Revealing the Nature of Chemical Bonding in an ALn2Ag3Te5-Type Alkaline-Metal (A) Lanthanide (Ln) Silver Telluride

Although the electronic structures of several tellurides have been recognized by applying the Zintl-Klemm concept, there are also tellurides whose electronic structures cannot be understood by applications of the aforementioned idea. To probe the appropriateness of the valence-electron transfers as implied by Zintl-Klemm treatments of ALn2Ag3Te5-type tellurides (A = alkaline-metal; Ln = lanthanide), the electronic structure and, furthermore, the bonding situation was prototypically explored for RbPr2Ag3Te5. The crystal structure of that type of telluride is discussed for the examples of RbLn2Ag3Te5 (Ln = Pr, Nd), and it is composed of tunnels which are assembled by the tellurium atoms and enclose the rubidium, lanthanide, and silver atoms, respectively. Even though a Zintl-Klemm treatment of RbPr2Ag3Te5 results in an (electron-precise) valence-electron distribution of (Rb+)(Pr3+)2(Ag+)3(Te2−)5, the bonding analysis based on quantum-chemical means indicates that a full electron transfer as suggested by the Zintl-Klemm approach should be considered with concern.