Displacement of chelate ligands from planar four-co-ordinate complexes. Part 5. Preparation and ligand-substitution reaction of di-chloro(ethylenediamine)- and dichloro(propylenediamine)-gold(III) complexes

Abstract

The displacement of the chelate ligand (N–N) from the title complexes [Au(en)Cl₂]⁺ and [Au(pn)Cl₂]⁺ has been studied in a hydrochloric acid medium, I= 1.7 mol dm^–3, using aqueous methanol (95%) or water as solvent. The reaction takes place in two stages: an initial equilibrium between singly and doubly co-ordinate diamine is established, followed by displacement of the singly bonded protonated ligand from the metal. The rate constants for opening of the chelate ring and displacement of the half-detached ligand, and the quotient of the rate constant for ring closure and the basicity constant of the half-bonded diamine, have been determined. Comparison is made with data for displacement of analogous ligands from complexes of Pd^II and Pt^II.