A new anion, [Hg2(SCN)7]3−: First synthesis, spectroscopic characterization and X-ray structure determination of [Co(NH3)6][Hg2(SCN)7]

The reaction of [Co(NH3)6]Cl3 with a mixture of HgCl2 and NH4SCN in 1:2:8 molar ratio in hot aqueous medium leads to formation of a new complex salt, [Co(NH3)6][Hg2(SCN)7] (1) in 70% yield. This hexaamminecobalt(III) complex salt has been characterized by elemental analyses, solubility measurement and spectroscopic techniques (e.g. UV/Visible, IR and 13C NMR). Single crystal X-ray structure determination of 1 revealed the presence of discrete [Co(NH3)6]3+ cation and a new anion, [Hg2(SCN)7]3−. This is the first report of a complex salt containing the new anion. The crystal lattice of the complex salt is stabilized by electrostatic forces of attraction and N–H…N (thiocyanate) hydrogen bonding interactions.