Abstract

Isopoly and heteropoly molybdenum- and tungstenpolyoxometalates have been widely applied to the syntheses of epoxides from olefins and of carbonium compounds from alcohols with the use of H₂O₂ as a very selective catalyst, Some of the formed peroxo complexes have generally been believed to play an important role in the reacting process as a key species, and thus many investigators have tried to determine their structures and behaviors using various kinds of <i>in situ</i> spectroscopic techniques. Recently, we have found an interesting catalytic activity of the sodium lanthanidedecatungstates, Ce(IV)-, Nd(III)-, and Sm(III)-W₁₀O₃₆^<i>n-</i> (LnW10), for the H₂O₂ decomposition and H₂O₂ oxidation of cyclohexanol. In the H₂O₂-cerium(IV) decatungstate (CeW10) reacting system, the formation of the peroxo complex and its reversible behaviors have been successfully observed with the use of <i>in situ</i> FT-Raman spectroscopy, and its unique catalytic activity for the H₂O₂ oxidation of various primary and secondary alcohols has been elucidated, In an effort to obtain more information about the structural features of the peroxo complex, <i>in situ</i> spectroscopic measurements, FT-IR and ¹⁸³W-NMR, were used under the H₂O₂-CeW10 reaction conditions. Here we wish to report a novel and unique structure of the peroxo complex and its reversible behavior as deduced from such measurements.

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