting compounds
display a trimeric structure linked by four metal ions forming
the structure of POMs with Lewis acid metal centers. Co-POM,
Mn-POM, and Zn-POM show isomorphic structures, in which
the metal ions are tetrahedrally coordinated, while the Cu ions
in Cu-POM exhibit octahedral coordination. Cu-POM was
proved to be an efficient heterogeneous catalyst for the cyano-
silylation reaction under ambient temperature and solvent-free
conditions, and displayed excellent cyclability in the catalytic Fig. 1 Combined polyhedral/ball-and-stick representation of (a) the
asymmetrical unit of Cu-POM, view along the c axis; (b) the flat cluster
view along the a axis, highlighting the bowl-shaped centre and the
process.
hollow (pink ball) in the bowl.
Results and discussion
Synthetic considerations
oanions through three Cu1–O2–Nb1 bridges with the Cu1–O2
bond length of 1.993 Å. Cu1 is located at the C axis of the
whole structure. The remaining three Cu2 connect two of the
polyoxoanions in the structure through Cu2–O7–Nb2 and Cu2–
O8–Nb3, with the bond lengths of Cu2–O7 and Cu2–O8 being
3
All the four compounds were synthesized by a solvothermal
method using a Nb/W mixed-addendum Dawson-type precur-
sor (K
8 2 2 3 2
H[P W15(NbO ) O59]·12H O) and the corresponding
transition metal salts (Cu(NO ) ·3H O, CoCl ·6H O, and
MnCl , Zn(NO ) ·6H O) in a H O/EtOH mixed solvent. Many
2 3 2 2 2
3
2
2
2
2
2.190 Å and 1.963 Å, respectively (Fig. S1†). Both Cu1 and Cu2
exhibit a six-coordinate octahedral configuration (Fig. S1b†).
Alternatively, this novel trimer can be viewed as a flat cluster,
with all the Cu and coordination water molecules of Cu
exposed to the two sides of the flat cluster (Fig. 1b).
factors including solvents, the reaction temperature and time
and pH of the mixed solution have been reported to have
important influence on the synthesis of POM compounds. In
2
8
our case, the proportion of the solvents (VH O : VEtOH = 2 : 1) is
2
Co-POM, Mn-POM and Zn-POM are isostructural, but their
asymmetrical structure characteristics are different from those
crucial for the production of the title compounds. Higher pro-
portion of ethanol (e.g. VH O : VEtOH = 1 : 1 or 1 : 2) can only
2
2
+
2+
2+
of Cu-POM: all the Co , Mn and Zn ions in these com-
pounds adopt tetrahedral coordination. Taking Zn-POM as an
example (Fig. 2a and Fig. S4†), each polyanion contains three
result in the formation of an unidentifiable precipitate.
For the synthesis of Cu-POM, Co-POM and Mn-POM, formic
acid is essential. No expected product can be obtained when
acetic acid or hydrochloric acid is used. However, acetic acid is
important for the synthesis of Zn-POM, whose yield is poor
when acetic acid is replaced by formic acid. The four com-
pounds can only be obtained with a given amount of the acid
2
+
2+
{
P W Nb O }, three [Zn(H O) ] and one [Zn(H O)] . Both
2 15 3 62 2 2 2
Zn1 and Zn2 exhibit a four-coordinate tetrahedral configur-
ation (Fig. S4b†).
In the centre of all the four compounds, three {Nb } clus-
3
ters and four TM ions are linked alternately forming a bowl
(2.5 mL for Cu-POM, 7 mL for Co-POM, 4.5 mL for Mn-POM
(
Fig. 1b and 2b). There is a hollow in the bowl with a diameter
of about 9 Å, in the centre of which a water molecule is locked
Fig. S2†). As shown in Table S2,† bond valence sum (BVS) ana-
and 5 mL for Zn-POM). Although formic acid and acetic acid
do not appear in the final structure of the title compounds
(
(except for Mn-POM), they play important roles in the for-
lyses reveal that the bond valences for all the terminal O atoms
of the TM sites are in the range of 0.283 to 0.472, indicating
mation of the four compounds. Firstly, the pH of the solution
is a key factor for the synthesis of POMs. The specific acidic
environment produced by a certain amount of an acid is
necessary for the syntheses of the reported TM-POMs with
different TM ions. Secondly, formic acid and acetic acid may
combine with TM ions in the reaction solutions. So, the
amount/concentration and type of acid are related to the
coordination equilibrium, which may affect the reaction of TM
ions with POMs and affect the final formation of the
TM-POMs.
10
that all of them exist in the form of coordination water, and
the BVS value of all the other O atoms in the POM skeleton is
−2. BVS analyses for the other elements in these compounds
Structural description
Single-crystal X-ray diffraction analysis (Table S1†) indicates
that all the four compounds crystallize in trigonal symmetry,
P- ˉ3 space group. They exhibit similar structures with the only
difference in the coordination of the TM ions. As shown in
Fig. 1a and Fig. S1–S3,† the asymmetrical unit of Cu-POM con-
2
+
tains three {P
2
W
15Nb
3
O
62}, three [Cu(H
2
O)
4
]
and one [Cu
Fig. 2 Combined polyhedral/ball-and-stick representation of (a) the
2
+
(
H O) ] to form a trimer, in which Cu1 connects three polyox- asymmetrical unit of Zn-POM; (b) the hollow (pink ball) in the bowl.
2
3
Dalton Trans.
This journal is © The Royal Society of Chemistry 2021

View Article Online
Dalton Transactions
Paper
3
5,36
indicated the following oxidation states: W(VI), Nb(V), P(V), Cu and promote cyanosilylation.
The open coordination
(
II), Co(II), Mn(II), and Zn(II) (Table S3†).
environment of the TM and the labile coordination water in
the four title compounds may afford Lewis acid active sites.
2 3
Besides, {P W15Nb O62} possesses bare nucleophilic surfaces
X-ray photoelectron spectroscopy (XPS)
The oxidation states of the TM ions (Cu , Co , Mn , and
Zn ) in the title compounds were further confirmed by XPS
spectroscopy. The peaks at 952.8 eV and 933.1 eV for Cu-POM
as a result of external oxygen atoms, which can act as a Lewis
base. Based on the synergy between them, we tested the
activity of the four compounds as heterogeneous catalysts in
the cyanosilylation reaction under solvent-free conditions at
room temperature.
Optimization of the catalyst. The cyanosilylation of benz-
aldehyde was chosen as a model reaction to evaluate
different catalysts and optimize the conditions. First, we
investigated the catalytic activity of the four compounds in
the reaction with 1 mol% of catalysts. The yield of 2-phenyl-
2
+
2+
2+
2
+
2
+
2+
can be assigned to Cu 2p1/2 and Cu 2p3/2, respectively
2
9
(
Fig. 3a). The peaks at 797.5 eV and 781.2 eV for Co-POM rep-
resent Co 2p1/2 and Co 2p3/2, respectively (Fig. 3b). As
shown in Fig. 3c, two Mn 2p photoelectron peaks occurring at
2
+
2+
30
6
54.6 eV and 641.9 eV correspond to the characteristic peak
2
+
positions of Mn . The representative peaks of the Zn 2p spec-
trum at 1045.2 eV and 1022.1 eV correspond to Zn 2p1/2 and
Zn 2p3/2, respectively (Fig. 3d). The oxidation states of these
metal ions were fully consistent with the BVS analysis results
2
+
2
-((trimethylsilyl)oxy)acetonitrile reached 91.7% after 2.5 h
2
+
31
when Cu-POM was used as the catalyst, while the yields with
the other three compounds were less than 80% for the same
reaction time (Table 1, entries 1–4). The conversion curves of
the four compounds also indicated that Cu-POM possesses
(Table S3†). The binding energies of the transition elements in
Co-POM, Mn-POM and Zn-POM are slightly higher than the
binding energies of those in their corresponding oxides, which
may be related to the coordination environment and the sur-
rounding charge density of the metal ions in these com-
pounds. Generally, metal ions will have less stability in tetra-
Table 1 Optimization of the parameters of the cyanosilylation reaction
a
hedral positions which will result in higher values of binding of benzaldehyde and TMSCN
3
2,33
energy.
Besides, the coordination of these TM ions with
high-negative POMs may decrease the electron density around
3
4
them, which will also result in their higher binding energies.
Catalytic activities
b
Entry
Catalyst (mol%)
Time (h)
Yield (%)
The cyanosilylation of carbonyl compounds is an important
reaction in organic synthesis for producing cyanohydrin
derivatives, which have been widely utilized as important syn-
thetic intermediates for organic compounds. Lewis acid cata-
lysts can act as electrophilic catalysts to activate carbonyl com-
pounds. Several nucleophilic catalysts, such as amines, phos-
phines, and alkaline earth metal oxides, can activate TMSCN
1
2
3
4
5
6
7
8
9
Cu-POM
Co-POM
Mn-POM
Zn-POM
Cu-POM (unactivated)
Cu-POM (0.3)
Cu-POM (0.5)
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
91.7
78.9
72.5
61.3
51.2
50.5
98.0
18.0
1.02
39.2
{P
Cu(NO
{P
2
W
15Nb
3
}
3
)
2
·3H
2
O
10
2
W15Nb
3
}/Cu
a
Reaction conditions: 0.5 mmol of aldehydes, 1.5 mmol of TMSCN,
.0 mol% of catalyst, without solvent, room temperature (25 °C), under
2
. Yields were determined by H NMR.
1
N
b
1
Fig. 3 XPS spectra of Cu 2p (a), Co 2p (b), Mn 2p (c) and Zn 2p (d) in the
title compounds.
Fig. 4 Conversion curve of the cyanosilylation reaction of benz-
aldehyde with Cu-POM (0.5 mol%) as the catalyst.
This journal is © The Royal Society of Chemistry 2021
Dalton Trans.

View Article Online
Paper
Dalton Transactions
superior catalytic activity to the other three compounds in
Generally, the reaction activity is positively correlated with
cyanosilylation (Fig. S8†). Without activation, Cu-POM the catalyst dosage; a higher dosage is beneficial for the con-
3
7
can catalyze the reaction with a low yield (51.2%, Table 1, versions. However, in this work, with the increasing amount
entry 5), which suggests that the activation of the catalyst is of the catalyst (from 0.5 mol% to 1 mol%), the yield decreased
conducive to the catalytic reaction probably owing to the from 98.0% to 91.7% (Table 1, entries 1 and 7). Increasing the
exposure of unsaturated coordination active sites after being catalyst loading does not provide any substantial benefits to
heated.
the reaction efficiency obviously. A similar phenomenon has
3
8
been reported by the Wei group. The catalytic activities of
the precursors {P } and Cu(NO ·3H O are far lower
than that of Cu-POM. Obviously, the catalytic activity of the
{P W Nb }/Cu mixture is better than that of any single con-
2
W
15Nb
3
3
)
2
2
a
Table 2 Cyanosilylation of various carbonyl compounds with TMSCN
2
15
3
stituent, indicating that there would be a synergy between
3
7
them (Table 1, entries 8–10). Conversion of cyanohydrin tri-
methylsilyl ether vs. reaction time catalyzed by Cu-POM
(
0.5 mol%) was investigated due to the good catalytic perform-
b
Entry
1
Substrate
Product
Yield (%) ance. As shown in Fig. 4, the conversion of benzaldehyde
increased significantly within 2 h (92.2%) and varied from
98.0
92.2% to 99.9% in the following 1 h, demonstrating that the
reaction was almost completed after two hours.
2
3
4
5
6
99.9
99.8
99.7
93.4
86.9
Scope of the substrate. The cyanosilylation of different alde-
hydes/ketones with TMSCN catalyzed by Cu-POM was further
studied. As shown in Table 2, when the substrate is 4-fluoro-
benzaldehyde, 4-nitrobenzaldehyde or 4-cyanobenzaldehyde,
the yields are over 99% (Table 2, entries 2–4). For substrates
like 4-methylbenzaldehyde and 4-methoxybenzaldehyde, the
resulting yields are relatively low (Table 2, entries 8 and 9).
This indicates that the nature of the substituent on the aro-
matic ring may dramatically affect the reaction yields. The
activity of substrates with electron-withdrawing substituents is
higher than the activity of those with electron-donating substi-
tuents, resulting from an increase of the substrate electrophili-
c
3
9,40
city in the former case.
an influence on the yields, para-substituent > meta-substituent
ortho-substituent, obviously (Table 2, entries 5–7). A low yield
54.0%) is observed when 1-naphthaldehyde is used as the
In addition, steric hindrance has
>
(
7
72.4
substrate which has larger steric hindrance (Table 2, entry 10).
The activity of ketones is much lower with final yields of less
than 1% (Table 2, entries 11 and 12).
Recyclability and stability. The recyclability of Cu-POM as a
catalyst was investigated. After the catalytic reaction, the cata-
lyst was separated and reused for the next round. It could be
used for five cycles with no significant decrease in the conver-
c
8
9
87.8
79.3
1
0
54.0
1
1
1
2
Trace
Trace
a
Reaction conditions: 0.5 mmol of aldehydes, 1.5 mmol of TMSCN,
.5 mol% of catalyst, without solvent, room temperature (25 °C), under
2
for 2.5 h. Yields were determined by H NMR. Isolated yields.
0
N
b
1
c
Entries 5 and 8 were selected for purification to obtain pure products:
after the reaction, the mixture was purified by column chromatography
Fig. 5 (a) Recyclability of Cu-POM as the catalyst for the cyanosilylation
over silica gel (100–200 mesh) using an ethyl acetate/petroleum ether of benzaldehyde. (b) Powder XRD patterns of the simulated (black), as-
4
1
(1 : 10) mixture as an eluent to obtain pure products.
synthesized (red), dehydrated (blue) and recovered (pink) Cu-POM.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2021

View Article Online
Dalton Transactions
Paper
sions (Fig. 5a). Meanwhile, the PXRD patterns (Fig. 5b) and
the IR spectra (Fig. S9†) of the recovered Cu-POM remained
unchanged, which proved that the polyoxoanion of Cu-POM is
stable and the crystal lattice is mainly retained after catalysis.
5 J. M. Clemente-Juan, E. Coronado and A. Gaita-Ariño,
Chem. Soc. Rev., 2012, 41, 7464–7478.
6 J. Jiang, Y. Chen, L. Liu, L. Chen and J. Zhao, Inorg. Chem.,
2019, 58, 15853–15863.
7
S.-Y. Wu, Y.-J. Wang, J.-X. Jing, X.-X. Li, Y.-Q. Sun and
S.-T. Zheng, Inorg. Chem. Front., 2020, 7, 498–504.
8
Y. Chen, Z.-W. Guo, Y.-P. Chen, Z.-Y. Zhuang, G.-Q. Wang,
X.-X. Li, S.-T. Zheng and G.-Y. Yang, Inorg. Chem. Front.,
Conclusions
In conclusion, we have successfully synthesized four POM
trimers from Nb/W mixed-addendum POMs and TM ions
2
021, 8, 1303–1311.
9
A. Sartorel, M. Bonchio, S. Campagna and F. Scandola,
Chem. Soc. Rev., 2013, 42, 2262–2280.
0 J. Jia, Y. Niu, P. Zhang, D. Zhang, P. Ma, C. Zhang, J. Niu
and J. Wang, Inorg. Chem., 2017, 56, 10131–10134.
1 Y.-S. Ding, H.-Y. Wang and Y. Ding, Dalton Trans., 2020, 49,
3
2 L.-H. Bi, G. Al-Kadamany, E. V. Chubarova, M. H. Dickman,
L. Chen, D. S. Gopala, R. M. Richards, B. Keita, L. Nadjo,
H. Jaensch, G. Mathys and U. Kortz, Inorg. Chem., 2009, 48,
2
+
2+
2+
2+
(
Cu , Co , Mn , and Zn ) under solvothermal conditions.
They were composed of three {P } units and four [M
H O) ] groups resulting in trimeric aggregates. The catalytic
2
W15Nb
3
1
1
1
2
+
(
2
x
investigation revealed that Cu-POM showed higher efficiency
compared to Co-POM, Mn-POM and Zn-POM. Cu-POM can be
reused for five cycles without significant reduction in its cata-
lytic activity. These results exemplify the potential of using
mixed-addendum POMs and transition metals to form the
structures of POMs with Lewis acid metal centers which
further enhance their catalytic activity.
457–3462.
1
0068–10077.
1
1
1
1
1
1
1
2
3 S.-X. Guo, C.-Y. Lee, J. Zhang, A. M. Bond, Y. V. Geletii and
C. L. Hill, Inorg. Chem., 2014, 53, 7561–7570.
4 X. Xin, N. Hu, Y. Ma, Y. Wang, L. Hou, H. Zhang and
Z. Han, Dalton Trans., 2020, 49, 4570–4577.
5 A. Proust, R. Thouvenot and P. Gouzerh, Chem. Commun.,
Author contributions
W. Xiao and Y. Zhao co-worked on the synthesis and character-
ization of the title compounds. W. Xiao and Y. Ma performed
the catalytic experiments. S. Li and J. Zhang collected the
structural data and provided detailed refinements on the
crystal structures. S. Li and X. Chen conceived the project and
designed the experiments. All authors co-wrote the
manuscript.
2
008, 1837–1852.
6 D.-L. Long, E. Burkholder and L. Cronin, Chem. Soc. Rev.,
007, 36, 105–121.
2
7 S. Shigeta, S. Mori, T. Yamase, N. Yamamoto and
N. Yamamoto, Biomed. Pharmacother., 2006, 60, 211–219.
8 X.-X. Li, W.-H. Fang, J.-W. Zhao and G.-Y. Yang, Chem. –
Eur. J., 2014, 20, 17324–17332.
9 T. J. R. Weakley, H. T. Evans, J. S. Showell, G. F. Tourné and
C. M. Tourné, J. Chem. Soc., Chem. Commun., 1973, 139–140.
0 J. D. Compain, P. Mialane, A. Dolbecq, I. M. Mbomekalle,
J. Marrot, F. Secheresse, E. Riviere, G. Rogez and
W. Wernsdorfer, Angew. Chem., Int. Ed., 2009, 48, 3077–
Conflicts of interest
There are no conflicts to declare.
3081.
2
2
2
2
2
1 S.-J. Li, S.-X. Liu, N.-N. Ma, Y.-Q. Qiu, J. Miao, C.-C. Li,
Q. Tang and L. Xu, CrystEngComm, 2012, 14, 1397–1404.
2 M. Pohl, D. K. Lyon, N. Mizuno, K. Nomiya and
R. G. Finke, Inorg. Chem., 1995, 34, 1413–1429.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (U1804253), the Natural Science
Foundation of Henan Province (202300410246) and the breed-
ing programs of Henan Normal University (2019PL06).
3 N. Mizuno, D. K. Lyon and R. G. Finke, J. Catal., 1991, 128,
84–91.
4 H. Weiner, A. Trovarelli and R. G. Finke, J. Mol. Catal. A:
Chem., 2003, 191, 253–279.
5 S. Li, Y. Zhou, Q. Peng, R. Wang, X. Feng, S. Liu, X. Ma,
N. Ma, J. Zhang, Y. Chang, Z. Zheng and X. Chen, Inorg.
Chem., 2018, 57, 6624–6631.
Notes and references
1
2
3
S.-T. Zheng and G.-Y. Yang, Chem. Soc. Rev., 2012, 41, 7623–
646.
O. Oms, A. Dolbecq and P. Mialane, Chem. Soc. Rev., 2012,
1, 7497–7536.
M. Ibrahim, Y. Xiang, B. S. Bassil, Y. Lan, A. K. Powell, P. de
7
26 S. Li, Y. Zhou, N. Ma, J. Zhang, Z. Zheng, C. Streb and
X. Chen, Angew. Chem., Int. Ed., 2020, 59, 8537–8540.
27 S. Li, Y. Zhao, H. Qi, Y. Zhou, S. Liu, X. Ma, J. Zhang and
X. Chen, Chem. Commun., 2019, 55, 2525–2528.
4
Oliveira, B. Keita and U. Kortz, Inorg. Chem., 2013, 52, 28 J.-P. Cao, Y.-S. Xue, Z.-B. Hu, X.-M. Luo, C.-H. Cui, Y. Song
399–8408. and Y. Xu, Inorg. Chem., 2019, 58, 2645–2651.
U. Kortz, A. Müller, J. van Slageren, J. Schnack, N. S. Dalal 29 D. P. Shoemaker, J. Li and R. Seshadri, J. Am. Chem. Soc.,
and M. Dressel, Coord. Chem. Rev., 2009, 253, 2315–2327. 2009, 131, 11450–11457.
8
4
This journal is © The Royal Society of Chemistry 2021
Dalton Trans.

View Article Online
Paper
Dalton Transactions
3
3
3
3
0 J. Wang, P. Ma and J. Niu, Sci. China, Ser. B: Chem., 2007, 36 H. An, J. Zhang, S. Chang, Y. Hou and Q. Zhu, Inorg.
0, 784–789. Chem., 2020, 59, 10578–10590.
1 T. Liu, J. Liu, Q. Liu, D. Song, H. Zhang, H. Zhang and 37 D. Li, Q. Xu, Y. Li, Y. Qiu, P. Ma, J. Niu and J. Wang, Inorg.
J. Wang, Nanoscale, 2015, 7, 19714–19721. Chem., 2019, 58, 4945–4953.
2 C. Elmi, S. Guggenheim and R. Gieré, Clays Clay Miner., 38 D. Dan, F. Chen, W. Zhao, H. Yu, S. Han and Y. Wei, Dalton
016, 64, 537–551. Trans., 2021, 50, 90–94.
3 P. N. Lisboa-Filho, C. Vila, M. S. Góes, C. Morilla-Santos, 39 A. G. Mahmoud, K. T. Mahmudov, M. F. C. Guedes da Silva
5
2
L. Gama, E. Longo, W. H. Schreiner and C. O. Paiva-Santos,
and A. J. L. Pombeiro, RSC Adv., 2016, 6, 54263–
Mater. Chem. Phys., 2004, 85, 377–382.
54269.
3
4 S.-R. Ye, Y.-K. Shan and L.-Y. Dai, J. Coord. Chem., 2006, 57, 40 J.-Z. Gu, S.-M. Wan, M. V. Kirillova and A. M. Kirillov,
45–155. Dalton Trans., 2020, 49, 7197–7209.
5 Y. Kikukawa, K. Suzuki, M. Sugawa, T. Hirano, K. Kamata, 41 W. Wang, M. Luo, W. Yao, M. Ma, S. A. Pullarkat, L. Xu and
1
3
K. Yamaguchi and N. Mizuno, Angew. Chem., Int. Ed., 2012,
1, 3686–3690.
P.-H. Leung, ACS Sustainable Chem. Eng., 2019, 7, 1718–
1722.
5
Dalton Trans.
This journal is © The Royal Society of Chemistry 2021