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首页> 外文期刊>Zeitschrift fur Anorganische und Allgemeine Chemie >Binary lanthanum stannides close to the 1:1 ratio - Synthesis, crystal structure, chemical bonding
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Binary lanthanum stannides close to the 1:1 ratio - Synthesis, crystal structure, chemical bonding

机译：二氧化锡锡接近于1：1的比例-合成，晶体结构，化学键合

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摘要

Four binary lanthanum stannides close to the 1:1 ratio of Sn:La were synthesized from mixtures of the elements. The structures of the compounds have been determined by means of single-crystal X-ray data. The low temperature (α) form of LaSn (CrB-type, orthorhombic, space group Cmcm, a = 476.33(6), b = 1191.1(2), c = 440.89(6) pm, Z = 4, R1 = 0.0247), crystallizes with the CrB-type. The structure exhibits planar tin zigzag chains with a Sn-Sn bond length of 299.1 pm. In contrast to the electron precise Zintl compounds of the alkaline earth elements, additional La-Sn bonding contributions become apparent from the results of band structure calculations. In the somewhat tin-richer region, the new compound La_3Sn_4 (orthorhombic, space group Cmcm, a = 451.45(4), b = 1190.44(9), c = 1583.8(2) pm, Z = 4, R1 = 0.0674), crystallizing with the Er_3Ge_4 structure type, exhibits Sn_3 segments of the zigzag chains of α-LaSn together with a further Sn atom in a square planar Sn coordination with increased Sn-Sn bond lengths. In the Lanthanum-richer region, La_(11)Sn_(10) (tetragonal, space group I4/mmm, a = 1208.98(5), c = 1816.60(9) pm, Z = 4, R1 = 0.0325) forms the undistorted tetragonal Ho_(11)Ge_(10) structure type. Its structure, which contains isolated Sn atoms, [Sn_2] dumbbells and planar [Sn_4] rings is related to the high temperature (β) form of LaSn. The structure of β-LaSn (space group Cmmm, a = 1766.97(6), b = 1768.28(5), c = 1194.32(3) pm, Z = 60, R1 = 0.0453), which forms a singular structure type, can be derived from that of La_(11)Sn_(10) by the removal of thin slabs. Due to the different stacking of the remaining layers, planar [Sn_4] chain segments and linear [Sn-Sn-Sn] anions are formed as additional structural elements. The chemical bonding (Sn-Sn covalent bonding, Sn-La contributions) is discussed on the basis of the simple Zintl concept and the results of FP-LAPW calculations (density of states, band structure, valence electron densities and electron localization function).
机译：从元素的混合物中合成了四种接近Sn：La 1：1比例的二元锡镧系元素。化合物的结构已经通过单晶X射线数据确定。 LaSn的低温（α）形式（CrB型，正交，空间群Cmcm，a = 476.33（6），b = 1191.1（2），c = 440.89（6）pm，Z = 4，R1 = 0.0247）结晶为CrB型。该结构显示出平面锡字形链，Sn-Sn键长为299.1 pm。与碱土元素电子精确的Zintl化合物相反，从能带结构计算的结果中可以明显看出其他La-Sn键的贡献。在较富锡的区域中，新化合物La_3Sn_4（斜方晶，空间群Cmcm，a = 451.45（4），b = 1190.44（9），c = 1583.8（2）pm，Z = 4，R1 = 0.0674），以Er_3Ge_4结构类型结晶时，在具有增加Sn-Sn键长的方形平面Sn配位中，显示出α-LaSn之字形链的Sn_3片段以及其他Sn原子。在富含镧的区域中，La_（11）Sn_（10）（四边形，空间群I4 / mmm，a = 1208.98（5），c = 1816.60（9）pm，Z = 4，R1 = 0.0325）形成无畸变四角形Ho_（11）Ge_（10）结构类型。其结构包含孤立的Sn原子，[Sn_2]哑铃和平面[Sn_4]环，与LaSn的高温（β）形式有关。可以形成单一结构类型的β-LaSn结构（空间群Cmmm，a = 1766.97（6），b = 1768.28（5），c = 1194.32（3）pm，Z = 60，R1 = 0.0453）通过去除薄板从La_（11）Sn_（10）导出。由于剩余层的堆叠不同，平面[Sn_4]链段和线性[Sn-Sn-Sn]阴离子形成为其他结构元素。在简单的Zintl概念和FP-LAPW计算结果（状态密度，能带结构，价电子密度和电子定位功能）的基础上，讨论了化学键（Sn-Sn共价键，Sn-La贡献）。

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