A heterometallic (Fe6Na8) cage-like silsesquioxane: synthesis, structure, spin glass behavior and high catalytic activity

Abstract

The exotic “Asian Lantern” heterometallic cage silsesquioxane [(PhSiO_1.5)₂₀(FeO_1.5)₆(NaO_0.5)₈(n-BuOH)_9.6(C₇H₈)] (I) was obtained and characterized by X-ray diffraction, EXAFS, topological analyses and DFT calculation. The magnetic property investigations revealed that it shows an unusual spin glass-like behavior induced by a particular triangular arrangement of Fe(III) ions. Cyclohexane and other alkanes as well as benzene can be oxidized to the corresponding alkyl hydroperoxides and phenol, respectively, by hydrogen peroxide in air in the presence of catalytic amounts of complex I and nitric acid. The I-catalyzed reaction of cyclohexane, c-C₆H₁₂, with H₂¹⁶O₂ in an atmosphere of ¹⁸O₂ gave a mixture of labeled and non-labeled cyclohexyl hydroperoxides, c-C₆H₁₁–¹⁶O–¹⁶OH and c-C₆H₁₁–¹⁸O–¹⁸OH, respectively, with an ¹⁸O incorporation level of ca. 12%. Compound I also revealed high efficiency in the oxidative amidation of alcohols into amides: in the presence of complex I, only 500 ppm of iron was allowed to reach TON and TOF values of 1660 and 92 h⁻¹.