Niobium peroxo compounds as catalysts for liquid-phase oxidation with hydrogen peroxide

The sodium tetraperoxo niobate, Na-3[Nb(O-2)(4)] . 13H(2)O (1) was prepared by fusing Nb2O5 with NaOH followed by reacting with aqueous H2O2 and chara cterised by single-crystal X-ray analysis and TGA. 1 was tested for the epo xidation of cyclohexene and oxidation of alcohols with hydrogen peroxide as a homogeneous catalyst. The [Nb(O-2)(4)](3-) anion was found to catalyse t he epoxidation of cyclohexene with 30% aqueous H2O2 in homogeneous solution giving cyclohexene oxide in a 73% selectivity and 7% cyclohexene conversio n at 45 degrees C. It also showed some catalytic activity for the homogeneo us oxidation of alcohols (ethanol, isopropanol, 1- and 2-butanol) with H2O2 . The [Nb(O-2)(4)](3-) anion immobilised on a quaternary ammonium polystyre ne resin was much less active in the above reactions than the homogeneous c atalyst. (C) 2000 Elsevier Science B.V. All rights reserved.