Crystal Structure of a Tetrameta-Polyphosphate: Pb2Cs3(P4O12)(PO3)3

Chemical preparation and crystal structure of Pb₂Cs₃(P₄O₁₂)(PO₃)₃ are described. The triclinic unit cell has the following dimensions: space group is P1 with Z = 2. The crystal structure has been solved by using 3350 unique reflexions with a final R value 0.048, The main outstanding feature of this compound rests on the coexistence in its atomic arrangement of two kinds of phosphate anions with different degrees of condensation: a tetrameric cyclic one (P₄O₁₂)^4? and a linear infinite chain (PO₃)_∞. The unit cell is crossed by two (PO₃)_∞ chains, related by centrosymmetry, running in planes perpendicular to the \documentclass{article}\pagestyle{empty}\begin{document}$ \overrightarrow {\rm c} $\end{document} axis at z ? 0.25 and 0.75. The two crystallographic independent P₄O₁₂^4? ring anions are centrosymmetrical located around (0, 1/2, 0) and (0, 1/2, 1/2) inversion centers, half way between the (PO₃)_∞ chains. Sr₂Cs₃(P₄O₁₂)(PO₃)₃ is isotypic with the title compound.