ELECTROCHEMICAL REDUCTION OF L-3-METHYL-5-HYDROXY-4-PYRAZOLYL)-1,10-DECANEDIONE - CHARACTERIZATION OF ITS ELECTROGENERATED MONONUCLEAR CO-II, NI-II AND CU-II COMPLEXES - ESR PROPERTIES OF CO-II AND CU-II COMPLEXES

The reductive electrochemistry of yl-3-methyl-5-hydroxy-4-pyrazoly)-1, 10-decanedione (H(2)L(3) = 3) in tetrahydrofuran on a mercury electrod e is reported. Voltammetric, polarographic, coulometric and spectrosco pic data indicate that 3 undergoes an irreversible two-electron reduct ion, generating a transient species that may involve the carbonyl grou ps. This step is followed by a rapid chemical reaction that produces t he stable dianion (L(3))(2-). The electrochemically generated dianion reacts with M(II) trifluoromethanesulfonate to afford the correspondin g (1/1) complexes [Co(II)L(3)], [Ni(II)L(3)] and [Cu(II)L(3)] respecti vely. These complexes have been characterized by spectroscopic (UV-Vis , IR and mass spectroscopies) and electrochemical (polarography) techn iques. ESR studies were carried out on the Co-II and the Cu-II complex es. Determination of the environment of the Co-II and Cu-II ions in ea ch complex was attempted using all the experimental results. [Co(II)L( 3)] is high-spin with a distorted octahedral geometry and [Cu(II)L(3)] has a tetrahedrally distorted square-planar symmetry.