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

Two new compounds, sodium copper nickel diorthophosphate, Na 2 CuNi(PO 4 ) 2 (I), and dimanganese copper diorthophosphate, Mn 2 Cu(PO 4 ) 2 (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 Na 2 NiCu(PO 4 ) 2 , NiO 6 and CuO 6 octahedra share edges to form chains that PO 4 groups link into a framework with cavities filled with Na atoms. Layered cationic fragments formed from dimers of MnO 5 trigonal bipyramids and CuO 4 square planes, sharing vertices, are connected through PO 4 tetrahedra into a 3-periodic Mn 2 Cu(PO 4 ) 2 crystal structure. Structural correlations between Na 2 NiCu(PO 4 ) 2 and NaCuPO 4 are discussed, and crystal-chemical details of the currently known exclusively synthetic mixed Mn/Cu and Ni/Cu phosphates are presented.