Structures of Medium-Sized Ruthenium Clusters: The Octahedral Motif

We describe the first direct structural characterization of medium-sized ruthenium clusters (Ru-19(-), Ru-28(-), Ru-38(-), and Ru-44(-)) by using a combination of trapped ion electron diffraction and density functional theory. We find close-packed structures based on octahedral geometries: Ru-19(-) and Ru-44(-) are closed-shell octahedra whereas Ru-28(-) is a double octahedron. In the case of Ru-38(-), instead of a truncated octahedron we obtain evidence for lower symmetry structures containing a reentrant surface.