Synthesis, Characterization, and Bonding of Heteroatomic Clusters: Na₁₃Cd₂₀E₇ (E = Pb, Sn), a Further Example of a Structure Containing Empty Icosahedra without an Element of Group 13

The compounds Na13Cd20E7 (E = Pb, Sn) were made in nearly 100% yield by quenching the melts of appropriate mixtures of elements sealed in niobium containers. They crystallize in the cubic space group Im3̄, Z = 4, with a = 15.992(2) and 15.790(4) Å for E = Pb and Sn, respectively. The Cd/E part of the structure is a framework of heavily fused monocapped truncated trigonal prisms. Twelve-bonded icosahedra are nested in cavities of the framework. This is the second example of a structure containing empty icosahedra made without the participation of an element of the boron group. The sodium cations occupy the space between the clusters and inside the 13-atom polyhedra.