Robust motifs in 2-phenylethylammonium and related tetrahalometallates

The novel crystal structures of seven compounds which combine 2-phenylethylammonium cations and perhalometallate anions, all with the general formula (C₈H₉NH₃⁺)₂ MX₄^2-, were determined to establish the effect of metal atom and halogen ligand substitution on the structures and hydrogen bonding interactions. Five of the structures, bis(2-phenylethylammonium) tetrachlorozincate, (C₈H₉NH₃⁺) ₂ ZnCl₄^2-, bis(2-phenylethylammonium) tetraiodozincate, (C₈H₉NH₃⁺) ₂ ZnI₄^2-, bis(2-phenylethylammonium) tetrabromodichloroiodozincate, (C₈H₉NH₃ ⁺)₂ ZnCl₂BrI^2-, bis(2- phenylethylammonium) tetrabromocadmate, (C₈H₉NH ₃⁺)₂ CdBr₄^2-, and bis(2-phenylethylammonium) tetrabromomercurate, (C₈H ₉NH₃⁺)₂ HgBr₄ ^2-, were found to be isostructural, while two of the compounds containing iodo ligands, bis(2-phenylethylammonium) tetraiodocadmate, (C ₈H₉NH₃⁺)₂ CdI ₄^2-, and bis(2-phenylethylammonium) tetraiodomercurate, (C₈H₉NH₃⁺)₂ HgI ₄^2-, crystallize in a different, but related disordered structure. Strong N⁺-H⋯X^--M hydrogen bonding interactions, as well as weaker C-H⋯π aromatic interactions occur in all seven structures, and two robust tetrameric hydrogen bonded zero-dimensional motifs are present in all seven structures. C-H⋯Cl-M hydrogen bonding interactions are present in the structure of bis(2-phenylethylammonium) tetrachlorozincate, and result in the distortion of the geometry of the 2-phenylethylammonium cation. Comparison of the identified zero-dimensional hydrogen bonding motifs with those occurring in related structures reported in the literature shows that the motifs are robust and can tolerate changes in cation, metal and ligand to a large extent.