Nitrosylruthenium nitrato complexes in aqueous nitric acid

Paper chromatographic and ion exchange studies of nitrosylruthenium nitrato complexes in 0·1–14·5 M nitric acid have enabled the complexes to be separated into four groups in order of increasing complexing from the mononitrato to the pentanitrato complex, H2RuNO(NO3)5. The eleven nitrato complexes which can be formulated assuming a regular octahedral arrangement around the hexa-co-ordinated ruthenium have been allocated to these groups. Absorption spectra and compositions are presented for equilibrium mixtures of the complexes in nitric acid and the successive formation constants for nitrato complexing of nitrosylruthenium have been calculated. Other measurements include the rates of one of the denitration reactions at 0° and 25° and the ruthenium distribution coefficients after prolonged contact of solutions in 0·5–10 M nitric acid with an anion exchange resin. In contrast to other metal nitrates, tributyl phosphate extracts preferentially the tetra- and pentanitrato acids rather than uncharged trinitrato complex.