Caesium thorium silicate, Cs₂ThSi₆O₁₅

A caesium thorium(IV) silicate has been synthesized serendipitously under high-temperature solid-state conditions by the reaction of Th^IV with a fused silica/alumina reaction crucible. The compound crystallizes in the orthorhombic space group Pca2₁. The crystal structure consists of ThO₆ distorted octa­hedra corner-shared with SiO₄ tetra­hedra to form an anionic three-dimensional framework possessing extended channels containing Cs⁺ cations. Cs₂ThSi₆O₁₅ is a phyllosilicate with the same sheet structure as β-K₃NdSi₆O₁₅.

Europium antimony sulfide, Eu₆Sb₆S₁₇

Eu₆Sb₆S₁₇ is isotypic with Sr₆Sb₆S₁₇ and can be regarded as consisting of two isolated [Sb₃S₇]^5- anions and an S₃^2- polysulfide anion that are joined together by Eu²⁺ cations. There are six crystallographically unique Eu²⁺ cations bound by sulfide and polysulfide anions in seven-, eight- and nine-coordinate environments. Each of the [Sb₃S₇]^5- anions consists of a trinuclear assembly of corner-sharing SbS₃ units. The [Sb₃S₇]^5- anions are connected by long (3.1 Å) Sb-S inter­actions, forming one-dimensional ribbons running down the a axis and packed with opposing directions of polarity. The bent S₃^2- anions stack in columns parallel to the a axis, oriented in opposing directions with respect to one another. The overall structure is three-dimensional and has channels running down the a axis to house the stereochemically active lone pair of electrons on the Sb³⁺ centers. The presence of Eu²⁺ is supported by both magnetic measurements and bond-valence calculations.