The use of neat BrCl in organic and inorganic chemistry is limited due to its gaseous aggregate state and especially its decomposition into Cl₂ and Br₂. The stabilization of BrCl in form of reactive ionic liquids via a novel in situ synthesis route shifts this equilibrium drastically to the BrCl side, which leads to safer and easier to handle interhalogenation reagents. Furthermore, the crystalline derivatives of the hitherto unknown [Cl(BrCl)₂] – and [Cl(BrCl)₄] – anions were synthesized and characterized by single‐crystal X‐ray diffraction (XRD), Raman and IR spectroscopy, as well as quantum chemical calculations.