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UBC Theses and Dissertations

The fluorides of platinum and related compounds Lohmann, Derek Harry

Abstract

The fluorides of platinum have been reinvestigated. Attempts to prepare a difluoride were unsuccessful. It is suggested that this is-due to it being unstable towards disproportionation. X-ray Crystallographic evidence is presented as evidence for a trifluoride of platinum although a pure sample has not been isolated. This trifluoride is shown to be isostructural with the rhombohedital trifluorides of palladium, iridium and rhodium. Platinum tetrafluoride has been reinvestigated. It was found to be diamagnetic and to have a lattice of slightly-distorted, tetragonal uranium tetrachloride type. The adducts of platinum tetrafluoride with bromine trifluoride and selenium tetrafluoride were investigated further and found to be diamagnetic. The platinum tetrafluoride, selenium tetrafluoride adduct was shown to be isostructural with the corresponding palladium and germanium compounds. An ionic lattice is suggested for these compounds. Bromine trifluoride adducts do not form a similar-series and this, combined with their physical properties lead to the suggestion that these compounds are more covalent in nature. The previously unknown pentapositive state of platinum has been established. Platinum pentafluoride is a deep-red, reactive solid which readily disproportionates on heating. It gives rise to 1:1 adducts with iodine pentafluoride and chlorine trifluoride. These, like the bromine trifluoride adducts, are low-melting solids. Potassium fluoroplatinate (V) was prepared as a deep-yellow solid, crystallizing with the rhombohedral potassium fluorosmate lattice. A pentapositive oxyfluoride, platinum oxytrifluoride was found, it is suggested that this is polymeric. Platinum hexafluoride has been briefly investigated. A very reactive oxyfluoride, of formula PtO₂F₆, has been prepared and investigated. It is a deep-red solid which can be sublimed at 90° in a vacuum. It melts with decomposition at 219°. It is paramagnetic and crystallizes in a cubic lattice. Many of its chemical properties were studied. It is suggested that this compound is platinum peroxidehexafluoride. The crystal structures of the tetrafluorides of platinum rhodium, tin and lead were investigated. No similarity in structure was found. A brief investigation into the fluorides of rhodium has lead to the suggestion that a pentafluoride, in addition to a tetrafluoride, exists.

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