Microwave-assisted hydroarylation of styrenes catalysed by transition metal oxide nanoparticles supported on mesoporous aluminosilicates

Article abstract of DOI:10.1016/j.molcata.2015.06.010

Abstract The addition of phenols to styrene to form ortho and para-(1-phenylethyl) phenols was catalysed by a range of metal oxide nanoparticles supported on mesoporous aluminosilicates (M/Al-SBA-15 catalysts) under microwave irradiation. Moderate to excellent yields to products could be obtained at short times of reaction (typically 10 min). 0.5%Fe/Al-SBA-15 as readily available, environmentally friendly and cheap catalysts exhibited remarkable improvements in yield as compared to the majority of utilized catalysts. The heterogeneous catalyst can be reused at least three times without a significant loss in activity.

Full text of DOI:10.1016/j.molcata.2015.06.010

Journal of Molecular Catalysis A: Chemical 407 (2015) 32–37
Contents lists available at ScienceDirect
Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Microwave-assisted hydroarylation of styrenes catalysed by transition
metal oxide nanoparticles supported on mesoporous aluminosilicates
Reza Hosseinpoura,b, Antonio Pinedab, Angel Garciab, Antonio A. Romerob,
Rafael Luqueb,∗
a Tarbiat Modares University, Department of Organic Chemistry, Tehran, Iran
b Departamento de Quimica Organica, Universidad de Cordoba, Edificio Marie-Curie (C-3), Campus de Rabanales, Ctra. Nnal IV-A, Km 396, E14014,
Cordoba, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
The addition of phenols to styrene to form ortho and para-(1-phenylethyl) phenols was catalysed by a
range of metal oxide nanoparticles supported on mesoporous aluminosilicates (M/Al-SBA-15 catalysts)
under microwave irradiation. Moderate to excellent yields to products could be obtained at short times
of reaction (typically 10 min). 0.5%Fe/Al-SBA-15 as readily available, environmentally friendly and cheap
catalysts exhibited remarkable improvements in yield as compared to the majority of utilized catalysts.
The heterogeneous catalyst can be reused at least three times without a significant loss in activity.
© 2015 Elsevier B.V. All rights reserved.
Received 27 February 2015
Received in revised form 5 June 2015
Accepted 10 June 2015
Available online 16 June 2015
Keywords:
Supported nanoparticles
Al-SBA-15
Hydroarylation
Phenols
Styrenes
1. Introduction
to alkynes [13,14] or alcohols [15] are elegant examples of these
types of transformation. In particular, the use of aromatic-derived
Alkenes are attractive starting materials for organic synthe-
sis as they can be easily functionalized using a plethora of both
oxidative and reductive mono- and difunctionalization methods
[1]. In general, Friedel–Crafts alkylations and acylations are one
of the most powerful methods for Carbon Carbon bond-forming
reactions [2–4]. These reactions have been traditionally performed
using strong Lewis acids including TiCl4, BF3·OEt2, and AlCl3 as well
as mineral acids such as HF and H2SO4. Ongoing investigation pro-
grams are currently trying to identify and design catalysts that
address typical problems in Friedel–Crafts chemistries including
high catalyst loading, low selectivity, over-alkylation, formation of
byproducts (salts) and sensitivity toward moisture and strong acid
media.
alkenes has been found to be very useful and practical as the result-
ing diarylalkane block represents an important part in biologically
active compounds and pharmaceuticals substrates that include
haplopappin, phenprocoumone, papaverine, or afenopin (Fig. 1).
During the past decade, transition metal nanoparticles sup-
ported on mesoporous materials emerged as promising nanoen-
tities to develop readily available, cheaper and more efficient
catalysts as alternatives to traditionally employed in several cat-
alytic reactions, especially for their use in heterogeneous catalysis
[16–18]. Nanoparticles can offer remarkably different properties
as compared to bulk metals based on their degenerated density of
energy states and small sizes which often lead to high activities and
specificities in chemical reactions [19,20].
C
H transformations of arenes and heteroarenes have recently
Solid acid catalysts are increasingly utilised in organic transfor-
mations due to their simple separation from the reaction mixture
and possible reuse. Additionally, the catalytic activity of solid
acid (e.g. aluminosilicates) can be increased via incorporation of
metal ions such as CuII, ZnII, FeIII, etc., which causes the gen-
eration of highly active Lewis acid sites [21]. The combination
of such active Lewis acid site along with the available Brönsted
acid sites in metal-exchanged Al-SBA-15 together with the high
surface area and exceptional textural properties and hydrother-
mal stability can facilitate reactions by localizing the reactants in
attracted a considerable interest in organic synthesis. Protocols
have been developed using various transition-metal and acid cat-
alysts [5,6]. The addition of olefins to acetophenones [7,8] and
aromatic imines [9,10], alkene additions to arenes [2,4] and het-
erocyclic compounds [11,12] as well as the addition of aromatics
∗
Corresponding author.
E-mail address: q62alsor@uco.es (R. Luque).
http://dx.doi.org/10.1016/j.molcata.2015.06.010
1381-1169/© 2015 Elsevier B.V. All rights reserved.

R. Hosseinpour et al. / Journal of Molecular Catalysis A: Chemical 407 (2015) 32–37
33
HO
radiation. Scans were performed over a 2␪ range from 10 to 80 at
step size of 0.018◦ with a counting time per step of 20 s.
O
OH
O
Nitrogen adsorption measurements were carried out at 77 K
using an ASAP 2000 volumetric adsorption analyzer from
Micromeritics. Samples were degassed for 24 h at 130 ◦C under vac-
cum (p < 10−2 Pa) prior to adsorption measurements. Surface areas
were calculated according to the BET (Brunauer–Emmet–Teller)
HO
O
O
O
O
OH
phenprocoumon
equation. Pore volumes (VBJH) and pore size distributions (DBJH
were obtained from the N2 desorption branch.
)
haplopappin
TEM micrographs were recorded on a JEOL 2010HR instrument
operating at 300 kV fitted with a multiscan CCD camera for ease and
speed of use as well as with an EDX system. The lattice resolution
is around 0.2 nm.
The surface acidity was measured in a dynamic mode by means
of a pulse chromatographic technique of gas-phase adsorption of
pyridine (PY) at 300 ◦C (sum of Brönsted and Lewis acid sites) and
2,6-dimethylpyridine (DMPY, Brönsted sites) as probe molecules
[29].
Fig. 1. Biologically and pharmaceutically active compounds.
their pores/external surfaces and providing high local concentra-
tion [22,23]. Among these transition metals, iron NPs have attracted
a great interest in the design of environmentally friendly and effec-
tive catalysts as alternative to traditionally employed noble metal
catalysts in several catalytic reactions. Fe-based systems have been
proven to be the most effective and green system in modern organic
synthesis because of their lower toxicity and easy accessibility
[24,25].
In this work, we have aimed to combine the high activities and
specificities of supported metal oxide nanoparticles with a simple
but important C H transformation such as the hydroarylation of
styrenes with phenol derivatives [26]. A number of catalytic sys-
tems were developed and utilised in the proposed reaction under
microwave irradiation.
DRIFTs characterisation of surface acidity involved the acid sites
titration with PY. The basic probe was introduced by bubbling a
stream of dehydrated and deoxygenated nitrogen (20 mL min−1
)
through the liquid and into the sample chamber containing the
neat (no KBr diluted) catalyst sample at 100 ◦C. Samples were equi-
librated for at least 1 h at each temperature (100, 150, 200 or 300 ◦C)
and reactant condition prior to collecting the spectra.
2.3. Microwave-assisted reactions
2. Experimental
Microwave irradiation was employed as alternative energy
source to promote the reactions (as opposed to conventional heat-
ing) in view of the possibilities to speed up reactions with often
changes in selectivity due to the rapid and homogeneous heating
achieved under microwave irradiation, particularly for supported
metals [30]. In a typical reaction, 1 mmol (0.115 mL) styrene, 1.5
mmol (0.141 g) phenol, 2 mL solvent (cyclohexane) and 0.050 g
catalyst were added to a pyrex vial and microwaved in a pressure-
controlled CEM-Discover microwave reactor for a period of time,
typically 10 min at 200 W (120 ◦C, maximum temperature reached)
under continuous stirring. Samples were then withdrawn from the
reaction mixture and analysed by GC and GC/MS Agilent 6890N fit-
ted with a capillary column HP-5 (30 m × 0.32 mm × 0.25 ␮m) and
a flame ionisation detector (FID).
The identity of the products was confirmed by GC–MS. Bblank
reaction showed the thermal effects in the reaction were negligible
(less than 5% conversion was obtained after 24 h). Response factors
of the reaction products were determined with respect to the sub-
strates from GC analysis using standard compounds in calibration
mixtures of specified compositions. The microwave method was
generally power controlled (by an infra-red probe) where the sam-
ples were irradiated with the required power output (settings at
maximum power, 300 W) to achieve different temperatures in the
range of 115–120 ◦C.
2.1. Materials synthesis
Al-SBA-15 materials were prepared in a similar way to those
reported in our previous work, following the previously reported
methodology by Bonardet et al. [22,27] and characterized using
available techniques including X-ray diffraction (XRD), nitrogen
physisorption, elemental analysis and surface acidity. Al-SBA-15
parent materials possessed a Si/Al ratio of 41 and were selected
as catalyst support due to their excellent hydrothermal stabilities
and textural properties (high surface area and appropriate meso-
porosity) combined with a good balance of Brönsted/Lewis acid
sites of moderate acidic strength. Importantly, we also needed a
mechanically resistant support to the milling process utilized for
the deposition of metal oxide nanoparticles.
The supported catalysts were prepared following a previously
reported novel dry mechanochemical approach [28]. In a typical
synthesis, 0.2 g Al-SBA-15 was ground with the needed quantity
of metal precursor (e.g. FeCl2·4H2O or AgNO3) in a Retsch PM-100
planetary ball mill using a 125 mL reaction chamber and 10 mm
stainless steel balls. Milling conditions were 10 min at 350 rpm
(previously optimized conditions [28]).
Upon milling, as synthesized materials were conditioned to
remove the excess of unreacted and/or physisorbed precursor
and directly calcined at 400 ◦C under air for 4 h. The conditioning
step included thorough washing steps with ethanol and then ace-
tone under mild heating (40–50 ◦C). Prepared catalysts, denoted as
Fe0.5%AlSBA, Fe1%AlSBA, Fe2%AlSBA, Fe4%AlSBA, Ag1%AlSBA and
Ag10%AlSBA, were characterized by a number of techniques includ-
ing X-ray diffraction (XRD), N2 physisorption, TEM and EDX. A
similar Co10%AlSBA material was synthesized for comparative pur-
poses.
3. Results and discussion
Textural and surface properties of the materials have been sum-
marized in Table 1. Surface acidities measured using pyridine (PY)
and 2,6-dimethylpyridine (DMPY) as probe molecules pointed to a
significant increase of Lewis acidity (difference between PY-DMPY
values) upon Fe incorporation in the materials. These findings are in
good agreement with previous reports from the group [23,28]. In
any case, ball-milling (BM) synthesized nanomaterials possessed
similar textural properties (e.g. surface areas, pore size and vol-
umes) as compared to the parent aluminosilicate. Comparatively,
the incorporation of Ag into the SBA-15 aluminosilicate material
2.2. Characterization
Structural properties of the materials were determined by XRD
on a Siemens D-5000 (40 kV, 30 mA) using Cu K␣ (ꢀ = 0.15418 nm)

34
R. Hosseinpour et al. / Journal of Molecular Catalysis A: Chemical 407 (2015) 32–37
Table 1
Textural properties [surface area (m2 g−1), pore size (nm) and pore volume (mL g−1)] and surface acidity [measured as mmol adsorbed of probe molecule (PY or DMPY) per
gram of catalyst] of metal NPs supported on mesoporous materials and parent Al-SBA-15.
Surface acidity at 300 ◦C (␮mol base g−1
)
Catalyst
Metal loading (wt%)
Surface area (m2 g−1
)
Pore size/volume (nm/mL g−1
)
PY (total acidity)
DMPY (Brönsted acidity)
Al-SBA-15
Fe0.5/AlSBA
Fe1/AlSBA
Fe2/AlSBA
Fe4/AlSBA
Ag1/AlSBA
Ag10/AlSBA
Co10/AlSBA
–
762
630
663
645
655
512
606
492
6.4/ 0.60
6.3/0.48
6.3/0.61
6.3/0.50
6.8/0.52
6.5/0.46
6.7/0.57
6.0/0.33
81
150
111
141
110
126
108
144
77
90
96
87
90
116
97
100
0.9
1.1
2.3
4.0
0.7
11.7
9.6
Fig. 2. TEM images of Fe0.5/AlSBA (left) and Ag10/AlSBA (right) with their corresponding size distribution histograms underneath. An average of ca. 20 nanoparticles were
size-measured for the preparation of the histograms.
equally increased both Lewis and Bronsted acidities (particularly
for the 1%Ag material). Metal loadings determined by ICP/MS were
generally close to theoretical values in most cases, except for the
case of Fe0.5%/AlSBA in which a larger Fe content was observed
(Table 1). Supported nanoparticle systems exhibited reduced sur-
face areas but in general fairly similar related textural properties
(pore sizes and volumes) as compared to the parent Al-SBA-15.
XPS characterization of mechanochemically synthesized nanoma-
terials indicated the presence of metal oxides (Fe2O3, hematite
phase [23,28] and AgO) as indicated by the typical binding energies
(711.7 eV for Fe 2p3/2 and 367.5 eV for Ag 3d 5/2) characteris-
tic of previously reported similar metal oxide Fe2O3 [31,32] and
AgO species [33,34]. Nanomaterials were further characterized by
TEM microscopy which confirmed the presence of nanoparticles
supported on the mesoporous aluminosilicates (Figs. 2 and 3).
Fe-containing Al-SBA materials possessed relatively small nanopar-
ticles in size (typically between 2-7 nm depending on the material,
see Figs. 2 A and 3) as compared to larger AgO nanoparticles
observed for Ag1 and particularly higher loaded Ag10/AlSBA (ca.
14 nm average nanoparticle size, Fig. 2B).
Initially, a preliminary solvent screening was conducted in
order to find out the optimum solvent conditions for the reaction.
Fig. 3. Representative TEM images of Fe0.5/AlSBA (left) and Fe4/AlSBA (right). A significant differences in nanoparticle size can be observed between materials. Nanoparticles
can be clearly visualized as dark spots in TEM images.

R. Hosseinpour et al. / Journal of Molecular Catalysis A: Chemical 407 (2015) 32–37
35
Table 2
Solvent screening in the hydroarylation of styrene with phenol using Fe0.5%/AlSBA.a
Entry
Solvent
Conversion (%)b
Selectivity (ortho-:para-)c
1
2
3
4
5
6
7
ACN
DMF
Toluene
Ethyl acetate
Ethanol
DCM
–
–
70
–
–
–
–
61:38
–
–
60:39
56:43
94
>99
Cyclohexane
Reaction conditions: (1 mmol, 0.115 mL) styrene, (1.5 mmol, 0.141 g) phenol, 0.050 g catalyst, 2 mL solvent, 200 W, 10 min reaction, T = 120 ◦C.
GC conversion of styrene.
GC yield of arylated products.
a
b
c
Fe0.5%/Al-SBA-15 was selected as catalyst for solvent optimisa-
Importantly, the effect of metal loading in the catalytic activ-
ity was investigated in both Fe and Ag-containing materials. An
increase in metal loading (from 0.5 to 4 wt.%) in Fe/Al-SBA-15
materials involved a gradual decrease in conversion as well as
an interesting switch in selectivity from ortho- to para- (Table 3,
entries 3 to 6). A similar effect was observed when comparing the
activity of Ag1 and Ag10/AlSBA materials (Table 3, entries 7 and 8)
as well as a Co10/AlSBA. These findings in fact pointed out that the
catalytic activity in the systems is not only influenced by acidity (i.e.
Fe0.5 and Fe2/AlSBA have almost identical textural and surface acid
properties, see Table 1) but most importantly nano-effects includ-
ing nanoparticle size and dispersion could be playing a major role
in the observed differences. TEM analysis was subsequently con-
ducted in this regard and a comparison between two Fe-containing
materials (Fe0.5 and Fe4/AlSBA) has been included in Fig. 3.
TEM images evidenced significant differences in terms of
nanoparticle sizes for Fe0.5 (2.5 nm, average particle size) and
Fe4/AlSBA (7 nm, average particle size) which can be correlated
with the significantly different catalytic activities in both materi-
als. In general, nanoparticle sizes were found to gradually increase
with metal loading. These results were also in good agreement
with reduced catalytic activities found for high loaded Ag and Co-
containing materials (e.g. Ag10/AlSBA and Co10/AlSBA, Table 2)
despite their relatively similar textural and surface acid properties
as compared to low-loaded highly active materials (Table 1).
The recycling and stability of the catalyst under the investi-
gated conditions was subsequently studied (Fig. 4). After each
cycle, the reaction mixture was allowed to cool down to room
temperature and the catalyst was separated by filtration. The recov-
tion based on previous results of the group which pointed out the
optimum activities of Fe0.5%/Al-SBA-15 with respect to other cat-
alytic systems in C H transformations [35]. Results summarized in
Table 2 indicated that cyclohexane is the solvent of choice (Table 2,
entry 7). Although the reaction did not proceed in acetonitrile, DMF,
ethylacetate and ethanol after 10 min, almost quantitative conver-
sion of styrene was observed in dichloromethane (DCM), with a
good conversion also in toluene. Comparatively, complete conver-
sion of styrene to products was observed in cyclohexane within
a remarkable short reaction time (Table 2, entry 7). These findings
were in good agreement with previously reported literature results
[23,35].
Different nanomaterials were subsequently investigated under
typically short reaction times (10 min) in the same microwave-
assisted model reaction in cyclohexane. Upon reaction optimisa-
tion, Table 3 summarises the main findings of this work. Blank
runs (in the absence of catalyst) provided no conversion in the
systems (entry 1), while the acidic Al-SBA-15 support gave an inter-
esting 64% conversion after 10 min of reaction with an improved
selectivity to the para- isomer (entry 2). As compared to various
M-Al-SBA-15, the corresponding Fe0.5/AlSBA exhibited optimum
activities in the reaction at times of reaction of 10 min (Table 3,
entry 3). Ortho-(1-phenylethyl) phenol (55%) was obtained as
favoured reaction product. Ag1/AlSBA also provided quantitative
conversion in the systems, with a 60% selectivity to the para- deriva-
tive (Table 3, entry 7).
Table 3
Effect of catalyst and time in the hydroarylation of phenol with styrene.a
Entry
Catalyst
Conversion (%)b
Selectivity (ortho-/ para-c)
1
2
3
4
5
6
7
8
9
Blank
–
64
>99
88
85
–
Al-SBA-15
Fe0.5/AlSBA
Fe1/AlSBA
Fe2/AlSBA
Fe4/AlSBA
Ag1/AlSBA
Ag10/AlSBA
Co10/AlSBA
45:55
56:44
45:55
39:61
47:53
40:60
88:12
55:45
63
>99
<15
74
a
Reaction conditions: (1 mmol, 0.115 mL) of styrene, (1.5 mmol, 0.141 g) of phe-
nol, 50 mg of catalyst, 2 mL of cyclohexane, 200 W, 10 min reaction, T = 115 − 120 ◦C.
Fig. 4. Reusability studies of Fe0.5/AlSBA in the Reaction of Phenol with Styrene.
Reaction conditions: 1 mmol (0.115 mL) styrene, 1.5 mmol (0.141 g) phenol, 50 mg
of catalyst, 2 mL of cyclohexane, 200 W, T = 120 ◦C, 10 min reaction per run.
b
GC conversion of styrene.
GC yield of arylated products.
c

36
R. Hosseinpour et al. / Journal of Molecular Catalysis A: Chemical 407 (2015) 32–37
Table 4
Scope of the hydroarylation reaction using phenol derivatives and styrene.a
Entry
1
ArOH
Time (min)
Conversion (mol%)b
Selectivities (mol%)c
10
81
2
3
4
10
10
10
<20
90
>99
5
10
10
82
96
6
a
Reaction conditions: (1 mmol, 0.115 mL) styrene, (1.5 mmol) phenol derivatives, 0.05 g Fe0.5/AlSBA, 2 mL of solvent, 200 W, T = 120 ◦C.
GC conversion of styrene.
GC yield of isomers.
b
c
ered catalyst was then washed with cyclohexane, methanol and
4. Conclusions
dichloromethane and dried at 100 ◦C for 4 h. The catalyst was then
reused without any further treatment. The recycled Fe0.5/AlSBA
catalyst exhibited an excellent conversion under the investigated
reaction conditions, preserving over 90% of their initial activity after
four uses.
To explore the scope and limitation of the reaction, the opti-
mized conditions were subsequently extended to several other
substituted phenols (Table 4). Different isomers could be obtained
depending on the substituent and directing groups on the phenol
ring. In any case, excellent styrene conversion to target products
could be achieved in most cases after 10 min of reaction, with the
exception of 2,4-dimethylphenol (Table 4, entry 2).
A simple and efficient protocol has been developed for the
hydroarylation of phenols with styrene catalysed by supported
nanoparticles on mesoporous Al-SBA-15 under microwave irradia-
tion. Fe0.5/AlSBA provided optimised yields to products under mild
reaction conditions and short times of reaction (typically 10 min).
Catalysts were highly stable and reusable under the investigated
conditions up to four uses, with a protocol also amenable to a
range of substituted phenols. The designed supported nanoparticle
systems are envisaged to have a remarkable potential for further
coupling and oxidation chemistries that will be reported in due
course.

R. Hosseinpour et al. / Journal of Molecular Catalysis A: Chemical 407 (2015) 32–37
[15] J. Choudhury, S. Podder, S. Roy, J. Am. Chem. Soc. 127 (2005) 6162.
37
Acknowledgments
[16] A.P. Wight, M.E. Davis, Chem. Rev. 102 (2002) 3589.
[17] A. Corma, H. Garcia, Chem. Rev. 102 (2002) 3837.
[18] T. Mallat, A. Baiker, Chem. Rev. 104 (2004) 3037.
Rafael Luque gratefully acknowledges Spanish MICINN for
financial support via the concession of a RyC contract (ref: RYC-
2009-04199) and funding under project CTQ2011-28954-C02-02
(MEC). Consejeria de Ciencia e Innovacion, Junta de Andalucia is
also gratefully acknowledged for funding project P10-FQM-6711.
[19] R.J. White, R. Luque, V. Budarin, J.H. Clark, D.J. Macquarrie, Chem. Soc. Rev. 38
(2009) 481.
[20] J.M. Campelo, D. Luna, R. Luque, J.M. Marinas, A.A. Romero, ChemSusChem 2
(2009) 18.
[21] Z. Luan, M. Hartmann, D. Zhao, W. Zhou, L. Kevan, Chem. Mater. 11 (1999)
1621.
[22] C. Gonzalez-Arellano, R.A.D. Arancon, R. Luque, Green Chem. 16 (2014) 4985.
[23] A.M. Balu, A. Pineda, K. Yoshida, J.M. Campelo, P.L. Gai, R. Luque, A.A. Romero,
Chem. Commun. 46 (2010) 7825.
[24] T. Stemmler, A.E. Surkus, M.M. Pohl, K. Junge, M. Beller, ChemSusChem 7
(2014) 3012.
[25] Iron Catalysis: Fundamentals and Applications, in: B. Plietker (Ed.), Springer,
The Netherlands, 2011.
[26] S. Haldar, S. Koner, J. Org. Chem. 75 (2010) 6005.
[27] B. Jarry, F. Launay, J.P. Nogier, V. Montouillout, L. Gengembre, J.L. Bonardet,
Appl. Catal. A: Gen. 309 (2006) 177.
[28] A. Pineda, A.M. Balu, J.M. Campelo, A.A. Romero, D. Carmona, F. Balas, J.
Santamaria, R. Luque, ChemSusChem 41 (2011) 561.
[29] J.M. Campelo, D. Luna, R. Luque, J.M. Marinas, A.A. Romero, J.J. Calvino, M.P.
Rodríguez-Luque, J. Catal. 230 (2005) 327.
[30] C.O. Kappe, B. Pieber, D. Dallinger, Angew. Chem. Int. Ed. 52 (2013)
1088–1094.
References
[1] M. Beller, J. Seayad, A. Tillack, H. Jiao, Angew. Chem. Int. Ed. 43 (2004) 3368.
[2] M. Bandini, A. Melloni, A.U. Ronchi, Angew. Chem. Int. Ed. 43 (2004) 550.
[3] G. Olah, V. Prakash Reddy, G.K. Surya Prakash, Kirk-Othmer Encyclopedia of
Chemical Technology, Hoboken, 2000.
[4] G.K. Surya Prakash, P.J. Linarez-Palomino, K. Glinton, S. Chacko, G. Rasul, T.
Mathew, G.A. Olah, Synlett 7 (2007) 1158.
[5] F. Muhlthau, O. Schuster, T. Bach, J. Am. Chem. Soc. 127 (2005) 9348.
[6] J. Liu, E. Muth, U. Flörke, G. Henkel, K. Merz, J. Sauvageau, E. Schwalke, G.
Dyker, Adv. Synth. Catal. 348 (2006) 456.
[7] F. Kakiuchi, T. Uetsuhara, Y. Tanaka, N. Chatani, S. Murai, J. Mol. Catal. A:
Chem. 182 (2002) 511.
[8] Y. Guari, A. Castellanos, S. Sabo-Etienne, B. Chaudret, J. Mol. Catal. A: Chem.
212 (2004) 77.
[9] F. Kakiuchi, M. Yamauchi, N. Chatani, S. Murai, Chem. Lett. (1996) 11.
[10] C.-H. Jun, J.-B. Hong, Y.-H. Kim, K.-Y. Chung, Angew. Chem. Int. Ed. 39 (2000)
3440.
[11] R.K. Thalji, K.A. Ahrendt, R.G. Bergman, J.A. Ellman, J. Am. Chem. Soc. 123
(2001) 9692.
[12] K.A. Ahrendt, R.G. Bergman, J.A. Ellman, Org. Lett. 5 (2003) 1301.
[13] F. Kakiuchi, Y. Yamamoto, N. Chatani, S. Murai, Chem. Lett. (1995) 681.
[14] C.G. Jia, W.T. Lu, J. Oyamada, T. Kitamura, K. Matsuda, M. Irie, Y. Fujiwara, J.
Am. Chem. Soc. 122 (2000) 7252.
[31] Handbook of X-Ray Photoelectron Spectroscopy, in: C.D. Wagner, W.N.L.E.
Riggs, G.F. Davis, G.E. Moulder (Eds.), Muilenberg, Perkin Elmer, Eden Prairie,
1979.
[32] X. Deng, J. Lee, D. Matranga, Surf. Sci. 604 (2010) 627.
[33] <http://www.xpsfitting.com/2013/04/silver.html/>.
[34] G.B. Hoflund, Z.F. Hazos, G.N. Salaita, Phys. Rev. B 62 (2000) 11126.
[35] R. Hosseinpour, A. Pineda, A. Garcia, A.A. Romero, R. Luque, Catal. Commun.
48 (2014) 73.