Oxidation catalysis with well-characterised vanadyl bis-bipyridine complexes encapsulated in NaY zeolite

Vanadyl exchanged faujasite (VO2+-NaY) allows bipyridine complexation, giving a heterogeneous ''ship-in-a-bottle'' catalyst denoted as [VO(bpy)(2)](2+)-NaY. The [VO(bpy)(2)](2+) complexes associated with the zeolite are characterised with FT-Raman, FT-IR, XPS, and diffuse reflectance spectroscopy (DRS), as well as with electron paramagnetic resonance (EPR). It is established that the cationic complexes are intrazeolitic and homogeneously distributed across the zeolite crystals and both the zeolite and the neutral bipyridine ligands stabilise V-IV. The catalytic oxidation of cyclohexane and cyclohexene with different peroxides or mono-oxygen atom donors in presence of several solvents is described. Good epoxide selectivity results from the complexation by bipyridine thus favoring the heterolytic over the homolytic decomposition pathway of V-peroxo-intermediates.