Cu2+-Mediated Nucleophilic Addition of Different Nucleophiles to Dicyanamide - Synthesis, Structures, and Magnetic Properties of a Family of Mononuclear, Trinuclear, Hexanuclear, and Polymeric Copper(II) Complexes

Five new copper(II) complexes have been isolated from the reaction system of Cu-II/N(CN)(2)-/HNu (HNu = pyrazole or MeOH) by Cu2+-mediated in situ nucleophilic additions of methanol or pyrazole to dicyanamide; they are [Cu-(HdcadMeOH)(2)](ClO4)(2 center dot)2H(2)O (3), [Cu(dCa)(2)(3-nic)(2)](n)center dot (HdcaMeOH)(2n) (4), [Cu(dcapz)(dcadMeOH)] (5), [Cu-3-(dcadpz)(2)(HpZ)(2)(MeCN)(2)] (ClO4)(2)(NO3)(2) (6), and [Cu-6-(dcadpz-2H)(2)(mu-pz)(6)] (7) [HdcadMeOH = bis(methoxycarbimido)amine, HdcaMeOH = (methoxycarbimido)cyanoamine, dcadMeOH(-) = bis(methoxycarbimido)aminato, dcapz(-) = (pyrazolecarbimido)cyanoaminato, dcadpz(-) = bis-(pyrazolecarbimido)aminato, Hpz = pyrazole, 3-nic = nicotinamide]. X-ray crystallography revealed that 3 and 5 are mononuclear complexes, 6 is a trinuclear complex, 7 is a cyclic hexanuclear cluster, whereas 4 is composed of neutral one-dimensional [Cu(mu(1),(5)-dca)(2)(3-nic)(2)](n) coordination chains with HdcaMeOH guest molecules located between these chains. In the five complexes, the 1:1 and 1:2 nucleophilic addition reactions occurred between dca(-) and methanol or pyrazole molecules under controlled conditions. In complexes 3, 5, 6, and 7, the addition products generated in situ act as bridging or chelating ligands, whereas in compound 4 the addition product acts as the guest molecule. The magnetic properties of complexes 6 and 7 were studied by variable-temperature magnetic susceptibility and magnetization measurements. In 6, significant ferromagnetic coupling exists between the three S = 1/2 spins within the Cu-3 unit through the dcadpz(-) bridges, whereas in 7, strong antiferromagnetic couplings exist between the neighboring copper ions through the [dcadpz-2H](3-) and pz(-) bridges with an intratrimer exchange interaction of -250.6 K and an intertrimer coupling interaction of -69.1 K. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)