Abstract

The new niobium phosphates Ba₃(NbO)₂(PO₄)₄ (1) and Co₃(NbO)₂(PO₄)₄(H₂O)₁₀ (2) have been synthesized in single crystal form by hydrothermal reactions at 250 °C and 170 °C respectively. The crystal structures have been determined from X-ray diffraction data. Both compounds contain NbP₂O₉ complex chains as a fundamental structural unit. The chains are similar to those of the known compound K₃NbP₂O₉ and structurally may be considered similar to a slice of the Zr(HPO₄)₂ layer in α-zirconium phosphate. In compound 1 the chains are separated and are held together by Ba–O bonds while in 2 the chains are linked by CoO₆ octahedra to form a framework structure.