PREPARATION, CHARACTERIZATION AND REDOX PROPERTIES OF O,O'-GEOMETRICAL ISOMERS OF MU-ALPHA AND MU-BETA-AMINOISOBUTYRATO CO(II) COMPLEXES WITH 2-PYRIDYLMETHYL)-1,4,8,11-TETRAAZACYCLOTETRADECANE

Two new dinuclear cobalt(II) complexes which, besides macrocyclic liga nd N',N',N '',N'''-tetrakis (2-pyridylmethyl)-1,4,8,11-tetraazacyclo ( tpmc) contain alpha- or beta-aminoisobutyrato ions (alpha-aibu(-) and beta-aibu(-), respectively) were synthesized. The complexes having gen eral formula [Co-2(aibu)tpmc](ClO4)(3) were characterized by elemental analysis, electronic and IR spectroscopy, magnetic measurements and c yclic voltammetry. it was assumed that in both complexes an exo coordi nation of the macrocyclic ligand is achieved. Cobalt(II) ions are brid ged with O,O'-aminoisobutyrato ligand. Both complexes are stable again st air oxidation, whereas the oxidation of the complex containing the alpha-aibu(-) ion by hydrogen-peroxide gave the corresponding mixed-va lence Co-II/Co-III complex. The complexes are also electrochemically s table in the potential range from-0,6V to 0,4V vs SCE.