The undecabromide ion

29 April 2013 - Chemical Zoo

In the zoo that is chemical space some strange creatures can be found wandering around. Take for example the undecabromide ion (Br11-) as very recently reported by Haller et al. (DOI) It is a member of a group of polyhalogen ions that already contains obscure species such as linear Br5- and ring-shaped Br102-.
Want some? Get a quantity of bis(triphenylphosphine)iminium chloride (PPNCl), replace the chloride for bromine (mix in water with excess KBr, collect crystals), then add elemental bromine and wait several days for red-brown crystals of (PPN)(Br11·Br2) to form. Judging from X-ray crystallography in this compound 5 bromine molecules are coordinated to a central bromine ion. One arm is extended with an additional bromine unit, linking the anions into chains.