Cesium Fluoride–Bromine Intercalation Compounds

CsF reacts with Br2 to form the two intercalation compounds CsF·Br2 and 2CsF·Br2. The former consists of layers of CsF squares separated by layers of Br2 molecules oriented perpendicular to the CsF layers. 2CsF·Br2 is a second‐stage compound, composed of two layers of CsF followed by one layer of bromine molecules. Iodine cannot replace bromine; instead, it reacts with CsF to form Cs2I8, and probably CsIF6 between 0° and 120 °C. Chlorine does not react at all with CsF. Bromine reacts with RbF only superficially, and after a long time some RbBr3 is observed; RbF and I2 give RbI3.