Synthesis and characterisation of a new niobate complex with chromium(III)

A new hexaniobate complex with chromium(III) was prepared and characterised by analytical and spectroscopic techniques. The compound is a violet, non-crystalline solid, formulated as [Cr-2(mu-OH)(H3Nb6O19)(en)(3)(H2O)] It was synthesised in aqueous solution by reaction of [Cr(en)3](3+), en = ethylenediammine, with the hexaniobate anion [Nb6O19](8-), at pH 8. Thermal decomposition yielded a mixture of CrNbO4 and Nb2O5 The synthesis of this compound shows that the hexaniobate anion may form complexes at lower pH values than previously reported.