Two vanadyl arsenates templated with ethylendiamonium (EnVAs) and piperazonium (PipVAs) were evaluated as catalysts for the oxidation of thioethers and alkenes, using H 2 O 2 and t-butyl hydroperoxide (TBHP) as oxidants. The intrinsic activity of EnVAs was higher than that of PipVAs for the oxidation of sulfides. Similar results were obtained when using either H 2 O 2 or TBHP as oxidants. However, the sterical effects were enhanced when TBHP was used and higher selectivities towards sulfoxides were achieved with this oxidant. The catalytic activity of the V-based materials in the epoxidation of simple alkenes and allylic alcohols was assessed. Upon reuse, both materials show no significant decrease in their catalytic properties.
1.-INTRODUCTIONOpen-framework metal phosphates are of considerable technological importance as shapeselective catalysts, ion-exchange materials and molecular sieves [1]. Since the discovery of the microporous crystalline aluminophosphates AlPO4-n in 1982[2], a large number of new metal phosphates with open-framework structures have been synthesized [3][4][5][6][7]. These structures contain not only tetrahedrally coordinated atoms but also square pyramidal and octahedral moieties. Among the vast family of open-framework metal phosphates, the transition metal phosphates constitute an important group due to their potential activity as redox catalysts. Out of all the open-framework compounds known, those based on the phosphate oxoanion appear to be the predominant class [8][9][10]. In addition to the use of tetrahedral phosphate groups as building units, other anionic moieties such as borates [11] . In addition, epoxides, produced by the oxidation of olefins, are extremely useful building blocks in the synthesis of organic compounds as they act as excellent intermediates that can yield a great variety of products [27]. When using vanadyl compounds, the catalytically active oxo-peroxo intermediate is formed in situ by oxidation of V(IV) to V(V) with an excess of tert-butyl hydroperoxide, yielding a tert-butyl hydroperoxovanadium(V) complex.In most of the methods described in the literature, pollutants are generated, because of the use of corrosive acids, toxic or dangerous substances [25]. For this reason it is important to develop clean methods which allow obtaining the sulfoxide derivatives and the epoxides without the generation of these undesired substances. In this sense, the use of hydrogen peroxide instead of other oxidants for the oxidation of organic substrates is an interesting alternative because the unique subproduct of the reaction is water. In addition, hydrogen peroxide is highly efficient in its oxygen content and is a cheap reagent.
4The use of open framework phases templated with amines as catalysts in these reactions is especially appealing due to their redox properties, including their acidity [22,23,28,29].During the course of our research, we have synthesized two new catalytic compounds, fluoro- was added dropwise, while the overall suspension was heated at 323...