KINETIC STUDIES ON THE NUCLEOPHILIC ACTIVATION OF CARBON MONOXIDE IN RU(NH3)5CO(PF6)2

Abstract

CO activation in the [Ru(NH3)5CO]2+ ion has been demonstrated under nucleophilic conditions in pyridine or 2-ethoxyethanol solution at 100 °C. In the presence of Me3NO the observed pseudo-first order rate constants were found to be sensitive only to auxiliary ligand concentration (pyridine or methyl pyridines), but with a tendency towards rate saturation and the same limiting rate at large excess of each entering ligand. A mechanism is proposed in which the rate-limiting step is viewed as an auxiliary ligand-assisted CO2 elimination, preceded by a fast reversible addition of Me3NO. This reaction pathway is also supported by the values determined for ΔH ‡ (81 ± 13 kJ mol−1) and ΔS ‡ (−114 ± 36 J mol−1 K−1).