ACID-BASE EQUILIBRIA OF COORDINATED LIGANDS .1. THE EFFECT OF BASICITY OF COORDINATED NITROGEN DONORS UPON THE ACIDITY OF CHELATING 8-AMINOQUINOLINE IN SOME DICATIONIC PLATINUM(II) COMPLEXES

Cationic complexes of the type [Pt(8NH2-quin)L2][ClO4]2 and (Pt(8NH2-q uin)(L-L)][ClO4]2 (8NH2-quin = 8-aminoquinoline), where L and L-L are mono- and bi-dentate nitrogen donors respectively, have been prepared. In aqueous solution, they undergo reversible deprotonation of the ami no group of the quinoline ligand. The corresponding ionization constan ts (K(a)c) have been determined by UV/VIS spectrophotometry at 25-degr ees-C and I = 0.1 mol dm-3. The linear free-energy relationship pK(a)c = alpha + betapK(a)L is verified for the para-substituted pyridines, pK(a)L referring to the basicity of L in water at 25-degrees-C.