Synthesis and Characterization of A₃Na₁₀Sn₂₃ (A = Cs, Rb, K) with a New Clathrate-Like Structure and of the Chiral Clathrate Rb₅Na₃Sn₂₅

Abstract

Four new compounds Cs17.4(1)Na60.6(1)Sn138 (1), Rb19.1(1)Na58.9(1)Sn138 (2), K21.3(1)Na56.7(1)Sn138 (3), and Rb20Na12Sn100 (4) were synthesized by fusion of the corresponding elements. The structures were determined by single-crystal X-ray diffraction. Compounds 1-3 are isostructural and crystallize in a new structure type (rhombohedral, R3m, Z = 1, a = 12.4567(9) A, c = 51.533(3) A for 1; a = 12.465(1) A, c = 51.085(3) A for 2; a = 12.456(2) A, c = 50.559(4) A for 3). The structure contains layers of fused pentagonal dodecahedra of tin that alternate with layers of isolated tin tetrahedra. It is an intergrowth between the structure of clathrate-II (A24Sn136) with the same layers of pentagonal dodecahedra and the Zintl phase ASn with Sn4(4-) tetrahedra. Compound 4 is a new chiral clathrate (cubic, P4(1)32, Z = 1; a = 16.4127(7) A) with stoichiometry that corresponds to an electronically balanced Zintl phase.

Structure and Phase Stability of Binary Zintl-Phase Compounds: Lithium–Group 13 Intermetallics and Metal-Doped Group 14 Clathrate Compounds

“…Recent experimental results show that when a mixture of alkali and alkaline earth elements is used one can synthesize new structures. [24,26,27,71,72] Representative structures chosen from our study are described below. The sodalite structure X 12 (X C, Si, Ge, Sn) is composed of both four-and six-membered rings.…”

“…twelve pentagonal faces (5 12 , i.e., a dodecahedron). By addition of atoms to this polyhedron, other types of cages can be built, which differ in the number of hexagonal faces: T 24 (5 12 6 2 ), T 26 (5 12 6 3 ), and T 28 (5 12 6 4 ). X 38 is seen in the amalgams A 3 Hg 20 (A Rb, Cs) [75] and consists of three and four-membered rings.…”

Crystal structure of barium europium germanide, Ba6-xEuxGe25 (x = 0.6), a chiral clathrate

“…The rather large elongation of the displacement ellipsoid for the M2 site (Table 3) is typical for all members of the Ba 6In4Ge21 family [1][2][3][4][5][6][7][8][9][10]. For Ba 5.4Eu0.6Ge25, the electron density distribution around the M2 position was additionally modelled using two split sites (M2¢ and M2², Table 2).…”

Stannides and Intermetallic Tin Compounds – Fundamentals and Applications

“…Ternary stannides with smaller and larger cations have more systematically been investigated in recent years by the Sevov group [68 -71]. The stannides A 3 Na 10 Sn 23 (A = K, Rb, Cs) [69] contain fused pentagonal dodecahedra and layers of isolated tin tetrahedra. An arachno- [Sn 8 ] 6− cluster occurs in A 4 Li 2 Sn 8 (A = K, Rb) [71].…”