Novel complexes possessing Hg–(Cl, Br, I)⋯OC halogen bonding and unusual Hg2S2(Br/I)4 kernel. The usefulness of τ4′ structural parameter

One mononuclear and two binuclear HgII complexes have been synthesized and characterized by X-ray diffraction, ATR IR and Hirshfeld surface analysis. Single-crystal X-ray diffraction showed that binuclear compounds are centrosymmetric and isostructural. All complexes form bifurcated intermolecular N–H⋯O hydrogen bonds that contribute to a formation of the centrosymmetric dimers. In binuclear complexes, sulfur atoms of thiourea ligands take the bridging role. These are the first examples of such compounds with mercury. In binuclear complexes of group 12 elements, halogens are usually the bridging atoms. The geometries of binuclear complexes are highly distorted with alarmingly low value of τ 4 ′ parameter suggesting presence of additional donor that turned out to be phenyl ring (Hg⋯π interaction). The crystal structures are stabilized by additional noncovalent interactions, including halogen bonding which leads to the formation of chains. The differences and similarities of these complexes indicate that halogen ions have a great impact on the structures. Presented complexes comprise unique interactions between mercury-bonded halogen atoms and neighboring oxygen atoms of carbonyl groups (Hg–(Cl, Br, I)⋯O C contacts).