Tetranuclear mixed-metal M(II)2Cu(II)2 complexes derived from a phenol-based macrocyclic ligand having two...

The reaction of N,N'-dimethyl-N,N'-ethylenebis(5-bromo-3-formyl-2-hydroxybenzylaminato)copper(II) with ethylenediamine in aqueous DMF with excess perchloric acid resulted in the [2:2] cyclic condensation of the constituents, providing the dinuclear Cu(II) complex [Cu2(H2R)](ClO4)2. It crystallizes in the monoclinic space group P2(1)/c, with a = 19.603(3) A, b = 13.370(2) A, c = 21.072(3) A, beta = 98.87(1) degrees, V = 5456(1) A3, and Z = 4. The ligand R4- has two N(amine)2O2 and two N(imine)2O2 metal-binding sites sharing two phenolic oxygens, and [Cu2(H2R)](ClO4)2 has the two Cu(II) ions in the N(imine)2O2 sites and two protons in the N(amine)2O2 sites. [Cu2(H2R)](ClO4)2 was converted by neutralization into [Cu2(R)], from which mixed-metal Cu(II)2M(II)2 complexes [Cu2M2(R)Cl4] (M = Co(II), Ni(II), Zn(II)) were derived. [Cu2Co2(R)Cl4]*2CHCl3*H2O crystallizes in the monoclinic space group C2/c, with a = 32.514(3) A, b = 12.246(3) A, c = 19.827(2) A, beta = 126.082(1) degrees, V = 6380(1) A3, and Z = 4. [Cu2Zn2(R)Cl4]*2CHCl3*H2O crystallizes in the monoclinic space group C2/c, with a = 32.53(1) A, b = 12.242(2) A, c = 19.729(9) A, beta = 126.03(3) degrees, V = 6354(4) A3, and Z = 4. The two complexes are isotructural and have a dimer-of-dimers structure with two separated Cu(II)M(II) units. In each dinuclear unit, the Cu(II) is bound to the N(imine)2O2 site and the M(II) is bonded to a phenolic oxygen and two nitrogens of the N(amine)2O2 site. The Cu(II) and M(II) ions are bridged by a phenolic oxygen and an exogenous chloride ion. The Cu(II)2Ni(II)2 complex has a defect double-cubane structure. Cryomagnetic studies for the Cu(II)2Co(II)2 complex indicate an antiferromagnetic spin-exchange interaction within each dinuclear Cu(II)Co(II) unit (J = -9.5 cm(-1) based on H = -2JS(Cu)S(Co)). The Cu(II)2Ni(II)2 complex shows a weak antiferromagnetic interaction between the adjacent Cu(II) and Ni(II) ions (-3.5 cm(-1)) and a weak ferromagnetic interaction between the two Ni(II) ions (+2.0 cm(-1)).