Oxygenation of heterodinuclear di(μ-phenoxo) Co(II)M(II) (M = Mn, Fe or Co) complexes having a "Co(salen)" entity in a macrocyclic framework

Heterodinuclear di(mu-phenoxo) (CoMII)-M-II complexes [CoM(L)(AcO)]ClO4 (M=Mn 1, Fe 2 or Co 3) and [CoM(L)(NCS)]ClO4 (M=Mn 4, Fe 5 or Co 6) have been obtained where L2- is a heterodinucleating macrocycle derived by the 2:1:1 condensation of 2,6-diformyl-4- methylphenol, ethylenediamine and diethylenetriamine and has a "salen"-like N2O2 metal-binding site and a "saldien"-like N3O2 site sharing the phenolic oxygens. The CoM(AcO) complexes 1 and 3 show reversible oxygenation at 0 degrees C in dmf, whereas 2 is irreversibly oxidized under the same conditions. The structures of the dioxygen adducts of 1 and 3 have been determined by X-ray crystallography. In that of 1, [{CoMn(L)(AcO)}(2)(O-2)][ClO4](2). 4CH(3)CN oxy-1, the Co resides in the "salen" site and the Mn in the "saldien" site. An exogenous acetate group bridges the two metal ions in the eta(1):eta(1) mode together with the two phenolic oxygens. The peroxo group bridges two {CoMn(L)(AcO)} molecules at the Co forming a Co-O-O-Co linkage. The peroxo O(1)-O(2) bond distance is 1.416(5) Angstrom and the Co(1)... Co(2) intermetallic separation is 4.359(1) Angstrom. The geometry about the Co is pseudo octahedral with a peroxo oxygen and an acetate oxygen at the axial sites and the Mn has a distorted six-co-ordination. The dioxygen adduct of 3, [{Co-2(L)(AcO)}(2)(O-2)][ClO4](2). 4CH(3)CN oxy-3, is isomorphous with oxy-1: the peroxo O(1)-O(2) bond distance is 1.415(4) Angstrom and the Co(1)... Co(3) intermetallic separation is 4.3527(8) Angstrom. Within the CoM(NCS) complexes 4-6, 4 shows reversible oxygenation at -30 degrees C, whereas irreversible oxidation is observed for 5 and 6.