Synthesis, Structural Characterization and Property Optimization of Novel Antimonides and Bismuthide

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Synthesis, Structural Characterization and
Property Optimization of Novel Antimonides and
Bismuthides
Svilen Bobev Department of Chemistry and
Biochemistry, University of Delaware Newark, DE
19716
The new compound Ba11Cd6Sb12 was synthesized and
structurally characterized by single-crystal
X-ray diffraction. Its structure features CdSb4
tetrahedra that share corners and form
polyanionic sub-structure consisting of
one-dimensional ribbons. There also are some
short SbSb bonds, which zip the corners of two
CdSb4 tetrahedra, leading to a unique arrangement
that was dubbed double pentagonal tubes as
shown in the picture. Applying the classic
concepts to rationalize the bonding in this
structure type appears straightforward and
results in the formulation A211Cd6Sb1222,
i.e., Ba11Cd6Sb12 should be a salt-like Zintl
phase. However, from analyses of the chemical
bonding based on ab-initio calculations, it can
be suggested that the simplistic description of
the structure is not informative two of the
CdSb interactions are very weak and are
inconsistent with the notion of
2-center-2-electron bonding. These findings
complement our recent reports on other related
Zintl phases with transition metals, suggesting
an inadequacy of the classic (empirical) rules
for electron counting for understanding the
complicated structures of these intermetallic
compounds.