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Encyclopedia of Physical Science and Technology EN007D-343 July 10, 2001 20:13

834 Inorganic Exotic Molecules

FIGURE 11 An endohedral scandium nitride fullerene cluster
(25).
FIGURE 9 A-77 aluminum cluster (23).
taining 12, 44, and 20 Al atoms. Aggregation to form bulk
metal is prevented by 20 [N(SiMe 3 ) 2 ] ligands. Overall, the
correspondtogiantwheel-shapedclustersmadeoutofpar-
cluster can be considered an intermediate species to the
tially reduced MoO 3 units. Among others, the nano-sized
formation of bulk, solid elemental aluminum.
cluster 22 was isolated. As shown in Fig. 8, 22 contains
176 Mo and 608 oxygen centers, representing one of the
C. A Really High-Spin Molecule (S = 51/2)
largest structurally characterized inorganic molecules. In
the solid state, wheel-shaped clusters of this kind can form Evidence that transition metal clusters can display highly
nanochannels or can encapsulate other, smaller clusters. unusual physical properties was recently provided by

B. A 77-Aluminum Cluster

The largest molecular species containing metal–metal
bonds that was characterized by X-ray diffraction is the
Al 77 cluster (23) as shown in Fig. 9. A central Al atom
is surrounded by three concentric polyhedral shells con-

+
FIGURE 10 An idealized structure for the core of an S = 51/2 FIGURE 12 A grid formed with Ag (26) and the hexacoordinat-
Mn/Mo cluster (24). ing ligand itself (27).