Ammoniates of Zintl Phases: Similarities and Differences of Binary Phases A4E4 and Their Corresponding Solvates

Abstract

The combination of electropositive alkali metals A (A = Na-Cs) and group 14 elements E (E = Si-Pb) in a stoichiometric ratio of 1:1 in solid state reactions results in the formation of polyanionic salts, which belong to a class of intermetallics for which the term Zintl compounds is used. Crystal structure analysis of these intermetallic phases proved the presence of tetrahedral tetrelide tetraanions [E 4 ] 4− precast in solid state, and coulombic interactions account for the formation of a dense, three-dimensional cation-anion network. In addition, it has been shown that [E 4 ] 4− polyanions are also present in solutions of liquid ammonia prepared via different synthetic routes. From these solutions crystallize ammoniates of the alkali metal tetrahedranides, which contain ammonia molecules of crystallization, and which can be characterized by X-ray crystallography despite their low thermal stability. The question to be answered is about the structural relations between the analogous compounds in solid state vs. solvate structures, which all include the tetrahedral [E 4 ] 4− anions. We here investigate the similarities and differences regarding the coordination spheres of these anions and the resulting cation-anion network. The reported solvates Na 4 Sn 4 •13NH 3 , Rb 4 Sn 4 •2NH 3 , Cs 4 Sn 4 •2NH 3 , Rb 4 Pb 4 •2NH 3 as well as the up to now unpublished crystal structures of the new compounds Cs

Structural Chemistry of Halide including Thallides A8Tl11X1−n (A = K, Rb, Cs; X = Cl, Br; n = 0.1–0.9)

“…The first naked thallium cluster was described in 1967 by Hansen and Smith in the binary solid-state compound Na 2 Tl [9], which contains Tl 4 tetrahedra with a calculated formal charge of −8 by assuming complete electron transfer. These tetrahedral assemblies are related to the structures of ATt (A: alkali metal, Tt: group 14 element) [10][11][12] and white phosphorus due to their formal iso-(valence)-electronic character. The largest (empty) thallide cluster is represented by the Tl 11 7− cluster which is present in binary materials A 8 Tl 11 [13,14] and A 15 Tl 27 [15] (A = K, Rb, Cs).…”

Investigations on the Solubility of Sn4‐Cluster Compounds in Liquid Ammonia

“…In the meantime, bare [Sn 4 ] 4clusters were observed in ammoniates with Li, [8] Na, [8][9] Rb, [10] and Cs [10] counter ions, and in a hydroxide containing potassium phase. [8] Special reaction conditions had been applied, often simply due to the fact that originally other products or reactions were intended which also lead to transition metal complexes of tetrahedral cluster anions like Rb 6 [(η 2 -Sn 4 )Zn(η 3 -Sn 4 )] • 5 NH 3 [11] and K 7 [(η 2 -Sn 4 )Au(η 2 -Sn 4 )] • 16 NH 3 . [12] A simple dissolution of Na 4 Sn 4 was successfully carried out in presence of [18]crown-6 and mesityl copper, which were not found in the solid product, [9] and the Cs compound was synthesized form tetraphenyl tin and an excess of elemental Cs.…”

Spotlight on Alkali Metals: The Structural Chemistry of Alkali Metal Thallides

“…Corbett to perform the structure determination of the latter compound. Tetrahedral shaped anions in solid state structures are wellknown in tetrelide chemistry [67], where the binaries of 1:1 stoichiometry form E4 4− anions. The coordination number within the different observed structure types in these cases is 12 (NaGe and NaSi type) and 16 (KGe and NaPb type).…”