Pale yellow single crystals of the composition Ln₃X₂[As₂O₅][AsO₃] (Ln = Tm for X = Br and Ln = Sm for X = Cl) were obtained via solid‐state reactions in the systems Ln₂O₃/As₂O₃ from sealed silica ampoules using different halides as fluxing agents. Sm₃Cl₂[As₂O₅][AsO₃] and Tm₃Br₂[As₂O₅][AsO₃] crystallize isotypically in the triclinic space group P1 with Z = 2 and cell parameters of a = 543.51(4) pm, b = 837.24(6) pm, c = 1113.45(8) pm, α = 90.084(2)°, β = 94.532(2)°, γ = 90.487(2)° for the samarium and a = 534.96(4) pm, b = 869.26(6) pm, c = 1081.84(8) pm, α = 90.723(2)°, β = 94.792(2)° γ = 90.119(2)° for the thulium compound. The isotypic crystal structure of both representatives exhibits three crystallographically different Ln³⁺ cations, each with a coordination number of eight. (Ln1)³⁺ and (Ln2)³⁺ are only coordinated by three oxygen atoms, whereas (Ln3)³⁺ shows additional contacts to halide anions in forming square [LnO₄X₄]^9– antiprisms. All As³⁺ cations are surrounded by three oxygen atoms in the shape of isolated [AsO₃]^3– ψ¹‐tetrahedra. They occur either isolated or condensed as pyroanionic [As₂O₅]^4– units with a bridging oxygen atom. In both anions, non‐binding lone‐pair electrons are present at the As³⁺ cations with a pronounced stereochemically active function.

中文翻译：

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三斜晶系镧系元素（III）卤化物氧化砷（III）Sm3Cl2 [As2O5] [AsO3]和Tm3Br2 [As2O5] [AsO3]

苍白组合物的黄色单晶LN ₃ X ₂ [如₂ ö ₅ ] [ASO ₃ ]（LN =的Tm为X = Br和LN =钐为X = Cl）的分别通过固态反应在系统中获得LN ₂使用不同卤化物作为助熔剂的密封二氧化硅安瓿瓶中的O ₃ / As ₂ O ₃。Sm ₃ Cl ₂ [As ₂ O ₅ ] [AsO ₃ ]和Tm ₃ Br ₂ [As ₂O ₅ ] [AsO ₃ ]在三斜空间群P 1中同型结晶，Z = 2，单元参数a = 543.51（4）pm，b = 837.24（6）pm，c = 1113.45（8）pm，α = 90.084（2）°，β = 94.532（2）°，γ = 90.487（2）°为钐和一个= 534.96（4）时，b = 869.26（6）时，C ^ = 1081.84（8）时，α = 90.723（2）°，β = 94.792（2）° γfor化合物为90.119（2）°。两种代表的同型晶体结构均表现出三个晶体学上不同的Ln ³⁺阳离子，每个阳离子的配位数为8。（Ln 1）³⁺和（Ln 2）³⁺仅由三个氧原子配位，而（Ln 3）³⁺在形成正方形[ Ln O ₄ X ₄ ] ^9-反棱镜时显示出卤化物阴离子的额外接触。所有As ³⁺阳离子由三个氧原子中的分离出的形状包围[ASO ₃ ] ^3- ψ ¹-四面体。它们以具有桥连氧原子的焦阴离子[As ₂ O ₅ ] ^4–单元的形式发生孤立或冷凝。在这两种阴离子中，As ³⁺阳离子都存在非结合的孤对电子，具有明显的立体化学活性功能。