Kinetics and mechanisms of substitution and ring opening of platinum(II) complexes with N-heterocyclic bases

The kinetics of the substitution reactions of [Pt(diPic(tr))(H2O)] and [Pt( dipic(tr))(L)] where H(2)dipic=2,6-pyridinedicarboxylic acid with the subsc ript ((tr)) denoting its tridendate mode of bonding and L=imidazole, benzim idazole and pyrazole with excess L have been studied in dimethylformamide s olution by UV-Vis spectrophotometry. The reactions show mono- and bi-phasic features depending on the Pt-II substrate. The tridentate dipic ligand tra nsforms to a bidentate one allowing the entry of the second molecule of the N-bases in the course of the reaction. The kinetic study has been substant iated by product isolation, IR and NMR spectral analysis. The reactions fol low normal square-planar substitution mainly in an associative way. Rate pa rameters have been evaluated under different conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.