Arsenic tribromide

Overview
Arsenic tribromide is the chemical compound with the formula AsBr3. This pyramidal molecule is the only known binary arsenic bromide. It forms by the direct reaction of bromine and arsenic. AsBr3 is noteworthy for its very high refractive index of approximately 2.3. It also has a very high diamagnetic susceptibility.

Bromides of arsenic
AsBr5 is not known, although the corresponding phosphorus compound PBr5 is known. AsBr3 is the parent for a series of hypervalent anionic bromoarsenates including [As2Br8]2−, [As2Br9]3−, and [As3Br12]3−.

Organoarsenic bromides, (CH3)2AsBr and (CH3)AsBr2 are formed efficiently by the copper-catalyzed reaction of methyl bromide with hot arsenic metal. This synthesis is similar to the direct process used for the synthesis of methyl chlorosilanes.