Mononuclear manganese(III) complex with a monodeprotonated N-(2-pyridylmethyl)iminodiisopropanol ligand: synthesis, crystal structure, and catalytic properties

The reaction of N-(2-pyridylmethyl)iminodiisopropanol (H₂pmidip), sodium azide, and manganese(II) salt in methanol leads to the isolation of a monomeric manganese complex of [Mn(Hpmidip)(N₃)₂]·CH₃OH (1). The structure of 1 has been verified by single crystal X-ray diffractometry. The manganese ion in 1 is bonded with one Hpmidip⁻ as tetradentate and two azido ligands in cis position in which the manganese ion is displayed a distorted octahedral geometry. One of two hydroxyl groups in the coordinated Hpmidip⁻ ligand is protonated, while the other one is deprotonated. The manganese ion is assigned as 3+ oxidation state that verified by bond lengths and bond valence sum. Furthermore, the complex reveals a dimeric structure by O[sbnd]H⋯O hydrogen bonding interactions. 1 exhibited selective and effective catalytic properties for various olefins with moderate yields using m-CPBA (meta-chloroperoxybenzoic acid). The mechanistic studies of 1 for olefin epoxidation have been investigated by the Hammett study, the O[sbnd]O bond cleavage of PPAA (peroxyphenylacetic acid) as a mechanistic probe, and competitive experiments of cis- and trans-2-octene.