Browsing by Author "Moss, John"

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    Encapsulation of cobalt complexes in zeolite Y for use as hydroformylation catalysts
    (1997) Galatolo, Paul Joseph Victor; Moss, John; Dry, Mark; O'Connor, Cyril
    In industry, the hydroformylation reaction is predominantly homogeneously catalysed using carbonyl complexes of cobalt and rhodium (1-3,45). The main disadvantage of homogeneous catalysts is that, especially for the longer chain hydrocarbon systems, very energy-intensive methods (such as distillation) are required to remove them from the reaction products. These separation techniques usually lead to losses of the catalyst. From an economic viewpoint, this is highly undesirable since the catalysts (especially rhodium) are expensive. Research has been carried out on encapsulating the catalysts within the cages of a zeolite, maintaining the activity of the catalyst while allowing it to be easily removed from the reaction medium ( eg. by filtration). However, all research reported so far has only considered rhodium catalysts (1,66-71,87). Furthermore, in most cases, leaching of the rhodium from the zeolite was significant enough to be undesirable. No successful research has been reported on encapsulating cobalt in zeolites for use as a hydroformylation catalyst. In this study, the synthesis of cobalt complexes encapsulated in the supercages of zeolite Y was attempted. The species initially present on the zeolites were analysed by Fourier-Transform Infrared Spectroscopy (FT-IR) and identified by comparison with the IR spectra of pure cobalt complexes synthesised independently in the laboratory. The impregnated catalysts were washed with various solvents to see if the cobalt complex remained in the zeolite. The impregnated zeolites were also tested as hydroformylation catalysts and compared with homogeneous catalysts.
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    The synthesis and characterization of novel rhodium alkenyl complexes and rhodacycloalkanes
    (2007) Hager, Emma; Moss, John; Smith, Greg
    The rhodium dimers [Cp*RhChh and [Cp*RhBr2h were reacted with alkenyl Grignard reagents MgBr(CH2)nCH=CH2 (n = 1 - 4, 6, 8, 9) in an attempt to form bis-alkenyl complexes that would be potential precursors to rhodium-containing metallacycloalkanes. The shorter-chain Grignard reagents (n = 1 - 3) produced novel rhodium allylic complexes of composition Cp*RhBr(1i3-allyl-R) where R = H, CH3, CH2CH3. These were isolated as stable crystals and were fully characterized by analytical and spectroscopic methods. An X-ray crystal structure obtained for one of the complexes (R = CH2CH3) confirmed the allylic structure of the complex. The use of longer-chain reagents (n = 3, 4, 6, 8, 9) resulted in the fonnation of the novel bis-alkenyl complexes Cp*Rh({CH2}nCH=CH2)2(H2O). The bis-alkenyl complexes were obtained as yellow oils that were found to be stable in air and non-chlorinated solvents, but unstable in chlorinated solvents. They were characterized by NMR, MS and elemental analysis. Ring-closing metathesis (RCM) reactions were carried out on two of the bis-alkenyl complexes (n = 4, 6) in the presence of Grubbs' first-generation catalyst. NMR evidence indicated that the corresponding 11- and 15-membered ring rhodacycloalkenes had been formed. The rhodium phosphine precursors Cp*RhCh(PR3) (PR3 = PPh3, PMePh2, PMe2Ph) were prepared and reacted with the di-Grignard reagents MgBr-(CH2)n-MgBr (n = 7, 8, 9) to form a series of medium-sized rhodacycloalkanes that were larger than any synthesized previously. The rhodacycles were found to be quite unstable at room temperature. Thermal decomposition studies were conducted on some of the complexes and the major organic products were analyzed by GC-MS. In most cases the major products were 1- and 2-alkenes and n-alkanes. It was found that the nature of the tertiary phosphine ligand affected the types of decomposition products formed.
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    The synthesis, characterization and activation of some multinuclear catalyst precursors for olefin polymerization
    (2003) Waggie, Fazlin; Moss, John; Mapolie, Selwyn
    This thesis reports on an exploratory investigation into the immobilization of homogeneous olefin polymerisation cataiysts on dendritic supports...; The dendrimers . employed were essentially allylaryl-ether type systems and consisted of both dendritic wedges .and compltte dendrimers.. These materials were used as supports for homogeneous irconocene catalysts. The zirconium moiety was attached to the surface of the dendrimer through the ally! functionality. This was dope via hydrozirconation of the pendant C=C of the ally! groups on the periphery of the dendrimers. A number of model compounds such as Cp2Zr{(CH2)4iPh}(Cl) and Cp2Zr{(CH2)30Ph}(Cl) were also prepared and their pronerties compared with the dendritic catalyst precursors .. The supported catalyst species together with. analogous mononuclear model compounds were activated using a range of activating agents. Included amongst these activating agents are, silver salts of the type AgX, (where X = OS02CF3, Cl04 and BP); the perfluoroaryl borane, B(C6Fs)3 and MAO. The activated complexes were assessed for their. polymerisation ability towards ethylene. The dendrimers were characterised using techniques such as FTIR spectroscopy, 1 H NMR and 13C NMR spectroscopy, GC mass spectrometry and microanalysis. All new organometallic compounds produced were characterised using techniques such as 1 H NMR and 13C NMR spectroscopy. The polymers prepared were characterised by Gel Permeation Chromatography (GPC), Fourier Transform InfraRed (FTIR), 1 H and 13C NMR spectroscopy, Differential Scanning Calorimetry (DSC) as well as Scanning Electron Microscopy (SEM).