χ-Octamolybdate [MoV4MoVI4O24]4−: An Unusual Small Polyoxometalate in Partially Reduced Form from Nonaqueous Solvent Reduction



The first mixed-valent octamolybdate anion [MoV4MoVI4O24]4−, termed χ-octamolybdate due to its shape, was obtained by partial reduction of α-(Bu4N)4[Mo8O26] in dry acetonitrile. Single-crystal X-ray structure analysis revealed that the anion includes an unusual MoV4O8 cubane-like cluster core, whose four side faces are capped by four MoO4 units to form a crosslike cluster. X-ray photoelectron spectroscopy (XPS) and bond valence sum (BVS) calculations were carried out to validate the presence of mixed-valent Mo centers.