Studies in the Catalytic Properties of Supported Transition Metal Complexes

Robertson, John (1974) Studies in the Catalytic Properties of Supported Transition Metal Complexes. PhD thesis, University of Glasgow.

Abstract

The object of this research was to investigate possible relationships between homogeneous and heterogeneous catalysis at the interface by examining complexes of potential homogeneous catalytic activity, supported on an "inert" carrier, and by studying the catalytic activity of these complexes in the heterogeneous phase. Attempts have been made to support a number of transition metal complexes on silica. From the observation of colour changes and changes in the infra-red spectra of the supported systems, it has been shown that some complexes, viz. ethylene palladous chloride, potassium ethylene trichloroplatinate and triiron dodecacarbonyl, decompose to the metal when supported by impregnation on the carrier from solution. Titanocene dichloride and rhodium trichloride retain their structures when so supported, while tristriphenylphosphine rhodium(I)chloride, when supported on silica, undergoes a structural rearrangement which is believed to involve the formation of a metal-hybride bond. Supported triruthenium dodecacarbonyl and triosmium dodecacarbonyl, although retaining their structures at ambient temperature and in an inert atmosphere, undergo chemical change on exposure to light, heat or air. By studying the CO labelled dodecacarbonyls, it has been shown that this chemical change involves the loss of carbon monoxide. It is. postulated that such structural changes are due to the influence of hydroxyl groups on the surface of the support material. The catalytic properties of titanocene dichloride, tristriphenylphosphine rhodium(I)chloride, rhodium trichloride, triruthenium dodecacarbonyl and triosmium dodecacarbonyl supported on silica have been investigated by studying their activities for the hydrogenation and iso-merisation of but-1-ene in a pulse-flow reactor system. Titanocene dichloride and tristriphenylphosphine rhodium(I)chloride when supported on silica possess negligible catalytic activity for these reactions. Silica supported rhodium trichloride is active in the isomerisation of but-1-ene to cis and trans but-2-ene in the absence of molecular hydrogen. It has not been possible to determine whether this reaction proceeds via a 1-methyl-pi-allyl or a 2-butyl intermediate. Catalysts active in the hydrogenation and isomerisation of but-1-ene have been prepared by heating silica-supported triruthenium and triosmium dodecacarbonyl in helium and in vacuo, whereby the complexes undergo an irreversible transition with the loss of some carbon monoxide. It is believed that this activation involves the reaction of the complex with surface hydroxyl groups of the support, thereby forming a new cluster complex which possesses sites capable of coordinating olefin molecules in a reactive form. From investigations of the kinetics and energetics of the reactions of but-1-ene with hydrogen and deuterium over the supported ruthenium complex in a static system, and from the product distributions of these reactions, as determined by gas chromatography and mass spectrometry, it is concluded that the isomerisation reaction proceeds via a 1-methyl-pi-allyl intermediate. It is also concluded that the hydrogenation and exchange reactions occur by a Rideal-Eley mechanism. Finally, evidence is presented to suggest that two-distinct sites are present on this catalyst, probably the result of asymmetry induced in the molecule by its interaction with the surface.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Inorganic chemistry
• Date of Award: 1974
• Depositing User: Enlighten Team
• Unique ID: glathesis:1974-78659
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 30 Jan 2020 15:05
• Last Modified: 30 Jan 2020 15:05
• URI: https://theses.gla.ac.uk/id/eprint/78659