The intermetallic phases Sr 2 Pt 2 Mg and Eu 2 Pt 2 Mg were obtained by reaction of the elements in sealed tantalum tubes at high temperature. Sr 2 Pt 2 Mg crystallizes with the monoclinic Ca 2 Ir 2 Si type ( C 2/ c , a = 1020.7(7), b = 597.7(4), c = 827.0(4) pm, β = 103.37(5)°), while Eu 2 Pt 2 Mg adopts the orthorhombic W 2 CoB 2 -type structure ( Immm , a = 440.31(5), b = 582.20(6), c = 914.11(9) pm, wR = 0.0359, 277 F 2 values, 14 variables). The magnesium atoms in both structures are coordinated by four Pt 2 dumb-bells with a rectangular planar coordination in Eu 2 Pt 2 Mg (268 pm Pt–Mg) and a distorted tetrahedral one in Sr 2 Pt 2 Mg (273–275 pm Pt–Mg). The Pt–Pt distances are 277 pm in the europium and 269 pm in the strontium compound. The polyanionic [Pt 2 Mg] units are planar in Eu 2 Pt 2 Mg and separated by the europium atoms. The Sr 2 Pt 2 Mg structure shows the motif of hexagonal rod packing for the [Pt 2 Mg] rows that are embedded in a strontium matrix. Chemical bonding and the influence of the valence electron count on the formation of the structure types are discussed.

中文翻译：

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镁金属间化合物：Eu2Pt2Mg 和 Sr2Pt2Mg 的合成和结构

金属间相Sr 2 Pt 2 Mg和Eu 2 Pt 2 Mg是通过这些元素在密封的钽管中在高温下反应得到的。Sr 2 Pt 2 Mg 结晶为单斜 Ca 2 Ir 2 Si 型 ( C 2/ c , a = 1020.7(7), b = 597.7(4), c = 827.0(4) pm, β = 103.37(5)°) ), 而 Eu 2 Pt 2 Mg 采用正交 W 2 CoB 2 型结构 ( Immm , a = 440.31(5), b = 582.20(6), c = 914.11(9) pm, wR = 0.0359, 277 F 2值，14 个变量）。两种结构中的镁原子由四个 Pt 2 哑铃配位，在 Eu 2 Pt 2 Mg（268 pm Pt-Mg）中具有矩形平面配位，在 Sr 2 Pt 2 Mg（273-275 pm Pt）中具有扭曲的四面体配位-Mg)。Pt-Pt 距离在铕中为 277 pm，在锶化合物中为 269 pm。聚阴离子 [Pt 2 Mg] 单元在 Eu 2 Pt 2 Mg 中是平面的，并被铕原子隔开。Sr 2 Pt 2 Mg 结构显示了嵌入锶基体中的 [Pt 2 Mg] 行的六角棒填充图案。讨论了化学键合和价电子数对结构类型形成的影响。