Hybrid Metalloporphyrin Magnetic Nanoparticles as Catalysts for Sequential Transformation of Alkenes and CO2 into Cyclic Carbonates

Article abstract of DOI:10.1002/cctc.201800397

The synthesis and full characterization of manganese and chromium metalloporphyrins and hybrid magnetic nanocomposites prepared thereof is described. Their application in homogeneous and heterogeneous sequential epoxidation/CO₂ cycloaddition reactions by using O₂ or H₂O₂ as the oxidant showed high activity and selectivity for the preparation of a variety of cyclic carbonates directly from olefins. The combination of manganese and chromium nanocomposites allowed us to set the keystone for the development of a reusable dual catalytic system to transform olefins into cyclic carbonates.

Full text of DOI:10.1002/cctc.201800397

Accepted Article
Title: Hybrid-Metalloporphyrin Magnetic Nanoparticles as Catalysts
for Sequential Transformation of Alkenes and CO2 into Cyclic
Carbonates
Authors: Lucas D. Dias, Rui M. B. Carrilho, César A. Henriques, Mário
J. F. Calvete, Anna M. Masdeu-Bultó, Carmen Claver, Liane
M. Rossi, and Mariette M. Pereira
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10.1002/cctc.201800397
ChemCatChem
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Hybrid-Metalloporphyrin Magnetic Nanoparticles as Catalysts for
Sequential Transformation of Alkenes and CO2 into Cyclic
Carbonates
Lucas D. Dias,[a] Rui M. B. Carrilho,*[a] César A. Henriques,[a] Mário J. F. Calvete,[a]
Anna M. Masdeu-Bultó,[b] Carmen Claver,[b,c] Liane M. Rossi,[d] and Mariette M. Pereira*[a]
Abstract: The synthesis and full characterization of manganese and
chromium metalloporphyrins and hybrid magnetic nanocomposites
prepared thereof is described. Their application in homogeneous and
heterogeneous sequential epoxidation/CO2 cycloaddition reactions
using O2 or H2O2 as oxidant showed high activity and selectivity for
the preparation of a variety of cyclic carbonates directly from olefins.
The combination of manganese and chromium nanocomposites
allowed to set the keystone for the development of a reusable dual
catalytic system to transform olefins into cyclic carbonates.
procedures.[44-48] Alternatively, synthetic metalloporphyrins have
been described as excellent cytochrome-P450 biomimetic
catalysts to selectively promote olefin epoxidation in a sustainable
[49-62]
fashion.
Despite such advances, the design of efficient
catalytic systems able to sequentially promote olefin epoxidation
followed by CO2 addition to epoxides is a great challenge[63,64] and
further studies are still required to overcome several issues
related with the instability of homogeneous catalysts and the
selection of appropriate oxidants.[65-70] Therefore, more robust
catalysts such as heterogeneous and/or biphasic systems have
been lately developed, namely those based on metal oxides[71,72]
supported gold catalysts,[73-75] sodium phosphotungstate[76] and
ionic liquids,[77] most of them using alkyl hydroperoxides as
oxygen donors. Nevertheless, to the best of our knowledge, there
are no reports on the application of heterogeneous
metalloporphyrin-based recyclable catalysts to promote the
sequential transformation of olefins into cyclic carbonates, using
green oxidants such as O2 or H2O2. From the existing literature
and our own previous experience, the introduction of halogen
atoms at metalloporphyrin's macrocycle structure is known to
enhance their catalytic activity and stability in both epoxidation
Introduction
The demand for renewable raw materials by the chemical industry
is a crucial issue regarding the development of low-carbon
economy.[1,2] In this context, conversion of carbon dioxide into
valuable organic chemicals[3-9]has become a topic with increasing
awareness, with remarkable economic and environmental
impacts. Among numerous possible transformations, the
cycloaddition of carbon dioxide to epoxides is an atom-economic
approach to prepare cyclic carbonates,[10-13] which have a wide
range of applications, namely as intermediates for fine chemicals
or in plastics industry, in biomedical applications, as electrolytes
for lithium batteries, fuel additives or green solvents. [14-17] So far,
great efforts have been devoted to the development of efficient
catalytic systems for this conversion,[10,18,19] such as
[78-80]
and CO2 addition to epoxides.[82] Particularly, fluorinated
groups are highly advantageous because they also increase the
catalyst's solubility in compressed CO2, avoiding the use of
solvents.[83,84]
So, with our aim focused on the development of efficient and
stable catalytic systems for sequential transformations,[85,86,87]
herein we report the synthesis and characterization of hybrid
manganese(III) and chromium(III) halogenated porphyrin
magnetic nanocomposites and their application as reusable
catalysts in olefin epoxidation (using O2 or H2O2 as the oxidants)
and in CO2 cycloaddition to epoxides. Finally, an heterobimetallic
dual catalyst, prepared by the appropriate amounts combining
Mn(III)-porphyrin and Cr(III)-porphyrin hybrid materials was
applied in sequential transformation of olefins into cyclic
carbonates.
organocatalysts,[20-22] ionic liquids[23,24] and metal catalysts,[25,31]
[32-43]
namely those based on metalloporphyrins.
However, the
previous synthesis of epoxides often involve the use of toxic and
expensive reagents, and require hard separation/purification
[a]
L. D. Dias, Dr. R. M. B. Carrilho*, Dr. C. A. Henriques,
Dr. M. J. F. Calvete, Prof. M. M. Pereira*
CQC, Department of Chemistry, University of Coimbra
Rua Larga, 3004-535 Coimbra (Portugal)
E-mail: mmpereira@qui.uc.pt; Tel.: +351 239 854 474
rmcarrilho@gmail.com Tel.: +351 239 854 474
Results and Discussion
[b]
[c]
[d]
Prof. A. M. Masdeu-Bultó, Prof. C. Claver
Department of Physical and Inorganic Chemistry, University Rovira
i Virgili, Marcel.lí Domingo, 43007 Tarragona (Spain)
Metalloporphyrin complexes (Figure 1) were prepared through
condensation of pyrrole with substituted benzaldehydes, using
optimized synthetic strategies developed by the Coimbra's
group,[88-91] followed by metallation of free-base porphyrins,
through modifications of the DMF/metal salt method.[92,93]
Prof. C. Claver
Centre Tecnològic de la Química, Marcel.lí Domingo s/n
Campus Sescelades, 43007 Tarragona (Spain)
Prof. L. M. Rossi
Departamento de Química Fundamental, Instituto de Química,
Universidade de São Paulo, 05508-000 São Paulo (Brasil)
Supporting information for this article is given via a link at the end of the
document.
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10.1002/cctc.201800397
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Figure 1. Metalloporphyrin-based homogeneous catalysts and precursors.
Scheme 1. Preparation of hybrid metalloporphyrin-based magnetic materials MNP@SiO2-3Mn, MNP@SiO2-4Cr and MNP@SiO2-8Mn.
The hybrid metalloporphyrin-based heterogeneous catalysts were
prepared using two different approaches: i) covalent attachment
grafting onto the magnetic support was carried out by reacting
each nitro-metalloporphyrin with the aminopropyl-functionalized
silica-coated magnetite nanoparticles, using cesium carbonate as
base and DME as solvent (Scheme 1, via A), which led to the
desired hybrid materials MNP@SiO2-3Mn and MNP@SiO2-4Cr.
Likewise, the hybrid nanocomposite MNP@SiO2-8Mn was
prepared accordingly to our recently described methodology,[51]
by covalent linkage of the amine group at the meso-aryl position
of the non-symmetric metalloporphyrin 8Mn to the magnetic
support, by reacting the silica-coated magnetite nanoparticles
(MNP@SiO2)[94,95] with 3-chloropropyltriethoxisilane (CPTES)
followed by addition of aminated metalloporphyrin 8Mn, using
Et3N as base (Scheme 1, via B).
to
aminopropyl-functionalized
silica-coated
magnetite
nanoparticles via β-ipso-nitro aromatic nucleophilic substitution
(Scheme 1, via A); ii) covalent grafting chloropropyl-functionalized
silica coated magnetite nanoparticles via nucleophilic substitution
(Scheme 1, via B). The synthesis of MNP@SiO2-3Mn and
MNP@SiO2-4Cr involved the previous nitration of meso-tetra(4-
(trifluoromethyl)phenyl)porphyrin with copper(II) nitrate in an
acetic anhydride/acetic acid mixture, followed by demetallation in
acidic
medium,
which
afforded
in
β-nitro-meso-tetra(4-
89% yield. Metal
(trifluoromethyl)phenyl)porphyrin
complexation was subsequently performed by reaction with
manganese(II) acetate or chromium (II) chloride, in DMF, which
afforded beta-mononitrated metalloporphyrins 3Mn and 4Cr in
79% and 84% isolated yields, respectively. Finally, covalent
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10.1002/cctc.201800397
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described by some of us.[51] Transmission electron microscopy
(TEM) images (Figure 2) showed that the silica-coated magnetite
nanoparticles (MNP@SiO2) display a spherical morphology,
having an average diameter of 23 ± 2 nm, which is substantially
higher than that of the uncoated magnetite nanoparticle MNP
(7 ± 2 nm). The metal content of the hybrid materials was
determined by ICP, which indicated a Mn percentage of 0.026%
in MNP@SiO2-3Mn, a Cr percentage of 0.260% in MNP@SiO2-
4Cr and a Mn percentage of 0.090% in MNP@SiO2-8Mn.
Characterization of catalysts based on metalloporphyrins
hybrid magnetic nanoparticles
The hybrid nanocomposites were characterized by inductively
coupled plasma atomic emission spectroscopy (ICP), UV-visible
spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy
(FTIR) and thermogravimetry-differential scanning calorimetry
(TG/DSC). The physical/chemical characterization data of
MNP@SiO2-8Mn was in agreement with that previously
Figure 2. Transmission electron microscopy (TEM) images and the corresponding particle size distribution histograms of: a) MNP; b) MNP@SiO2
The quantification of the organic content in the nanocomposite
materials was carried out by TG/DSC measurements in the range
25 °C-800 °C (Figure 3). All diagrams present an endothermic
peak between 30 °C and 175 °C, attributed to weight loss of
physically adsorbed water and solvents. Another weight loss of
4.0% was observed for MNP@SiO2-NH2 (Figure 3a), attributed to
the decomposition of aminopropyl groups grafted at the surface
of silica-coated magnetite nanoparticle matrix (1.1% of NH2
corresponding to 0.68 mmol g−1). In the TG/DSC curves of
MNP@SiO2-3Mn and MNP@SiO2-4Cr (Figure 3b and 3c,
respectively), additional weight losses (with exothermic peaks)
occurred between 225 °C and 780 °C, which were considered to
essentially arise from decomposition of metalloporphyrins 3Mn or
4Cr. By comparison with the TG/DSC curve of MNP@SiO2-NH2,
the weight losses of MNP@SiO2-3Mn and MNP@SiO2-4Cr were
of 0.6% and 5.1%, respectively, which allowed determining the
amount of metalloporphyrins 3Mn (0.0057 mmol g-1) and 4Cr
(0.050 mmol g-1), grafted onto the magnetic support. These
values are in agreement with those obtained by ICP.
Figure 3. TG-DSC curves (weight loss - solid line; heat flow - dashed line) of: a) MNP@SiO2-NH2; b) MNP@SiO2-3Mn; c) MNP@SiO2-4Cr.
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Figure 5. Infrared spectra of: a) MNP@SiO2-NH2; b) MNP@SiO2-3Mn and c)
MNP@SiO2-4Cr, in the regions 4000-2500 cm−1 (up) and 1800-1325 cm−1
(down).
The UV–Vis absorption spectra of MNP@SiO2-3Mn and
MNP@SiO2-4Cr (Figure 4) clearly show the Soret bands at 471
nm and at 448 nm, typical of manganese (III) and chromium(III)
porphyrins, respectively, in similarity with the corresponding non-
immobilized metalloporphyrins 3Mn and 4Cr.
The effective grafting of metalloporphyrins 3Mn and 4Cr onto the
magnetic support was confirmed by infrared analysis of the hybrid
materials MNP@SiO2-3Mn and MNP@SiO2-4Cr, in contrast with
the aminopropyl-functionalized silica, MNP@SiO2-NH2 (Figure 5).
In the interval 4000-2500 cm-1 (Figure 5, up), all IR spectra show
broad bands between 3750-3300 cm−1, which are typical of
terminal silanol and hydroxyl groups in interaction, and additional
signals at 2950-2850 cm-1, which are characteristic of C–H
stretching vibrations. The spectrum of MNP@SiO2-NH2 presents
two clear bands at 3300-3400 cm-1 (Figure 5, up) and one broad
band close to 1600 cm-1 (Figure 5, down), typical of N–H
stretching of primary amines and N–H bending, respectively. In
the interval 1300-1700 cm-1 (Figure 5, d), both spectra of
MNP@SiO2-3Mn and MNP@SiO2-4Cr present characteristic
peaks at: 1450 cm−1 (C–H bending), 1410 cm−1 (Si–CH2 bending)
and 1350–1400 cm−1 (C–F stretching), indicating the presence of
trifluoromethyl-based porphyrins in the nanocomposite materials.
It should be noted that, instead of two bands in the region 3300-
3400 cm-1, both spectra of MNP@SiO2-3Mn and MNP@SiO2-4Cr
present a broad band, attributed to N–H stretching of secondary
amines, which corroborate the covalent attachment of the
metalloporphyrins, through amino groups, onto the surface of the
magnetic support.
Catalytic epoxidation
The metalloporphyrin-based homogeneous catalysts were first
evaluated in styrene epoxidation, using molecular oxygen or H2O2
as non-pollutant oxidants, in order to appraise the effects of the
metal center, porphyrin structure and oxygen source. In a typical
epoxidation reaction with O2, a round bottom flask was loaded
with the appropriate amounts of styrene, the desired
metalloporphyrin catalyst and isobutyraldehyde as co-reductant.
The solution was stirred at room temperature (25 °C), under O2
bubbling, for 90 min. Substrate conversion, along with TON
calculations and selectivity were determined by GC analysis,
using chlorobenzene as internal standard and the results are
presented in Table 1.
Figure 4. Normalized UV-Vis absorption spectra of MNP@SiO2-3Mn (up) and
MNP@SiO2-4Cr (down) dispersed in CH3CN:H2O (1:1), compared with
metalloporphyrins 3Mn and 4Cr in CHCl3.
All manganese(III)-porphyrin catalysts 1Mn, 5Mn and 6Mn (Table
1, entries 2-4) led to practically full conversions (99%) in 90 min,
presenting TON's of up to 10531, and high selectivity for epoxide
formation (86-92%), with benzaldehyde being formed as side-
product in just 8-14%. Moreover, no significant effects of the
porphyrin meso-aryl substituents were observed in the catalytic
activity. Contrarily, a strong influence of the central metal was
identified, being chromium(III)-porphyrin catalysts 2Cr, 7Cr and
9Cr significantly less active and selective towards epoxide, with
formation of benzaldehyde in up to 30%, as previously
observed[96] (Table 1, entries 5-7).The effect of porphyrin structure
and central metal on the mechanism of epoxidation reactions with
O2 have been object of several publications.[97,98] Our study
corroborates previous observations, where the use of molecular
oxygen as oxygen donor requires, in general, the presence of an
electron source.[99] Herein, we observed that the presence of
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isobutyraldehyde is crucial to obtain an active catalytic system via
high-valent metal oxo species (Table 1, entry 4), which points
toward the involvement of the Mukaiyama´s mechanism. [51,99,100]
UV-Vis analyses showed degradation of around 30% of the
Cr(III)-porphyrin catalysts 2Cr and 7Cr, after 90 min, while
Mn(III)-porphyrin catalysts 1Mn, 5Mn and 6Mn suffer
degradation of up to 85% (SI, FiguresS1–S5).
Table 1. Epoxidation of styrene using metalloporphyrins as homogeneous catalysts.[a]
Epoxide
select. (%)
Entry
Catalyst
Oxidant [O]
Conv.[b] (%)
TON[c]
1
2
-
O2
O2
3
99
78
88
86
92
70
73
72
90
98
-
319
10531
10531
10531
1595
1807
1488
24
Mn(III)OAc-TPPpCF3 (1Mn)
Mn(III)OAc-TDFPP (5Mn)
Mn(III)OAc-TDCPP (6Mn)
3
O2
99
4
O2
99 (0) [d]
15
5
Cr(III)Cl-TPPpCF3
Cr(III)Cl-TDFPP
Cr(III)Cl-TDCPP
(2Cr)
(7Cr)
(9Cr)
O2
6
O2
17
7
O2
14
8
Mn(III)OAc-TPPpCF3 (1Mn)
H2O2
H2O2
H2O2
4
9
Mn(III)OAc-TDCPP (6Mn)
99
594
10
-
0
-
[a] Reaction conditions using O2 as oxidant (entries 1-6): catalyst, styrene, isobutyraldehyde (1:10638:53191), CH2Cl2
(2 mL), O2 bubbling, T = 25 ºC, t = 90 min. Reaction conditions using H2O2 as oxidant (entries 7-9): catalyst, styrene,
NH4OAc (1 : 600 : 387), CH3CN (20 mL), T = 25 ºC, t = 45 min; H2O2 (30% w/w) solution in CH3CN (1:10) was added
to the reaction mixture (2.25 mL aliquots every 15 min). [b] Conversions calculated by GC based on chlorobenzene as
internal standard. [c] Turnover number (TON) calculated by molproducts/molcatalyst. [d] In absence of isobutyraldehyde.
The effect of the oxidant was then appraised on the catalytic
activity and stability, with the manganese(III) porphyrins 1Mn and
6Mn being further applied as catalysts in the same reaction, but
using hydrogen peroxide as alternative oxygen source, which
does not require any co-reductant (Table 1, entries 8-9). In a
model epoxidation experiment, the substrate, the selected
metalloporphyrin catalyst and ammonium acetate (axial ligand),
were dissolved in acetonitrile and stirred at room temperature.
Then, aliquots of a solution of hydrogen peroxide (30% w/w) in
CH3CN (1:10) were added to the reaction mixture, every 15 min,
along 45 min. A significant effect of the porphyrin structure was
found, evidenced by the best performance of catalyst 6Mn
(MnOAc-TDCPP), which produced full conversion in 45 min with
excellent selectivity for epoxide formation (98%), while a
conversion of only 4% was observed with catalyst 1Mn (MnOAc-
TPPpCF3). In this case, the difference of activity may be explained
by the higher stability of 6Mn (MnOAc-TDCPP) when compared
with of 1Mn (MnOAc-TPPpCF3), as corroborated by UV-Vis (SI,
Figure S3 and S5). The mechanism of H2O2 epoxidation reaction,
TDCPP, aprotic solvent and ammonium acetate as axial ligand),
the Mn(V)=O oxo species is the active species obtained directly
from the reaction of 6Mn Mn(III)TDCPPP with H2O2 (peroxidase
route).
From the studies in homogeneous phase, Mn(III)
metalloporphyrins were found to be the most promising
epoxidation catalysts, when using O2 as oxidant, presenting
higher activity and selectivity to epoxides than the Cr(III)
counterparts, probably due to the formation of highly stable and
consequently poorly active Cr(V)=O species.[96] Regarding the
epoxidation reactions using hydrogen peroxide as oxygen source,
significant conversion was only obtained with 6Mn (MnOAc-
TDCPP), containing 2,6-dichlorophenyl groups in the meso
positions. However, both strategies led to a significant catalyst's
degradation. Therefore, to overcome the catalysts instability and
allow their recycling and reuse, the hybrid heterogeneous
catalysts MNP@SiO2-3Mn and MNP@SiO2-8Mn, were then
selected to be applied in styrene epoxidation, using molecular
oxygen or hydrogen peroxide as the oxidants. The results are
reported by some of us[78,79] and other authors,[80,81] points out that, presented in Table 2.
under the above mentioned reaction conditions (6Mn MnOAc-
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Using O2 as the oxidant, heterogeneous hybrid catalyst
MNP@SiO2-8Mn gave rise to high conversions and selectivity in
the order of 94% for epoxide formation (Table 2, entry 3), while
that MNP@SiO2-3Mn showed low conversion in order to 34% and
selectivity 85% for epoxide. However, when hydrogen peroxide
was used as oxygen source, only the catalyst containing meso-
2,6-dichloro-phenyl substituents at the porphyrin structure,
MNP@SiO2-8Mn, led to high activity (SI, Figure S7), while the
trifluoromethyl-based manganese(III) porphyrin hybrid catalyst,
MNP@SiO2-3Mn, was completely inactive. These results are in
close agreement with those previously observed in homogeneous
phase (Table 1, entries 7-8 and Table 2, entries 2 and 4). The
recyclability of MNP@SiO2-8Mn was then appraised, after
magnetic recovery of the catalyst followed by washing of the solid
material with the solvent used in the catalytic reaction. When
using O2 as the oxidant, the catalyst MNP@SiO2-8Mn showed
excellent reusability along five consecutive cycles, almost without
loss of activity or selectivity for epoxide formation (Figure 6).
Therefore, besides the high activity and selectivity, it is worth
noting the stability of Mn(III) porphyrin magnetic material,
MNP@SiO2-8Mn, with no catalyst leaching being observed, as
demonstrated by ICP analyses of the liquid supernatant, which
showed a negligible metal content in solution (<0.1µg mL-1). This
stabilizing effect may be attributed to the influence of the magnetic
support in preventing the formation of catalytic inactive oxo-
dimeric metalloporphyrin species.[101]
Table 2. Evaluation of heterogeneous hybrid metalloporphyrin-based iron magnetic catalysts in styrene
epoxidation, using molecular oxygen or hydrogen peroxide as oxidants.[a]
Entry
Catalyst
Oxidant [O]
Conv.[b]
(%)
Epoxide
select. (%)
TON[c]
1
2
3
4
MNP@SiO2-3Mn
MNP@SiO2-3Mn
MNP@SiO2-8Mn
MNP@SiO2-8Mn
O2
H2O2
O2
34
2
85
41
94
92
3616
12
99
91
10531
546
H2O2
[a] Reaction conditions using O2 as the oxidant: catalyst, styrene, isobutyraldehyde, chlorobenzene (1 :
10638 : 53191 : 4148), CH2Cl2 (2 mL), O2 bubbling, T = 25 ºC, t = 140 min. Reaction conditions using H2O2
as the oxidant: catalyst, styrene, NH4OAc (1 : 600 : 387) and CH3CN (20 mL), T = 25 ºC, t = 45 min; H2O2
(30% w/w) diluted with CH3CN (1:10) was added to the reaction mixture in 450μL aliquots every 15 min. [b]
Conversions calculated by GC based on chlorobenzene as internal standard. [c] Turnover number (TON)
calculated by molproducts/molcatalyst
.
the presence of hydroxyl radicals. Blank experiments, carried out
using silica-functionalized magnetite nanoparticles (MNP@SiO2-
Cl and MNP@SiO2-NH2) as catalysts, either with O2 or H2O2 as
the oxidants, led to conversions below 1%, which discards the
involvement of the magnetic supports as the reaction's catalysts.
In
conclusion,
the
porphyrin
magnetic-nanocomposite
MNP@SiO2-8Mn was a stable, active and reusable catalyst for
styrene epoxidation using O2.
Catalytic CO2 cycloaddition to epoxides
The metalloporphyrin-based homogeneous catalysts were then
evaluated in the CO2 addition to styrene oxide, in order to
appraise the effects of the metal and porphyrin structure on the
catalytic activity and selectivity. The reactions were performed
under moderate conditions (10 bar CO2, 80 °C), using 0.07 mol%
catalyst, with and without bis(triphenylphosphine)iminium chloride
(PPNCl) as the co-catalyst. The results are collected in Table 3.
All Mn(III)-porphyrin catalysts presented low conversions in the
absence of co-catalyst but, with the addition of PPNCl, a
significant increase in their catalytic activity was observed
(Table 3, entries 2-7). The ligand’s structure had a moderate
Figure 6. Recycling experiments of MNP@SiO2-8Mn in styrene epoxidation
with O2.
Contrarily, when hydrogen peroxide was used as oxidant, the
catalyst MNP@SiO2-8Mn showed limited reusability, with a sharp
decrease in epoxide yield being observed after the third run (SI,
Figure S8). This might be due to metalloporphyrin degradation in
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Table 3. CO2 cycloaddition to styrene oxide using manganese(III) and chromium(III) metalloporphyrins as homogeneous catalysts.[a]
10.1002/cctc.201800397
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Conv.[b]
(%)
TOF
(h-1)
Entry
Catalyst
Co-catalyst
TON
1
2
–
PPNCl
30
429
157
18
MnOAc-TPPpCF3 (1Mn)
MnOAc-TPPpCF3 (1Mn)
MnOAc-TDFPP (5Mn)
MnOAc-TDFPP (5Mn)
MnOAc-TDCPP (6Mn)
MnOAc-TDCPP (6Mn)
–
PPNCl
–
11
7
3
88
1257
52
4
5
71
3
5
PPNCl
–
77
10
1100
46
6
142
5
54
7
PPNCl
–
90
1286
8
CrCl-TPPpCF3
(2Cr)
88
1257
52
9
CrCl- TPPpCF3 (2Cr)
PPNCl
–
100 (91)[c]
86
1429 (1300)[c]
1229
60 (260)[c]
51
10
11
12
13
CrCl-TDFPP
CrCl-TDFPP
CrCl-TDCPP
CrCl-TDCPP
(7Cr)
(7Cr)
(9Cr)
(9Cr)
PPNCl
-
100 (88)[c]
78
1429 (1257)[c]
1128
60 (251)[c]
47
PPNCl
100 (81)[c]
1429 (1157)[c]
60 (231)[c]
[a] Reaction conditions: styrene oxide (35 mmol, 4 mL); catalyst: 0.07 mol%; co-catalyst (when indicated): 0.07 mol% PPNCl; T = 80 °C; P (CO2) = 10 bar; t = 24
h. [b] Conversions calculated by GC based on chlorobenzene as internal standard. Selectivity for styrene carbonate, as determined by crude 1H NMR, was 100%
in all cases. [c] t = 5 h.
influence in the activity of the Mn(III) porphyrins, with the
trifluomethylphenyl (1Mn) and 2,6-dichlorophenyl-based (6Mn)
catalysts being more active than the 2,6-difluorophenyl
metalloporphyrin catalyst (5Mn), either with or without the use of
PPNCl as co-catalyst. In addition, full selectivity for the cyclic
carbonate product was observed with all Mn(III) catalytic systems,
under the studied conditions (10 bar CO2, 80 °C). On the other
hand, the Cr(III)-porphyrin catalysts were much more active than
their Mn(III) analogues, both with or without co-catalyst. In the
absence of any additive, the catalysts 2Cr, 7Cr and 9Cr led to
conversions of 88%, 86% and 78% in 24 h, respectively (Table 3,
entries 8, 10 and 12). Remarkably, the addition of PPNCl lead to
a significant increase on the activity of the Cr(III)-porphyrin
catalysts 2Cr, 7Cr and 9Cr (Table 3, entries 9, 11 and 13). The
best catalytic system is 2Cr/PPNCl, displaying 91% conversion in
just 5 h, with full selectivity for the formation of styrene carbonate
UV-Vis analysis of crude mixtures showed practically no catalyst
degradation, after 24 h, in all cases. Based on the results in
homogeneous phase, the trifluoromethyl-based chromium(III)
hybrid nanocomposite MNP@SiO2-4Cr was selected as
heterogeneous catalyst, to be applied in CO2 addition to styrene
oxide, under similar reaction conditions. Following a standard
procedure, the magnetic catalyst (490 mg, 0.0245 mmol Cr) was
introduced in a glass vial inside the autoclave, together with the
co-catalyst, PPNCl (0.0245 mmol). After pressurization with CO2
(10 bar), the reaction was conducted for 24 h, under vigorous
stirring. The hybrid catalyst MNP@SiO2-4Cr produced
a
conversion of 55% in 24 h, with close to full selectivity for the
formation of styrene carbonate (SI, Figure S8). Then, the
heterogeneous catalyst was recovered using an external magnet,
it was washed with CH3CN and CH2Cl2, dried under vacuum and
reused in the next run. Remarkably, the nanocomposite showed
a notable reusability in four consecutive cycles, without significant
loss of activity or selectivity for styrene carbonate (Figure 7). A
blank experiment was carried out, using the aminopropylsilyl-
functionalized magnetic nanoparticle (MNP@SiO2-NH2) as
catalyst but practically no conversion (<1%) was observed after
24 h, which indicates that the immobilized Cr(III)-porphyrin is
effectively acting as the reaction's catalyst. In sum, these results
show that the hybrid Cr(III)-porphyrin magnetic nanocomposite
MNP@SiO2-4Cr is a stable and reusable catalyst for CO2
cycloaddition to styrene epoxide, with high selectivity for cyclic
carbonate formation.
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10.1002/cctc.201800397
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FULL PAPER
In the search of efficient methodologies for the "direct"
transformation of olefins into cyclic carbonates, different
approaches were studied. Sequential epoxidation/CO2 addition
reactions were first appraised in homogeneous phase, with
styrene being selected as model olefin substrate.
Initially, hydrogen peroxide was selected as the oxidant and the
epoxidation step was carried out with the manganese(III)-
porphyrin catalyst 6Mn, under the conditions presented in Table
1. After 45 min, the solvent was partially evaporated and the
resulting mixture was transferred, without any further purification,
to a stainless steel autoclave containing the chromium(III)-
porphyrin catalyst 2Cr and the co-catalyst PPNCl. The
subsequent CO2 addition proceeded along 24 h, under the
conditions described in Table 3 (10 bar CO2, 80 ºC), leading to
the formation of the desired styrene carbonate in 70% yield (Table
4, entry 1). Therefore, the scope of this sequential methodology
was expanded to a set of different aryl and alkyl olefins, including
4-chlorostyrene, 4-methylstyrene, 2-vinylnaphthalene and 1-
hexene. Remarkably, full conversion of the initial olefin was
achieved in all cases, with moderate to good selectivity for cyclic
carbonate formation (47-70%) (Table 4, entries 2-5) and
(SI, Figures S9-11). The only exception was obtained with 4-
methylstyrene, for which a complex mixture of benzylic oxidation
products, formed during the epoxidation step, was observed,
leading to very low selectivity (<1%) for cyclic carbonate formation
(Table 4, entry 3). A different approach was then appraised, using
molecular oxygen as the oxidant (and isobutyraldehyde as co-
reductant), again with manganese(III)-porphyrin 6Mn as the
epoxidation catalyst, under the reaction conditions described in
Table 1. After 90 min at 25 ºC under O2 bubbling, the
chromium(III)-porphyrin catalyst 2Cr and the co-catalyst PPNCl,
was added. The subsequent CO2 addition proceeded along 24 h,
under the conditions described in Table 3 (10 bar CO2, 80 ºC).
GC/MS analysis of the crude showed the complete conversion of
the initial olefin substrate but a complex mixture of products was
obtained, without any evidence of cyclic carbonate formation. This
was attributed to the epoxide ring opening in the presence of
isobutyric acid formed in the first step.
Figure 7. Recycling experiments of MNP@SiO2-4Cr in CO2 addition to styrene
oxide.
Sequential epoxidation/CO2 cycloaddition
Table 4. Sequential epoxidation/CO2 cycloaddition, catalyzed by
homogeneous Mn(III) (6Mn) and Cr(III)-porphyrin (2Cr) catalysts.[a]
Entry
Substrate
Conversion[b]
(%)
Product
(%)
1
99
99
70
2
3
47
Therefore, from a critical analysis of the above results and aiming
at the development of efficient and reusable catalytic system to
sequentially promote the "direct" transformation of olefins into
cyclic carbonate, the hybrid metalloporphyrin magnetic
nanocomposites MNP@SiO2-8Mn and MNP@SiO2-4Cr were
combined and evaluated as a heterogeneous bimetallic dual
catalytic system for styrene epoxidation with molecular oxygen,
followed by CO2 cycloaddition (Figure 8).
99
<1
68
4
5
93
99
48
[a] Reaction conditions for epoxidation: catalyst, styrene, NH4OAc (1 : 600 :
387), CH3CN (20 mL), T = 25 ºC, t = 45 min; H2O2 (30% w/w) solution in
CH3CN (1:10) was added to the reaction mixture (2.25 mL aliquots every 15
min). Reaction conditions for CO2 addition reaction: catalyst and co-catalyst
(PPNCl): 0.07 mol%; T = 80 °C; P (CO2) = 10 bar; t = 24 h [b] Conversions
calculated by GC based on chlorobenzene as internal standard.
Figure 8. Sequential heterogeneous bimetallic dual catalytic system for direct
transformation of styrene into styrene cyclocarbonate using O2 and CO2.
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10.1002/cctc.201800397
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So, a mixture containing the two hybrid materials MNP@SiO2-
8Mn (66 mg, 8.16×10-4 mmol) and MNP@SiO2-4Cr (122 mg,
6.08×10-3 mmol Cr) was placed inside the reaction vessel. The
epoxidation reaction was carried out using molecular oxygen as
the oxidant and isobutyraldehyde as the co-reductant, under the
reaction conditions described in Table 2. After 140 minutes, the
magnetic hybrid catalyst (containing both Mn(III) and Cr(III)-
porphyrin nanoparticles) was collected in the reactor walls with an
external magnet and the reaction crude was treated with an
aqueous solution of sodium hydrogen carbonate to remove the
isobutyric acid formed as side-product. After separation, the
organic phase was transferred to the autoclave, containing
already the recovered magnetic catalysts and the co-catalyst
PPNCl. The reactor was then pressurized with CO2 (10 bar) and
cycloaddition step was conducted at 80 ° C, for 24 h. GC/MS
analyses determined complete conversion of the olefin, with
formation of styrene carbonate as the major product (up to 52%).
After the catalyst's recovery using an external magnet, the hybrid
material was washed several times with different solvents, dried
under vacuum and reused in the next run, which involved both
epoxidation and CO2 addition as sequential steps. Remarkably,
the hybrid material could be reused in several additional
consecutive sequential epoxidation/CO2 addition cycles, without
loss of catalytic activity and just a slight decrease of selectivity for
the formation of cyclic carbonate (Figure 9), which demonstrated
the recyclability of this heterobimetallic dual catalytic system.
From the final product selectivity we may infer that the mechanism
of the overall sequential reaction should be similar to the one
described for individual steps, where Mn(V)=O oxo species is the
epoxidation active species, obtained by Mukayiama
oxygen/aldehyde activation mechanism, and the CO2 addition to
the epoxide is catalyzed by the Cr(III) porphyrin (stronger Lewis
acid), assisted by the nucleophile PPNCl as previously described
by some of us.[83]
homogeneous phase have allowed us to conclude that,
regardless of the oxidant used (molecular oxygen or hydrogen
peroxide), the manganese(III) porphyrins are more active and
selective than their chromium(III) counterparts. Furthermore,
using O2 as the oxidant, the catalyst 6Mn (MnOAc-TDCPP) was
shown to be the most active, selective and stable epoxidation
catalyst. On the other hand, chromium(III) metalloporphyrins
proved to be the most active catalysts for CO2 addition to styrene
oxide, among the synthesized metalloporphyrins, the best results
being obtained with 2Cr (CrCl-pCF3TPP). Within our main goal of
developing sustainable chemical processes, the most promising
catalysts for each individual reaction were immobilized in
magnetic nanoparticles, to obtain the corresponding reusable
heterogeneous hybrid catalysts, which were characterized by
several physical/chemical techniques.
Although the use of H2O2 as the oxidant, in homogeneous phase,
has allowed the direct transformation of a set of different olefins
into the respective cyclic carbonates in good yields, using the
catalysts 6Mn and 2Cr in each epoxidation and CO2 cycloaddition
steps, respectively, the corresponding heterogeneous catalysts
were shown to lose significant activity after each recycling
experiment. Advantageously, the hybrid catalyst MNP@SiO2-
8Mn presented a good performance in styrene epoxidation using
O2 as oxidant, maintaining its efficiency in five consecutive cycles.
Remarkable, for the first time we developed an efficient and
reusable heterobimetallic catalytic system, through appropriate
combination of two hybrid materials, MNP@SiO2-8Mn and
MNP@SiO2-4Cr, to sequentially promote the transformation of
styrene into epoxide followed by the CO2 cycloaddition reaction.
This dual catalyst could be recycled and reused in three
consecutive cycles without significant loss of activity or selectivity.
Studies on the preparation of immobilized catalysts, with different
metals and different ligands are underway in our laboratory, with
a view to the development and optimization of tandem (one-pot)
oxidative carboxylation processes.
Experimental Section
Reagents and solvents were purchased from Sigma-Aldrich (Portugal) and
Fluorochem (England). Commercial styrene oxide was distilled prior to use.
1H-NMR spectra were recorded on a Bruker Avance III spectrometer, or a
Bruker DRX-400 spectrometer, both operating at 400.13 MHz (chemical
shifts are expressed in ppm using CDCl3 as solvent). The MALDI-TOF MS
data were obtained on a Bruker Daltonics Flex Analysis apparatus. The
UV–vis absorption spectra, in solution, were recorded on a Hitachi U-2010
and the absorption spectra of solid samples were obtained by diffuse
reflectance using a Cary 5000 UV-Vis-NIR spectrophotometer equipped
with an integrating sphere. The infrared spectra were obtained using a Pike
Miracle spectrometer and each spectrum were performed with a resolution
of 4 cm-1 (64 scans). The samples were pressed into thin wafers (20-25
mg cm-2) and heated in an IR glass cell up to 160 °C using a heating rate
of 10 K min-1 during 1h, under vacuum (10 Pa) before spectra acquisition
in transmission mode. A Philips CM 200 apparatus (accelerating voltage
of 200 kV) was used for TEM analyses and size distributions of the hybrid
materials were determined by a statistical size distribution via manual
analysis of enlarged images with Imagetool sware (Version 3.0)
programme. An Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
Thermo X Series apparatus was used for ICP analysis. Thermogravimetric
Figure 9. Recycling experiments of the dual catalytic system MNP@SiO2-
8Mn+MNP@SiO2-4Cr in styrene sequential epoxidation/CO2 addition.
Conclusions
The work presented herein allowed the development of active and
selective
metalloporphyrin-based
homogeneous
and
heterogeneous catalysts for epoxidation/CO2 addition sequential
reactions, aiming at the direct transformation of olefins into cyclic
carbonates. Studies of the styrene epoxidation reaction in
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10.1002/cctc.201800397
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FULL PAPER
analyses were obtained using a Parkin-Elmer STA6000 simultaneous
TG/DSC instrument from 25°C to 800 °C as maximum temperature. HP-
Agilent 6890 chromatographer, equipped with ionization detector (FID)
was used for gas chromatography analysis using chlorobenzene as
internal standard. GC-MS spectra were obtained in a Hewlett-Packard
5973 MSD spectrometer, using EI (70 eV), coupled to a Hewlett-Packard
Agilent 6890 chromatographer, equipped with a HP-5 MS column (30 m ×
0.25 mm × 0.25 μm). A Brucker Microtof instrument was used for mass
spectral analyses.
(III) acetate (3Mn) in 78% yield (292 mg, 0.28 mmol). HRMS (ESI-FIA-
TOF): calcd. for C50H26F12N5O4Mn [M-OAc]: 984.1041; found: 984.0883.
2-Nitro-5,10,15,20-tetra(4-trifluoromethylphenyl)porphyrinato
chromium(III) chloride (4Cr)
Chromium(II) chloride (181 mg, 1.48 mmol) was added to a round bottom
flask containing 10 (350 mg, 0.37 mmol) dissolved in dimethylformamide
(20 mL). The reaction was kept under stirring, at 150 °C for 5 h. Finally,
the crude was concentrated under vacuum and washed with a saturated
solution of sodium hydrogen carbonate (2×), water (2×) and dried with
anhydrous sodium sulfate. The crude product was purified using silica gel
column chromatography with ethyl acetate as eluent yielding 2-nitro-
Synthesis of metalloporphyrin catalysts
The symmetric porphyrins 5,10,15,20-tetra(2,6-difluorophenyl) porphyrin
(TDFPP), 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrin (TDCPP) and
5,10,15,20-tetra(4-trifluoromethylphenyl) porphyrin (p-CF3TPP), as well as
5,10,15,20-tetra(4-trifluoromethylphenyl)porphyrinatochromium
(III)
chloride (4Cr) in 89% yield (335 mg, 0.33 mmol). HRMS (ESI-FIA-TOF):
calcd. for C48H23ClCrF12N5O2 [M+1]: 1017.0754; found: 1017.0837
the
non-symmetric
5-(4-aminophenyl)-10,15,20-tri(2,6-
dichlorophenyl)porphyrin (NH2-TDCPP) were prepared according to our
optimized synthetic methods.[51,88-91] Then, the free-base porphyrins were
reacted with the desired metal salts (manganese(II) acetate tetrahydrate
or chromium(II) chloride), following literature procedures, to afford the
metalloporphyrin complexes 1Mn, 2Cr, 5Mn, 6Mn, 7Cr, 8Mn and 9Cr.
Their characterization data was in agreement with the reported
literature.[82,83,93,102]
Preparation of hybrid metalloporphyrin magnetite nanocomposites
In a round bottom flask, the aminopropylsilyl-functionalized magnetite
material MNP@SiO2-NH2 (1 g), previously prepared as described
elsewhere, was added to a solution of 3Mn (230 mg, 0.22 mmol) or 4Cr
(250 mg, 0.24 mmol) and cesium carbonate (310 mg, 0.95 mmol) in dry
1,2-dimethoxyethane (50 mL). The mixtures were heated until 85°C for 24
h. Then, the magnetic solid materials were collected using an external
magnet and washed several times with acetonitrile, ethyl acetate and
dichloromethane to rinse away excess of non-immobilized
metalloporphyrins. Finally, the resulting hybrid metalloporphyrin magnetic
nanocomposites MNP@SiO2-3Mn and MNP@SiO2-4Cr were dried under
vacuum for 48 h. A similar procedure was adopted to prepare the
MNP@SiO2-8Mn,[51] through reaction of 8Mn with chloropropylsilyl-
functionalized magnetite nanoparticles.[103]
2-Nitro-5,10,15,20-tetra(4-
trifluoromethylphenyl)porphyrinatocopper(II) (9Cu)
A solution of copper(II) nitrate trihydrate (0.27 g, 1.12 mmol) in acetic
anhydride/acetic acid mixture (50/10 mL) was added to a chloroform
solution (500 mL) of 5,10,15,20-tetra-(4-trifluoromethylphenyl)porphyrin
(p-CF3TPP) (500 mg, 0.56 mmol). The reaction was conducted at 60 °C
for 24 h. Then, the solution was concentrated under vacuum and washed
with a saturated solution of sodium hydrogen carbonate (2×), water (2×)
and dried with anhydrous sodium sulfate. The crude was then purified by
silica gel column chromatography, using dichloromethane:n-hexane (2:1)
Procedure for catalytic epoxidation with O2
A dichloromethane solution (2 mL), containing the olefin substrate (0.5
mmol), the metalloporphyrin catalyst (4.7×10-5 mmol metal),
isobutyraldehyde (0.18 g, 2.5 mmol) and chlorobenzene (21 mg, 0.19
mmol) was introduced into a stainless steel autoclave. Then, the reaction
was stirred, at 25 ˚C, under oxygen bubbling, for the appropriate time (90
min with homogeneous catalysts or 140 min with heterogeneous catalysts.
Conversion and selectivity were determined by GC, using chlorobenzene
as internal standard. The products' identification was performed by GC/MS
and GC analysis against standards.
as
the
eluent.
The
complex
2-nitro-5,10,15,20-tetra-(4-
trifluoromethylphenyl)porphyrinato copper(II) (9Cu) was isolated in 84 %
yield (466 mg, 0.47 mmol). HRMS (ESI-FIA-TOF): calcd. for
C48H23F12N5O2Cu 992.0956; found: 992.0954.
2-Nitro-5,10,15,20-tetra(4-trifluoromethylphenyl)porphyrin (10)
A solution of sulfuric acid 98% (10 mL) was added dropwise to a
chloroform solution (200 mL) of 9Cu (500 mg, 0.50 mmol). The reaction
was kept at 25 °C for 1 h. Then, the crude was carefully neutralized with a
saturated solution of sodium bicarbonate and distilled water. The organic
solution was dried with anhydrous sodium sulfate. After filtration and
solvent evaporation, the crude was purified by silica gel column
chromatography, using dichloromethane:n-hexane (2:1) as the eluent. The
Procedure for catalytic epoxidation with H2O2
The olefin substrate (4.5 mmol), ammonium acetate (225 mg, 2.91 mmol),
the metalloporphyrin catalyst (7.48×10-3 mmol metal) and chlorobenzene
(44 mg, 0.39 mmol) were dissolved in acetonitrile (20 mL). The mixture
was introduced into a glass vial and a hydrogen peroxide (2 mmol) solution
(30% w/w), diluted with acetonitrile (1:10), was slowly added to the reaction
mixture, in 2.25 mL aliquots, until complete substrate conversion. The
reaction was conducted at 25 ºC, under stirring, for the desired time (45
min with homogeneous catalysts or 24 h with heterogeneous catalysts).
Conversion and selectivity were determined by GC, using chlorobenzene
as internal standard. The products' identification was performed by GC/MS
and GC analysis against standards.
2-nitro-5,10,15,20-tetra(4-trifluoromethylphenyl)porphyrin
(10)
was
isolated in 88% yield (415 mg, 0.44 mmol). 1H NMR (400.13 MHz, CDCl3,
298 K): δ = 9.01 (s, 1H, β-H), 8.96– 8.86 (m, 4H, β-H), 8.70 – 8.67 (m, 2H,
β-H), 8.37 – 8.32 (m, 8H, Ar-H), 8.09 – 8.06 (m, 6H, Ar-H), 7.99 (d, J = 8.0
Hz, 2H, Ar-H), -2.68 ppm (s, 2H). HRMS (ESI-FIA-TOF): calcd. for
C48H25F12N5O2 931.1817; found: 932.1889.
2-Nitro-5,10,15,20tetra(4trifluoromethylphenyl)porphyrinato
manganese(III) acetate (3Mn)
Procedure for catalytic CO2 addition to epoxides
Manganese(II) acetate tetrahydrate (880 mg, 3.6 mmol) was added to a
round bottom flask containing 10 (300 mg, 0.32 mmol), dissolved in
dimethylformamide (20 mL). The reaction was kept under stirring at 150 °C
for 4h. The solution was then concentrated under vacuum and washed
with a saturated solution of sodium hydrogen carbonate (2×), water (2×)
and dried with anhydrous sodium sulfate. The crude was purified by silica
gel column chromatography, using ethyl acetate as the eluent, providing
2-nitro-5,10,15,20-tetra(4-trifluoromethylphenyl)porphyrinato manganese
The metalloporphyrin catalyst (2.45×10-2 mmol) and the co-catalyst PPNCl
(2.45×10-2 mmol) (when indicated) were placed inside a 100 mL stainless
steel autoclave and kept for 3 h under vacuum, at 80 °C. Then, styrene
epoxide (4 mL, 35 mmol), previously dried over alumina and stored under
inert atmosphere, was introduced via cannula into the autoclave. The
autoclave was pressurized with CO2 (10 bar) and the reaction was
conducted under stirring, at 80 ºC, for 24 h. At the end, the autoclave was
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10.1002/cctc.201800397
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cooled in an ice bath and slowly depressurized. Conversion was
determined by GC, using chlorobenzene as internal standard and
selectivity was determined by 1H NMR, through integral ratio.
solution (30 mL). After phase separation, the organic phase was dried over
alumina and introduced, via cannula, inside the stainless steel autoclave
containing the recovered hybrid catalysts. Then, the reactor was
pressurized with CO2 (10 bar) and the reaction was conducted at 80 ºC for
24 h. At the end, the autoclave was cooled and slowly depressurized.
Finally, the mixture of magnetic catalysts (MNP@SiO2-8Mn and
MNP@SiO2-4Cr) was separated from the reaction mixture using an
external magnet. The recovered solid material was washed with
dichloromethane (4 mL) (3×), dried in vacuum for 2 h at 60 °C and reused
in the next run. Conversion was determined by GC, using chlorobenzene
Recycling and reuse of heterogeneous magnetic catalysts
After the first run of each catalytic experiment, the heterogeneous catalysts
MNP@SiO2-3Mn, MNP@SiO2-8Mn or MNP@SiO2-4Cr were steadily
separated from the crude mixtures, using an external magnet, followed by
decantation of supernatant solution. Then, the solid magnetic material was
washed with CH2Cl2 (4 mL) (3×) and CH3CN (4 mL) (3×), dried under
vacuum, at 60 °C, for 2h and reused in the next run.
1
as internal standard and selectivity was determined by H NMR, through
peak integral ratio.
Procedure
for
homogeneous
sequential
epoxidation/CO2
cycloaddition with O2 as the oxidant
A dichloromethane solution (2 mL) containing styrene (1 mL, 8.69 mmol),
the catalyst 6Mn (0.8 mg, 8.16×10-4 mmol), isobutyraldehyde (3.1 g, 43.4
mmol), and chlorobenzene (21 mg, 0.19 mmol) was introduced in an
autoclave. The reaction was conducted with stirring at 25 ˚C, under oxygen
bubbling, for 4 h. Meanwhile, the catalyst 2Cr (5.9 mg, 6.08×10-3 mmol)
and PPNCl (6.08×10-3 mmol) were placed inside a 100 mL stainless steel
autoclave and kept for 3 h under vacuum, at 80 °C. Then, the epoxidation
crude mixture was transferred via cannula into the autoclave. The reactor
was pressurized with CO2 (10 bar) and the reaction was conducted at 80
ºC for 24 h. At the end, the autoclave was cooled in an ice bath and slowly
depressurized. The products' identification was performed by GC/MS and
GC analysis against standards. Conversion was determined by GC, using
chlorobenzene as internal standard and selectivity was determined by 1H
NMR, through peak integral ratio.
Acknowledgements
The authors thanks Coimbra Chemistry Centre and SunStorage -
Harvesting and storage of solar energy project through Project
Nos. PEst-OE/QUI/UI0313/2014 and POCI-01-0145-FEDER-
016387, respectively. L.D.D thanks CNPq - Brasil (Conselho
Nacional de Desenvolvimento Científico e Tecnológico) for his
PhD grant 232620/2014-8/GDE. R.M.B.C., C.A.H., and M.J.F.C.
are grateful to FCT for post-doc grants SFRH/BPD/100537/2014,
PTDC/QEQ-MED/3521/2014,
and
SFRH/BPD/99698/2014,
respectively. The authors also thanks TAIL-UC facility funded
under QREN-Mais Centro project ICT 2009_02_012_1890 for
TG-DSC analysis.
Procedure
for
homogeneous
sequential
epoxidation/CO2
cycloaddition with H2O2 as the oxidant
The olefin substrate (4.5 mmol), ammonium acetate (225 mg, 2.91 mmol),
the catalyst 6Mn (7.5 mg, 7.48×10-3 mmol) and chlorobenzene (44 mg,
0.39 mmol), were dissolved in CH3CN (20 mL). The mixture was then
introduced into an autoclave and an aqueous hydrogen peroxide (2 mmol)
solution (30% w/w), diluted with acetonitrile (1:10), was slowly added to
the reaction mixture, in 2.25 mL aliquots, every 15 min. The reaction was
conducted with stirring at 25 ºC, for 45 min. Then, the crude mixture was
dried over anhydrous sodium sulfate, concentrated to a total volume of 2.5
mL and stored under inert atmosphere. Meanwhile, the catalyst 2Cr (3.0
mg, 3.15×10-3 mmol) and the co-catalyst PPNCl (1.8 mg, 3.15×10-3 mmol)
were placed inside a 100 mL stainless steel autoclave and kept for 3 h
under vacuum, at 80 °C. Then, the epoxidation crude mixture was
transferred via cannula into the autoclave. The reactor was pressurized
with CO2 (10 bar) and the reaction was conducted at 80 ºC for 24 h. At the
end, the autoclave was cooled in an ice bath, and slowly depressurized.
Conversion was determined by GC, using chlorobenzene as internal
standard and selectivity was determined by 1H NMR, through peak integral
ratio.
Keywords: metalloporhyrin • hybrid magnetic nanoparticles •
epoxidation • CO2 cycloaddition • sequential process
[1]
[2]
X. Lim, Nature 2015, 526, 628-630.
J. A. Martens, A. Bogaerts, N. De Kimpe, P. A. Jacobs, G. B. Marin, K.
Rabaey, M. Saeys, S. Verhelst, ChemSusChem 2017, 10, 1039-1055.
Q. Liu, L. Wu, R. Jackstell, M. Beller, Nature Commun. 2015, 6, 5933.
J. Artz, T. E. Mꢀller, K. Thenert, Chem. Rev. 2018, 118, 434-504.
E. Alper, O. Y. Orhan, Petroleum 2017, 3, 109-126.
[3]
[4]
[5]
[6]
E. Vessally, M. Babazadeh, A. Hosseinian, S. Arshadi, L. Edjlali, J. CO2
Util. 2017, 21, 491-502.
[7]
[8]
[9]
Q.-W. Song, Z.-H. Zhou, L.-N. He, Green Chem. 2017, 19, 3707-3728.
M. Aresta, A. Dibenedetto, E. Quaranta, J. Catal. 2016, 343, 2-45.
K. M. K. Yu, I. Curcic, J. Gabriel, S. C. E. Tsang, ChemSusChem 2008,
1, 893-899.
[10] R. R. Shaikh, S. Pornpraprom, V. D’Elia, ACS Catal. 2018, 8, 419-450.
[11] X.-D. Lang, L.-N. He, Chem. Rec. 2016, 16, 1337-1352.
[12] V. B. Saptal, B. M. Bhanage, Curr. Opin. Green Sustainable Chem. 2017,
3, 1-10.
Procedure
for
heterogeneous
sequential
epoxidation/CO2
[13] C. Martín, G. Fiorani, A. W. Kleij, ACS Catal. 2015, 5, 1353-1370.
[14] J. H. Clements, Ind. Eng. Chem. Res. 2003, 42, 663-674.
[15] A. A. G. Shaikh, S. Sivaram, Chem. Rev. 1996, 96, 951-976.
[16] T. Sakakura, K. Kohno, Chem. Commun. 2009, 1312-1330.
[17] M. North, R. Pasquale, C. Young, Green Chem. 2010, 12, 1514-1539.
[18] C. J. Whiteoak, A. W. Kleij, Synlett. 2013, 24, 1748-1756.
[19] H. Büttner, L. Longwitz, J. Steinbauer, C. Wulf, T. Werner, Top. Curr.
Chem. 2017, 375, 50.
cycloaddition
Styrene (1 mL, 8.69 mmol), the hybrid catalysts MNP@SiO2-8Mn (66 mg,
8.16×10-4 mmol Mn) and MNP@SiO2-4Cr (122 mg, 6.08×10-3 mmol Cr),
isobutyraldehyde (3.1 g, 43.4 mmol), chlorobenzene (0.4 g, 3.32 mmol)
and dichloromethane were introduced into a glass vial, inside an autoclave
and the reaction was conducted with stirring at 25 ˚C, under oxygen
bubbling, for 4 h. After this period, the hybrid solid material (containing both
catalysts MNP@SiO2-8Mn and MNP@SiO2-4Cr) was collected in the
autoclave walls, using an external magnet, and the liquid was decanted.
Then, PPNCl (6.08×10-3 mmol) was added to the stainless steel autoclave
containing the hybrid magnetic catalysts and the reactor was kept under
vacuum, at 80 °C, for 3 h. Next, the crude mixture obtained in the
epoxidation step was treated with a saturated sodium hydrogen carbonate
[20] M. Cokoja, M. E. Wilhelm, M. H. Anthofer, W. A. Herrmann, F. E. Kuhn,
ChemSusChem 2015, 8, 2436-2454.
[21] C. J. Whiteoak, A. Nova, F. Maseras, A. W. Kleij, ChemSusChem 2012,
5, 2032-2038.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201800397
ChemCatChem
FULL PAPER
[22] M. Alves, B. Grignard, R. Mereau, C. Jerome, T. Tassaing, C.
Detrembleur, Catal. Sci. Technol. 2017, 7, 2651-2684.
[23] Q. He, J. W. O'Brien, K. A. Kitselman, L. E. Tompkins, G. C. T. Curtis, F.
M. Kerton, Catal. Sci. Technol., 2014, 4, 1513-1528.
[24] V. B. Saptal, B. M. Bhanage, ChemCatChem 2016, 8, 244-250.
[25] A. Decortes, A. M. Castilla, A. W. Kleij, Angew. Chem. Int. Ed. 2010, 49,
9822-9837.
[59] P. J. Thomassen, S. Varghese, E. J. A. Bijsterveld, P. Thordarson, J. A.
A. W. Elemans, A. E. Rowan, R. J. M. Nolte, Eur. J. Org. Chem. 2015,
5246-5253.
[60] J. W. Brown, Q. T. Nguyen, T. Otto, N. N. Jarenwattananon, S. Glöggler,
L.-S. Bouchard, Catal. Commun. 2015, 59, 50-54.
[61] S. Rayati, F. Nejabat, New J. Chem. 2017, 41, 7987-7991.
[62] X.-L. Yang, C.-D. Wu, Inorg. Chem. 2014, 53, 4797-4799.
[63] L. Cuesta-Aluja, A. M. Masdeu-Bultó, ChemistrySelect 2016, 1, 2065-
2070.
[26] X.-B. Lu, D. J. Darensbourg. Chem. Soc. Rev. 2012, 41, 1462-1484.
[27] V. D´Elia, J. D. A. Pelletier, J.-M. Basset, ChemCatChem 2015, 7, 1906-
1917.
[64] J. Sun, L. Liang, J. Sun, Y. Jiang, K. Lin, X. Xu, R. Wang, Catal. Surv.
Asia. 2011, 15, 49-54.
[28] J. W. Comerford, I. D. V. Ingram, M. North, X. Wu, Green Chem. 2015,
17, 1966-1987.
[65] N. Eghbali, C.-J. Li, Green Chem. 2007, 9, 213-215.
[66] P. Ramidi, C. M. Felton, B. P. Subedi, H. Zhou, Z. R. Tian, Y. Gartia, B.
S. Pierce, A. Ghosh, J. CO2 Util. 2015, 9, 48-57.
[29] X.-H. Ji, N.-N. Zhu, J.-G. Ma, P. Cheng, Dalton Trans. 2018, 47, 1768-
1771.
[30] S.-S. Yu, X.-H. Liu, J.-G. Ma, Z. Niu, P. Cheng, J. CO2 Util. 2016, 14,
122-125.
[67] J. Sun, S. Fujita, B. M. Bhanage, M. Arai, Catal. Today 2004, 93-95, 383-
388.
[31] M. North, P. Villuendas, ChemCatChem 2012, 4, 789-794.
[32] Y. Chen, R. Luo, Q. Xu, J. Jiang, X. Zhou, H. Ji, ACS Sustainable Chem.
Eng. 2018, 6, 1074-1082.
[68] C. C. Rocha, T. Onfroy, F. Launay, C. R. Chimie 2015, 18, 270-276.
[69] M. Aresta, E. Quaranta, A. Ciccarese, J. Mol. Catal. 1987, 41, 355-359.
[70] D. Bai, H. Jing, Green Chem. 2010, 12, 39-41.
[71] M. Aresta, A. Dibenedetto, J. Mol. Catal. A: Chem. 2002, 182-183, 399-
409.
[33] Y. Qin, H. Guo, X. Sheng, X. Wang, F. Wang, Green Chem. 2015, 17,
2853-2858.
[34] C. Maeda, S. Sasaki, T. Ema, ChemCatChem 2017, 9, 946-949.
[35] Y. Chen, R. Luo, Q. Xu, W. Zhang, X. Zhou, H. Ji, ChemCatChem 2017,
9, 767-773.
[72] M. Aresta, A. Dibenedetto, I. Tommasi, Appl. Organometal. Chem. 2000,
14, 799-802.
[73] D. Xiang, X. Liu, J. Sun, F.-S. Xiao, J. Sun, Catal. Today. 2009, 148, 383-
388.
[36] X. Jiang, F. Gou, X. Fu, H. Jing, J. CO2 Util. 2016, 16, 264-271.
[37] A. Farhadian, M. B. G. Afshani, A. B. Miyardan, M. R. Nabid, N. Safari,
ChemistrySelect 2017, 2, 1431-1435.
[74] J. Sun, S. Fujita, F. Zhao, M. Hasegawa, M. Arai, J. Catal. 2005, 230,
398-405.
[38] Z. Dai, Q. Sun, X. Liu, C. Bian, Q. Wua, S. Pan, L. Wang, X. Meng, F.
Deng, F.-S. Xiao, J. Catal. 2016, 338, 202-209.
[75] K. Jasiak, T. Krawczyk, M. Pawlyta, A. Jakóbik-Kolon, S. Baj, Catal. Lett.
2016, 146, 893-901.
[39] A. Chen, P. Ju, Y. Zhang, J. Chen, H. Gao, L. Chen, Y. Yu, RSC Adv.
2016, 6, 96455-96466.
[76] J.-L. Wang, J.-Q. Wang, L.-N. He, X.-Y. Dou, F. Wu, Green Chem. 2008,
10, 1218-1223.
[40] F. Zadehahmadi, F. Ahmadi, S. Tangestaninejad, M. Moghadam, V.
Mirkhani, I. Mohammadpoor-Baltork, R. Kardanpour, J. Mol. Catal. A:
Chem. 2015, 398, 1-10.
[77] J. Sun, S. Fujita, B. M. Bhanage, M. Arai, Catal. Commun. 2004, 5, 83-
87.
[78] S. L. H. Rebelo, M. M. Q. Simões, M. G. P. M. S. Neves, A. M. S. Silva,
J. A. S. Cavaleiro, A. F. Peixoto, M. M. Pereira, M. R. Silva, J. A. Paixão,
A. M. Beja, Eur. J. Org. Chem. 2004, 4778-4787.
[41] X. Sheng, H. Guo, Y. Qin, X. Wang, F. Wang, RSC Adv. 2015, 5, 31664-
31669.
[42] D. Bai, Q. Wang, Y. Song, B. Li, H. Jing, Catal. Commun. 2011, 12, 684-
688.
[79] S. L. H. Rebelo, M. M. Pereira, M. M. Q. Simões, M. G. P. M. S. Neves,
J. A. S. Cavaleiro, J. Catal. 2005, 234, 76-87.
[43] C. Maeda, J. Shimonishi, R. Miyazaki, J. Hasegawa, T. Ema, Chem. Eur.
J. 2016, 22, 6556-6563.
[80] R. de Paula, M. M. Q. Simões, M. G. P. M. S. Neves, J. A. S. Cavaleiro,
J. Mol. Catal. A: Chem. 2011, 345, 1-11.
[44] J. He, J. Ling, P. Chiu, Chem. Rev. 2014, 114, 8037-8128.
[45] F. Cavani, J. H. Teles, ChemSusChem 2009, 2, 508-534.
[46] A. Fingerhut, O. V. Serdyuk, S. B. Tsogoeva, Green Chem. 2015, 17,
2042-2058.
[81] A. Franke, C. Fertinger, R. Eldik, Chem. Eur. J. 2012, 18, 6935-6949.
[82] L. Cuesta-Aluja, J. Castilla, A. M. Masdeu-Bultó, C. A. Henriques, M. J.
F. Calvete, M. M. Pereira, J. Mol. Catal. A: Chem. 2016, 423, 489-494.
[83] R. M. B. Carrilho, L. D. Dias, R. Rivas, M. M. Pereira, C. Claver, A. M.
Masdeu-Bultó, Catalysts 2017, 7, 210.
[47] S.-C. Chua, X. Xu, Z. Guo, Process Biochem. 2012, 47, 1439-1451.
[48] Modern Oxidation Methods, J.-E. Bäckvall (Ed.), Wiley-VCH Verlag
GmbH & Co. KGaA, Weinheim, 2004.
[84] S. Mang, A. I. Cooper, M. E. Colclough, N. Chauhan, A. B. Holmes,
Macromolecules 2000, 33, 303-308.
[49] J. C. Barona-Castaño, C. C. Carmona-Vargas, T. J. Brocksom, K. T. de
Oliveira, Molecules 2016, 21, 310.
[85] A. R. Almeida, R. M. B. Carrilho, A. F. Peixoto, A. R. Abreu, A. Silva, M.
M. Pereira, Tetrahedron 2017, 73, 2389-2395.
[50] A. Farokhi, H. Hosseini-Monfared, New J. Chem. 2016, 40, 5032-5043.
[51] L. D. Dias, R. M. B. Carrilho, C. A. Henriques, G. Piccirillo, A. Fernandes,
L. M. Rossi, M. F. Ribeiro, M. J. F. Calvete, M. M. Pereira, J. Porphyrins
Phthalocyanines 2018, 22, 2-11.
[86] L. Damas, G. N. Costa. J. C. Ruas, R. M. B. Carrilho, A. R. Abreu, G.
Aquino, M. J. F. Calvete, M. Pineiro, M. M. Pereira, Curr. Microwave
Chem. 2015, 2, 53-60.
[87] M. M. Pereira, A. C. B. Neves, M. J. F. Calvete, L. D. Dias, A. Fernandes,
Catal. Today, 2013, 218, 99-106.
[52] R. A. Baglia, J. P. T. Zaragoza, D. P. Goldberg, Chem. Rev. 2017, 117,
13320-13352.
[88] R. A. W. Johnstone, M. L. P. J. Nunes, M. M. Pereira, A. M. A. R.
Gonsalves, A. C. Serra, Heterocycles 1996, 43, 1423-1437.
[89] C. A. Henriques, S. M. A. Pinto, G. L. B. Aquino, M. Pineiro, M. J. F.
Calvete, M. M. Pereira, ChemSusChem 2014, 7, 2821-2824.
[90] M. Silva, A. Fernandes, S. S. Bebiano, M. J. F. Calvete, M. F. Ribeiro, H.
D. Burrows, M. M. Pereira, Chem. Commun. 2014, 50, 6571-6573.
[91] M. J. F. Calvete, L. D. Dias, C. A. Henriques, S. M. A. Pinto, R. M. B.
Carrilho, M. M. Pereira, Molecules 2017, 22, 741.
[53] K. Berijani, H. Hosseini-Monfared, Inorg. Chim. Acta 2018, 471, 113-120.
[54] A. Farokhi, H. Hosseini Monfared, J. Catal. 2017, 352, 229-238.
[55] M. Zhao, C.-D. Wu, Catal. Commun. 2017, 99, 146-149.
[56] K. Berijani, H. Hosseini-Monfared, Mol. Catal. 2017, 433, 136-144.
[57] P. Sakthipriya, N. Ananthi, J. Porphyrins Phthalocyanines 2016, 20, 730-
737.
[58] T. Omagari, A. Suzuki, M. Akita, M. Yoshizawa, J. Am. Chem. Soc. 2016,
138, 499-502.
[92] P. Chen, M. H. Chisholm, J. C. Gallucci, X. Zhang, Z. Zhou, Inorg. Chem.
2005, 44, 2588-2595.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201800397
ChemCatChem
FULL PAPER
[93] D. Lahaye, K. Muthukumaran, C-H. Hung, D. Gryko, J. S. Rebouças, I.
Spasojevic, I. Batinic-Haberle, J. S. Lindsey, Bioorg. Med. Chem. 2007,
22, 7066-7086.
[100] B. B. Wentzel, P. L. Alsters, M. C. Feiters, R. J. M. Nolte, J. Org. Chem.
2004, 69, 3453-3464.
[101] C. Sun, B. Hu, Z. Liu, Chem. Eng. J. 2013, 232, 96-103.
[102] T. G. Traylor, A. R. Miksztal, J. Am. Chem. Soc. 1989, 111, 7443-7448.
[103] C. A. Henriques, S. M. A. Pinto, J. Pina, C. Serpa, A. Fernandes, L.
M. Rossi, M. F. Ribeiro, M. M. Pereira, M. J. F. Calvete, Dalton Trans.
2016, 45, 16211-16220.
[94] C. A. Henriques, A Fernandes, L. M. Rossi, M. F. Ribeiro, M. J. F. Calvete,
M. M. Pereira, Adv. Funct. Mater. 2016, 26, 3359-3368.
[95] L. M. Rossi, L. L. R. Vono, F. P. Silva, P. K. Kiyohara, E. L. Duarte, J. R.
Matos, Appl. Catal. A: Gen. 2007, 330, 139-144.
[96] J. Muzart, Chem. Rev. 1992, 92, 113-140.
[97] R. A. Baglia, J. P. T. Zaragoza, D. P. Goldberg, Chem. Rev. 2017, 117,
13320-13352.
[98] X. Huang, J. T. Groves, Chem. Rev. 2018, 118, 2491-2553.
[99] W. Nam, H. J. Kim, S. H. Kim, R. Y. N. Ho, J. S. Valentine, Inorg. Chem.
1996, 35, 1045-1049.
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Layout 1:
FULL PAPER
The search for more efficient
catalytic processes and CO2
industrial applications are key
Lucas D. Dias, Rui M. B. Carrilho*,
César A. Henriques, Mário J.F.Calvete,
Anna M. Masdeu-Bultó,
challenges
in
Chemistry:
Carmen Claver, Liane M. Rossi,
and Mariette M. Pereira*
Development of an efficient catalytic
system for valorization of CO2
through sequential transformation
epoxidation/CO2 cycloaddition of
simple olefins into valuable cyclic
carbonates
metalloporphyrin magnetic catalysts
is reported.
Page No. – Page No.
Hybrid-Metalloporphyrin Magnetic
Nanoparticles as Catalysts for
Sequential Transformation of
Alkenes and CO2 into Cyclic
Carbonates
by
hybrid
This article is protected by copyright. All rights reserved.