Transition-metal complexes of biuret and related ligands. Part II. Magnetic properties of copper(II)–biuret complexes
Abstract
The temperature-dependence of the magnetic susceptibility (between 80 and 295°K) has been examined for three copper(II)–biuret complexes. The complexes Cu(NH2·CO·NH·CO·NH2)2Cl2 and K2[Cu(NH·CO·NH·CO·NH)2], 4H2O obey the Curie–Weiss law with values of θ equal to –20°± 2° and –5°± 2°, respectively. The complex K2{[Cu(NH·CO·NH·CO·NH)·OH]2},4H2O does not exhibit Curie–Weiss behaviour and an equilibrium between singlet and triplet states has been assumed. Enthalpy and entropy changes associated with it are discussed.