CHELATE COMPLEXES OF MANGANESE(II) - SYNTHESIS, SPECTROSCOPIC AND ELECTRON-PARAMAGNETIC RESONANCE PROPERTIES OF MANGANESE(II) BETA-DIKETONATE DERIVATIVES

The results of e.s.r. vibrational and electronic investigations were compared in order to describe the ligand field properties, the charge distribution and the nature of the chemical bonds in the adducts of bis-(2,4-pentanedionato)manganese(II) (Mn(pd)2) with basic molecules. E.s.r data are suitable to describe axial and rhombic distortions caused by the additional base molecules. Phenanthroline, pyrazine and ethylenediamine give rise to axial distortion; dipyridyl, pyridine, 4-Mepyridined, quinoline, quinoxaline, water to rhombic distortion. Both the steric hindrance and the electronic properties of the additional base ligand contribute to the distortion; however the electron-withdrawing power of the base decides the distortion weight. Intermolecular interaction in Mn(pd)2 and in the adduct with pyrazine have also been considered by the e.s.r. data. The manganese-pentanedionato bond properties and the bond strength internal to pentanedionato have been discussed by the i.r. ata, in the light of the metal electronic structure of the π acceptor properties of the additional base; the competition between pentanedionato and the additional base, as for the π acceptor power, is favourable to the pentanedionato ligand. © 1979.