A rational synthesis of new anion [HgBr4Cl]3−: Synthesis, characterization and single crystal X-ray structure determination of [Co(NH3)6][HgBr4Cl]

A new anionic species [HgBr4Cl]3− has been isolated in the form of complex salt, [Co(NH3)6][HgBr4Cl] (1). The complex salt was crystallized from a solution of hexamminecobalt(III) chloride and potassium tetrabromidomercurate(II) in aqueous medium in 1:1 molar ratio. This complex salt has been characterized by elemental analyses, spectroscopic techniques (e.g. UV/Visible, IR), solubility product and conductance measurements. The complex salt crystallizes in monoclinic crystal system with space group P21/c. Single crystal X-ray structure determination revealed the presence of discrete ions: [Co(NH3)6]3+ cation and a new anion [HgBr4Cl]3−. This is the first structural report of any complex salt containing mixed halogenidomercurate(II) ion, [HgBr4Cl]3−. The crystal lattice is stabilized by the extensive hydrogen bonding (N―H…Br/Cl) between the cationic and anionic moieties resulting in a bi-layered structure.