Antimony Pentabromide, SbBr₅

Antimony Pentabromide, SbBr₅, has not yet been isolated; its existence, however, is indicated by the action of antimony trihydride upon an aqueous solution of a mixture of bromine and potassium bromide, while molecular weight determinations on solutions in bromine by the boiling point method also suggest the existence of this compound. Complex compounds with organic bases have been prepared, in addition to many complex inorganic salts; these may perhaps be regarded as salts of bromoantimonic acids.

Of the three possible acids only one has been obtained in the free state. By crystallisation from a solution containing antimony tri-bromide, bromine and either hydrobromic or sulphuric acid the compound meta-bromoantimonic acid, HSbBr₆.3H₂O, has been prepared in the form of hygroscopic, irregular, six-sided, black tablets. It decomposes readily, with evolution of bromine, leaving a residue of antimony tribromide. The following salts, corresponding to this acid, have also been prepared:

LiSbBr6.4H2O	Black, square, hygroscopic tablets.
KSbBr6.H2O	Stout, six-sided, black tablets.
NH4SbBr6.H2O	Resembles the potassium salt.
Fe(SbBr6)3.14H2O	Black, irregular, six-sided tablets; very hygroscopic.
Ni(SbBr6)2.12H2O	Black, glistening, irregular, six-sided tablets.

Other complex salts that have been described include:

2SbBr5.3CsBr.2H2O	Black, microcrystalline powder.
3SbBr5.2BeBr2.18H2O	Black, glistening prisms.
5SbBr5.2AlBr3.24H2O	Black, glistening, stout prisms.

Some of the organic compounds suggest relationship with pyrobromoantimonic acid.