Nucleophilic displacement of halides from dihalogenoplatinum(II) complexes containing a chelating thioether. Kinetics and equilibria

Abstract

Kinetic and equilibrium measurements on the displacement of halides from the substrates [Pt(PhSCH₂CH₂SPh)X(Y)](X, Y = Cl, Cl; Cl, Br; Br, Br; Br, I; I, I; Cl, I) with the nucleophiles Cl^–, Br^– and I^– have been carried out in methanol at 25 °C, I= 0.5 mol dm^–3(LiClO₄). The results are discussed in terms of the relative stability of the planar ground and five-co-ordinate transition states, and the lability and kinetic cis effects of co-ordinated halides are compared. All substrates appear to be characterized by a sort of stereoelectronic hindrance leading to retardation effects, mainly in the second-order substitution pathway.