Pentahalides and Oxyhalides

Sixteen pentahalides could conceivably exist for combinations of P, As, Sb, and Bi with F, Cl, Br, and I. However, several of these possibilities are unknown, and others are of little importance. None of the elements forms a stable pentaiodide, but all of the pentafluorides are known. Phosphorus forms a pentachloride and a pentabromide, whereas antimony forms a pentachloride. As with the discussion of the trihalides, most of the discussion presented will center on the phosphorus compounds. 

Phosphorus pentachloride can be formed by the reaction of excess chlorine with elemental phosphorus or PC13  

Phosphorus pentabromide can be prepared by the reaction of PBr3 with bromine  

In the gas phase, phosphorus pentachloride and pentabromide have the trigonal bipyramid structure (D3h symmetry), 

Several mixed halide compounds are known that have formulas such as PCI3F2, PF3C12, and PF3Br2. These compounds are prepared by adding a halogen to phosphorus trihalides that contain a different halogen, and a typical reaction is 

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