Radiolysis of aqueous solutions of ruthenium(III) hexa-ammine chloropenta-ammine

Abstract

Ru(NH₃)₆ ³⁺ is reduced by e^– _aq and by the radical CH₂OH to Ru(NH₃)₆ ²⁺. Similar reduction of Ru(NH₃)₅Cl²⁺ first gives Ru(NH₃)₅Cl⁺ which aquates to Ru(NH₃)₅H₂O²⁺ with a rate constant 4·7 sec.^–1. The aquo-ion reduces the original Ru(NH₃)₅Cl²⁺ to give Ru(NH₃)₅Cl₊ and Ru(NH₃)₅H₂O³⁺ with a rate constant 1·0 × 10³ l.mole^–1 sec.^–1, so that the aquation of Ru(NH₃)₅Cl²⁺ is catalysed by small amounts of the reduced species. Oxidation of Ru(NH₃)₆ ³⁺ by OH appears to give Ru(NH₃)₆ ⁴⁺ as the primary product, which decays by a bimolecular process (k= 4·5 × 10⁹ l. mole^–1 sec.^–1) to give species tentatively designated as Ru(NH₃)₆ ⁵⁺ and Ru(NH₃)₆ ^3–. The former has a half-life of 0·75 sec. and leads to products which decay slowly during hours. Oxidation of Ru(NH₃)₅Cl²⁺ differs in that there are three compounds formed successively in first-order processes after the primary oxidation step, with rate constants 2·5 × 10⁵, 44, and 0·45 sec.^–1. It is suggested that these are aquation products formed from Ru(NH₃)₅Cl³⁺. Absorption spectra of the intermediates have been obtained.