Lewis‐Acid‐Base Synthesis of [Se₃Cl₃]₂[SnCl₆] and [BMIm]₂[Ga₈As₆Cl₁₆O₁₄]

[Se3Cl3]2[SnCl6] (1) and [BMIm]2[Ga8As6Cl16O14] (2) are prepared by Lewis-acid-base reaction of SnCl2 with SeCl4 and As2O3 with GaCl3/[BMIm]Cl at room temperature and at 60 °C. 1 contains [ClSe−Se−SeCl2]+ cations with an Se3 unit and isolated octahedral [SnCl6]2− anions. The cation was yet only obtainable via Se0/Se4+ synproportionation in liquid SO2 with AsF5. The [Ga8As6Cl16O14]2− anion in 2 consists of two central edge-sharing GaO6 octahedra, surrounded by pseudo-tetrahedral AsO3 units and tetrahedral GaCl3O and GaCl2O2 units. Moreover, an almost planar central Ga4O4 ring surrounded by six GaAs2O3 rings is characteristic, which was not described before. The title compounds are characterized by X-ray diffraction based on single crystals and powders, infrared spectroscopy, thermogravimetry, and optical spectroscopy.