The isolation and characterization of the monomeric bis[peroxotitanium(IV)]-substituted alpha-Keggin polyoxometalate (POM) K-7[alpha-1,2PW(10)(TiO2)(2)O-38]center dot 8H(2)O (1) and the monomeric bis[hydroperoxotitanium(IV)]-substituted alpha-Keggin POM K-5[alpha-1,2-PW10(TiOOH)(2)O-38]center dot 5H(2)O (2) are described. The orange solution was prepared by adding an excess amount of aqueous 30% H2O2 to the in situ-generated monomeric Keg.-in species [alpha-1,2-PW10Ti2O40](7-) in a neutral aqueous solution derived by the hydrolytic cleavage of the dimeric, Ti-O-Ti bridged anhydride form K-10[alpha-1,2-PW10Ti2O39](2)center dot 18H(2)O. Reprecipitation of the orange solution with MeOH gave a thermally stable yellow species containing the peroxo groups (compound 1) whereas reprecipitation with EtOH yielded a relatively unstable orange species that would contain the hydroperoxo groups (compound 2). The characterization of 1 and 2 was accomplished by a complete elemental analysis, TG/DTA, FTIR, UV-vis, solution (P-31 and W-183) NMR and P-31 CPMAS NMR spectroscopy, and (for 1 only) X-ray crystallography. Complex 1 did not show any activity for 2-propanol oxidation in the absence of 30% H2O2 whereas complex 2 showed an effective activity for the oxidation reaction. (c) 2006 Elsevier B.V. All rights reserved.