Migratory Transmetalation in Diphenoxo-Bridged Cu^IIM^II Complexes of a Dinucleating Macrocycle with N(amine)₂O₂ and N(imine)₂O₂ Metal-Binding Sites

A phenol-based heterodinucleating macrocycle (H2L), comprised of two 2-((methylamino)methyl)-6-(iminomethyl)-4-bromophenolate entities bridged by the −(CH2)2− groups between amine nitrogens and by the −(CH2)3− groups between imine nitrogens, displays dissimilar N(amine)2O2 and N(imine)2O2 metal-binding sites sharing the phenolic oxygens and is prepared as a Cu(II)Pb(II) complex [CuPb(L)](ClO4)2. An analogous complex [CuPb(L)(BzO)(dmf)]ClO4 crystallizes in the triclinic space group P1̄, (No. 2), with a = 13.998(2) Å, b = 15.568(2) Å, c = 8.699(2) Å, α = 95.32(1)°, β = 92.23(1)°, γ = 82.81(1)°, V = 1871.9(5) Å3, and Z = 2. Refinements based on 3788 reflections with I > 3.00σ(I) converged with R = 0.058 and Rw = 0.069. The Cu(II) resides at the N(imine)2O2 site and assumes a planar geometry. The Pb(II) resides at the N(amine)2O2 site and assumes a seven-coordinate geometry by further addition of a dmf molecule and a bidentate benzoate group. The Cu--Pb separation, doubly bridged by the phenolic oxygens, is 3.466(2) Å. The reaction of [CuPb(L)](ClO4)2 with metal(II) sulfate salts provides CuIIMII complexes [CuM(L)](ClO4)2·nH2O (M = Mn (n = 2), Co (n = 2), Ni (n = 0), Cu (n = 0), Zn (n = 1)). The CuZn complex, [CuZn(L)(AcO)]ClO4, crystallizes in the triclinic space group P1̄, (No. 2), with a = 12.290(3) Å, b = 13.402(4) Å, c = 11.501(2) Å, α = 95.10(2)°, β = 116.68(2)°, γ = 112.00(2)°, V = 1491.8(9) Å3, and Z = 2. Refinements based on 2497 reflections with I > 3.00σ(I) converge with R = 0.046 and Rw = 0.034. The Cu(II) is bound at the N(amine)2O2 site and the Zn(II) is bound at the N(imine)2O2 site with a Cu--Zn separation of 2.942(2) Å. Further, the acetate group bridges the two metal ions providing a five-coordinate geometry about both metal ions. The CuM complexes except for the CuZn complex show significant antiferromagnetic spin-exchange within each dinuclear unit. The CuNi complex shows the ESR spectrum of the spin-doublet ground state which demonstrates the delocalization of the unpaired electron over the CuNi core.