Kinetics of aquation of penta-amminechlororuthenium(III) dichloride and cis-dichlorobis(ethylenediamine)ruthenium(III) chloride hydrate in mixed water–organic solvents

Abstract

Kinetic data are reported for the spontaneous aquations of [Ru(NH3)5Cl]Cl2 and cis-[Ru(en)2Cl2]Cl in a variety of mixed water–organic solvents. Plots of log kH2O against Grunwald–Winstein Y values are linear with gradients ca. 0.25, suggesting essentially SN1 mechanisms. The Hg2+-catalysed aquation of [Ru(NH3)5Cl]2+ has also been studied in both aqueous solution and in a variety of mixed water–organic solvents. Kinetic data in aqueous solution are consistent with pre-equilibnum formation of a chloro-bridged intermediate, [(NH3)5Ru–Cl–Hg]4+, followed by dissociation to release [HgCl]+ and the rapid pick up of water. Plots of log kHg2+ against Y values for the Hg2+-catalysed aquation in mixed solvents are markedly non-linear. This unusual behaviour is discussed in terms of the pre-equilibrium mechanism.