Electronic Variations in Carbonate- and Phosphane-Related 24- and 26-Electron E4 Clusters of Silicon and Germanium

Isolated starlike E4clusters form the basis of the crystal strucures of the novel isotypic Zintl compounds M5+xMg18−xE13 (M=Sr, Ba; E=Si, Ge, see picture). The geometry and electronic structure of this species already gave rise to several controversial discussions in the literature. Quantum chemical investigations and physical properties of the presented compounds allow a new view on stability and electronic configuration of the starlike E4 cluster.