Angewandte
Chemie
Cluster Compounds
Alkynyl-Protected Au23 Nanocluster: A 12-Electron System**
Xian-Kai Wan, Shang-Fu Yuan, Qing Tang, De-en Jiang,* and Quan-Ming Wang*
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Abstract: A 23-gold-atom nanocluster was prepared by
made in a recent computational study which showed PhC C-
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NaBH4-mediated reduction of a solution of PhC CAu and
Au-C C-Ph and PhC C-Au-C C(Ph)-Au-C C-Ph motifs are
preferred on the Au(111) surface and the Au20 nanocluster
Ph3PAuSbF6 in CH2Cl2. The cluster composition was deter-
mined to be [Au23(PhC C)9(Ph3P)6]2+ and single-crystal X-ray
with the interfacial p bonding between gold and the C C
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diffraction revealed that the cluster has an unprecedented Au17
kernel protected by three PhC2-Au-C2(Ph)-Au-C2Ph motifs
and six Ph3P groups. The Au17 core can be viewed as the fusion
of two Au10 units sharing a Au3 triangle. Electronic structure
analysis from DFT calculations suggests that the stability of
this unusual 12-electron cluster is a result of the splitting of the
bond.[24] To date, only two alkynyl-protected gold nano-
clusters have been structurally determined. Konishi et al.
prepared a cluster [Au8(dppp)4(RC C)2] from dialkynyl-
ation of [Au8(dppp)4] , where a RC C group is terminally
bound as a s donor to a gold atom (dppp = 1,3-bis(diphenyl-
phosphanyl)propane).[25] More recently, we have shown that
the direct reduction of gold alkynyl precursors with NaBH4
2+
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superatomic 1D orbitals under
D3h symmetry of the
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Au17 kernel. The discovery and determination of the structure
of the Au23 cluster demonstrates the versatility of the alkynyl
ligand in leading to the formation of new cluster compounds.
led to the isolation of [Au19(PhC C)9(Hdppa)3](SbF6)2
(Hdppa = N,N-bis-(diphenylphosphino)amine).[26] The Au19
cluster has a Au13 icosahedral core protected by three
PhC2-Au-C2(Ph)-Au-C2Ph motifs and three Hdppa groups.
This is the first time that such motifs were observed
experimentally, but are they common in alkynyl-protected
gold nanoclusters? The Au19 cluster is an 8-electron system
according to the superatom complex model and is therefore
a magic cluster. However, the question remains as to whether
synthesis and single-crystal X-ray determination can access
other sizes, magic numbers, or structural building blocks.
Herein, we report the synthesis and total structure
determination of a novel alkynyl-protected gold nanocluster,
Atomically precise, ligand-protected metal nanoclusters, in
particular those of gold, are interesting not only because of
their often molecule-like structures and properties but also
because of their applications in catalysis, biosensing, lumi-
nescence, and molecular electronics.[1–5] Gold nanoclusters
protected by thiolate or/and phosphine ligands have been
extensively studied,[6–21] but alkynyl-protected gold nano-
clusters are just beginning to attract attention. Tsukuda et al.
synthesized a series of alkynyl-protected gold nanoclusters
with AuxLy compositions (L is an alkynyl ligand) by the direct
ligation of phenylacetylene to preformed small Au clusters
(Au:PVP, PVP = polyvinylpyrrolidone).[22,23] However, the
structures of these alkynyl-protected gold nanoclusters have
not been determined.
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[Au23(Ph3P)6(PhC C)9](SbF6)2 (1), featuring a unprecedented
Au17 core (or kernel), PhC2-Au-C2(Ph)-Au-C2Ph motifs, and
12 free electrons. Both geometric and electronic structural
analyses of this new cluster will be presented.
The cluster was prepared from the reduction of a CH2Cl2
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As frequently demonstrated for thiolate-protected gold
nanoclusters, total structural determination is crucial to
understanding the interfacial bonding and the correlation
between structure and properties. An alkynyl ligand contains
suspension containing PhC CAu and Ph3PAuSbF6 (2:1) by
NaBH4. The sample was firstly characterized by ESI-TOF-
MS (Figure 1). The peak at m/z 3506.57 corresponds to
[Au23(PhC C)9(Ph3P)6] . Its isotopic distribution pattern is
2+
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a C C group that can function as both s and p donors in
in perfect agreement with the simulated one. X-ray photo-
electron spectroscopy (XPS) yielded a binding energy of
84.4 eV for Au 4f7/2 (see the Supporting Information, Fig-
ure S1), indicating the gold atoms in 1 are presented largely as
Au0 centers.
coordinating metals, which provides more diverse structural
motifs in comparison to a thiolate. This point has been clearly
[*] X.-K. Wan, S.-F. Yuan, Prof. Dr. Q.-M. Wang
State Key Lab of Physical Chemistry of Solid Surfaces
Collaborative Innovation Center of Chemistry for Energy Materials
(iChEM), Department of Chemistry
The structure of 1 was determined by single-crystal X-ray
diffraction.[27] The dicationic cluster [Au23(PhC C)9(Ph3P)6]
2+
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consists of 23 gold atoms, 9 phenylethynyl ligands, and 6
triphenylphosphine ligands. The top view of 1 is shown in
Figure 2a. The structure has C3 symmetry with a Au17 kernel
surrounded by three PhC2-Au-C2(Ph)-Au-C2Ph motifs, col-
ored green, yellow, and red. These motifs are called staple
motifs, in analogy to the RS-Au-SR-Au-SR motifs found in
Aun(SR)m clusters. The three staple motifs are arranged in an
up and down pattern alternately to surround the Au core
around the center, forming a helical configuration (Fig-
ure 2b). As illustrated in Figure 2c, three Ph3P ligands are
located at the top of the kernel and the other three are at the
bottom, each coordinated to a gold atom. The very similar
College of Chemistry and Chemical Engineering
Xiamen University, Xiamen, 361005 (P.R. China)
E-mail: qmwang@xmu.edu.cn
Dr. Q. Tang, Prof. Dr. D. Jiang
Department of Chemistry, University of California
Riverside, CA, 92521 (USA)
E-mail: de-en.jiang@ucr.edu
[**] This work was supported by the 973 program (2014CB845603), the
Natural Science Foundation of China (21125102, 21390390, and
21473139) and the University of California, Riverside.
Supporting information for this article is available on the WWW
Angew. Chem. Int. Ed. 2015, 54, 1 – 5
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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