V^IIIV^IV₃O₃(PO₄)₃:  A Novel Vanadium Phosphate for Selective Oxidation of Light Hydrocarbons

A novel vanadium(IV) phosphate V^IIIV^IV₃O₃(PO₄)₃ has been synthesized and crystallized (1073 K, sealed silica tube, a few milligrams of PtCl₂ as mineralizer). According to the single-crystal structure analysis [orthorhombic, F2dd (No. 63), Z = 24, a = 7.2596(8) Å, b = 21.786(2) Å, c = 38.904(4) Å (lattice parameters from Guinier photographs), R₁ = 0.032, wR₂ = 0.067, κ-CCD diffractometer, 83 949 reflections measured, 6836 independent, 5986 with I > 2σ(I), 299 variables], V^IIIV^IV₃O₃(PO₄)₃ belongs to the Lipscombite/Lazulite structure family. At 1073 K V^IIIV^IV₃O₃(PO₄)₃ is in thermodynamic equilibrium with (VO)₂P₂O₇, VO₂, and VPO₄. Substitution of V³⁺ in V^IIIV^IV₃O₃(PO₄)₃ by Cr³⁺ and Fe³⁺ is possible. Like vanadylpyrophosphate the oxide phosphates M^IIIV^IV₃O₃(PO₄)₃ (M^III:  V, Cr, Fe) show significant catalytic activity in selective oxidation of n-butane and 1-butene to maleic acid anhydride.