Preparation and some properties of vanadium(III) tris(metaphosphate) and vanadium(IV) bis(metaphosphate)

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Vanadium(IV) bis(metaphosphate), [VO][PO3]2(d1), and vanadium(III) tris(metaphosphate), V[PO3]3(d2). have been prepared by heating V2O5 in phosphoric acid. Blue crystals of [VO][PO3]2 are tetragonal, space group I41md, with lattice parameters a0= 10.973(10), c0= 4.293(4)Å, and Z= 4. Green crystals of V[PO3]3 are monoclinic, space group Cc, with lattice parameters a0= 13.19(1), b0= 19.08(2), c0= 9.42(1)Å, β= 127° 08(6)′, and Z= 12. The bis(phosphate) probably contains chains of corner-shared [VO6]8– octahedra linked by metaphosphate ([PO3]–)∞ chains. The tris(phosphate) is structurally similar to the C-type metaphosphates of Mo, Ti, Cr, Fe, and Al. Both compounds are resistant to most solvents and stable in air to at least 1 000 °C and have been characterised by magnetic-susceptibility and electronic-spectral measurements. Neither compound shows magnetic ordering down to 1.5 K. Possible non-linear optical properties of [VO][PO3]2 are mentioned.