Fe2Mn(μ3-O)(COO)6 Cluster Based Stable MOF for Oxidative Coupling of Amines via Heterometallic Synergy

Article abstract of DOI:10.1002/cjoc.202100361

The direct catalytic oxidative coupling of amines is one of the attracting methods for the synthesis of a variety of pharmaceutical or industrial needed imines. Numerous earth-abundant manganese based salts, oxides, and complexes have been applied in this reaction. However, these compounds suffered from difficult separation, large catalyst loading, complicated reactivation or indeterminate activity. Considering the facts that metal-organic frameworks (MOFs) with crystalline structure, precise composition, and enormous surface area have superior performance in heterogeneous catalytic reactions, herein, we introduced Mn into [Fe₃(μ₃-O)(CH₃COO)₆], one of the precursors for the preparation of stable MOFs, and got [Fe₂Mn(μ₃-O)(CH₃COO)₆] cluster. After ligand replacement with biphenyl-3,4’,5-tricarboxylic acid (BPTC), heterometallic cluster-based [Fe₂Mn(μ₃-O)(BPTC)₂(DMF)₂(H₂O)] (1) was obtained. As expected, 1 is stable and able to catalyze the homo- or cross-coupling of amines effectively and selectively with 0.9 mol% catalyst loading at room temperature. Control experiments indicated that the catalytic activity of 1 mainly stems from Mn sites and that Fe synergistically contributes to the stability. Additionally, 1 is recyclable and can be reused easily for at least 8 runs without obvious decrease in catalytic ability. To our knowledge, 1 should be the first heterometallic cluster-based MOF with defined structure suitable for the synthesis of diverse imines from oxidative coupling of amines under mild conditions, which may shed light on the easy preparation of effective heterogeneous catalysts for organic synthesis.

Full text of DOI:10.1002/cjoc.202100361

Fe Mn( -O)(COO) cluster based stable MOF for oxidative
2
3
6
coupling of amines via heterometallic synergy
a
a
a
a
a
,a,b
Ying-Xia Wang, Hui-Min Wang, Pan Meng, Dong-Xia Song, Zhikai Qi and Xian-Ming Zhang*
a
Key Laboratory of Magnetic Molecules and Magnetic Information Materials (Ministry of Education), Institute of Chemistry and Culture,
School of Chemistry and Material Science, Shanxi Normal University, Linfen 041004, China.
College of Chemistry & Chemical Engineering, Key Laboratory of Interface Science and Engineering in Advanced Material, Ministry of
b
Education, Taiyuan University of Technology, No. 79 Yingze West, Taiyuan, 030024, P. R. China.
Keywords
Stable |Metal-Organic Frameworks | Oxidative Coupling | Amines | Heterometallic Synergy
Main observation and conclusion
The direct catalytic oxidative coupling of amines is one of the attracting methods for the synthesis of a variety of pharmaceutical or
industrial needed imines. Numerous earth-abundant manganese based salts, oxides, and complexes have been applied in this
reaction. However, these compounds suffered from difficult separation, large catalyst loading, complicated reactivation or
indeterminate activity. Considering the facts that metal-organic frameworks (MOFs) with crystalline structure, precise composition,
and enormous surface area have superior performance in heterogeneous catalytic reactions, herein, we introduced Mn into
[
Fe ( -O)(CH COO) ], one of the precursors for the preparation of stable MOFs, and got [Fe Mn( -O)(CH COO) ] cluster. After ligand
3
3
3
6
2
3
3
6
replacement with biphenyl-3,4’,5-tricarboxylic acid (BPTC ), heterometallic cluster-based [Fe Mn( -O)(BPTC) (DMF) (H O)] (1) was
2
3
2
2
2
obtained. As expected, 1 is stable and able to catalyze the homo- or cross-coupling of amines effectively and selectively with 0.9 mol%
catalyst loading at room temperature. Control experiments indicated that the catalytic activity of 1 mainly stems from Mn sites and
that Fe synergistically contributes to the stability. Additionally, 1 is recyclable and can be reused easily for at least 8 runs without
obvious decrease in catalytic ability. To our knowledge, 1 should be the first heterometallic cluster-based MOF with defined structure
suitable for the synthesis of diverse imines from oxidative coupling of amines under mild conditions, which may shed light on the easy
preparation of effective heterogeneous catalysts for organic synthesis.
Comprehensive Graphic Content
*E-mail: zhangxm@dns.sxnu.edu.cn
This article has been accepted for publication and undergone full peer review but has not been
through the copyediting, typesetting, pagination and proofreading process which may lead to
differences between this version and the Version of Record. Please cite this article as doi:
10.1002/cjoc.202100361
This article is protected by copyright. All rights reserved.

Report
First author et al.
common solvents and different pH (1-12) aqueous solutions.
Catalytic results indicated that 1 is applicable effectively and
selectively in the oxidative homo- or cross-coupling of aromatic
and aliphatic amines with 0.9 mol% loading at room temperature,
and the highest yield and selectivity is 90% and 99%, respectively.
Additionally, 1 can be recovered easily and reused without any
complicated reactivation for more than 8 runs only with negligible
decrease in catalytic ability. Furtherly, heterometallic synergy
exists in 1, where Mn acts as the main catalytic active site and Fe
synergistically contributes to the robustness, as revealed by
Background and Originality Content
Imines, also known as Schiff bases with chemical active
unsaturated C=N double bonds, have been extensively used as
intermediates for the production of pharmaceuticals,
[
1-2]
agrochemicals, and other heterocyclic chemicals.
The direct
oxidative coupling of the readily available primary amines is
considered as one of the most important methods to synthesize
imines, which is able to efficiently reduce energy consumption
control experiments. To our knowledge,
1 is the first
heterometallic cluster based MOF with defined structure that is
capable of catalyzing the oxidative coupling of diverse amines.
[3-6]
and waste emission.
However, this kind of approach still
possesses some shortcomings, for instance the relative inactivity
of benzylamines with electron-withdrawing groups or aliphatic
amines, the possible generation of unwanted by-products, and
Results and Discussion
[7-8]
the difficulty in synthesizing asymmetrically substituted imines.
To this end, a large number of catalytic systems including noble
Synthesis and characterization of 1
[9-12]
[13-16]
[17-20]
Solvothermal reactions of BPTC with [Fe Mn( -O)(CH COO) ]
metal,
non-noble metal,
and metal free
based
2
3
3
6
in the presence of acetic acid in DMF at 150 °C for 48 h yielded
the red bitruncated octahedron-shaped crystals of 1.
Single-crystal X-ray diffraction analysis reveals that 1 crystallized
catalysts have been established and shown the excellent
conversion and selectivity. Nevertheless, obvious disadvantages,
such as high cost, inefficient time- and energy-consumption,
complex preparation process, and worrisome stability, largely
restrained their wide applications. Therefore, the design of cheap,
efficient, easily prepared, and reusable heterogeneous catalysts
suitable for various amines under mild conditions is highly
desirable.
in the tetragonal space group P4 2 2. The asymmetric unit
3
1
3+
2+
3-
contains one Fe , half a Mn , half a  -O, one BPTC , one
coordinated DMF and half a H O molecule. The Fe is surrounded
by four carboxylate O atoms from four different BPTC , one DMF
O atom, and one  -O, forming a distorted octahedral geometry.
The Mn shows the same coordination geometry with Fe , but
replacing the coordinated DMF with H O (Figure 1a). The
3
3+
2
3-
3
2+
3+
Manganese (Mn) is one of the earth-abundant elements and
is well known for its excellent oxidation ability. Numerous
2
[21-23]
[24]
[25-28]
[
Fe Mn( -O)(COO) ] cluster (Figure 1b) was kept in 1, where six
2 3 6
-
Mn-porphyrins,
MnSO4,
and manganese oxide
have
of the CH COO groups in [Fe Mn( -O)(CH COO) ] were replaced
by the carboxyl groups from BPTC . Each BPTC links three
Fe Mn( -O) building blocks to form a three-dimensional (3D)
been reported for the oxidative coupling of amines. It is
noteworthy that these catalysts suffered from tedious
chromatographic separations, high catalyst loading (e.g. > 25 mg
or 10 mol%), complicated reactivated operations, and/or
indeterminate activity influenced by surface properties.
3
2
3
3
6
3-
3-
2
3
porous framework containing two kinds of 1D channels shaped in
quadrilateral and triangle along a- and b-axis with the size
2
2
approximately in 7.96 × 4.63 Å and 10.44 × 5.09 Å , respectively
Figure 1c). Removing guest molecules, the framework has a free
Comparatively,
heterogeneous
Mn-based
metal-organic
(
frameworks (MOFs) usually possess enormous surface areas and
precise composition, which is helpful to obtain abundant catalytic
void of 30.8%. Topologically, by regarding [Fe Mn( -O)(CH COO) ]
building block and BPTC ligand as 6- and 3-connected nodes,
2
3
3
6
3-
[
29-36]
active sites and reveal the structure-property relationships.
However, partly due to the relatively poor chemical stability,
their applications in oxidative coupling of amines are still under
[
37]
respectively, 1 can be simplified as a binodal (3,6)-connected ttd
11
4
3
[47]
net with the point symbol of (6 8 )(6 ) (Figure 1d).
2
2
+
3+
[
33]
To confirm the coexistence of Mn and Fe in 1, tests of
energy-dispersive X-ray spectroscopy (EDS), inductively coupled
plasma atomic emission spectroscopy (ICP-OES), and X-ray
photoelectron spectroscopy (Figure S17) were performed.
Analysis results indicated that the Mn and Fe distribute uniformly
development.
Previous
studies
have
shown
that
Fe ( -O)-cluster, which is easy to be prepared and convenient to
3
3
be completely or partly replaced of Fe by a specific metal atom
M), could be viewed as one of the most popular secondary
building units (SBUs) to construct chemical stable MOFs with
(
[38-43]
heterometallic synergy.
To this regard, we attempt to
introduce Mn into Fe ( -O) SBU and finally get
3
3
Fe Mn ( -O)-cluster based MOFs with high chemical stability
3-x
x
3
and catalytic activity in oxidative coupling of amines.
Two typical methods have been published to introduce Mn
into MOFs with Fe ( -O) SBU: one is de novo synthesis by mixing
3
3
Fe and Mn salts during synthesis, which gives domain MTV-MOF,
formulated as (Mn1.45Fe1.55O) (TCPP-Ni) , containing
single-component Mn ( -O)(COO) and Fe ( -O)(COO) SBU;
2
3
[44]
3
3
6
3
3
6
-
the other one is ligand substitution of CH COO in the performed
3
[
46, 46]
Fe Mn( -O)(CH COO) ,
which provides well-mixed
2
3
3
6
bimetallic MOFs containing Fe Mn( -O) SBU. Considering the
2
3
facts that the former method usually suffers from the lack of
control over the final metal distribution, and the close position of
M to Fe within the SBU has superior performance to the domain
[44]
arrangement,
herein, we precisely targeted at the synthesis of
Fe Mn( -O)(COO) cluster based stable MOFs and successfully
2
3
6
obtained [Fe Mn( -O)(BPTC) (DMF) (H O)] (1, BPTC
=
2
3
2
2
2
3+
Figure 1 (a) Asymetric unit of 1 and coordination environment of Fe
and Mn ; (b) Fe
two kinds of 1D channel; (d) (3,6)-connected ttd network in 1.
biphenyl-3,4’,5-tricarboxylic
acid)
by
pre-preparing
2+
2 3 6
Mn( -O)(COO) cluster; (c) 3D network of 1 containing
[
Fe Mn( -O)(CH COO) ] and ligand replacing with BPTC. As
2 3 3 6
expected, 1 shows the excellent stability in the most of the
2
www.cjc.wiley-vch.de
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
This article is protected by copyright. All rights reserved.
Chin. J. Chem. 2021, 39, XXX－XXX

Running title
Chin. J. Chem.
within the structure (Figure S3) and the stoichiometry of Fe/Mn is
approximately in 2:1 (Table S3, Table S4, and Table S10),
Table 1 Substrate scope of oxidative homo-coupling of amines
catalyzed by 1
a
[
39]
consistent with the previous reports.
The phase purity of bulk
Entry
Product
Conversion
90%
87%
Selectivity Yield
samples and the repeatability of the synthesis method were
verified by PXRD patterns (Figure S2).
To examine the chemical stability of 1, the obtained samples
were immersed in the different solvents (water, acetone,
methanol (MeOH), dichloromethane (DCM), toluene, acetonitrile
1
1
a
b
1
2
99%
99%
80%
93%
87%
99%
99%
99%
96%
70%
85%
0%
90%
87%
80%
93%
87%
82%
83%
50%
96%
61%
85%
0%
(
MeCN), and tetrahydrofuran (THF)) for 1 week and the aqueous
1
c
solutions with different pH (1-12) for 24 h. As Figure S4 and Figure
S5 showed, the PXRD patterns of recovered kept well with the
as-synthesized, demonstrating the excellent chemical stability of
3
99%
99%
99%
82%
83%
50%
99%
87%
4
1d
1e
1
, which is essential for utilization in heterogeneous catalytic
oxidative coupling of amines.
5
To evaluate the porosity of 1, N2 adsorption-desorption
isotherms were measured at 77K. The obtained result (Figure S7)
of activated sample, first solvent exchanged with acetone for 7
days and then thermal annealing at 120 °C under vacuum for 12 h,
indicated that 1 possesses a Type-I isotherm with the maximum
6
1f
1
g
7
3
-1
adsorption of 358.75 m g and the calculated Langmuir surface
2
-1
area of 1560.30 m g . The Density Functional Theory (DFT) pore
distribution plot (Figure S8) showed that there are two main kinds
of pore in 1, 0.70 and 0.95 nm, which is consistent with the
crystallographic structure determinations. Additionally, 1 was
8
1h
1
1
i
j
9
capable of CO adsorption and the volumetric uptakes were 94.92
2
10
3
-1
3
-1
m g and 125.32 m g at 298 K and 273 K, respectively (Figure
S9).
1k
1a
1
1
99%
0%
Catalytic results of 1 in oxidative coupling of amines
b
1
2
Catalytic homo-coupling of benzylamine under the oxidation
of TBHP was initially employed as the model reaction to explore
the optimized reaction conditions. As shown in Figure 2, Table S5
and Figure S10, when reactions were took place in toluene, DCM,
and MeCN, the selectivities of 1a were up to 99%, but the
conversions of benzylamine were lower than 70%. When the
solvents were changed to MeOH and n-hexane, both the
conversions and selectivities could be improved to > 90%.
Considering the superior selectivity, MeOH was finally selected as
the best solvent for the following investigation. Then, the
concentration of benzylamine for the present reaction was
optimized (Table S5, entries1, 8, 9) and the results indicated that
when 1 mmol of benzylamine was added, the highest yield of 1a
could be achieved. Finally, for the realization of green chemistry,
utilization of more eco-friendly O and H O were also tested,
1
3
1l
12%
99%
12%
a
Reaction condition: amines (1 mmol), TBHP (0.3 mL), 1 (8 mg), MeOH (1
mL), time 12 h. Conversion and selectivity were determined by H NMR
and GC-MS. Reaction condition: same as a, but dibenzylamine was used.
1
b
TBHP (0.3 mL), MeOH (1mL), temperature (r.t.) and time (12 h).
To verify the catalytic active sites and reveal the
heterometallic synergy in 1, a number of control reactions
without any catalyst, with [Fe Mn( -O)(CH COO) ], BPTC, 1-Fe,
MIL-88-Fe, PCN-260-Fe, PCN-250-Fe, and Mn(OAc) were
performed. As evidenced in Table S6 and Figure S11, the
2
3
3
6
[38]
[38]
[38]
2
conversions with 1 (90%), [Fe Mn( -O)(CH COO) ] (99%), and
Mn(OAc) (99%) were much higher than that with 1-Fe (4%),
2
3
3
6
2
2
2
2
unfortunately, only trace amount of benzylamine could be
conversed to 1a. Considering that the main reduction product of
TBHP is tert-butanol, which can be recovered easily and used for
the synthesis of methyl tert-butyl ether, the optimized reaction
conditions was finally set as: benzylamine (1 mmol), 1 (8 mg),
MIL-88-Fe (10%), PCN-260-Fe (9%), PCN-250-Fe (6%), and BPTC
(trace), revealing the fact that the catalytic activity of 1 mainly
stem from the Mn sites and that Fe may synergistically contribute
to the stability. The higher selectivity under the catalysis of 1 (99%)
than Fe Mn precursor (73%) and Mn(OAc) (32%) could be
2
2
rationalized by the effective transportation and attachment of
amines to in-situ formed aldehydes in the confined space of 1.
Compared to previous reported Mn based homogeneous catalysts
[22, 23, 32]
and Mn/Co-MOF (Table S7),
1 maintain the excellent
catalytic ability of Mn and is the first heterometallic cluster based
MOF with defined structure for the oxidative coupling of amines.
To demonstrate the general applicability of 1, various
aromatic or aliphatic primary amines and secondary amines were
examined under the optimized conditions. As Table 1 showed, a
variety of substituted benzylamines containing electron-donating
or electron-withdrawing groups could be converted successfully
to their corresponding imines with acceptable conversions and
selectivities (entries 1-8). Further analysis revealed that the
electron-withdrawing substituents (entries 6-8) may decrease the
reaction rate and that the steric hindrance (entries 3-5) has a
negligible influence on the reaction outcomes. It should be noted
that the heterocyclic 2-thiophenemethylamine (entry 9), which
Figure 2 Optimization of reaction conditions: benzylamine (1 mmol),
oxidant (0.3 mL) or with a O
2
balloon, 1 (8 mg), solvent (1 mL), 12h. Blue:
conversion of benzylamine; Red: selectivity of 1a, determined by GC-MS.
Chin. J. Chem. 2021, 39, XXX－XXX
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
www.cjc.wiley-vch.de
3
This article is protected by copyright. All rights reserved.

Report
First author et al.
Table 2 Oxidative cross-coupling of substituted benzylamines with
a
aniline catalyzed by 1 .
Entry
Product
Conversion
100%
Selectivity
62%
2
2
a
b
1
2
3
4
5
6
100%
71%
Figure 3 A plausible reaction mechanism.
2
c
100%
61%
exhibited a pseudo-first-order rate dependence with respect to
amines (Figure S15) and that one can establish a linear
relationship between log(k /k ) and Brown-Okamoto constant
2d
100%
56%
x
H
+
[48]
2
2
e
f
( ) (Figure S16). The negative slope of the nearly linear plot in
Hammett plot suggested that a positively charged intermediate
may be generated during the process. We tried to trap this
intermediate by adding 2,2,6,6-tetramethylpiperidinooxy (TEMPO)
into the reaction system (Scheme S1), but no obvious difference
in the reaction conversion was detected, which may be because
TEMPO (4.2×4.4×6.9 Å, calculated based on the MM2 energy
minimization mode of the Chem3D program followed by
measuring the longest atom-to-atom separations in three
dimensions) was not effectively transported into the mesoporous
network of 1 to capture the intermediates.
100%
47%
100%
54%
a
Reaction condition: substituted benzylamines (1 mmol), aniline (5 mmol),
TBHP (0.3 mL), 1 (8 mg), MeOH (1 mL), time 12 h. Conversion and
selectivity were determined by GC-MS. Side products resulted from the
homo-coupling of substituted benzylamines
usually poison metal catalyst by S atom, and aliphatic amines
(
entries 10-11), which are relatively difficult to be oxidized, could
also smoothly conversed to their corresponding products with
moderate conversions and selectivities, demonstrating the
remarkable catalytic ability and broad tolerance of 1. In order to
investigate the oxidative ability of 1 for inert secondary amines,
dibenzylamine and 1,2,3,4-tetrahydroisoquinoline were tested. It
was found that only 12% of 1,2,3,4-tetrahydroisoquinoline can be
conversed to 1l, possibly because of the steric difficulty of
abstracting H atoms next to N-H group.
To verify the possibility of benzaldehyde as one of the
intermediate, equal amounts of benzaldehyde and benzylamine
were simultaneously added into the system, experimental results
indicated that this reaction processed successfully with 1a in 93%
yield and 99% selectivity (Scheme S2), confirming the rationality
of our hypotheses. To rule out the participation of O
,
2
explorations under inert and O atmosphere were also carried out
2
(Scheme S3), the similar conversions and selectivities proved that
TBHP is the only oxidant during the whole process.
The excellent performance of
1
in the oxidative
homo-coupling of amines encouraged us to check the possibility
of 1 in the synthesis of unsymmertical imines. As table 2 showed,
a variety of structurally different benzylamines were selected to
cross-coupling with aniline at the molar ratio of 1:5. After stirring
for 12 h, all of the substituted benzylamines could be conversed
completely to the expected products and homo-coupling
products with a moderate selectivity, which showed the trend
that the stronger the electron-withdrawing ability, the poor the
selectivity. Further investigation revealed that the cross-coupling
of benzylamine with aliphatic amines could also proceed
successfully, though the conversions and selectivity were less
than satisfactory (Table S8). These results demonstrated the
broad applicability of 1 in the oxidative coupling of amines to
imines.
Basing on the literature reports and taking the above
investigation into consideration, a possible reaction mechanism
II
(Figure 3) was proposed as following: Mn at the node of 1 was
IV
[22]
III
oxidized to Mn by TBHP,
which was then reduced to Mn
through electron transfer from benzylamine, accompaning with
[24，33]
the formation of benzylamine cation radical A.
After that, A
expelled one benzylic proton to produce benzylideneamine
[
33]
III
radical B,
that is oxidized by Mn and generate the positively
[24]
charged intermediate C.
With proton releasing, C converted to
the intermediate reactive D, which hydrolyzed rapidly to
[22]
benzaldehyde with the elimination of molecule ammonia.
Finally, the aldehyde attacked nucleophilically by another
benzylamine and give 1a as target product and H O as by-product,
2
[21-22]
which would be consumed when D hydrolyzed to aldehyde.
To confirm the heterogeneity of this reaction, 1 in the finished
reaction mixture of benzylamine was filtered and a new portion
of reactants was added. The yields of 1a was monitored every 2 h
Conclusions
1
by H NMR and no significant additional increase was observed
In summary, we have got the first defined heterometallic
(
Figure S14), confirming the heterogeneity of 1. To quantify the
cluster (Fe Mn( -O)) based 1 with synergistic effect through the
2
3
3+ 2+
homogeneous Fe or Mn leached from 1 into the reaction
ligand replacement of prepared [Fe Mn( -O)(CH COO) ] with
2
3
3
6
mixture, ICP-OES analyses was performed and results revealed
BPTC. 1 is applicable to the synthesis of symmetrical as well as
unsymmetrical imines through the oxidative coupling of primary
amines at moderate conditions. Catalytic results indicated that 1
is heterogeneous and can be reused for at least 8 runs without
any complicated reactivation. Further control experiment
revealed that the catalytic active site in 1 is mainly attributing to
the introduced Mn and Fe synergistically contributes to the
stability. Considering the fact that Cr -based MOFs with Cr O SBU
usually show superior chemical stability and could be obtained by
solvent-assisted metal metathesis from Fe -based MOFs, the
3+
2+
that the leached Fe and Mn were less than 0.18% and 0.21% of
the total content in loaded 1, respectively. Meanwhile, as
confirmed by PXRD patterns (Figure S12), the crystallinity of 1
could be maintained after each reaction. Benefiting from the air
for more than 8 runs without distinct decrease in yields (Table S9,
Figure S13). amines, experiments of benzylamine and its
3+
para-substituted derivatives (X = CF , H, CH and OCH ) were
3
3
3
3
carried out over 1 to calculate the reaction rates and achieve the
Hammett plot. Experimental results indicated that the reaction
3
+
4
www.cjc.wiley-vch.de
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
This article is protected by copyright. All rights reserved.
Chin. J. Chem. 2021, 39, XXX－XXX

Running title
Chin. J. Chem.
following work for the synthesis of imines through oxidative
A mixture of benzylamine (6 mmol) and activated 1 (48 mg,
0.053 mmol) in MeOH (6 mL) was stirring at room temperature,
then TBHP (1.8 mL) was added dropwise by dropper. After that
the resulting suspension was stirred until all of the benzylamine
was consumed. The catalyst was recovered by centrifugation,
washed with fresh MeOH (8×4 mL) and air-dried for next runs.
The supernatant was evaporated to dryness for the
coupling of amines under the catalysis of (Cr Mn( -O)) based
2
3
MOF will be performed. Our works may pave a new way for the
development of the catalysts for the synthesis of imines.
Experimental
1
determination of H NMR yield of 1a.
General
All reagents were purchased from Energy Chemical and used
without further purification. PXRD patterns were measured on
Rigaku D/Max-2500 diffractometer with Cu target tube at 40 kV
and 30 mA. IR spectrum on KBr pellet was obtained using a
Nicolet iS50 spectrometer in the region of 4000-400 cm .
Thermogravimetric analyses (TGA) were performed on Shanghai
General procedure for the cross-oxidative coupling of two
different amines
A
mixture of substituted benzylamines (1 mmol) or
-1
benzylamine (1 mmol), aniline (5 mmol) or aliphatic amines (5
mmol) and activated 1 (8 mg, 0.009 mmol) in MeOH (1 mL) was
stirring at room temperature, then TBHP (0.3 mL) was added and
the resulting suspension was stirred continuously for 12 h. After
that 100 mL of the reaction mixture was taken out and diluted
with n-hexane to 10mL for GC-MS to determine the yield and
selectivity of target products.
yinnuo 1000 B under N atmosphere at a heating rate of 10 °C
2
-1
min . Scanning electron microscope energy-dispersive X-ray
spectroscopy (SEM-EDS) analyses were conducted on
a
JSM-7500F SEM equipped with an EDAX CDU leap detector. X-ray
photoelectron spectroscopy (XPS) was carried out on a Thermo
Fisher SCIENTIFIC using Al Kα X-ray source. Binding energies (BE)
were calibrated by setting the measured BE of C 1s to 284.80 eV.
ICP-OES analysis was performed on PerkinElmer Optima 8000
Procedure for filtration experiment
A mixture of benzylamine (1 mmol), TBHP (0.3 mL) and
activated 1 (8 mg, 0.009 mmol) in MeOH (1 mL) was stirring at
room temperature for 12 h, then the catalyst was removed by
centrifugation and a new portion of reactants was added to the
Plasma Emission Spectrometer. The sorption isotherms for N (77
2
K) and CO (298 K and 273 K) gas were measured with ASPS 2020
2
1
gas sorption analyzer. H NMR was recorded on Bruker Avance III
1
supernatant, yield of 1a after every 2 h was determined by H
DM 600 MHz. GC-MS analysis was performed on Shimadzu Gas
TM
NMR.
Chromatograph with Nexis GC-2030 system.
Procedure for metal leaching analysis
Preparation of [Fe Mn( -O)(CH COO) ]
2
3
3
6
After the completely conversion of benzylamine to 1a, 1 was
separated by centrifugation and washed with fresh MeOH for 3
times. The combined solution was concentrated to 1 mL by
heating and stood for 1 day with 15 mL aqua regia. After that the
mixture was heated at 160 °C until only 1 mL liquid was left. Then
One reported procedure was used to prepare
[38]
[
Fe Mn( -O)(CH COO) ]. A solution of NaOAc (5.0 g, 62 mmol)
2 3 3 6
in H O (10 mL) was added dropwise to the mixture of
2
Fe(NO ) ·9H O (1.6 g, 4 mmol) and Mn(OAc) ·4H O (4.9 g, 20
3
3
2
2
2
mmol) in H O (14 mL) under stirring. Then the resulting mixture
2
a new portion of HCl or HNO was added and removed by heating
3
was stirred overnight and separated by filtrating, the filter cake
after standing for few hours. This digestion process was repeated
was washed with H O for several times and dried in oven. IR (KBr)
2
until the solution was transparent when H O was added. The
2
ν: 1654 (s), 1616 (s), 1589 (s), 1566 (s), 1439 (s), 1402 (s), 1385 (s),
257 (w), 1176 (w), 1149 (w), 1109 (m), 1019 (w), 865 (w), 775 (s).
remaining mixture was diluted with 2% HNO aqueous solution to
3
1
2
5 mL and analyzed by ICP-OES for the quantification of leached
Preparation of [Fe Mn( -O)(BPTC) (DMF) (H O)] (1)
Fe and Mn
2
3
2
2
2
[
Fe Mn( -O)(CH COO) ] (10 mg, 0.019 mmol), BPTC (10 mg,
2 3 3 6
0
.035 mmol), HOAc (0.3 mL) and Dimethylformamide (DMF, 2 mL) Supporting Information
were placed in a 15 mL Teflon-lined stainless steel reactor and
heated at 150 °C in an oven for 48 hours. After cooling to room
temperature, red crystals were obtained in 70% yield based on
BPTC. IR (KBr): 1653 (s), 1614 (s), 1587 (s), 1562 (s), 1438 (s), 1403
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2021xxxxx.
(
8
s), 1386 (s), 1257 (w), 1177 (w), 1147 (w), 1108 (m), 1020 (w),
64 (w), 773 (m), 718 (m), 616 (w), 501 (w), 473 (w).
Acknowledgement
This work was supported by the “1331” project of Shanxi
Province, Scientific and Technological Innovation Programs of
Higher Education Institutions in Shanxi (2019L0464 and
2019L0451), Shanxi Province Science Foundation for Youths
(201901D211391), Research Project Supported by Shanxi
Scholarship Council of China (2020-088).
X-ray crystallography
Single crystal of 1 was used in intensity data collection using a
Bruker SMARTAPEX CCD diffractometer at 298 (2) K (λ = 0.71073
Å). The structure was solved by direct methods and refined by
full-matrix least-squares methods with SHELXTL. All non-hydrogen
atoms were refined with anisotropic thermal parameters.
General procedure for the catalytic oxidative coupling of amines References
to imines
[
1] Kobayashi, S.; Mori, Y.; Fossey, J. S.; Salter, M. M. Catalytic
TBHP (70% in H O, 0.3 mL) was added to the mixture of
2
Enantioselective Formation of C−C Bonds by Addition to Imines and
Hydrazones: A Ten-Year Update. Chem. Rev. 2011, 111, 2626－2704.
2] Schümperli, M. T.; Hammond, C.; Hermans, I. Developments in the
Aerobic Oxidation of Amines. ACS Catal. 2012, 2, 1108－1117.
3] Chen, B.; Wang, L.; Gao, S. Recent Advances in Aerobic Oxidation of
Alcohols and Amines to Imines. ACS Catal. 2015, 5, 5851－5876.
4] Lin, J.; Guo, Z.; Zhan, H. A Robust Phenazine-Containing Organic
amines (1 mmol) and activated 1 (8 mg, 0.009 mmol) in MeOH (1
mL). Then the resulting suspension was stirred at room
temperature for 12 h. After that 1 was separated by filtration and
[
[
[
1
the filtrate was evaporated to dryness for H NMR and GC-MS to
determine the yield and selectivity of corresponding imines.
Procedure for recycling oxidative coupling of benzylamine
Chin. J. Chem. 2021, 39, XXX－XXX
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
www.cjc.wiley-vch.de
5
This article is protected by copyright. All rights reserved.

Report
First author et al.
Polymer as Catalyst for Amine Oxidative Coupling Reactions. J. Catal.
020, 385, 338－344.
meso-Tetraphenylporphyrin Chloride under Ambient Conditions.
Catal. Commun. 2010, 12, 202－206.
2
[
[
5] Zhang, N.; Li, X.; Liu, Y.; Long, R.; Li, M.; Chen, S.; Qi, Z.; Wang, C.;
Song, L.; Jiang, J.; Xiong, Y. Defective Tungsten Oxide Hydrate
Nanosheets for Boosting Aerobic Coupling of Amines: Synergistic
Catalysis by Oxygen Vacancies and Brønsted Acid Sites. Small 2017,
[22] Zhou, X.-T.; Ren, Q.-G.; Ji, H.-B. Mimicking the Environment of Living
Organisms to Achieve the Oxidative Coupling of Amines to Imines
Catalyzed by Water-Soluble Metalloporphyrins. Tetrahedron Lett.
2012, 53, 3369－3373.
[23] Kim, S. S.；Thakur, S. S. Oxidative Coupling of Benzylamines into
N-Benzylbenzaldimines with MnTPPCl/t-BuOOH. Bull. Korean Chem.
Soc. 2005, 26, 1600－1602.
[24] Kim, S. S.; Thakur, S. S.; Song, J. Y.; Lee, K.-H. Oxidative Coupling of
Benzylamines into N-Benzylbenzaldimines with Mn(II)/tert-BuOOH
Bull. Korean Chem. Soc. 2005, 26, 499－501.
1
3, 1701354－1701363.
6] Hudwekar, A. D.; Verma, P. K.; Kour, J.; Balgotra, S.; Sawant, S. D.
Transition Metal-Free Oxidative Coupling of Primary Amines in
Polyethylene Glycol at Room Temperature: Synthesis of Imines,
Azobenzenes, Benzothiazoles, and Disulfides. Eur. J. Org. Chem. 2019,
4
2－1250.
[
[
[
7] Furukawa, S.; Ohno, Y.; Shishido, T.; Teramura, K.; Tanaka, T.
[25] Chen, F.; Yang, T.; Zhao, S.; Jiang, T.; Yu, L.; Xiong, H.; Guo, C.; Rao, Y.;
Liu, Y.; Liu, L.; Zhou, J.; Tu, P.; Ni, J.; Zhang, Q.; Li, X. Highly Selective
2 5 2
Selective Amine Oxidation Using Nb O Photocatalyst and O . ACS
Catal. 2011, 1, 1150－1153.
8] Lang, X.; Ji, H.; Chen, C.; Ma, W.; Zhao, J. Selective Formation of
2 3
Oxidation of Amines to Imines by Mn O Catalyst under Eco-friendly
Conditions. Chin.Chem. Lett. 2019, 30, 2282－2286.
[26] Biswas, S.; Dutta, B.; Mullick, K.; Kuo, C.-H.; Poyraz, A. S.; Suib, S. L.
Aerobic Oxidation of Amines to Imines by Cesium-Promoted
Mesoporous Manganese Oxide. ACS Catal. 2015, 5, 4394－4403.
[27] Dutta, B.; Amin, A. S.; Wu, Y.; Poges, S.; Alpay, S. P.; Suib, S. L.
Imines by Aerobic Photocatalytic Oxidation of Amines on TiO
2
.
Angew. Chem. Int. Ed. 2011, 50, 3934－3937.
9] Neeli, C. K. P.; Ganji, S.; Ganjala, V. S. P.; Kamaraju, S. R. R.; Burri, D. R.
Oxidative Coupling of Primary Amines to Iminesunder Base-Free and
Additive-Free Conditions Over AuNPs/SBA-NH
2
Nanocatalyst. RSC
Mesoporous Cobalt/Manganese Oxide:
a
Highly Selective
Adv. 2014. 4, 14128－14135.
Bifunctional Catalyst for Amine-Imine Transformations. Green Chem.
2018, 20, 3180－3185.
[28] Zhang, Z.; Wang, F.; Wang, M.; Xu, S. T.; Chen, H. J.; Zhang, C. F.; Xu, J.
Tert-Butyl Hydroperoxide (TBHP)-Mediated Oxidative Self-Coupling
[
[
10] He, L.-P.; Chen, T.; Gong, D.; Lai, Z. P.; Huang, K.-W. Enhanced
Reactivities toward Amines by Introducing an Imine Arm to the
Pincer Ligand: Direct Coupling of Two Amines To Form an Imine
Without Oxidant. Organometallics 2012, 31, 5208－5211.
2
of Amines to Imines overα-MnO Catalyst. Green Chem. 2014, 16
11] Rodriguez-Lugo, R. E.; Chacon-Teran, M. A.; Leon, S. D.; Vogt, M.;
Rosenthal, A. J.; Landaeta, V. R. Synthesis, Characterization and
Pd(II)-Coordination Chemistry of the Ligand Tris(quinolin-8-yl)
Phosphite. Application in the Catalytic Aerobic Oxidation of Amines.
Dalton Trans. 2018, 47, 2061－2072.
2523－2527.
[29] Qiu, X.; Len, C.; Luque, R.; Li, Y. Solventless Oxidative Coupling of
Amines to Imines by Using Transition-Metal-Free Metal-Organic
Frameworks. ChemSusChem 2014, 7, 1684－1688.
4
[30] Qiao, W.; Song, T.; Zhao, B. [Zn O] Cluster-Based Metal-Organic
[
[
12] Deng, W.; Chen, J.; Kang, J.; Zhang, Q.; Wang, Y. Carbon
Nanotube-Supported Au-Pd Alloy with Cooperative Effect of Metal
Nanoparticles and Organic Ketone/Quinone Groups as a Highly
Efficient Catalyst for Aerobic Oxidation of Amines. Chem. Commun.
2
Frameworks as Catalysts for Conversion of CO . Chin. J. Chem. 2019,
37, 474－478.
[31] Wang, X.; Zhang, Y.; Chang, Z.; Huang, H.; Liu, X.-T.; Xu, J.; Bu, X.-H.
Synergistically Directed Assembly of Aromatic Stacks Based
Metal-Organic Frameworks by Donor-Acceptor and Coordination
Interactions. Chin. J. Chem. 2019, 37, 871－877.
[32] Ge, D.; Qu, G.; Li, X.; Geng, K.; Cao, X.; Gu, H. Novel Transition
Bimetal-Organic Frameworks: Recyclable Catalyst for the Oxidative
Coupling of Primary Amines to Imines at Mild Conditions. New J.
Chem. 2016, 40, 5531－5536.
[33] Xu, C.; Liu, H.; Li, D.; Sub, J.-H.; Jiang, H.-L. Direct Evidence of Charge
Separation in a Metal-Organic Framework: Efficient and Selective
Photocatalytic Oxidative Coupling of Amines via Charge and Energy
Transfer. Chem. Sci. 2018, 9, 3152－3158.
[34] Nagarjun, N.; Jacob, M.; Varalakshmi, P.; Dhakshinamoorthy, A.
UiO-66(Ce) Metal-Organic Framework as a Highly Active and
Selective Catalyst for the Aerobic Oxidation of Benzyl Amines. Mol.
Catal. 2021, 499, 111277－111284.
[35] Venu, B.; Shirisha, V.; Vishali, B.; Naresh, G.; Kishore, R.; Sreedhar, I.;
Venugopal, A. A Cu-BTC Metal-Organic Framework (MOF) as an
Efficient Heterogeneous Catalyst for the Aerobic Oxidative Synthesis
of Imines from Primary Amines under Solvent free conditions. New J.
Chem. 2020, 44, 5972－5979.
[36] Liu, H.; Guo, Z.; Lv, H.; Liu, X.; Che, Y.; Mei, Yi.; Bai, R.; Chi, Y.; Xing, H.
Visible-Light-Driven Self-Coupling and Oxidative Dehydrogenation of
Amines to Imines via a Mn(II)-Based Coordination Polymer. Inorg.
Chem. Front. 2020, 7, 1016－1025.
2
016, 52, 6805－6808.
13] Johnson, J. A.; Luo, J.; Zhang, X.; Chen, Y.-S.; Morton, M. D.
Porphyrin-Metalation-Mediated Tuning of Photoredox Catalytic
Properties in Metal-Organic Frameworks. ACS Catal. 2015, 5, 5283－
5
291.
14] Largeron, M.; Fleury, M.-B. Bioinspired Oxidation Catalysts. Science
013, 339, 43－44.
15] Largeron, M.; Fleury, M.-B.
Topaquinone-Like Co-Catalytic
[
[
2
I
A
Biologically Inspired Cu
/
System for the Highly
Atom-Economical Aerobic Oxidation of Primary Amines to Imines.
Angew. Chem. Int. Ed. 2012, 51, 5409－5412.
[
[
[
[
16] Aguirre-Díaz, L. M.; Snejko, N.; Iglesias, M.; Sáncheꢀꢁ F.ꢂ
ꢃutiꢄrreꢀ-Puebla E.; Monge M. ꢅ. Efficient Rare-Earth-Based
Coordination Polymers as Green Photocatalysts for the Synthesis of
Imines at Room Temperature. Inorg. Chem. 2018, 57, 6883－6892.
17] Su, F.; Mathew, S. C.; Mꢆhlmann, L.; Antonietti, M.; Wang, X.,
Blechert S. Aerobic Oxidative Coupling of Amines by Carbon Nitride
Photocatalysis with Visible Light. Angew. Chem. Int. Ed. 2011, 50, 657
－660.
18] Wang, K.; Jiang, P.; Yang, M.; Ma, P.; Qin, J.; Huang, X.; Ma, L.; Li, R.
Metal-Free Nitrogen-Doped Carbon Nanosheets: a Catalyst for the
Direct Synthesis of Imines under Mild Conditions. Green Chem. 2019,
2
1, 2448－2461.
19] He, H.; Li, Z.; Li, K.; Lei, G.; Guan, X.; Zhang, G.; Zhang, F.; Fan, X.;
Peng, W.; Li, Y. Bifunctional Graphene-Based Metal-Free Catalysts for
Oxidative Coupling of Amines. ACS Appl. Mater. Interfaces 2019, 11,
[37] Wei, Y.-S.; Zhang, M.; Zou, R.; Xu, Q. Metal-Organic
Framework-Based Catalysts with Single Metal Sites. Chem. Rev. 2020,
120, 12089－12174.
3
1844－31850.
[38] Feng, D.; Wang, K.; Wei, Z.; Chen, Y.-P.; Simon, C. M.; Arvapally, R. K.;
Martin, R. L.; Bosch, M.; Liu, T.-F.; Fordham, S.; Yuan, D.; Omary, M.
A.; Haranczyk, M.; Smit, B.; Zhou, H.-C. Kinetically Tuned Dimensional
Augmentation as a Versatile Synthetic Route Towards Robust
Metal-Organic Frameworks. Nat. Commun. 2014, 5, 5723－5730.
[39] Wang, X.-L.; Dong, L.-Z.; Qiao, M.; Tang, Y.-J.; Liu, J.; Li, Y.; Li, S.-L.; Su,
[
[
20] Zhao, C.; Gao, Y.; Zhang, Z.; Ma, D. Functions of Phytic Acid in
Fabricating Metal-Free Carbocatalyst for Oxidative Coupling of
Benzylamines. Chin. J. Chem. 2020, 38, 1292－1298.
21] Yuan, Q.-L.; Zhou, X.-T.; Ji, H.-B. Efficient Oxidative Coupling of
Amines
to
Imines
Catalyzed
by
Manganese(III)
6
www.cjc.wiley-vch.de
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
This article is protected by copyright. All rights reserved.
Chin. J. Chem. 2021, 39, XXX－XXX

Running title
Chin. J. Chem.
J.-X.; Lan, Y.-Q. Exploring the Performance Improvement of the
Frameworks. J. Am. Chem. Soc. 2016, 138, 13822－13825.
Oxygen Evolution Reactionina Stable Bimetal-Organic Framework
System. Angew. Chem. Int. Ed. 2018, 57, 9660－9664.
[45] Blake, A. B.; Yavari, A.; Kubicki, H. Exchange Interactions in a Series of
Novel Heteronuclear Basic Carboxylate Complexes Containing Two
Iron(III) Ions and a Divalent Metal Ion. J. C. S. Chem. Comm. 1981,
796－797.
[46] Blake, A. B. Yavari, A. Magnetic and Spectroscopic Properties of
Some Heterotrinuclear Basic Acetates of Chromium(III), Iron(III), and
Divalent Metal Ions. J. Chem. Soc. Dalton Trans. 1985, 2509－2520.
[47] Blatov, V. A.; Shevchenko, A. P.; Proserpio, D. M. Applied Topological
Analysis of Crystal Structures with the Program Package ToposPro.
Cryst. Growth Des. 2014, 14, 3576－3586.
[
40] Wongsakulphasatch, S.; Nouar, F.; Rodriguez, J.; Scott, L.; Guillouzer,
C. L.; Devic, T.; Horcajada, P.; Grenèche, J.-M.; Llewellyn, P. L.;
Vimont, A.; Clet, G.; Daturid, M.; Serre, C.; Direct Accessibility of
Mixed-Metal (III/II) Acid Sites Through the Rational Synthesis of
Porous Metal Carboxylates. Chem. Commun. 2015, 51, 10194－
1
0197.
[
[
41] Surblé, S.;Millange, F.; Serre, C.; Férey G.; Walton, R. I. An EXAFS
Study of the Formation of a Nanoporous Metal-Organic Framework:
Evidence for the Retention of Secondary Building units During
Synthesis. Chem. Commun. 2006, 1518－1520.
[48] Brown, H. C.; Okamoto, Y. Electrophilic Substituent Constants. J. Am.
Chem. Soc. 1958, 80, 4979－4987.
42] Wang, J.-H.; Zhang, Y.; Li, M.; Yan, S.; Li, D.; Zhang, X.-M.
Solvent-Assisted Metal Metathesis: A Highly Efficient and Versatile
Route towards Synthetically Demanding Chromium Metal-Organic
Frameworks. Angew. Chem. Int. Ed. 2017, 56, 6478－6482.
(The following will be filled in by the editorial staff)
Manuscript received: XXXX, 2021
Manuscript revised: XXXX, 2021
[
[
43] Zhang, X.; Wang, X.; Fan, W.; Sun, D. Pore-Environment Engineering
in Multifunctional Metal-Organic Frameworks. Chin. J. Chem. 2020,
Manuscript accepted: XXXX, 2021
Accepted manuscript online: XXXX, 2021
Version of record online: XXXX, 2021
3
8, 509－524.
44] Liu, Q.; Cong, H.; Deng, H. Deciphering the Spatial Arrangement of
Metals and Correlation to Reactivity in Multivariate Metal-Organic
Chin. J. Chem. 2021, 39, XXX－XXX
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
www.cjc.wiley-vch.de
7
This article is protected by copyright. All rights reserved.

Report
First author et al.
Entry for the Table of Contents
2 3 6
Fe Mn( -O)(COO) cluster based stable MOF for oxidative coupling of amines via bimetallic synergy
Ying-Xia Wang, Hui-Min Wang, Pan Meng, Dong-Xia Song, Zhikai Qi and Xian-Ming Zhang*
Chin. J. Chem. 2021, 39, XXX—XXX. DOI: 10.1002/cjoc.202100XXX
Catalytic active Mn was introduced into stable Fe
2 3
M( -O) cluster based MOF and used for the oxidative homo- or cross-coupling of amines with low
catalyst loading, high selectivity, broad substrate, good recyclability and synergistic effect.
8
www.cjc.wiley-vch.de
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
This article is protected by copyright. All rights reserved.
Chin. J. Chem. 2021, 39, XXX－XXX