Fluorine Tagging of Polyoxometalates: The Cyclic [{MoV2O4(H2O)}4{O3PC(CF3)(O)PO3}4]12–

Abstract

AbstractWe have discovered a simple and efficient strategy to incorporate fluorine into polyoxometalates by reaction of thefluorinated diphosphonate H2O3PC(CF3)(OH)PO3H2 with [MoV2O4(H2O)6]2+ in aqueous medium (pH = 6.4) resulting in [{MoV2O4(H2O)}4{O3PC(CF3)(O)PO3}4]12– (1), which was structurally characterized in solution by multinuclear NMR spectroscopy and in the solid state by single‐crystal X‐ray diffraction, infrared, thermogravimetric and elemental analyses. Polyanion 1 crystallizes as the mixed sodium/guanidinium salt Na6.5[(H2N)3C]5.5[{MoV2O4(H2O)}4{O3PC(CF3)(O)PO3}4]·8H2O (1a) in the monoclinic system, space groupC2/c with the unit‐cell parameters a = 34.0685(95) Å, b = 8.0874(19) Å, c = 34.4101(10) Å, β = 100.20(2)°, V = 9331.02(4) Å3 and Z = 2. The novel polyanion 1 has a cyclic, saddle‐like structure with four {Mo2O4(H2O)} units linked by four fully deprotonated diphosphonate moieties. In addition, the (CF3)C–OH moiety is deprotonated, due to the electronic effects of the neighboring CF3 group, leading to the formation of an Mo–O(C) bond. Solution 31P and 19F NMR studies of 1 indicate magnetic inequivalence of the two phosphorus atoms in each diphosphonate moiety. The solid‐state packing of the title polyanions in 1a by loosely bound Na+ counterions leads to an AAA‐type arrangement.