A New Class of Heterobinuclear Complexes: Crystal Structure and Magnetism of Copper(II)‐Nickel(II) Complexes Incorporating Two Different Macrocyclic Ligands

Three novel oxamido‐bridged heterobinuclear copper(II)‐nickel(II) complexes incorporating two different tetraazamacrocyclic compounds were synthesized and characterized by IR, ESR, and electronic spectra. They are of the formulas (CuL¹)Ni(rac‐cth)](ClO)₄₂?H₂O ( 1 ), Cu(L²)Ni(rac‐cth)](ClO₄)₂?0.5 EtOH ( 2 ), and (CuL³)Ni(rac‐cth)](ClO₄)₂?H₂O ( 3 ). L¹, L², and L³ are the dianions of diethyl 5,6,7,8,16,17‐hexahydro‐6,7‐dioxo‐15H‐dibenzoe,n]1,4,8,12]tetraazacyclopentadecine‐13,19‐dicarboxylate, diethyl 5,6,7,8,15,16‐hexahydro‐6,7‐dioxodibenzo1,4,8,11]tetraazacyclotetracine‐13,18‐dicarboxylate, and diethyl 5,6,7,8,15,16‐hexahydro‐15‐methyl‐6,7‐dioxodibenzo1,4,8,11]tetraazacyclotetradecine‐13,18‐dicarboxylate, respectively, and rac‐cth is rac‐5,7,7,12,14,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane. The crystal structures of 1 and 2 were determined by single‐crystal X‐ray analysis. The Ni^II ion is pseudooctahedrally coordinated. The coordination geometry around the Cu^II ion in 2 is slightly distorted square planar, while that in 1 shows significant distortion towards a tetrahedral structure. The temperature dependence of the magnetic susceptibility for 1 and 2 was analyzed by means of the Hamiltonian H? =?2J S? ₁? S? ₂, leading to J=?63.9 and ?67.4 cm^?1 for 1 and 2 , respectively.