Preparation, structures and properties of manganese complexes containing amine–(amido or amidato)–phenolato type ligands

Abstract

Complexation of 2-hydroxy-N-(n-aminoalkyl)benzamides, where n-aminoalkyl substituents are 2-amino-2-methylpropyl (H2L2Me2), (R)-2-aminopropyl {(R)-H2L2Me} and 3-aminopropyl (H2L3), with manganese(II) chloride or perchlorate were examined. With the 2-aminopropyl derivatives, dinuclear methoxido-bridged manganese(III) complexes bearing the dianionic ligands, [{Mn(L2Me2 or (R)-L2Me)(MeOH)}2(μ-OMe)2] (2 or 4), were isolated and their crystal structures were determined. There was a weak antiferromagnetic interaction between two axially distorted MnIII centers in 2. Also, with the ligand of (L2Me2)2− a mononuclear manganese(IV) complex, [Mn(L2Me2)2]·DMF (3·DMF) was obtained. In the crystal of 3·DMF a heterochiral dimerization via the intermolecular double hydrogen-bonds was observed. In the case of reactions with H2L3, mononuclear manganese(III) complexes, [Mn(H2L3′)2Cl2]Cl (6) and [Mn(H2L3′)2(MeOH)2]Cl2(ClO4) (7), were afforded, where the ligand (H2L3′) has a phenolate–amide–ammonium type zwitterionic form of H2L3 and coordinates to a MnIII center via the phenolato-O and amide-O atoms to form a six-membered chelate ring. Furthermore, a tetranuclear MnII2MnIII2 double incomplete-cubane type cluster compound, [Mn4(HL3)2Cl2(OMe)6(MeOH)2]·4MeOH (5a·4MeOH) was revealed by the single-crystal X-ray diffraction study, although the bulk crystals (5) obtained from the reaction mixture showed a different PXRD pattern. The elemental analysis of the bulk crystals of 5 suggested that they consist of the same tetranuclear clusters. It is interesting that the bulk crystals of 5 were highly efflorescent, and it was suggested that their coordinated MeO− and MeOH ligands were easily substituted by OH− and H2O, respectively, in atmospheric air. This conversion changed their magnetic behaviors drastically.