An alternative approach to rationalizing the structures of the cyclotrisilicates: Rb₁₀[Si₆O₁₇], Cs₈[Si₆O₁₆] and Na₃Y[Si₆O₁₅] by viewing them in light of the extended Zintl–Klemm concept

Abstract

The structures of the three dimeric cyclotrisilicate anions [Si6O17](10-), [Si6O16](8-) and [Si6O15](6-) forming part of the compounds Rb10[Si6O17] or Rb14[Si4][Si6O17], Cs8[Si6O16] and Na3Y[Si6O15], respectively, have been described as different ways of condensing the more elemental cyclotrisilicate anions [Si3O9](6-) [Hlukhyy & Fässler (2013). Z. Anorg. Allg. Chem. 639, 231-233]. Such a description prevents a rational explanation of the connectivity between the Si atoms. So, in this article the Si skeletons of the above silicate anions are put on a common basis in light of the extended Zintl-Klemm concept. Their connectivity is directly related to the ratio Ψ-S/Ψ-P resulting from the number of electrons transferred from the electropositive Na, Y, Rb and Cs atoms, offering a new example of the fact that there exists a univocal link between chemical composition (in terms of pseudo-atoms) and structure: the generalized Zintl-Klemm concept. The three skeletons fit the connectivity of hypothetical Zintl polyanions of composition [Ψ-S4P2](10-), [Ψ-S2P4](8-) and [Ψ-P6](6-) respectively.