RuH2O63

RuH2O63 is a shorthand notation for the hexaaquaruthenium(III) cation, [Ru(H2O)6]3+. In aqueous solution this species represents ruthenium in the +3 oxidation state coordinated by six water molecules. The conventional way to denote it in chemical formulas is [Ru(H2O)6]3+; the simplified form underscores its aquated nature.

Structure and properties: The six water ligands arrange around ruthenium in an octahedral geometry. The complex is paramagnetic with one unpaired electron (low-spin d5 configuration). In solution, it is typically colored due to d–d transitions, often described as violet or related hues, depending on concentration and the presence of other species. The aqua ligands can be displaced by stronger or multidentate ligands in substitution reactions, reflecting the lability of the complex.

Formation and reactions: Hexaaquaruthenium(III) forms when Ru(III) salts such as RuCl3 are dissolved in water and, if needed, kept in acidic solution to suppress hydrolysis. With increasing pH, the complex undergoes hydrolysis to yield hydroxy-bridged species like [Ru(H2O)5(OH)]2+ and higher-order rubidium or ruthenium oxide-hydroxide equilibria, depending on conditions. The Ru(III) aqua complex serves as a versatile precursor for synthesizing a wide range of ruthenium(III) coordination compounds by ligand substitution.

Applications and context: As a common ruthenium(III) aqua starting material, [Ru(H2O)6]3+ is used in inorganic synthesis, catalysis research, and electrochemical studies. It provides a straightforward entry point to many coordination chemistries of ruthenium and helps illustrate properties of high-valent aqua complexes in aqueous media.

See also: Hexaaquoruthenium(III) complex; Ruthenium aqua chemistry.