Atomic Coordination, Chemical Bonding, and Electronic State of Praseodymium in Pr₂Si₇

The new binary silicide Pr 2 Si 7 is prepared by high‐pressure high‐temperature techniques at 9.5 GPa and 1100 K (600 min). The crystal structure is solved and refined using synchrotron X‐ray diffraction data. It belongs to the structure type of Ce 2 Si 7 (space group Cmmm , a = 7.1513(2) Å, b = 10.0033(2) Å, c = 4.5417(1) Å, and Z = 2). The characteristic feature of the atomic arrangement is the 3D‐polyanion formed by silicon atoms with (highest weight) topological coordination numbers of 4, 5, and 6. Analysis of chemical bonding within the electron‐localizability approach reveals six electron localizability indicator (ELI‐D) attractors around each of the three symmetrically independent silicon atoms. The bonding picture in the polyanion is characterized by the appearance of lone‐pair‐like arrangements at silicon species and two types of two‐atomic SiSi bonds. The total of six attractors for each silicon atom documents hypervalent configurations within the polyanionic framework. Magnetic susceptibility measurements indicate an oxidation state +3 for praseodymium ( f 2 configuration) with the degenerate states of the free ion being split by crystalline electric fields.