Stannaspherene (Sn122-) and Plumbaspherene (Pb122-)

1
Stannaspherene (Sn122-) and Plumbaspherene
(Pb122-) Lai-Sheng Wang, Washington State
University, DMR 0503383
During photoelectron spectroscopy (PES)
experiments aimed at understanding the
semiconductor to metal transition in tin
clusters, the spectrum of Sn12- was observed to
be remarkably simple and totally different from
the corresponding Ge12- cluster, suggesting that
Sn12- is a unique and highly symmetric cluster.
Structural optimization starting from an
icosahedral (Ih) cluster led to a slightly
distorted cage with C5v symmetry. However,
adding an electron to Sn12- resulted in a stable
closed-shell Ih-Sn122- cluster, which was
produced in the form of KSn12- (KSn122-). The
Ih-Sn122- cage is shown to be bonded by four
delocalized radial p bonds and nine delocalized
on-sphere tangential ? bonds from the 5p orbitals
of the Sn atoms, whereas the 5s2 electrons remain
largely localized and nonbonding. Both the
?-bonding and the highly spherical symmetry of
the 12-atom Sn cluster are analogous to the C60
fullerene and a name stannaspherene is coined
for this highly special cluster 1. The
corresponding 12-atom Pb cluster is also found to
be an icosahedral cage cluster and a name
plumbaspherene has been coined to describe its
?-bonding and high symmetry 2. Both
stannaspherene and plumbaspherene have diameters
exceeding 6 Å and can host most transition metal
atoms in the periodic table, giving rise to a
large class of endohedral chemical building
blocks (M_at_Sn12 or M_at_Pb12) for potential new
cluster-assembled nanomaterials 3.
1 L. F. Cui, X. Huang, L. M. Wang, D. Y.
Zubarev, A. I. Boldyrev, J. Li, and L. S. Wang,
J. Am. Chem. Soc. 128, 8390 (2006). 2 L. F.
Cui, X. Huang, L. M. Wang, J. Li, and L. S. Wang,
J. Phys. Chem. A 110, 10169 (2006). 3 L. F.
Cui, X. Huang, L. M. Wang, J. Li, and L. S. Wang,
Angew. Chem. Int. Ed. 119, 756 (2007).
2
Pd2_at_Sn184-) Fusion of Two Endohedral
Stannaspherenes (Pd_at_Sn122-) Lai-Sheng Wang,
Washington State University, DMR 0503383
One of the major objectives of cluster science is
to discover stable atomic clusters, which may be
used as building blocks for cluster-assembled
materials. The discovery and bulk synthesis of
the fullerenes have sprouted new research
disciplines in chemistry, materials science, and
nanoscience and precipitated intense interests to
search for other similar stable clusters.
Recently, we have discovered a stable icosahedral
12-atom Sn cluster (stannaspherene Sn122),
which has also been shown to be able to trap all
transition metals to form gaseous endohedral
clusters (M_at_Sn12). During exploratory solution
syntheses of endohedral stannaspherenes, a new
closo-deltahedral cluster, Pd2_at_Sn184, has been
isolated as a (2,2,2-crypt)K salt through the
reaction of K4Sn9 and PdP(C6H5)34 in
ethylenediamine solutions and characterized via
X-ray crystallography. The new Pd2_at_Sn184
cluster has pseudo-D3d symmetry and is composed
of 18 Sn atoms encapsulating two Pd atoms. It
can be viewed as the fusion of two endohedral
stannaspherenes (Pd_at_Sn122) along their C3 axis
by removing a Sn3 triangle on each Sn12 unit at
the cluster-cluster interface. Electronic
structure calculations show that Pd2_at_Sn184
consists of a Sn184 cage with two zero valent Pd
atoms and possesses a highly stable electronic
configuration. The new cluster can be viewed as
an analogue of C70, whereas stannaspherene can be
viewed as an analogue of the buckyball C60.
Z. M. Sun, H. Xiao, J. Li, and L. S. Wang, J.
Am. Chem. Soc. 128, 9560 (2007).
3
Broader Impacts and Educational
Outreach Lai-Sheng Wang, Washington State
University, DMR 0503383
A graduate level course (Phys. 581 Nanoclusters,
Nanomaterials, and Nanotechnology) has been
developed, which is based primarily on research
results from this grant. Since 2003, this course
has been offered during the summer on-site at
Pacific Northwest National Laboratory and
integrated as a course for the Joint Institute of
Nanotechnology between PNNL and University of
Washington, allowing students from all
institutions in the pacific northwest to
participates. During the two week course,
students also gain hands-on research experiences
by working on small research projects in the PIs
lab, as well as in others labs at the
Environmental Molecular Sciences Laboratory of
PNNL.