Fast reactions at planar four-co-ordinate complexes. Part 5. The solvent effect on the leaving group in the reactions of neutral and cationic palladium(II) complexes

Abstract

The rate of replacement of the group X by n-propylamine or thiourea in the substrates [Pd(3-NHpd)X]NO₃(3-NHpd = 3-azapentane-1,5-diamine; X = Cl, Br, I, N₃, SCN, or NO₂) and the equilibrium constants of some of these reactions have been studied in the solvents methanol, dimethylformamide, and dimethyl sulphoxide at 25 °C. The kinetics of substitution of the first group X, by ethylenediamine, in the substrates [Pd(L–L)X₂][L–L = 1, 10-phenanthroline, 1,2-bis(diphenylphosphino) ethane, or ethylenediamine] in dimethylformamide and in some cases in methanol, at 25 °C, have also been followed. Both rate and equilibrium constants vary sensibly on going from protic to dipolar aprotic solvents. The lability sequence of the leaving group depends on the nature of the substrates and in all cases is affected to a large extent by the change in the solvent nature.