Hybrid dimers based on metal-substituted Keggin polyoxometalates (metal = Ti, Ln) for cyanosilylation catalysis

Article abstract of DOI:10.1039/C8DT00389K

Six novel organic-inorganic hybrid polyoxometalate derivatives, K[(H₂O)₄(3-Hpic)₂Ce][(H₂O)₅(3-Hpic)₂Ce][PW₁₀Ti₂O₄₀]·11H₂O 1, K[(H₂O)

Full text of DOI:10.1039/C8DT00389K

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: H. An, Y. Zhang, Y.
Hou, T. Hu, W. Yang, S. Chang and J. Zhang, Dalton Trans., 2018, DOI: 10.1039/C8DT00389K.
Volume 45 Number
1
7
January 2016 Pages 1–398
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Dalton
Transactions
An international journal of inorganic chemistry
www.rsc.org/dalton
Accepted Manuscripts are published online shortly after
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

Page 1 of 12
Pleas eD ad l ot o nn oT tr aa nd sj au cs tt i omn as rgins
View Article Online
DOI: 10.1039/C8DT00389K
Journal Name
ARTICLE
Hybrid dimers based on metal-substituted Keggin
polyoxometalates (metal = Ti, Ln) for cyanosilylation catalysis
Haiyan An,* Yumeng Zhang, Yujiao Hou, Tao Hu, Wei Yang, Shenzhen Chang, Jianjun Zhang
Received 00th January 20xx,
Accepted 00th January 20xx
Six
novel
organic–inorganic
(3-Hpic) Ce][PW10Ti
(3-Hpic) Nd][PW10Ti
(3-Hpic) Sm][PW10Ti
39]·14.5H O 4, H[(H
(4-Hpic)Nd][(4-Hpic) NdPW11 39]·10H
-picolinic acid) have been synthesized and characterized by elemental analysis, IR, solid state UV-vis
hybrid
40]·11H
40]·12H
40]∙8H
polyoxometalate
derivatives,
DOI: 10.1039/x0xx00000x
K[(H
K[(H
K[(H
H[(H
2
O)
O)
O)
O)
4
4
4
7
(3-Hpic)
(3-Hpic)
(3-Hpic)
2
2
2
Ce][(H
Nd][(H
Sm][(H
2
O)
O)
O)
5
2
2
O
2
O
2
O
O
O)
1,
2,
3,
www.rsc.org/
2
2
2
2
5
2
2
O
2
5
2
2
O
2
(4-Hpic)La][(4-Hpic)
O)
2
LaPW11
O
2
2
7 2 2
(4-Hpic)Ce][(4-Hpic) CePW11O39]∙7.5H O
O 6, (3-Hpic = 3-picolinic acid; 4-Hpic =
5
4
, K(4-Hpic)0.5[(H
2
6
2
O
2
spectroscopy, thermal gravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction.
Isostructural compounds 1–3 are hybrid dimers that consist of two Ti-substituted Keggin-type polyoxoanions
2
PW10Ti O
40]7- and four Ln-3-Hpic coordination groups. The strong hydrogen bonds in 1–3 can make these
[
dimers yield a 1D supramolecular chain. Compounds 4–6 are also dimers constructed from two
lanthanide-substituted Keggin-type polyoxoanions [PW11LnO39]4- and four 4-Hpic ligands, which are further
linked by two Ln-4-Hpic groups to form a bi-supporting structure. Then these subunits are joined together by
strong hydrogen-bonding interactions between polyoxoanions and coordinated water molecules to produce a
2
D supramolecular framework. All these compounds as heterogeneous Lewis acid-base catalysts show high
activity and high selectivity for the cyanosilylation of different carbonyl compounds in solvent-free condition,
and can be recycled without any obvious inactivation.
Introduction
catalyzing the cyanosilylation reactions of ketones and
aldehydes.20-21 Cyanosilylation reaction of aldehydes and ketones is
Polyoxometalates (POMs) are transition metal oxide clusters with
Mo, W, V, Nb and Ta in their highest oxidation state.1-6 The
assembly of lacunary POM clusters with transition metal (TM) or
lanthanide (Ln) cations produces a family of metal-substituted
POMs, which not only possess diverse structures, but also have
significant applications in catalysis, magnetism, luminescence or
medicine.7-15 In particular, catalysis materials of metal-substituted
POMs have attracted increasing interest, which can catalyze many
reactions including the light-driven water oxidation, the epoxidation
of various olefins, the oxidation of sulfides, the hydrolysis of
phosphoesters and the degradation of organic dyes etc..16-19 In 2012,
Mizuno and coworkers firstly found that Ln-substituted di-lacunary
of importance in organic synthesis, because this reaction creates
cyanohydrins that are key starting materials in fine chemical and
drugs, however, there are very few examples of POMs as catalysts
for cyanosilylation reaction up to now. In 2014, Niu and coworkers
38]8- and
reported a novel hybrid species based on lacunary [H
Cu-organic
2 11
W O
fragments,
[
2 2 2 2 11 2 3
Cu (bpy)(H O)5.5] [H W O38]·3H O·0.5CH CN, which showed
good performance in cyanosilylation reactions as heterogeneous
catalyst.22 After that, Sun’s group prepared a hybrid assembly
containing {P
5
W30} anion and Cu-organic coordination units,
{
[Cu12(pbtz) (Hpbtz)
2
2
(OH) (H O)16] [Na(H O)P 110]}·16H O,
4
2
2
5
W
30
O
2
which displayed prominent catalytic performance in the
cyanosilylation reaction of aldehydes.23 Recently, our group reported
Keggin
POMs
[{Y(H
2
O)
2
}
2
(γ-SiW10
O
36
)
2
]10-
and
[
{Ln(H
2
O)
2
(acetone)}
2
(γ-SiW10O )
36 2
]10- (Ln = Y , Nd , Eu , Gd ,
3+
3+
3+
3+
38]6- polyanion with
several compounds based on [Co
lanthanide cations or alkaline earth metal cations as linkers, those are
2 4
Mo10H O
Tb3+ or Dy ) are the homogeneous catalysts for high-efficiently
3+
[
(C
(
Ln(H
2
O)
5
][Ln(H
2
O)
O) ][Co
O) ][Co
7
][Co
2
Mo10
Mo10
Mo10
H
4
O
38]·6H
38]∙2H
38]∙3H
2
O
2
O,
O
(Ln
=
Sm, Eu)
and
College of Chemistry, Dalian University of Technology, Dalian 116023, P. R. China.
Email:anhy@dlut.edu.cn; Fax:+86-411-84657675; Tel:+86-411-84657675
Electronic Supplementary Information (ESI) Polyhedral representation of the
2
N
2
H
10
)
2
[Sr(H
2
5
2
H
4
O
C
2
N
2
H
10
)
2
[Ba(H
2
3
2
H
4
O
2
which
as
coordination modes of Ce cations in
La cations in ; IR, TG curves and PXRD patterns for 1–6; UV-vis spectra for
plots of cyanohydrin yield vs. time for the cyanosilylation reaction of
benzaldehyde with TMSCN with compounds 1–6; IR spectra for as-synthesized and
recovered catalyst and are available; IR spectra of , benzaldehyde and
obtained after the absorption of benzaldehyde are available. Study on recycling of
catalyst and is listed in Table S1. CCDC 1818604 1818609.
1
; EDS spectra for 1–3; coordination modes of
heterogeneous catalysts exhibit excellent catalytic activity under
solvent-free conditions for the cyanosilylation reactions.24-25
Considering the research status of POM-based catalysts, the
exploration of new hybrid materials based on metal-substituted
POMs and lanthanide-organic linkers, which efficiently
4
2
and
6;
1
5
1
1
1
3
–
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Pleas eD ad l ot o nn oT tr aa nd sj au cs tt i omn as rgins
Page 2 of 12
Journal Name
ARTICLE
heterogeneously prompt the cyanosilylation of carbonyl compounds, from 5 to 50°. TG analyses were carried out on aViPewerAkritincl-eEOlmnlineer
DOI: 10.1039/C8DT00389-K1
is of great importance, but faces challenge.
When selected as the substituted metal centers, the Ti(IV) ion is in flowing N
TGA7 instrument from 30 to 900°C at a heating rate of 10°C·min
2
. UV-vis spectra were obtained on an Analytic Jenina
an active candidate, because not only the similar ionic radius of SPECORD S600 spectrophotometer at room temperature. The GC
Ti(IV) with W(VI) implies it fits well into the vacant site of POMs, analyses were performed on Techcomp GC-7900 with a flame
but also it can be an active site as organic reaction catalyst in both ionization detector (FID) equipped with a SE-54 (internal diameter =
homogeneous and heterogeneous systems such as oxidation 0.32 mm, length = 30 m).
reactions.26-28 So far, only a few dimeric, trimeric and tetrameric
Experimental Measurements
Synthesis
inorganic structures based on Ti-substituted POMs have been
reported through intermolecular Ti-O-Ti bonds, except for mono-,
di-, and tri-substituted monomers.29-30 The examples of introducing
other metal-organic coordination groups into Ti-substituted POMs to
construct new hybrid materials, have never been known, although
they may possess significant catalysis applications. On the other
hand, lanthanide-substituted POMs have always been the research
of
2 4 2 2 5 2 2 2
K[(H O) (3-Hpic) Ce][(H O) (3-Hpic) Ce][PW10Ti O40]·11H O
(1)
K
7
PW10Ti
2
O
40·6H
2
O (0.1493 g, 0.05 mmol) was dissolved in 10
mL deionized water at 50°C. Then, 10 mL aqueous solution of
Ce(NO ·6H O (0.0434 g, 0.1 mmol) and 3-pic (0.0246 g, 0.2
3
)
3
2
focus, originating from their magnetic properties, photoluminescent
and their strong Lewis acids for activation of substrates.31-34 Many
mmol) was added dropwise. After stirring 1 h, the pH value of the
mixing solution was adjusted to 3.20. Next, the solution was
refluxed for 1 h at 80°C. Finally, the resulting solution was filtered
and left to evaporate at room temperature. The pale-yellow crystals
were obtained after three weeks. Yield: 42% (based on
charming hybrid structures based on Ln-substituted POMs have been
successfully obtained by Pope, Wang, Su, Niu, Zhao et al.,35-38
36]8- polyoxoanions were
however, only Ln-substituted [SiW10O
investigated as the catalyst for cyanosilylation reactions by Mizuno's
group. Thus, it is quite appealing to combine Ti-substituted or
Ln-substituted polyoxotungstates with lanthanide-organic fragments
to make new hybrid materials featuring the functions of
high-effectively catalyzing the cyanosilylation reaction.
K
1
7
PW10Ti
2
O
40·6H
2
O). Anal. Calcd (%) for 1: C, 7.62; H, 1.59; N,
.48; K, 1.03; P, 0. 82; W, 48.66; Ti, 2.53; Ce, 7.42. Found: C, 7.40;
H, 1.67; N, 1.35; K, 1.10; P, 0.73; W, 48.57; Ti, 2.58; Ce, 7.52. IR
-
1
data (KBr, cm ): 3366(s), 1643(s), 1592(m), 1461(w), 1401(s),
1103(w), 1062(s), 955(s), 878(m), 794(vs), 747(s), 672(m), 615(m)
and 505(m).
40]7-- and [PW11LnO39]4- as the
Fortunately, with [PW10Ti
building block, we successfully obtained six hybrid compounds,
2
O
Synthesis
K[(H O)
2)
Compound 2 was synthesized in a way similar to that described
for 1, except that Nd(NO ·6H O (0.0438 g, 0.1 mmol) was used
instead of Ce(NO ·6H O. Light purple crystals were isolated from
the filtrate. Yield: 34% (based on K O). Anal. Calcd
%) for 2: C, 7.57; H, 1.63; N, 1.47; K, 1.03; P, 0.81; W, 48.32; Ti,
2.52; Nd, 7.58. Found: C, 7.43; H, 1.78; N, 1.36; K, 1.11; P, 0.89;
of
K[(H
K[(H
K[(H
H[(H
H[(H
2
2
2
2
2
O)
O)
O)
O)
O)
4
4
4
7
7
(3-Hpic)
(3-Hpic)
(3-Hpic)
2
2
2
Ce][(H
Nd][(H
Sm][(H
2
O)
O)
O)
5
(3-Hpic)
(3-Hpic)
(3-Hpic)
2
Ce][PW10Ti
Nd][PW10Ti
Sm][PW10Ti
39]·14.5H
39]∙7.5H
(4-Hpic)Nd][(4-Hpic) NdPW11
2
O
40]·11H
40]·12H
40]∙8H
2
O
1,
2
4 2 2 5 2 2 2
(3-Hpic) Nd][(H O) (3-Hpic) Nd][PW10Ti O40]·12H O
2
5
2
2
O
2
O 2,
(
2
5
2
2
O
2
O
3,
4,
5,
6,
(4-Hpic)La][(4-Hpic)
(4-Hpic)Ce][(4-Hpic)
O)
2
LaPW11
O
O
2
O
3
)
3
2
2
CePW11
2
O
3
)
3
2
K(4-Hpic)0.5[(H
2
6
2
O39]·10H
2
O
7
2 2
PW10Ti O40·6H
(3-Hpic = 3-picolinic acid; 4-Hpic = 4-picolinic acid). Compounds
(
1
–3 are isostructural, and display a dimer composed of two
40]7- anions and four Ln-3-Hpic units. Also, compounds
[PW10Ti O
2
-
1
–6 are dimers constructed from two [PW11LnO39]4- linked by
-Hpic ligands, which are further supported by two Ln-4-Hpic units.
W, 48.50; Ti, 2.59; Nd, 7.47. IR data (KBr, cm ): 3345(s), 1642(s),
4
4
1
7
593(m), 1461(w), 1402(s), 1095(w), 1061(s), 955(s), 879(m),
93(vs), 745(s), 673(m), 611(m) and 503(m).
Interestingly, all six compounds act as Lewis acid-base catalysts of
great efficiency in the cyanosilylation of carbonyl compounds under
solvent-free conditions, which can be recycled without any obvious
loss of activity.
Synthesis
K[(H O)
3)
Compound 3 was synthesized in a way similar to that described
for 1, except that SmCl ·6H O (0.0365 g, 0.1 mmol) was used
instead of Ce(NO ·6H O. Pale-yellow crystals were collected.
Yield: 38% (based on K O). Anal. Calcd (%) for 3:
C, 7.69; H, 1.44; N, 1.50; K, 1.04; P, 0.83; W, 49.09; Ti, 2.56; Sm,
of
2
4 2 2 5 2 2 2
(3-Hpic) Sm][(H O) (3-Hpic) Sm][PW10Ti O40]∙8H O
(
3
2
Experimental section
3
)
3
2
Materials and methods
7 2 2
PW10Ti O40·6H
7 2 2 3 2
The raw materials K PW10Ti O40·6H O and H PW12O40·6H O
8
.03. Found: C, 7.57; H, 1.51; N, 1.39; K, 0.95; P, 0.86; W, 49.17;
were synthesized following the literature methods39-40 and confirmed
by IR spectra. Other laboratory chemicals were reagent grade,
commercially purchased and used without further purification. The
C, H and N elemental analyses were performed on a Perkin-Elmer
-1
Ti, 2.60; Sm, 7.92. IR data (KBr, cm ): 3353(s), 1643(s), 1594(m),
1
7
Synthesis
H[(H O) (4-Hpic)La][(4-Hpic)
O (0.299 g, 0.1 mmol) was dissolved in 10 mL
deionized water. Then, Li CO (0.0295 g, 0.4 mmol) was added to
the solution. The initial pH value of the mixture was about 6.80 and
459(w), 1402(s), 1178(w), 1062(s), 955(s), 879(m), 794(vs),
46(s), 673(m), 620(m) and 510(m).
of
2
400 CHN elemental analyzer. IR spectra were recorded on an
2
7
2 2
LaPW11O39]·14.5H O (4)
Alpha Centaur FT/IR Spectrophotometer with KBr pellets over the
range 400–4000 cm-1 region. PXRD patterns of the samples were
recorded on a Rigaku Dmax 2000 X-ray diffractometer with graphite
monochromatized Cu-Kα radiation (λ = 0.154 nm) and 2θ varying
3 2
H PW12O40·6H
2
3
adjusted to about 4.80 with HNO
3
. Next, 10 mL aqueous solution of
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 2
Please do not adjust margins

Page 3 of 12
Pleas eD ad l ot o nn oT tr aa nd sj au cs tt i omn as rgins
Journal Name
ARTICLE
La(NO ·6H
3
)
3
2
O (0.0866 g, 0.2 mmol) and 4-Hpic (0.0492 g, 0.4 “DFIX” were used in the refinements. The crystallogVriaepwhAircticdleaOtanlionef
mmol) was added dropwise. Under stirring, the pH value of the final 1–6 are provided in Table 1. Selected bondDOleI:n1g0th.1s03a9n/dC8aDnTg0l0es38f9oKr
mixing solution was adjusted close to 3.20 using KOH. Finally, the compound 1 and 4 are listed in Table 2. The crystallographic data of
suspension was refluxed for 1 h at 80°C in the thermostatic water 1–6 have been deposited in the Cambridge Crystallographic Data
bath and filtrated. The colorless crystals were collected several days Centre with CCDC reference number: 1818604 for 1, 1818605 for 2,
from the filtrate at room temperature. Yield: 29% (based on 1818606 for 3, 1818607 for 4, 1818608 for 5, 1818609 for 6.
H
3
PW12
O40·6H
2
O). Anal. Calcd (%) for 4: C, 5.82; H, 1.59; N, 1.13;
General procedure for cyanosilylation reactions
P, 0.83; W, 54.46; La, 7.48. Found: C, 5.53; H, 1.38; N, 1.31; P,
-
1
1
1
8
.02; W, 54.77; La, 7.5. Selected IR (KBr, cm ): 3353(s), 1633(s),
591(m), 1408(s), 1374(m), 1238(w), 1089(m), 1045(s), 949(vs),
86(s), 836(vs), 794(s), 763(s), 719(m), 595(w) and 512(w).
A typical procedure for the cyanosilylation reaction of aldehydes
is as follows: 2 mol% catalyst 1–6 was added to a mixture of
substrates (0.5 mmol) and trimethylsilyl cyanide (TMSCN) (1.5
mmol) without any solvent. Then, the reaction mixture was stirred at
Synthesis of H[(H
5)
The preparation of 5 was similar to that of 4 except that
2 7 2 2
O) (4-Hpic)Ce][(4-Hpic) CePW11O39]∙7.5H O
(
3
2
23K under a N atmosphere and the conversion to product was
monitored by GC analysis. After the reaction was completed, the
catalyst was removed by filtration and centrifugation of the reaction
mixture. All products (cyanohydrin trimethylsilyl ethers) were
confirmed by a comparison of their GC retention times, GC-MS
spectra with those of authentic data.
Ce(NO
3
)
3
·6H
·6H
based on H
2
O (0.0868 g, 0.2 mmol) was used instead of
O. Orange yellow crystals were obtained. Yield: 41%
La(NO
3
)
3
2
(
3
PW12
O40·6H
2
O). Anal. Calcd (%) for 5: C, 6.02; H,
1
.25; N, 1.17; P, 0.86; W, 56.35; Ce, 7.81. Found: C, 6.18; H, 0.99;
-
1
N, 0.93; P, 1.05; W, 56.64; Ce, 7.64. Selected IR (KBr, cm ):
3
1
350(s), 1633(s), 1596(m), 1408(s), 1374(m), 1245(w), 1089(m),
046(s), 949(vs), 889(s), 835(vs), 794(s), 763(s), 713(m), 601(w)
Results and discussion
and 505(w).
Synthesis
Synthesis
of
2 6 2 2
K(4-Hpic)0.5[(H O) (4-Hpic)Nd][(4-Hpic) NdPW11O39]·10H O
In this work, we have attempted to introduce Ti and Ln ions to the
lacunary POM clusters to build novel organic-inorganic hybrid
compounds through the conventional aqueous solution method.
(
6)
The preparation of 6 was similar to that of 4 except that
Nd(NO ·6H O (0.0876 g, 0.2 mmol) was used instead of
La(NO ·6H O. Light purple crystals were isolated. Yield: 36%
based on H O). Anal. Calcd (%) for 6: C, 6.77; H,
.33; N, 1.32; K, 1.05; P, 0.83; W, 54.30; Nd, 7.75. Found: C, 6.45;
3
)
3
2
40]7- anions,
Dimers 1–3 were obtained by the reactions of [PW10Ti O
2
3
)
3
2
Ln3+ (Ce , Nd , Sm ) and 3-Hpic, and the synthetic methods of
3+
3+
3+
(
1
3 2
PW12O40·6H
these
[PW10Ti
The effects of metal cations on the formation of compounds have
isostructural
compounds
are
the
same
7-
3+
(
2
O40] /Ln /3-Hpic = 1:2:4, temperature and heating time).
H, 1.07; N, 1.12; K, 0.76; P, 1.12; W, 54.56; Nd, 7.94. Selected IR
-
1
(
KBr, cm ): 3352(s), 1637(s), 1586(m), 1403(s), 1374(m), 1245(w),
3+
3+
been investigated in detail. Other Ln cations except for Ce , Nd ,
Sm3+ cations were tried to be introduced to the reaction system.
1
5
090(m), 1047(s), 949(vs), 890(s), 835(vs), 794(s), 764(s), 718(m),
92(w) and 515(w).
When La3+ cation was used, similar species to compounds 1–3 can
be found, however, its crystal data cannot be collected owing to the
poor crystal quality. When other Ln3+ cations after Sm3+ in the
X-Ray crystallography
periodic table of the elements react with K
7 2
PW10Ti O40 and 3-pic,
The crystallographic data for compounds 1–6 were determined
using a Bruker Smart CCD diffractometer with Mo Kα radiation (λ =
only some bulk crystal of K 40 was obtained. The
7
2
PW10Ti O
aforementioned facts suggest that the lanthanide cations play a key
role in the construction of hybrid compounds, and the radius of Ln
0
.71073 Å) by ω and θ scan modes. All of the structures were solved
using the SHELXL-2014 software by the full-matrix least squares on
F2. In compounds 1–6, except for partial crystal water molecules, all
non-hydrogen atoms were refined anisotropically. In compounds 1–
3
+
cations is a non-negligible factor. If the Ln ion was replaced by
2
+
2+
2+
2+
transition metal cations (such as Mn , Co , Ni , Zn ions and so
on) under the similar conditions, we only obtained the crystals of
3
, two W sites (W5, W6) are site occupancy disordered. W(5) site is
K
7
PW10Ti
2
O
40. Then, the effects of organic ligands on the structures
were investigated by replacing 3-Hpic with other N-donor ligands
such as imidazole, 2-nitroimidazole, 1,2,4-triazole, benzimidazole)
occupied by W and Ti atom with occupancy factors of 0.75 and 0.25
for 1, 0.78 and 0.22 for 2, 0.8 and 0.2 for 3. W(6) site is occupied by
W and Ti atom with occupancy factors of 0.25 and 0.75 for 1, 0.22
and 0.78 for 2, 0.2 and 0.8 for 3. So, the composition of the
(
under similar conditions. Unfortunately, we only got the raw
materials. Although 4-Hpic was tried to be used in the reaction
system, some amorphous precipitates were isolated. The results
indicate that organic ligand is an important factor to control the final
product.
7
-
2
polyoxoanion is [PW10Ti O40] . In compound 6, the disordered Nd
center is occupied by Nd2 and Nd2A with the site occupancies of 0.5
and 0.5. In 1–3, site occupancies of the partial water molecules of
solvation were set to be less than 1, owing to disorder; in 4–6
Compounds 4–6 were synthesized by the self-assembly of
“squeeze” command was used to deal with the water molecules of
7
-
3+
monolacunary Keggin-type polyanion [PW11
O39] , Ln cations (La ,
solvation. For compounds 1–6, the highest residual peaks are close
to lanthanide cations and partial W atoms mainly due to the series
termination errors. Furthermore, in order to obtain reasonable atom
sites and thermal parameters, other restraints such as “ISOR” or
Ce3+ and Nd ) and organic ligands 4-Hpic under the similar reaction
3+
8-
conditions. The [PW11
was all freshly prepared by adjustment of the pH value of solution of
40]3- through the addition of Li
CO . In the meantime, we
O39] used in the syntheses of compounds 4–6
[PW12
O
2
3
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Pleas eD ad l ot o nn oT tr aa nd sj au cs tt i omn as rgins
Page 4 of 12
Journal Name
ARTICLE
attempted to directly use [PW11O39] taking place of [PW12O
40]3- as 2.367(1) Å]. The average Ce–O bond length is 2.485 ÅVieiwn A1r.ticEleaOchnlionef
7
-
DOI: 10.1039/C8DT00389K
the original material, but no crystals could be obtained. So far, we two crystallographically independent 3-Hpic molecules, as
a
7-
haven’t found suitable conditions to prepare 4–6 with [PW11
precursor. Although, 3-Hpic was tried to replace 4-Hpic, no crystals 3-Hpic group by utilizing its carboxyl oxygen atom. Two unique
can be got. Similar to compounds 1–3, metal cations and organic Ce–3-Hpic fragments are linked to one [PW10Ti
40]7 unit to form a
ligands play very important roles in forming species 4–6. mononuclear cluster (Fig. 2a). Then two clusters are joined together
The effects of pH values, ratio of the raw materials and into a dimer by Ce1–O4–Ti2/W6 and Ce2–O11–W5/Ti1 bonds,
temperature were investigated by large quantities of parallel related by an inversion center. The dimer based on [PW10Ti
O39] as monodentate ligand coordinates to one Ce(III) cation to form a Ce–
2
O
2
O
40]7-
experiments. We found that the pH values between 3.00 and 3.50 and Ln–organic coordination complexes, has never been seen in the
were optimal to the synthesis process. The crystals weren’t obtained literatures (Fig. 2b). Moreover, theses dimers are joined up together
at higher pH or lower pH. All six compounds could be well prepared to yield a 1D supramolecular chain by the strong hydrogen-bonding
3
+
3+
by the 1:2:4 POM/Ln /ligand ratio. When the POM/Ln /ligand interactions between oxygen atoms from 3-Hpic molecules and
ratio was at 1:2:2, no crystals were separated. At a higher ratio coordinated water molecules with length of 2.642 and 2.702 Å (Fig.
(
1:2:8), a few deteriorated crystals were isolated with low yields. 2c).
Apart from these, reaction temperatures also can’t be ignored in the
The bond valence sums (BVS)45 calculated based on the observed
synthesis of these compounds. we can find out that the optimal bond lengths in compounds 1–3, indicate that the oxidation states of
reaction temperature is about 80°C. There were no crystals in the W, P, Ti and Ce/Nd/Sm atoms in 1–3 are +6, +5, +4 and +3,
solution at lower temperature, such as room temperature. When the respectively. Energy dispersive X-ray spectroscopy (EDS) on
temperature was raised to 100°C or more, few crystals were obtained compounds 1–3 showed that the presence of W, Ti, and Ln (Ce, Nd,
with poor quality.
Sm), and a nearly 5:1:1 ratio of W: Ti: Ln (see Fig. S2, S3, S4),
which are consistent with the single crystal X-ray analyses.
Crystal structures of 1-3
Single crystal X-ray diffraction analyses reveal that the structures
of compounds 1–3 are essentially isomorphous and all crystallize in
the monoclinic space group C2/m. Herein, we take compound 1 for
example to discuss the crystal structure in detail. The asymmetric
2
unit of 1 is constructed from half one [PW10Ti O
40]7- polyoxoanion,
two crystallographically unique Ce(III) cations, two 3-Hpic ligands
+
40]7- subunit is formed by
and one K cation (Fig. 1a). The [PW10Ti
2
O
the incorporation of two titanium ions into the vacant Keggin-type
POM. It should be noted that in [PW10Ti
40]7- polyoxoanion, two Fig. 1 (a) ORTEP drawing of compound 1 with thermal ellipsoids at 50%
2
O
W sites (W5, W6) are site occupancy disordered by W and Ti atom probability. (b) ORTEP drawing of compound 4 with thermal ellipsoids at
with occupancy factors of 0.75/0.25 and 0.25/0.75. This kind of 50% probability. (color code: P, yellow; W, lavender; WTi, pink; La, green;
disorder has been found in other metal-substituted POMs.41-44 Ce, turquoise; K, brown; O, red; N, blue; C, black).
According to the different environment of the oxygen coordination,
we can divide the oxygen atoms into four kinds: central oxygen Oa,
double-bridging oxygen Ob, terminal oxygen Ot and terminal
oxygen linked to Ce3+ Ot′. Thus, the W-O distances can be grouped
into four different groups W–Oa 2.375(9)–2.473(10) Å, W-Ob
1
.851(9)–2.009(9) Å, W–Ot 1.688(10)–1.710(9) Å, W–Ot′ 1.698(10)
and 1.711(10) Å in 1. The central P-O distance is from 1.525(9) to
.545(9) Å. The Ti-O distance is in the range of 1.924(10)–1.985(9)
1
Å, which is similar to that in the literatures.
There are two crystallographically unique Ce(III) cations in the
complex unit, and the coordinated modes of the crystallographically
independent Ce3+ cations in 1 are shown in Fig. S1. The
nine-coordinated Ce(1) forms
coordination environment, defined by five water molecules [Ce–OW
.484(1)–2.643(1) Å], two terminal oxygen atoms from two
40]7- polyoxoanions [Ce–O4 2.496(9) Å], and two
carboxyl oxygen atoms from two 3-Hpic molecules [Ce–O21
.468(1) Å]. Ce(2) has a distorted monocapped square antiprismatic
coordination environment, bonded to four water molecules [Ce–OW
.18(3)–2.475(1) Å], two terminal oxygen atoms from two
40]7- polyoxoanions [Ce–O11 2.563(1) Å], and two
a
tricapped trigonal prism
2
Fig. 2 (a) Ball-stick and polyhedral representation of mononuclear cluster for
. (b) Ball-stick and polyhedral representation of dimeric polyanion for 1. (c)
2
[PW10Ti O
1
View of the 1D chain in 1 showing the hydrogen-bonding interactions
between the coordinated water molecules and nitrogen atom from one 3-Hpic
molecule. Free water molecules and K atoms are omitted for clarity. (color
code: P, yellow; W, lavender; WTi, pink; Ce, turquiose; O, red; N, blue; C,
black).
2
2
2
[PW10Ti O
carboxyl oxygen atoms from two 3-Hpic molecules [Ce–O23
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 4
Please do not adjust margins

Page 5 of 12
Pleas eD ad l ot o nn oT tr aa nd sj au cs tt i omn as rgins
Journal Name
Table 1 Crystal data and structure refinement for 1–6.
ARTICLE
View Article Online
DOI: 10.1039/C8DT00389K
Complex
Formula
1
2
3
4
5
6
KH60
C
24PTi
2
W
10
KH62
C
24PTi
W
2 10
KH54
C
24PTi
2
W
1
H
59
C
18PW11La
2
H
45
C
18PW11Ce
2
KH49.5C21PW11Nd
2
Ce
2
N
4
O
68
Nd
N O
2 4 69
0
Sm N O
2 4 65
N
3
O
66.5
N
3
O
59.5
3.5 62
N O
Formula weight
T (K)
3777.21
200(2)
3803.53
293(2)
3743.78
296(2)
3712.71
293(2)
3589.13
200(2)
3723.93
293(2)
Crystal system
Space group
a (Å)
Monoclinic
C2/m
Monoclinic
C2/m
Monoclinic
C2/m
Triclinic
P-1
Triclinic
P-1
Triclinic
P-1
21.8889(3)
30.2502(5)
15.2713(4)
90
21.916(13)
30.097(19)
15.243(9)
90
21.889(4)
30.183(6)
15.327(3)
90
13.0114(5)
14.3598(6)
21.4373(8)
96.428(2)
91.620(2)
95.623(2)
3957.9(3)
2
13.0263(13)
14.3304(14)
21.410(2)
96.253(2)
91.877(2)
95.276(2)
3952.4(7)
2
13.0716(6)
14.3465(7)
21.2358(11)
84.449(3)
89.313(3)
84.531(3)
3945.7(3)
2
b (Å)
c (Å)
α (°)
β (°)
133.3600(10)
90
133.528(7)
90
133.421(2)
90
γ (°)
3
U (Å )
7351.8(3)
4
7290(8)
4
7355(3)
4
Z
-
1
μ (mm )
17.192
14132
17.516
18523
17.539
19022
17.094
17.176
17.428
Reflections
collected
27811
20170
37497
Independent
reflections
R (int)
6159
6503
6577
13825
13625
13851
0.0316
1.024
0.1022
1.002
0.0867
1.020
0.0564
1.057
0.0264
1.020
0.0813
1.098
2
GOF on F
a
R
1
[I > 2σ(I)]
0.0458
0.1281
0.0522
0.0540
0.1297
0.0729
0.1419
0.0573
0.1450
0.0719
0.1564
0.0550
0.1414
0.0715
0.1497
0.0451
0.1204
0.0588
0.1265
0.0808
0.2179
0.1144
0.2449
b
wR
(all data)
wR (all data)
2
[I > 2σ(I)]
R
1
2
0.1332
aR1 = ∑||F
b
2-F
2)2]/∑[w(F
2 2 1/2
0
|-|F
C
||/∑|F
0
|; wR2 = ∑[w(F
0
C
0
) ]
Crystal structures of 4-6
Compounds 4–6 are all built on monovacant Keggin
ligands to construct a dimer. Other two La(2)–4-Hpic groups are
covalently linked to the dimer to build the bi-supporting structure
(
Fig. 3b). In the [PW11LaO39]4−, there are three classes of oxygen
7-
39]7- anion can be viewed as
40]3- anion, which
polyoxoanion [PW11
removal of a W–Ot group from the [PW12
consists of a central {PO } tetrahedron surrounded by four
vertex-sharing W 13 trimers. Compounds 4–6 all belong to the
O39] . [PW11O
atoms. The W–O bond lengths are divided into three: W–Oa
O
2
1
.344(10)–2.523(10) Å, W–Ob 1.792(12)–2.085(11) Å, W–Ot
.669(10)–1.738(10) Å in 4.
4
3
O
In the structure, La(1) adopts a distorted monocapped square
triclinic space group P-1, and compounds 4 and 5 are isomorphic
with the unit cell dimensions, volumes, related bond distances and
antiprismatic coordination environment, linked to four oxygen
39]7- anion [La–O 2.482(9)–2.504(9) Å],
atoms from one [PW11
and four carboxyl oxygen atoms from two 4-Hpic acid molecules
La–O 2.474(9)–2.559(9) Å] (Fig. S6). The nine-coordinate La(2)
O
angles only slightly changed. The structure of 6 is similar to 4 and
+
5
, however, 6 contains dissociative 4-Hpic molecule and K . Then,
[
compound 4 is represented here. The asymmetric unit of 4 is
has a tricapped trigonal prism coordination environment, linking to
one terminal oxygen atom from one [PW11LaO39]4- unit [La–O
7-
composed of one monovacant Keggin polyoxoanion [PW11
O39] ,
two La(III) cations and three 4-Hpic ligands (Fig. 1b). The
monovacant [PW11O39] polyoxoanion is coordinated by one La(1)
to form the mono-La-substituted [PW11LaO39]4− (Fig. 3a). Then
two [PW11LaO39]4− units are connected by four bridged 4-Hpic
2
2
.604(1) Å], one carboxyl oxygen atom from one 4-Hpic [La–O
.47(2) Å], and seven water molecules [La–OW 2.42(4)–2.65(3)Å].
7-
The average La–O bond length is 2.509 Å in 4, corresponding to
the literatures.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Pleas eD ad l ot o nn oT tr aa nd sj au cs tt i omn as rgins
Page 6 of 12
Journal Name
ARTICLE
Interestingly, theses dimers are joined up together by the strong
hydrogen-bonding interactions of O38…O3W between terminal
oxygen atoms of polyoxoanions and coordinated water molecules
with length of 2.698 Å, and of O13…N2 between bridging oxygen
atoms and nitrogen atoms from 4-Hpic molecules with length of
structure diversity. Coordinated water moleculesVieawnAdrticsleuOrfnalicnee
DOI: 10.1039/C8DT00389K
oxygen atoms of mono-Ln-substituted POMs can be the proton
acceptors, and combine together with the proton donors to build the
high-dimensional structure. Whereas, in compound 1, there is only
one kind of hydrogen bond between oxygen atom from 3-pic
molecule and coordinated water molecule, which makes the
structure be a 1D supramolecular chain.
The bond valence sums (BVS)45 calculated based on the
observed bond lengths in compounds 4–6, indicate that the
oxidation states of W, P and La/Ce/Nd atoms are +6, +5 and +3,
respectively.
2
.943 Å, to form a 1D supramolecular chain (Fig. 3c). Each chain
is further connected to other two parallel chains by hydrogen bonds
O31…O4W) between water molecules and the terminal oxygen
(
atoms of the polyoxoanions with length of 2.785 Å, to yield a 2D
layer (Fig. 3d). Obviously, the strong hydrogen-bonding
interactions are of significance in stabilizing the 2D framework.
Table 2 Selected bond lengths (Å) and angles (˚) for 1 and 4.
Compound 1a
W(1)-O(9)
1.710(9)
1.706(9)
W(2)-O(10)
W(4)-O(20)
1.898(9)
1.697(9)
2.009(9)
2.367(11)
1.924(10)
109.7(5)
W(3)-O(16)
W(5)-O(11)
Ce(1)-O(21)
O(18)-Ti(2)#1
1.711(10) W(6)-O(15)
2.468(11) Ce(2)-O(23)
1.985(9)
O(13)-Ti(2)#1
O(1)-P(1)-O(2)
O(9)-W(1)-O(3 103.2(4)
Compound 4
W(1)-O(9)
1.930(11) W(2)-O(18)
1.891(12) W(4)-O(32)
1.893(11) W(6)-O(22)
1.937(12) W(8)-O(21)
1.738(10) W(10)-O(6)
1.918(11)
1.912(10)
2.054(10)
1.885(10)
1.697(10)
1.541(11)
109.0(6)
W(3)-O(16)
W(5)-O(26)
W(7)-O(24)
W(9)-O(27)
W(11)-O(14)
1.864(9)
P(1)-O(1)
O(1)-P(1)-O(2) 110.1(5)
O(3)-P(1)-O(4)
a
Symmetry transformations used to generate equivalent atoms: #1 -x, y,
-z+2
FT-IR spectra
The IR spectra of compounds 1–3 have been recorded with KBr
pellets in the range of 4000–400 cm-1 (Fig. S7a–c). In the result of
comparison, IR spectra further confirm the isomorphic structures of
1
–3. Four characteristic bands are attributed to νas(W–Ot), νas(W–
Ob) and νas(W–Oc), which appear at 955, 878 and 795/745 cm−1
for 1, 956, 879 and 793/745 cm−1 for 2, and 955, 879 and 795/745
cm−1 for 3, respectively. Compared with the IR spectrum of the
classical Keggin POM H PW12O40·6H O, the ν(W–Oc) vibrational
3 2
bands in 1–3 split, maybe owing to the distortion of structure and
Fig. 3 (a) Ball-stick and polyhedral representation of mononuclear cluster in
4
. (b) Ball-stick and polyhedral representation of dimeric polyanion for 4.
(c) View of the 1D chain in 4 showing the hydrogen-bonding interactions
among the oxygen atoms of polyoxoanions, coordinated water molecules
and nitrogen atoms from 4-Hpic acid molecules. (d) View of the 2D layer in
the reduction of symmetry. As is shown in Fig. 4a, the low
4
, displaying the 1D chains linked by the hydrogen-bonding interactions
−1
wavenumber domain (ν < 1000 cm ) of 1–3 are similar to the
between water molecules and the terminal oxygen atoms. (color code: P,
yellow; W, lavender; La, green; O, red; N, blue; C, black; hydrogen bond,
blue). Free water molecules are omitted for clarity.
7
-
precursor [PW10Ti
1
1
2
O
40] . The absorption bands at 1643, 1592 and
401 cm−1 in 1, 1642, 1593 and 1401 cm−1 in 2, 1643, 1593 and
402 cm−1 in 3, are due to the asymmetric and symmetric stretching
There exist three types of hydrogen bonds in 4 (O38…O3W,
O13…N2, O31…O4W, O35…O2W). Specifically, as the proton
donors, 4-Hpic ligands on La cations may act as useful parts for the
vibrations of the carboxylate groups of 3-pic molecules.
In the IR spectra of compounds 4–6 (Fig. S7d–f), four
characteristic νas(P–Oa), terminal νas(W–Ot), corner-sharing νas(W–
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 6
Please do not adjust margins

Page 7 of 12
Pleas eD ad l ot o nn oT tr aa nd sj au cs tt i omn as rgins
Journal Name
ARTICLE
Ob) and edge-sharing νas(W–Oc) asymmetrical vibration peaks are
S8a, which is regarded as three-step continuousVieww eAirtgichletOlnolinses
DOI: 10.1039/C8DT00389K
derived from the monolacunary Keggin-type polyanions
process. The first weight loss of 5.27% from 30°C to 180°C, is
7-
[
PW11
O
39] . For example, in compound 4, the characteristic bands
ascribed to the loss of all eleven lattice waters (calculated, 5.24%).
Then, the next weight loss is 3.37% from 180°C to 450°C, because
of the release of all eight coordinated water molecules (calculated,
3.81%). The last weight loss of 13.22% in 450–900°C arises from
the decomposition of 3-pic acid organic molecules and the POM
cluster (calculated, 13.55%). The TG curve of 1 gives a total
weight loss of 21.86%, which is consistent with the calculated
-
1
of νas(P–Oa) are observed at 1089, 1047 cm ; the characteristic
band of νas(W–Ot) is at 949 cm ; the characteristic band of νas(W–
Ob) is at 889 cm and the characteristic bands of νas(W–Oc) are at
8
which shows the peaks of νas(P–Oa) (1082, 1040 cm ), νas(W–Ot)
956 cm ), νas(W–Ob) (895cm ) and νas(W–Oc) (810, 740 cm−1),
-
1
-
1
-
1
7-
33, 763 cm . Compared with the IR spectrum of [PW11O39] ,
-
1
-
1
-1
(
the IR spectra of compounds 4–6 display similar characteristic
value of 22.39%, with the final products K
2 2 3 2 5 3
O, Ce O , P O , WO
7-
patterns of the [PW11
O
39] structure (Fig. 4b). However, the νas(W–
and TiO . The TG curves of compounds 2 and 3 exhibit similar
2
–
1
Ot) vibration peaks for 4–6 have red-shifts of 7 cm compared
weight loss stages to those of compound 1, and the whole weight
loss is 21.79% and 21.10% in agreement with the calculated value
of 22.59% and 20.99% (Fig. S8b and S8c).
The thermogravimetric (TG) curve of 4–6 all exhibit multi-step
2
continuous weight loss steps in an N atmosphere. The TG curve of
4 gives a total weight loss of 20.80%, which dovetails with the
calculated value of 20.62%. The weight loss of 7.0% at 30–350°C
corresponds to the loss of all lattice water (calculated, 7.03%). We
ascribe the weight loss of 3.40% at 350–450°C to the loss of all
coordinated water molecules (calculated, 3.39%). At 450–900°C,
the last weight loss of 10.40% is attributed to the decomposition of
7
-
with [PW11O39] , the possible reason for which may be that the
Ln(III) cations have stronger interactions to the terminal oxygen
atoms of the POMs, reducing the W–Ot bond force constant and
leading to decreasing of the W–Ot vibration frequency. The νas(P–
Oa) and νas(W–Oc–W) vibration frequencies for 4–6 have different
levels of blue-shifts, owing to the lower symmetry of [PW11
O
39]7-
in 4-6 than α-Na O. In addition, the features at 1591
PW11O39·nH
7 2
and 1408 cm−1 in 4, 1596 and 1408 cm−1 in 5, 1602 and 1410 cm−1
in 6, can be regarded as the stretching vibrations of the carboxylate
groups of 4-Hpic molecules.
4
-Hpic acid molecules and the POM cluster (calculated, 10.20%).
The TG curve of compounds 5 and 6 display similar weight loss
stages. In 5, the whole weight loss (18.04%) is in agreement with
the calculated value (17.83%). In 6, the whole weight loss
(19.54%) agrees with the calculated value (19.33%) (Fig. S8d–f).
The PXRD patterns for compounds 1–6 are presented in Fig S9.
The diffraction peaks of both calculated and experimental patterns
match well, which indicates that the phase purities of compounds
1
–6 are good. The similarity of PXRD patterns of 1–3 verifies that
they are isomorphic structure. The PXRD patterns for 4–6 are very
similar, also indicating the three compounds are semblable. These
conclusions of experiments conform to the results of the single
crystal X-ray analysis.
UV-vis spectra
The diffuse reflectivity for solid samples of compounds 1–6 are
shown in Fig. 5, ranging from 200 to 800 nm. On the 200−400 nm
UV region, the plots reveal an intense broad absorption band at
about 252 nm, which is assigned to the pπ–dπ charge-transfer
transitions of the Ob(c) → W bonds. The UV-vis spectra of 2 and 6
are very similar with the same Nd(III) cation (Fig. S10). On the
visible region, four absorption bands centered at 524, 584, 749 and
8
01 nm in 2, and 524, 584, 749 and 801 nm in 6 can be ascribed to
the transitions of 4I9/2 → 4F5/2, I9/2 → 4F3/2, I9/2 → 4I15/2 and 4I9/2
4
4
→
4I13/2 of Nd(III) ion.
Fig. 4 (a) IR spectra for H
middle), and 1 (top). (b) IR spectra for H
α-Na O (middle), and 4 (top).
3
PW12
O
40·6H
2
O (bottom), K
5
PW10Ti
2 2
O40·6H O
(
3
PW12
O40·6H O (bottom),
2
7
PW11O39·nH
2
TG analysis and PXRD characterization
2
Under a N atmosphere, the thermogravimetric (TG) curve of 1–
6
were carried out from 30 to 900°C to examine the thermal
stabilities. The thermogravimetric (TG) curve of 1 is shown in Fig.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Dalton Transactions
Page 8 of 12
the nature of the substituent on the aromatic ring ha
effect on the reaction yield.
Table 3 Cyanosilylation of aldehydes catalyzed by compounds 1–6a.
V
d
iewnoArt
icle Online
dramatic
DOI: 10.1039/C8DT00389K
O
C
Si
2
% Cat., neat
H
+
Si CN
R
CH
3
23K, N
2
CN
R
Compound
Aldehyde
Time(h)
Yield(%)b
1
2
3
4
5
6
4
4
4
4
4
4
99.2
97.1
97.8
66.7
70.4
68.1
O
O
1
5
4
4
97.2
69.5
3
H C
1
5
4
4
98.7
52.4
O
F
O
O
Fig. 5 (a) UV-vis spectra for compounds 1–3. (b) UV-vis spectra for
compounds 4–6.
1
5
4
4
99.0
50.3
H
Cyanosilylation study
1
5
4
4
99.8
92.1
Cyanohydrins are versatile intermediates in the context of organic
synthesis and have a promising prospect for the synthesis of some
drug molecules. The reaction of aldehydes and TMSCN is a
relatively mature method for the preparation of cyanohydrins.
Compared with other various cyanating reagents (HCN, KCN and
O
O
1
5
4
4
22.5
8.7
3
Bu SnCN etc.), TMSCN is one of the most useful and safe cyanating
reagents, which has the advantages of low toxicity, high reaction
activity and chemical selectivity. In the present work, we have tested
the activity of the six compounds 1–6 as heterogeneous catalysts in
the cyanosilylation reaction of aldehyde with TMSCN under
solvent-free conditions.
Initially, the cyanosilylation of benzaldehyde acts as a model
reaction to evaluate the catalytic properties of six compounds 1–6.
The reactions in the presence of these hybrid dimers exhibited high
conversions of aldehydes to cyanohydrin trimethylsilyl ethers,
Blank
4
4
35.8
85.2
O
K
O
5
PW10Ti
2
O
40·3H O
2
O
Na
7
PW11
O
4
65.0
reaching 66.7%–99.2% yields (Table 3). Compound
1 and
3
9
· nH O
2
compound 5 containing Ce3+ cations have higher catalytic activity
than their isostructural compounds. Subsequently, 1 and 5 were
chosen to further study the cyanosilylation reactions of various kinds
a
Reaction conditions: catalyst 1–6 2 mol%, aldehyde 0.5 mmol,
of
aromatic
aldehydes.
With
a
substrate
like
or
2
TMSCN 1.5 mmol, without solvent, temperature (323 K) under N .
b
2
4
-hydroxybenzaldehyde,
-fluorobenzaldehyde, the yield of corresponding product reached to
4-methylbenzaldehyde,
Yields were determined by GC analysis using naphthalene as an
internal standard.
above 90% with catalyst 1. These experimental results indicated that
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 8
Please do not adjust margins

Page 9 of 12
Pleas eD ad l ot o nn oT tr aa nd sj au cs tt i omn as rgins
Journal Name
ARTICLE
3
+
charges was considered as Lewis base. In compounds 4-6, the Ln
View Article Online
DOI: 10.1039/C8DT00389K
cation of [(4-Hpic)
2
LnPW11O
39]4- unit coordinated by four oxygen
atoms from one [PW11O
39]7- anion and four carboxyl oxygen atoms
In stark contrast, introducing the substituent with the large steric
hindrance to the aromatic ring, such as 1-naphthaldehyde, the yield
decreased significantly. The experiment result expresses that under
the same conditions, a substrate with the large steric hindrance is far
more difficult than others in contacting with rare earth metal cations
on the compounds, which can be viewed as Lewis acid. Meanwhile,
the blank experiment for the cyanosilylation of benzaldehyde
without catalyst gave 35.8%. Then, we have also checked the
from two 4-Hpic acids, is difficult to play a role of Lewis acid,
which makes compounds 4-6 have less Lewis acid sites and weaker
Lewis basicity than compounds 1-3, thus lower activity. Some
coordination complexes based on Ti4+ and organic ligands have been
reported as catalysts for the cyanosilylation reaction, in which Ti4+
cation can act as Lewis acid site to activate the aldehydes. A
comparison of the activity of our catalyst 1 with other reported
titanium-based complexes is shown in Table 4. Our compounds 1–3
display more effective for cyanosilylation. These results support the
viewpoint that the catalysis efficiency for the cyanosilylation
reaction can be improved after the synergy between Ti-substituted
a
reactivity of the precursors. α-Na
7 2
PW11O39·nH O gave 65.0% under
4
5 2 2
h and K PW10Ti O40·6H O gave 69.4% under 4 h in the
heterogeneous manner, which are far lower than those of our
heterogeneous catalysts. On account of the synergistic effect of the
Lewis acid (Ln3+ cations) and the Lewis base (POM), compounds 1–
Catalyst
Time(h)/ratio(mol%) Yield (%)
Ref.
1
4/2
99.2
90
This work
6
have better catalytic activity. The plots of yield versus time for the
cyanosilylation reaction of benzaldehyde and TMSCN with different
catalysts are presented in Fig. S11. It can be seen from the figure,
that with the extension of reaction time, obvious increases in yield
were detected in the presence of different catalysts under the same
experimental conditions.
L
L
L
L
L
L
1
2
3
4
5
6
-Ti(Oi-Pr)
-Ti(Oi-Pr)
-Ti(Oi-Pr)
-Ti(Oi-Pr)
4
4
4
4
20/10
46
47
48
49
50
50
51
52
84/20
20/20
16/20
3/1
95
94
98
< 5
98
99
90
It is well known, some metal-containing polyoxotungstates
catalyzing cyanosilylation reaction have been reported previously,
- Ti(Oi-Pr)
4
4
such as TBA
8
H
2
[(SiYW10
[H
(Hpbtz) (OH)
[(SiYW10
yield = 94%) and TBA [Nd (SiW10
0 min, and yield = 97%), our compounds have weaker catalytic
O
36
)
2
], TBA
O·0.5CH
O)16][Na(H O)P
8
H
2
[Nd
2
(SiW10
O
36)2]·7H
2
O,
{
[Cu
2
(bpy)(H
2
O)5.5
]
2
2
W
11
O
38]·3H
2
3
CN}
and
O.
- Ti(Oi-Pr)
24/1
{
[Cu12(pbtz)
2
2
4
(H
2
2
5
W
30
O110]}·16H
2
Compared with TBA
8
H
2
O
36
)
2
] (benzaldehyde, 15 min, and
]·7H O (benzaldehyde,
L7-Ti(Oi-Pr)4
-Ti(Oi-Pr)
4
24/0.2
12/10
8
H
2
2
O
36
)
2
2
L
8
4
effects. These reported homogeneous catalysts are better than
compound 1, which has the best catalytic performance in these
compounds we obtained (benzaldehyde, 4 h, and yield = 99.2%).
However, the biggest disadvantage of homogeneous catalyst is that it
is difficult to recycle. While, our compounds have stronger catalytic
POM and Ln3+ cations.
Table 4 A comparison of catalytic activity of various complexes in
the cyanosilylation reaction of benzaldehydes and TMSCN.
effect
in
[H
comparison
with
CN (benzaldehyde, 24
98.1%) and
a
L
1
:
C
31
H
32
O
4
;
L
2:
44 56 2 2 3 22 23 2 4 20 12 2 5
C H O N ; L : C H O N; L : C H O ; L :
Cu
h,
2
(bpy)(H
and
(Hpbtz)
2
O)5.5
]
2
2
W
11
O
38]·3H
2
O·0.5CH
3
C
37
H
55
O
2
N
3
; L
6
: C37
H
57
O
N
2 3
7
I; L : C74
H
108
N
6
O
6
; L
8
: C18
H
22
O
2
N
2
P.
yield
(OH) (H
=
{
[Cu12(pbtz)
2
2
4
2
O)16][Na(H
2
5 30 2
O)P W O110]}·16H O
To check the recyclability and stability of the catalysts in the
(
benzaldehyde, 24 h, and yield = 61.7%), that are heterogeneous
cyanosilylation reaction, we collected the catalysts recovered from
the completed catalytic reaction by filtration and recycled these
catalysts at least three times with benzaldehyde as the reaction
substrate. The results in detail are shown in Fig. 6. The recovered
catalysts displayed high catalytic performance without a large drop.
catalysts and use solvent conditions.
Furthermore, we can find a remarkable difference in activity
between Ti-substituted polyoxometalate derivatives 1–3 and
Ln-substituted polyoxometalate derivatives 4–6. Compounds 1–3
show better catalytic performance. In compounds 1-3, Ln3+ cations
With
compound
1
as
catalyst,
the
yield
of
as Lewis acid can activate the carbonyl group of aldehyde
compounds and Ti-substituted POM as Lewis base can activate
2
-phenyl-2-trimethylsilyloxyacetonitrile shows just a slight decrease
40]7- of 1–
(from 99.2% to 97.1%) after three times recycling experiments; As
catalyst, compound 5 can be recycled at least three times without an
appreciate decrease in activity (from 70.4% to 68.2%).
TMSCN at the same time. In the polyoxoanion [PW10Ti
, Ti atom (Ti1 or Ti2) and W atom (W5 or W6) occupy one
position by site occupancy disorder, and the terminal oxygen atoms
of {TiO } octahedra are covalently linked by lanthanide-3-Hpic
2
O
3
6
coordination groups, so the whole polyoxoanion with high negative
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Pleas eD ad l ot o nn oT tr aa nd sj au cs tt i omn as rgins
Page 10 of 12
Journal Name
ARTICLE
stability of 1 and 5 during the cyanosilylation reactioVni.ewInArtaicdledOitniolinne,
DOI: 10.1039/C8DT00389K
infrared spectroscopy of the compounds 1 and 5 impregnated with
1
00
cycle 1
cycle 2
cycle 3
9
9.2 98.6
benzaldehyde showed one broad C–O stretch at 1688.43 and
9
7.1
9
8
7
6
5
0
0
0
0
0
−1
1
688.71 cm , respectively. The ν(C–O) stretch showed a red shift of
13.37 and 13.09 cm-1 from 1701.8 cm−1 of the free benzaldehyde
Fig. S14). This phenomenon suggests that the possible activation of
(
the substrate by compounds 1 and 5.
7
0.4 69.4
6
8.2
Conclusions
1
5
In this work, we have successfully synthesized six novel hybrid
dimers 1–6 constructed from metal-substituted Keggin-type
polyoxoanions and lanthanide-organic coordination units under mild
condition. These new POM materials are efficient heterogeneous
Lewis acid-base catalysts for cyanosilylation of various aldehydes
2
Fig. 6 Recycling catalytic experiments with 1 and 5 as heterogeneous under solvent-free conditions. As far as we know, [PW10Ti O
40]7- as
catalysts for cyanosilylation of benzaldehyde under the same condition.
a precursor of compounds 1–3 is firstly used to synthesize
heterogeneous catalysts that show higher efficiency than compounds
–6 for cyanosilylation reaction. This result indicates that the
synergy between Ti-substituted Keggin POM [PW10Ti
4
2
O
40]7- and
Ln3+ cations makes compounds 1–3 show higher catalytic activity. In
consequence, the successful synthesis of these species certainly
stimulates researchers' interest to develop new heterogeneous
catalytic materials containing metal-substituted POMs, especially
titanium-containing POMs.
Acknowledgment
The National Natural Science Foundation of China (21371027,
2
1274015, 20901013), Natural Science Foundation of Liaoning
Province (2015020232) and Fundamental Research Funds for the
Central Universities (DUT15LN18, DUT15LK02) provide financial
supports for this work.
References
1
1
2
A. Müller, F. Peters, M. T. Pope and D. Gatteschi, Chem. Rev.,
998, 98, 239–271.
L. Zhang, W. B. Yang, X. F. Kuang, X. Y. Wu and C. Z. Lu,
Dalton Trans., 2014, 43, 16328–16334.
3
3
4
D. L. Long, E. Burkholder and L. Cronin, Chem. Soc. Rev., 2007,
6, 105–121.
J. W. Zhang, Q. Li, M. Y. Zeng, Y. C. Huang, J. Zhang, J. Hao and
Y. G. Wei, Chem. Commun., 2016, 52, 2378–2381.
Fig. 7 (a) Powder X-ray diffraction (PXRD) patterns of 1. (b) Powder X-ray
diffraction (PXRD) patterns of 5: calculated pattern from crystal data (red
line); experimental pattern before catalysis (black line); recovered catalyst 1
or 5 after 3 catalytic runs of the cyanosilylation of benzaldehyde (blue line).
5
7
6
4
7
Y. F. Song and R. Tsunashima, Chem. Soc. Rev., 2012, 41, 7384–
402.
G. L. Guo, Y. Q. Xu, J. Cao and C. W. Hu, Chem. Commun., 2011,
7, 9411–9413.
X. B. Han, Z. M. Zhang, T. Zhang, Y. G. Li, W. B. Lin, W. S. You,
We also checked the structural integrity of catalysts by FT-IR and Z. M. Su and E. B. Wang, J. Am. Chem. Soc., 2014, 136, 5359–
PXRD analyses of the catalyst before and after the catalytic reaction. 5366.
The PXRD patterns of the retrieved catalysts were identical with 8 Z. Q. Huang, Z. Luo, Y. V. Geletii, J. W. Vickers, Q. S. Yin, D.
those of the fresh catalysts, confirming the structural integrity of 1 Wu, Y. Hou, Y. Ding, J. Song, D. G. Musaev, C. L. Hill and T. Q.
and 5 after the catalytic reaction (Fig. 7). The IR spectra of the Lian, J. Am. Chem. Soc., 2011, 133, 2068–2071.
recovered compounds 1 and 5 were also identical to those of the 9 J. W. Zhao, Y. Z. Li, L. J. Chen and G. Y. Yang, Chem. Commun.,
freshly prepared samples (Fig. S12 and Fig. S13). These 2016, 52, 4418–4445.
experimental results suggested that 1 and 5 are true heterogeneous
catalysts for the cyanosilylation reaction, and verified the excellent
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 10
Please do not adjust margins

Page 11 of 12
Pleas eD ad l ot o nn oT tr aa nd sj au cs tt i omn as rgins
Journal Name
ARTICLE
1
0 M. Ibrahim, Y. H. Lan, B. S. Bassil, Y. X. Xiang, A. Suchopar, A. 35 M. Zimmermann, N. Belai, R. J. Butcher, M. TV.iePwoAprteic,leEO.nliVne.
K. Powell and U. Kortz, Angew. Chem. Int. Ed., 2011, 50, 4708– Chubarova, M. H. Dickman and U. Kortz, DInOoIr:g10. .C10h3e9m/C.,8D20T00073, 8496K,
4
1
711.
1737–1740.
1 X. Zhang, Z. H. Yi, L. Y. Zhao, Q. Chen, X. M. Gu, J. Q. Xu, X. 36 X. L. Wang, Y. Q. Guo, Y. G. Li, E. B. Wang, C. W. Hu and N.
L. Wang, C. Yang, X. Z. Xu and W. J. Xia, Dalton Trans., 2009, H. Hu, Inorg. Chem., 2003, 42, 4135–4140.
9
1
198–9206.
2 X. L. Wang, X. J. Liu, A. X. Tian, J. Ying, H. Y. Lin, G. C. Liu Shao, Z. M. Su and E. B. Wang, Dalton Trans., 2015, 44, 11290–
11293.
3 W. M. Gao, T. Yu, L. X. Wu and L. H. Bi, Chem. Commun., 38 J. W. Zhao, D. Y. Shi, L. J. Chen, Y. Z. Li, P. T. Ma, J. P. Wang
016, 52, 10403–10406. and J. Y. Niu, Dalton Trans., 2012, 41, 10740–10751.
4 J. T. Rhule, C. L. Hill and D. A. Judd, Chem. Rev., 1998, 98, 39 W. H. Knoth, P. J. Domaille and D. C. Roe, Inorg. Chem., 1983,
27–357. 22, 198.
5 T. Zhang, D. Y. Fu, Y. Q. Wu, Y. Z. Wang and L. X. Wu, Dalton 40 C. R. Deltcheff, M. Fournier, R. Franck and R. Thouvenot, Inorg.
Chem., 1983, 22, 207.
6 X. B. Han, Y. G. Li, Z. M. Zhang, H. Q. Tan and E. Bo. Wang, J. 41 S. M. Liu, Y. W. Liu, S. P. Jiang, S. X. Liu, D. F. He, N. Li, J.
37 W. C. Chen, C. Qin, X. L. Wang, Y. G. Li, H. Y. Zang, K. Z.
and Q. Gao, Dalton Trans., 2012, 41, 9587–9589.
1
2
1
3
1
Trans., 2016, 45, 15457–15463.
1
Am. Chem. Soc., 2015, 137, 5486–5493.
Miao and J. H. Ye, Journal of Environmental Chemical Engineering.,
1
7 S. L. Zhu, X. Xu, S. Ou, M. Zhao, W. L. He and C. D. Wu, Inorg. 2016, 4, 908–914.
Chem., 2016, 55, 7295–7300.
42 Z. W. Weng, Y. H. Ren, M. Gu, B. Yue and H. Y. He, Dalton
1
8 T. K. N. Luong, P. Shestakova, T. T. Mihaylov, G. Absillis, K. Trans., 2018, 47, 233–239.
Pierloot and T. N. P. Vogt, Chem. Eur. J., 2015, 21, 4428–4439.
43 T. M. Anderson, M. A. Rodriguez, T. A. Stewart, J. N. Bixler, W.
1
9 J. Tucher, Y. L. Wu, L. C. Nye, I. I. Burmazovic, M. M. Q. Xu, J. B. Parise and M. Nyman, Eur. J. Inorg. Chem., 2008,
Khusniyarov and C. Streb, Dalton Trans., 2012, 41, 9938–9943.
3286–3294.
2
0 Y. Kikukawa, K. Suzuki, M. Sugawa, T. Hirano, K. Kamata, K. 44 T. Z. Zhang, S. Yao, Z. M. Zhang, Y. Lu, Y. G. Li and E. B.
Yamaguchi and N. Mizuno, Angew. Chem. Int. Ed., 2012, 51, 3686– Wang, ChemPlusChem., 2014, 79, 1153–1158.
3
2
690.
1 K. Suzuki, M. Sugawa, Y. Kikukawa, K. Kamata, K. Yamaguchi B. I. D. Brown and D. Altermatt, Acta Cryst.,1985, B41, 244–247.
46 S. S. Kim, J. M. Kwak and G. Rajagopal, Bull. Korean Chem.
2 Q. X. Han, X. P. Sun, J. Li, P. T. Ma and J. Y. Niu, Inorg. Chem., Soc., 2006, 27, 10.
014, 53, 6107–6112.
47 F. X. Chen, X. M. Feng, B. Qin, G. L. Zhang and Y. Z. Jiang,
3 T. P. Hu, Y. Q. Zhao, Z. Jagličić, K. Yu, X. P. Wang and D. Sun, Org. Lett., 2003, 5, 949–952.
48 Y. Li, B. He, B. Qin, X. M. Feng and G. L. Zhang, J. Org. Chem.,
4 H. Y. An, L. Wang, Y. Hu and F. Fei, CrystEngComm., 2015, 17, 2004, 69, 7910–7913.
531–1540. 49 M. Mori, H. Imma and T. Nakai, Tetrahedron Lett., 1997, 38,
5 Y. J. Hou, H. Y. An, B. J. Ding and Y. Q. Li, Dalton Trans., 6229–6232.
45 B. I. D. Brown and K. K. Wu, Acta Cryst., 1976, B32, 1957–1959;
and N. Mizuno, Inorg. Chem., 2012, 51, 6953–6961.
2
2
2
CrystEngComm., 2015, 54, 7415–7423.
2
1
2
2
2
017, 46, 8439–8450.
50 Y. Q. Wen, W. M. Ren and X. B. Lu, Org. Biomol. Chem., 2011,
6 K. Y. Wang, Z. G. Lin, B. S. Bassil, X. L. Xing, A. Haider, B. 9, 6323–6330.
Keita, G. J. Zhang, C. Silverstru and U. Kortz, Inorg. Chem., 2015, 51 C. W. Lv, D. Q. Xu, S. F. Wang, C. X. Miao, C. G. Xia and W.
5
2
4, 10530–10532.
7 L. Hua, Y. X. Qian, Y. Y. Yu, W. W. Zhu, T. Cao, Y. Shi, H, Li, 52 J. M. Brunel, O. Legrand and G. Buono, Tetrahedron:
Asymmetry., 1999, 10, 1979–1984.
Sun, Catalysis Communications., 2011, 12, 1242–1245.
B. Feng and Z. S. Hou, New J. Chem., 2011, 35, 1836–1841.
8 Y. Goto, K. Kamata, K. Yamaguchi, K. Uehara, S. Hikichi and N.
Mizuno, Inorg. Chem., 2006, 45, 2347–2356.
9 O. A. Kholdeeva, G. M. Maksimov, R. I. Maksimovskaya, L. A.
2
2
Kovaleva, M. A. Fedotov, V. A. Grigoriev and C. L. Hill, Inorg.
Chem., 2000, 39, 3828–3837.
3
0 S. Yoshida, H. Murakami, Y. Sakai and K. Nomiya, Dalton
Trans., 2008, 4630–4638.
1 B. Nohra, P. Mialane, A. Dolbecq, E. Rivière, J. Marrot and F.
Sécheressea, Chem. Commun., 2009, 2703–2705.
2 P. Mialane, L. Lisnard, A. Mallard, J. Marrot, E. A. Fidancev, P.
Aschehoug, D. Vivien and F. Sécheresse, Inorganic Chemistry.,
3
3
2
3
003, 42, 2102–2108.
3 P. T. Ma, F. Hu, R. Wan, Y. Huo, D. D. Zhang, J. Y. Niu and J. P.
Wang, J. Mater. Chem. C., 2016, 4, 5424–5433.
4 K. Wang, D. D. Zhang, J. C. Ma, P. T. Ma, J. Y. Niu and J. P.
3
Wang, CrystEngComm., 2012, 14, 3205–3212.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 11
Please do not adjust margins

Dalton Transactions
Page 12 of 12
View Article Online
DOI: 10.1039/C8DT00389K
Table of Contents
Hybrid dimers based on metal-substituted Keggin
polyoxometalates (metal = Ti, Ln) for cyanosilylation
catalysis
Haiyan An,* Yumeng Zhang, Yujiao Hou, Tao Hu, Wei Yang, Shenzhen Chang,
Jianjun Zhang
7
-
4-
Six hybrid dimers 1–6 constructed from [PW10Ti
2
O
40] / [PW11LnO39
]
and
lanthanide-organic units are reported, which as heterogeneous catalysts show high
activity for the cyanosilylation under solvent-free conditions.