Preparation and characterisation of the platinum group metal fluorides.
thesisposted on 19.11.2015, 08:47 by Gillian. Stanger
An extensive reveiw of the platinum group metal fluorides has been carried out and in the light of this, new preparative routes have been developed and characterisation has been significantly improved. The preparation of the platinum group metal fluorides in both static and dynamic systems is discussed in chapter two. The fluorinations of ruthenium, rhodium and platinum sponges in dynamic systems proved to be of greatest interest. In these studies large amounts of ruthenium hexafluoride and platinum hexafluoride were produced and traces of rhodium hexafluoride were noted, where as previously more forcing conditions had been employed in the preparation of these compounds. It is believed that rigorous drying of the flow line and hydrogenation of the metal in situ are responsible for the success of this new preparative route. When ruthenium is fluorinated in the dynamic system ruthenium hexafluoride and tetrameric ruthenium pentafluoride are produced in large quantities, and smaller amounts of a red glassy material is also formed. There have been no previous reports of any red material forming during this reaction. It is now believed that this material is a trimeric form of ruthenium pentafluoride. The charaterisation of these fluorides was carried out using a large variety of techniques, the most useful being mass spectrometry and matrix isolated infrared spectroscopy. Mass spectrometry proved invaluble in the characterisation of the trimeric ruthenium pentafluoride, while matrix isolation enabled good quality infrared spectra of the reactive hexafluorides to be recorded. These techniques were also utilised to give the first insight into the behaviour of the tetrameric pentafluorides in the gas phase. Iridium pentafluoride has been shown to be monomeric at elevated temperatures, under similar conditions ruthenium and osmium pentafluorides decompose to the metal and fluorine. Platinum pentafluoride is known to be unstable at room temperature and thought to decompose to the hexafluoride and tetrafluoride. Using matrix isolation, direct evidence of this has been obtained.