Dilithium manganese(II) catena-tetrakis(polyphosphate), Li₂Mn(PO₃)₄

The poly-phosphate Li₂Mn(PO₃)₄ was synthesized and its structure characterized from powder diffraction data by Averbuch-Pouchot & Durif [J. Appl. Cryst. (1972), 5, 307–308]. These authors showed that the structure of this phosphate is isotypic to that of Li₂Cd(PO₃)₄, as confirmed by the present work. The structure is built from infinite zigzag polyphosphate chains, [(PO₃)⁻]_n, extending along [010]. These polyphosphate chains are connected by sharing vertices with MnO₆ octa­hedra (site symmetry .m.) and Li₂O₇ polyhedra, which form also chains parallel to [010]. Adjacent chains are linked by common vertices of polyhedra in such a way as to form porous layers parallel to (100). The three-dimensional framework delimits empty channels extending along [010].

Potassium trinickel(II) orthophosphate diphosphate, KNi₃(PO₄)P₂O₇

The structure of the title compound is characterized by the presence of two different anions, (PO₄)³⁻ and (P₂O₇)⁴⁻ with an eclipsed conformation. The crystal structure consists of edge-sharing [NiO₆] octa­hedra forming an [Ni₃O₁₄] chain running parallel to [001]. Adjacent chains are connected through edges and apices to PO₄ and P₂O₇ groups in such a way as to build a three-dimensional host lattice. The resulting framework presents inter­secting tunnels running along [010] and [101] in which the 11-coordinated potassium cation is located. The crystal structure of this new phosphate probably represents a new structural type.