First structurally characterized optically active mononuclear Mn(iv) complex: synthesis, crystal structure and properties of [MnivL2] {H2L = S-(−)-2-[(2-hydroxy-1-phenylethylimino)methyl]phenol}

Abstract

The reaction of Mn(CH₃COO)₂·4H₂O with H₂L {H₂L = S-(−)-2-[(2-hydroxy-1-phenylethylimino)methyl]phenol} in the presence of air afforded dark brown crystals of [Mn^IVL₂], 1. Compound 1 crystallizes in the monoclinic chiral C2 space group. Crystals of 1 were further characterized by elemental analysis, room temperature magnetic moment determination, IR, UV-visible and EPR spectroscopy, cyclic voltammetry and circular dichroism (CD) studies. Cyclic voltammetry reveals a quasi-reversible redox wave corresponding to the Mn(IV)/Mn(III) couple. The EPR spectrum at liquid nitrogen temperature consists of a strong signal at g ∼ 4 and a weak but resolved response at g ∼ 2. The CD spectrum of 1 exhibits a negative band, such as shown by the enantiopure ligand H₂L. Complex 1 was found to catalyze the oxidation of olefins using iodosobenzene as the oxidant in acetonitrile solutions.