A research article authored by Professor Slavi Sevov and coworkers at Notre Dame was chosen by the editors of the journal Science as a highlight of the recent literature.
Houses of Triangles: Atomic clusters often adopt cage-like geometries with triangular faces, such as the tetrahedron, octahedron, and icosahedron. Goicoechea and Sevov have extended this series by constructing a germanium cluster composed of 32 triangles. The Ge18 ellipsoid has approximate threefold symmetry and a charge of 4-, and was crystallized with four charge-balancing potassium ions that were sequestered inside cryptand ligands. The cluster encapsulates two palladium atoms, which appear to stabilize the large cage from within by overlapping with the Ge orbitals. The synthesis fuses the two cluster halves together from a solution of K4Ge9 and tetrakis(triphenylphosphine) palladium precursors. Although a similar geometry has been seen in extended solid lattices, mass spectrometry confirmed that these structures are stable as discrete species in solution.
For more information see the article in J. Am. Chem. Soc. 2005, 127, 7676.