The structure of triphenylphosphorus–dibromine, the first crystallographically characterised bromophosphorane, a compound which has the novel four-coordinate molecular Ph 3 P–Br–Br geometry

Triphenylphosphorus–dibromine is shown by X-ray crystallography to have a four-coordinate Ph3P–Br–Br ‘spoke’ structure and is isostructural with Ph3P–I–I and Ph3As–I–I; thus forcing us to question the conventional belief that tertiary-organo group 15 adducts with dihalogens have either pentacoordinate R3EX2 or ionic [R3EX]+X– structures in the solid state.