Dioxomolybdenum(VI) complexes containing chiral oxazolines applied in alkenes epoxidation in ionic liquids: A highly diastereoselective catalyst

New monometallic dioxomolybdenum complexes, 2 and 3, containing the bis(oxazoline) B and the oxazolinyl-pyridine C respectively, have been prepared and fully characterized both in solution and solid state, including the single-crystal X-ray diffraction analysis for 2, which represents the first structure of a Mo(VI) complex coordinated to a bis(oxazoline). These complexes, together with the bimetallic system 1, were used as catalytic precursors for alkenes epoxidation (cyclooctene, (R)-limonene, trans-β-methylstyrene) in imidazolium- and pyrrolidinium-based ionic liquids, exhibiting a high chemoselectivity towards the epoxide formation, mainly for cyclooctene and (R)-limonene epoxidation, without formation of the corresponding diols. In [BMP][NTf2] (BMP = butyl methyl pyrrolidinium; NTf2 = bis(trifluoromethanesulfonyl)amide), complex 1 exclusively gave trans(R)-limonene 1,2-epoxide, while monometallic catalytic systems led to a low diastereoselectivity. 95Mo NMR studies helped to understand the catalytic behaviour of 1 and 2 in ionic liquid medium.

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► Dioxomolybdenum(VI) complexes applied in alkenes epoxidation in ionic liquids.
► Pyrrolidinium-based ionic liquid leads to stable oxazoline-based catalytic systems.
► Diastereospecific bimetallic catalyst in pyrrolidium-based ionic liquids.
► 13C and 95Mo NMR studies evidence Mo-NHC bond formation in imidazolium IL.