Novel first-row transition-metal phosphates: hydrothermal synthesis and crystal structures.

Two new compounds, sodium copper nickel diorthophosphate, NaCuNi(PO) (I), and dimanganese copper diorthophosphate, MnCu(PO) (II), were synthesized hydrothermally, yielding single crystals, and were studied by X-ray diffraction. In the crystal structures, various transition metals of d-elements occupy symmetrically independent crystallographic positions with different coordination geometries. In the crystal structure of NaNiCu(PO), NiO and CuO octahedra share edges to form chains that PO groups link into a framework with cavities filled with Na atoms. Layered cationic fragments formed from dimers of MnO trigonal bipyramids and CuO square planes, sharing vertices, are connected through PO tetrahedra into a 3-periodic MnCu(PO) crystal structure. Structural correlations between NaNiCu(PO) and NaCuPO are discussed, and crystal-chemical details of the currently known exclusively synthetic mixed Mn/Cu and Ni/Cu phosphates are presented.