Ionic-liquid-assisted synthesis of the phosphorus interhalides [PBr4][IBr2] and [PBr4][I5Br7].

The phosphorus interhalides [PBr₄][IBr₂] (1) and [PBr₄]₂[I₅Br₇] (2) were prepared by reaction of PBr₅ and the interhalogen IBr in the ionic liquid [MeBu₃N][N(Tf)₂] (N(Tf)₂: bis(trifluoromethylsulfonyl)amide). [PBr₄][IBr₂] (1) consists of tetrahedral [PBr₄]⁺ cations and linear [IBr₂]⁻ anions. [PBr₄]₂[I₅Br₇] (2) also contains [PBr₄]⁺ cations as well as the iodine bromide anion [I₅Br₇]²⁻. The latter represents the yet largest known polyiodinebromide. Moreover, (2) shows remarkable halogen release (IBr and Br₂) of 96.8 wt% below 300 °C. For the ternary system P–Br–I, (1) and (2) are the first compounds that were characterized by crystal structure analysis. Composition, bonding situation and properties were further validated by energy dispersive X-ray (EDX) analysis, thermogravimetry (TG) and Raman spectroscopy. [ABSTRACT FROM AUTHOR]