Towards deeper understanding of multifaceted chemistry of magnesium alkylperoxides

Abstract

Despite considerable progress in the multifaceted chemistry of non-redox-metal alkylperoxides, the knowledge about magnesium alkylperoxides is in its infancy and only started to gain momentum. Harnessing the well-defined dimeric magnesium tert-butylperoxide [(f5BDI)Mg(μ-η2:η1-OOtBu)]2 incorporating a fluorinated β-diketiminate ligand, herein, we demonstrate its transformation at ambient temperature to a spiro-type, tetranuclear magnesium alkylperoxide [(f5BDI)2Mg4(μ-OOtBu)6]. The latter compound was characterized by single-crystal X-ray diffraction and its molecular structure can formally be considered as a homoleptic magnesium tert-butylperoxide [Mg(µ-OOtBu)2]2 terminated by two monomeric magnesium tert-butylperoxides. The formation of the tetranuclear magnesium alkylperoxide not only contradicts the notion of the high instability of magnesium alkylperoxides, but also highlights that there is much to be clarified with respect to the solution behaviour of these species. Finally, we probed the reactivity of the dimeric alkylperoxide in model oxygen transfer reactions like the commonly invoked metathesis reaction with the parent alkylmagnesium and the catalytic epoxidation of trans-chalcone with tert-butylhydroperoxide as an oxidant. The results showed that the investigated system is among the most active known catalysts for the epoxidation of enones.

Fresh Impetus in the Chemistry of Calcium Peroxides

“…There is a spread of Ca−O bond distances ranging from 2.342 to 2.383 Å (Table S6), and the O−O distances [1.340(4) and 1.348( 5) Å] are within the typical range of distances recorded for hydroperoxide moieties and shorter than those observed for well-defined main group metal alkylperoxides. 58,92 Compound 4 is a centrosymmetric dimer possessing two heptacoordinated Ca centers bridged by the peroxide moieties (Figure 1c). Both units in 4 are also seamed by two K + cations interacting with the peroxide oxygen atoms and the flanked aromatic rings.…”