Sm5Ga3

Single crystals of penta­samarium trigallium, Sm₅Ga₃, display tetra­gonal symmetry. The crystal structure was solved and refined in space group P4/ncc. The present work does not confirm the space group I4/mcm previously deduced from powder data measurements. One Sm atom is in a general position, and the other Sm atom and one of the Ga atoms are at sites with fourfold symmetry. The remaining Ga atom is at a site with twofold symmetry.     

Die Kristallstrukturen von Rh10Ga17 und Ir3Ga5

Zusammenfassung Die Kristallstrukturen von Rh₁₀Ga₁₇ und Ir₃Ga₅ werden bestimmt und mittels zweidimensionalerFourier-Synthesen verfeinert. Die beiden Verbindungen gehören zu einer Gruppe von TiSi₂-Abkömmlingen der allgemeinen Formel T _n B_2n-m (TB_2-x ). Die Gitterkonstanten betragen für Rh₁₀Ga₁₇ a=5,813;c=47,46 und für Ir₃Ga₅ a=5,823;c=14,20 Å.

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The crystal structures of Rh₁₀Ga₁₇ and Ir₃Ga₅ have been determined by means of two-dimensionalFourier syntheses. The crystal structure of the two compounds of the general formula T _n B_2n-m (TB_2-x ) can be derived from the TiSi₂-type. The lattice parameters were found to be: Rh₁₀Ga₁₇ a=5,813;c=47,46 and Ir₃Ga₅ a=5,823;c=14,20 Å.

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Mit 2 Abbildungen     

Die Phasen Nb3Ga2, Ta5Ga3 und Ta5Al3Bx

Zusammenfassung Die Phasen Nb₃Ga₂, Ta₅Ga₃ und Ta₅Al₃B_x werden aus den Komponenten hergestellt. Nb₃Ga₂ kristallisiert im U₃Si₂-Typ, Ta₅Ga₃ hat Cr₅Br₃-Struktur (T 2) und Ta₅Al₃B_x ist mit Mn₅Si₃ (teilweise aufgefüllt) isotyp.     

ROLE OF Ga AND Pt-Ga IN THE CONVERSION OF PROPANE OVER Ga/HZSM-5 AND Pt-Ga/HZSM-5

为获得较高的Ｃ２选择性，在加水（水蒸气）条件下，研究了添加ＣａＯ对甲烷氧化偶联Ｌａ２Ｏ３催化剂的影响。发现ＣａＯ的添加提高了Ｌａ２Ｏ３催化剂的活性，同时水的添加明显地提高了催化剂的Ｃ２选择性。在加水条件下，Ｌａ２Ｏ３－ＣａＯ催化剂获得了较好的结果，其ＣＨ４转换率为２０％，Ｃ２选择性超过８０％。利用ＸＲＤ和ＸＰＳ技术对催化剂进行了表征，并对加水和不加水条件下的催化剂性能与结构变化的关系进行了讨论     

Darstellung und Struktur von Li5Ga4

Preparation and Crystal Structure of Li₅Ga₄ Li₅Ga₄ has been established as further, hitherto unknown phase in the LiGa system. The new compound crystallizes in the trigonal system (P3 m1—D_3d³) with a = 437.5 ± 0.2 pm, c = 825.7 ± 0.2 pm, c/a = 1.885. The structure is strongly related to those of LiGa and Li₃Ga₂.     

Oxygen-Bridged Ga2(Et)3(OTeF5)3 and the Weakly Coordinating Anions [Ga(Et)(OTeF5)3]− and [Ga(OTeF5)4]−

Salts of the weakly coordinating anions [Ga(OTeF₅)₄]⁻ as well as [Ga(Et)(OTeF₅)₃]⁻ and the neutral Ga₂(Et)₃(OTeF₅)₃ were synthesized and characterized by spectroscopic methods and single-crystal X-ray diffraction. Ga₂(Et)₃(OTeF₅)₃ was formed by treating GaEt₃ with pentafluoroorthotelluric acid (HOTeF₅) and reacted with PPh₄Cl and CPh₃Cl to [PPh₄][Ga(Et)(OTeF₅)₃] and [CPh₃][Ga(Et)(OTeF₅)₃]. In contrast, Ag[Ga(OTeF₅)₄] was prepared from AgOTeF₅ and GaCl₃ and was used as a versatile starting material for further reactions. Starting with Ag[Ga(OTeF₅)₄] the substrates [PPh₄][Ga(OTeF₅)₄] and [CPh₃][Ga(OTeF₅)₄] were formed from PPh₄Cl and CPh₃Cl.     

Elektronenmangelverbindungen des Galliums Zur Kenntnis von Ca3Ga5

Electron Deficient Compounds of Gallium: Crystal Structure of Ca₃Ga₅ The stoichiometry of the formerly described compound Ca₂Ga₃ is corrected to Ca₃Ga₅. This compound crystallizes in the orthorhombic system, space group Cmcm (No. 63) with the lattice constants see ?Inhaltsübersicht”?. In the structure there is a Ga framework for which on the basis of the Gillespie/Nyholm conception and by calculating the bond numbers according to Pauling a characteristic electron concentration can be derived.     

Na，NBA－Ga－Si－ZSM－5杂原子沸石分子筛的表征

Ｎａ，ＮＢＡ┐Ｇａ┐Ｓｉ┐ＺＳＭ┐５杂原子沸石分子筛的表征高志贤程昌瑞谭长瑜李源（中国科学院山西煤炭化学研究所，太原０３０００１）关键词Ｇａ－Ｓｉ－ＺＳＭ－５沸石分子筛，正丁胺，表征，模板作用近年来的研究结果表明，使用不同类型的有机胺或醇作引导剂，甚...     

镓改性ZSM-5沸石中镓活性中心的形成与表征

采用脉冲微反体系研究了经不同程度还原和不同镓含量的GaZSM-5沸石的芳构化性能与吡啶吸附红外光谱特征谱带吸收度的关联，证实了1458 cm~(-1)吸收带的用于表征与Ga物种有关的活性中心，并研究了沸石的硅铝比对Ga中心形成和Ga的价态对芳构化性能的影响。结果表明，对Ga含量相同的样品来说，硅铝比愈低，起始Ga中心生成量愈多，高价态与低价态的Ga中心对丙烷芳构化反应都有促进作用。     

Propane transformation on H-GaZSM-5 as a function of Ga content

Gallosilicates with different contents of gallium have been studied in propane aromatization reaction. Catalytic evaluations were carried out at atmospheric pressure, varying temperature and reactant flow. The best results in yield to BTX products were obtained for samples with gallium contents of 3–5 wt. %.     

Ga/HZSM-5分子筛上乙烯二聚反应的理论研究

应用理论计算方法研究了Ga/HZSM-5及Al/HZSM-5 分子筛上乙烯二聚生成1-丁烯的反应历程, 比较了分子筛酸性对反应能量的影响. 计算采用分为两层的76T簇模型, 应用量子力学和分子力学联合的 ONIOM2 (B3LYP/6-31G(d, p):UFF) 方法. 乙烯二聚过程可按照分步机理和协同机理进行, 均得到表面丁基烷氧中间产物. 计算结果表明, 与在Al/HZSM-5分子筛上的反应过程相比, 乙烯在 Ga/HZSM-5分子筛上的吸附能低 20.62 kJ·mol^-1, 但质子化反应的活化能只高出1.26 kJ·mol^-1; 而乙基烷氧中间体与乙烯分子结合过程的活化能高出 62.55 kJ·mol^-1, 原因是Ga 原子半径大, 降低了六元环过渡态的稳定性. 若按协同机理, 质子转移和C―C键聚合同时进行, 在 Ga/HZSM-5分子筛上的活化能较Al/HZSM-5的高16.44 kJ·mol^-1. 因此乙烯二聚按照协同机理有利. 研究还表明, 表面丁基烷氧中间体脱质子, 生成1-丁烯并吸附在复原的分子筛酸性位上. 该反应在两种酸中心上的活化能几乎相同, 但明显高于其他各步的活化能, 因此成为整个反应的速度控制步骤.