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

Abstract

AbstractFive new copper(II) complexes have been isolated from the reaction system of CuII/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)2·2H2O (3), [Cu(dca)2(3‐nic)2]n·(HdcaMeOH)2n (4), [Cu(dcapz)(dcadMeOH)] (5), [Cu3(dcadpz)2(Hpz)2(MeCN)2](ClO4)2(NO3)2 (6), and [Cu6(dcadpz‐2H)2(μ‐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(μ1,5‐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 Cu3 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)