Dendrimer-Encapsulated Pd Nanoparticles, Immobilized in Silica Pores, as Catalysts for Selective Hydrogenation of Unsaturated Compounds

Article abstract of DOI:10.1002/open.201800280

Heterogeneous Pd-containing nanocatalysts, based on poly (propylene imine) dendrimers immobilized in silica pores and networks, obtained by co-hydrolysis in situ, have been synthesized and examined in the hydrogenation of various unsaturated compounds. The catalyst activity and selectivity were found to strongly depend on the carrier structure as well as on the substrate electron and geometric features. Thus, mesoporous catalyst, synthesized in presence of both polymeric template and tetraethoxysilane, revealed the maximum activity in the hydrogenation of various styrenes, including bulky and rigid stilbene and its isomers, reaching TOF values of about 230000 h^?1. Other mesoporous catalyst, synthesized in the presence of polymeric template, but without addition of Si(OEt)₄, provided the trans-cyclooctene formation with the selectivity of 90–95 %, appearing as similar to homogeneous dendrimer-based catalysts. Microporous catalyst, obtained only on the presence of Si(OEt)₄, while dendrimer molecules acting as both anchored ligands and template, demonstrated the maximum activity in the hydrogenation of terminal linear alkynes and conjugated dienes, reaching TOF values up to 400000 h^?1. Herein the total selectivity on alkene in the case of terminal alkynes and conjugated dienes reached 95–99 % even at hydrogen pressure of 30 atm. The catalysts synthesized can be easily isolated from reaction products and recycled without significant loss of activity.

Full text of DOI:10.1002/open.201800280

DOI: 10.1002/open.201800280
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Dendrimer-Encapsulated Pd Nanoparticles, Immobilized in
Silica Pores, as Catalysts for Selective Hydrogenation of
Unsaturated Compounds
Edward A. Karakanov,[a] Anna V. Zolotukhina,[a, b] Andrey O. Ivanov,[b] and
Anton L. Maximov*[a, b]
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Heterogeneous Pd-containing nanocatalysts, based on poly (OEt)4, provided the trans-cyclooctene formation with the
(propylene imine) dendrimers immobilized in silica pores and selectivity of 90–95%, appearing as similar to homogeneous
networks, obtained by co-hydrolysis in situ, have been synthe- dendrimer-based catalysts. Microporous catalyst, obtained only
sized and examined in the hydrogenation of various unsatu- on the presence of Si(OEt)4, while dendrimer molecules acting
rated compounds. The catalyst activity and selectivity were as both anchored ligands and template, demonstrated the
found to strongly depend on the carrier structure as well as on maximum activity in the hydrogenation of terminal linear
the substrate electron and geometric features. Thus, mesopo- alkynes and conjugated dienes, reaching TOF values up to
rous catalyst, synthesized in presence of both polymeric 400000 hÀ 1. Herein the total selectivity on alkene in the case of
template and tetraethoxysilane, revealed the maximum activity terminal alkynes and conjugated dienes reached 95–99% even
in the hydrogenation of various styrenes, including bulky and at hydrogen pressure of 30 atm. The catalysts synthesized can
rigid stilbene and its isomers, reaching TOF values of about be easily isolated from reaction products and recycled without
230000 hÀ 1. Other mesoporous catalyst, synthesized in the significant loss of activity.
presence of polymeric template, but without addition of Si
Introduction
arenes,[14] cyclodextrines[15] and dendrimers[1a,16]), are used to
stabilize metal nanoparticles.
Systems based on metal nanoparticles are the most prospective
Due to their physical and chemical properties, dendrimers,
catalysts for hydrogenation, oxidation and cross-coupling which are the spherically symmetrical globular macromolecules
reactions.[1] They may be applied both as homogeneous and with branched regular structure,[17] appeared as the most
heterogeneous catalysts. In the last case metal nanoparticles interesting for their application in catalysis. The primary merits
are supported on the various inorganic carriers, such as of dendrimers are: 1) sorption of strictly defined metal
mesoporous silica and zeolites,[2] Al2O3,[3] carbon doped silica[4] quantity;[17c] 2) control of solubility and substrate selectivity due
and carbon materials (activated carbon,[5] carbon nanofibers to the dendrimer end group modification;[17a,18] 3) recyclability
and nanotubes,[6] polyaromatic frameworks[7]) to prevent par- due to the fractional precipitation of dendritic species from the
ticles agglomeration and subsequent catalyst deactivation. In solution.[19]
homogeneous catalysts various donor organic ligands, both
For the first time dendrimers were suggested as structure-
forming agents for metal nanoparticles-based catalytic systems
low-molecular (amines,[8] ionic liquids,[1a,8b–d, 9] phosphines[8b,d,10]
)
and supramolecular ligands (poly-(N-vinyl pyrrolidone),[1a,8b,d,11] instead of block co-polymers[20] to prevent exchange by macro-
poly(ethylene glycol),[1a,12] poly(ethylene imine),[11a,13] calix- molecules and metal ions between micelles. Thus especial
nanoreactors, in which metal nanoparticles were encapsulated
within the dendrimer molecule, were proposed (Figure 1).[21]
[a] Prof. Dr. E. A. Karakanov, Dr. A. V. Zolotukhina, Prof. Dr. A. L. Maximov
Department of Petroleum Chemistry and Organic Catalysis
Moscow State University
119991, Moscow (Russian Federation)
Fax: +7(495)9391951
E-mail: max@ips.ac.ru
[b] Dr. A. V. Zolotukhina, A. O. Ivanov, Prof. Dr. A. L. Maximov
A.V. Topchiev Institute of Petrochemical synthesis RAS
119991, Moscow (Russian Federation)
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/open.201800280
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
This is an open access article under the terms of the Creative Commons
Attribution Non-Commercial NoDerivs License, which permits use and dis-
tribution in any medium, provided the original work is properly cited, the
use is non-commercial and no modifications or adaptations are made.
Figure 1. Dendrimer-stabilized (left) and dendrimer-encapsulated nanopar-
ticles (right).[21]
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Scheme 1. Approach to the synthesis of metal nanoparticles, encapsulated into the matrices of cross-linked PPI or PAMAM dendrimers.[30]
This approach can be realized only under the following
conditions:[22] 1) dendrimer peripheral groups must not be able
to complex formation to prevent nanoparticle stabilization; 2)
dendrimer end groups must be charged to provide repulsion
between dendrimer molecules; 3) dendrimer generation must
be high enough to enclose nanoparticle. In this connection the
much more widespread is the dendrimer stabilization (Figure 1),
that does not require especial synthesis conditions[23] and
includes simple complex formation of dendrimers with the ions
of metal sorbed, followed by reduction with sodium
borohydride.[17b]
Using this approach, metal nanoparticles of various size and
nature, stabilized by carbosilane,[24] poly(aryl ether),[19a,f–g] poly
(amido amine) (PAMAM) or poly(propylene imine) (PPI) den-
drimers with amino,[25] hydroxyl,[26] thiol[27] or carboxyl end
groups[28] can be obtained. Dendrimer molecules here act as
surfactants,[29] adsorbed on the surface of growing nano-
particles, resulting in the larger size of the latters and wider
particle size distribution in comparison with dendrimer-encap-
sulated nanoparticles.[21–22]
drimers by various bifunctional agents (diepoxides, diisocya-
nates), followed by metal ions impregnation and subsequent
reduction (Scheme 1).[30] The driving force for the metal sorption
here was the complex formation. Metal ions and nanoparticles
were retained in the carrier due to large amount of donor
coordination groups in the network and also by the multiple
sterical hindrances, originated from the latter.
Ru- and Rh containing catalysts, synthesized by this way,
appeared as highly active catalysts for exhausting hydrogena-
tion of aromatic compounds and phenols under two-phase
conditions, maintaining their efficacy at recycling.[31] Analo-
gously Pd nanoparticles, encapsulated into cross-linked net-
works of PPI and PAMAM dendrimers, proved themselves as
highly active, selective and stable catalysts for semi-hydro-
genation of phenyl acetylene and conjugated dienes.[32] It was
demonstrated, that the nature and generation of dendrimer
used, the nature, size and rigidity of cross-linking agent, as well
as the synthesis conditions (temperature, solvent and the
presence of polymeric template) had an essential influence on
both physical chemical properties (particles size distribution,
metal weight content, metal surface valency states etc.), activity
and selectivity of the catalyst obtained.[31c,32a]
The main disadvantage of such systems is the gradual metal
leaching from stabilizing micelles, leading to catalyst
deactivation.[19f–g] In this connection the promising may appear
the heterogenisation of dendrimer-based catalysts, allowing to
combine the advantages of both conventional homogeneous
and heterogeneous catalysts, for that several approach were
developed.
Similar approach was also developed in the works.[33] Pd
nanoparticles here were synthesized in situ, encapsulated in
PAMAM dendrimers, co-polymerized with ethylene glycol
diacrylate.[33a] Herein nanoparticles growth occurred simultane-
ously with the meshy polymeric matrix formation, and the pore
size was limited by the dendrimer diameter. Thus synthesized
catalyst appeared as highly active in Suzuki-Miyaura cross-
The first one was the cross-linking of amino-terminated poly
(propylene imine) (PPI) and (poly)amidoamine (PAMAM) den-
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coupling in water, giving a yield exceeding 90% within 2 hours,
maintained during 8 cycles. Acid network-like material, based
on PPI dendrimers, cross-linked with Sc(OTf)3, successfully
catalyzed Mukaiyama aldol addition, Friedel-Crafts acylation
and Diels-Alder coupling.[33b]
The main drawback of such materials, namely synthesized
with the use of diisocyanates as cross-linking agents, is the
liability to metal-catalyzed hydrolysis under two-phase con-
ditions, resulting in partial network destruction and, as a
consequence, in particles agglomeration.[31a]
Analogously, using aminomethylation reaction, PPI den-
drimers can be anchored on the surface of ordered mesoporous
phenol-formaldehyde resins (OMR, MPF).[46] Impregnated with
Pd nanoparticles, such materials appeared as stable, very active
and selective catalysts in semi-hydrogenation of both terminal
and internal liner alkynes, giving TOF values up 120000 hÀ 1.[46]
An alternative approach was the co-hydrolysis of Si(OEt)4
with PPI dendrimers, modified with (3-glycidoxy)propyltri-
methoxysilane, in situ, resulting in regular porous material:
microporous in the absence of the additional polymeric
template (dendrimer appeared as both ligand for nanoparticles
stabilization and template for pore formation) and mesoporous
in the presence of polymeric PEG-based template (Schemes 2
and 3).[46] Impregnated with Ru nanoparticles, these catalysts
were applied for the effective hydrogenation of phenols to
corresponding cyclohexanols[47] and for selective hydrogenation
of levulinic acid and its esters to γ-valerolactone.[48]
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The alternative approach for heterogenization of den-
drimer-based catalysts is the grafting of dendrimers or
dendrons on the surface of organic or inorganic insoluble
carriers, such as SiO2 (both amorphous and mesoporous),[34]
cross-linked
poly(styrene),[35]
poly(thiophenes),[36]
poly
(vinylpyridines)[37] etc., by means of covalent or electrostatic
interactions. Thus synthesized materials, impregnated with Pd,
Ag, Au, Ru and Rh nanoparticles, proved their effectiveness in
the selective hydrogenation of olefins,[16,34a] conjugated
dienes,[16,34b] aromatic and heterocyclic compounds,[16,36b] cross-
coupling,[16,35c,38] aldol condensation,[35b] carbonylation[39] and
oxidation reactions.[40] Also immobilized dendrimers and den-
drons can be impregnated by metal nanoparticles, already
stabilized by simple organic ligands, e.g. ionic liquids.[41]
In the present work we propose the use of these hybrid
dendrimer-based organo-silica materials as carriers for effective
Pd nanocatalysts in the selective hydrogenation of unsaturated
compounds.
Results and Discussion
Multiwall carbon nanotubes (MWCNTs) were also proposed
as prospective carriers for anchoring dendrimer-based catalysts.
Herein, as in the case of polystyrene or silica,[34–35] grafting the
dendrons was performed by surface modification with amino
groups followed by repeated Michael addition and subsequent
end group activation.[42] For this Pd-PAMAM-g-MWCNTs cata-
lysts not typical positive dendritic effect was observed in
Mizoraki-Heck cross-coupling reaction: the reaction rate in-
creased with the increase of dendron generation, that
authors[42] explained in terms of the enhanced stability due to
sterical hindrances surrounding the catalytic centers.
These catalysts, based on the anchored dendrons, are stable
at recycling and, as a rule, resistant to metal leaching.[34–35,42]
Nonetheless, these materials are characterized by irregular
dendrimer coating due to mutual sterical hindrances, arisen
from bulky dendrons and resulting in irregular metal distribu-
tion through the carrier. To solve this problem, two different
approaches were suggested.
The first one was the immobilization of ready dendrimers
(not dendron grafting) on the silica polyamine composite via
Mannich reaction (Scheme S1).[43] Herein anchoring the den-
drimers was performed, considering the space, occupied by the
latters on surface of the carrier. Impregnated with Pd and PdAg
nanoparticles, this material was characterized by regular and
narrow particle size distribution and proved its high efficacy
and stability in selective hydrogenation of phenyl acetylene,
linear alkynes and conjugated dienes.[43–44] Similar approach was
earlier applied for ready poly(ether imine) phosphine modified
dendrimer, anchored to amorphous silica, preliminary function-
alized with 3-chloropropylsilane.[45] Impregnated with Pd nano-
particles, this material was successfully applied in the hydro-
genation of various alkenes.
The Synthesis of Bimetallic Dendrimer-Based Heterogeneous
Catalysts
In this work, in addition to earlier synthesized hybrid organo-
silica materials, denounced as G2-dendr-meso-SiO2 and G3-
dendr-SiO2, prepared by cohydrolysis tetra(ethoxy)silane with
PPI dendrimers, modified with (3-glycidoxy)propyl trimethoxysi-
lane in the presence or absence of Pluronic template
correspondingly (Schemes 2 and 3),[46] recently we have
developed a new organo-silica carrier with low Si/N ratio. The
latter have been achieved by exception of Si(OEt)4 from the
synthetic procedure. As a consequence, PPI dendrimers of 2nd
generation, partly modified with (3-glycidoxy)propyl trimethox-
ysilane, underwent co-hydrolysis with each other in the
presence of polymeric template Pluronic P123 (Scheme S4).
Physical chemical properties of thus obtained meso-G2-
dendr-Si carrier, as well as of earlier synthesized G2-dendr-
meso-SiO2 and G3-dendr-SiO2, are presented in Tables S1 and
S2. As seen from Figures S1–S3, in contrast to G2-dendr-meso-
SiO2 and G3-dendr-SiO2, meso-G2-dendr-Si does not have well-
marked pores and channels in its structure and looks like as a
typical dendrimer networks.[31a] One may suggest, that relatively
bulk and flexible (in comparison with Si(OEt)4) PPI dendrimers
are not able to form a rigid ensemble around the Pluronic
micelle, resulting in amorphous structure.
XPS and solid-state NMR spectroscopy of meso-G2-dendr-Si
sample (Table S1) confirmed the presence of fragments, typical
for PPI dendrimers (NCH2CH2CH2N, NCH2CH2CH2NH2, etc.)[49] and
modifying groups, that link dendimers each other
(SiCH2CH2CH2O, OCH2CH(OH)CH2NH).[49–50] Herein silicon was not
detected, that probably might be due to its very low content in
the sample. The another reason might be too deep location of
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Scheme 2. The synthesis of hybrid G2-dendr-meso-SiO2 material.[47]
Scheme 3. The synthesis of hybrid G3-dendr-SiO2 material.[47]
Si groups under the surface, not detectable by XPS method, in
contrast to dendrimer fragments, characterized by high surface
C and N atomic concentrations.
observed results may be explained by that dendrimers,
anchored to the inner surface of mesopores in G2-dendr-meso-
SiO2, possess by partial mobility and, as a consequence, are
subjected to much stronger vacillation in comparison to those
in meso-G2-dendr-Si, bounded into the network, or in G3-
dendr-SiO2, where dendrimer molecules, being simultaneously a
templates for pore formation, are anchored to their walls by all
modified end groups (Schemes 2–4).[35a,51]
13C NMR spectrum for meso-G2-dendr-Si is relatively well
resolved similar to G3-dendr-SiO2, while G2-dendr-meso-SiO2
carrier is consisted of poorly solved, broadened signals, related
to glycidyl (~66–80, 80–96 ppm), dendrimer (~21–66 ppm) and
oxypropylsilane (~12–21 ppm) fragments (Figure S4). Thus
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Scheme 4. The synthesis of hybrid meso-G2-dendr-Si material.
Scheme 5. Encapsulation of Pd nanoparticles into dendrimer-based organo-silica carriers on the example.
All three carriers: G2-dendr-meso-SiO2, G3-dendr-SiO2 and
meso-G2-dendr-Si – were used as supports for Pd catalysts. Pd
deposition was performed according to earlier published
procedures for dendrimer-based materials by wetness impreg-
nation method, using Pd(OAc)2 in chloroform as a metal source
and NaBH4 as a reducing agent (Scheme 5).[43]
The catalysts synthesized were characterized by means of
atomic emission spectroscopy with inductively coupled plasma
(ICP-AES), transmission electron microscopy (TEM), X-ray photo-
electron (XPS) and solid-state NMR spectroscopy. Physical
chemical properties of the catalysts obtained are listed in
Table 1 and illustrated in Figures 2 and 3 and S5–S13.
As one can see, both silica-containing catalysts are charac-
terized by Pd content, close to the theoretical one (Table 1). The
latter can be calculated as the mass ratio of Pd, loaded in the
synthesis, to the sum of Pd loaded and carrier mass and
reached ~8.7–9.3% for G3-dendr-SiO2-Pd and G2-dendr-meso-
SiO2-Pd. In meso-G2-dendr-Si-Pd the found Pd content, vice
versa, is inferior to theoretical (that is of 19.9%) by ~2.5 times.
Similar phenomenon was earlier observed for meso-G3-PPI-
DMDPDI-Pd catalyst, based on the PPI dendrimer network, also
synthesized in the presence of polymeric template.[32a]
As in the case of dendrimer-based hybrid organo-silica Ru-
containing catalysts,[46] the use of mesoporous carrier did not
result in the significant particle size increase (Table 1). Nonethe-
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Table 1. Physical chemical properties of the dendrimer-based Pd-containing catalysts.
Entry Catalyst Pd content, wt.% d, nm XPS atomic concentrations, %
1
2
3
4
5
6
7
8
9
Pd 3d5/2 valency states, % (eV)
Pd0
PdOx/Pd PdO
Pd Si
C
N
O
Pd2+
Pd(OAc)2, Pd (II)
N-bound
1
2
3
G3-dendr-SiO2-Pd
6.70
2.81�0.71 3.1 28.3 4.2
3.29�0.34 2.7 32.1 3.6
2.71�0.44 2.3 62.5 18.6 16.6
48.5 15.9 54.5
(335.8)
48.2 13.1 63.9
–
41.2
(337.4)
–
–
4.3
(338.7)
2.5
G2-dendr-meso-SiO2-Pd 7.58
18.2
16.3
(338.0) (339.0)
28.6
(337.8)
(335.2) (336.5)
26.4 45.0
(335.3) (336.6)
meso-G2-dendr-Si-Pd
7.71
–
–
–
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Figure 2. Pd 3d XPS spectra of the synthesized organo-silica dendrimer-based catalysts.
less, the particle size distribution and morphology were differ-
ent for each sample. G2-dendr-meso-SiO2-Pd was characterized
by particle size distribution with a maximum at 3.0 nm and
preferentially regular distribution of particles inside pores of the
carrier (Figures 3 and S5). The electron diffraction, obtained
from the larger nanoparticles by HRTEM method, also con-
firmed the presence of Pd crystallites in the sample (Table S3,
Figures S6–S7). Herein Pd nanoparticles apparently ordered and
limited vacillations of dendrimers, resulting in the better
resolution for corresponding 13C NMR spectrum (Figure S8).
For meso-G2-dendr-Si-Pd particle size distribution was close
to Gauss function with a maximum at 2.2 nm (Figures 3 and S9),
often typical for the catalysts, based on the dendrimer
networks.[32] However particle distribution through the carrier
surface was not regular, and sample contained areas both with
high and low particle density (Figure S9).
Particle size distribution in G3-dendr-SiO2-Pd is very similar
to pore size distribution of the corresponding carrier with a
maximum of ~0.85 nm, a minimum diameter for Pd nano-
particles (Figures 3, S10–S11).[2g,52] One may assume, that
particles with diameter range of 0.85–2.5 nm are located
predominantly in the micropores of the carrier, where the larger
size corresponds to modified PPI dendrimer of 3rd generation in
the expanded state. Larger crystallites (Figures S10, S12) are
located respectively in the outer pore space, on the carrier
surface, resulting in increase of the mean particle diameter. It
can also be noted, that inclusion of Pd particles in the carrier
structure had no a sufficient influence on the 13C NMR spectrum
of the latter (Figure S13).
According to the XPS data (Table 1, Figure 2), Pd in all three
samples was presented both in zero-valent (Pd0, 335.0–335.7 eV
[53]
at Pd 3d5/2
)
and oxidized forms (PdOx, 336.5 eV at Pd 3d5/2;
PdO, 337.4 eV at Pd 3d5/2),[54] that is typical for catalyst stored in
the air[55] and containing N- and O-coordination groups in their
structures.[53a–b,56] Nonetheless, the distribution of the latters was
significantly dependent on the carrier structure for the certain
catalyst. Thus, meso-G2-dendr-Si-Pd, in spite of the lowest
oxygen content (~17%), was characterized by the lowest Pd0
portion (~26.5%) and maximum portion of the oxidized species
in comparison with both G2-dendr-meso-SiO2-Pd and G3-dendr-
SiO2-Pd (Table 1, Figure 1). The ratio of surface Pd concen-
tration, Cs (2.3%), to the volume Pd content, Cv (7.7%), was also
the lowest for this catalyst an reached approximately 0.3. Herein
it should be noted, that an oxygen portion, relating to silica
knots, is extremely low in this sample; therefore Pd is appeared
to bound with oxygen both from glycidyl groups of the carrier
and adsorbed from the air.
G2-dendr-meso-SiO2-Pd, vice versa, was characterized by the
highest portion of Pd0 state, reaching ~64% of total surface Pd
content (Table 1). G3-dendr-SiO2-Pd had the highest Cs/Cv ratio
of ~0.5 and Pd/O ratio close to those for G2-dendr-meso-SiO2-
Pd, while Pd0 portion was ~55% (Table 1, Figure 1). The main
difference for this sample is a relatively high binding energy for
Pd0 state, as compared with G2-dendr-meso-SiO2-Pd and meso-
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Figure 3. TEM images and particle size distributions of the synthesized Pd-containing organo-silica dendrimer-based catalysts.
G2-dendr-Si-Pd (Table 1). This phenomenon can be explained in
terms of small particle sizes, predominating in the G3-dendr-
SiO2-Pd sample: the smaller particle size, the higher uncompen-
sated surface partly positive charge, and, as a consequence, the
higher binding energy for Pd0.[57]
Also G3-dendr-SiO2-Pd sample contained a low, but notice-
able portion of Pd2+ ions, strongly bounded with the dendrimer
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Table 2. Hydrogenation of styrenes in the presence of G2-dendr-meso-SiO2-Pd catalyst.[a]
1
2
3
Entry
Substrate
Catalyst loading, mg
Substrate/Pd
(mol/mol)
P (H2), atm.
Conv., %
TOF, hÀ 1
4
5
6
7
8
9
1
2
3
4
5
6
7
8
Styrene
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
1
0.5
1
0.5
0.5
0.5
0.5
1
36760
36760
91900
38360
38360
95905
18395
18395
2335
4665
2335
4665
4665
10
30
30
10
30
30
10
30
10
10
10
10
30
30
30
10
10
30
53
100
63
50
94
55
60
74
79
10.5
98.5
50.5
100
81
46
91
43
77
77930
147040
231590
76725
144240
210995
44155
54455
7385
1965
9205
9440
18695
30285
25795
8685
8205
14695
4-methylstyrene
4-tert-butylstyrene
4-phenylstyrene
trans-stilbene
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
9
10
11
12
13
14
15
16
17
18
9330
14000
2385
4770
1,1-diphenylethylene
0.5
0.5
4770
°
[a] Reaction conditions are: 80 C, 15 min.
fragments (Table 1). Analogous tendency was earlier observed
for Pd nanoparticles, encapsulated in PPI dendrimers of 3rd
generation, immobilized on the silica-polyamine composite
surface,[43] as well as for Pd nanoparticles, encapsulated in high
densely cross-linked networks of PPI and PAMAM
dendrimers.[32a]
fractions and t is the minimal reaction time, for which the
reaction progress is measured.
In hydrogenation of styrenes corresponding substituted
alkylbenzenes were the only reaction products for all catalysts.
It was established, that catalyst activity was simultaneously
dependent on the carrier structure, substrate size and geome-
try, electron factors. Mesoporous G2-dendr-meso-SiO2-Pd cata-
lyst appeared the highest activity for the most of substrates
(Table 2, Figure 4). For styrene it exceeded 75000 hÀ 1 at molar
substrate/Pd ratio of ~36760 and hydrogen pressure of 10 atm.
and 230000 hÀ 1 at molar substrate/Pd ratio of about 91900 and
hydrogen pressure of 30 atm., that was extremely superior to
Pd catalyst, based on PPI dendrimers, anchored on the silica
polyamine composite (Pd-G3-dendr@BP-1), earlier tested in the
analogous reaction.[43] So high efficacy for G2-dendr-meso-SiO2-
Pd can be attributed to its regular mesoporous structure,
providing the well access for substrate to the active Pd
nanoparticles, while the ratio of Pd0/(PdOx +Pd2+) was approx-
imately equal for both catalysts. Nonetheless, it should also be
noted, that in the present work we have used higher temper-
It appears, that hyper-branched PPI dendrimers of 3rd
generation or PAMAM dendrimers of 2nd generation are able
not only to stabilize metal nanoparticles through electron
donation,[1a,16,17b–c] but also to interfere the metal ions reduction
due to formation of stable chelate complexes.
Pd2+ ions, those may origin from the rest Pd(OAc)2 or
weakly bounded Pd complexes with dendrimers, are absent in
G3-dendr-SiO2-Pd, as compared with G2-dendr-meso-SiO2-Pd
and meso-G2-dendr-Si-Pd (Table 1). At the same time the
remarkable portion of PdO in this sample can be referred not
only to the oxidation in the air,[55] but also to the strong
interactions of Pd species with silica matrix,[53a] to those small
particles are subjected extremely.[57]
atures (80 C instead of 70 C[43]) and carried out the experiments
for liquid substrates in the absence of solvent, thus avoiding
the competitive adsorption of the latter and the dilution effect.
With the substrate size increased, catalytic activity for G2-
dendr-meso-SiO2-Pd decreased (Table 2, Figure 4), that was
typical for the dendrimer-based catalysts.[17c,18a] This downfall
was especially remarkable for substrates, such as trans-stilbene,
4-phenylstyrene and 1,1-diphenylethylene, whose substituents
(phenyl rings) possessed the weak –M-effect, along with bulk
and rigid substrate geometry, hindering the adsorption of the
latter. Even slightly increase of substrate/Pd ratio from ~2300–
2400 to ~4700–4800 resulted in notable decrease in conversion:
from 98 to 50% for trans-stilbene, from 79 to 10% for 4-
phenylstyrene and from 91 to 43% for 1,1-diphenylethylene
within 15 minutes at hydrogen pressure of 10 atm. (Table 2).
°
°
Hydrogenation of Unsaturated Compounds in the Presence
of Hybrid Dendrimer-Based Pd Catalysts
Synthesized catalysts were tested in the hydrogenation of
various unsaturated compounds, such as styrenes, alkynes and
dienes. Catalyst activity, defined as the reaction turnover
frequency (TOF), was calculated as amount of the substrate
reacted (νsubstr) per mole of metal (νPd) per unit of time,
according to formula:
nsubstr � w
TOF ¼
nPd � t
where ω is the substrate conversion, expressed in the unit
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°
Figure 4. Hydrogenation of styrenes in the presence of the dendrimer-based organo-silica palladium nanocatalysts. Reaction conditions are: 80 C, 15 min.
Table 3. Hydrogenation of styrenes in the presence of G3-dendr-SiO2-Pd catalyst.[a]
Entry
Substrate
Catalyst loading,
mg
Substrate/Pd
(mol/mol)
P (H2), atm.
Conv., %
TOF, hÀ 1
1
2
3
4
5
6
7
8
Styrene
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
1
41590
41590
103970
14465
21700
21700
27750
27750
41625
41625
2645
10
30
30
10
10
30
10
30
10
30
10
10
62
100
50
100
33
64
103140
166365
207945
57870
28645
55555
88805
105455
37465
146525
105
4-methylstyrene
4-tert-butylstyrene
80
95
9
22.5
88
10
11
12
4-phenylstyrene
trans-stilbene
4 [b]
6 [b]
1
2645
160
0
[a] Reaction conditions are: 80 C, 15 min. [b] 1 h.
The lowest conversion for 4-phenylstyrene in comparison
with its isomers, 1,1-diphenylethylene and trans-stilbene, can be
explained in terms of geometric factors: too closely located,
phenyl rings in the 4-phenylstyrene are perpendicularly
oriented to each other, minimizing the steric energy and, as a
consequence, sufficiently retarding the substrate adsorption. In
1,1-diphenylethylene molecule phenyl rings are located farther
from each other, facilitating the adsorption. In the trans-stilbene
molecule both C=C double bond and phenyl rings are located
in the same plane, making the adsorption the most favourable.
Increase in hydrogen pressure up to 30 atm. allowed to achieve
conversions of 77 and 100% for 1,1-diphenylethylene and
trans-stilbene respectively (Table 2).
Activity of the microporous G3-dendr-SiO2-Pd catalyst was
strongly affected by both electron and geometry factors (Fig-
ure 4), that was originated form its hindered structure
(Scheme 5). Thus, in the styrene hydrogenation turnover
frequency for G3-dendr-GlycdSiO2-Pd was comparable with that
for G2-dendr-meso-SiO2-Pd, reaching 103140 hÀ 1 at molar
substrate/Pd ratio of ~41560 and hydrogen pressure of 10 atm.
and 207945 hÀ 1 at molar substrate/Pd ratio of ~103970 and
hydrogen pressure of 30 atm. (Table 3). Then it dropped down
for 4-methylstyrene and rose again, when 4-tert-butylstyrene
was used as s substrate (4-tert-butylstyrene). In the last case
turnover frequency for G3-dendr-GlycdSiO2-Pd reached
88805 hÀ 1 at molar substrate/Pd ratio of ~14465 and 10 atm. of
H2 and 146525 hÀ 1 at molar substrate/Pd ratio of ~41625 and
30 atm. of H2 within 15 min. (Table 3), noticeably exceeding that
for G2-dendr-meso-SiO2-Pd (Table 2).
The phenomenon observed can be explained in terms of
strong +I-effect of the tert-butyl group, located oppositely to
C=C double bond in the side chain of 4-tert-butylstyrene
molecule (the concerted action of substituents). G3-dendr-SiO2-
Pd is characterized by less portion of Pd0 on its surface (Table 1,
Figure 1) and higher portion of small particles, having uncom-
pensated partly positive charge on their surface (Figure 6).
Therefore, the strong +I-effect of 4-tert-butylstyrene can play a
play key role in the preferential adsorption and the subsequent
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Figure 5. Recycling of G2-dendr-meso-SiO2-Pd and G3-dendr-SiO2-Pd in the hydrogenation of styrene. Reaction conditions: 0.5 mg of cat., 1500 μL of the
°
substrate (substrate/Pd � 36760 for G2-dendr-meso-SiO2-Pd and 41590 for G3-dendr-SiO2-Pd), 15 min., 80 C, 10 atm. of H2.
hydrogenation of the latter in comparison with 4-methylstyrene
and other bulky substrates.
were calculated with the use of time ranges, corresponding the
maximum slopes on the kinetic curves (Figure S15).
Extremely low conversions for rigid 4-phenylstyrene and
trans-stilbene (4 and 6% within 1 hour correspondingly,
Table 3) confirm our suggestion, as we think. Herein both
sterical factors (hindered catalyst structure, bulky and rigid
geometry of substrate) and electron factors (À M-substituents)
act together, resulting in the retarded hydrogenation.
G2-dendr-meso-SiO2-Pd and G3-dendr-SiO2-Pd were tested
on the possibility of recycling on the example of styrene
(Figure 5). The recycling test was performed analogously to a
standard hydrogenation procedure in the presence of heteroge-
neous dendrimer-based palladium catalysts.[32a,43] For the better
sedimentation of the catalyst and, therefore, for the prevention
of mechanical losses, the reaction products were additionally
Table 4. Hydrogenation of styrenes in the presence of meso-G2-dendr-
SiÀ Pd.[a]
Entry Substrate
Catalyst
loading,
mg
Substrate/ t,
Conv., TOF,
%
Pd
min
hÀ 1
(mol/mol)
1
2
3
4
5
6
7
Styrene
1
3010
6025
3145
60
30
15
60
30
15
60
100
96
27
96.5
69
22
8310
0.5
1
11325
1700
4-methylstyr-
ene
18.5
diluted with n-hexane, which is
a
poor solvent for
8
9
10
11
12
13
30
15
60
30
15
60
18
4.5
10
6.5
3.5
85.5
dendrimers.[32a,43] The resulting solution was separated by
decantation, and the remaining catalyst after sedimentation (~
30 min.) was used in the subsequent cycles without additional
loading and regeneration.
0.5
1
6285
3015
880
4-tert-butyl-
7595
styrene
This experiment revealed, that the catalysts said can be
used six or more times without significant loss in activity. Total
turnover number for eight cycles was 110280 for G2-dendr-
meso-SiO2-Pd and 148885 for G3-dendr-SiO2-Pd. Pd leaching
during the test did not exceed 0.5% according to ICP-AES.
Herein we suppose some mechanical losses of the catalysts as
inevitable due to their fine dispersity and very low initial
loading.
In contrast to G2-dendr-meso-SiO2-Pd and G3-dendr-SiO2-
Pd, meso-G2-dendr-Si-Pd revealed unexpectedly low activity in
the hydrogenation of styrene (Table 4, Figure 4). An induction
period was observed in the hydrogenation of all substrates
(Figure S14); therefore the TOF values for meso-G2-dendr-Si-Pd
14
15
16
17
18
19
20
30
15
60
45
30
15
60
81
18
72
62
20.5
9
95.5
0.5
1
6030
2300
8555
7030
4-phenylstyr-
ene
21
22
23
24
25
26
27
28
30
15
60
30
15
60
30
15
80
3.5
7
4.5
3
63
34.5
1.5
0.5
1
4595
2300
550
trans-stilbene
3030
0
[a] Reaction conditions are: 80 C, 10 atm. of H2.
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°
Figure 6. Hydrogenation of alkynes in the presence of the dendrimer-based organo-silica palladium catalysts. Reaction conditions are: 80 C, 15 min.
As seen from Figure S14 and Table 4, even slight increase in
molar substrate/Pd ratio from ~2300–3100 to 4600–6300
resulted in sharp decrease in the reaction rate for the most of
the substrates. Prolongation of the induction period was also
observed (Figure S14). We suppose, such behavior of the meso-
G2-dendr-Si-Pd catalyst can be connected with the predom-
inance of the oxidized Pd species on the surface (Table 1,
Figure 1). This supposal may be confirmed by the results of 4-
tert-butylstyrene hydrogenation, being significantly superior to
those of 4-methylstyrene. Herein 4-tert-butylstyrene by the
strong +I-effect was characterized.
The structure of meso-G2-dendr-Si carrier is expanded and
loose (Scheme 4). It resulted in elimination of the sterical factors
in the hydrogenation of bulky and rigid 4-phenylstyrene and
trans-stilbene (Figure 4, Table 4). Nonetheless, due to the À M-
effect of substituents, they are still inferior to 4-tert-butylstyrene
in their propensity to hydrogenation, that was especially
notable at increased substrate/Pd ratios (Table 4, Figure S14).
Selective hydrogenation of acetylene compounds is one of
the most important problems in petrochemistry, since they
poison polymerization catalysts.[59] Therefore, the catalysts
synthesized were tested in the hydrogenation of various
alkynes, such as phenylacetylene, 1-octyne, 4-octyne and 1-
hexyne. As seen from Figure 6, phenylacetylene was subjected
to hydrogenation in the significantly lesser degree in compar-
ison with linear alkynes for all catalysts tested.
rather large quantity, as compared with those of phenyl-
acetylene. On the other hand, alkyl substituents in the 1-octyne,
4-octyne and 1-hexyne molecules possess the weak +I-effect,
that facilitates substrate adsorption on Pd nanoparticles – in
contrast to weak À M-effect of phenyl ring in the phenyl-
acetylene molecule.[19b,32a]
The presence of basic dendrimer amino groups strengthens
polarization of terminal CÀ H bond near to the C�C triple bond
in phenylacetylene molecule and, as a consequence, the acidity
of the terminal proton. On the one hand, it leads to increase in
the electron density on the C�C triple bond and, as a
consequence, to the enhanced selectivity on styrene.[32a] On the
other hand, it favours to the predominant perpendicular
adsorption of phenylacetylene molecule, not suitable for the
subsequent hydrogenation to styrene. Nonetheless, due to the
dendrimer action, a portion of PhCH2À C�Pd and PhCH2À CH=Pd
adsorbed species,[57a,58] leading to ethylbenzene formation
decreases, replaced by surface PhÀ C�CδÀ À Pdδ+ complexes.[60]
As a result, the reaction turnover frequency decreases (Figure 6)
along with the styrene selectivity increased (Table 5).
Catalyst efficiency in the phenyl acetylene hydrogenation
was strongly influenced by the carrier structure and the reaction
conditions (substrate/Pd ratio, hydrogen pressure etc.). G3-
dendr-SiO2-Pd appeared as the most selective and efficient
catalyst among the others tested: the portion of styrene among
the reaction products reached 95–98% even at hydrogen
pressures of 30 atm. and was just slightly dependent on the
substrate/Pd ratio (Table 5). Herein the maximum TOF value
might reach 80995 hÀ 1 (Table 5, Entry 8), and the maximum
styrene yield was of 92% (conversion of 97%, selectivity of
95%) was achieved at substrate/Pd ratio of ~14455 and
hydrogen pressure of 30 atm. (Table 5, Entry 3).
These results can be explained in terms of both sterical and
electron factors. Thus, on the one hand, rigid phenylacetylene,
with its planar geometry, requires much larger adsorption area
for successful hydrogenation of the C�C triple bond, than
flexible linear alkynes. As a consequence, the same Pd nano-
particle can simultaneously adsorb linear alkyne molecules in
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Table 5. Hydrogenation of phenyl acetylene in the presence of the dendrimer-based organo-silica palladium catalysts.[a]
1
2
3
Pd0þPd=PdOx
Entry
Catalyst
d, nm
DM, %[b]
Substrate/Pd,
(mol/mol)
P (H2), atm.
Conv., %
TOF, hÀ 1
Selectivity
on styrene, %
PdOþPd2þ
4
5
6
7
8
9
1
2
3
4
5
6
7
8
G3-dendr-SiO2-Pd
2.81�0.71
31.5
1.2
7230
10
10
30
30
10
30
10
40
10
10
30
30
10
30
10
10
30
30
10
30
99.5
77
97
82
57
79
47
70
98
63
98
90
45.5
75
73
47
98
28780
44545
56115
59300
49465
68555
54380
80995
25055
32215
50115
57530
34900
57530
18350
23630
49279
69755
20610
53795
90.5
98
95
97
98
98
98
96
67
95.5
84
90.5
96.5
92
92
98
87.5
91.5
98
14455
14455
18070
21680
21680
28910
28910
6390
12785
12785
15980
19175
19175
6285
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
9
G2-dendr-meso-SiO2-Pd
meso-G2-dendr-Si-Pd
3.29�0.34
2.71�0.44
26.9%
32.6%
4.4
2.5
10
11
12
13
14
15
16
17
18
19
20
12570
12570
18850
25135
25135
92.5
20.5
53.5
93.5
°
[a] Reaction conditions are: 0.5 mg of catalyst, 80 C, 15 min;
[2g]
0:885
[b] Particle dispersity DM can be calculated according to the formula: DM
¼
,
where d is mean particle diameter, expressed in nm, and 0.885 is a Pd
reduced factor, corresponding to the ratio of the atomic phase volume vM todthe average atomic effective area aM on the particle surface.[61] It can be
�
Ar
M
aM
calculated according to the formula:
¼
.
Na���aM
Mesoporous catalysts G2-dendr-meso-SiO2-Pd and meso-G2-
dendr-Si-Pd, based on PPI dendrimers of 2nd generation, were
noticeably inferior to G3-dendr-SiO2-Pd in both activity and
selectivity (Figure 6, Table 5). The maximum styrene yield of
81.5% (conversion of 90%, selectivity of 90.5%) for G2-dendr-
meso-SiO2-Pd catalyst, as well as TOF values of 57530 hÀ 1, can
be achieved at molar substrate/Pd ratio of ~15980 and hydro-
gen pressure of 30 atm. within 15 minutes (Table 5, Entry 12). In
the case of meso-G2-dendr-Si-Pd the best conditions for the
selective phenyl acetylene hydrogenation were the substrate/
Pd ratio of ~18850 and hydrogen pressure of 30 atm., allowing
to achieve the styrene yield of 84.5% within 15 minutes
(conversion of 92.5%, selectivity of 91.5%) at TOF value of
69755 hÀ 1 (Table 5, Entry 18).
dendrimers of the 3rd and higher generation are presumably
located closely to each other. It results in Pd nanoparticles,
stabilized by the large amount of donor amino groups
simultaneously.[1a,16,32a] As a consequence, Pd surface is partly
filled with electrons and much stronger adsorbs phenylacety-
lene with its high electron density on the C�C triple bond
(additionally polarized by the interactions with the basic
dendrimer amino groups) in comparison with styrene, resulting
both in higher reaction rate and selectivity on styrene.[32a,58b,65]
Herein for organo-silica dendrimer-based catalysts a positive
dendritic effect was observed: the more dendrimer’s generation,
the more donor amino groups it has and, as a consequence, the
more stabilized and electron-enriched nanoparticles appearing
to be.
We think our supposal to be indirectly confirmed by the
results of the selective 1-hexyne hydrogenation in the presence
of Pd nanoparticles, stabilized by imidazolium-modified 2,2’-
bipyridyl.[66] Herein alkenes formed were not subjected to the
further hydrogenation even at quantitative conversions and
long reaction times (4–8 hours). It was established, that
adsorption constants decreased in the following order: K1
(alkyne) > K (nitrogen ligand)@K2 (alkene).
Addition of piperidine allowed not only to maintain high
selectivity on 1-butene in 1-butyne hydrogenation, but also to
noticeably increase the reaction rate for small particles in
comparison with the reference Pd/Al2O3 catalyst.[65c] PAMAM
dendron-stabiliized bimetallic PtPd nanoparticles effectively
catalyzed methylphenylacetylene hydrogenation to β-methyl-
styrene with the yield of 94%.[18b] Analogously poly(ethylene
imine) based Pd-containing catalysts, both homogeneous and
heterogeneous, allowed to obtain cis-stilbene from diphenyla-
cetylene in 1,4-dioxane medium with the selectivity of 94–97%,
As one can see from Table 5, there is no certain dependency
between catalyst efficiency and mean particle diameter, typical
for many both homogeneous[62] and heterogeneous
catalysts[6c,63] and connected with the ratio of [111] (active in
phenylacetylene hydrogenation) and [110] planes (active in
phenylacetylene
adsoption
and
complex
formation).[6c,57a–b,58b,63–64] Analogously catalyst activity does not
seem to be influenced by the ratio of reduced and oxidized
valency states on the surface of Pd nanoparticles (Table 5).
Moreover, the catalyst G3-dendr-SiO2-Pd, characterized by the
lowest Pd0/(PdO+Pd2+) ratio, appeared as the most active and
selective in the phenyl acetylene hydrogenation, whereas
oxidized Pd forms are known decrease selectivity on styrene.[43]
Therefore, we assume the carrier structure and ligand
microenvironment appear to be the main factors, influencing
the activity and selectivity of the dendrimer-based organo-silica
palladium catalysts. Indeed, in the microporous G3-dendr-SiO2-
Pd catalyst, prepared in the absence of polymeric template, PPI
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which did not decrease even at very long reaction times (10–
40 hours) and quantitative conversions.[13,67]
Increase in substrate/Pd ratio led to the predominance of
kinetic control, appearing in increase of the total alkene fraction
among the reaction products and lowering the isomerization
degree, while the rise of hydrogen pressure resulted in slight
increase of alkane and isomer portions (Tables S4 and S5).
Moreover, hydrogen pressure had a significant influence on the
efficacy of the alkyne hydrogenation (Figure 6). The more
noticeable it was for mesoporous G2-dendr-meso-SiO2-Pd and
meso-G2-dendr-Si-Pd catalysts, allowing to increase the reaction
turnover frequency by 2.5–8.5 times (Figure 6, Tables S4 and
S5). This is typical for heterogeneous Pd catalysts[6c,69] and may
be explained by the fact, that in mesoporous catalysts, based
on PPI dendrimers of the 2nd generation, have enough free
space, that can be occupied by both substrate molecules and
adsorbed hydrogen species, thus favouring to the hydro-
genation process. The adsorption density here also increases.
For microporous G3-dendr-SiO2-Pd catalyst increase in
hydrogen pressure from 10 to 30 atm. gives increase in the
reaction efficiency only by 1–1.5 times (Figure 6, Tables S4 and
S5). This may be due to initial higher local ligand to Pd ratio,
originated from PPI dendrimers of the 3rd generation, constitut-
ing the ligand basis of the G3-dendr-SiO2-Pd catalyst, and the
predominance of small particles (Figures 3). Moreover, G3-
dendr-SiO2-Pd allowed to obtain higher conversions and, as a
consequence, higher TOF values at lower hydrogen pressures
even at the highest substrate/Pd ratios (Figure 6, Tables S4 and
S5). It was especially remarkable for 1-octyne, for which
conversion and TOF at 10 atm. of H2 reached 98% and
316545 hÀ 1 respectively (substrate/Pd ~80750, 15 min.), there-
fore being remarkably superior to that for both G2-dendr-meso-
SiO2-Pd and meso-G2-dendr-Si-Pd at 30 atm. of H2 (TOF
~17130–211900 hÀ 1 at substrate/Pd of ~70170–71400, within
15 min.) (Figure 6, Table S5).
This phenomenon can be explained in terms of hindered
catalyst structure, retarding the substrate molecules and, there-
fore, increasing their local density. As a consequence, the
probability of substrate adsorption on Pd nanoparticles in-
creases in comparison with more expanded mesoporous
catalysts. By the careful adjusting the reaction conditions, it was
possible to reach high terminal alkene yield (�90%) for all
catalysts tested.
Similar to phenylacetylene, 1-octyne and 1-hexyne, at high-
est substrate/Pd ratios, when alkyne not consumed completely,
caused slight Pd leaching from catalysts, that is typical for
terminal alkynes due to the complex formation.[60] At the same
time, the reasonable selectivity on alkene (� 90%) for 1-octyne
and 1-hexyne can be achieved only at much higher substrate/
Pd ratios, than for phenylacetylene (Tables S4 and S5). This may
be due to the flexible structure of linear alkynes and their semi-
hydrogenation products, resulting in their retarding by den-
drimer branches, whereas rigid and planar phenylacetylene
moves apart the denrimers branches, thus providing the free
space for the fast desorption of styrene formed.
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Another important advantage for the use of N-containing
donor ligands is the suppression of alkyne polymerization,
typical for small particles (< 4 nm), especially at high substrate/
Pd ratios.[63a,68] Herein ligands presumably occupy low coordina-
tion electron-deficient adsorption sites, characterized by the
lowest selectivity in alkyne hydrogenation.[63a,66]
All catalysts studied appeared to be inferior to the
amorphous Pd-G3-dendr@BP-1 catalyst, based on PPI den-
drimers of the 3rd generation,[43] but surpassed it in the
selectivity on styrene. As we think, this difference in behavior
for the catalysts with the similar composition may originate
from the features of Pd nanoparticles localization in the carrier.
In Pd-G3-dendr@BP-1 both dendrimers and Pd nanoparticles
are located only on the outer surface of the carrier:[43] it results
in the better substrate access to catalytic centers in comparison
with catalysts, where Pd nanoparticles are predominantly
located in pores or in the network cavities. On the other hand,
due to its outer surface localization, Pd nanoparticles in the Pd-
G3-dendr@BP-1 catalyst are less coated with the dendrimer
amino groups and, as a consequence, appeared less selective in
the phenylacetylene hydrogenation, especially as compared
with G3-dendr-SiO2-Pd catalyst.
With respect to alkynes, the reaction turnover frequency as
well as alkene selectivity was additionally influenced by the
substrate size and C�C triple bond position in the alkyne
molecule. As seen from Figure 6, linear 1-octyne and 1-hexyne
were hydrogenated with much better efficacy, than that for
phenylacetylene, with 1-hexyne hydrogenated much faster as
less-size substrate. The maximum TOF value appeared as
404415 hÀ 1 for G3-dendr-SiO2-Pd catalyst at molar substrate to
Pd ratio of ~103700 and hydrogen pressure of 30 atm. within
15 minutes (Table S4, Entry 5). Mesoporous catalysts G2-dendr-
meso-SiO2-Pd and meso-G2-dendr-Si-Pd again revealed the
similar activity, giving maximum TOF values for 1-hexyne of
about 234300–276805 h-1 at substrate/Pd ratios of 90100–
91600 and hydrogen pressure of 30 atm. within 15 minutes
(Table S4, Entries 13 and 19).
As in the case of phenylacetylene hydrogenation, the
selectivity on terminal alkene was strongly dependent on both
reaction conditions (substrate/Pd ratio, hydrogen pressure) and
catalyst structure. At low substrate/Pd ratios thermodynamic
reaction control prevailed, resulting in high isomerization
degrees for rest alkenes among the reaction products (Tables S4
and S5).
Isomerization of the C=C double bond position is the typical
process for linear alkenes in the presence of Pd catalysts.[19d] It
was especially noticeable for the products of less-size 1-hexyne
hydrogenation (Table S4). Herein G3-dendr-SiO2-Pd catalyst
favoured for the maximum isomerization degree among the
other catalysts (Table S4). This phenomenon can be explained
in terms of highly branched moieties of PPI dendrimers of the
3rd generation, those retarded alkenes formed in close proximity
of Pd nanoparticles, making the formers undergo the further
isomerization.
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The second possible reason is the less polarization of
terminal CÀ H bond due to the +I-effect of substituent near to
C�C triple bond in the linear alkyne molecule – as compared
with phenylacetylene one with À M-effect of phenyl ring. As a
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°
Figure 7. Hydrogenation of dienes in the presence of the dendrimer-based organo-silica palladium catalysts. Reaction conditions: 80 C, 15 min.
consequence, the difference between electron densities on C�C
and C=C bonds with alkyl substituents is diminished, resulting
in facilitated readsorption of alkene formed. We think, this
supposal is confirmed by the results of 4-octyne hydrogenation,
whose internal C=C triple bond has two +I- substituents from
both sides and cannot be polarized.
which allowed to achieve near-to-quantitative yield of 4-octene
by carefully adjusting the reaction conditions under the
thermodynamic reaction control,[44] but also with monometallic
supported Pd/SiO2 and Pd/Al2O3 catalysts, providing the
selective hydrogenation of diphenylacetylene to cis-
stilbene[3c,70]
.
As seen from Figure 6, when 4-octyne is hydrogenated in
the presence of G2-dendr-meso-SiO2-Pd catalyst, the reaction
TOF reaches values as high as 243980 hÀ 1 at substrate/Pd ratio
of ~71760 and 30 atm. of H2 within 15 minutes, that is just
slightly less (Table S6, Entry 10), than for 1-hexyne (Table S4,
Entry 13). We assume, this phenomenon is originated both from
less hindered mesoporous structure of G2-dendr-meso-SiO2-Pd,
providing the well access for substrate molecules to Pd nano-
particles, and from internal position of C�C triple bond,
surrounded by two +I-substituents. This assumption is con-
firmed by the fact, that for G3-dendr-SiO2-Pd and meso-G2-
dendr-SiÀ Pd, with more hindered structures, activity for 4-
octyne, with the internal C�C triple bond, sharply decreased, as
compared with terminal 1-octyne and 1-hexyne, and did not
exceed 194840 hÀ 1 (Figure 6, Table S6, Entry 5).
Another remarkable difference in the 4-octyne hydrogena-
tion is the predominance of octane among the reaction
products for all catalysts even at highest substrate/Pd ratios
(Table S6). In the presence of dendrimer moieties on the carrier
surface internal alkyne is retarded to adsorb and, as a
consequence, its semi-hydrogenation products with the internal
C=C bonds are retarded to desorb away. It resulted in the
subsequent hydrogenation of alkenes formed and correspond-
ing high portion of n-octane among the reaction products
(Table S6) in comparison not only with bimetallic PdAg-G3-
dendr@BP-1[44] and monometallic MPF-PPI-G3-Pd catalysts,[46]
In the hydrogenation of dienes several main features may
be marked. Flexible and tiny isoprene and 2,5-dimethyl-2,4-
hexadiene, as well as small 1,3-cyclohexadiene (which is partly
isomorphic to 2,5-dimethyl-2,4-hexadiene in cis-conformation)
were hydrogenated with high efficacy, reaching the TOF values
of 100000–400000 hÀ 1 (Figure 7, Tables S7–S9), sharply exceed-
ing those not only for traditional heterogeneous catalysts, but
also for the materials, based on PPI or PAMAM dendrimers,
grafted to amorphous silica surface[34b,43] or dendritic
networks.[32a]
In contrary, bulky 1,3- and 1,5-cyclooctadienes were hydro-
genated very slowly: their conversion after 1 hour does not
reach 100% for all catalysts at minimal substrate/Pd ratios (~
2800–3200). Herein 1,5-cyclooctadiene very often underwent
isomerization to conjugated 1,3-cyclooctadiene, that was the
appearance of the reaction thermodynamic control. The
predominant reaction product for G2-dendr-meso-SiO2-Pd and
G3-dendr-SiO2-Pd catalysts was cyclooctane, whereas the liter-
ature reports, as a rule, about the cyclooctene formation in the
presence of dendrimer-based catalysts.[18,21,34b,71]
Trans-cyclooctene with the selectivity of ~5% was detected
for less active G3-dendr-SiO2-Pd catalyst only in the beginning
of the reaction, at conversion not exceeding 10% (Figure S15).
It should also be noted, that the literature data are referred
mostly to the homogeneous catalysts, tested at the ambient
temperature and pressure.[18,21,34b,71]
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Scheme 6. Product distribution in the hydrogenation of conjugated dienes in the presence of the dendrimer-based organo-silica palladium nanocatalysts.
At the same time, unexpectedly high selectivity on cyclo-
octenes was revealed in the presence of meso-G2-dendr-Si-Pd
catalyst. Herein 1,3-cyclooctadiene, for which the induction
period was observed (Figure S16), gave predominantly trans-
cyclooctene with the selectivity of 85–90% at conversion of 44–
46% within 0.5–1 hour. Trans-cyclooctene formation may origi-
nate from simultaneous adsorption of 1,3-cyclooctadiene on
both C=C double bonds.[67] Vice versa, 1,5-cyclooctadiene gave
predominantly cis-cyclooctene with the selectivity of 80–90% in
the beginning of the reaction (Figure S17, Table S9), that was
the result of the adsorption only by one C=C bond. Nonethe-
less, this cis-cyclooctene, due to its configuration, suitable for
readsorption, easily underwent further hydrogenation to cyclo-
octane: the portion of the latter reached 92% at 1,5-cyclo-
octadiene conversion of 22% within 1 hour.
The results, obtained for meso-G2-dendr-Si-Pd, may eluci-
date the main features of cyclooctadiene hydrogenation in the
presence of other dendrimer-based heterogeneous catalysts.
Indeed, in the presence of severely hindered G3-dendr-SiO2-Pd
catalyst 1,3-cyclooctadiene have not enough space for simulta-
neous adsorption on both two C=C double bonds; as a
consequence, its hydrogenations proceeds similar to 1,5-cyclo-
octadiene, with the formation of cis-cyclooctene as an inter-
mediate product. The latter, being as less stable, tense cycle,
fast undergoes the subsequent hydrogenation to cyclooctane,
possibly without desorption and readsorption act (maintaining
as adsorbed species on Pd surface).
Hydrogenation in the presence of mesoporous, less hin-
dered G2-dendr-meso-SiO2-Pd catalyst apparently proceeds in
the same way. It may indicate, that Pd nanoparticles in this
sample, though less intricated by dendrimer branches, nonethe-
less, have similar environment and shape, interfering the
simultaneous double adsorption for 1,3-cyclooctadiene. There-
after, meso-G2-dendr-Si-Pd has respectively to consist of
ensembles (Figure S18), similar to those in homogeneous
catalysts, providing the selective formation of cyclooctene.
Hydrogenation of flexible linear or branched conjugated
dienes, such as isoprene or 2,5-dimethyl-2,4-hexadiene, pro-
ceeded according Scheme 6. Herein the product distribution
was determined by the stability of corresponding π-allyl
intermediates (Figure S19), being formed at the first stage of
hydrogenation, and was additionally affected by such factors, as
mean particle size, local ligand/Pd ratio etc.[68]
The use of lower substrate/Pd ratios as well as increase in
hydrogen pressures favoured to thermodynamic reaction con-
trol, resulting in increased portions for corresponding alkane
and thermodynamically the most stable internal alkene, being
the products of 1,4-addition (2-methyl-2-butene, 2,5-dimethyl-
trans-3-hexene) (Tables S7–S9) – in contract to Pd nanocatalyst,
based on arylcarbosilane triazol-containing dendrimers[21]
–
while the rise of substrate/Pd ratio furthered correspondingly to
increased portions for 1,2-addition products, being thermody-
namically less stable terminal alkenes (2-methyl-1- and 3-
methyl-1-butenes) or cis-isomers of internal alkenes (2,5-
dimethyl-cis-3-hexene) (Tables S7–S9). In the last case the
substrate, being in large excess, easily replaced olefin formed.
As a result, the latter is desorbed without undergoing further
hydrogenation or isomerization.[43,71] On the other hand,
thermodynamically less stable products of the kinetic control,
as a rule, sterically less hindered (2-methyl-1- and 3-methyl-1-
butenes) and geometrically more suitable for readsorption (2,5-
dimethyl-cis-3-hexene), were subjected to hydrogenation in the
first instance. In the case of symmetrical and cyclic 1,3-
cyclohexadiene both 1,2- and 1,4-addition of hydrogen resulted
to the same product, cyclohexene (Figure S19). Similar phenom-
enon was earlier observed in the hydrogenation of isoprene in
the presence of homogeneous Pd2(Ph2PCH2PPh2)3 catalyst at
various substrate/Pd ratios.[72]
It should be noted, that the presence of PPI dendrimers as
anchored ligands allowed not only to avoid the diene
chemisorption and, as a consequence, polymerization and
substrate inhibition, typical for small particles (< 4 nm),
especially at high substrate/Pd ratios,[63a,68] but also to maintain
high total selectivity on olefins (90–99%) (Tables S7–S9). PPI
dendrimers, due to the electron-donor properties of their amino
groups, not only displace alkene formed from palladium
surface, but also prevent readsorption of the latter (olefins are
less electron rich in contrast to conjugated dienes), thus
preventing the coke formation and polymerization of substrate
and its semi-hydrogenation products.[73]
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Figure 8. Recycling of G3-dendr-SiO2-Pd in the hydrogenation of 1,3-cyclohexadiene and 2,5-dimethyl-2,4-hexadiene. Reaction conditions are: 0.5 mg of
°
catalyst, 750 μL of 1,3-cyclohexadiene (substrate/Pd � 25005) or 1500 μL of 2,5-dimethyl-2,4-hexadiene (substrate/Pd � 33425), 15 min., 80 C, 10 atm. of H2.
The activity of the catalysts synthesized in the hydro-
genation of conjugated dienes decreased in the following
order: G3-dendr-SiO2-Pd > G2-dendr-meso-SiO2-Pd @ meso-G2-
dendr-Si-Pd (Figure 7). For mesoporous G2-dendr-meso-SiO2-Pd
and meso-G2-dendr-Si-Pd catalysts size and geometry of the
substrate appeared as main factors, determining their exposure
to hydrogenation (Figure 7). Therefore, small 1,3-cyclohexa-
diene with the rigid geometry (rotation of C=C double bonds is
impossible) underwent hydrogenation faster, than others. Also
small isoprene, but containing a substituent in central position
at C=C double bond, was interfered to adsorb and, as a result,
hydrogenated more slowly. Respectively, more hindered 2,5-
dimethyl-2,4-hexadiene was more inferior to isoprene in the
tend to hydrogenation. At such size and structure dependency
it is obvious the poor activity of heterogeneous dendrimer-
based catalysts in the hydrogenation of cyclooctadienes (Fig-
ure 7). For G2-dendr-meso-SiO2-Pd the thermodynamic control
was predominant, resulting in higher portions for the products
of 1,4-addition even at highest substrate/Pd ratios (Table S7).
As earlier for styrenes and alkynes, the electron factors
appeared as the crucial, when G3-dendr-SiO2-Pd was used as
the catalyst, even overbalancing the sterical factors, being
expectable as more important for catalyst with such hindered
structure. Thus, we can see, that the most substituted 2,5-
dimethyl-2,4-hexadiene, being able to form the most stable π-
allyl intermediates (Figure S19), was hydrogenated with the
efficacy, just slightly superior to that for less substituted
isoprene (Figure 7). The last, in its turn, was slightly superior to
1,3-cyclohexadiene, which cannot form tertiary, the most stable
π-allyl intermediates (Figure S19). We attribute this tendency for
G3-dendr-SiO2-Pd catalyst to interact better with donor sub-
strates, able to form more stable intermediates, to the
predominance of small particles (Figure 3), characterized by the
partial positive charge on the surface.[63a,68] G3-dendr-SiO2-Pd
was influenced by the kinetic control, appearing in higher
portions for the products of 1,2-addition not only at highest
substrate/Pd ratios (Table S8).
G3-dendr-SiO2-Pd was tested on the possibility of diene
recycling on the examples of 1,3-cyclohexadiene and 2,5-
dimethyl-2,4-hexadiene (Figure 8). The recycling test revealed
the slight, gradual decrease of activity, that might be caused
mostly by the mechanical losses of the catalyst under the
conditions, at which reaction becomes sensitive even to slight
increase in substrate/Pd ratio. Leaching portion did not exceed
1% according to ICP-AES. Herein total selectivity on alkenes
maintained at 96–99.5%. Total turnover number for six cycles
reached 125405 for 1,3-cyclohexadiene and 169130 for 2,5-
dimethyl-2,4-hexadiene.
Increase in hydrogen pressure up to 30 atm. allowed to
increase TOF values in diene hydrogenation by 1.3–1.7 times for
G2-dendr-meso-SiO2-Pd and by 2.4–3 times for G3-dendr-SiO2-
Pd (Figure 7, Tables S7 and S8). Herein the total selectivity on
olefin maintained still high, dropping only by 1–5%. Analogous
tendency was also the characteristic of alkyne hydrogenation in
the presence of the dendrimer-based organo-silica Pd nano-
catalysts, studied in this work (Tables S4–S6). This compares
dendrimer-based organo-silica Pd nanocatalysts favourably with
traditional heterogeneous Pd catalysts (including Lindlar
catalyst).[74] In spite of the fact, that the latters allow to achieve
selectivities on alkene as high as 85–100% and TOF values of
30000–100000 hÀ 1 in some cases, reactions in their presence are
carried out, as a rule, at ambient temperatures and pressures
(Tables S10–S11) and have to be stopped at conversions of 70–
90% to avoid overhydrogenation, that becomes inevitable,
when the most portion of alkyne or diene is consumed.[58a,63b,74]
Herein increase in temperature or pressure obviously results in
accelerating the reaction rate and further downfall in the
selectivity on alkene.[3b,64c]
In the case of meso-G2-dendr-Si-Pd, increase in hydrogen
pressure did not result in the sufficient rise of efficacy (only by
1–1.2 times), when isoprene and 2,5-dimethyl-2,4-hexadiene
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Scheme 7. Stepwise hydrogenation of dicyclopentadiene in the presence of Pd catalysts.[32a]
were used as substrates (Figure 7, Table S9). We assume, it may
be connected with the adsorption features or nanoparticle local
microenvironment, interfering the efficient hydrogenation (and
simultaneously providing high selectivity on cyclooctene, when
1,3-cyclooctadiene was used as the substrate). In general, meso-
G2-dendr-Si-Pd appeared as poor catalyst for conjugated diene
hydrogenation as compared with G2-dendr-meso-SiO2-Pd and
G3-dendr-SiO2-Pd. It tended to thermodynamic control in 2,5-
dimethyl-2,4-hexadiene hydrogenation, resulting in higher
portions for the products of 1,4-addition even at highest
substrate/Pd ratios (Table S9), and to kinetic control in the
isoprene hydrogenation, giving to portions of 2-methyl-1-
butene, 3-methyl-1-butene and 2-methyl-2-butene, close to the
classical 1:1:2 (Table S9).[68]
Hydrogenation of unconjugated dicyclopentadiene pro-
ceeded stepwise (Scheme 7).[32a] The double bond, located
opposite to the methylene bridge, primarily underwent hydro-
genation due to its less sterical hindrance and geometrical
Figure 9. Adsorption of dicyclopentadiene molecule on the surface of
palladium nanoparticle, stabilized by PPI dendrimers.[32a
strain (Figure 9).[32a,75] Herein the configuration of initial dicyclo-
pentadiene was retained. In contrast to the earlier published
heterogeneous Pd catalysts, based on the dendrimer
networks,[32a] organo-silica Pd catalysts appeared much higher
activity in the dicyclopentadiene hydrogenation along with the
lowered selectivity on dihydrodicyclopentadiene (Tables 6 and
7).
]
to quantitative conversions of dicyclopentadiene (~95%) within
15 minutes (Table 7). However, this dihydrodicyclopentadiene
easily underwent the subsequent hydrogenation to tetrahydro-
dicyclopentadiene with the prolonged reaction time (Figure 10),
that was typical for traditional supported Pd catalysts (Pd/C, Pd/
Al2O3 and Pd/SiO2).[76]
Another feature of the dendrimer-based organo-silica Pd
catalysts in the hydrogenation of dicyclopentadiene was the
high portion of retro-diene decay. In the case of G2-dendr-
meso-SiO2-Pd it reached 32% and appeared only at highest
substrate/Pd ratios and the lowest dicyclopentadiene conver-
sions (Table 6). When G3-dendr-SiO2-Pd used as the catalyst, a
small portion of the retro-diene decay appeared even at
quantitative dicyclopentadiene conversions and initially sharply
increased with the increase in substrate/Pd ratio (the maximum
of 30% was observed at substrate/Pd ~18020) and then
Thus, the portion of tetrahydrodicyclopentadiene, the
product of exhausting hydrogenation of dicyclopentadiene, in
the presence of G2-dendr-meso-SiO2-Pd catalyst reached 95%
within 15 minutes at molar substrate/Pd ratio of ~2655 and
10 atm. of hydrogen (Table 6), while in the presence of Pd
nanoparticles, encapsulated into dendritic networks it was only
5–10% even at less substrate/Pd ratios.[32a] Increase in the latters
led to the corresponding increase in dihydrodicyclopentadiene
portion; nonetheless, there also took place the abrupt downfall
in conversion (Table 6).
The use of G3-dendr-SiO2-Pd catalyst, containing in its
structure more hindered dendrimers of the 3rd generation with
larger amount of donor amino groups, allowed to achieve the
higher selectivity on dihydrodicyclopentadiene (~95%) at near
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Table 6. Hydrogenation of dicyclopentadiene in the presence of G2-dendr-meso-SiO2-Pd catalyst.[a]
1
2
3
Entry
Catalyst loading, mg
Substrate/Pd
(mol/mol)
Conv., %
TOF, hÀ 1
Product distribution, %
4
5
6
7
8
9
1
2
3
4
5
6
1
2655
100
100
99.5
96
10620
21240
42265
81560
53525
50975
Dihydrodicyclopentadiene 5%
Tetrahydrodicyclopentadiene 95%
Dihydrodicyclopentadiene 28.5%
Tetrahydrodicyclopentadiene 71.5%
Dihydrodicyclopentadiene 57%
Tetrahydrodicyclopentadiene 43%
Dihydrodicyclopentadiene 85.5%
Tetrahydrodicyclopentadiene 14.5%
Dihydrodicyclopentadiene 93%
Tetrahydrodicyclopentadiene 7%
Dihydrodicyclopentadiene 62%
Tetrahydrodicyclopentadiene 6%
Cyclopentadiene 1%
0.5
0.5
0.5
0.5
0.5
5310
10620
21240
42480
70800
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
31.5
18
Cyclopentene 23%
Cyclopentane 8%
0
[a] Reaction conditions are: 80 C, 10 atm. of H2, 15 min.
Table 7. Hydrogenation of dicyclopentadiene in the presence of G3-dendr-SiO2-Pd catalyst.[a]
Entry
Catalyst loading, mg
Substrate/Pd
(mol/mol)
P (H2), atm.
Conv., %
TOF, hÀ 1
Product distribution, %
1
1
3005
10
99.5
11955
23910
70645
90350
59115
100925
24990
98040
Dihydrodicyclopentadiene 42%
Tetrahydrodicyclopentadiene 55.5%
Retro-diene decay 2.5%
Dihydrodicyclopentadiene 69%
Tetrahydrodicyclopentadiene 17.5%
Retro-diene decay 13.5%
Dihydrodicyclopentadiene 66%
Tetrahydrodicyclopentadiene 4%
Retro-diene decay 30%
Dihydrodicyclopentadiene 94%
Tetrahydrodicyclopentadiene 4.5%
Retro-diene decay 1.5%
Dihydrodicyclopentadiene 95%
Tetrahydrodicyclopentadiene 3%
Retro-diene decay 2%
Dihydrodicyclopentadiene 90%
Tetrahydrodicyclopentadiene 9%
Retro-diene decay 1%
Dihydrodicyclopentadiene 90.5%
Tetrahydrodicyclopentadiene 2.5%
Retro-diene decay 7%
Dihydrodicyclopentadiene 93%
Tetrahydrodicyclopentadiene 5%
Retro-diene decay 2%
2
3
4
5
6
7
8
0.5
0.5
0.5
0.5
0.5
0.5
0.5
6010
10
10
10
10
30
10
30
99.5
98
18020
24030
48060
48060
64080
64080
94
41
70
13
51
°
[a] Reaction conditions are: 80 C, 15 min.
abruptly downfall (Table 7). Increase in hydrogen pressure led Conclusions
to the decrease in the retro-diene decay portion (Table 7).
Hence, one may assume, that retro-diene decay occurs on
the walls of silica pores, possessing a some of acidity. For its
appearance the highest substrate/Pd ratio is required, when the
mesoporous material G2-dendr-meso-SiO2-Pd is used as the
catalyst. For much more hindered microporous G3-dendr-SiO2-
Pd it appears already at low and moderate substrate/Pd ratios,
however the further increase in substrate/Pd ratio presumably
results in displacement of the adsorbed species from the carrier
surface before they succeed to undergo retro-diene decay.
New hybrid organo-silica Pd-containing nanocatalysts, based on
poly(propylene imine) dendrimers, have been synthesized using
co-hydrolysis of the silane-modified dendrimer moieties in situ.
Herein the synthesis can be performed either with or without
addition of tetraethoxysilane, in the presence or in the absence
of polymeric template.
Thus prepared catalysts were examined in the hydrogena-
tion of various unsaturated compounds: styrenes, alkynes and
dienes. The activity and selectivity of these catalysts were found
to depend on the carrier structure, substrate size and geometry,
as well as on the electron properties.
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°
Figure 10. Hydrogenation kinetics of dicyclopentadiene in the presence of G3-dendr-SiO2-Pd catalyst. Reaction conditions are: 80 C, 10 atm. of H2.
Mesoporous G2-dendr-meso-SiO2-Pd catalyst, synthesized in
presence of template with the addition of tetraethoxysilane,
revealed the maximum activity in the hydrogenation of
styrenes, reaching TOF values of about 230000 hÀ 1. Due to the
larger particle size and much larger pore diameter, as well as
due to the highest portion of Pd0 on the nanoparticle surface, it
favoured to the quantitative conversions for bulky and rigid
substrates with À M-substituents, such as trans-stilbene, 4-
phenylstyrene and 1,1-diphenyl ethylene.
Microporous catalyst G3-dendr-SiO2-Pd, based on PPI den-
drimes of the 3rd generation and synthesized with the addition
of tetraethoxysilane, but in the absence of template, appeared
as the most active in terminal alkyne and flexible and small Experimental Section
conjugated diene hydrogenation, reaching TOF values more
catalyst, providing the trans-cyclooctene formation with the
selectivity of 90–95%, having elucidated the mechanism of
cyclooctadiene hydrogenation. This makes it similar to both
homogeneous and heterogeneous dendrimer-based catalysts,
described in literature.
Pd-containing dendrimer-based organo-silica nanocatalysts
can be easily separated from the reaction products and reused
several times without significant loss in activity. However their
apparent stability depends on the reaction sensitivity to the
substrate/Pd ratio.
than 400000 hÀ 1 for 1-hexyne and 2,5-dimethyl-2,4-hexadiene.
Herein the high selectivity on alkene (90–99%) was maintained
even at hydrogen pressure of 30 atm. The main feature of this
catalyst was the predominance of small particles (~0.9–2 nm) in
the structure and, as a consequence, the strong influence by
the electron factors, resulting in the unexpectedly high activity
for the bulky, long and hindered substrates with +I-substitu-
ents, such as 4-tert-butylstyrene, 1-octyne and 2,5-dimethyl-2,4-
hexadiene. Herein the moieties of 3rd generation PPI den-
drimers, containing the large amount of donor amino groups,
provided the better Pd nanoparticle stabilization and, as a
consequence, the highest selectivity on alkenes in the hydro-
genation of terminal alkynes and tiny and flexible conjugated
dienes.
Chemicals
The following substances were used as substrates and reference
compounds: phenylacetylene C6H5CH�CH (Aldrich, 98%); styrene
C6H5CH=CH2 (Aldrich,�99%); ethylbenzene C6H5CH2CH3 (Reachim,
Purum); p-methylstyrene p-CH3C6H4CH=CH2 (Aldrich, 96%); p-tert-
butylstyrene p-(CH3)3CC6H4CH=CH2 (Aldrich, 94%); 2,5-dimethyl-2,4-
hexadiene (CH3)2C=CH–CH=C(CH3)2 (Aldrich, 98%); isoprene H2C=C
(CH3)À CH=CH2 (Aldrich, 99%); 1,3-cyclohexadiene (Aldrich, 97%);
dicyclopentadiene C10H12 (Aldrich, 97%).
Ethanol C2H5OH (IREA 2000, Analytical Grade), methanol (Acros
Organics, 99.9%), chloroform CHCl3 (Chimmed, Reagent Grade) and
n-hexane n-C6H14 (Chimmed, Reagent Grade) were used as solvents.
For the synthesis of hybrid dendrimer-based catalysts the following
substances were used: Pd acetate (II) Pd(OAc)2 (Aldrich, 99.9%);
poly(propylene imine) (PPI) dendrimers of the 2nd generation with a
diaminobutane core DAB(NH2)8, earlier prepared according to
literature procedure;[77] (3-glycidoxypropyl)trimethoxysilane (Acros
Organics,�97%); poly(ethylene glycol)-block-poly(propylene gly-
col)-block-poly(ethylene glycol) with the average number molecular
The catalyst meso-G2-dendr-Si-Pd, prepared in presence of
template, but without addition of tetraethoxysilane, appeared
as significantly inferior both to G2-dendr-meso-SiO2-Pd and G3-
dendr-SiO2-Pd in its efficiency. At the same time it was the only
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weight Mn of 5800 HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H
(Pluronic P123, Aldrich); microporous G3-dendr-SiO2 and mesopo-
rous G2-dendr-meso-SiO2 carriers, synthesized earlier according to
the published procedure.[46]
that was further evaporated on a rotary evaporator, giving an
insoluble residue, weighing 3.3 g.
1
2
3
4
5
6
7
8
9
For the next stage of the synthesis, 2.5 g of Pluronic P123 were
placed into a 100 mL glass beaker, containing a solution of 90 mL
of deionized water and 0.55 mL of concentrated hydrochloric acid
(Sigma-Tech, Chemical Grade). The mixture obtained was subjected
Analyses and Instrumentations
°
to stirring at 50 C for 3 h, gradually growing turbid. After that the
Analysis by transmission electron microscopy (TEM) was conducted
using a LEO912 AB OMEGA microscope with electron tube voltage
of 100 kV. The count of particles and calculation of mean particle
size was performed by processing the obtained micro-images using
the “Image J” program. High resolution transmission electron
microscopy (HRTEM) was performed using a JEM-2100 microscope
with an electron tube voltage of 200 kV (LaB6 cathode). The d-
spacing of the metal nanoparticles was made by means of fast
Fourier transforms of the micrographs obtained, using the “Image
J” program.
previously obtained and ground modified dendrimer was added to
the resultant colloid solution of polymer, followed by stirring for
°
3 h. at 50 C, resulting in red-orange residue. This residue was
further stored in a drying chamber for 3 h with a gradual temper-
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25
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29
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32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
°
ature increase from 60 to 110 C, and after that it was subjected to
°
stirring with 25 mL of water and 100 mL of ethanol at 70 C, to
wash out the polymer. Then the residue obtained was subjected to
centrifugation and dried in the air. The product was isolated as a
fluffy yellow powder, weighing 3.25 g.
XPS: 285.8 (C 1s, 67.6%); 399.4 (N 1s, 16.1%); 532.7 (O 1s, 16.3%).
X-ray photoelectron spectroscopy (XPS) analysis was carried out on
Kratos Axis Ultra DLD and LAS-3000 instruments equipped with an
OPX-150 hemispherical retarding-field electron-energy analyzer.
The X-radiation of an aluminum anode (Al K=1486.6 eV) was used
for the excitation of photoelectrons at a tube voltage of 12 kV and
an emission current of 20 mA. Photoelectron peaks were calibrated
on the C 1s line of carbon with a binding energy of 284.8 eV.
Deconvolution of palladium peaks was processed with the PeakFit
4.11 program using the Gauss-Lorentz-Ampere approximation.
13C NMR (δ, ppm): 74 (À OCH2CH2OCH2); 68 (À (CH2)2CHOH); 65
(SiCH2CH2CH2O); 53 (NCH2CH2CH2CH2N); 51 (NCH2CH2CH2N,
NHCH2CH2O); 47 (NCH2CH2CH2NHCH2À ); 38 (NCH2CH2CH2NH2); 22
(NCH2CH2CH2N,
(SiCH2CH2CH2O).
NCH2CH2CH2CH2N,
SiCH2CH2CH2O);
9.6
The synthesis of G3-dendr-SiO2-Pd catalyst.[43] Into a 25 mL single
neck round-bottom flask, equipped with magnetic stirrer and reflux
condenser, 500 mg of the microporous hybrid G3-dendr-SiO2 carrier
and 5 mL of chloroform were placed. Then 100 mg (0.45 mmol) of
Pd(OAc)2 in 5 mL of chloroform were added to the resulting
suspension while stirring. The reaction was carried out for 6 h at
The quantitative determination of palladium in the samples was
performed by atomic emission spectrometry with inductively
coupled plasma (ICP AES) by means of IRIS Interpid II XPL
instrument (Thermo Electron Corp., USA) with both radial and axial
viewings at wavelengths of 310 and 95.5 nm.
°
70 C. The color of the reaction mixture changed from red-ocher to
brown-black. After the reaction, the suspension was evaporated in
°
a rotary evaporator at 50 C. The resulting material was a grey-
Analysis by means of nitrogen low-temperature adsorption and
desorption was carried out on a Gemini VII 2390 instrument.
Nitrogen adsorption-desorption isotherms were obtained at 77 K.
brown powder weighing 562 mg (yield of 93.5%).
To reduce Pd (II) to Pd (0), 562 mg of the earlier obtained catalyst
precursor, 7 mL of chloroform and 3 mL of methanol were placed
°
The samples being analyzed were previously outgassed at 150 C
to
a 25 mL single neck round-bottom flask, equipped with
for 12 h. Surface area measurements were performed according to
the Brunauer-Emmett-Teller (BET) method from nitrogen adsorption
points in the range P/P0 =0.05–0.2. Pore size distribution was
calculated using the Barrett-Joyner-Halenda model (BJH). The
diameter corresponding to the maximum of the pore size
distribution curve was suggested as the average pore size. Total
pore volume was obtained at a relative pressure P/P0 of 0.985.
magnetic stirrer and reflux condenser. Then 171 mg (4.5 mmol) of
sodium borohydride were portion-wise added to the suspension
obtained while stirring. The reaction mixture rapidly turned black
and gas evolution was observed. The reaction was carried out for
°
6 h at 70 C. After the reaction, the resulting solid mixture was
washed with water and methanol to remove sodium tetraborate,
and the residue isolated by centrifugation and dried in the air. The
resulting material was a black powder weighing 494 mg (yield of
90%).
A
ChromPack CP9001 gas chromatograph, equipped with a
capillary column (SE-30 grafted phase, 30 m×0.2 mm) and flame-
ionization detector, was used for analysis of substrates and reaction
products. Chromatograms were recorded and analyzed on a
computer with the use of the Maestro 1.4 software. Conversion was
determined by changes in the relative peak areas (in %) of the
substrates and products.
XPS (eV): 102.9 (SiO2, Si 2p, 15.9%); 283.6 (OCH2CH2CH2Si, C 1s,
3.8%), 284.7 (NCH2CH2CH2N, NCH2CH2CH2CH2N, OCH2CH2CH2Si, C
1s, 6.2%), 286.4 (NCH2CH2CH2N, OCH2CH2CH2Si, OCH2CH2O/N, C
1s, 14.6%), 288.2 (À OÀ CÀ OÀ , À CH2CH2O!PdOx, C 1s, 2.9%),
289.4 (orthoester, epoxide or NCH2CH2CH2N/OCH2CH2O (sat), C
1s, 0.9%); 335.8 (Pd0, Pd 3d5/2, 1.7%), 337.4 (PdO, Pd 3d5/2, 1.3%),
338.7 (Pd (II) N-bound, Pd 3d5/2, 0.1%), 341.6 (Pd0, Pd 3d3/2), 343.2
(PdO, Pd 3d3/2), 344.4 (Pd (II) N-bound, Pd 3d3/2); 398.7
(NCH2CH2CH2N, NCH2CH2CH2NH2, N 1s, 0.7%), 399.9 (CH2NH2!
Pd0, À CH2NH2!Pdδ +, N 1s, 1.5%), 401.1 (NH3R+, À CH=NH+À , N
1s, 1.3%), 402.5 (NHR3 +, R3N+ !OÀ , N 1s, 0.5%), 404.4 (R3N+ !
OÀ , N 1s, 0.05%), 405.8 (N 1s (sat), 0.1%); 531.1 (PdOx, O 1s,
3.9%), 532.8 (OCH2CH2O, SiO2, O 1s, 17.7%), 534.4 (SiO2, À CH2O!
Pdδ +, N/O…H2O, O 1s, 15.4%), 536.0 (ordered H2O, O 1s, 9.1%),
537.8 (O 1s (sat), 2.4%).
Synthetic Procedures for Porous Hybrid Dendrimer-Based
Materials
The synthesis of meso-G2-dendr-Si network.[78] The synthesis of
mesoporous dendrimer-based material was performed according to
the following procedure Into a 25 mL single-neck round-bottom
flask, equipped with a magnetic stirrer and a reflux condenser,
1.33 g (1.7 mmol) of DAB(NH2)8 dendrimer and 5 mL of ethanol
were placed. Then 1.52 mL (6.9 mmol) of (3-glycidoxypropyl)
triethoxysilane were added dropwise at room temperature, while
13C NMR (δ, ppm): 73 (À OCH2CH2OCH2À ); 66 (À (CH2)2CHOH); 57
°
stirring. Reaction was carried out at 80 C for 2 h while stirring and
(NCH2CH2CH2CH2N);
51
(NCH2CH2CH2N,
NHCH2CH2O);
46
the flask contents gradually turned into an orange glass-like mass,
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(NCH2CH2CH2NHCH2À ); 33 (NCH2CH2CH2NH2); 23 (NCH2CH2CH2N,
NCH2CH2CH2CH2N); 16 (SiCH2CH2CH2O); 9.6 (SiCH2CH2CH2O).
added with a concentration of 2 μL of the solvent per 1 mg of the
substrate. The autoclave was tightly closed, filled with hydrogen to
a required pressure, and connected to a thermostat. The reaction
1
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3
4
5
6
7
8
9
ICP-AES: 6.70% wt. of Pd.
°
was carried out at 80 C with intense stirring for a required time,
The synthesis of G2-dendr-meso-SiO2-Pd catalyst.[43] The synthesis was
performed similar to the previously described procedure. 1000 mg
of mesoporous hybrid G2-dendr-meso-SiO2 carrier and 215 mg
(0.96 mmol) of Pd(OAc)2 in 15 mL of chloroform were taken as
after which the reactor was cooled below room temperature. The
reaction products were analyzed by means of gas-liquid chroma-
tography.
Activity of the catalysts (TOF=turnover frequency) was calculated
as the amount of reacted substrate (νsubstr) per mole of metal (νPd)
per unit of time:
°
initial substances. The reaction was carried out for 12 h at 70 C. To
reduce Pd (II) to Pd (0), the resulting intermediate product
(847 mg), isolated as yellow-brown powder, was introduced into
reaction with 365 mg (9.6 mmol) of sodium borohydride in a
mixture of 10 mL of chloroform and 5 mL of ethanol. The weight of
the end product, isolated as a black powder, was 926 mg (71%).
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51
nsubstr � w
TOF ¼
nPd � t
XPS (eV): 103.1 (SiO2, Si 2p, 13.1%), 153.5 (SiO2, Si 2 s); 284.8
(NCH2CH2CH2N, NCH2CH2CH2CH2N, OCH2CH2CH2Si, C 1s, 13.6%),
286.3 (NCH2CH2CH2N, OCH2CH2CH2Si, OCH2CH2O/N, C 1s, 15.1%),
288.0 (À OÀ CÀ OÀ , À CH2CH2O!PdOx, C 1s, 3.4%); 335.2 (Pd0, Pd
3d5/2, 1.70%), 336.5 (PdOx/Pd, Pd 3d5/2, 0.5%), 338.0 (Pd2+, PdOx, Pd
3d5/2, 0.4%), 339.0 (Pd (II) N-bound, Pd 3d5/2, 0.1%), 340.5 (Pd0, Pd
3d3/2), 341.6 (PdOx/Pd, Pd 3d3/2), 343.1 (Pd2+, PdOx, Pd 3d3/2), 344.2
(Pd (II) N-bound, Pd 3d3/2), 345.7 (Pd2+, Pd 3d3/2 sat); 397.6
where ω is substrate conversion, expressed in the unit fractions.
Herein t is the minimal reaction time, for which the reaction
progress is measured.
The re-use of dendrimer-based Pd hybrid catalysts was conducted
as follows. The desired amounts of catalysts and substrate were
placed in a thermostatically controlled steel autoclave equipped
with a glass insertion tube and a magnetic stirrer. The autoclave
was tightly closed and filled with hydrogen up to a pressure of 10
or 30 atm. and then connected to the thermostat. The reaction was
(À C=NÀ CÀ , À N�Pdads
,
N
1s, 0.2%), 399.9 (NCH2CH2CH2N,
OCH2CH2NHCH2À , (À CH2NH2!Pd0, À CH2NH2!Pdδ+, N 1s, 2.9%),
402.0 (NHR3+, [À CH=NHÀ ]+, N 1s, 0.5%); 532.8 (OCH2CH2O, SiO2, O
1s, 48.2%).
°
carried out at 80 C with intense stirring for 15 min. After the
reaction completed, the stirring was turned off and the autoclave
was cooled below room temperature in a cold water bath and
opened. The reaction mixture was diluted with ~2 mL of hexane for
the better sedimentation of the catalyst and allowed to stand for
20–30 min. The solution with reaction products was separated by
decantation and analyzed by gas-liquid chromatography. Catalyst,
remained in the test tube, was repeatedly used without additional
loading or purification.
13C NMR (δ, ppm): 75 (À OCH2CH2OCH2); 57 (NCH2CH2CH2N,
NCH2CH2CH2CH2N, NHCH2CH2O, br); 51 (NCH2CH2CH2NHCH2-, br); 33
(NCH2CH2CH2NH2, br); 25 (NCH2CH2CH2N, NCH2CH2CH2CH2N); 15
(SiCH2CH2CH2O); 8 (SiCH2CH2CH2O).
ICP-AES: 7.58% wt. of Pd.
The synthesis of meso-G2-dendr-Si-Pd catalyst.[43] The synthesis was
carried out using a previously described procedure. 500 mg of
meso-G2-dendr-Si network and 262 mg (1.17 mmol) of Pd(OAc)2 in
15 mL of chloroform were taken as initial substances. The reaction
Acknowledgements
°
was carried out for 6 h at 70 C. To reduce Pd (II) to Pd (0), the
resulting intermediate product (500 mg), isolated as dark-brown
powder, was introduced into reaction with 443 mg (11.66 mmol) of
sodium borohydride in a mixture of 10 mL of chloroform and 5 mL
of ethanol. The weight of the end product, isolated as a black
powder, was 430 mg (69%).
This work was supported by RFBR grant No 16–33-60101. We also
thank Natalia Tabachkova (National University of Science and
Technology ‘MISIS’, Moscow, Russia) for HRTEM facilities.
XPS (eV): 284.3 (NCH2CH2CH2N, NCH2CH2CH2CH2N, OCH2CH2CH2Si,
OCH2CH2CH2Si, C 1s, 13.6%), 286.3 (NCH2CH2CH2N, OCH2CH2CH2Si,
OCH2CH2O/N, C 1s, 32.4%), 288.2 (À OÀ CÀ OÀ , À CH2CH2O!PdOx, C
1s, 11.0%), 290.1 (À C(OCH2À )3 or NCH2CH2CH2N/OCH2CH2O (sat), C
Conflict of Interest
The authors declare no conflict of interest.
1s, 5.4%); 335.3 (Pd0, Pd 3d5/2, 0.6%), 336.6 (PdOx/Pd, Pd 3d5/2
,
1.0%), 337.8 (Pd2+, PdOx, Pd 3d5/2, 0.7%), 340.6 (Pd0, Pd 3d3/2), 341.6
(PdOx/Pd, Pd 3d3/2), 342.6 (Pd2+, PdOx, Pd 3d3/2); 398.0 (À C=NÀ CÀ ,
À N�Pdads, N 1s, 2.2%), 399.3 (NCH2CH2CH2N, OCH2CH2NHCH2À , N 1s,
11.2%), 400.4 (À CH2NH2!Pd0, À CH2NH2!Pdδ+, N 1s, 3.2%), 401.4
(NH3R+, À CH=NH+À , N 1s, 0.4%), 403.8 (R3N+!OÀ , N 1s, 1.2%),
405.0 (N 1s (sat), 0.4%); 530.1 (O 1s, PdOx/Pd, 0.9%), 531.2 (PdOx, O
1s, 1.4%), 532.5 (OCH2CH2O, SiO2, O 1s, 12.2%), 533.7 (SiO2,
À CH2O!Pdδ+, 1 s, 1.4%), 534.7(N/O…H2O, O 1s, 0.7%).
Keywords: palladium nanoparticles · hydrogenation · organic-
inorganic hybrid composites · immobilized dendrimers
[1] a) D. Astruc, F. Lu, J. Ruiz Aranzaes, Angew. Chem. Int. Ed. 2005, 44,
7852–7872, b) A.Yu. Stakheev, I. S. Mashkovskii, G. N. Baeva, N. S. Tele-
gina, Russ. J. Gen. Chem. 2010, 80, 618–629; c) C. D. Pina, E. Falletta, M.
Rossi, Chem. Soc. Rev. 2012, 41, 350–369; d) I. Favier, E. Teuma, M.
Gómez, C. R. Chim. 2009, 12, 533–545; e) H. Hagiwara, T. Nakamura, N.
Okunaka, T. Hoshi, T. Suzuki, Helv. Chim. Acta 2010, 93, 175–182; f) E. A.
Karakhanov, A. L. Maksimov, A. V. Zolotukhina, Yu. S. Kardasheva, Russ.
Chem. Bull. 2013, 62, 1465–1492; g) J. A. Widegren, R. G. Finke, J. Mol.
Catal. A 2003, 191, 187–207; h) V. Polshettiwar, Á. Molnár, Tetrahedron
2007, 63, 6949–6976.
[2] a) J. M. Thomas, B. F. G. Johnson, R. Raja, G. Sankar, P. A. Midgley, Acc.
Chem. Res. 2003, 26, 20–30; b) B. F. G. Johnson, S. A. Raynor, D. B. Brown,
D. S. Shephard, T. Mashmeyer, J. M. Thomas, S. Hermans, R. Raja, G.
Sankar, J. Mol. Catal. A: Chem. 2002, 182–183, 89–97; c) J.-L. Liu, L.-J.
ICP-AES: 7.71% wt. of Pd.
52 Protocol for the Catalytic Experiments
53
54
55
56
57
A catalyst and a substrate in a required ratio were placed into a
thermostatically controlled steel autoclave, equipped with an glass
insertion tube and a magnetic stirrer. If the solid substrate was
used (4-phenylstyrene, trans-stilbene), a toluene as a solvent was
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www.chemistryopen.org
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© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA

Full Papers
Zhu, Ya. Pei, J.-H. Zhuang, H. Li, H.-X. Li, M.-H. Qiao, K.-N. Fan, Appl.
Catal. A. 2009, 353, 282–287; d) Sh. Miao, Zh. Liu, B. Han, J. Huang, Zh.
Sun, J. Zhang, T. Jiang, Angew. Chem. Int. Ed. 2006, 45, 266–269; e) J.-L.
Liu, L.-J.n Zhu, Ya. Pei, J.-H. Zhuang, H. Li, H.-X. Li, M.-H. Qiao, K.-N. Fan,
Appl. Catal. A 2009, 353, 282–287; f) M. Jacquin, D. J. Jones, J. Rozière, S.
Albertazzi, A. Vaccari, M. Lenarda, L. Storaro, R. Ganzerla, Appl. Catal. A
2003, 251, 131–141; g) Á. Mastalir, Z. Király, F. Berger, Appl. Catal. A
2004, 269, 161–168; h) A. Papp, Á. Molnár, Á. Mastalir, Appl. Catal. A.
2005, 289, 256–266; i) J. D. Webb, S. MacQuarrie, K. McEleney, C. M.
Crudden, J. Catal. 2007, 252, 97–109; j) G. Budroni, A. Corma, H. García,
A. Primo, J. Catal. 2007, 251, 345–353; k) D. D. Das, A. Sayari, J. Catal.
2007, 246, 60–65; l) N. Ren, Y.-H. Yang, Y.-H. Zhang, Q.-R. Wang, Y. Tang,
J. Catal. 2007, 246, 215–222; m) Yu. Nie, S. Jaenicke, H. van Bekkum, G.-
Kh. Chuah, J. Catal. 2007, 246, 223–231.
D. Zhao, W. H. Ang, Yo. Li, P. J. Dyson, Inorg. Chem. 2008, 47, 3292–
3297; h) V. Calò, A. Nacci, A. Monopoli, F. Montingelli, J. Org. Chem.
2005, 70, 6040–6044; i) M. H. G. Prechtl, M. Scariot, J. D. Scholten, G.
Machado, S. R. Teixeira, J. Dupont, Inorg. Chem. 2008, 47, 8995–9001.
[10] a) M. Guerrero, A. Roucoux, A. Denicourt-Nowicki, H. Bricoute, E.
Monflier, V. Collière, K. Fajerwerg, K. Philippot, Catal. Today 2012, 183,
34–41; b) D. González-Gálvez, P. Nolis, K. Philippot, B. Chaudret,
P. W. N. M. van Leeuwen, ACS Catal. 2012, 2, 317–321; c) A. Gual, M. R.
Axet, K. Philippot, B. Chaudret, A. D. Nowicky, A. Roucoux, S. Castillon, C.
Claver, Chem. Commun. 2008, 2759–2761; d) E. Bresó-Femenia, B.
Chaudret, Sergio Castillón, Catal. Sci. Technol. 2015, 5, 2741–2751; e) R.
Liu, F. Zhao, Sh. Fujita, M. Arai, Appl. Catal. A. Gen. 2007, 316, 127–133;
f) J. O. Woo, J.-E. Park, J.-S. Han, T. S. Kwon, Ye.-J. Kim, K.-S. Son, Appl.
Organometal. Chem. 2014, 28, 151–155; g) R. Tatumi, T. Akita, H.
Fujihara, Chem. Commun. 2006, 3349–3351.
[11] a) E. Bayer, W. Schumann, J. Chem. Soc., Chem. Commun. 1986, 12, 949–
952; b) F. Lu, J. Liu, J. Xu, Mater. Chem. Phys. 2008, 108, 369–374; c) F.
Lu, J. Liu, J. Xu, J. Mol. Catal. A. Chem. 2007, 271, 6–13; d) J.-F. Zhu, G.-H.
Tao, H.-Yu Liu, L. He, Q.-H. Sun, H.-Ch. Liu, Green Chem. 2014, 16, 2664–
2669; e) M. M. Telkar, C. V. Rod, R. V. Chaudhari, S. S. Joshi, A. M.
Nalawade, Appl. Catal. A: Gen. 2004, 273, 11–19; f) F. Lu, J. Liu, J. Xu, Adv.
Synth. Catal. 2006, 348, 857–861.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
[3] a) R. Soeiro Suppino, R. Landers, A. J. Gomez Cobo, Appl. Catal. A 2013,
452, 9–16; b) L. Piccolo, A. Valcarcel, M. Bausach, C. Thomazeau, D. Uzio,
G. Berhault, Phys. Chem. Chem. Phys. 2008, 10, 5504–5506; c) P. V.
Markov, O. V. Turova, I. S. Mashkovsky, A. K. Khudorozhkov, V. I.
Bukhtiyarov, A.Yu. Stakheev, Mendeleev Commun. 2015, 25, 367–369;
d) S. Domínguez-Domínguez, Á. Berenguer-Murcia, Á. Linares-Solano, D.
Cazorla-Amorós, J. Catal. 2008, 257, 87–95; e) H. Liu, T. Jiang, B. Han, Sh.
Liang, Yi. Zhou, Science 2009, 326, 1250–1252; f) Y. Pérez, M. Fajardo, A.
Corma, Catal. Commun. 2011, 12, 1071–1074; g) A. Solladié-Cavallo, A.
Baram, E. Choucair, H. Norouzi-Arasi, M. Schmitt, F. Garin, J. Mol. Catal. A
2007, 273, 92–98.
[12] a) S. Sawoo, D. Srimani, P. Dutta, R. Lahiri, A. Sarkar, Tetrahedron 2009,
65, 4367–4374; b) D. Srimani, S. Sawoo, A. Sarkar, Org. Lett. 2007, 9,
3639–3642.
[13] Sh. Mori, T. Ohkubo, T. Ikawa, A. Kume, T. Maegawa, Ya. Monguchi, H.
Sajiki, J. Mol. Catal. A: Chem. 2009, 307, 77–87
[4] a) F. Su, L. Lv, F. Y. Lee, T. Liu, A. I. Cooper, X. S. Zhao, J. Am. Chem. Soc.
2007, 129, 14213–14223; b) Yi. Wan, H. Wang, Q. Zhao, M. Klingstedt, O.
Terasaki, D. Zhao, J. Am. Chem. Soc. 2009, 131, 4541–4550.
[14] V. Huc, K. Pelzer, J. Colloid Interface Sci. 2008, 318, 1–4.
[5] a) T. Maegawa, A. Akashi, K. Yaguchi, Yo. Iwasaki, M. Shigetsura, Ya.
Monguchi, H. Sajiki, Chem. Eur. J. 2009, 15, 6953–6963; b) B. Güvenatam,
O. Kurşun, E. H. J. Heeres, E. A. Pidko, E. J. M. Hensen, Catal. Today, 2014,
233, 83–91; c) K. H. Park, K. Jang, H. J. Kim, S. U. Son, Angew. Chem. Int.
Ed. 2007, 46, 1152–1155; d) Z. A. Chase, J. L. Fulton, D. M. Camaioni, D.
Mei, M. Balasubramanian, V.-T. Pham, Ch. Zhao, R. S. Weber, Yo. Wang,
J. A. Lercher, J. Phys. Chem. C 2013, 117, 17603–17612; e) N. Hiyoshi, Ch.
Rode, O. Sato, H. Tetsuka, M. Shirai, J. Catal. 2007, 252, 57–68; f) Á.
Mastalir, Z. Király, Á. Patzkó, I. Dékány, P. L’Argentiere, Carbon 2008, 46,
1631–1637; g) P. Handa, K. Wikander, K. Holmberg, Microporous
Mesoporous Mater. 2009, 117, 126–135.
[6] a) H. Wang, F. Zhao, S. Fujita, M. Arai, Catal. Commun. 2008, 9, 362–368;
b) S. Domínguez-Domínguez, Á. Berenguer-Murcia, B. K. Pradhan, Á.
Linares-Solano, Diego Cazorla-Amorós, J. Phys. Chem. C 2008, 112,
3827–3834; c) E. A. Karakhanov, I. A. Aksenov, S. V. Kardashev, A. L.
Maksimov, F. N. Putilin, A. N. Shatokhin, S. V. Savilov, Appl. Catal. A: Gen.
2013, 464–465, 253–260; d) Y. Wang, J. Yao, H. Li, D. Su, M. Antonietti, J.
Am. Chem. Soc. 2011, 133, 2362–2365; e) Y. Ma, Ya. Huang, Yo. Cheng, L.
Wang, X. Li, Appl. Catal. A. Gen. 2014, 484, 154–160; f) L. Li, Hu. Zhao, R.
Wang, ACS Catal. 2015, 5, 948–955; g) M. Pilar Ruiz, J. Faria, M. Shen, S.
Drexler, T. Prasomsri, D. E. Resasco, ChemSusChem 2011, 4, 964–974;
h) E. V. Starodubtseva, M. G. Vinogradov, O. V. Turova, N. A. Bumagin,
E. G. Rakov, V. I. Sokolov, Catal. Commun. 2009, 10, 1441–1442; i) N.
Semagina, A. Renken, L. Kiwi-Minsker, Chem. Eng. Sci. 2007, 62, 5344–
5348.
[7] a) A. Maximov, A. Zolotukhina, L. Kulikov, Yu. Kardasheva, E. Karakhanov,
React. Kinet. Mech. Cat. 2016, 117, 1–15; b) E. Karakhanov, Yu.
Kardasheva, L. Kulikov, A. Maximov, A. Zolotukhina, M. Vinnikova, A.
Ivanov, Catalysts 2016, 6, 122, doi:10.3390/catal6080122.
[8] a) D. Gonzalez-Galvez, P. Lara, O. Rivada-Wheelaghan, S. Conejero, B.
Chaudret, K. Philippot, P. W. N. M. van Leeuwen, Catal. Sci. Technol.
2013, 3, 99–105; b) P. Lara, K. Philippot, B. Chaudret, ChemCatChem
2013, 5, 28–45; c) K. Nasar, F. Fache, M. Lemaire, J.-C. Béziat, M. Besson,
P. Gallezot, J. Mol. Catal. 1994, 87, 107–115; d) S. Jansat, D. Picurelli, K.
Pelzer, K. Philippot, M. Gómez, G. Muller, P. Lecante, B. Chaudret, New J.
Chem. 2006, 30, 115–122; e) A. Gual, C. Godard, S. Castillon, Carmen
Claver, Dalton Trans. 2010, 39, 11499–11512;
[15] a) A. Nowicky, Y. Zhang, B. Léger, J.-P. Rolland, H. Bricout, E. Monflier, A.
Roucoux, Chem. Commun. 2006, 296–298; b) S. Kuklin, A. Maximov, A.
Zolotukhina, E. Karakhanov, Catal. Commun. 2016, 73, 63–68; c) S. Noël,
B. Léger, R. Herbois, A. Ponchel, S. Tilloy, G. Wenz, E. Monflier, Dalton
Trans. 2012, 41, 13359–13363; d) S. Noël, B. Léger, A. Ponchel, K.
Philippot, A. Denicourt-Nowicki, A. Roucoux, E. Monflier, Catal. Today
2014, 235, 20–32.
[16] a) R. Andrés, E. Jesús, J. C. Flores, New J. Chem. 2007, 31, 1161–1191;
b) D. Astruc, E. Boisselier, C. Ornelas, Chem. Rev. 2010, 110, 1857–1959;
c) D. Mery, D. Astruc, Coord. Chem. Rev. 2006, 250, 1965–1979; d) D.
Wang, D. Astruc, Coord. Chem. Rev. 2013, 257, 2317–2334.
[17] a) F. Vögtle, S. Gestermann, R. Hesse, H. Schwierz, B. Windisch, Prog.
Polym. Sci. 2000, 25, 987–1041; b) R. M. Crooks, M. Zhao, L. Sun, V.
Chechik, L. K. Yeung, Acc. Chem. Res. 2001, 34, 181–190; c) Y. Niu, R. M.
Crooks, C. R. Chimie 2003, 6, 1049–1059; d) G. R. Newkome, C. D.
Shreiner, Polym. 2008, 49, 1–173.
[18] a) M. Ooe, M. Murata, T. Mizugaki, T. Ebitani, K. Kaneda, Nanolett. 2002,
2, 999–1002; b) M. Murata, Yu. Tanaka, T. Mizugaki, K. Ebitani, K. Kaneda,
Chem. Lett. 2005, 34, 272–273.
[19] a) K. R. Gopidas, J. K. Whitesell, M. A. Fox, Nano Lett. 2003, 3, 1757–1760;
b) M. Ooe, M. Murata, T. Mizugaki, K. Ebitani, K. Kaneda, J. Am. Chem.
Soc. 2004, 126, 1604–1605; c) Ya. Yang, Sh. Ogasawara, G. Li, Sh. Kato,
Polym. J. 2015, 47, 1–8; d) E. A. Karakhanov, A. L. Maximov, B. N.
Tarasevich, V. A. Skorkin, J. Mol. Catal. A: Chem. 2009, 297, 73–79; e) A.
Singh, B. D. Chandler, Langmuir 2003, 19, 7682–7684; f) Q.-H. Fan, Y.-M.
Chen, X.-M. Chen, D.-Zh. Jiang, F. Xi, A. S. C. Chan, Chem. Commun.
2000, 789–790; g) G.-J. Deng, Q.-H. Fan, X.-M. Chen, D.-Sh. Liu, A. S. C.
Chan, Chem. Commun. 2002, 1570–1571.
[20] a) M. Antonietti, E. Wenz, L. Bronstein, M. Seregina, Adv. Mater. 1995, 7,
1000–1005; b) J. P. Spatz, A. Roescher, M. Möller, Adv. Mater. 1996, 8,
337–340.
[21] C. Ornelas, J. Ruiz, L. Salmon, D. Astruc, Chem. Eur. J. 2008, 14, 50–64.
[22] L. M. Bronstein, Z. B. Shifrina , Chem. Rev. 2011, 111, 5301–5344.
[23] a) K. Esumi, A. Suzuki, N. Aihara, K. Usui, K. Torigoe, Langmuir 1998, 14,
3157–3159; b) M. E. Garcia, L. A. Baker, R. M. Crooks, Anal. Chem. 1999,
71, 256–258.
[24] a) S. Chandra, H. Lang, Mater. Chem. Phys. 2009, 114, 926–932; b) C. Li,
D. Li, Z.-S. Zhao, X.-M. Duan, W. Hou, Colloid. Surf. A: Physicochem. Eng.
Asp. 2010, 366, 45–49.
[25] a) J. R. Lakowicz, I. Gryczynski, Z. Gryczynski, C. J. J. Murphy, Phys. Chem.
B 1999, 103, 7613–7620; b) X. Y. Shi, T. R. Ganser, K. Sun, L. P. Balogh,
J. R. Baker Jr., Nanotechnol. 2006, 17, 1072–1078.
[26] Y. Niu, L. K. Yeung, R. M. Crooks, J. Am. Chem. Soc. 2001, 123, 6840–6846
[27] A. C. Wisher, I. Bronstein, V. Chechik, Chem. Commun. 2006, 1637–1639
[28] K. Sooklal, L. H. Hanus, H. J. Ploehn, C. J. Murphy, Adv. Mater. 1998, 10,
1083–1087
[9] a) J. Le Bras, D. Kumar Mukherjee, S. González, M. Tristany, B. Ganchegui,
M. Moreno-Mañas, R. Pleixats, F. Hénin, J. Muzart, New J. Chem. 2004,
28, 1550–1553; b) A. Nowicki, V. Le Boulaire, A. Roucoux, Adv. Synth.
Catal. 2007, 349, 2326–2330; c) E. T. Silveira, A. P. Umpierre, L. M. Rossi,
G. Machado, J. Morais, G. V. Soares, I. J. R. Baumvol, S. R. Teixeira, P. F. P.
Fichtner, J. Dupont, Chem. Eur. J. 2004, 10, 3734–3740; d) L. M. Rossi, G.
Machado, J. Mol. Catal. A: Chem. 2009, 298, 69–73; e) A. L. Maksimov,
S. N. Kuklin, Yu.S. Kardasheva, E. A. Karakhanov, Petrol. Chem. 2013, 53,
157–163; f) M. Beller, H. Fischer, K. Kühlein, C.-P. Reisinger, W. A.
Herrmann, J.Organomet. Chem. 1996, 520, 257–259; g) X. Yang, Zh. Fei,
ChemistryOpen 2019, 8, 358–381
www.chemistryopen.org
379
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA

Full Papers
[29] a) F. Gröhn, B. J. Bauer, Y. A. Akpalu, C. L. Jackson, E. J. Amis, Macromol.
2000, 33, 6042–6050; b) E. Boisselier, A. K. Diallo, L. Salmon, C. Ornelas,
J. Ruiz, D. Astruc, J. Am. Chem. Soc. 2010, 132, 2729–2742; c) A. K. Diallo,
C. Ornelas, L. Salmon, J. Ruiz, D. Astruc, Angew. Chem. Int. Ed. 2007, 46,
8644–8648; d) C. Ornelas, L. Salmon, J. Ruiz, D. Astruc, Chem. Commun.
2007, 4946–4948; e) C. Ornelas, J. Ruiz, L. Salmon, D. Astruc, Adv. Synth.
Catal. 2008, 350, 837–845.
[30] E. A. Karakhanov, A. L. Maximov, V. A. Skorkin, A. V. Zolotukhina, A. S.
Smerdov, A.Yu. Tereshchenko, Pure Appl. Chem. 2009, 81, 2013–2023
[31] a) A. Maximov, A. Zolotukhina, V. Murzin, E. Karakhanov, E. Rosenberg,
ChemCatChem 2015, 7, 1197–1210; b) E. A. Karakhanov, A. L. Maximov,
A. V. Zolotukhina, M. V. Terenina, A. V. Vutolkina, Petrol. Chem. 2016, 56,
491–502; c) E. Karakhanov, A. Maximov, A. Zolotukhina, Yu. Kardasheva,
M. Talanova, J. Inorg. Organomet. Polym. Mater. 2016, 26, 1264–1279;
d) E. M. Zakharyan, Gouqiung Ma, A. L. Maksimov, E. A. Karakhanov,
Z. D. Voronina, Petrol. Chem. 2014, 54, 412–419.
[51] B. González, M. Colilla, C. López de Laorden, M. Vallet-Regí, J. Mater.
Chem. 2009, 19, 9012–9024
[52] a) J. R. Anderson, Structure of Metallic Catalysts, London, Academic Press,
1975; b) P. C. Aben, J. Catal. 1968, 10, 224–229
1
2
3
4
5
6
7
8
9
[53] a) V. I. Nefedov, I. A. Zakharova, I. I. Moiseev, M. A. Porai-koshits, M. N.
Vargoftik, A. P. Belov, Zh. Neorg. Khimii 1973, 18, 3264 (Russ. J. Inorg.
Chem. 1973, 18, 3264); b) V. I. Nefedov, Y. V. Salyn, I. I. Moiseev, A. P.
Sadovskii, A. S. Berenbljum, A. G. Knizhnik, S. L. Mund, Inorg. Chim. Acta
1979, 35, L343–L344; c) C. J. Powell, J. Electron Spectrosc. Relat. Phenom.
2012, 185, 1–3; d) R. Nyholm, N. Mårtensson, J. Phys. C 1980, 13, L279–
L284.
[54] a) M. C. Militello, S. J. Simko, Surf. Sci. Spectra 1994, 3, 395–401; b) G. A.
Shafeev, J.-M. Themlin, L. Bellard, W. Marine, A. Cros, J. Vac. Sci. Technol.
A 1996, 14, 319–326; c) K. Noack, H. Zbinden, R. Schlögl, Catal. Lett.
1990, 4, 145–155; d) T. H. Fleisch, G. W. Zaiac, J. O. Schreiner, G. J. Mains,
Appl. Surf. Sci. 1986, 26, 488–497
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
[32] a) E. A. Karakhanov, A. L. Maximov, E. M. Zakharyan, A. V. Zolotukhina,
A. O. Ivanov, Mol. Catal. 2017, 440, 107–119; b) E. A. Karakhanov, A. L.
Maksimov, A. V. Zolotukhina, S. V. Kardashev, T.Yu. Filippova, Petrol.
Chem. 2012, 52, 289–298; c) E. A. Karakhanov, A. L. Maksimov, E. M.
Zakharian, Yu.S. Kardasheva, S. V. Savilov, N. I. Truhmanova, A. O. Ivanov,
V. A. Vinokurov, J. Mol. Catal. A: Chem. 2015, 397, 1–18.
[33] a) S. Ogasawara, S. Kato, J. Am. Chem. Soc. 2010, 132, 4608–4613;
b) M. T. Reetz, D. Giebel, Angew. Chem. Int. Ed. 2000, 39, 2948–2951
[34] a) Yi. Jiang, Q. Gao, J. Am. Chem. Soc. 2006, 128, 716–717; b) P. P. Zweni,
H. Alper, Adv. Synth. Catal. 2006, 348, 725–731; c) H. Wu, Z. Liu, X. Wang,
B. Zhao, J. Zhang, C. Li, J. Colloid Interface Sci. 2006, 302, 142–148;
d) Y. M. Chung, H. K. Rhee, Korean J. Chem. Eng. 2004, 21, 81–97; e) H. Li,
J. Lü, Zh. Zheng, R. Cao, J. Colloid Interface Sci. 2011, 353, 149–155; f) Yi.
Xu, Zh. Zhang, J. Zheng, Q. Du, Yi. Li, Appl. Organometal. Chem. 2013,
27, 13–18; g) Zh. Zheng, H. Li, T. Liu, R. Cao, J. Catal. 2010, 270, 268–274;
[35] a) G. R. Krishnan, K. Sreekumar, Soft Mater. 2010, 8, 114–129;
b) B. M. J. M. Suijkerbuijk, L. J. Shu, R. J. M. Klein Gebbink, A. D. Schlüter,
G. van Koten, Organometallics, 2003, 22, 4175–4177; c) A. Dahan, M.
Portnoy, Org. Lett. 2003, 5, 1197–1200;
[55] Z. Yi Xiao, Yu. Zhao, A. Wang, J. Perumal, D.-P. Ki, Lab. Chip 2011, 11,
57–62
[56] a) Ya. Masahiro, M. Ichiro, I. Tasuku, W. Yoshiki, M. Tadaoki, I. Isao, Bull.
Chem. Soc. Jpn. 1985, 58, 2336–2339; b) Ya. Masahiro, M. Ichiro, I. Isao,
Bull. Chem. Soc. Jpn. 1985, 58, 2697–2698
[57] a) S. Hub, L. Hilaire, R. Touroude, Appl. Catal. 1988, 36, 307–322; b) Yu.A.
Ryndin, L. V. Nosova, A. I. Boronin, A. L. Chuvilin, Appl. Catal. 1988, 42,
131–141; c) L. V. Nosova, M. V. Stenin, Yu.N. Nogin, Yu.A. Ryndin, Appl.
Surf. Sci. 1992, 55, 43–48; d) M. G. Mason, L. J. Gerenser, S. -T. Lee, Phys.
Rev. Lett. 1977, 39, 288–291; e) Yu. Takasu, R. Unwin, B. Tesche, A. M.
Bradshaw M. Grunze, Surf. Sci. 1978, 77, 219–232; f) A. Fritsch, P. Légaré,
Surf. Sci. 1985, 162, 742–746; g) R. C. Baetzold, J. Catal. 1973, 29, 129–
137
[58] a) M. A. Aramendía, V. Borau, C. Jiménez, J. M. Marinas, M. E. Sempere,
F. J. Urbano, Appl. Catal. 1990, 63, 375–389; b) A. Molnár, A. Sárkány, M.
Varga, J. Mol. Catal. A. Chem. 2001, 173, 185–221
[59] S. Hub, R. Touroude, J. Catal. 1988, 114, 411–421
[60] G. He, Ya. Song, X. Kang, Sh. Chen, Electrochim. Acta 2013, 94, 98–103
[61] J. R. Anderson, Structure of Metallic Catalysts, London, Academic Press,
1975.
[62] N. Semagina, A. Renken, L. Kiwi-Minsker, J. Phys. Chem. C 2007, 111,
13933–13937
[63] a) M. Crespo-Quesada, F. Cardenas-Lizana, A.-L. Dessimoz, L. Kiwi-
Minsker, ACS Catal. 2012, 2, 1773–1786; b) J. P. Boitiaux, J. Cosyns, S.
Vasudevan, Appl. Catal. 1983, 6, 41–51
[64] a) W. G. Augustyn, R. I. McCrindle, N. J. Coville, Appl. Catal. A: Gen. 2010,
388, 1–6; b) C. E. Gigola, H. R. Aduriz, P. Bodnariuk, Appl. Catal. 1986, 27,
133–144; c) J. Silvestre-Albero, G. Rupprechter, H.-J. Freund, Chem.
Commun. 2006, 80–82; d) R. Van Hardeveld, F. Hartog, Surf. Sci. 1969,
15, 189–230; e) D. Uzio, G. Berhault, Catal. Rev. Sci. Eng. 2010, 52, 106–
131.
[65] a) T. Mallat, A. Baiker, Appl. Catal. A. Gen. 2000, 200, 3–22; b) E. M.
Sulman, Russ. Chem. Rev. 1994, 63, 923–936; c) J. P. Boitiaux, J. Cosyns,
S. Vasudevan, Appl. Catal. 1985, 15, 317–326
[66] M. Crespo-Quesada, R. R. Dykeman, G. Laurenczy, P. J. Dyson, L. Kiwi-
Minsker, J. Catal. 2011, 279, 66–74
[67] W. Long, N. A. Brunelli, S. A. Didas, E. W. Ping, C. W Jones, ACS Catal.
2013, 3, 1700–1708
[68] a) G. C. Bond, A. F. Rawle, J. Mol. Catal. A. Chem. 1996, 109, 261–271;
b) G. C. Bond, J. Mol. Catal. A. Chem. 1997, 118, 333–339; c) B. J. Joice,
J. J. Rooney, P. B. Wells, G. R. Wilson, Discuss. Faraday Soc. 1966, 223–
236
[69] G. Carturan, G. Facchin, V. Gottardi, M. Guglielmi, G. Navazio, J. Non-
Cryst. Solids 1982, 48, 219–226
[70] A.Yu. Stakheev, P. V. Markov, A. S. Taranenko, G. O. Bragina, G. N. Baeva,
O. P. Tkachenko, I. S. Mashkovskii, A. S. Kashin, Kinet. Catal. 2015, 56,
733–740
[71] Yo.-M. Chung, H.-K. Rhee, J. Mol. Catal. A. Chem. 2003, 206, 291–298
[72] E. W. Stern, P. K. Maples, J. Catal. 1972, 27, 120–133
[73] a) Z. T. Beisembaeva, B. S. Gudkov, S. L. Kiperman, Bull. Russ. Acad. Sci.
Div. of Chem. Sci. 1984, 33, 481–485; b) Z. T. Beisembaeva, B. S. Gudkov,
M. S. Kharson, N. I. Popov, S. L. Kiperman, Bull. Russ. Acad. Sci. Div. of
Chem. Sci. 1975, 24, 863–865
[74] a) H. Fujii, J. C. Bailar Jr., J. Catal. 1978, 52, 342–345; b) T.-B. Lin, T.-C.
Chou, Appl. Catal. A. Gen. 1994, 108, 7–19; c) D. Duca, L. F. Liotta, G.
Deganello, Catal.Today 1995, 24, 15–21; d) G. Carturan, G. Facchin, G.
Cocco, S. Enzo, G. Navazio, J. Catal. 1982, 76, 405–417; e) G. Carturan, G.
Cocco, G. Facchin, G. Navazio, J. Mol. Catal. 1984, 26, 375–384; f) J. A.
Anderson, J. Mellor, R. P. K. Wells, J. Catal. 2009, 261, 208–216; g) P.
[36] a) J. Alvarez, L. Sun, R. M. Crooks, Chem. Mater. 2002, 14, 3995–4001;
b) Z. Guo, H. Feng, H. C. Ma, Q. X. Kang, Z. W. Yang, Polym. Adv. Technol.
2004, 15, 100–104.
[37] E. Murugan, R. Rangasamy, J. Polym. Sci A: Polym. Chem. 2010, 48, 2525–
2532
[38] a) H. Alper, P. Arya, S. C. Bourque, G. R. Jefferson, L. E. Manzer, Can. J.
Chem. 2000, 78, 920–924; b) R. Chanthateyanonth, H. Alper, J. Mol.
Catal. A: Chem. 2003, 201, 23–31
[39] a) R. Chanthateyanonth, H. Alper, Adv. Synth. Catal. 2004, 346, 1375–
1384; b) Sh.-M. Lu, H. Alper, J. Am. Chem. Soc. 2005, 127, 14776–14784;
c) R. Touzani, H. Alper, J. Mol. Catal. A: Chem. 2005, 227, 197–207; d) Sh.
Antebi, P. Arya, L. E. Manzer, H. Alper, J. Org. Chem. 2002, 67, 6623–
6631; e) J. P. K. Reynhardt, Howard Alper, J. Org. Chem. 2003, 68, 8353–
8360.
[40] P. P. Zweni, H. Alper, Adv. Synth. Catal. 2004, 346, 849–854
[41] H. Hagiwara, H. Sasaki, N. Tsubokawa, T. Hoshi, T. Suzuki, T. Tsuda, S.
Kuwabata, SynLett. 2010, 1990–1996
[42] M. Reza Nabid, Ya. Bide, S. J. Tabatabaei Rezaei, Appl.Catal. A. Gen. 2011,
406, 124–132
[43] E. Karakhanov, A. Maximov, Yu. Kardasheva, V. Semernina, A. Zolotukhi-
na, A. Ivanov, G. Abbott, E. Rosenberg, V. Vinokurov, ACS Appl. Mater.
Interfaces 2014, 6, 8807–8816
[44] E. A. Karakhanov, A. L. Maximov, A. V. Zolotukhina, N. Yatmanova, E.
Rosenberg, Appl. Organomet. Chem. 2015, 29, 777–784
[45] G. Jayamurugan, C. P. Umesh, N. Jayaraman, J. Mol. Catal. A. Chem.
2009, 307, 142–148
[46] M. P. Boronoev, A. V. Zolotukhina, V I. Ignatyeva, M. V. Terenina, A. L.
Maximov, E. A. Karakhanov, Macromol. Symp. 2016, 363, 57–63
[47] E. Karakhanov, A. Maximov, A. Zolotukhina, E. Mamadli, A. Vutolkina, A.
Ivanov, Catalysts 2017, 7, 86, doi:10.3390/catal7030086
[48] A. L. Maximov, A. V. Zolotukhina, A. A. Mamedli, L. A. Kulikov, E. A.
Karakhanov, ChemCatChem 2018, 10, 222–233
[49] G. Beamson, D. Briggs, High Resolution XPS of Organic Polymers: The
Scienta ESCA300 Database,John Wiley & Sons, Chichester, UK, 1992, p.
295.
[50] a) D. Briggs, G. Beamson, Anal. Chem. 1992, 64, 1729–1736; b) B. R.
Strohmeier, Appl. Surf. Sci. 1991, 47, 225–234; c) A. J. Pertsin, M. M.
Gorelova, V. Y. Levin, L. I. Makarova, J. Appl. Polym. Sci. 1992, 45, 1195–
1202; d) P. Laoharojanaphand, T. J. Lin, J. O. Stoffer, J. Appl. Polymer Sci.
1990, 40, 369–384.
ChemistryOpen 2019, 8, 358–381
www.chemistryopen.org
380
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA

Full Papers
Weerachawanasak, O. Mekasuwandumrong, M. Arai c, Sh.-I. Fujita, P.
Praserthdam, J. Panpranot, J. Catal. 2009, 262, 199–205
[77] E. M. M. de Brabander-van den Berg, E. W. Meijer, Angew. Chem. Int. Ed.
Engl. 1993, 32, 1308–1312
[78] M. Karaki, A. Karout, J. Toufaily, F. Rataboul, N. Essayem, B. Lebeau, J.
Catal. 2013, 305, 204–216.
1
2
3
4
5
6
7
8
[75] J.-J. Zou, X. Zhang, J. Kong, L. Wang, Fuel 2008, 87, 3655–3659
[76] a) D. V. Sokolsky, A. Ualikhanova, A.Ye. Temirbulatova, A. A. Dembitsky,
B. T. Mailyubaev, Russ. J. Appl. Chem. 1988, 61, 2360–2363 (Russ.);
b) T. N. Antonova, I. A. Abramov, V. S. Feldblyum, I. G. Abramov, A. S.
Danilova, Petrol. Chem. 2009, 49, 366–368; c) A. Behr, V. Manz, A. Lux, A.
Ernst, Catal. Lett. 2013, 143, 241–245; d) G. Liu, Zh. Mi, X. L. Wang, Ind.
Zhang, Eng. Chem. Res. 2005, 44, 3846–3851; e) D. Skála, J. Hanika, Petrol
Coal 2003, 45, 105–108; f) M. Hao, B. Yang, H. Wang, G. Liu, S. Qi, J. Phys.
Chem. A 2010, 114, 3811–3817
Manuscript received: December 5, 2018
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52
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