Structure and asymmetric epoxidation reactivity of chiral Mn(iii) salen catalysts modified by different axial anions

Abstract

A series of chiral Mn(III) catalysts [salen–Mn(III)][X] (X⁻ = Cl⁻, OAc⁻, NO₃⁻, BF₄⁻, CF₃SO₃⁻, OCH₂CH₃⁻) were synthesized by ion exchange. The influence of the axial anion on both the electronic structure and steric configuration of [salen–Mn(III)][X] were carefully investigated. Besides, the reactivity and enantioselectivity of these catalysts were explored in the asymmetric epoxidation of olefins. The obtained results indicate that the axial anions have influences on both electronic structure and steric configuration of the chiral Mn(III) salen complexes. Controlling the reactivity and enantioselectivity of these chiral Mn(III) salen complexes can be achieved by changing the axial anions.