A new mixed valent molybdenum monophosphate with a tunnel structure: Cs3Mo8O11(PO4)8

A new mixed valent molybdenum monophosphate, Cs₃Mo₈O₁₁(PO₄)₈, with a tunnel structure, has been synthesized. It crystallizes in the space group C2/m with a=20.203 (2) Å, b=6.370 (1) Å, c=14.379 (1) Å and β=99.827 (7)°. Its Mo₈P₈O₄₃]_∞ 3D-framework consists of single phosphate groups, single MoO₆ octahedra, and bioctahedral units of corner-sharing octahedra Mo₂O₁₁ and of edge-sharing octahedra Mo₂O₁₀. The entire host lattice can be described by the association of MoPO₈]_∞ chains running along b, through the corners of their octahedra and tetrahedra, and through the edges of their octahedra, forming large tunnels running along b where the Cs⁺ cations are located. Bond valence calculations show that in the bioctahedral units, the electrons are delocalized between the two Mo atoms.