Srb>7b>Geb>6b>, Bab>7b>Geb>6b> and Bab>3b>Snb>2b> -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 Srb>7b>Geb>6b> and Bab>7b>Geb>6b> as well as the stannide Bab>3b>Snb>2b> 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. Srb>7b>Geb>6b> and Bab>7b>Geb>6b> crystallize in the Cab>7b>Snb>6b> structure type (space group Pmna, Z=4: a=7.777(2) 脜, b=23.595(4) 脜, c=8.563(2) 脜, wRb>2b>=0.081 (all data), 2175 independent reflections, 64 variable parameters for Srb>7b>Geb>6b> and a=8.0853(6) 脜, b=24.545(2) 脜, c=8.9782(8) 脜, wRb>2b>=0.085 (all data), 2307 independent reflections, 64 variable parameters for Bab>7b>Geb>6b>). Bab>3b>Snb>2b> crystallizes in an own structure type with the space group P4b>3b>2b>1b>2, Z=4, a=6.6854(2) 脜, c=17.842(2) 脜, wRb>2b>=0.037 (all data), 1163 independent reflections, 25 variable parameters.

In Srb>7b>Geb>6b> and Bab>7b>Geb>6b> the Ge atoms are arranged as Geb>2b> dumbbells and Geb>4b> four-membered atom chains. Their crystal structures cannot be rationalized according to the (8-N) rule. In contrast, Bab>3b>Snb>2b> presents Snb>2b> 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 Bab>3b>Snb>2b> reveals semiconducting behaviour, all germanides Aeb>7b>Geb>6b> (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>}.}