ChemInform Abstract: Framework Compounds with Mobile La^III Cations: Syntheses, Crystal Structures and Structural Dynamics of the Lanthanum(III) Iron(II) Sulfide Halides La₅₃Fe₁₂S₉₀X₃ (X: Cl, Br, I).

Abstract

Lanthanum(III) Iron(II) Sulfide HalidesLa53Fe12S90X3 (X: Cl, Br, I). -The title compounds are synthesized by reaction of La2S3 and FeS in a reactive LaX3 (X: Cl, Br, I) flux at 1320 K (graphite crucible in an evacuated quartz tube, 2 d). The compounds are isostructural and crystallize in the rhombohedral space group R3m with Z = 1 (single crystal XRD). The structure contains face-shared S 9 double-octahedra which are linked to are linked to bi-or tri-capped La III S6+n (n = 2 or 3) trigonal prisms by face-and vertex-sharing, forming a three-dimensional framework containing cuboctahedral cavities of two sizes. The larger cavities are filled by halide ions, while the smaller cavities accommodate numerous sites for disordered lanthanum cations, modelling a network of diffusion pathways through the structure. Molecular dynamic simulations confirm a strong coupling between the motions of the mobile lanthanum ions and the neighboring sulfide ions. -(BRAEUNLING, D.; LEONI, S.; MILLS, A. M.; RUCK*, M.; Z.