The water-soluble cluster cation [H₃Ru₃(C₆H₆)(C₆Me₆)₂(O)]⁺: Improved synthesis, aerobic oxidation, electrochemical properties and ligand exchange studies

The synthesis of the trinuclear cluster cation [H₃Ru₃(C₆H₆)(C₆Me₆)₂(O)]⁺ (<b>1</b>) has been considerably improved by changes in the NaBH₄ addition step and by introducing chromatographic methods; in addition, the redox and ligand exchange properties of <b>1</b> have been studied. Although exposure of an aqueous solution of <b>1</b> to air yields the oxidised cluster [H₃Ru₃(C₆H₆)(C₆Me₆)₂(O) (OH)]⁺ (<b>2</b>), cyclic voltammetry of [<b>1</b>][BF₄] in acetonitrile reveals a first reversible oxidation step that does not involve <b>2</b>. Bulk electrolysis of <b>1</b> and <b>2</b> in the same medium affords only decomposition products. Ligand exchange in <b>1</b> takes place only at higher temperatures: by heating a mixture of toluene with an aqueous solution of [<b>1</b>][BF₄] (1000:1) to 110 °C for 2 h, the formation of the toluene derivative [H₃Ru₃(C₆H₅Me)(C₆Me₆)₂ (O)]⁺ (<b>3</b>) is observed in small quantities. H/D exchange of <b>1</b> with D₂O does not occur up to 90 °C; however, in the presence of D₂, H/D exchange with <b>1</b> is observed to give the deuterated derivative [D₃Ru₃ (C₆H₆)(C₆Me₆)₂ (O)]⁺ (<b>1a</b>). The results provide an improved synthesis of <b>1</b>, as well as information about its redox and ligand-exchange reactions, results necessary to understand and develop the chemistry of <b>1</b>.