On the Nature of Ge–Pb Bonding in the Solid State. Synthesis, Structural Characterization, and Electronic Structures of Two Unprecedented Germanide-Plumbides

Reported are the syntheses and the crystallographic characterization of two structurally related solid-state compounds: (Eu1–xCax)2Ge2Pb (space group Pbam) and (SrxEu1–x)2Ge2Pb (space group Cmmm). Both structures boast anionic sublattices with fully ordered Ge and Pb at the atomic level, which is unusual for elements of the same group. Despite the nearly identical formulas and the similar chemical makeup, the nature of the chemical bonding in the two compounds is subtly different; in the (Eu1–xCax)2Ge2Pb structure, Ge and Pb are positioned at a relatively shorter distance from one another (2+ ground state ([Xe]­4f7 configuration) and the presence of an antiferromagnetic ordering at cryogenic temperatures.