Rate constants have been determined for the reaction of [PtCl4]2− with cyanide in water and in 20% and 40% (v/v) methanol, and for the reaction of [Pd(Et4dien)Cl]+ with thiourea in water, in 50% methanol, and in 50% DMSO, in all cases at 298.2K. The solubility of K2PtCl4 has been determined in water and in 20% and 40% methanol; the solubility of [Pd(Et4dien)Cl]Cl has been determined in water, in 20%, 40%, 60%, and 80% methanol, and in 40% and 80% DMSO; again in all cases at 298.2K. From these solubilities, Gibbs free energies of transfer for the [PtCl4]2− and [Pd(Et4dien)Cl]+ ions have been estimated. From these transfer data, published transfer data for cyanide and thiourea, and these and earlier kinetic results, solvent effects on reactivity have been dissected into their initial state and transition state components for the following four reactions: [PtCl4]2− hydrolysis, [PtCl4]2− plus cyanide, [Pd(Et4dien)Cl]+ substitution, and [Pd(Et4-dien)Cl]+ plus thiourea. The patterns thus established are discussed, and compared with those previously obtained for some other reactions of transition metal complexes.