Two novel Zintl compounds Na12Ge8Sn and Na15Ge8SnP: Single crystal and electronic structures

Two mixed anionic Zintl phases, Na12Ge8Sn and Na15Ge8SnP, have been synthesized and structurally characterized. Na12Ge8Sn crystallizes in the tetragonal space group P41212 (#92, a = 14.1172(2) Å, c = 21.8483(7) Å, V = 4354.3(2) Å3, Z = 8, and R/wR = 0.0481/0.1213) and Na15Ge8SnP crystallizes in the orthorhombic space group Cmcm (#63, a = 17.517(4) Å, b = 12.890(3) Å, c = 11.111(2) Å, V = 2508.7(9) Å3, Z = 4, and R/wR = 0.0313/0.0669). Both compounds adopt new structure types and are made up of isolated Na+ cations, anionic (Ge4)4− tetrahedral clusters, and Sn4− or P3− anions. The structure of Na12Ge8Sn can be described as a square packing of two kinds of columns, highly distorted Sn centered Na icosahedra chains ([Na9Sn]5+∞1) and highly distorted Na(1) centered anti-rectangular prism (four (Ge4)4− and four Na, [Na3(Ge4)2]5−∞1) chains. The structure of Na15Ge8SnP is composed of cationic [Na15SnP]8+∞1 saw tooth-like chains, which are made up of Sn centered Na bicapped hexagonal prisms and P centered tricapped trigonal prisms, extending along the c axis with anionic (Ge4)4− tetrahedral clusters between the chains. The electronic structures have been studied using density functional theory.

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