Synthesis, characterization and reactivity of Claus' blue, a superoxodirhodium(III,III) species long said to contain RhVI

Abstract

Spectroscopic study of the ill defined Claus' blue, ‘[Rh^VIO₄]^2–’, and the better characterized [Rh^III₂(OH)₂(H₂O)_n(µ-O₂)]³⁺ ion has revealed that the two ostensibly very different syntheses involved both give aquasuperoxorhodium(III) species; the properties of the two products are compared and contrasted. The O–O link in Claus' blue derives from the oxidation of co-ordinated hydroxide to give a peroxo-, then a superoxo-form. The properties of Claus' blue are rationalized in terms of its synthesis. The [Rh^III(O₂)Rh^III]⁵⁺ core can be utilized to form other rhodium(III) superoxide complexes.