First structurally characterized optically active mononuclear Mn(IV) complex: Synthesis, crystal structure and properties of [Mn < inf > IV < /inf > L < inf > 2 < /inf > ] {H < inf > 2 < /inf > L = 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.