On the Magnetic behaviour of Tetrakis|2-Diethylamino- Ethanolato-/i3-0-Copper(II)-Isocyanate| • Trichloromethane, C28H56CU4N808 • CHCI3, a Tetrameric Copper(II) Complex with Antiferromagnetic Ground State

Tetrameric copper(II) complexes of cubane type show the effect of plasticity: The geometry of the magnetically active Cu 4 0 4 -core varies in a wide range caused by different ligands. Mergehenn and Haase [1] classified these complexes geometrically: Type I complexes can be described as two slightly coupled dimers while type II complexes are chairlike. Between these types there is a continuous transition in the molecular arrangement of the Cu 40 4-core. Such complexes will be considered as "transition type complexes". An interpretation of the magnetic behaviour of tetrameric copper(II) complexes can be given by the isotropic Heisenberg-Dirac-van Vleck (HDvV) model, which allows one to calculate the magnetic exchange integrals. Type I complexes indicate dominating antiferromagnetic spin coupling, whereas type II complexes show dominating ferromagnetic interaction. In the transition type complexes antiferromagnetic and ferromagnetic interactions are in the same order of magnitude. Till now only transition type complexes with antiferromagnetic ground state are known. Recently we have reported the crystal and molecular structure of the title com-