Efficient general procedure to access a diversity of gold(0) particles and gold(I) phosphine complexes from a simple HAuCl4 source. Localization of homogeneous/heterogeneous system's interface and field-emission scanning electron microscopy study

Article abstract of DOI:10.1021/ja311258e

Soluble gold precatalysts, aimed for homogeneous catalysis, under certain conditions may form nanoparticles, which dramatically change the mechanism and initiate different chemistry. The present study addresses the question of designing gold catalysts, taking into account possible interconversions and contamination at the homogeneous/heterogeneous system's interface. It was revealed that accurate localization of boundary experimental conditions for formation of molecular gold complexes in solution versus nucleation and growth of gold particles opens new opportunities for well-known gold chemistry. Within the developed concept, a series of practical procedures was created for efficient synthesis of soluble gold complexes with various phosphine ligands (R₃P)AuCl (90-99% yield) and for preparation of different types of gold materials. The effect of the ligand on the particles growth in solution has been observed and characterized with high-resolution field-emission scanning electron microscopy (FE-SEM) study. Two unique types of nanostructured gold materials were prepared: hierarchical agglomerates and gold mirror composed of ultrafine smoothly shaped particles.

Full text of DOI:10.1021/ja311258e

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Article
Efficient general procedure to access a diversity of gold(0) particles and
gold(I) phosphine complexes from a simple HAuCl4 source. Localization
of homogeneous/heterogeneous systems interface and FE-SEM study
Sergey S. Zalesskiy, Alexander E. Sedykh, Alexey S. Kashin, and Valentine P Ananikov
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/ja311258e • Publication Date (Web): 31 Dec 2012
Downloaded from http://pubs.acs.org on January 5, 2013
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Efficient general procedure to access a diversity of gold(0) particles and
gold(I) phosphine complexes from a simple HAuCl4 source. Localization of
homogeneous/heterogeneous systems interface and FE-SEM study
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Sergey S. Zalesskiy, Alexander E. Sedykh, Alexey S. Kashin,
and Valentine P. Ananikov*
Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47,
Moscow, 119991, Russia. E-mail: val@ioc.ac.ru; Fax: +007 (499) 1355328
Abstract: Soluble gold pre-catalysts, aimed for homogeneous catalysis, under certain
conditions may form nanoparticles, which dramatically change the mechanism and initiate different
chemistry. The present study addresses the question of designing of gold catalysts taking into
account possible interconversions and contamination at the homogeneous/heterogeneous systems
interface. It was revealed that accurate localization of boundary experimental conditions for
formation of molecular gold complexes in solution vs. nucleation and growth of gold particles
opens new opportunities for well-known gold chemistry. Within the developed concept a series of
practical procedures was created for efficient synthesis of soluble gold complexes with various
phosphine ligands (R3P)AuCl (90-99% yield) and for preparation of different types of gold
materials. The effect of the ligand on the particles growth in solution has been observed and
characterized with high resolution field-emission scanning electron microscopy (FE-SEM) study.
Two unique types of nano-structured gold materials were prepared: hierarchical agglomerates and
gold mirror composed of ultrafine smoothly-shaped particles.
Keywords: gold nanoparticles, morphology control, gold(I) complexes, reactions in solution,
ligand effect.
1. INTRODUCTION
In the recent decades gold-catalyzed reactions have widely spread over the field of organic
chemistry.1,2,3,4,5,6 Numerous examples of gold-catalyzed reactions include nucleophilic additions,
cyclizations, oxidative couplings, multiple bond activation processes, hydrogenations and other
fascinating transformations.1-7,8,9,10,11,12 These examples show that gold catalysis tends to succeed in
the utmost direction of the organic synthesis. Moreover, it is a common practice now to utilize
cascade of gold-catalyzed cyclizations to yield complex frameworks of natural compounds in one
step instead of step-by-step buildup of polycyclic skeleton.1-13
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Interestingly, in spite of high activity of the catalyst and tolerance to wide range of functional
groups, gold-catalyzed reactions proved to be very sensitive to the minor changes in the catalyst
structure. Selected examples show that even small changes in the ligand, counter ion, additives or
conditions can direct the reaction to a completely different route.1-5
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A series of recent studies have shown that fundamentally different reactions and mechanisms
are accessible using soluble gold complexes and gold nanoparticles.14,15 Heterogeneous pathways
can contribute in distinct ways to activity and/or selectivity of gold-catalyzed transformations,
including alternative pathways due to decomposition of common gold salts used as catalyst
precursors towards nanoparticles.14,16 Ongoing research on transition-metal-mediated
transformations has emerged the problem of identity of active form of the catalyst in view of
possible interconversion of soluble complexes and nanoparticles in the catalyst precursor and in the
catalytic system in solution.17,18 An excellent example of the gold-catalyzed transformation through
the involvement of heterogeneous and homogeneous pathways, and the control of leaching were
published.19 The important mechanistic tools for in situ reduction of gold catalysts20 and for the
proof of homogeneous pathway with EXAFS/XANES measurements have been successfully
demonstrated.21 A valuable insight in the gas-phase ion chemistry suggested more detailed look on
the gold clusters, where a particularly strong ligand effect may be observed.22
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So far, numerous factors have pointed out that successful implementation and development of
gold catalysis in organic synthesis requires an extensive set of various gold pre-catalysts for rapid
screening. Nowadays these should include not only soluble complexes, but also nanoparticles of
various sizes and shapes.
Scheme 1. Commonly used Au(I) complexes precursors.
Widely used starting materials to prepare soluble complexes represent gold(I) stabilized by a
weak-coordinated ligand, such as Me2S (1), thiodiglycol (tdg; 2) or tetrahydrothiophene (tht; 3)
(Scheme 1). However, all three of these pre-catalysts have noticeable drawbacks. Preparation of
(Me2S)AuCl and (tht)AuCl involves handling of dimethylsulfide and tetrahydrothiophene both
having very strong odor (in fact, even used as odorants for LPG and natural gas).23 Apart from this,
(Me2S)AuCl reported to be light- and air-sensitive with limited storage period.24,25 The complex of
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gold(I) with thiodiglycole has limited stability, and therefore it has to be used without isolation.
Beyond the fact that thiodiglycole itself belongs to Schedule 2 of Chemical Weapons Convention as
a restricted compound and routine laboratory usage of thiodiglycole is limited in some countries.26
A recent example to prepare a multipurpose pre-catalyst was demonstrated by the synthesis of gold-
nitrile complex bis(2,4,6-trimethoxybenzonitrile)gold hexafluoroantimonate (4; Scheme 1) and the
application for generation of soluble gold species was shown.27
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Another challenging task for “all-from-one” catalyst kit is efficient generation of nano-
structured gold particles. Several excellent reviews cover preparation and application of
nanoparticles in details.14 However, the preparation of nano-sized gold catalyst with required
particles size and shape is not a trivial task. The majority of studies still use specific physical or
physico-chemical procedures to control the morphology of the nanoparticles during the synthesis.
Particularly, it is often necessary to use stabilizers in order to prepare gold nanoparticles (citrate-
capped, etc.).28 However, the stabilizers have to be removed from the surface of the nanoparticle for
catalytic applications.
Thus, an important direction for improvement of currently available catalyst preparation
procedures is to avoid impractical intermediate derivatives (1-3) and to get the necessary insight
into the nature of gold species. The protocols developed for the synthesis of soluble complexes were
not extended for nanoparticles, although uncontrolled formation of the nanoparticles cannot be
anticipated and recalls for possible contamination. Vice versa, the procedures for preparation of
nanoparticles were not proven to be compatible with those developed for soluble complexes. An
important aim is to prepare gold nanoparticles directly suitable for catalytic applications without the
need of intermediate stabilizers.
In the present study we describe a simple approach to access well-established gold(I)
complexes and a diversity of gold(0) particles with varying size and shape. The synthesis of the
complexes and nanoparticles was performed in high yields starting from the same HAuCl4 source as
a most available gold salt. Fascinating advantage of the developed approach is governed by
sequential procedure to access gold products of different nature. We have chosen simple and well-
known reagents to mediate formation of gold complexes and particles. The usage of these reagents
was proven in gold chemistry and here we describe the systematic study focused on detailed
characterization of soluble complexes and particles as well as addressing the question of possible
contamination at the homogeneous/heterogeneous interface.
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2. RESULTS AND DISCUSSION
2.1 Preparation of gold particles by reduction of HAuCl4 with N2H4·2HCl, NaBH4, and
hydroquinone.
On the first step we identified what gold complexes or nanoparticles can be obtained by
reduction of HAuCl4 using a set of well-known reducing agents - N2H4·2HCl, NaBH4, and
hydroquinone. The milestone study of G. Schmid and co-workers have demonstrated that Au55
clusters can be readily formed by reduction of Au(III) salt with B2H6.29 Formation of large metal
clusters is an important prerequisite for homogeneous (soluble mononuclear molecular species) and
heterogeneous (insoluble metal particles) systems boundary in solution.30
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Reduction of HAuCl4 in solution is known to proceed smoothly and, in the absence of a
stabilizer, it results in the formation of insoluble precipitate. In the case of sodium borohydride the
reaction at room temperature was completed immediately and yielded a black precipitate without
noticeable amount of metal mirror on the walls of the reaction vessel.31 Field-emission scanning
electron microscopy (FE-SEM) study showed that the precipitate consisted of non-uniformly
shaped particles in a 100 - 400 nm size with the individual particles been arranged in a well
developed porous network (Figure 1A and 1B).
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Figure 1. FE-SEM images of the metal particles formed in the reduction of HAuCl4 by NaBH4 (A
and B), N2H4·2HCl (C and D), and hydroquinone (E and F); microscopy characterization of
precipitates at ×10000 (A), ×50000 (B), ×5000 (C), ×3000 (E) magnifications, and gold mirrors on
the walls of the reaction vessel at ×5000 (D, F) magnification (corresponding µm and nm scale bars
shown on each image).
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Reduction with hydrazine dihydrochloride was completed in 5 min after addition of the
reductant (somewhat slower compared to NaBH4 reduction) and resulted in formation of clear
colorless solution with dark brown precipitate and gold mirror on the walls of the tube. Both the
precipitate and the mirror were subject to FE-SEM analysis and showed almost the same
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morphology and particle size (Figure 1C and 1D). The particles on the glass surface (mirror) were
spherically-shaped and were not aggregated with boundaries between separate particles clearly
visible. The particles from precipitate had the same size distribution and shape but due to more
dense packing formed an agglomerated structure (Figure 1C). The diameter of the particles in both
cases was about 300-700 nm.
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At the first sight, the reaction of HAuCl4 with hydroquinone proceeded very similar to the one
with N2H4·2HCl but the amount of the formed gold mirror was significantly lower. The mirror
consisted of loosely arranged metal particles (Figure 1F): the major fraction consisted of the
particles of nearly spherical shape and a smaller fraction consisted of rods and polygonal-shaped
particles. However, FE-SEM analysis of the precipitate revealed surprisingly complex 3D structure
(Figure 1E). The bigger particles (about 1.5 µm in size) were arranged in a complex agglomerated
porous three-dimensional framework. As shown on the high magnification image each of the
particles in turn had a highly-developed surface with multiple spikes, ledges and pits (Figure 2).
Such hierarchy of particles was previously described for lanthanide salts,32 CdS33 and Ni-Al binary
systems,34 however, to the best of our knowledge the formation on such a framework for gold
materials based on a simple preparation procedure has not been described. These types of structures
may be attractive for heterogeneous catalysis because larger surface area and various types of
corners and edges become available for the reaction with substrate.
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Figure 2. High magnification FE-SEM image (×20000) showing the morphology of hierarchal gold
particles formed upon reduction of HAuCl4 with hydroquinone.
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2.2 Morphology change in the presence of PPh3.
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On the next step we studied the influence of phosphine ligands to check if it would prevent
precipitation of gold metal and favor (Ph3P)Au(I) complex formation. It is well known that the
(triphenylphosphine)gold chloride complex can be simply prepared by reaction of HAuCl4 with
excess PPh3, so that an excess of PPh3 partially serves as reducing agent.35 This approach is rather
simple and straightforward, however it requires a large excess of phosphine (ca. 2-5 equiv.) to be
used.
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With sodium borohydride the reaction yielded insoluble dark precipitate without gold mirror
formation. Low magnification analysis showed structural array of gold material (Figure 3A). Higher
magnification FE-SEM revealed ultrafine structure consisting of small sized particles of 5-10 nm in
diameter (Figure 3B). It is evident that PPh3 in this case plays an important role to control
nanoparticles growth process (cf. Figure 1B and Figure 3B). The nature of this process may be
connected to the metal clusters generation and leaching involving nanoparticles16,29,30 – molecules
of triphenylphosphine coordinate to initially formed smaller clusters and nanoparticles stabilizing
them in solution and effecting the rate of their growth.
Reactions with hydrazine dihydrochloride and hydroquinone yielded both the precipitate and
the gold mirror on the walls of the tube. In case of reduction with hydrazine dihydrochloride
characteristic spherical particles with a diameter of about 200-500 nm were formed (Figures 3C and
3D). High magnification FE-SEM showed some distortions from the spherical geometry and the
presence of round-shaped corners. The same structural subunit was found in the precipitate and in
the mirror, however with a different degree of aggregation (cf. Figures 3C and 3D).
FE-SEM study of the precipitate formed during the reaction of HAuCl4 and hydroquinone in
presence of triphenylphosphine revealed a complex 3D framework with particles sizes being
significantly lower compared to the experiment without phosphine ligand. The presence of PPh3
resulted in ca. twofold decrease in the particles size (Figure 3E). In this case the structure of the
gold mirror was principally different as compared to the precipitate (cf. Figures 3E and 3F). The
metal particles grown on the glass surface had almost the same size and morphology as the ones
formed in the absence of phosphine (Figures 3F and 2F). Presumably, addition of
triphenylphosphine changed the growth pattern of metal particles in solution to preserve a more fine
structure in the isolated product, however the phosphine has little effect (if any) on the morphology
of metal mirror.
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Figure 3. FE-SEM images of the metal particles formed in the reduction of HAuCl4 in the presence
of PPh3 using NaBH4 (A and B), N2H4·2HCl (C and D), and hydroquinone (E and F); microscopy
characterization of precipitates at ×20000 (A), ×300000 (B), ×10000 (C, E) magnifications and gold
mirrors at ×10000 (D, F) and ×50000 (insert on D) magnifications with corresponding µm and nm
scale bars shown on each image.
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2.3 Preparation of soluble (R3P)AuCl complexes by tuning the reducing agent.
In spite of our attempts, none of the reducing agents discussed above were suitable for the
synthesis of gold(I) complexes because to a greater or lesser extent each of them lead to formation
of Au nanoparticles. Contamination of soluble metal complexes with nanoparticles can seriously
obscure application in catalysis and lead to ambiguous mechanistic picture.17 Therefore we have
studied mild sulfur-based reductants and investigated whether it is possible to prepare a number of
gold(I) phosphine complexes in one step starting from HAuCl4 without the contamination with
nanoparticles. Practically inconvenient sulfur compounds (see Introduction) have been excluded
from the synthetic procedure.
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Modification of the known procedure of reduction with sulfides has shown that a number of
gold(I) complexes with various phosphine ligands can be accessed in excellent yields (90-99%)
directly from HAuCl4 (eq. 1, Scheme 2).36 Addition of Pr2S to HAuCl4 in ethanol led to colorless
clear solution, which indicated reduction of HAuCl4 and formation of soluble Pr2S-gold complex
(10 min at 40oC). Subsequent addition of R3P ligand to the reaction mixtures led to formation of the
target (R3P)AuCl complex (1 h at 40oC). The procedure can be carried out one pot without the need
of separation and purification of intermediate gold(I) sulfide complex. Among the studied disulfides
the best yields were obtained using Pr2S,37 which was selected as a reagent of choice (commercially
available and easy to handle compound with weak odor).
Scheme 2. (1) - Synthesis of (R3P)AuCl complexes from HAuCl4 using one-pot procedure
developed in the present study (90-99% yield for the shown ligands); (2) and (3) - comparison with
the literature methods.
Developed procedure is much more efficient as compared to the one pot reduction of HAuCl4
with an excess of phosphine reported in the literature (eq. 2, Scheme 2). The literature procedure
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gave good yield only for Ph3P and poor yields for other ligands (34 - 69%), while only traces of
product were detected for CyPh2P.36 Also for cost-efficiency reasons synthesis of the complexes by
reduction with an excess of biphenylphosphine and phosphite ligands is impractical. Another well-
known method is based on the substitution of R2S by a phosphine ligand, which proceeds with high
yields (eq. 3, Scheme 2). However, starting with HAuCl4 it is a two-step procedure involving
preparation of (R2S)AuCl.38 Both sulfur compounds (R2S = Me2S and tht) used on the first step are
not as easy to handle as Pr2S utilized in the present study. For the in situ reduction the procedure
using thiodiglycol as a reducing agent has been reported with the yield of 94% for {(2,4-(t-
Bu)2C6H3O)3P}AuCl,39 84% for (Ph3P)AuCl, 49% for (o-Tol)3PAuCl, 69% for {Cy2(o-
biphenyl)P}AuCl and 43% for {(t-Bu)2(o-biphenyl)P}AuCl.40
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One-pot HAuCl4 reduction/complexation developed in the present study is a general
procedure and all tested ligands gave high yields (90-99%) and excellent product purity (eq. 1,
Scheme 2). The complexes were obtained in the pure form without any dedicated purification steps.
No signs of contamination of the product with corresponding phosphine oxides were observed (in
contrast to reduction with an excess of PR3). Even with rather complex and sterically demanding
biphenylphosphine ligands (Buchwald-type) the proposed method results in formation of the target
complexes in one step with high yield using only one equivalent of the phosphine. Challenging
issue concerns synthesis of gold(I) complexes with electron-poor phosphite ligand possessing weak
coordination ability, where the developed procedure has also shown very good performance (eq. 1,
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Scheme 2).36 Structure and purity of the synthesized gold complexes were established with H, C
and 31P NMR, and high resolution ESI-MS in solution (see Experimental part and Supporting
information).
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Figure 4. High magnification FE-SEM images of the metal particles formed in the reduction of
(Ph3P)AuCl in solution with NaBH4: (A) - precipitate (×50000) and (B) – metal mirror (×200000)
with corresponding nm scale bars shown on each image.
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2.4 Synthesis of ultrafine nanoparticles by reduction of tightly bound gold-phosphine
complex.
It was of much interest to track the tendency of phosphine ligand to control nanoparticles
formation, thus we have carried out the reaction of (Ph3P)AuCl complex with the studied reducing
agents. No reaction took place with hydrazine dihydrochloride and hydroquinone, however
reduction with NaBH4 led to formation of metal mirror and small amount of precipitate. As
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evidenced by FE-SEM, the particles of this precipitate (Figure 4A) had significantly different
morphology compared to those discussed earlier (Figure 1A). The aggregates had a diameter of 20-
150 of nm, while the diameter of the small particles was in the range of 5 - 10 nm in diameter
(Figure 4A).
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The most interesting finding was the microscopic structure of gold mirror – in fact it consisted
of very small nanoparticles with the mean diameter about 5 nm. The borders between individual
particles were clearly visible with negligible degree of aggregation (Figure 4B). In addition to
application in catalysis, such thin metal films consisting of perfectly shaped particles are in demand
for material science studies41 and development of new nanoelectronic devices.42 Synthetic
procedures reported so far to obtain such structures were based on complicated techniques including
galvanic displacement reactions,43 electrodeposition,44 electrohydrodynamic atomization.45 The
procedure described in the present study provides simple and straightforward approach to this class
of gold materials.
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2.5 “All-from-one” gold complexes/particles kit.
In the present study we have developed a series of practically useful procedures to access
various gold species starting from HAuCl4 (Scheme 3). An important issue was to localize the
interface between soluble molecular complexes of gold and insoluble gold particles. Large and
medium-sized particles were prepared by reaction in solution carried out in the presence or in the
absence of ligand. Nanoparticles of gold were synthesized by stabilization of molecular complexes
with PPh3 prior to the self-assembly procedure. From the other hand, individual molecular
complexes were prepared in high yields without nanoparticles contamination. Best results were
achieved using Pr2S as reducing and complexation agent. Therefore, the approach was developed to
access gold complexes and particles to cover homogeneous and heterogeneous chemical systems
(Scheme 3).
The scope and structural summary of the developed approach are shown in Table 1, with the
highlight on preparation of a variety of soluble gold complexes and particles. Current study
constitutes an attempt to develop so-called “all-from-one” gold kit for application in the fields of
homogeneous/heterogeneous catalysis as well as in solid state chemistry of gold. The approach
should be especially useful for screening procedures, where a diversity of metal complexes and
materials should be rapidly generated from a single source.
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Scheme 3. A summary of possible pathways for the preparation of gold materials from the known
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“platform chemicals” HAuCl4 and R3PAuCl ([Red] = N2H4·2HCl, NaBH4 or hydroquinone).
The study of HAuCl4 reduction with sulfides allowed us to develop easy to use and efficient
method for the synthesis of various (R3P)AuCl complexes which are valuable pre-catalysts for gold-
mediated reactions. The application of developed method was successfully tested on various
phosphine ligands. The complexes were prepared in excellent yields under verified conditions that
avoid contamination by metal nanoparticles.
A diversity of micro-sized and nano-sized gold particles was prepared using well-known
reducing agents (Table 1). Gold particles were characterized in details by FE-SEM study. Gold
particles formed as a precipitate and as metal mirror on the glass surface can be easily separated
from each other and potentially used in various catalytic reactions. Due to noticeable difference in
size and morphology of the particles assembled on the glass surface and in solution one should
expect varying chemical and catalytic properties.
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Table 1. Preparation of molecular complexes, particles and metal mirrors starting from HAuCl4.a
Products
Initial
Reagents/
№
1
Molecular
compound
Conditions
Particles
Metal mirror
compounds
Particles with diameter of 100-400 nm
arranged in a well developed porous network
(Figures 1A, 1B).
HAuCl4
HAuCl4
NaBH4
-
-
-
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Slightly distorted spheres with
diameter of 500-700 nm (Figure
1D).
Slightly distorted spheres with diameter of 300-
600 nm (Figure 1C).
2
N2H4·2HCl
Polygonal particles with smoothed edges
(diameter of 100-300 nm) incorporated in the
sphere-like structures with diameter of 1.5 ±
0.2 µm (Figures 1E, 2).
Polygonal
particles
with
3
HAuCl4
Hydroquinone
NaBH4+ PPh3
-
smoothed edges (diameter of
100-400 nm); (Figure 1F).
Structural array of gold material consisting of
ultrafine subunits with diameter of 5 – 10 nm;
(Figures 3A, 3B).
4
5
HAuCl4
HAuCl4
-
-
-
Slightly distorted spheres with
diameter of 200 - 300 nm
(Figure 3D).
N2H4·2HCl +
PPh3
Slightly distorted spheres with diameter of 200-
500 nm (Figures 3C).
Polygonal particles with smoothed edges
(diameter of 50-100 nm) incorporated in the
sphere-like structures with diameter of 0.7 ±
0.1 µm (Figure 3E).
Polygonal
particles
with
Hydroquinone +
PPh3
6
HAuCl4
-
-
smoothed edges and diameter of
200-300 nm (Figure 3F).
Individual spherical particles
with diameter of 5 - 10 nm
(Figure 4B).
Highly aggregated particles with a small
subunit of 5 - 10 nm (Figure 4A).
7
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(Ph3P)AuCl
HAuCl4
NaBH4
(R3P)AuCl
(90-99%)
Pr2S + PR3
-
-
a In case of non-spherical shape the reported size of the particles corresponds to Feret diameter.
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3. CONCLUSIONS
We have shown that a number of challenging gold structures can be formed by reduction of
HAuCl4 under controlled conditions. An interesting effect of triphenylphosphine stabilization of
nanoparticles upon formation was observed. This allowed us to tune the size and shape of the particles
simply by addition of a ligand. Very interesting results came out from the reaction of gold
tetrachloroaurate with hydroquinone and reduction of (Ph3P)AuCl in solution with NaBH4. These
reactions proceeded smoothly at room temperature yielding the formation of agglomerated porous
three-dimensional framework consisting of nano-sized gold subunits (Figures 2, 3F) and gold mirror
composed of ultrafine smoothly-shaped particles (Figure 4B). Surprisingly, the unique nano-structured
organization of gold particles in demand for material science applications and catalysis14,41,42 became
accessible via such a simple and practical procedure.
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For homogeneous catalytic systems, gold(I) phosphine complexes represent one of the most used
types of catalysts and pre-catalysts in various transformations, including their cationic derivatives,
which are easily made by treatment with an equivalent of silver salt. Practical application of (R3P)AuCl
complexes prepared in high yield in the present study (Scheme 2) has demonstrated unquestionable
utility.46 Complexes of gold(I) with bulky biphenylphosphines were explored in several catalytic
transformations and revealed amazing ability of ligand effect tuning.40a,47,48 Synthesis and isolation of
stable complexes with electron-poor ligands is another challenging goal achieved using the developed
procedure. Gold(I) complex with phosphite ligand give rise to most electrophilic metal species and new
types of catalytic applications.40a,48,49,50 Thus, a general synthetic procedure was developed for the
preparation of a series of the key gold(I) complexes in demand for homogeneous catalysis.
It should be pointed out that we focused our attention on simple reducing agents and efficient
procedures with proven utility in transition metal chemistry. Individual reactions of these types under
different conditions and varying target applications were employed in gold chemistry for many years.
However, detailed study and comprehensive FE-SEM characterization in the solid state coupled with
NMR in solution reported in the present article have clearly shown that the potential of these practically
simple procedures remains largely unexplored. We anticipate further research in the area of tuning the
properties of gold complexes and particles at molecular level and finding new chemical applications.
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3. EXPERIMENTAL
3.1 General considerations.
NMR spectra were recorded at on Bruker DRX-500 and Avance-600 spectrometers with working
frequencies 500.1 and 600.1 MHz for 1H, respectively. Chemical shifts are reported in ppm relative to
residual solvent signal for 1H and 13C, and external 85 % H3PO4/H2O for 31P.
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High resolution mass spectra (HR MS) were measured on a Bruker micrOTOF II and Maxis
instrument using electrospray ionization (ESI).51 The measurements were performed in a positive ion
mode (interface capillary voltage – 4500 V); mass range from m/z 50 to m/z 3000 Da; external or
internal calibration was performed with Electrospray Calibrant Solution (Fluka). A syringe injection
was used for solutions in acetonitrile (flow rate 3 µL/min). Nitrogen was applied as a dry gas; interface
temperature was set to 180°C.
For the FE-SEM measurements samples were mounted on a 25 mm aluminum specimen stub and
fixed by conductive silver paint. The observations were carried out using Hitachi SU8000 field-
emission scanning electron microscope (FE-SEM). Images were acquired in secondary electron mode
at 10 kV accelerating voltage and at the working distance of 8-10 mm. For the samples of gold mirror
obtained from the HAuCl4 metal coating with a thin film of chromium was performed using magnetron
sputtering method as described earlier.52 Morphology of the coated samples was studied adjusted for
the metal coating surface effects.
3.2 Reaction of HAuCl4 with reductants.
The solution of the reductant (0.08 mmol) in ethanol (1 mL) was added to a solution of
HAuCl4·4H2O (0.005 g, 0.0126 mmol) in ethanol (1 mL) at room temperature (25 °C).53
NaBH4. After addition of the reductant the solution instantly became black and gas evolution
was observed. Black solid precipitate was washed with 4 mL of dichloromethane, 2 mL of ethanol, 2
mL of hexanes, 2 mL of water, and 2 mL of acetone.
N2H4·2HCl. Reaction was completed in 5 min after addition of the reductant, and the solution
became colorless. Brown solid precipitate and the gold mirror from the walls of the reaction vessel
were washed with 2 mL of dichloromethane, 2 mL of ethanol, 2 mL of water, and 2 mL of acetone.
Hydroquinone. Brown suspension was formed in 5 min after addition of the reductant. The solid
and the gold mirror from the walls of the reaction vessel were washed with 2 mL of dichloromethane, 2
mL of ethanol, and 2 mL of acetone.
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3.3 Reaction of HAuCl4 with reductants in the presence of PPh3.
The solution of the reductant (0.08 mmol) and PPh3 (0.0033 g, 0.0126 mmol) in ethanol (1 mL)
was added to a solution of HAuCl4·4H2O (0.005 g, 0.0126 mmol) in ethanol (1 mL).
NaBH4. After addition of the reductant the solution instantly became black and gas evolution
was observed. Black solid precipitate was washed with 4 mL of dichloromethane, 2 mL of ethanol, 2
mL of hexanes, 2 mL of water, and 2 mL of acetone.
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N2H4·2HCl. The reaction was completed in 5 min after addition of the reductant, and the solution
became colorless. Brown solid precipitate was washed with 2 mL of dichloromethane, 2 mL of ethanol,
2 mL of water, and 2 mL of acetone.
Hydroquinone. Brown suspension was formed in 5 min after addition of the reductant and the
solution became dark. Solid precipitate was washed with 2 mL of dichloromethane, 2 mL of ethanol,
and 2 mL of acetone.
3.4 Reaction of (Ph3P)AuCl with sodium borohydride.
The solution of NaBH4 (0.0038 g, 0.10 mmol) in ethanol (1.5 mL) was added to the solution of
(Ph3P)AuCl (0.005 g, 0.01 mmol) in dichloromethane (0.5 mL). After addition of the reductant the
solution instantly became black and gas evolution was observed. Black solid and the internal walls of
the reaction vessel were washed with 4 mL of ethanol, 4 mL of dichloromethane, 4 mL of acetone and
4 mL of water.
3.5 General procedure for the developed one-pot synthesis of Au(I) complexes from HAuCl4
by reduction with Pr2S.
Pr2S (0.080 mL, 0.568 mmol) was added to the solution of HAuCl4·4H2O (0.100 g, 0.243 mmol)
in ethanol (2 mL). After 10 min of stirring at 40 °C the solution became colorless. The solution of
corresponding phosphine or phosphite ligand (0.2673 mmol) in ethanol (2 mL) was added to the
reaction mixture and the formation of precipitate was initiated upon addition. Stirring was continued
for 60 min at 40 °C followed by cooling the reaction mixture to room temperature and evaporation to a
5-10 % of initial volume under reduced pressure. The white precipitate was separated by centrifugation
(3500 rpm; 2 min) and washed with 1.5 mL of ethanol and 7.5 ml of hexanes (in the centrifuge tube).
After that it was washed with 0.5 mL of ethanol and 4.5 ml of hexanes (in the centrifuge tube). The
product was isolated by centrifugation (3500 rpm; 2 min) and redissolved in DCM. The evaporation of
the solvent gave pure products with the isolated yeild 90-90% for the studied ligands (eq. 1,
Scheme 2).36 The complexes were characterized by NMR and ESI-MS.
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ACKNOWLEDGEMENTS
The work was supported in part by the Russian Foundation for Basic Research (Projects No. 12-
03-33127, 12-03-31270, 12-03-31512), grant MD-4969.2012.3, the Ministry of education and science
of Russian Federation (Project 8453) and Programs of Division of Chemistry and Material Sciences of
RAS.
SUPPORTING INFORMATION.
Optimization of the reaction conditions, NMR spectra and ESI-MS spectra of the synthesized
gold complexes.
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REFERENCES
1 (a) Hashmi, A.S.K.; Hutchings, G.J. Angew Chem. Int. Ed. 2006, 45, 7896. (b) Hashmi, A.S.K. Chem.
Rev 2007, 107, 3180.
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
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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
58
59
60
2 (a) Jiménez-Núñez, E.; Echavarren, A.M. Chem. Commun. 2007, 333. (b) Echavarren, A.M.;
Jiménez-Núñez, E. Top. Catal. 2010, 53, 924.
3 (a) Gorin, D. J.; Toste, F. D. Nature 2007, 446, 395. (b) Shapiro, N. D.; Toste, F. D. Synlett 2010,
675. (c) Gorin, D.J.; Sherry, B.D.; Toste, F.D. Chem. Rev. 2008, 108, 3351.
4 (a) Fürstner, A. Chem. Soc. Rev. 2009, 38, 3208. (b) Fürstner, A.; Davies, P.W. Angew. Chem. Int.
Ed. 2007, 46, 3410.
5 Corma, A.; Leyva-Pérez, A.; Sabater, M. J. Chem. Rev. 2011, 111, 1657.
6 (a) Dyker, G. Angew. Chem., Int. Ed. 2000, 39, 4237; (b) Li, Z.; Brouwer, C.; He, C. Chem. Rev.
2008, 108, 3239. (c) Arcadi, A. Chem. Rev. 2008, 108, 3266. (d) Zhang, L.; Sun, J.; Kozmin, S. A.
Adv. Synth. Catal. 2006, 348, 2271. (e) Shen, H. C. Tetrahedron 2008, 64, 7847. (f) Skouta, R.; Li, C.-
J. Tetrahedron 2008, 64, 4917. (g) Sengupta, S.; Shi, X. ChemCatChem 2010, 2, 609. (h) Aubert,
C.; Fensterbank, L.; Garcia, P.; Malacria, M.; Simonneau, A. Chem. Rev. 2011, 111, 1954. (i)
Widenhoefer, R. A. Chem. Eur. J. 2008, 14, 5382.
7
(a) Hopkinson, M.N.; Gee, A.D.; Gouverneur, V. Chem. Eur. J. 2011, 17, 8248. (b) Wegner, H.A.
Chimia 2009, 63, 44. (c) Brenzovich, W.E.; Brazeau, J.-F. Jr.; Toste, F.D. Org. Lett. 2010, 12, 4728.
8 (a) Corma, A.; Serna, P. Science 2006, 313, 332. (b) González-Arellano, C.; Corma, A.; Iglesias, M.;
Sánchez F. Chem. Commun. 2005, 3451.
9 (a) Huguet, N.; Echavarren, A.M. Top. Organomet. Chem. 2013, 43, 291. (b) Hashmi, A.S.K.; Bührle,
M. Aldrichimica Acta 2010, 43, 27.
10
(a) Jiménez-Núñez, E.; Echavarren, A.M. Chem. Rev. 2008, 108, 3326. (b) Hashmi, A.S.K.;
Rudolph, M. Chem. Soc. Rev. 2008, 37, 1766.
11 (a) Dudnik, A.S.; Chernyak, N.; Gevorgyan, V. Aldrichim. Acta 2010, 43, 37. (b) Dudnik, A.S.;
Schwier, T.; Gevorgyan, V. Org. Lett. 2008, 10, 1465. (c) Dudnik, A. S.; Xia, Y.; Li, Y.; Gevorgyan,
V. J. Am. Chem. Soc. 2010, 132, 7645. (d) Shiroodi, K. R.; Dudnik, A. S.; Gevorgyan, V. J. Am. Chem.
Soc. 2012, 134, 6928.
12 (a) Zhao, R.; Ji, D.; Lv, G.; Qian, G.; Yan, L.; Wang, X.; Suo, J. Chem. Commun. 2004, 904; (b) Xu,
Y.-J.; Landon, P.; Enache, D.; Carley, A.F.; Roberts, M.W.; Hutchings, G.J. Catal. Lett. 2005, 101,
175; (c) Abbiati, G.; Arcadi, A.; Bianchi, G.; Di Giuseppe, S.; Marinelli, F.; Rossi, E. J. Org. Chem.
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2003, 68, 6959; (d) Corma, A.; Serna, P.; García, H. J. Am. Chem. Soc 2007, 129, 6358. (e) Zhang, Y.;
Cui, X.; Shi, F.; Deng, Y. Chem. Rev. 2012, 112, 2467. (f) Davies, P.W.; Martin, N. Org. Lett. 2009,
11, 2293.
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13 See also activation of pure acetylenic hydrocarbons without heteroatoms: (a) Hashmi, A. S. K.;
Braun, I.; Nösel, P.; Schädlich, J.; Wieteck, M.; Rudolph, M.; Rominger, F. Angew. Chem. Int. Ed.
2012, 51, 4456. (b) Hashmi, A. S. K.; Braun, I.; Rudolph, M.; Rominger, F. Organometallics 2012, 31,
644. (c) Hashmi, A. S. K.; Wieteck, M.; Braun, I.; Nösel, P.; Jongbloed, L.; Rudolph, M.; Rominger, F.
Adv. Synth. Catal. 2012, 354, 555.
14 Selected reviews on gold nano-particles in catalysis: (a) Gong, J. Chem. Rev. 2012, 112, 2987. (b)
Zhang, Y.; Cui, X.; Shi, F.; Deng, Y. Chem. Rev. 2011, 112, 2467. (c) Corma, A.; Garcia, H. Chem.
Soc. Rev. 2008, 37, 2096. (d) Astruc, D.; Lu, F.; Aranzaes, J.R. Angew. Chem. Int. Ed. 2005, 44, 7852.
(e) Daniel, M.-C.; Astruc, D. Chem. Rev. 2003, 104, 293 (f) Haruta, M. Cattech 2002, 6, 102. (g)
Haruta, M.; Daté, M. Appl. Cat. A: Gen. 2001, 222, 427. (h) see also ref. 1.
15 (a) Corma, A.; Juárez., R.; Boronat, M.; Sánchez, F.; Iglesias, M.; García, H. Chem. Commun. 2011,
47, 1446. (b) Lauterbach, T.; Livendahl, M.; Rosellón, A.; Espinet, P.; Echavarren, A.M. Org. Lett.
2010, 12, 3006. (c) Han, J.; Liu, Y.; Guo, R. J. Am. Chem. Soc. 2009, 131, 2060. (d) García-Mota M.;
Cabello, N.; Maseras, F.; Echavarren, A.M.; Pérez-Ramírez, J.; Lopez, N. Chem. Phys. Chem. 2008, 9,
1624;
16 (a) Kyriakou, G.; Beaumont, S.K.; Humphrey, S.M.; Antonetti, C.; Lambert, R.M. Chem. Cat. Chem.
2010, 2, 1444. (b) Kanuru, V.K.; Kyriakou, G.; Beaumont, S.M.; Papageorgiou, A.C.; Watson, D.J.;
Lambert, R.M. J. Am. Chem. Soc. 2010, 132, 8081. (c) Peixoto de Almeida, M.; Carabineiro, S.A.C.
Chem. Cat. Chem. 2012, 4, 18. (d) Beaumont, S.K.; Kyriakou, G.; Lambert, R.M. J. Am. Chem. Soc.
2010, 132, 12246.
17
(a) Zalesskiy, S.S.; Ananikov, V.P. Organometallics 2012, 31, 2302. (b) Ananikov, V.P.; Orlov,
N.V.; Zalesskiy, S.S.; Beletskaya, I.P.; Khrustalev, V.N.; Morokuma, K.; Musaev, D.G. J. Am. Chem.
Soc. 2012, 134, 6637. (c) Ananikov, V.P.; Beletskaya, I.P. Organometallics 2012, 31, 1595.
18 Somorjai, G. A.; Li Y. Introduction to surface chemistry and catalysis. Second addition. 2010, John
Wiley & Sons, Inc. Hoboken.
19 Carrettin, S.; Blanco, M. C.; Corma, A.; Hashmi, A. S. K. Adv. Synth. Catal. 2006, 348, 1283.
20 Hashmi, A. S. K.; Blanco, M. C.; Fischer, D.; Bats, J. W. Eur. J. Org. Chem. 2006, 1387.
21 Hashmi, A. S. K.; Lothschütz, C.; Ackermann, M.; Doepp, R.; Anantharaman, S.; Marchetti, B.;
Bertagnolli, H.; Rominger, F. Chem. Eur. J. 2010, 16, 8012.
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22 Robinson, P. S. D.; Khairallah, G. N.; da Silva, G.; Lioe, H.; O’Hair, R. A. J. Angew. Chem. Int. Ed.
2012, 51, 3812.
23 (a) Pollock, H.B. US Pat. 2625518. (b) de Wild, P.J.; Nyqvist, R.G.; de Bruijn, F.A.; Stobbe, E.R. J.
Power Sources 2006, 159, 995.
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24 Fortman, G.C.; Nolan, S.P. Organometallics 2010, 29, 4579.
25 See also oxidation of thioesters by Au(III) complexes: Boring, E.; Geletii, Y. V.; Hill, C. L. J. Am.
Chem. Soc. 2001, 123, 1625.
26
Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical
Weapons and on their Destruction, Paris - New York, 1993. http://www.opcw.org/chemical-weapons-
convention/annex-on-chemicals/b-schedules-of-chemicals/schedule-2/
27
Raducan, M.; Rodríguez-Escrich, C.; Cambeiro, X.C.; Escudero-Adán, E.C.; Pericàs, M.A.;
Echavarren, A.M. Chem. Commun. 2011, 47, 4893.
28 Some representative studies for the preparation of gold nanoparticles using stabilizers, reduction with
NaBH4 and hydroquinone: (a) Zhang, Z.; Wu, Y. Langmuir 2011, 27, 9834. (b) Zhang, Z.; Wu, Y.
Langmuir 2010, 26, 9214. (c) Bakr, O.M.; Wunsch, B.H.; Stellacci, F. Chem. Mater. 2006, 18, 3297.
(d) Li, J.; Wu, J.; Zhang, X.; Liu, Y.; Zhou, D.; Sun, H.; Zhang, H.; Yang, B. J. Phys Chem. C 2011,
115, 3630. (e) Lu, L.; Ai, K.; Ozaki, Y. Langmuir 2008, 24, 1058. (f) Wang, X.; Yang, D.-P.; Huang,
P.; Li, M.; Li, C.; Chen, D.; Cui, D. Nanoscale 2012, 4, 7766. (g) Jana, N.R. Small 2005, 1, 875. (h)
Martra, G.; Prati, L.; Manfredotti, C.; Biella, S.; Rossi, M.; Coluccia, S. J. Phys. Chem. B 2003, 107,
5453. (i) Liu, G.-K.; Hu, J.; Zheng, P.-C.; Shen, G.-L.; Jiang, J.-H.; Yu, R.-Q.; Cui, Y.; Ren, B. J. Phys.
Chem. C 2008, 112, 6499. (j) Kuo, P.-L.; Chen, C.-C. Langmuir 2006, 22, 7902. (k) Perrault, S.D.;
Chan, W.C.W. J. Am. Chem. Soc. 2009, 131, 17042. (l) Frens, G. Nat. Phys. Sci. 1973, 241, 20.
29 (a) Schmid, G.; Pfeil, R.; Boese, R.; Bandermann, F.; Meyer, S.; Calis, G. H. M.; van der Velden, J.
W. A. Chem. Ber. 1981, 114, 3634. (b) Schmid, G. Inorg. Synth. 1990, 27, 214. (c) Schmid, G. Chem.
Rev. 1992, 92, 1709.
30 Selected recent reviews: (a) Maity, P.; Xie, S.; Yamauchi, M.; Tsukuda, T. Nanoscale 2012, 4, 4027.
(b) Lu, Y.; Chen, W. Chem. Soc. Rev. 2012, 41, 3594. (c) Sardar, R.; Funston, A. M.; Mulvaney, P.;
Murray, R. W. Langmuir 2009, 25, 13840. (d) Häkkinen, H. Chem. Soc. Rev. 2008, 37, 1847. (e)
Schmid, G. Chem. Soc. Rev. 2008, 37, 1909. (f) Ott, L. S.; Finke, R. G. Coord. Chem. Rev. 2007, 251,
1075.
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31 Precipitate was collected at the bottom of reaction vessel and it was removed as a suspension in the
organic solvent, whereas metal mirror was formed on the internal walls of reaction vessel and remained
after removing the solution.
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32 Li, C.; Yang, J.; Yang, P.; Lian, H.; Lin, J. Chem. Mater. 2008, 20, 4317.
33 Zhao, P.; Huang, K. Cryst. Growth Des. 2008, 8, 717.
34 Wang, H.; Fan, G.; Zheng, C.; Xiang, X.; Li, F. Ind. Eng. Chem. Res. 2010, 49, 2759.
35 Mann, F.G.; Wells, A.F.; Purdie, D. J. Chem. Soc. 1937, 1828.
36 See supporting information for the details on preparation and yields of the complexes.
37 ESI-MS study of the synthesis of (R3P)AuCl from HAuCl4 has revealed a side-reaction leading to
R3P=S and resulting in a decrease of complex yield. The choice of the sulfur reagent was important to
decrease the contribution of the side-reaction and to maintain the scope for different R3P ligands.
38 For the subsequent preparation of gold materials described in the present study utilization of HAuCl4
as a starting point was an important aim (cost-efficiency).
39 López, S.; Herrero-Gómez, E.; Pérez-Galán, P.; Nieto-Oberhuber, C.; Echavarren, A.M. Angew.
Chem. Int. Ed. 2006, 45, 6029.
40 (a) Nieto-Oberhuber, C.; López, S.; Echavarren, A.M. J. Am. Chem. Soc. 2005, 127, 6178. (b) Al-
Sa’Ady, A. K.; McAuliffe, C. A.; Parish, R. V.; Sandeank, J. A. Inorg. Synt. 1985, 191.
41 (a) Sun, L.; Crooks, R.M. Langmuir 2002, 18, 8231. (b) Dai, J.; Bruening, M.L. Nano Lett. 2002, 2,
497.
42
(a) Shipway, A.N.; Katz, E.; Willner, I. ChemPhysChem. 2000, 1, 18. (b) Convertino, A.;
Capobianchi, A.; Valentini, A.; Cirillo, E.N.M. Adv. Mater. 2003, 15, 1103.
43 Wang, Y.; Becker, M.; Wang, L.; Liu, J.; Scholz, R.; Peng, J.; Gösele, U.; Christiansen, S.; Ha Kim,
D.; Steinhart, M. Nano Lett. 2009, 9, 2384.
44 Zhang, H.; Xu, J.-J.; Chen, H.-Y. J.Phys. Chem. C 2008, 112, 13886.
45
Samarasinghe, S.R.; Pastoriza-Santos, I.; Edirisnghe, M.J.; Liz-Marzán, L.M. Appl. Phys. A 2008,
91, 141.
46 See the references1-13 and numerous examples therein.
47 (a) Partyka, D. V.; Robilotto, T. J.; Zeller, M.; Hunter, A. D.; Gray, T. G. Organometallics 2008, 27,
28. (b) Ferrer, C.; Amijs, C. H. M.; Echavarren, A. M. Chem. Eur. J. 2007, 13, 1358. (c) Herrero-
Gómez, E.; Nieto-Oberhuber, C.; López, S.; Benet-Buchholz, J.; Echavarren, A. M. Angew. Chem. Int.
Ed. 2006, 45, 5455. (d) Nieto-Oberhuber, C.; López, S.; Muñoz, M. P.; Jiménez-Núñez, E.; Buñuel,
E.; Cárdenas, D. J.; Echavarren, A. M. Chem. Eur. J. 2006, 12, 1694. (e) Mézailles, N.; Ricard, L.;
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Gagosz, F. Org. Lett. 2005, 7, 4133. (f) Chen, Y.; Chen, M.; Liu, Y. Angew. Chem. Int. Ed. 2012, 51,
6493.
48 Mauleón, P.; Zeldin, R.M.; González, A.Z.; Toste, F.D. J. Am. Chem. Soc. 2009, 131, 6348.
49 (a) Teller, H.; Flügge, S.; Goddard, R.; Fürstner, A. Angew. Chem. Int. Ed. 2010, 49, 1949. (b)
Amijs, C. H. M.; López-Carrillo, V.; Raducan, M.; Pérez-Galán, P.; Ferrer, C.; Echavarren, A. M. J.
Org. Chem. 2008, 73, 7721.
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50 Hashmi, A. S. K.; Häffner, T.; Yang, W.; Pankajakshan, S.; Schäfer, S.; Schultes, L.; Rominger, F.;
Frey, W. Chem. Eur. J. 2012, 18, 10480.
51
Belyakov, P. A.; Kadentsev, V. I.; Chizhov, A. O.; Kolotyrkina, N. G.; Shashkov, A. S.; Ananikov,
V. P. Mendeleev Commun. 2010, 20, 125.
52 Kashin, A. S.; Ananikov, V. P. Russ. Chem. Bull. Int. Ed. 2011, 60, 2602.
53 For the sections 3.2 – 3.4 the reactions were optimized for 5 mg of gold precursor since it
corresponds for the amount of gold materials usually used in catalytic procedures (0.5 – 3 mol% of
catalyst for preparation of 2.5 – 0.4 mmol of product).
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