NEW MAGNETICALLY COUPLED BIMETALLIC COMPLEXES AS POTENTIAL BUILDING-BLOCKS FOR MAGNETIC-MATERIALS

The preparation and characterization of the new binucleating ligand, , 5-tetrakis(2-hydroxy-2-methylpropanamido)benzene, H-8[3], and its Co-I II and V-V(O) complexes [PPh4](2)-[Co-III(kappa(4)-3-kappa(4))Co-III], [PPh4](2)[4], and [Et4N](2)[V-V(O)(kappa(4)-3-kappa(4))V-V(O)], [(EtN )-N-4](2)- [5], are described. Both complexes have been characterized by X-ray crystallography, H-1 NMR, IR, and UV/Vis spectroscopy, and by electrochemical and microanalytical analyses. The electrochemical pro perties of [4](2-) and [5](2-) are remarkably similar, each exhibiting two one-electron oxidation processes of similar E-o/; since the VV(O) sites in [5](2-) are d(0), ligand-localized oxidation is implicated f or both compounds. A deep blue vanadium species obtained upon one-elec tron oxidation of [5](2-), [5(I)](-), has a total spin, S-T, of 1/2, a nd its EPR spectrum exhibits a single g = 2 signal at 4 K. These resul ts are consistent with the oxidized vanadium complex, [5(I)](-), as co ntaining the ligand cation radical 3(I), that is [5(I)](-) is best for mulated as [V-V(O)(kappa(4)-3(I)-kappa(4))V-V(O)](-). Isolation and ch aracterization of the dark purple cobalt species, obtained upon one-el ectron oxidation of [4](2-), [4](-), also revealed the presence of the organic radical 3(I).