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 bromo-7-oxa-bicyclo[2.2.1]heptane-2,3-dicarbox ylic acid (3 and 4) have been prepared. For cobalt and nickel two type s of complexes are formed: [ML3/4(H2O)3] . H2O and [ML3/4(H2O)2], the latter is thermodynamically more stable. Manganese and copper form onl y complexes [MnL3/4] and [CuL3/4(H2O)2], respectively. The stereochemi cal configuration of the compounds have been deduced from their spectr oscopic and magnetic properties. The metal atoms have been found to be in an octahedral environment. The stability constants of the complexe s have been determined by potentiometric measurements. The thermal dec omposition of the complexes has been studied by thermogravimetry and d ifferential thermal analysis. The complexes of 3 are thermally more st able 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 dicar boxylate anion acts as a tridentate ligand, the other octahedral sites are occupied by three water molecules. The chlorine atoms are not inv olved in the network of hydrogen bonds within the crystal packing.