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

During attempted preparation of [Co(NH3)6]Cl[Hg(SCN)4] from an aqueous mixture of [Co(NH3)6]Cl3 and (NH4)2[Hg(SCN)4], an unexpected highly crystalline product of composition [Co(NH3)6][Hg2(SCN)7] has been obtained in an excellent yield.