The X-ray structure analysis of phosphorus thioiodide (1958)
AuthorsWright, D. A.show all
These compounds were studied by Ouvrand (1892), (1894), who came to the conclusion that three thioiodides existed, namely P₄S₃I₂, PSI and P₂SI₄. Three methods of preparation for P₄s₃I₂, one for PSI and four for P₂sI₄ were given, but Ouvrard mentions neither the precise conditions for their preparation, nor any means of characterization. The compound P₄S₃I₂ was also reported by Wolter (1907) as formed by the slow addition of iodine to P₄S₃, a method given by Ouvrard. The lack of any analogues to these compounds such as P₄O₃I₂, P₄ S₃Br₂ made it of considerable interest to confirm these early reports if possible, and find the inter-relationships between any thioiodides made. Accordingly an investigation was carried out in detail by Topsom and Wilkins (1956). Attempts to prepare P₂SI₄ and PSI by Ouvrard's methods were not successful. They could not be detected even as intermediates under the mildest conditions of reaction, and their existence is open to serious doubt. Two of the methods did in fact lead to a thioiodide, but this was shown to be P₄S₃I₂. Two of the three methods given by Ouvrard for the preparation of P₄S₃I₂ were successful, that one consisting of heating the elements in the ratio of 4P:3S:2I giving almost quantitative yield (see Section 2.1). The compound was easy to prepare and readily characterized. Topsom and Wilkins could not detect any other phosphorus thioiodide and infer that this is the only stable compound formed by these three elements.