Layers built from caesium cations and heptaphosphanortricyclane anions: synthesis and crystal structure of [NEt3Me][Cs2P7]·NH3 and [NEt4][Cs2P7]·4NH3

Abstract

Exchange of one caesium cation of Cs₃P₇ for NEt₃Me⁺ or NEt₄⁺ in liquid ammonia gave [NEt₃Me][Cs₂P₇]·NH₃1 and [NEt₄][Cs₂P₇]·4NH₃2, respectively. The crystal structure of the compounds have been determined. They show the existence of corrugated _∞²[Cs₂P₇]^– layers stacked along the crystallographic a axis in both compounds. The layers are topologically equivalent in 1 and 2. While the layers are repeated in the same orientation in 1, stacking mode AAA, they have two different orientations in 2, stacking mode ABAB, where B is related to A by a mirror plane. The space between the layers contains ammonia of solvation completing the co-ordination of caesium, and the tetraalkylammonium cations.