Ein neues Kupferzinnboratoxid mit isolierten BO3-Baugruppen: Cu5Sn(BO3)2O4

Sn3B8O15: A Ternary Tin(II) Borate with Flexible [B8O18]12- Fundamental Building Block Formed by [B7O16]11- and [BO3]3- Groups

Owing to the tendency to form the glass state in growing crystals in the ternary tin(II) borate system, hitherto, very few single crystals in ternary tin(II) borate were reported. In this paper, a single crystal of Sn₃B₈O₁₅ was obtained via a high temperature solution method in a closed system. The structure features a flexible fundamental building block [B₈O₁₈]^12- constructed by one [BO₃]^3- unit and one [B₇O₁₆]^11- group that contains three hexatomic rings, which further connect to compose a two-dimensional ²_∞[B₈O₁₅] layer structure. The connection mode and flexibility of the three hexatomic B-O rings were analyzed, verifying the structural diversity of the B-O configuration. Moreover, the synthesis, crystal structure, and various characterizations were comprehensively presented. Also, theoretical calculations were employed to discuss structure-property relationships, and we use the real-space atom-cutting techniques to explain the origin of the birefringence of Sn₃B₈O₁₅.

On the structural relations of malachite. I. The rosasite and ludwigite structure families

The crystal structures of malachite Cu2(OH)2CO3 and rosasite (Cu,Zn)2(OH)2CO3, though not isotypic, are closely related. A previously proposed approach explaining this relation via a common hypothetical parent structure is elaborated upon on the basis of group–subgroup considerations, leading to the conclusion that the aristotype of malachite and rosasite should crystallize in the space group Pbam (No. 55). An ICSD database search for actual representatives of this aristotype leads to the interesting observation that the structure type of ludwigite (Mg,Fe)2FeO2BO3, which is adopted by several natural and synthetic oxide orthoborates M 3O2BO3, is closely related to the proposed malachite–rosasite aristotype and thus to the malachite–rosasite family of hydroxide carbonates M 2(OH)2CO3 in general. Relations within both structure families and their analogies are summarized in a joint simplified Bärnighausen tree.