Srub>7ub>Geub>6ub>, Baub>7ub>Geub>6ub> and Baub>3ub>Snub>2ub> -Three new binary compounds containing dumbbells and four-membered chains of tetrel atoms with considerable Ge-Ge 蟺-bonding character

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• 作者：Lisa Siggelkow ; Viktor Hlukhyy ; Thomas F. Fä ; ssler ; ^{thomas.faessler@lrz.tum.de} ; ^{thomas.faessler@lrz.tu-muenchen.de}
• 关键词：Alkaline earth metal ; Stannide ; Germanide ; Zintl phases ; Intermetallic phase ; Chemical bonding
• 刊名：Journal of Solid State Chemistry
• 出版年：2012
• 期刊代码：130_00224596
• 类别：ch
• 出版时间：July, 2012
• 卷：191
• 期：Complete
• 页码：76-89
• 文件大小：2685 K

摘要

The germanides Srub>7ub>Geub>6ub> and Baub>7ub>Geub>6ub> as well as the stannide Baub>3ub>Snub>2ub> were prepared by arc melting and annealing in welded tantalum ampoules using induction as well as resistance furnaces. The compounds were investigated by powder and single crystal X-ray diffraction. Srub>7ub>Geub>6ub> and Baub>7ub>Geub>6ub> crystallize in the Caub>7ub>Snub>6ub> structure type (space group Pmna, Z=4: a=7.777(2) 脜, b=23.595(4) 脜, c=8.563(2) 脜, wRub>2ub>=0.081 (all data), 2175 independent reflections, 64 variable parameters for Srub>7ub>Geub>6ub> and a=8.0853(6) 脜, b=24.545(2) 脜, c=8.9782(8) 脜, wRub>2ub>=0.085 (all data), 2307 independent reflections, 64 variable parameters for Baub>7ub>Geub>6ub>). Baub>3ub>Snub>2ub> crystallizes in an own structure type with the space group P4ub>3ub>2ub>1ub>2, Z=4, a=6.6854(2) 脜, c=17.842(2) 脜, wRub>2ub>=0.037 (all data), 1163 independent reflections, 25 variable parameters.

In Srub>7ub>Geub>6ub> and Baub>7ub>Geub>6ub> the Ge atoms are arranged as Geub>2ub> dumbbells and Geub>4ub> four-membered atom chains. Their crystal structures cannot be rationalized according to the (8-N) rule. In contrast, Baub>3ub>Snub>2ub> presents Snub>2ub> dumbbells as a main structural motif and thereby can be described as an electron precise Zintl phase. The chemical bonding situation in these structures is discussed on the basis of partial and total Density Of States (DOS) curves, band structures including fatbands, topological analysis of the Electron Localization Function (ELF) as well as Bader analysis of the bond critical points using the programs TB-LMTO-ASA and Wien2k. While Baub>3ub>Snub>2ub> reveals semiconducting behaviour, all germanides Aeub>7ub>Geub>6ub> (Ae=Ca, Sr, and Ba) show metallic properties and a considerable 蟺-bonding character between the Ge atoms of the four-membered chains and the dumbbells. The 蟺-bonding character of the germanides is best reflected by the resonance hybrid structures {[Ge-Ge]^{6鈭?/sup>/[GeGeGeGe]8鈭?/sup>}鈫攞[Ge=Ge]4鈭?/sup>/[Ge-Ge-Ge-Ge]10鈭?/sup>}.}