The [Sn-5](2-) cluster compound [K-(2,2,2-crypt)](2)Sn-5 - Synthesis, crystal structure, Raman spectrum, and hierarchical relationship to CaIn2

Dark red crystals of [K-(2,2,2)-crypt)](2)Sn-5 precipitate after the reacti on of (2,2,2)-crypt with a solution of K1.33Sn in liquid ammonia at room te mperature. The compound is sensitive to oxidation and hydrolysis. The seque nce of Raman bands (104, 120, 133 and 180 cm(-1)) is characteristic for the trigonal bipyramidal closo-[Sn-5](2-) cluster anion. The wave numbers corr espond with the data from Hartree-Fock calculations (114, 128, 142 and 187 cm(-1)). The compound crystallizes trigonally (a = 11.736 Angstrom, c = 22. 117 Angstrom, Z = 2, space group <P(3)over bar c1> (No. 165); Pearson code hP262), isotypic with [Na-(2,2,2)-crypt)](2)Pb-5. The atoms of the cluster show strange anisotropic displacements, which are perfectly reducible to a helical rigid-body motion around and along [001] (libration: +/-9.5 degrees ; translation +/-0.29 Angstrom). The structure can be described as a hierar chical derivative of the initiator CaIn2 (P6(3)/mmc, hP6), generated by an atom-to-aggregate replacement: [Ca][In](2) = [Sn-5][K @ C36H72N4O12](2). Th us, the distribution of the [Sn-5](2-) Zint1 anions is hexagonal primitive, and the cation complexes are located close to the centers of trigonal supe rprisms formed by Sn5 clusters.