A Heterodinuclear CoIICuI Complex with Co(salen) in a Macrocyclic Framework. Oxygenation Studies in Comparison with Analogous CuIICuI and CoIIPbII Complexes

A di(μ-phenoxo)Co II Cu I complex, [CoCu(L)]ClO 4 ·0.5DMF, has been prepared where (L) 2 - is a macrocyclic dinucleating compartmental ligand derived from the 2:1:1 condensation of 2,6-diformyl-4-methylphenol, ethylenediamine, and 3-thia-1,5-pentanediamine, having a salen-like N 2 O 2 metal-binding site (salen = N, N ‘-ethylenedisalicylideneaminate) and an N 2 O 2 S site sharing the phenolic oxygens. It crystallizes in the monoclinic space group P 2 1 / n, a = 7.087(1) Å, b = 19.593(6) Å, c = 19.447(3) Å, β = 96.29(1)°, V = 2684(1) Å 3, and Z = 4. The Co II resides in the salen-like site and assumes a planar geometry. The Cu I in the N 2 O 2 S site has a planar four-coordinate geometry with two phenolic oxygens and two imine nitrogens; the thioether sulfur on the lateral chain is situated at an axial site of the Cu I, but the Cu--S separation is very large (3.08 Å). In the {CuN 2 O 2 } chromophore, the two Cu−O bond distances (2.333(5) and 2.385(5) Å) are significantly long relative to the two Cu−N bond distances (1.984(6) and 1.929(4) Å). Further, the N−Cu−N angle is very large (128.2(2)°), whereas the O−Cu−O angle is very small (65.2(2)°). Analogous Cu II Cu I and Co II Pb II complexes of (L) 2 -, [Cu II Cu I (L)]ClO 4 and [CoPb(L)](ClO 4 ) 2, have been prepared. The DMF adduct of [Cu II Cu I (L)]ClO 4, [Cu II Cu I (L)]ClO 4 ·0.5DMF, crystallizes in the monoclinic space group P 2 1 / n, a = 6.957(2) Å, b = 23.774(2) Å, c = 7.758(3) Å, β = 94.72(3)°, V = 1278.8(6) Å 3, and Z = 4. The dinuclear core resembles that of the Co II Cu I complex and shows distortions about the Cu I similar to those found for the Co II Cu I complex. The di-DMF adduct of the Co II Pb II complex, [CoPb(L)(DMF) 2 ](ClO 4 ) 2, crystallizes in the monoclinic space group P 2 1 / n, a = 16.265(2) Å, b = 12.640(2) Å, c = 18.584(3) Å, β = 90.43(1)°, V = 3820.5(8) Å 3, and Z = 4. The Co II in the N 2 O 2 site has a square-pyramidal geometry together with a DMF oxygen at the apical site. The Pb II in the N 2 O 2 S site has a six-coordinate geometry with the further coordination of a DMF molecule. The reactivity of the Co II Cu I complex toward dioxygen has been studied in comparison with the Cu II Cu I and Co II Pb II complexes. The Co II Cu I complex in DMF is very sensitive to dioxygen and is oxidized at −50 °C. The Cu II Cu I complex is inert to dioxygen. The Co II Pb II complex is oxygenated at 0 °C to form a peroxo dimer (Pb II Co III −O−O−Co III Pb II ). The high sensitivity of the Co II Cu I complex to dioxygen is explained by the irreversible oxidation to a Co III Cu II species through an intramolecular-type peroxo complex (Co III −O−O−Cu II ).