COMPLEX-FORMATION OF 5,6-DIHALOGENO-7-OXA-BICYCLO[2.2.1]HEPTANE-2,3-DICARBOXYLIC ACID WITH 3D TRANSITION-ELEMENTS

Carboxylate complexes of bivalent manganese, cobalt, nickel and copper with 5,6-dichloro- and 5,6-dibromo-7-oxa-bicyclo[2.2.1]heptane-2,3-dicarboxylic acid (3 and 4) have been prepared. For cobalt and nickel two types of complexes are formed: [ML3/4(H2O)3] . H2O and [ML3/4(H2O)2], the latter is thermodynamically more stable. Manganese and copper form only complexes [MnL3/4] and [CuL3/4(H2O)2], respectively. The stereochemical configuration of the compounds have been deduced from their spectroscopic and magnetic properties. The metal atoms have been found to be in an octahedral environment. The stability constants of the complexes have been determined by potentiometric measurements. The thermal decomposition of the complexes has been studied by thermogravimetry and differential thermal analysis. The complexes of 3 are thermally more stable than the corresponding ones of 4. The X-ray structure analysis of [CoL3(H2O)3] . H2O shows a monomeric structure of the complex within the crystal and an octahedral coordination of the metal ion. The dicarboxylate anion acts as a tridentate ligand, the other octahedral sites are occupied by three water molecules. The chlorine atoms are not involved in the network of hydrogen bonds within the crystal packing.