Synthesis, structure and magnetic properties of a trinuclear cyano-bridged complex [Cu(bappz)(μ-NC)Ni(CN)2(μ-CN)Cu(bappz)](ClO4)2 {bappz=1,4-bis(3-aminopropyl)piperazine}

The bimetallic trinuclear complex [Cu(bappz)(μ-NC)Ni(CN)2(μ-CN)Cu(bappz)](ClO4)2 (bappz=1,4-bis(3-aminopropyl)piperazine) has been prepared from the reaction of [Cu(bappz)](ClO4)2 and K2[Ni(CN)4] in water and its crystal and molecular structure has been determined. The structure consists of a trinuclear [Cu(bappz)(μ-NC)Ni(CN)2(μ-CN)Cu(bappz)]2+ cation and two perchlorate anions. The bridging [Ni(CN)4]2− anion is coordinated by two [Cu(bappz)]2+ cations through two cyano groups, providing a novel trinuclear structure with the Cu–(NC)–Ni–(CN)–Cu linkage. The nickel(II) ion is four-coordinated by carbon atoms from four cyano groups (two of them, in trans position, form a bridge) in a square planar arrangement, whereas both the copper(II) ions are five-coordinated by four bappz nitrogens and one cyanide nitrogen in a distorted square–pyramidal geometry. The temperature dependence of magnetic susceptibility was measured for this compound over the range of 2–300 K. The magnetic investigation showed the presence of a very weak antiferromagnetic interaction (superexchange interaction parameter J=−0.54 cm−1) between the copper atoms through the diamagnetic [Ni(CN)4]2− ion.