New Mixed-Valent Molybdenum Monophosphates with the KMo3P2O14 structure

New mixed valent molybdenum monophosphates AMo₃P₂O₁₄ have been synthesized for A = Ag, Rb, Na, Sr. The single crystal X-ray diffraction study of two of them (A = Ag, Sr) shows that they belong to the layer structure type KMo₃P₂O₁₄. Their structure consists of Mo₃P₂O₁₄]_∞ layers involving MoO₆ octahedra and MoO₅ bipyramids, interleaved with A cations forming bicapped trigonal prisms AO₈. Bond valence calculations show a localisation of the Mo^V and Mo^VI species according to the formula A¹Mo^V_oct1Mo^VI_oct2Mo^VI_bipyP₂O₁₄ for A = Ag, Na and SrMo^V_oct1Mo^V_oct2Mo^VI_bipyP₂O₁₄. A comparison between the different Mo^V? Mo^VI phosphates is made.