Stannaspherene (Sn122-) and Plumbaspherene (Pb122-)

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Stannaspherene (Sn122-) and Plumbaspherene
(Pb122-) Lai-Sheng Wang, Washington State
University Award (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
synthesized in the form of KSn12- (KSn122-)
with a similar PES spectrum as Sn12-. 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. The bonding
pattern in Sn122- is similar to the well-known
B12H122- cage, with the twelve 5s2 localized
electron pairs replacing the twelve B-H bonds.
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. 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. 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.
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) L. F. Cui, X. Huang,
L. M. Wang, J. Li, and L. S. Wang, J. Phys.
Chem. A 110, 8/31 (2006)