Water-compatible gold and silver nanoparticles as catalysts for the oxidation of alkenes

Article abstract of DOI:10.1016/j.poly.2016.06.012

Water-compatible Ag/Au nanoparticles (NP) catalyze the liquid-phase oxidation of 1,1-diphenylethylene to afford benzophenone, the product of oxidative cleavage, and 1,1-diphenylepoxide. The metal nanoparticles are surface functionalized with tannic acid and/or citrate and have diameters of 10–12 nm. By proper selection of the reaction conditions, percent conversions/distributions of 85–100% of 1,1-diphenylethylene can be achieved at 90 °C using water as a solvent and TBHP (tert-butylhydroperoxide) as the co-oxidant. In addition, these nanoparticles have been further supported on functionalized silica to improve their stability and recyclability in this oxidation process. Conversions of up to 100% to benzophenone could be obtained with 1.5 mol% Au or Ag nanoparticles (10 nm) supported on functionalized silica. The supported NP could be recycled and re-used without significant catalytic activity loss for three runs.

Full text of DOI:10.1016/j.poly.2016.06.012

Polyhedron xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Water-compatible gold and silver nanoparticles as catalysts for the
oxidation of alkenes
Eugenia Fisher , Lea Kenisgberg a,1, Monica Carreira , Jacob Fernández-Gallardo , Richard Baldwin
⇑
,
María Contel
a
a,1
a
a
b,
a,c,
⇑
Department of Chemistry, Brooklyn College, The City University of New York, Brooklyn, NY 11210, United States
NanoComposix INC, 4878 Ronson Court Suite K, San Diego, CA 92111, United States
Chemistry PhD Program, The Graduate Center, The City University of New York, 365 Fifth Avenue, New York, NY 10016, United States
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Water-compatible Ag/Au nanoparticles (NP) catalyze the liquid-phase oxidation of 1,1-diphenylethylene
to afford benzophenone, the product of oxidative cleavage, and 1,1-diphenylepoxide. The metal nanopar-
ticles are surface functionalized with tannic acid and/or citrate and have diameters of 10–12 nm. By
proper selection of the reaction conditions, percent conversions/distributions of 85–100% of 1,1-dipheny-
lethylene can be achieved at 90 °C using water as a solvent and TBHP (tert-butylhydroperoxide) as the
co-oxidant. In addition, these nanoparticles have been further supported on functionalized silica
to improve their stability and recyclability in this oxidation process. Conversions of up to 100% to
benzophenone could be obtained with 1.5 mol% Au or Ag nanoparticles (10 nm) supported on function-
alized silica. The supported NP could be recycled and re-used without significant catalytic activity loss for
three runs.
Received 30 March 2016
Accepted 9 June 2016
Available online xxxx
This paper is dedicated to Emeritus
Professor Martin A. Bennett on the occasion
of his 80th birthday.
Keywords:
Oxidative cleavage
Alkenes
Ó 2016 Elsevier Ltd. All rights reserved.
Gold
Silver
Nanoparticles
1
. Introduction
During the last two decades there has been much interest in
co-workers reported the oxidative cleavage of alkenes to form
ketones and aldehydes with AuCl/neocuproine in water at 90 °C
with TBHP (tert-butylhydroperoxide) as the oxidant (Scheme 1)
[20]. Our group reported that gold(I) and especially silver(I) com-
plexes containing a tripodal bis(imidazole) thioether ligand, could
perform this oxidative cleavage in toluene [21].
finding new and less toxic metal-based oxidation catalysts, with
reports that have been compiled in a number of recent reviews
[
1–10]. Research has been focused on developing highly selective
and/or recoverable catalysts which employ oxygen or air as
oxidants. While not all new oxidation catalysts have been able to
fulfill all the above features, gold compounds and nanoparticles
have been proven as an excellent alternative to other classical
metal-based oxidation catalysts, and have been successfully used
in heterogeneous [11–16] and to a lesser extent in homogeneous
oxidations [13–18]. In contrast, oxidations of alkenes with silver
compounds in homogeneous conditions have been less explored
Liu and co-workers synthesized fully substituted butenolides
via a cascade reaction for the cleavage of a carbon–carbon triple
bond involving: (a) gold-catalyzed addition of an oxygen nucle-
ophile to the triple bonds in (Z)-enynols and, (b) subsequent oxy-
gen-assisted oxidative cleavage of the exo-enolic double bond
[22].
In the cases of the oxidative cleavage of alkenes with the Au(I)
and Ag(I) compounds [20,21], we wondered if the active catalyst
could be nanoparticles generated under reaction conditions and
[
12,19]. One relevant oxidation reaction is the oxidative cleavage
of C@C double bonds to carbonyl compounds (usually achieved
2
we set to explore the catalytic activity of Au and Ag NP in H O.
by stoichiometric oxidation or ozonation). In 2006, Shi and
We report here on the use of commercially available water-compat-
ible Ag/Au nanoparticles for the liquid-phase oxidation of
1
2
,1-diphenylethylene in H O at 90 °C with TBHP as oxidant. The
⇑
Corresponding authors at: Department of Chemistry, Brooklyn College, The City
University of New York, Brooklyn, NY 11210, United States (M. Contel).
E-mail addresses: richard.baldwin@nanocomposix.com (R. Baldwin),
oxidation products are benzophenone, product of the oxidative
cleavage, and 1,1-diphenylepoxide (Scheme 2). We also describe
catalytic studies with the nanoparticles further supported on func-
tionalized silica in order to improve the recyclability of the systems.
mariacontel@brooklyn.cuny.edu (M. Contel).
1
These authors contributed equally to the work.
http://dx.doi.org/10.1016/j.poly.2016.06.012
0
277-5387/Ó 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: E. Fisher et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.06.012

2
E. Fisher et al. / Polyhedron xxx (2016) xxx–xxx
1
13
1
AV400 ( H NMR at 400 MHz, C{ H} NMR at 100.6 MHz). Chemical
3
shifts (d) are given in ppm using CDCl as the solvent, and spectra
N
N
1
13
was recorded at 25 °C. H and C NMR resonances were measured
relative to solvent peaks with tetramethylsilane = 0 ppm. Coupling
constants J are given in hertz. Nanoparticles were characterized by
TEM and UV–Vis spectroscopy as well as ICP-MS for metal concen-
tration by nanoComposix.
(5 mol %)
AuCl (5 mol %)
R
1
H
R1
H
O
+
O
O, 90 o
C
R
2
R
3
TBHP, H
2
R2
R3
R
R
R
1
2
3
= aryl, alkyl
= aryl, alkyl, H
= H or CH
3
Scheme 1. Oxidative cleavage of alkenes with a gold(I) catalyst [20].
2.2. Catalytic oxidation procedure for unsupported nanoparticles
To 1.5 ml of deionized H
1,1-diphenylethylene) were added at room temperature. Solu-
tions of metal nanoparticles in water were subsequently added
different concentrations, see Tables 1–4 for mol per cent values).
2
O, TBHP (2.1 equiv.) and the alkene
(
2
. Experimental
(
2
.1. General procedure
The reaction mixture was stirred under reflux at 90 °C (different
times were studied, see Tables 1–4). After the reaction finished
and the flask was cooled to room temperature, the aqueous layer
was extracted with diethyl ether (3 Â 20 mL). The combined
organic layers were washed with a saturated sodium bisulfite solu-
The unsupported water suspended metal nanoparticles
employed are surface functionalized with tannic acid and/or citrate
in the case of gold and citrate surface groups in the case of silver
and have dimensions of 10–12 nm. The nanoparticles used are
available commercially from nanoComposix (products AuB10,
AuB12 and AgCB10 for gold at 10 and 12 nm and silver respec-
tively). 1,1-diphenylethylene was purchased from Sigma Aldrich.
All purchased reactants were used without further purification.
Reaction and work-up solvents were purchased from Fisher
Scientific (ACS Grade). Deuterated solvents were purchased from
Cambridge Isotope Laboratories, Inc., were kept over molecular sieves
tion (3 Â 10 mL) followed by deionized H O (3 Â 20 mL), and dried
2
over MgSO overnight. The solution was then filtered and concen-
4
1
trated under vacuum. The product obtained was analyzed by
H
NMR spectroscopy. Ketone and epoxide (Scheme 2) were observed
in different percent conversions depending on the reaction condi-
1
tions (Tables 1–4). Diagnostic signals in H NMR spectra (CDCl ):
3
1,1-diphenylethylene 5.5 ppm (2H, s, CH2), 7.6–7.3 ppm (10H, m,
6CH); benzophenone 7.8 ppm (4H, m, 4CH); 1,1-diphenylepoxide
4.84 ppm (2H, s, CH2).
(
3 Å, beads, 4–8 mesh). NMR spectra were recorded using a Bruker
Scheme 2. Oxidative cleavage of 1,1-diphenylethylene catalyzed by Au or Ag NP.
Table 1
Oxidations with 1 mol% of gold nanoparticles of size 10 nm (entries 1–4) and 12 nm (entries 5–8).a
Entry
Type of NP
[cat] mol%
Time (h)
Conversion (%)
To ketone
Std dev
To epoxide
Total
1
2
3
4
5
6
7
8
10 nm Au
10 nm Au
10 nm Au
10 nm Au
12 nm Au
12 nm Au
12 nm Au
12 nm Au
1
1
1
1
1
1
1
1
18
5
2
1
18
5
85
85
67
65
79
78
66
62
15
15
33
35
21
22
34
38
86
69
71
39
90
87
63
54
4
0
4
12
3
0
2
2
2
1
a
Reaction conditions: 0.5 mmol diphenylethylene, 1.05 mmol TBHP, H
2
O, 90 °C. Conversion determined by 1H NMR spectroscopy. Values given are an average of two
reactions. The standard deviation is given for the conversion of ketone.
Table 2
Oxidations with gold nanoparticles of size 12 nm (18 h).a
Entry
Type of NP
[cat] mol%
Time (h)
Conversion (%)
To ketone
Std dev
To epoxide
Total
1
1
2
12 nm Au
12 nm Au
12 nm Au
1
2
5
18
18
18
79
83
88
21
17
12
90
70
84
3
3
0
a
O, 90 °C. Conversion determined by 1H NMR spectroscopy. Values given are an average of two
2
Reaction conditions: 0.5 mmol diphenylethylene, 1.05 mmol TBHP, H
reactions. The standard deviation is given for the conversion of ketone.
Please cite this article in press as: E. Fisher et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.06.012

E. Fisher et al. / Polyhedron xxx (2016) xxx–xxx
3
Table 3
a
Oxidations with silver nanoparticles of size 10 nm.
Entry
Type of NP
[cat] (mol%)
Time (h)
Conversion (%)
To ketone
Std dev
To epoxide
Total
1
2
3
10 nm Ag
10 nm Ag
10 nm Ag
1
1
5
5
18
18
78
89
86
22
11
14
47
45
92
0
3
0
a
O, 90 C°. Conversion determined by 1H NMR spectroscopy. Values given are an average of two
2
Reaction conditions: 0.5 mmol diphenylethylene, 1.05 mmol TBHP, H
reactions. The standard deviation is given for the conversion of ketone.
Table 4
a
Reactions of gold nanoparticles (size 10 nm, entries 1–3 and size 12 nm entry 4) supported on APTMS functionalized silica .
Entry
Type of NP
Functionalized silica (g)
[cat] mol%
Time (h)
Conversion (%)
To ketone
Std dev
To epoxide
Total
1
2
3
4
10 nm Au
10 nm Au
10 nm Au
12 nm Au
0.25
0.25
0.375
0.25 g
1
18
18
18
18
93
100
90
7
0
10
3
98
100
95
7
0
1
3
1.5
1.5
1.5
97
97
a
O, 90 °C. Conversion determined by 1H NMR spectroscopy. Values given are an average of two
2
Reaction conditions: 0.5 mmol diphenylethylene, 1.05 mmol TBHP, H
reactions. The standard deviation is given for the conversion of ketone.
2.3. Functionalization of silica
modified. Nanoparticles were provided at a concentration of
1
mg/mL. After impregnation, the silica supported nanoparticles
Chromatographic silica was mixed with silane (Aminopropy-
were collected by filtration. The supported Au nanoparticles
formed a light purple powder while the supported Ag nanoparti-
cles formed a light brown powder. The filtrate was a clear solution
in both cases.
ltrimethoxysilane APTMS or Mercaptopropyltrimethoxysilane
MPTMS) in ethanol. 19 mmol of silane per 1 g of silica were used.
The solution was stirred for 10 min in the case of APTMS and for
2
h in the case of MPTMS, and then washed 3 times with 10 mL
of ethanol. The functionalized-silica was filtered and dried under
vacuum. The ninhydrin test was performed to check if the silica
was functionalized with the amine group (APTMS). A solution of
2
.5. Catalytic oxidation procedure for supported nanoparticles and
study of the recyclability
0
2
.2 g of ninhydrin and 50 mL of H O was prepared. One mL of
2
To the supported metal NP, 1.5 ml of deionized H O, the starting
the ninhydrin solution in water was added to 2 mg of the function-
alized silica. The mixture was boiled for 15–20 s. A blue/violet
color indicated that surface was successfully functionalized.
material (1,1-diphenylethylene), and TBHP (2.1 equiv.) were added
at room temperature. The reaction mixture was stirred under
reflux at 90 °C for the times specified in Tables 4–6. After the reac-
tion finished and the flask was cooled to room temperature, 4 mL
of ether was added to the crude reaction. The mixture was stirred
for a few minutes, and the liquid layer was decanted by pipette and
run through a fine filter. This procedure was repeated 4 times to
2.4. Procedure for supporting the nanoparticles
Ag and Au nanoparticles in water were stirred at room temper-
ature with functionalized silica overnight. The ratio of grams of
functionalized silica to milliliters of nanoparticle solution was
separate the products of the reaction. Deionized H
was subsequently added to the reaction mixture and the solid
2
O (3 Â 5 mL)
Table 5
a
Oxidations using recycled supported gold nanoparticles (10 nm) supported on APTMS functionalized silica .
Entry
Recycled NP?
Type of NP
[cat] mol%
Time (h)
Conversion (%)
To ketone
std dev
To epoxide
Total
1
2
3
No
10 nm Au
10 nm Au
10 nm Au
1.5
1.5
1.5
18
18
18
100
98
97
0
0
3
99
98
99
1
2
4
From entry 1
From entry 2
a
O, 90 °C. Conversion determined by 1H NMR spectroscopy. Values given are an average of two
2
Reaction conditions: 0.5 mmol diphenylethylene, 1.05 mmol TBHP, H
reactions. The standard deviation is given for the conversion of ketone.
Table 6
a
Reactions of silver nanoparticles (size 10 nm, 1.5 mol%) supported on silica functionalized with MPTMS and APTMS .
Entry
Recycled NP?
Type of NP
[cat] mol%
Time (h)
Conversion (%)
To ketone
Std dev
To epoxide
Total
1
2
3
No
10 nm Ag
10 nm Ag
10 nm Ag
1.5
1.5
1.5
18
18
18
100
100
100
0
0
0
91
87
75
5
2
4
From entry 1
From entry 2
a
O, 90 °C. Conversion determined by 1H NMR spectroscopy. Values given are an average of two
2
Reaction conditions: 0.5 mmol diphenylethylene, 1.05 mmol TBHP, H
reactions. The standard deviation is given for the conversion of ketone.
Please cite this article in press as: E. Fisher et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.06.012

4
E. Fisher et al. / Polyhedron xxx (2016) xxx–xxx
supported nanoparticles were filtered out. The reaction flask was
washed with diethyl ether (10 mL) to dissolve any remaining
product. The solid supported nanoparticles were then washed with
We therefore demonstrated that both Au and Ag water
suspendable nanoparticles are able to catalyze the oxidation of
1,1-diphenylethylene affording the product of oxidative cleavage
benzophenone as the major product. It should be noted that in
the report of Shi and co-workers a mechanism involving the first
step of epoxidation and a subsequent oxidation to produce car-
bonyl products was discarded since they could not detect epoxida-
tion products or perform further oxidations on specific epoxides.
[20] Gold NP of sizes 10 and 12 nm (1 mol%) are able to oxidize
1,1-diphenylethylene in 18 h affording conversions of 40–90%
depending on the time. Silver nanoparticles catalyze this oxidative
cleavage but the amount required for a conversion of 90% (18 h of
reaction) is higher (5 mol%).
deionized H
2
O (1 Â 10 mL) and diethyl ether (3 Â 10 mL). Follow-
ing the filtration process, the supported nanoparticles were dried
under vacuum for further use. The organic layer was extracted
from the combined organic and aqueous filtrate with diethyl ether
(
3 Â 20 mL). Following extraction, the organic layer was washed
with a saturated sodium bisulfite solution (3 Â 10 mL), followed
by deionized
(2 Â 10 mL). The organic layer was then
dried over MgSO overnight. The solution was filtered and poured
2
H O
4
into a pre-weighted round bottom flask and dried under high vac-
1
uum. The product obtained was weighed and analyzed by H NMR
spectroscopy. Ketone and epoxide (Scheme 2) were observed in
different percent conversions depending on the reaction conditions
While trying to recycle these nanoparticles and run subsequent
reactions we observed a dramatic decrease in the percent total
conversion. This is due to the decomposition and aggregation of
the water-suspendable nanoparticles in solution under the reac-
tion conditions. We decided to support these nanoparticles on a
solid in order to improve their catalytic activity and their recycla-
bility. Since the nanoparticles used in this study contain tannic
acid/citrate as surface groups, a procedure was developed to dis-
place these groups and coordinate the metal NP to the functional
groups on the solid support. The surface of silica materials can be
functionalized by various methods, e.g. by reaction of the silanol
groups on the silica surface with alkoxysilanes [23].
(Tables 4–6).
2.6. Transmission electron microscopy characterization
TEM images were taken on a JEOL 1010 electron microscope.
Samples of the catalysts were suspended in a 2:1 mixture of iso-
propanol and DI water. 5 L of this solution was dropped onto
l
the formvar side of a carbon coated formvar 300 mesh copper
TEM grid. The sample was then dried under vacuum and imaged
at 100 kV.
Functionalizing the silica with aminopropyltrialkoxysilanes
proved efficient for Au nanoparticles. The primary amine in the
APTMS (Fig. 1) is known to possess a high affinity for Au nanopar-
ticles and to prevent nanoparticles from aggregating. The amine
groups give rise to a positive charge on the surface of the silica
while the gold and silver nanoparticles with either a citrate or a
tannic acid surface inherently have a negative charge, thus bring-
ing the particles in close contact to the silica surface. Amines are
better ligands for noble metal surfaces than the alcohol or acid
groups in the citrate or tannic acid, thus the incorporation of ami-
nes was used to bind the metal nanoparticles to the silica surface.
We tested supported Au NP in the oxidation reaction and
observed that when the mol% of catalyst was increased from 1 to
3
. Results and discussion
We studied the use of commercially available water-stable
Ag/Au nanoparticles for the liquid-phase oxidation of 1,1-dipheny-
lethylene in H O at 90 °C with TBHP as oxidant (2.1 equivalents).
2
The oxidation products are benzophenone, product of the oxidative
cleavage, and 1,1-diphenylepoxide (Scheme 2). We started by
investigating the effect of time in the catalytic activity of 1 mol%
of unsupported 10 nm and 12 nm gold nanoparticles (Table 1).
From the results depicted in Table 1 we infer that the total con-
version and the percent conversion to ketone are directly propor-
tional to the reaction time. Increasing the reaction time resulted
in an increased total conversion and increased conversion to
ketone. We next examined how the conversion percentage was
related to the mol percent of catalyst used in the reactions for Au
NP of size 12 nm (Table 2) with a constant reaction time of 18 h.
We did not observe significant changes in terms of total conver-
sion. However, we observed that increasing the amount of catalyst
increased slightly the amount of conversion to ketone product.
Our group had reported that silver(I) complexes containing a
tripodal bis(imidazole) thioether ligand (10 mol%) could perform
this oxidative cleavage at 90 °C in toluene. We therefore examined
next the catalytic activity of silver nanoparticles of 10 nm in size
and the dependence of the catalytic reaction in terms of time
and mol percent of the catalyst (Table 3).
1
.5, the total conversion increased and the ratio to the product of
oxidative cleavage increased (see entry 2). Also, when comparing
entry 1 in Table 4 to entry 1 in Table 1, we can observe that the
activity of 10 nm Au nanoparticles improves when the Au NP were
supported on silica functionalized with APTMS. In the same man-
ner, Au NP of size 12 mm afforded the same catalytic activity while
supported on silica functionalized with APTMS affording high% of
total conversion and a 97% conversion to benzophenone. In general
the percentage of epoxide produced was considerably lower than
with unsupported Au or Ag NP (never more than 10%).
The 10 nm Au nanoparticles from entry 2, Table 4 (before and
after catalysis) were sent for characterization by TEM imaging
(Fig. 2) and we could observe that there were not considerable dif-
ferences in the samples in terms of NP size.
We examined next the recyclability of the supported Au
nanoparticles (10 mm size). The results are collected in Table 5.
In the recyclability tests we used 1.5 mol% of 10 nm Au nanoparti-
cles that were supported on 0.25 g silica functionalized with
APTMS (entry 1). After the reaction the nanoparticles were
The results in Table 3 show that as the reaction time increases
entry 1 to entry 2), the conversion to ketone and the total conver-
sion increases as well. However, as the mol% of the catalyst
increases the overall percent of conversion doubles but the ketone
and epoxide distributions do not change significantly.
(
O
O
Si
NH
2
Si
SH
O
O
O
O
3
aminopropyltrimethoxysilane (APTMS)
3 mercapto propyltrimethoxysilane (MPTMS)
Fig. 1. Two silanes (MPTMS and APTMS) used in this study to functionalize silica to make solid supports.
Please cite this article in press as: E. Fisher et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.06.012

E. Fisher et al. / Polyhedron xxx (2016) xxx–xxx
5
A
B
Fig. 2. TEM images (40Â) of Au NP (10 mm) supported on APTMS functionalized-silica before (A) and after (B) the catalytic oxidation.
recovered and used for the subsequent reactions (entries 2 and 3).
We kept the ratio of catalyst/alkene/co-oxidant constant taking
into consideration the amount of catalysts recovered. The catalytic
activity of the Au NP was preserved for three consecutive reactions.
The total conversion and the conversion to ketone only decreased
very slightly. However after the third run, the yields decreased dra-
matically and we did not study subsequent runs. This deactivation
of the catalyst may be due to the well-known effect of lixiviation of
gold (and other metals) from stabilized nanoparticles. This deacti-
vation mechanism has been previously described for gold nanopar-
ticles in oxidation reactions [24].
(either with APTMS for Au or with a 50:50 ratio mixture of MPTMS
and APTMS for Ag) allowed for the formation of more stable sys-
tems. The supported NP could be used in the oxidative cleavage
under the same reaction conditions with almost 100% conversion
to benzophenone (1.5 mol% of metal NP) and could be recycled
and reused for another two runs without major loss of catalytic
activity. These preliminary results suggest that some of the oxida-
tion processes of organic compounds with gold and silver com-
pounds may indeed be catalyzed by NP generated in situ under
reaction conditions. We will further explore the reaction
mechanisms and the scope of the oxidative cleavage with these
and similar NP systems in the future.
We also ran reactions with 10 nm Au nanoparticles supported
on silica functionalized with APTMS, using hydrogen peroxide as
the co-oxidant (see table in the SI) but the total conversion yields
were low (ranging from 35% to 42%).
Acknowledgement
While supporting silver nanoparticles on silica functionalized
with MPTMS (Fig. 1) we noticed that the filtrates always displayed
color and that after impregnation the supported nanoparticles did
not show a uniform color indicating that the impregnation proce-
dure had not proceeded in a successful way. We then functional-
ized the silica with mixtures 50% MPTMS/50% APTMS so that the
silver nanoparticles would have reduced degradation and aggrega-
tion. We reasoned that the positive charge of the amine would
attract the negative silver colloid which will subsequently be held
in place by the thiol. After impregnation, the filtrate was clear, and
the supported nanoparticles formed a powder of uniform color. We
carried the catalytic reaction and in a similar manner to the sup-
ported Au NP systems, we were able to recycle them two times
The authors are grateful for financial support from the PSC-
CUNY Research Awards, grants PSCREG-39-68 and PSCOOC-38-78
(
M.C.). M.C. is grateful to Mr. Leonard Tow and the Tow Foundation
for a Tow Professorship (2015–2017).
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.poly.2016.06.012.
References
[
[
1] W.N. Oloo, Q. Lawrence Jr., Acc. Chem. Res. 48 (2015) 2612.
2] A. Villa, N. Dimitratos, C.E. Chan-Thaw, C. Hammond, L. Prati, G.J. Hutchings,
Acc. Chem. Res. 2015 (48) (2015) 1403.
(
(
Table 6) since after the third run the yield decreased dramatically
again, most plausibly due to lixiviation of silver).
[
[
[
3] A. Parent, R. Alexander, K. Sakai, ChemSusChem 7 (2014) 2070.
4] H. Miyamura, S. Kobayashi, Acc. Chem. Res. 47 (2014) 1054.
5] Md.E. Ali, Md.M. Rahman, S.M. Sarkar, S.B. Abd Hamid, J. Nanomat. (2014).
Article ID 192038, http://dx.doi.org/10.1155/2014/192038.
6] M.G. Clerici, O.A. Kholdeeva, Liquid Phase Oxidation via Heterogeneous
Catalysis. Organic Synthesis and Industrial Applications, John Wiley & Sons,
Hoboken, 2013.
In conclusion, we have demonstrated that the oxidative cleav-
age of 1,1-diphenylethylene can be performed catalytically by
water-soluble Au (10 or 12 nm) or Ag (12 nm) NP in H O at 90 °C
and with TBHP as oxidant. The mol% of catalyst used is as low as
mol% for Au unsupported NP or 5 mol% for Ag unsupported NP
18 h reaction time). Supporting these NP in functionalized silica
2
[
1
(
[7] L. Wu, Y. Zhang, Y.-G. Ji, Curr. Org. Chem. 17 (2013) 1288.
Please cite this article in press as: E. Fisher et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.06.012

6
E. Fisher et al. / Polyhedron xxx (2016) xxx–xxx
[17] A.S.K. Hashmi, F.D. Toste, Modern Gold Catalyzed Synthesis, Wiley-VCH Verlag
[
[
8] A. Singh, L. Spiccia, Coord. Chem. Rev. 257 (2013) 2607.
9] S. Fukuzumi, Y. Yamada, J. Mater. Chem. 22 (2012) 24284.
& Co. KGaA, Weinheim, 2012. Chapter 10.
[
[
10] B. Limburg, E. Bowman, S. Bonnet, Coord. Chem. Rev. 256 (2012) 1451.
11] M.D. Hughes, Y.-J. Xu, P. Jenkins, P. McMorn, P. Landon, D.I. Enache, A.F. Carley,
G.A. Attard, G.J. Hutchings, F. King, E.H. Stitt, P. Johnston, K. Griffin, C.J. Kiely,
Nature 437 (2005) 1132.
[18] F.D. Toste, V. Michelet, Gold Catalysis: An Homogeneous Approach, Catalytic
Science Series 13, Imperial College Press, London, 2014. Chapter 2.
[19] M. Liu, H. Wang, H. Zeng, C.-J. Li, Sci. Adv. 1 (2015) e1500020.
[20] D. Xing, B. Guan, G. Cai, Z. Fang, L. Yang, Z. Shi, Org. Lett. 8 (2006) 69.
[21] F. Liu, R. Anis, E. Hwang, R. Ovalle, A. Varela-Ramírez, R.J. Aguilera, M. Contel,
Molecules 16 (2011) 6701.
[
12] S.T. Oyama, Mechanisms on Homogeneous and Heterogeneous Epoxidation
Catalysis, Elsevier, Amsterdam, Oxford, 2008.
[
[
[
[
13] A. Corma, H. Garcia, Chem. Soc. Rev. 37 (2008) 2096.
[22] Y. Liu, F. Song, S. Guo, J. Organomet. Chem. 694 (2009) 502.
[23] S.L. Westcott, S.J. Oldenburg, T.R. Lee, N.J. Halas, Langmuir 14 (1998) 5396.
[24] J. Restrepo, R. Pocar, P. Lozano, M.I. Burguete, E. Garcia-Verdugo, S.V. Luis, ACS
Catal. 5 (2015) 4743.
14] C. Della Pina, E. Falleta, L. Pratti, M. Rossi, Chem. Soc. Rev. 37 (2008) 2077.
15] C. Della Pina, E. Falleta, M. Rossi, Chem. Soc. Rev. 41 (2012) 350.
16] E. Della Pina, M. Falleta, M. Rossi, Top. Catal. 44 (2007) 325.
Please cite this article in press as: E. Fisher et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.06.012