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New Examples for the Unexpected Stability of the 10π‐Electron Hückel Arene [Si 6 ] 10–
Author(s) -
Gil Raul Cardoso,
CarrilloCabrera Wilder,
Schultheiss Martin,
Peters Karl,
Schnering Hans Georg von,
Grin Yuri
Publication year - 1999
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/(sici)1521-3749(199902)625:2<285::aid-zaac285>3.0.co;2-v
Subject(s) - crystallography , chemistry , materials science
The compounds Ba 4 Ag 2 Si 6 , Eu 4 Ag 2 Si 6 , and Ca 4 Ag 2 Si 6 , prepared from the elements at 1273 K (the components in inner corundum crucibles are enclosed in sealed quartz ampoules), are brittle semiconductors with silvery luster. They react slowly with acids liberating hydrogen. Ba 4 Ag 2 [Si 6 ] and Eu 4 Ag 2 [Si 6 ] crystallize like Ba 4 Li 2 [Si 6 ] (space group Fddd (No. 70); a = 8.613 Å, b = 14.927 Å, c = 19.639 Å, and a = 8.420 Å, b = 14.585 Å, c = 17.864 Å, respectively), whereas Ca 4 Ag 2 [Si 6 ] represents a new structure type (space group Fmmm (No. 69); a = 8.315 Å, b = 14.391 Å, c = 8.646 Å). The three compounds are Zintl phases with the formal charges M 2+ , Ag + and [Si 6 ] 10– . The mean bond lengths d(Si–Si) = 2.335–2.381 Å in the 10π‐Hückel arene [Si 6 ] 10– as well as d(Ag–Si) = 2.464–2.595 Å vary with the size of the M 2+ cations. The chemical bonding was analyzed in terms of the Electron Localization Function (ELF) and compared with the bonding in related systems (Ce 4 Co 2 Si 6 ).