Dinuclear (CoMII)-M-II (M = Pb or Co) complexes having a "Co(salen)" entity in a macrocyclic framework: ligand modulation effect and neighboring metal(II) effect upon oxygenation at the "Co(salen)" center

Dinuclear (CoPbII)-Pb-II and (CoCoII)-Co-II complexes, [CoPb(L)(CH3OH)][ClO 4](2) (L2-=(L-1)(2-) 1 or (L-2)(2-) 2) and [Co-2(L)(CH3CN)(2)][ClO4](2) (L2 -=(L-1)(2-) 3 or (L-2)(2-) 4), have been obtained where (L-1)(2-) is a dinu cleating macrocyclic ligand derived from the [2:1:1] condensation of 2,6-di formyl-4-methylphenol, ethylenediamine, and diethylenetriamine and (L-2)(2- ) is an analogous ligand comprised of 1,1,2,2-tetramethylethylenediamine in stead of ethylenediamine. The macrocycles have a "salen"-like N2O2 metal-bi nding site and a "saldien"-like N3O2 site sharing two phenolic oxygens. Cry stal structures of the complexes 1-4 have been determined by X-ray crystall ography. Complex 1 reacted reversibly with dioxygen in acetonitrile at 0 de grees C to form a peroxo complex [{CoPb(L-1)(CH3CN)}(2)(O-2)][BPh4](2)[ClO4 ](2). 4CH(3)CN . 5.5H(2)O (peroxo-1), whose structure was determined by X-r ay crystallography. The peroxo group assumes a rare mu(3)-1 kappa O,2 kappa O,3 kappa O' binding mode, where one peroxo oxygen bridges the Co and Pb i n one {CoPb(L-1)(CH3CN)} unit whereas the other oxygen is unidentate to the Co in another unit. Complex 3 is very sensitive to dioxygen so as to be ir reversibly oxidized even at -30 degrees C. A (CoCoII)-Co-III complex, [Co-2 (L-1)(AcO)][ClO4](2). dmf . H2O (oxi-3), was isolated by adding sodium acet ate to the oxidized solution. Complexes 2 and 4 are inert toward dioxygen.