The polyhedral oligomeric silsesquioxane trisilanolate vanadium(V) complex 1 efficiently catalyzes oxidations at room temperature using cumyl hydroperoxide as the terminal oxidant. Sulfoxidations and N-oxidations have been carried out yielding the corresponding products in good yields. The addition of a Lewis base as a coligand can markedly affect reactivity, stability, and chemo- and stereo-selectivity. A proposal for the intermolecular activation, using Gutmann analysis supported by MP2/TZVP calculations, is presented.