Quinoline-based tetradendate nitrogen ligands stabilize the bis(μ-oxo) dinuclear manganese(III,III) core

Quinoline-based, tetradentate nitrogen ligands, NN'-bis(2-quinolylmethyl)-NN'-dialkyl-1,2ethanediamine (alkyl = methyl, bqdmen; ethyl, bqdeen; isopropyl, bqdpen), have been investigated as the supporting ligands for the formation of bis(mu-oxo) dinuclear manganese complexes. Bis( mu-oxo)Mn-2(III,III) complexes 1 and 2 were obtained for bqdmen and bqdeen, respectively, as evidenced by X-ray crystallography, whereas bqdpen did not afford any manganese complexes due to its steric bulk. Complexes 1 and 2 exhibit highly positive Mn-2(III,III)/Mn-2(III,IV) and Mn-2(III,IV)/Mn-2(IV,IV) redox couples relative to the corresponding pyridine-ligated (mu-O),Mn-2(III,III) complexes.