State and kinetic stability of the complex of scandium(III) with octaphenyltetraazaporphine in proton-donor media

The state of scandium(III) octaphenyltetraazaporphine with an acetate extra ligand in proton-donor media, HOAc-benzene, HOAc-antipyrine-H2SO4, and HOA c-H2SO4, was studied by spectrophotometry. It was shown that in media with Hammett acidity functions of 6.26-1.84 an ion-ion associate is formed by on e of the meso-nitrogen atoms. The stability constant of the ion-ion associa te was determined (pK(s1) 3.95). In higher acidity media (H-0 > 1.84) the i on-associate undergoes solvoprotolytic dissociation to give the octaphenylt etraazaporphyne ligand protonated by one of the meso-nitrogen atoms. The ki netic stability of the scandium complex in HOAc-H2SO4 and H2O-H2SO4 solutio ns was studied. Kinetic parameters of the solvoprotolytic dissociation of t he complex were determined and some speculations on the reaction mechanism were made.