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

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.