Synthesis, characterization and redox properties of novel di-mu-oxo dimanganese complexes and manganese(III) Schiff base systems

The syntheses, spectra, electrochemical, magnetic and catalytic properties of novel di-mu-oxo dimanganese(III,III), (III,IV), and (IV,IV) complexes employing single tetradentate ligands (N;The epr spectra of the III,IV complexes are similar to those observed in related complexes and show the characteristic sixteen line pattern observed for the S;The syntheses, characterization and catalytic properties of novel Mn(III) complexes with Schiff base ligands are also described. The single crystal x-ray characterization for complexes 12, 14 and 15 show they are in pseudo octahedral geometry, the bases of which are occupied by the Schiff base ligands while the axial sites are occupied by water and ethanol, two ethanol, and water and acetonitrile, for complexes 12, 14 and 15, respectively. Complexes 11 and 13 are tetragonal pyramidal, the schiff base ligands occupying the basal sites while the chloride is in the axial position. The six coordinate complexes show a one electron process in the cyclic voltammogram and are selective in catalytic epoxidation of cyclohexene whereas the five coordinate complexes are non selective and exhibit no reversible redox wave in the cyclic voltammogram.;The complexes have also been shown to be powerful electrocatalysts in the IV,IV state. Thus benzyl alcohol has been selectively oxidized to benzaldehyde with yield as high as 100%. Magnetic properties of the III,IV complexes are consistent with a doublet ground state, the observed J values being larger (in magnitude) than those of other reported complexes of this type. The IV,IV complexes have a singlet ground state.