The Formation of High-Order Polybromides in a Room-Temperature Ionic Liquid: From Monoanions ([Br5]- to [Br11]-) to the Isolation of [PC16H36]2[Br24] as Determined by van der Waals Bonding Radii

An unprecedented diversity of high-order bromine catenates (anionic polybromides) was generated in a tetraalkylphosphonium-based room temperature ionic liquid system. Raman spectroscopy was used to identify polybromide monoanions ranging from [Br-5](-) to [Br-11](-) in the bulk solution, while single-crystal X-ray diffraction identified ex-tended networks of linked [Br-11](-) units, forming a previously unknown polymeric [Br-24](2-) dianion. This represents the largest polybromide species identified to date. In combination with recent work, this suggests that other, higher order molecular polybromide ions might be isolated.