Halides of Phosphorus, Arsenic, Antimony, and Bismuth

Abstract

This chapter focuses on simple halides of phosphorus, arsenic, antimony, and bismuth; compounds that also contain other elements. These compounds fall into two large groups according to whether the central atom has an oxidation state of +5 or +3. Both simple and complex halides are known in each of these groups. There are also halides of minor importance in which the elements have oxidation states below +3. Simple halides with oxidation state +3 may be prepared directly from the elements, although this route is not always the most suitable. The reactivity of fluorine is such that the pentafluoride is formed as a secondary product with phosphorus and arsenic and also to a smaller extent with antimony. Bismuth becomes coated during fluorination with a solid layer of fluoride, which hinders further reaction. Little is known so far about halides with oxidation states < +3, and it is not clear if the various substances reported in the literature are true compounds. Isomerism and bonding have been discussed in the chapter. It is quite understandable that the molecular form of a substance showing bonding isomerism should react differently from the ionic form. It follows that the nature of the solvent will influence the mode of reaction of such substances very strongly. In cases where equilibrium is involved, both temperature and concentration will also have a considerable influence for a given solvent.