E.S. Yandanova, D.M. Ivanov, M.L. Kuznetsov, A.G. Starikov, G.L. Starova, V.Yu. Kukushkin
“Recognition of S···Cl Chalcogen Bonding in Metal-Bound Alkylthiocyanates”
Cryst. Growth Des., 2016, 16, 2979-2987
Reaction of K2[PtCl4] with excess AlkSCN in water gives the alkylthiocyanate complexes trans-[PtCl2(AlkSCN)2] (Alk = Et 1, nPr 2; 80–85%). These species were studied, in particular, by X-ray crystallography. In the solid state, both 1 and 2 exhibit the previously unreported S···Cl chalcogen bonding, which consolidates the complexes into networks and leads to layered structures. Theoretical density functional theory calculations and Bader’s atoms in molecules analysis demonstrated two types of intermolecular interactions in tetramer (1)4, viz. the S···Cl chalcogen and the H···Cl hydrogen bonds. Despite that each particular S···Cl or H···Cl bonding is weak with the estimated energy of 1–2 kcal/mol, altogether they play a crucial role in the stabilization of the S2Cl2 fragment in (1)4, the basis set of superposition error corrected interaction energy being −12.8 kcal/mol per monomer complex molecule. The chalcogen bonding and the rhomboidal structure of the S2Cl2 fragment can be interpreted in terms of electrostatic arguments as a result of the interaction between the belt of negative electrostatic potential around the Cl atoms and the sulfur σ-holes. The natural bond orbital analysis revealed that both LP(S) → LP*(Pt)/σ*(Pt–N)/σ*(Pt–Cl) and LP(Cl) → σ*(S–C) types of hyperconjugative charge transfers are important in the chalcogen bonding.