Nucleophilic substitution reactions at planar four-co-ordinate monoanionic platinum(II) complexes

Abstract

The kinetics of displacement of chloride from complex anions of the type [Pt(4R-pydca)Cl]–(pydca = pyridine-2,6-dicarboxylate; R = H, Cl or OMe) by a number of anionic and neutral nucleophiles have been studied in aqueous solution, at 25.0 °C, I= 0.50 mol dm–3(LiClO4). Apart from the reactions with OH–, the reactivities of the substrates are not greatly sensitive to the nature of the substituent in the 4 position. Anionic nucleophiles can be as much as two orders of magnitude less reactive than neutral nucleophiles with similar n0pt values. The rate law for the reaction with OH– takes the form –dln[substrate]/dt=ks+k3[OH–]2, where ks is the first-order rate constant for the solvolytic pathway observed in all the substitution reactions, and where k3 is sensitive to the basicity of the nitrogen in the terdentate ligand.