Synthesis of a Hexachloro Sulfate(IV) Dianion Enabled by Polychloride Chemistry

The preparation and structural characterization of [NEt₃ Me]₂ [SCl₆ ] is described, which is the first example of a [SCl₆ ]^2- dianion and of a halosulfate anion of the type [S_x X_y ]^z- in general. This dianion belongs to the group of 14-valence electron AB₆ E systems and forms an octahedral structure in the solid-state. Interestingly, co-crystallization with CH₂ Cl₂ affords [NEt₃ Me]₂ [SCl₆ ]⋅4 CH₂ Cl₂ containing [SCl₆ ]^2- dianions with C_4v symmetry. As suggested by quantum-chemical calculations, the distortion of the structure is not caused by a stereochemically active lone pair but by enhanced hydrogen bonding interactions with CH₂ Cl₂ . At elevated temperatures, [NEt₃ Me]₂ [SCl₆ ] decomposes to various sulfur chlorine compounds as shown by Raman spectroscopy. Cooling back to room temperature results in the selective formation of [NEt₃ Me]₂ [SCl₆ ] which is comparable to the well-studied SCl₄ .