Two principally different in their molecular architecture isomeric tetranuclear copper(II) silsesquioxanes, “Globule”-like compound [(PhSiO_1.5)₁₂(CuO)₄(NaO_0.5)₄] (1) and “Sandwich”-like derivative [(PhSiO_1.5)₆(CuO)₄(NaO_0.5)₄(PhSiO_1.5)₆] (2), were synthesized by the partial cleavage of polymeric copper(II) silsesquioxane [(PhSiO_1.5)₂(CuO)]_n by tetraphenylcyclotetrasiloxanolate. The route leading to the formation of either 1 or 2 entirely depends on the nature and composition of the solvent used for this reaction. Thus, the process in an ethanol–1-butanol solution gives compound 1. When a 1,4-dioxane–methanol mixture was used, compound 2 was prepared. The structures and unusual crystal packing of the cages were confirmed by the X-ray studies. It has been found that the reaction of benzene with H₂O₂ in acetonitrile solution at 50 °C catalyzed by 1 requires addition of trifluoroacetic acid (TFA) in low concentration and gives phenol with a turnover number (TON) of 250 after 3 h. The initial reaction rate W₀ linearly depends on the concentration of catalyst 2. The oxidation of 1-phenylethanol to acetophenone with hydrogen peroxide catalyzed by complex 1 in the presence of TFA is not efficient. In contrast, 1 exhibited excellent activity in the oxidation with tert-butyl hydroperoxide (TBHP) in the absence of any acid (the yield of acetophenone was close to the quantitative, TON attained 475 after 2 h). A kinetic study of this reaction led to the conclusion that the process occurs with the participation of radicals tert-BuO˙ produced in the Cu-promoted decomposition of TBHP. The mode of dependence of W₀ on the initial concentration of TBHP indicates the formation of an intermediate adduct between the catalyst 1 and TBHP (characterized by the equilibrium constant K₁ ≈ 2 M⁻¹ for the conditions of conducted experiments) followed by subsequent decomposition of the adduct (k₂ ≈ 0.2 s⁻¹) to generate an intermediate species tert-BuO˙ which induces the alcohol oxidation.