First Oxalate-Bridged Heterobinuclear Co(II)-Mn(III) Complexes: Synthesis and Magnetism

Three novel Co(II)-Mn(III) oxalato heterobinuclear complexes have been synthesized and characterized, namely K[Co(L)(2)Mn(ox)(3)] (L denotes 1,10-phenanthroline (phen), 2,2'-bipyridyl (bpy), 4,4'-dimethyl-2,2'-bipyridyl (Me(2)bpy), respectively), where ox stands for the oxalate dianion. Based on IR, elemental analyses, electronic spectra and ESR, these complexes are proposed to have extended oxalato-bridged structures consisting of manganese(III) ions and cobalt(II) ions, in which each manganese(III) and each cobalt(II) ion has a distorted octahedral environment. The temperature dependance of the magnetic susceptibility for K[Co(bpy)(2)Mn(ox)(3)] and K[Co(Me(2)bpy)(2)Mn(ox)(3)]. 2H(2)O was measured over the range 77 - 300 K and the observed data were simulated by an equation based on the spin Hamiltonian operator (H = -2JS(1) . S-2), giving the exchange integral J = -0.311 cm(-1) or -0.335 cm(-1), respectively. This indicates a very weak antiferromagnetic interaction between Co(II) ion and Mn(III) ion.