Coordination compound containing σ-hole interactions: Synthesis and crystal structure of NH4[Cr(CO(NH2)2)6][Hg(SCN)4]2·2H2O

The crystallographic analysis of complex, NH4[Cr(CO(NH2)2)6][Hg(SCN)4]2⋅2H2O (1) has revealed that its cations and anions are held together by secondary non-covalent interactions. These interactions have led to the formation of four σ-holes, one on Hg and three on S atoms. The molecular electrostatic potential (MEP) study confirms that the σ- holes on sulphur are large enough to generate interactions between S...S (chalcogens) and S...N (chalcogen-pincogen) in [Hg(SCN)4]2−. Single crystal X-ray diffraction of 1 has revealed that [Cr(CO(NH2)2)6]3+ are stacked one upon another running parallel along a-axis and surrounded by a “cylinder” consisting of anions, ammonium cations and water molecules. The supramolecular architecture has been obtained which is being stabilized by intermolecular hydrogen bonding interactions (O-H⋅⋅⋅N, O-H⋅⋅⋅S, N-H⋅⋅⋅N, N-H⋅⋅⋅O (H2O)) along with the formations of σ-hole interactions. The crystals of 1 has been obtained using one-pot synthetic method by reacting [Cr(CO(NH2)2)6]Cl3⋅3H2O, HgCl2 and NH4SCN (in 1:2:8 molar ratio) in aqueous medium and have been initially characterized by UV-visible and IR spectroscopy.