Crystal structures of three salts of the tri-phenylsulfonium ion

The reactions of tri-phenyl-sulfonium chloride ([TPS][Cl]) with various acids in methanol yield the corresponding salts tri-phenyl-sulfonium triiodide, C₁₈H₁₅S⁺·I₃ ^- or [TPS][I₃] (I), tri-phenyl-sulfonium perchlorate, C₁₈H₁₅S⁺·ClO₄ ^- or [TPS][ClO₄] (II), and tri-phenyl-sulfonium hexa-fluoro-phosphate, C₁₈H₁₅S⁺·PF₆ ^- or [TPS][PF₆] (III), as crystalline products. These crystals were structurally characterized by single-crystal X-ray diffraction. In all three compounds, the sulfur atom in the tri-phenyl-sulfonium cation adopts a distorted trigonal-pyramidal geometry. [TPS][I₃] (I) and [TPS][PF₆] (III) both crystallize in the space group P2₁/n, while [TPS][ClO₄] (II) crystallizes in P2₁. The S-C bond lengths are comparable across the three salts, and the S-C-S bond angles are consistently between 102 and 106°. Hirshfeld surface analyses reveal that each structure is dominated by hydrogen-based inter-molecular contacts, supplemented by anion-specific inter-actions such as I⋯H in (I), O⋯H in (II), and F⋯H in (III). These contacts organize the ions into mono-periodic ribbon- or chain-like arrangements. No significant π-π stacking is observed.