A structurally characterized monomeric Mn(IV) complex in a discrete N2O4 coordination environment

From the reaction of Mn(III)OAc3 with (3,5-dibutyl-2-hydroxyphenylmethyliminomethyl)3,5-dibutyl phenol (H2dbpip) in acetonitrile, dark brown crystals of compound Bis[(3,5-dibutyl-2-hydroxyphenylmethyliminomethyl)3,5-dibutylphenalato]manganese (IV), Mn(IV)(dbpip)2 (1) were obtained upon slow evaporation of the solvent. The structural assignments of 1, that were made in part by elemental analysis and magnetic susceptibility, were confirmed by single crystal X-ray diffraction studies which revealed that compound 1 crystallizes in the monoclinic, space group C2/c with a cell dimensions a=49.746(8) Å, b=12.682(2) Å, c=19.497(3) Å, α=90°, β=94.240(3)°, γ=90°. Cyclic voltammetry reveals a quasireversible redox wave corresponding to the Mn(III)/Mn(IV) couple. The EPR spectrum at 4 K consists of strong and weak signals near g=2 and 4, respectively. A comparison of the EPR spectrum to there obtained for other Mn(IV)N2O4 complexes reveals that 1 is a rare example of an axial Mn(IV) species with D≪hν.