A new form of decavanadate: Hydrothermal synthesis and structural characterization of Ba_5.33(H₃O)_0.33[ V₁₀O₃₀]

The hydrothermal reaction of V₂O₅, BaCl₂ ·2H₂O, ethylenediamine and H₂O in the mole ratio 1:1:2.8:925 at 200°C for 5 days yielded black crystals of Ba_5.33(H₃O)_0.33[V₁₀O₃₀] in 20% yield. The structure consists of discrete decavanadate clusters [V₁₀O₃₃] ^11- and Ba²⁺ and H₃O⁺ cations. The molecular anion is constructed from four {V₂O₇)^4- units, each acting in a bidentate linkage mode to the central (V₂O₂}⁵⁺ unit. The tetrahedral sites associated with the {V₂O₇}^4- moieties are in the +5 oxidation state, while the reduced site is delocalized over the two central square pyramidal sites. Crystal data for HBa_5.33O_30.33V₁₀: cubic Im3̄, a= 16.9439(2) Å, V=4864.5(1) ų Z=6, D_calc = 3.540 g cm^-3; R=0.0255 for all 1077 reflections.