Exploring palladium nanoparticles protected with alkanethiolates functionalized with organometallic units as potential catalysts for sequential reactions

Article abstract of DOI:10.1016/j.molcata.2013.04.006

Palladium nanoparticles peripherally functionalized with "RuCl ₂(p-cymene)" (NP2), "RhCl(cod)" (NP3) and "PdCl(η³-2-MeC₃H₄)" (NP4) units show catalytic activity in CC coupling reactions, hydrogenation and hydrovinylation processes. We report for the first time an example of a catalytic precursor for the hydrovinylation/CC coupling sequential process by using the two catalytic centres displayed by NP4, the Pd core and the PdCl(η³-2-MeC₃H₄) moieties.

Full text of DOI:10.1016/j.molcata.2013.04.006

Journal of Molecular Catalysis A: Chemical 376 (2013) 7–12
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Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Exploring palladium nanoparticles protected with alkanethiolates functionalized
with organometallic units as potential catalysts for sequential reactions
Mario Friederici, Inmaculada Angurell∗, Oriol Rossell∗, Miquel Seco, Guillermo Muller
Departament de Química Inorgànica, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Palladium nanoparticles peripherally functionalized with “RuCl2(p-cymene)” (NP2), “RhCl(cod)” (NP3)
and “PdCl(␩3-2-MeC3H4)” (NP4) units show catalytic activity in C C coupling reactions, hydrogenation
and hydrovinylation processes. We report for the first time an example of a catalytic precursor for the
hydrovinylation/C C coupling sequential process by using the two catalytic centres displayed by NP4,
the Pd core and the PdCl(␩3-2-MeC3H4) moieties.
Received 16 January 2013
Received in revised form 24 March 2013
Accepted 6 April 2013
Available online 16 April 2013
© 2013 Elsevier B.V. All rights reserved.
Keywords:
Functionalized palladium nanoparticles
Suzuki reaction
Cyclohexadiene hydrogenation
Styrene hydrovinylation
Sequential reactions
1. Introduction
our group [8]. Our interest was to evaluate the possibility of using
such kind of NPs as catalysts in multistep processes and, in turn,
Over the last decade, a huge number of reports have appeared
on the use of transition metal nanoparticles in catalysis because
of their size, high ratio of surface area to volume [1] and ease of
preparation [2]. It is well-known that the NPs are prone to for-
mation of bulk metals and require the use of protecting ligands
or linkers to prevent aggregation and precipitation. However, in
many cases, the role of the linkers is not only restricted as pro-
tecting agents, but also they can play other relevant functions. For
example, voluminous dendrons may act as selective gates to con-
trol access of small molecules to the metal core, that is, they can
act as nanofilters [3]. On the other hand, the attachment of chiral
ligands onto the surface of the core may induce enantiomeric activ-
ity [4–6]. The enantio control depends on how the ligands are able
to transmit their influence to substrate molecules coordinated to
the particle in their vicinity [7]. In this context, it is reasonable to
assume that the synthesis of peripherally functionalized NPs with
organometallic fragments would enhance their catalytic efficiency
and applicability. For testing this hypothesis we have centred our
studies on a set of palladium nanoparticles (Pd NPs) peripherally
functionalized with diverse metal fragments recently reported by
to detect potential synergetic effects between the Pd core and the
organometallic units. To date, the number of examples of sequen-
tial reactions catalyzed by metal nanoparticles is scarce. Fan and
co-workers [9] described a tandem reaction based on a Suzuki cou-
pling, followed by a hydrogenation reaction and Gómez applied
Pd NPs in sequential reactions involving C C coupling and hydro-
genation steps using ionic liquid phase [10]. Here we report for
the first time an example of a two-step process in that two dif-
ferent metal catalytic centres of a same nanoparticle are involved
at once. The sequential process consists of the hydrovinylation of
4-bromostyrene followed by a C C coupling Suzuki reaction with
phenylboronic acid. Although the yield obtained in the synthesis
of the final compound is rather modest, the success of the process
opens an area scarcely explored with metal nanoparticles, but with
undeniable potential.
2. Experimental
2.1. Materials and methods
Phenylboronic acid and 1,3-cyclohexadiene were sourced from
Fluka and 4-bromoanisole, AgPF6, styrene and 4-bromostyrene
(98%) from Aldrich. Palladium nanoparticles NP0, NP1, NP2, NP3
and NP4 were synthesized as reported in the literature [8].
Nanoparticles metal content (% in mass): NP0, 77.5% Pd; NP1, 55.5%
∗
Corresponding author. Tel.: +34 934037057 (I.A.); +34 934039136 (O.R.).
E-mail addresses: inmaculada.angurell@qi.ub.es (I. Angurell),
oriol.rossell@qi.ub.es (O. Rossell).
1381-1169/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcata.2013.04.006

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M. Friederici et al. / Journal of Molecular Catalysis A: Chemical 376 (2013) 7–12
Pd; NP2, 57.0% Pd and 3.4% Ru(II); NP3, 66.2% Pd and 2.9% Rh(I); NP4,
43.5% Pd(0) and 5.2% Pd(II).
All solvents were distilled from appropriate drying agents.
Deionised water was obtained from Millipore Elix 3 purification
system. All manipulations were performed under purified nitrogen
using standard Schlenk techniques.
2.5. Typical procedure for the sequential reaction
(4-bromostyrene hydrovinylation and Suzuki–Miyaura cross
coupling)
In a 100 mL Schlenk flask, a mixture of 0.028 g (1.37 × 10−5 mol
Pd(II), 1.14 × 10−4 mol Pd(0)) or 0.056 g (2.74 × 10−5 mol Pd(II),
2.28 × 10−4 mol Pd(0)) of catalyst precursor NP4, AgPF6 or
NaBARF (BARF = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate)
Hydrogenation reactions were carried out in a Fisher–Porter
reactor.
Hydrovinylation reactions were performed in a stainless steel
autoclave fitted with an external jacket connected to an isobutyl
alcohol bath, and the temperature was controlled using a thermo-
stat to 0.5 ◦C. The internal temperature was monitored using a
thermopar coupled to a digital recorder.
The routine GC analyses were performed on an Agilent Tech-
nologies 6890 N. Gas chromatography analysis coupled with mass
spectrometry were performed on an Agilent Technologies 7820
coupled with a mass detector 5975, both instruments loading a
30 m HP5 capillary column.
(1.38 × 10−5
or
2.76 × 10−5 mol)
and
4-bromostyrene
(1.38 × 10−3 mol) in 20 mL of freshly distilled CH2Cl2 was main-
tained stirring for 15 min in the dark under N2. After filtering off the
NaCl or AgCl formed, the solution was placed in an autoclave ther-
mostatically controlled (25 ◦C). The autoclave was then pressurized
with ethylene to a pressure of 15 bar. After 6 h the autoclave was
depressurized slowly. Then, the reaction mixture was placed in a
50 mL Schlenk flask, and CH2Cl2 was evaporated almost to dryness
under vacuum. 20 mL of a 4:1, toluene/water mixture were added
(or alternatively more CH2Cl2 and water to reach a ratio of 4 to 1
(CH2Cl2/H2O)) and successively 2.06 × 10−3 or 2.76 × 10−3 mol of
phenylboronic acid and 2.76 × 10−3 or 3.45 × 10−3 mol of K2CO3
were added. The mixture was kept to stir under reflux or placed
in a reactor at 110 ◦C for 24 h. After the reaction mixture was
processed, the quantitative distribution of the fractions of the
products was determined by gas chromatography analysis coupled
with mass spectrometry using ethylbenzene as internal standard.
2.2. Typical procedure for Suzuki cross coupling reaction
In a 100 mL Schlenk flask, 3.7 mg of NP0, or 5.2 mg of NP1, or
5.0 mg of NP2, or 6.6 mg of NP3, or 4.3 mg of NP4 (2.7 × 10−5 mol
Pd) were dissolved in 24 mL of a solution of THF/H2O (2:1) and
4-bromoanisole (1 mmol), phenylboronic acid (2 mmol) and NaOH
(3 mmol) were added. The mixture was allowed to stir under N2 at
room temperature for the required time. To determine the compo-
sition of the mixture of catalysis, an aliquot was taken and CH2Cl2
and H2O were added in equal volumes. The mixture was stirred
and the organic phase was extracted and dried over anhydrous
MgSO4. The quantitative distribution of the fractions of the coupling
products was determined by gas chromatography analysis.
3. Results and discussion
The Pd NPs used in this work are shown in Scheme 1. NP1 is
formed by a Pd core protected with two different thiol ligands. The
shorter one, hexanethiolate is introduced to provide solubility to
the system in organic solvents and the larger is the alkanethiolate
HS(CH2)11OOCC6H4PPh2. The free phosphine ligand permits facile
coordination to different metal units: “RuCl2(p-cymene)” (NP2),
“RhCl(cod)” (NP3) and “PdCl(␩3-2-MeC3H4)” (NP4). For compara-
tive purposes we have carried out some catalytic tests using the Pd
NPs containing uniquely 1-hexanethiol as protected ligands (NP0).
Our initial studies began by screening the catalytic behaviour
of the metal core and that of the peripheral metal fragments of the
NPs. In some cases, the simultaneous participation of both catalytic
centres could be evidenced. The results given in Tables 1–4 were
obtained as a mean of at least three runs.
2.3. Typical procedure for hydrogenation of 1,3-cyclohexadiene
In a 50 mL Schlenk flask, 5.0 mg of NP0 (3.6 × 10−5 mol Pd), or
5.0 mg of NP1 (2.6 × 10−5 mol Pd), or 5.0 mg of NP3 (3.1 × 10−5 mol
Pd, 1.4 × 10−6 mol Rh(I)) were dissolved in 10 mL of CH2Cl2 and
0.027 mL (0.283 mmol) of 1,3-cyclohexadiene were added. The
mixture was placed in a reactor and charged with H2 to a pres-
sure of 3 bar at room temperature under stirring. After the desired
time the reactor was depressurized and the solution was filtered
through a small SiO2 column. The conversion was determined by
gas chromatography using ethylbenzene as internal standard.
3.1. Suzuki–Miyaura C C coupling reaction
Palladium-catalyzed Suzuki–Miyaura cross couplings of aryl
halides and arylboronic acids to give biaryl structures have
found applications in fine chemical and pharmaceuticals synthe-
sis [11]. Here, we analyzed the C C coupling reaction between
4-bromoanisole and phenylboronic acid in a biphasic mixture of
THF–water with NaOH as a base under ambient conditions, in pres-
ence of NP0–NP4 (Scheme 2). Table 1 shows the reaction conditions
and conversion. The results obtained in entries 1 and 2 are in line
with those previously published in similar reaction conditions [12].
That is, the Pd core is an efficient catalyst thanks to the fact that the
hexanethiol linkers do not prevent the approach of the reagents
to its surface. The cross-coupling/homocoupling ratio is about 5:1.
The use of NP1 modifies clearly the efficiency of the system since
after 24 h only traces of the products are obtained (entries 4 and
5) because of the robust blocking phosphine units. However, after
96 h the conversion is complete (entry 6) with complete selectivity.
This behaviour suggests that the reaction only takes place after NP
degradation, due to the strong basic medium, giving Pd–phosphine
species which are very active and selective species. Using NP2 as
catalyst the results are similar to those observed with NP1. That is,
2.4. Typical procedure for styrene hydrovinylation
In a Schlenk, a mixture of 0.055 g of NP4 (2.7 × 10−5 mol Pd(II))
or 0.011 g of NP4 (5.4 × 10−6 mol Pd(II)), AgPF6 (2.7 × 10−5 or
5.4 × 10−6 mol) and styrene or 4-bromostyrene (5.4 × 10−3 mol)
in 10 mL of freshly distilled CH2Cl2 was kept stirring for 15 min
in the dark under N2. After filtering the AgCl formed, the solu-
tion was placed in an autoclave thermostatically controlled (25 ◦C).
The autoclave was then pressurized with ethylene to a pressure
of 15 bar. After the desired time, the autoclave was depressurized
slowly and 10 mL of 10% HCl was added. The mixture was kept
stirring for 10 min to quench the catalyst. The CH2Cl2 layer was
decanted and dried with anhydrous MgSO4. The quantitative dis-
tribution of the fractions of the products was determined by gas
chromatography analysis using ethylbenzene as internal standard.
TOF was calculated respect to the amount of Pd(II) in the nanopar-
ticle surface.

M. Friederici et al. / Journal of Molecular Catalysis A: Chemical 376 (2013) 7–12
9
Scheme 1. Pd nanoparticles used in this work.
Table 1
Suzuki–Miyaura reaction.a
Entry
Time (h)
Cat
% Conversionb
% Cross-coupling/homocoupling of the 4-bromoanisole
% Biphenyl homocoupling productc
1
2
3
4
5
6
7
8
9
6
24
6
NP0
NP0
NP1
NP1
NP1
NP1
NP2
NP2
NP3
NP3
NP4
NP4
25.9
65.2
0
Traces
58.5
100
Traces
81.0
Traces
48.9
43.7
81.9
21.7/4.2
55.5/9.7
2.5
5.4
24
48
96
12
24
12
24
12
24
58/0
100/0
7.9
46.7
78.3/2.7
10.3
10
11
12
48.9/traces
43.7/traces
80.3/1.6
4.5
1.7
9.3
a
Reaction conditions: 1 mmol of substrate, 2 mmol of phenylboronic acid, 3.7 mg of NP0, or 5.2 mg of NP1, or 5.0 mg of NP2, or 6.6 mg of NP3, or 4.3 mg of NP4 catalyst
(2.7 × 10−5 mol Pd), 3 mmol NaOH, THF/H2O (16 mL/8 mL).
b
4-Bromoanisole conversion.
Based on the initial amount of phenylboronic acid.
c
Table 2
1,3-Cyclohexadiene hydrogenation.a
Entry
Catalyst precursor
t (h)
% Conversionb
% Cyclohexene
% Cyclohexane
1
2
3
4
NP0
NP1
NP3
NP3
0.5
0.5
0.5
2
100
23.0
42.7
100
86.0
21.0
40.5
97.0
14.0
2.0
2.2
3.0
a
Reaction conditions: 5.0 mg of catalyst precursor NP0 (3.6 × 10−5 mol Pd), NP1 (2.6 × 10−5 mol Pd), or NP3 (3.1 × 10−5 mol Pd, 1.4 × 10−6 mol Rh(I)), and 0.283 mmol of
1,3-cyclohexadiene, CH2Cl2 (10 mL). H2 pressure, 3 bar. T = 25 ◦C.
b
1,3-Cyclohexadiene transformation determined by GC–MS.

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M. Friederici et al. / Journal of Molecular Catalysis A: Chemical 376 (2013) 7–12
Table 3
Styrene hydrovinylation.
Entry
Cat
t (h)
% Conversione
% A
% B
% C
% D
TOF (h)f
1a
2b
3b
4c
5d
NP4
NP4
NP4
NP4
NP0
4
2
4
4
4
100
30.4
36.9
8.5
0
0
Traces
1.0
0.7
–
28.9
1.0
1.4
–
71.1
2.3
3.4
–
–
152
92
4
26.1
31.4
8.5
–
–
–
–
–
a
Ratio styrene/Pd(II)/AgPF6 200:1:1.
Ratio styrene/Pd(II)/AgPF6 1000:1:1.
Substrate: 4-bromostyrene. Ratio 4-bromostyrene/Pd(II)/AgPF6 200:1:1.
Ratio styrene/Pd(0) 200:1.
Conversion of styrene determined by GC using ethylbenzene as internal standard.
TOF/h calculated as the total amount of arylbutenes formed respect to Pd(II) surface.
b
c
d
e
f
Table 4
Sequential reaction: 4-bromostyrene hydrovinylation and Suzuki–Miyaura reaction.
Entry
Abstractor chloride employed
Ratio 4-bromostyrene: phenylboronic acid: K2CO3 Suzuki reaction
% 4-Bromostyrene
% A
% B
3.5
2.7
7.0
% C
1a
2a
3b
4c
AgPF6
1:1.5:2.0
1:2.0:2.5
1:2.0:2.5
1:2.0:2.5
42.1
52.8
17.0
6.0
10.1
26.7
38.0
17.0
44.3
17.8
38.0
53.0
NaBARF
NaBARF
NaBARF
24.0
a
Ratio catalyst NP4/substrate 1:100. The Suzuki reaction was performed on a mixture of toluene/H2O (4:1).
Ratio catalyst NP4/substrate 1:100. The Suzuki reaction was performed on a mixture of CH2Cl2/H2O (4:1).
Ratio catalyst NP4/substrate 1:50. The Suzuki reaction was performed on a mixture of CH2Cl2/H2O (4:1).
b
c
Scheme 2. Cross coupling reaction of 4-bromoanisole and 4-phenylboronic acid.
the voluminous ruthenium units block the approach of the reagents
to the Pd core, but degradation of the NPs affords ruthenium species
along with Pd–phosphine residues which are responsible for the
intermediate selectivity observed between NP0 and NP1. The cat-
alytic behaviour of NP3 (entries 9 and 10) is comparable with the
that described for NP2; however, the presence of the PdCl(␩3-2-
MeC3H4) unit in NP4 increases the efficiency of the catalyst (entries
11 and 12) since this metal fragment is known to provide active
Pd(0) species in solution.
To confirm the role of the allyl/Pd unit in NP4 we became
interested in comparing its catalytic efficiency with that shown
by the model compound [PdCl(PPh3)(␩3-2-MeC3H4)] in similar
experimental conditions. Thus, we found that total conversion of
4-bromoanisole was achieved after 12 h with traces of substrate
of homocoupling product. The excellent result obtained with the
use of the mononuclear Pd complex was not unexpected given the
enormous catalytic potential shown by similar molecular species
[13].
3.2. Hydrogenation of 1,3-cyclohexadiene
Palladium- and rhodium-catalyzed hydrogenation is frequently
used not only in laboratories but also in industry. For example, a
dendrimer-stabilized Pd NPs has been shown to be efficient for a
good number of unsaturated compounds [9] and more recently
Roucoux et al. studied the dehalogenation/hydrogenation reac-
tion with bromoanisole regioisomers with rhodium nanoparticles
[14]. In this paper we have analyzed the hydrogenation of 1,3-
cyclohexadiene on the basis of the NPs used (Scheme 3). The first
experiments were carried out using NP0. The reaction conditions
are listed in Table 2. After a half hour total conversion was found and
the cyclohexene/cyclohexane ratio was 6:1 under 3 bar of pressure
(entry 1).
The stability of the catalysts studied in this reaction is only mod-
erate since a gradual precipitation of solid indicates that partial
aggregation of the NPs occurs.
Scheme 3. Hydrogenation of 1,3-cyclohexadiene.

M. Friederici et al. / Journal of Molecular Catalysis A: Chemical 376 (2013) 7–12
11
Scheme 4. Hydrovinylation of styrene.
The alternative use of NP1, containing free phosphine at the
3.4. Sequential reaction
end of the chain, made worse the efficiency due to the blocking
effect of the phosphine ligands (entry 2). The highest selectivity
was observed using NP3 (entries 3 and 4). The presence of periph-
eral RhCl(cod) units largely favours the formation of cyclohexene
in front cyclohexane (cyclohexene/cyclohexane ratio 32:1). From
these results is reasonable to assume that both metal centres are
simultaneously working and that the selectivity towards cyclohex-
ene formation is mainly induced by the Rh centre. According to
the literature, the high selectivity towards formation of cyclohex-
ene is due to the stronger coordination of the 1,3-cyclohexadiene
versus cyclohexene to the rhodium fragments, preventing cyclo-
hexene binding and cyclohexane formation [15]. On the other hand,
1,3-cyclohexadiene is known to disproportionate to cyclohexene
and benzene in the presence of Pd nanoparticles [16], but in our
experiments no traces of benzene have been detected in any case.
In view of these precedents and considering that NP4 can pro-
mote separately both the hydrovinylation of 4-bromostyrene and
C
C cross coupling reactions with phenylboronic acid we designed
a sequential process combining both reactions. Thus, the reactions
were carried out consecutively in one pot using the same cata-
lyst, but adding the reagents stepwise. The process consisted of
hydrovinylation of 4-bromostyrene followed by the cross coupling
of the resulting compound A with phenylboronic acid to give B
(Scheme 5). NaBARF was selected as halide abstractor to improve
the low conversion in the hydrovinylation reaction.
The optimized reaction conditions in terms of time of reaction,
temperature and 4-bromostyrene/Pd/NaBARF ratio were obtained
after a set of experiments. The condition reactions and cat-
alytic results are summarized in Table 4. The target compound B
was obtained accompanied by a fraction of unreacted A and C,
this one resulting from coupling of the starting 4-bromostyrene
with phenylboronic acid. Note that the low conversion of 4-
bromostyrene, despite the use of NaBARF as halide abstractor,
favours the formation of C. The increase of the substrate/catalyst
ratio in the sequential reaction (Table 4, entry 4) permitted to
raise the conversion of 4-bromostyrene up to 94% although the
target compound B was formed only in 24%. It was thought, accord-
ing to the literature [13], that in the course of 4-bromostyrene
hydrovinylation active Pd(0) species are formed. These new species
3.3. Reaction catalyzed by the peripheral organometallic
fragments: styrene hydrovinylation
The hydrovinylation of styrene produces 3-phenyl-1-butene as
a main product, this process being a model reaction for the syn-
thesis of compounds with pharmacological activity, in particular
in catalytic versions of asymmetric C C coupling reactions [17]
(Scheme 4).
The catalytic data obtained in this process in presence of NP4 are
listed in Table 3. Using a styrene:Pd ratio of 200/1 the conversion
is 100%, but the 3-phenyl-1-butene isomerizes totally giving cis-
and trans-2-phenyl-2-butene (C and D) (entry 1). With a 1000/1
styrene/Pd ratio the conversion was 30.4% and the TOF 152 after
2 h (entry 2). These results compare well with those obtained using
carbosilane dendrimers decorated with allyl palladium fragment
on the periphery [18]. It should be noted that the results obtained
with the new substrate 4-bromostyrene were worse (entry 4) than
those expected in terms of conversion. Thus, the hydrovinylation
achieved was only 8.5% using a 200:1 4-bromostyrene/Pd ratio. This
is a surprising result taking into account that para-ring substituted
styrene molecules show similar reactivity than styrene in this pro-
cess [19]. It is remarkable that NP0 does not catalyze any reaction,
this fact indicating that for this process the unique catalytic centre
in NP4 is the palladium PdCl(␩3-2-MeC3H4) moiety.
would catalyze, along with the Pd core of NP4, the further C
C
Suzuki coupling. To corroborate this hypothesis, we investigated
the hydrovinylation/C C coupling process using the molecular
[PdCl(PPh3)(␩3-2-MeC3H4)] complex. In this experiment the con-
version of 4-bromostyrene was almost complete after 2 h of
hydrovinylation and 24 h of C C coupling reactions to give a mix-
ture of products. Compound A and its isomerized internal olefins
were present in 31%, the desired compound B accounted for 24%
along with a 35% of its isomerized products. Finally, 8% of com-
pound C was also present. That is, the Pd(0) species formed in the
first reaction catalyze the second one.
Coming back to the catalytic results obtained with NP4, we con-
clude that in a similar way, the hydrovinylation of 4-bromostyrene
is catalyzed by the peripheral Pd units while the second reaction
is simultaneously catalyzed by the Pd core of NP4 and the new
Pd(0) species formed by decomposition of the Pd(␩3-2-MeC3H4)
moieties.
For comparison purposes we tested the [PdCl(PPh3)(␩3-
2-MeC3H4)] complex as catalyst for the hydrovinylation of
4-bromostyrene in the same reaction conditions given in Table 3
(b). As expected, the catalytic results in homogeneous catalysis
improved those obtained with NP4 in terms of conversion (88%).
Despite the modest results achieved in this sequential process,
still far from ideal conversions with acceptable substrate/catalyst
ratio, we feel that Pd NPs functionalized with organometallic units

12
M. Friederici et al. / Journal of Molecular Catalysis A: Chemical 376 (2013) 7–12
Scheme 5. Sequential reaction.
at the periphery have an enormous potential for this class of reac-
tions in combining the high catalytic activity of Pd with great
variety of potential organometallic fragments available to graft on
the NPs core. Another interesting point to consider is the facile
preparation of these systems.
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4. Conclusions
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[11] Selected examples:
It has been shown that functionalized palladium nanoparticles
with organometallic units at the periphery can catalyze a number of
reactions using either the Pd core or the metal periphery as catalytic
centres. We applied NP4 for the sequential process, hydrovinylation
of 4-bromostyrene followed by a C C Suzuki reaction. This is the
first time that a sequential process is catalyzed by nanoparticles
displaying two different metal centres.
(a) N. Miyaura, A. Suzuki, Chem. Rev. 95 (1995) 2457–2483;
(b) M. Moreno-Man˜as, R. Pleixats, Acc. Chem. Res. 36 (2003) 638–643;
(c) L. Wu, B.-L. Li, Y.-Y. Huang, H.-F. Zhou, Y.-M. He, Q.-H. Fan, Org. Lett. 8 (2006)
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