STRUCTURES AND MAGNETIC-PROPERTIES OF CO(II)CU(II) AND NI(II)CU(II) COMPOUNDS INCORPORATING THE OBP = OXAMIDOBIS(N,N'-PROPIONATO) LIGAND

Two novel bimetallic compounds have been prepared from the copper(II) precursor [Cu(obp)]2-, namely CoCu(obp)(H2O)3.H2O (1) and NiCu(obp)(H2O)5-3.5H2O (2), obp standing for oxamidobis(N,N'-propionato). The crystal structures of 1 and 2 have been solved. Both compounds crystallize in the triclinic system, space group P1BAR. The lattice parameters for 1 are a = 8.642(1), b = 9.197(1), c = 10.645(2) angstrom, alpha = 67.14(1), beta = 62.28(1), gamma = 73.95(1)-degrees, Z = 2. Those of 2 are a = 11.444(1), b = 12.295(1), c = 15.100(2) angstrom, alpha = 68.89(1), beta = 72.94(1), gamma = 76.26(1)-degrees, Z = 4 NiCu units. The structure of 1 consists of bimetallic chains in which the Co(II) and Cu(II) ions are alternately bridged by oxamido and carboxylato groups. In contrast, the structure of 2 consists of isolated oxamido-bridged Ni(II)Cu(II) units. The magnetic properties of both compounds have been investigated and quantitatively. interpreted. In spite of its chain structure 1 does not show the one-dimensional ferrimagnetic behavior. It has been assumed that the interaction through the carboxylato bridged was very small. The magnetic data have been fitted with a model taking explicitly into account the orbital degeneracy of the Co(II) ion in a weak octahedral field. The magnetic behavior of 2 is in line with its structure with a strong intramolecular antiferromagnetic interaction between the spin carriers. Finally, the J(MnCu), J(CoCu) and J(NiCu) interaction parameters through the oxamido bridge in related compounds have been compared.