Hygrometers, catalystsCobalt(II) bromide hydrate is mainly used as a catalyst in organic synthesis, like C-metal, C-heteroatom and C-C bond formations, addition to unsaturated bonds, cyclizations, polymerization, oxidations reductions and carbonylations. It reacts with ammonia to form coordination compound bromopentaamminecobalt(III) bromide. It reacts with triphenylphosphine and form complexes of cobalt(II) bromide, which used as a catalyst in organic synthesis.