Electronic transmission in trans-bis(1,2-dioximato)cobalt(III) complexes with organic bases—deprotonation reaction

Abstract

The p K a values for the deprotonation reaction of intramolecular hydrogen bridges of trans-[Co(dmgH) 2 B 2] +, where dmgH is the dimethylglyoximate monoanion and B aniline, pyridine or their derivatives, have been determined spectrophotometrically. With increasing the electron-donor power of B the p K a values are increased. The axial pyridine derivatives decrease the p K a values of the complexes much more than the axial aniline derivatives. This characteristic behavior of the axial pyridine ligand has been observed in a series of the Co(III) complexes with methylethylglyoxime, cyclohexanedionedioxime and α-benzildioxime. In the complexes with B = pyridine derivatives, the additional formation of Co- B π-interaction has been postulated: the π-interaction may display a role withdrawing electron toward B and increasing the residual positive charge on the cobalt ion with a concomitant decrease of the electron density on the oxime groups.