Reactions of hydrogen peroxide with several lacunary polyoxometalates of the 1:11 series, XW 11 O 39 m - (X = Co 3+, Ga 3+, Fe 3+, Si 4+, and P 5+ ), are reported. Synthetic pathways to new polyoxotungstates incorporating dioxygen moieties (peroxo and/or superoxo) are developed. The key step involves treating lacunary precursors with H 2 O 2 in strongly buffered aqueous solutions. Upon reaction of H 2 O 2 with α-[Co 3+ W 11 O 39 ], 9 - (a) the central tetrahedral Co 3+ is reduced to Co 2+ and (b) each of the four unshared oxygens surrounding the vacancy are replaced by a peroxide group, yielding salts of the tetraperoxide anion β 3 -[(Co 2+ O 4 )W 11 O 31 (O 2 ) 4 ] 10 - ( 1 ). These results are unequivocally established by a combination of elemental analysis, spectroscopy (UV−Vis−near-IR and IR), magnetic moment determination, and complete X-ray crystal structure analysis of (NH 4 ) 9 K[(Co 2+ O 4 )W 11 O 31 (O 2 ) 4 ]·5H 2 O. The dioxygen O−O bonds are 1.41 and 1.44 Å, typical of peroxo complexes. Salts of 1 are excellent stereoselective catalysts for the oxidation/epoxidation by H 2 O 2 . Reaction of 2 - cyclohexenol with H 2 O 2 catalyzed by 1 yields cis- and trans -2,3-epoxycyclohexen - 1 - ol (59.3% and 3.6%, respectively) and 2 - cyclohexen - 1 - one (28.3%). According to ESR and IR spectroscopic results, the reaction of H 2 O 2 with other lacunary XW 11 O 39 m - anions (X = P 5+, Si 4+, Ga 3+, and Fe 3+ ) proceeds by a different mechanism which involves the loss of heteroatom and formation of an isopolytungstate containing superoxo moieties ( g 1 = 2.039, g 2 = 2.014, g 3 = 2.009; ν 0 - 0 = 1040 and 1060 cm - 1 ).
No takes yet. Share an insight, caveat, or question.
Server-Carrió et al. (1999) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: