Thioglycerol-Stabilized Rhodium Nanoparticles in Biphasic Medium as Catalysts in Multistep Reactions

Article abstract of DOI:10.1002/ejic.202000451

Small rhodium nanoparticles (ca. 3.5 nm) were prepared by the decomposition of an organometallic precursor under hydrogen pressure in glycerol using 1-thioglycerol as stabilizer. Full characterization in the solid state [HR-TEM, EDX, XPS] showed a fcc structure for the Rh⁰/Rh^I nanoparticles capped with thiolate ligand. Reduction of different functionalities, including nitro groups and imines, was applied to tandem reductive amination of aldehydes with primary and secondary amines, and to the synthesis of N-substituted anilines from nitrobenzene. In addition, thiolate-capped RhNPs could be recovered and reused up to 5 runs without loss of activity nor selectivity.

Full text of DOI:10.1002/ejic.202000451

European Journal of Inorganic Chemistry
Accepted Article
Title: Thioglycerol-stabilized RhNPs in biphasic medium as catalysts in
multistep reactions
Authors: Alejandro Serrano-Maldonado, Antonio Reina, Benjamín
Portales-Martínez, and Itzel Guerrero-Ríos
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To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.202000451
Link to VoR: https://doi.org/10.1002/ejic.202000451
01/2020

10.1002/ejic.202000451
European Journal of Inorganic Chemistry
FULL PAPER
Thioglycerol-stabilized RhNPs in biphasic medium as catalysts in
multistep reactions
Alejandro Serrano-Maldonado,[a] Antonio Reina,[a] Benjamín Portales-Martínez[b] and Itzel Guerrero-
Ríos *[a]
[a]
M. Sc. A. Serrano-Maldonado, Dr. A. Reina and Dr. I. Guerrero-Ríos
Departamento de Química Inorgánica y Nuclear
Universidad Nacional Autónoma de México
Av. Universidad 3000, 04510, CDMX, México
E-mail: itzelgr@unam.mx
[b]
Dr. B. Portales-Martínez
CONACYT, Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Laboratorio Nacional de Conversión y Almacenamiento de Energía,
Instituto Politécnico Nacional, Calzada Legaría 694, Col. Irrigación, Ciudad de México, 11500, Mexico
Supporting information for this article is given via a link at the end of the document.
transformations, as several products can be obtained.[22,23]
Concerning RhNPs as catalysts, Jin and co-workers prepared
nanoparticles (2.1±0.3 nm) in polyethylene glycol ammonium-
based ionic liquids and applied them in hydroformylation and
tandem hydroaminomethylation reactions, using a biphasic
toluene/ionic liquid system, which formed one phase at high
temperatures.[24-26] Very recently, our group reported the
synthesis of RhNPs in ionic liquids stabilized by pyridine and
thiolates, showing the influence of the stabilizers on the
selectivity of hydrogenation reactions, especially in the formation
of amines through reductive amination reactions.[27,28]
Abstract: Small rhodium nanoparticles (ca. 3.5 nm) were prepared
by the decomposition of an organometallic precursor under
hydrogen pressure in glycerol using 1-thioglycerol as stabilizer. Full
characterization in the solid state ((HR)-TEM, EDX, XPS) showed a
fcc structure for the Rh(0)/Rh(I) nanoparticles capped with thiolate
ligand. Reduction of different functionalities, including nitro groups
and imines, was applied to tandem reductive amination of aldehydes
with primary and secondary amines, and to the synthesis of N-
substituted anilines from nitrobenzene. In addition, thiolate-capped
RhNPs could be recovered and reused up to 5 runs without loss of
activity nor selectivity.
Introduction
However, the few data available on the environmental impact of
ionic liquids, together with their high cost, compels us to search
for greener solvents. Thus, glycerol coming from biomass
appears as a suitable alternative.[29] Glycerol is a low-cost and
low-toxicity solvent with negligible vapor pressure, able to
solubilize both organic and inorganic compounds and has low
miscibility with organic solvents, attributes that position it as an
excellent solvent for catalysis.[29,30] Indeed, Gómez et al. have
pointed out the beneficial properties of glycerol in the
immobilization of Pd-, Cu- and Ni- nanoparticles stabilized by
In the last four decades, we have witnessed the development of
Nanoscience as well as the analytical techniques used for the
characterization of nanoparticles, to tailor the size and properties
of individual objects, for instance to become highly active and
selective catalysts.[1-4]
Several industrial processes rely on rhodium-based catalysis
given their versatility to perform a large variety of chemical
transformations including hydrogenations, hydroformylations and
carbonylations.[5-7] To promote catalyst activity under mild
conditions while extending the catalyst shelf-life as well as the
reuse of catalytic phase, rhodium nanoparticles (RhNPs) and in
particular supported RhNPs, have recently gained attention.
Besides solid supports, where RhNPs have been immobilized on
silica,[8-10] activated carbon,[11-13] alumina[14] and polystyrene;[15]
liquid phase immobilization provides the advantages of both
homogeneous and heterogeneous catalysis.[16,17] Compared to
common organic solvents, structured liquids organized through
electrostatic interactions, hydrogen bonding or - stalking, can
phosphines, alkaloid-based quinolines or polyvinylpyrrolidone
[31-36]
(PVP),
which have been applied for hydrogenation and
cross-coupling reactions as well as tandem processes.[37,38]
Some works have addressed the synthesis of group 9 metal
nanoparticles using glycerol as reducing agent, showing high
control on size and shape and protective effect of glycerol
toward oxidation.[39-42] Nevertheless, only one publication deals
with the synthesis of RhNPs in glycerol, without showing any
catalytic application.[42] Rh compounds in glycerol however, have
shown interesting catalytic applications in multistep reactions
help
to
stabilize
metal
nanoparticles
avoiding
such
as
Pauson-Khand
and
hydroaminomethylation
agglomeration.[18,19] In this context, ionic liquids (ILs) have been
widely explored for the immobilization of metal nanoparticles
from different transition metals, including Ir, Rh, Co, Pd, Ni and
Cu, among others.[20]
reactions.[43,44]
Considering our previous work using RhNPs in ionic liquid and
the lack of applications of these systems in suitable glycerol
solvent, herein we focus on the synthesis of thiolate capped-
RhNPs in glycerol and its application as recyclable catalyst for
selective hydrogenations and multi-step tandem processes.
Metal nanoparticles have been applied as catalysts in one-pot
methodologies for the formation of amines. Especially anilines,
which are important precursors for the synthesis of
pharmaceuticals, agrochemicals, dyes and additives in the
petroleum industry.[21] Selectivity is the main challenge in these
1
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10.1002/ejic.202000451
European Journal of Inorganic Chemistry
FULL PAPER
Results and Discussion
a
c
b
3.88 nm
Synthesis and characterization of RhNPs in glycerol
3.99 nm
Rhodium nanoparticles in glycerol were prepared by the
decomposition
of
the
organometallic
precursor
3.79 nm
3.67 nm
4.02 nm
3.41 nm
[Rh(−MeO)(COD)]2 under dihydrogen pressure. This method
was first applied by Chaudret and consists on the reduction of
organic ligands generating naked metal atoms that
spontaneously nucleate and growth to form nanoparticles with
narrow size distribution.[45] Contrary to ionic liquids where MNPs
can be stabilized by solvent, addition of ligands or stabilizers are
required in glycerol.[31] Based on our previous work using
pyridine as stabilizer for RhNPs in ionic liquids and the reports of
Pd and NiNPs in glycerol stabilized by nitrogen-containing
ligands, we tried the synthesis of RhNPs in glycerol stabilized by
triethanolamine, aminoglycerol or nicotinic acid.[27,33,35] However
only rhodium agglomerates were obtained in each case. Hence,
we synthesize RhNPs stabilized by glycerol-soluble thiolate, 1-
thioglycerol, obtaining a black colloidal mixture (Scheme 1). In
the presence of the ligand, the solubility of the rhodium
precursor was highly improved probably due to the formation of
Rh-thiolate complexes that can be reduced under dihydrogen
pressure to form nanoparticles, as previously observed.[28]
Varying the ligand to metal ratio did not show significant
differences in terms of size, shape or catalytic activity,
nonetheless a L/Rh ratio of 1 (RhNPs1) afforded a more robust
catalyst as shown below (Supporting Information, Figures S4-S7
for characterization of RhNPs0.5 L/Rh = 0.5).
3.36 nm
3.42 nm
d
2.2 Å
Figure 1. TEM micrographs showing nanoparticles assemblies (a). Magnified
TEM together with FFT analysis showing spherical RhNPs (b). HR-TEM of one
nanoparticle (c) and interplanar distance corresponding to Rh {111} (d).
Energy dispersive X-ray spectroscopy showed that the
nanoparticles contained Rh, S and O, confirming the presence
of the ligand at the surface of RhNPs (supporting information,
Figure S1). Surface state composition and electronic state of
RhNPs was studied by X-ray photoelectron spectroscopy. XPS
survey spectrum confirmed the presence of sulfur and rhodium
(Supporting information, Figure S2). High-resolution spectrum in
the binding energy region corresponding to rhodium (Rh 3d3/2
and Rh 3d5/2) showed a mixture of Rh(0) and Rh(I) in a 40/60
ratio (Figure 2). The high amount of Rh(I) can be explained by
the formation of Rh-thiolate species.
A
high 1-
Scheme 1. Synthesis of RhNPs in glycerol
thioglycerol/rhodium ratio prevented the formation of Rh(III)
species as observed in RhNPs0.5 (L/Rh = 0.5) (Supporting
Information, Figure S7).
RhNPs were characterized in the solid state after centrifugation,
removal of glycerol, redispersion in ethanol solution and drying.
Even though the negligible vapor pressure of glycerol allows
direct characterization from colloidal solution, it requires from
special technical handling, so we were urged to characterize the
materials in the solid state as described.
The TEM images showed assemblies comprised by well-
dispersed small dendritic RhNPs of an average size of 26.96 nm
and (HR)-TEM revealed that the RhNPs aggregates were
constituted of spherical nanoparticles with size ranging from
3.41 to 4.02 nm (Figure 1a and 1b). This kind of assemblies
constituted of nanoparticles were previously observed by Yang
in noble metal nanoparticles synthesized in oleylamine as
reducing media and by Gómez in the synthesis of PdNPs
capped with PVP at relatively low temperatures.[36] HR-TEM
together with fast Fourier transform evidenced the face centered
cubic (fcc) crystalline structure of Rh, where the measured
interplanar distance (2.2 Å) corresponded to the crystallographic
{111} planes (Figure 1c and 1d).
Figure 2. High-resolution XPS analysis in the binding region corresponding to
rhodium. Rh 3d5/2: Rh(0) = 39.6%; Rh(I) = 60.3%
Catalytic results
We chose the hydrogenation of nitrobenzene as benchmark
reaction for testing the catalytic activity of RhNPs1 in glycerol.
2
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10.1002/ejic.202000451
European Journal of Inorganic Chemistry
FULL PAPER
RhNPs1 in neat glycerol gave only 54% conversion but complete
selectivity to aniline (entry 1, Table 1). Adding glycerol to the
reaction mixture resulted in an increase of the conversion up to
76% after 3 h, showing that higher diffusion of both catalyst and
substrate improve catalytic activity (entry 2, Table 1). Likewise,
adding water to the black colloidal solution resulted in 88%
conversion (entry 3, Table 1). Using n-heptane instead of water
gave a similar conversion. In the latter, a biphasic system is thus
formed, allowing separation of the organic products after the
reaction is completed (entry 4, Table 1). Two phenomena could
play important roles in enhancing the catalytic activity of RhNPs
in biphasic media. The miscibility of reactants and products
could be facilitated by organic solvent, but also the additional
solvent could dilute the dendritic metal nanoparticles resulting in
more active systems. Finally, without hydrogen pressure no
reaction took place, revealing that transfer hydrogenation in
glycerol does not occur (entry 5, Table 1). No products other
than the ones expected were observed by GC nor NMR in any
of the catalytic reactions performed, however formation of side-
products derived from glycerol decomposition cannot be
discarded.
study and therefore the results attained with RhNPs0.5 won’t be
discussed (for further catalytic studies on RhNPs0.5 see
Supporting Information, Tables S1-S4).
Scheme 2. Rh-catalyzed reductive amination of aniline (1’) and benzaldehyde
(a).
Following this line-up, we prepared secondary amines via the N-
reductive alkylation of nitroaryls and aryl carboxaldehydes. The
multi-step reaction proceeds through the reduction of the nitro
group, followed by a condensation reaction of the resulting
aniline with aldehydes to form an imine derivative that can be
reduced under hydrogen pressure. The initial and final reduction
steps are catalyzed by RhNPs.
The N-reductive alkylation reactions were completed after 18 h
(Table 2). While nitrobenzene (1) and nitroacetophenone (2)
were completely reduced under the reaction conditions, we
observed different imine/amine ratio on the N-reductive
alkylation reaction from other substrates (entries 1 and 2, Table
2). An electron-withdrawing group on 2 make the reduction of
imine slower, and we observed a similar behavior for p-
chlorobenzaldehyde (b) (entry 3 in Table 2). On the other hand,
an electron-donating group in aldehydes seems to favor the
imine reduction, while 2-formylpyridine (d) gave excellent yields
probably due to straightforward coordination of the pyridine
moiety to RhNPs’ surface (entries 4 and 5, Table 2).
Table 1. Nitrobenzene (1) reduction to aniline (1’) with RhNPs in glycerol[a]
Entry
P (bar)
Added
solvent
%Conv.
(%Sel.)[b]
1
2
3
4
5
40
40
40
40
-
-
54 (>99)
76 (>99)
88 (>99)
89 (>99)
0
Table 2. Rh-catalyzed synthesis of secondary amines via N-reductive
alkylation reaction[a]
Glycerol
H2O
Entry
Nitroderivative
Aldehyde
Product
%Conv.
(%Sel.)[b]
Heptane
Heptane
1
94 (98)
1
a
a
1a
[a] Reaction conditions: 1 mmol of nitrobenzene, 1 mL of RhNPs1 in glycerol
([Rh] = 1 mol%), 2 mL of added solvent. [b] Conversion and selectivity
determined by GC using decane as internal standard.
99 (67)[c]
2
3
The optimized reaction conditions were applied in the reductive
amination to generate secondary amines. The synthesis of
amines through this multi-step process is a straightforward
methodology consisting on a condensation step of an aldehyde
with an amine, followed by reduction of the resulting imine,
enamine or hemiaminal (depending on the nature of the amine
used). Several groups have reported this synthetic method,
2
1
2a
1b
99 (77)[c]
b
mainly using Pd[32,46,47] catalysts but also Rh[27,28] or Cu[48]
.
Reductive amination of benzaldehyde (a) and aniline (1’)
catalyzed by RhNPs1 afforded the secondary amine with high
selectivity and activity in 18 h (Scheme 2). When RhNPs0.5 was
used as catalyst, we observed similar activities but lower
selectivity to amines (Scheme 2). At the end of the reaction with
RhNPs0.5, we observed bulk rhodium. The differing catalytic
behavior can be attributed to a lower concentration of 1-
thioglycerol stabilizer for RhNPs0.5, resulting in less stable NPs.
Similar results were obtained using benzylamine instead of 1’
with benzaldehyde (a) (Supporting Information, Figure S8). A
comparable behavior was observed throughout the catalytic
4
5
1
1
99 (99)
c
1c
1d
99 (99)
d
[a] Reaction conditions:
1
mmol of nitrobenzene derivative,
1
mmol of
aldehyde, 1 mL of RhNPs1 in glycerol ([Rh]=1 mol%). 2 mL of heptane, 40 bar
H2, 120 ºC, 18 h. [b] Conversion and selectivity determined by GC using
decane as internal standard. [c] Imine derivative observed.
3
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10.1002/ejic.202000451
European Journal of Inorganic Chemistry
FULL PAPER
Tertiary amines could be prepared from the reductive amination
of aldehydes and secondary amines under hydrogen pressure
without isolating any intermediate using RhNPs as catalyst
(Table 3). The scope of aldehydes and amines provided the
desired products with a remarkable selectivity towards the amine
in only 3 h. Higher yields were attained with alkylamines (entries
2 and 3, Table 3) in contrast to N-methylaniline (3) (entry 1,
Table 3). We were delighted to observe that morpholine (6)
afforded the condensation/reduction product with high selectivity
despite the competition with the formation of aminal and benzyl
alcohol previously observed (entry 4, Table 3) (Supporting
Information, Figure S9).[49,50]
Aldehydes bearing electron withdrawing (b) and electron
donating groups (c), as well as heterocyclic aldehydes (d) gave
the corresponding tertiary amines in high yields, pointing out the
catalytic system versatility (entries 5-7, Table 3). Unfortunately,
starting from nonanal (e), an n-alkyl aldehyde, we observed a
high amount of aldol condensation byproduct which is promoted
by the reaction conditions (entry 8, Table 3). Acetophenone (f)
needed longer times to achieve poor conversion, nevertheless
the catalytic system remained very selective (entry 9, Table 3.).
In the absence of hydrogen, no reaction took place, discarding
the hypothesis of transfer hydrogenation triggered by glycerol
(entry 10, Table 3).
[a] Reaction conditions: 1 mmol of substrate, 1 mL of RhNPs1 in glycerol
([Rh]=1 mol%). 2 mL of heptane, 40 bar H2, 120 ºC, 3 h. [b] Conversion and
selectivity to tertiary amine determined by GC using decane as internal
standard, benzyl alcohol observed as byproduct. [c] Aldol condensation as
byproduct. [d] 18 h. [e] Absence of H2.
To evaluate the reusability of the catalytic glycerol solution, we
chose the reductive amination of benzaldehyde (a) with
morpholine (6) as benchmark reaction. We were very pleased to
see that after 5 runs, there is no significant loss of activity nor
selectivity as the desired product was afforded in excellent yields
(Figure 3). TEM micrographs of the catalyst after reaction did not
exhibit any sign of agglomeration or decomposition (Supporting
Information, Figure S3). In addition, rhodium was not detected
by ICP-MS analyses of the organic phase after each cycle,
proving that there is no metal leaching.
Table 3. Synthesis of tertiary amines via RhNPs1-catalyzed N-monoalkylation
of aldehydes [a]
Entry
Amine
Aldehyde
Tertiary Amine
%Conv.
(%Sel.)[b]
1
a
62 (99)
91 (94)
Figure 3. Diagram showing the recycling of the catalytic phase RhNPs1 for the
reductive amination of benzaldehyde with morpholine. Figures indicate
conversion and selectivity determined by GC using decane as internal
standard.
3
3a
2
a
4
5
4a
5a
6a
3
4
a
a
84 (97)
90 (97)
Conclusion
In summary, we prepared for the first time thiolate-capped
RhNPs in glycerol. No important effect on the size or dispersion
were observed using different thioglycerol/rhodium ratios. The
as-prepared materials were fully characterized showing dendritic
assemblies constituted of small, spherical and well-dispersed fcc
Rh-nanoparticles. XPS analyses at the surface of the
nanoparticles showed the presence of a Rh(0)/Rh(I) mixture due
to the covalent bonding of thioglycerol ligand. Stabilized RhNPs
in glycerol were successfully used in biphasic catalysis with
heptane, where the organic products were easily separated at
the end of the reaction. Rh-catalyzed hydrogenation reactions of
different functional groups and tandem processes for the
synthesis of secondary and tertiary amines afforded the desired
products in excellent yields and selectivity. Glycerol played a key
role in the immobilization of the catalyst illustrated by the
reusability test, which showed that RhNPs1 had a remarkable
robustness through recycling. This novel catalyst constituted of
well-defined RhNPs stabilized by thiolate ligands in glycerol,
offers a complementary synthetic tool in selective hydrogenation
6
6
5
95 (92)
b
c
6b
6
7
8
6
6
6
97 (99)
98 (97)
6c
6d
6e
d
e
>99 (50)[c]
9[d]
6
6
34 (99)
0
5f
f
10[e]
a
6a
4
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10.1002/ejic.202000451
European Journal of Inorganic Chemistry
FULL PAPER
reactions compared to classical Rh behavior towards aromatic
ring reduction.
After reaction time, depressurization and removal of heptane, substrates
and heptane were added to the reaction mixture and the procedure for
catalytic reaction was repeated.
Experimental Section
Acknowledgements
General
This work was financially supported by the project from Consejo
Nacional de Ciencia y Tecnología (México) through grant CB-
2016-01-283094. A.S.-M. thanks CONACyT for a PhD grant.
A.R. thanks Programa de Becas Posdoctorales en la UNAM.
Authors are grateful for XPS analyses by the Laboratorio
Nacional de Almacenamiento y Conversion de Energía (LNCAE).
Authors thank Dr. Salas-Martin for technical support.
Unless otherwise stated, all chemical reagents were obtained from
commercial suppliers and used without further purification. Precursor
[Rh(-OMe)(COD)]2 was prepared following previously reported
methods.[51] All manipulations were performed using standard Schlenk
techniques under nitrogen atmosphere. Glycerol was dried under
vacuum at 80 °C for 18 h prior to use. NMR spectra were recorded on a
Varian VNMRS spectrometer (400 MHz for 1H NMR) and chemical shifts
were calibrated relative to residual solvent peak. GC analyses were
carried out on a Varian 3800 GC with ionization flame detector, using a
DB-WAX capillary column (30 m × 0.32 mm × 0.25 mm) composed by
polyethyleneglycol as stationary phase. Transmission electron
microscopy images of synthesized RhNPs were obtained on a JEOL
ARM200F microscope, and images of nanoparticles after recycling were
obtained on a JEOL JEM-210 microscope. Nanoparticles measurements
were performed with the software package DigitalMicrograph
3.30.2017.0.52 Synthesis of nanoparticles and catalytic reactions were
performed on a Parr Multi Reactor 500 system. ICP-MS experiments
were performed on a Bruker Aurora M90 equipment. XPS measurements
were performed using a Thermo Scientific K-Alpha spectrometer, with
MAGCIS ion source for depth profiling analysis and surface cleaning.
The assignment of chemical components of core level Rh 3d was made
by comparison to the referenced values reported in the literature.[28,53,54]
Keywords: biphasic catalysis • glycerol • nanoparticles •
reductive amination • rhodium
[1]
[2]
R. Schlögl, S. B. A. Hamid, Angew. Chem. Int. Ed., 2004, 43, 1628-
1637.
B. Voitglander, B. Meyer, N. M. Amer, Phys. Rev. B., 1991, 44,
10354-10357.
[3]
[4]
A. T. Bell, Science, 2003, 299, 1688-1691.
Nanocatalysis, (Eds: U. Heiz, U. Landman), Springer-Verlag, Berlin,
2007
.
[5]
[6]
P. Etayo, A. Vidal-Ferran, Chem. Soc. Rev., 2013, 42, 728-754.
S. K. Murphy, J.-W. Park, F. A. Cruz, V. M. Dong, Science, 2015
347, 56-60.
[7]
[8]
[9]
Rhodium Catalysed hydroformylation, (Eds: P. W. N. M. Van
Leeuwen, C. Claver), Kluwer Academic Publishers, New York, 2002
.
C. Chen, X.-Q. Dong, X. Zhang, Org. Chem. Front., 2016, 3, 1359-
1370.
M. J. Ndolomingo, B. Ndzondelelo, R. Meijboom, J. Mater. Sci.,
2020, 55, 6195-6241.
General synthesis of RhNPs in glycerol
To a 25 mL reactor flask equipped with a stirring magnet were added
[Rh(-OMe)(COD)]2 (0.05 mmol, 0.1 mmol of total Rh, 24.2 mg), 1-
thioglycerol (0.05 mmol for RhNPs0.5 or 0.1 mmol for RhNPs1) and
glycerol (10 mL). The reaction mixture was stirred 15 min at 80 ºC prior to
pressurize the system with hydrogen (10 bar) and stir at 80 ºC for 18 h.
After completion, reaction mixture was cooled down to room temperature
and hydrogen pressure was removed. The resulting black colloidal
solution was transferred to a Schlenk and stirred under vacuo at 80 ºC for
6 h in order to remove volatiles. Catalytic solution was stored under
nitrogen pressure.
[10] S. Ganji, S. S. Enumula, R. K. Marella, K. S. R. Rao, D. R. Burri,
Catal. Sci. Technol., 2014, , 1813-1819.
4
[11] E. Vunain, P. Ncube, K. Jalama, R. Meijboom, J. Porous Mater.,
2018, 25, 303-320.
[12] I. Choi, S. Chun, Y. K. Chung, J. Org. Chem., 2017, 82, 12771-
12777.
[13] L. Huang, Z. Wang, L. Geng, R. Chen, W. Xing, Y. Wang, J. Huang,
RSC Adv., 2015, 5, 56936-56941.
[14] M. Muñoz, Z. M. de Pedro, J. A. Casas, J. J. Rodríguez, Appl, Catal.
A: Gen., 2014, 488, 78-85.
[15] S. Sharma, D. Bhattacherjee, P. Das, Adv. Synth, Catal., 2018, 360,
2131-2137.
[16] L. S. Ott, R. G. Finke, Coord. Chem. Rev., 2002, 102, 3757-3778.
[17] J. Durand, E. Teuma, M. Gómez, Eur. J. Inorg. Chem., 2008, 3577-
3586.
Isolation of RhNPs to the solid state
RhNPs colloidal solution was centrifuged and washed 10 times with
ethanol to remove remaining glycerol. The resulting black powder was
redispersed in ethanol to prepare TEM grid.
[18] S. Wegner, C. Janiak, Top. Curr. Chem., 2017, 375, 65.
[19] I. Favier, D. Pla, M. Gómez, Chem. Rev., 2019, 120, 1146-1183.
[20] J. Dupont, J. D. Scholtten, Chem. Soc. Rev., 2010, 39, 1780-1804.
[21] S. Bähn, S. Imm, L. Neubert, M. Zhang, H. Neumann, M. Beller,
ChemCatChem, 2013, 3, 1853-1864.
General procedure for catalytic reactions under hydrogenation with
RhNPs
[22] C. S. Couto, L. M. Madeira, C. P. Nunes, P. Araujo, Chem. Eng.
Technol., 2015, 38, 1625-1636.
To a 25 mL reactor flask equipped with a stirring magnet were added
RhNPs in glycerol (0.01 M, 1 mL, 0.01 mmol Rh) at 80 ºC, heptane (2
mL) and substrates (1 mmol). Reaction mixture was then pressurized
with hydrogen (40 bar) and stirred at 120 ºC for 3 h. Then reactor was
cooled down with an ice bath, hydrogen pressure released, and heptane
was removed from the glycerol colloidal solution prior to be analyzed by
GC.
[23] E. A. Gelder, S. D. Jackson, C. M. Lok, Chem. Commun., 2005
,
522-524.
[24] Y. Zeng, Y. Wang, Y. Xu, Y. Song, J. Zhao, Z. Jin, Chin. J. Catal.,
2012, 33, 402-406.
[25] B. Tan, J. Jiang, Y. Wang, L. Wei, D. Chen, Z. Jin, Appl.
Organomet. Chem., 2008, 22, 620-623.
[26] Y. Xu, Y. Wang, K. Li, M. Niu, Y. Zeng, J. Jiang, Z. Jin, J. Nanosci.
Nanotechnol., 2013, 13, 5048-5052.
General procedure for recycling of RhNPs
[27] A. Serrano-Maldonado, E. Martin, I. Guerrero-Ríos, Eur. J. Inorg.
Chem., 2019, 2863-2870.
5
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10.1002/ejic.202000451
European Journal of Inorganic Chemistry
FULL PAPER
[28] A. Serrano-Maldonado, S. S. Rozenel, J. L. Jimenez-Santiago, I.
Guerrero-Ríos, E. Martin, Catal. Sci. Technol., 2018, 8, 4373-4382.
[29] A. E. Díaz- Álvarez, J. Francos, B. Lastra-Barreira, P. Crochet, V.
Cadierno, Chem. Commun., 2011, 47, 6208-6227.
[30] F. Chahdoura, I. Favier, M. Gómez, Chem. Eur. J., 2014, 20, 10884-
10893.
[31] F. Chahdoura, C. Pradel, M. Gómez, Adv. Synth. Catal., 2013, 355,
3648-3660.
[32] F. Chahdoura, I. Favier, C. Pradel, S. Mallet-Ladiera, M. Gómez,
Catal. Commun., 2015, 63, 47-51.
[33] A. Reina, C. Pradel, E. Martin, E. Teuma, M. Gómez, RSC Adv.,
2016, 6, 93205-93216.
[34] T. Dang-Bao, C. Pradel, I. Favier, M. Gómez, Adv. Synth. Catal.,
2017, 359, 2832-2846.
[35] A. Reina, I. Favier, C. Pradel, M. Gómez, Adv. Synth. Catal., 2018
,
360, 3544-3552.
[36] a) Y. Feng, X. Ma, L. Han, Z. Peng, J. Yang, Nanoscale, 2014, 6,
6173-6179; b) A. Reina, I. Favier, E. Teuma, M. Gómez, A. Conte,
L. Pichon, AIChE J., 2019, 65, e16752.
[37] F. Chahdoura, S. Mallet-Ladeira, M. Gómez, Org. Chem. Front.,
2015, 2, 312-318.
[38] A. Reina, A. Serrano-Maldonado, E. Teuma, E. Martin, M. Gómez,
Catal. Commun., 2018, 104, 22-27.
[39] S. Gudyka, G. Grzybek, J. Grybos, P. Indyka, B. Leszczynski, A.
Kotarba, Z. Sojka, Appl. Catal. B Environ., 2017, 339-347.
[40] P. P. Pedra, J. L. Silva Filho, R. J. S. Lima, S. K. Sharma, K. O.
Moura, J. G. S. Duque, C. T. Meneses, J. Nanosci. Nanotechnol.,
2016, 16, 4943-4947.
[41] P. Nekoi, M. Akbari, M. K. Amini, Int. J. Hydrogen Energ., 2010, 35,
6392-6398.
[42] M. Harada, C. Cong, Ind. Eng. Chem. Res., 2016, 55, 5634-5643.
[43] F. Chahdoura, L. Dubrelle, K. Fourmy, J. Durand, D. Madec, M.
Gómez, Eur. J. Inorg. Chem., 2013, 5138-5144.
[44] A. Serrano-Maldonado, T. Dang-Bao, I. Favier, I. Guerrero-Ríos, D.
Pla, M. Gómez, Chem. Eur. J., DOI: 10.1002/chem.202001978.
[45] K. Philippot, B. Chaudret, C. R. Chim., 2003, 6, 1019-1034.
[46] R. J. Kalbasi, O. Mazaheri, New J. Chem., 2016, 40, 9627-9637.
[47] P. Rubio-Marqués, A. Leyva-Pérez, A. Corma, Chem. Commun.,
2013, 49, 8160-8162.
[48] A. L. Nuzhdin, E. A. Artiukha, G. A. Bukhtiyarova, E. A.
Derevyannikova, V. I. Bukhtiyarov, Catal. Commun., 2017, 102,
108-113.
[49] N. Sakai, H. Hori, Y. Yoshida, T. Konakahara, Y. Ogiwara,
Tetrahedron, 2015, 71, 4722-4729.
[50] V. I. Tararov, R. Kadyrov, T. H. Reirmeier, A. Boerner, Adv. Synth.
Catal., 2002, 344, 200-208.
[51] J. A. C. R. Uson, L. A. Oro, Inorg. Synth., 1985, 23, 126-130.
[52] DigitalMicrograph 3.30.2017.0, Gatan Inc., 1996-2018.
[53] C. Jin, W. Jia, T. C. Nagaiah, J. Guo, X. Chen, N. Li, M. Bron, W.
Schuhmann, M. Muhler, J. Mater. Chem., 2010, 20, 736-742.
[54] Y. Li, N. Li, K. Yanagisawa, X. Ding, X. Li, J. Mater. Chem. A, 2014
,
2, 1484-1494.
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This article is protected by copyright. All rights reserved.

10.1002/ejic.202000451
European Journal of Inorganic Chemistry
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Thiolate-capped RhNPs in glycerol catalyzed the formation of alkyl and arylamines through reductive amination. The catalytic
reaction took place as a biphasic process glycerol/heptane, facilitating the separation of organic products from the glycerol phase.
RhNPs in glycerol could be re-used several times for the reductive amination without loss of activity nor selectivity.
Institute and/or researcher Twitter usernames: @quimica_unam
Key Topic: RhNPs-glycerol
7
This article is protected by copyright. All rights reserved.