The structural interrelationship between the three polymorphs of Rh2O3 and Rh2S3, Rh2Se3, and Ir2S3

The syntheses of each of the three modifications of rhodium sesquioxide are reviewed and their infrared spectra are described. Models of each of these structures were constructed and manipulated using interactive molecular graphics. Their interrelationship is clearly described and used both to explain the similar features observed in their respective infrared spectra and to predict the occurrence of other discrete structures in the Rh₂O₃ system. Rhodium sesquisulfide, Rh₂S₃, is shown to be isostructural with the high pressure modification, II-Rh₂O₃.