LAUSR

White microcrystalline diamagnetic oxoperoxotungstate(VI) complexes K[WO(O2 ) 2F]·H2O, K2 [WO(O2 )2(CO3 )]·H2O, [WO(O2 )(SO4 )(H2O)2] have been synthesized from reaction of Na2WO4 ·2H2O with aqueous HF, solid KHCO3 , aqueous H2SO4 (W:F− 1:3; W: CO3 2 − 1:1; and W: SO4 2 − 1:3), and an excess of 30% H2O2 at pH 7.5–8. Precipitation was completed by the addition of precooled acetone. The occurrence of terminal WO and triangular bidentate O2 2 −(C 2 v ) in the synthesized compounds was ascertained from IR spectra. The IR spectra also suggested that the F− and SO4 2 − ions in K[WO(O2 ) 2F]·H2O and [WO(O2 )(SO4 )(H2O)2] were bonded to the WO +4 center in monodentate manner, while CO3 2 − ion in K2 [WO(O2 )2(CO3 )]·H2O binds the metal center in bidentate chelating fashion. The complex [WO(O2 )(SO4 )(H2O)2] is stable upto 110°C. The water molecule in [WO(O2 )(SO4 )(H2O)2] is coordinated to the WO +4 center, whereas it occurs as water of crystallization in the corresponding peroxo(fluoro) and peroxo(carbonato) compounds. Mass spectra of the compounds are in good agreement with the molecular formulae of the complexes. K2 [WO(O2 )2(CO3 )]·H2O acts as an oxidant for bromide in the aqueous-phase bromination of organic substrates to the corresponding bromo-organics, and the complex also oxidizes Hantzsch-1,4-dihydropyridine to the corresponding pyridine derivative in excellent yield at room temperature. Density functional theory computation was carried out to compute the frequencies of relevant vibrational modes and electronic properties, and the results are in agreement with the experimentally obtained data.