Versatile Polyoxometalates of Different Structural Dimensionalities for Liquid Phase Catalytic Oxidation

Abstract

Ionic polymolybdate compounds (IPOM) possessing the anions [Mo8O26]4− and [Mo3O10]2−, and cyclohexylammonium (Cy6N) or anilinium (Anil) as organic cations, namely cyclohexylammonium β-octamolybdate dihydrate (1), cyclohexylammonium trimolybdate hydrate (2), anilinium β-octamolybdate dihydrate (3), anilinium trimolybdate tetrahydrate (4) and anilinium trimolybdate dihydrate (5), were synthesized via simple, eco-friendly one-pot routes. New crystal structures of 1, 2 and 5 were discovered. IPOM compounds with different structural dimensionality, density and ratio of the number of terminal oxo groups/molybdenum atoms (n(oxo)/Mo) were developed. The IPOM compounds promoted the epoxidation of biobased olefins such as the fatty acid methyl esters methyl oleate and methyl linoleate with tert-butylhydroperoxide as oxidant, leading to conversions of at least 81% at 4 h, 70 °C and the corresponding epoxides. The reaction scope of applications for the IPOM catalysts covered cyclooctane oxidation.