Crystal structure of novel Ni-Zn borides: first observation of a boron-metal nested cage unit: B20Ni6.
Crystal structure of novel Ni-Zn borides: first observation of a boron-metal nested cage unit: B20Ni6.
复制标题
新型镍锌硼化物的晶体结构：首次观察到硼金属嵌套笼单元：B20Ni6。
作者：
Z. Malik;O. Sologub;A. Grytsiv;G. Giester;P. Rogl
用X射线单晶衍射（XSC）和X射线粉末衍射（XPD）技术结合电子探针分析（EMPA）确定了三种三元Ni-Zn硼化物的晶体结构。Ni（21）Zn（2）B（24）晶体具有独特的结构类型（空间群I4/mmm; a = 0.72103（1）nm和c = 1.42842（5）nm; R（F）（2）= 0.017），它包含由两个波纹状的双硼环组成的B（20）单元的特征孤立笼，它们通过硼原子在四个位置连接。B（20）单元在所有六个面上都有八元环，就像立方体的面一样。每个面的中心是一个镍原子。六个镍原子以八面体的形式排列，嵌套在B（20）单元内。这种硼聚集是独特的，并且在金属-硼化学中以前从未遇到过。Ni（12）Zn B（8-x）（x = 0.43;空间群Cmca，a = 1.05270（2）nm，B = 1.45236（3）nm，c = 1.45537（3）nm; R（F）（2）= 0.028）的晶体结构为Ni（12）Al B（8）的五个硼原子有限锯齿链结构类型。化合物Ni（3）ZnB（2）具有独特的结构类型（空间群C2/m，a = 0.95101（4）nm，B = 0.28921（4）nm，c = 0.84366（3）nm，β = 101.097（3）°，R（F）（2）= 0.020），其特征在于B（4）锯齿形链段，B-B键长为0.183-0.185 nm。Ni（3）ZnB（2）结构与Dy（3）Ni（2）型有关。
The crystal structures of three ternary Ni-Zn borides have been elucidated by means of X-ray single-crystal diffraction (XSC) and X-ray powder diffraction techniques (XPD) in combination with electron microprobe analyses (EMPA) defining the Ni/Zn ratio. Ni(21)Zn(2)B(24) crystallizes in a unique structure type (space group I4/mmm; a = 0.72103(1) nm and c = 1.42842(5) nm; R(F)(2) = 0.017), which contains characteristic isolated cages of B(20) units composed of two corrugated octogonal boron rings, which are linked at four positions via boron atoms. The B(20) units appear to have eight-membered rings on all six faces like the faces of a cube. Each face is centered by a nickel atom. The six nickel atoms are arranged in the form of an octahedron nested within the B(20) unit. Such a boron aggregation is unique and has never been encountered before in metal-boron chemistry. The crystal structure of Ni(12)ZnB(8-x) (x = 0.43; space group Cmca, a = 1.05270(2) nm, b = 1.45236(3) nm, c = 1.45537(3) nm; R(F)(2) = 0.028) adopts the structure type of Ni(12)AlB(8) with finite zigzag chains of five boron atoms. The compound Ni(3)ZnB(2) crystallizes in a unique structure type (space group C2/m, a = 0.95101(4) nm, b = 0.28921(4) nm, c = 0.84366(3) nm, β = 101.097(3)°, and R(F)(2) = 0.020) characterized by B(4) zigzag chain fragments with B-B bond lengths of 0.183-0.185 nm. The Ni(3)ZnB(2) structure is related to the Dy(3)Ni(2) type.