Structure and properties of a rhodium(III) pentanitrato complex embracing uni- and bidentate nitrato ligands

A novel rhodium [Rh(NO₃)₅]²⁻ anionic complex with mixed denticity of nitrato ligands was isolated in a form of its poorly soluble caesium salt. The structure of the salt was studied by an X-ray single crystal method. DFT-based theoretical studies were carried out to gain insights into the electronic structure and the properties of the [Rh(NO₃)₅]²⁻ complex. The calculated ¹⁵N NMR chemical shifts of nitrato groups in [Rh(NO₃)₅]²⁻ complex was found to become sensitive to the nitrate ligand coordination bonding mode upon ion-pairing with caesium cations. In good agreement with experimental findings, the DFT calculated free energies for the addition of H₂O or NO₃ ⁻ ligands to the [Rh(NO₃)₅]²⁻ complex points to its low hydrolytic stability.