Binding of inorganic oxo-anions to cationic cobaltammine: Synthesis, characterization, X-ray structures determination and DFT calculations of [Co(NH3)6]Cl2(ClO3), [Co(NH3)6]Br2(ClO3) and [Co(NH3)6]Cl2(IO3) · H2O

Single crystals of [Co(NH3)6]Cl2(ClO3) (1), [Co(NH3)6]Br2(ClO3) (2) and [Co(NH3)6]Cl2 (IO3) · H2O (3) suitable for X-ray structure determinations were obtained directly by reacting hexaamminecobalt(III) halide with appropriate metal halates in 1:1 molar ratio in hot aqueous medium. These hexaamminecobalt(III) complexes have been characterized by spectroscopic studies (e.g. UV/Visible and IR). Single crystal X-ray structure determination of title complex salts revealed the presence of discrete ions, i.e., cation [Co(NH3)6]3+ and mixed anions Cl− and ClO3- or Br− and ClO3- or Cl− and IO3- in the solid state. Crystal lattice is stabilized by electrostatic forces of attraction and hydrogen bonding interactions (N–H⋯O−, N–H⋯Cl− or N–H⋯Br−). The formation of definite salts of composition with halate ions suggests that [Co(NH3)6]3+ may be used as purely inorganic anion binding agent for these weakly coordinating oxo-anions. The DFT calculations have been carried out to calculate molecular volumes of the oxoanions and separation between two successive cation layers.

The binding of halate ions with hexaamminecobalt(III) present in hexaamminecobalt(III) chloride has been studied crystallographically for the first time. This revealed that the cation cobaltammine is a strong binding agent for halate ions. DFT calculations have also been carried out to calculate molecular volumes and distances between two successive cation layersFigure optionsDownload as PowerPoint slide