Abstract: Three complexes [2-ClPyH]₂CoCl₄(1), [2-ClPyH]₂NiCl₄(2) and [2-ClPyH]₂CuCl₄(3) were prepared, and their crystal structures were determined with X-ray crystallography. In each of the structures, the [2-ClPyH]⁺ cation is almost in the same plane while the [MCl₄]^2- anion is a slightly distorted tetrahedron. The X-ray crystallography analysis indicates that ultimate structures include the hydrogen bonds N—H…Cl and C—H…Cl, intermolecular Cl…Cl interactions as well as π-π stacking interactions. The title compounds were investigated theoretically via crystal orbital method based on density functional theory, as self-existent anions and a structure units respectively. The hydrogen bonding determines the directions of one-dimensional infinite columns and Cl…Cl interactions plays a crucial role in the final structure.

Key words: Adduct, Hydrogen bonds, Cl…Cl interaction, π-π Stacking interaction