Crystal structures of three salts of the triphenylsulfonium 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] (<b>I</b>), tri-phenyl-sulfonium perchlorate, C₁₈H₁₅S⁺·ClO₄ ^- or [TPS][ClO₄] (<b>II</b>), and tri-phenyl-sulfonium hexa-fluoro-phosphate, C₁₈H₁₅S⁺·PF₆ ^- or [TPS][PF₆] (<b>III</b>), 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] (<b>I</b>) and [TPS][PF₆] <b>(III</b>) both crystallize in the space group <i>P</i>2₁/<i>n</i>, while [TPS][ClO₄] (<b>II</b>) crystallizes in <i>P</i>2₁. 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 (<b>I</b>), O⋯H in (<b>II</b>), and F⋯H in (<b>III</b>). These contacts organize the ions into mono-periodic ribbon- or chain-like arrangements. No significant π-π stacking is observed.