SYNTHESIS, SPECTROSCOPIC AND STRUCTURAL CHARACTERIZATION OF THE MER ISOMER OF AMMONIUM BIS(PHENYLPYRUVIC ACID THIOSEMICARBAZONE)-COBALT(III) HEMIHYDRATE

Phenyl pyruvate thiosemicarbazone (H2PPVATSC) coordinates in its bineg ative thiolate form to cobalt(III) in the complex isolated from basic medium. An X-ray structure determination of the resulting meridional i somer was found to contain mutually cis sulphur, trans nitrogen, and t rans oxygen donor atoms, respectively. The two five-membered rings for med by each ligand are puckered towards each other, resulting in a dis tortion from regular octahedral geometry about the cobalt atom. The co mplex was found to exhibit only a metal-based one electron reversible reduction at - 0.97 V, while the parent ligand yields a c.v. profile c onsisting of two irreversible reduction peaks at - 0.75 and - 1.05 V r espectively, the latter corresponding to the reduction of the azomethi ne group.