Hydrolysis study of the bifunctional antitumour compound RAPTA-C, [Ru(η6-p-cymene)Cl2(pta)]

The hydrolysis of [Ru(η6-p-cymene)Cl2(PTA)] (PTA = 1,3,5-triaza-7-phosphatricyclo-[3.3.1.1]decanephosphine; RAPTA-C) was studied using UV–visible (UV–vis) spectrophotometry and NMR spectroscopy. In analogy to in silico studies, [Ru(η6-p-cymene)Cl(H2O)(PTA)]+ was found to be the most abundant hydrolysis product, although the dihydrolysed species [Ru(η6-p-cymene)(OH)(H2O)(PTA)]+ and the dichloro compound are present. Rate constants for the different aquation and anation steps and the equilibrium constants were determined. Hydrolysis is suppressed at high chloride concentrations. These results have important implications on the mode of action of the RAPTA drug candidates.