Browsing by Author "Moss, John R"
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- ItemOpen Access[1,2-Bis(diphenylphosphino)ethane]-diiodidoplatinum(II) dichloromethane disolvate(2007) Sivaramakrishna, Akella; Su, Hong; Moss, John RIn the title compound, [PtI2(C26H24P2)]·2CH2Cl2, the PtI2(dppe) [dppe = 1,2-bis(diphenylphosphino)ethane] molecules possess twofold rotation symmetry. The Pt coordination displays a square-planar arrangement, with the sum of the angles around the Pt atom being 360.01 (2)°. The Pt-I distance is 2.6484 (5) Å. In the crystal structure, intermolecular C-H...I contacts link the PtI2(dppe) molecules into rows along the c axis, with a C...I distance of 3.873 (5) Å.
- ItemOpen AccessBulky cyclopentadienyl chromium complexes as ethene trimerisation catalyst precursors(2004) Blom, Burgert; Moss, John RThe process of ethene trimerisation to 1-hexene, has recently attracted considerable interest, in light of the usefulness of 1-hexene industrially. In this project the process of catalytic ethene trimerisation, using bulky cyclopentad ienyl chromium complexes was investigated. Firstly, a series of known and novel bulky cyclopentadiene ligands, of the type, C₅Ph₄RH (R = H, alkyl, aromatic or substituted aromatic group) were synthesised. Four routes were investigated. (i) Making use of an in situ generated bis-lithium intermediate, resulting in the formation of 1 ,2,3,4,5-pentaphenyl cyclopenta-1 ,3-diene and 1 ,2,3,4-tetraphenylcyclopenta-1 ,3-diene. (ii) The attempted use of a metallation I alkylation route which was unsuccessful. (iii) The use of tetracyclone as starting material, reacted with alkyl likthium reagents, or alkyl Grignard reagents which resulted in the formation of ligands, of the type C₅Ph₄R, with R in the 5 position of the ring (R = n-butyl, tertbutyl, hexyl). Unexpected side reactions afforded the isolation of two ligands of the type C₅Ph₄R, R = 1-propeneyl and ethyl, both with the terminal alkene function, saturated. (iv) The use of a Pd catalysed route, making use of Cp₂ZrCI₂ as source of cyclopentadiene, resulted in the successful isolation of the cyclopentadiene, C₅Ar₅H (Ar = C₆Me₂H₃). All new compounds were successfully characterised using NMR, IR, MS and elemental analysis. A stable Fe(II) model complex, bis-tetraphenylcyclopentadienyl iron, was prepared and cyclic voltametry conducted on it, to investigate the effect of phenyl substituents on a Cp ligand in the reduction I oxidation potential of the iron(II) centre. This study showed that phenyl rings on a cyclopentadiene ligand have a significant effect on the redox potential of Fe(II); this trend could possibly be expected with other metals, in particular chromium .
- ItemOpen AccessChloromethyl and methoxymethyl transition metal complexes : an investigation into their synthesis and reactivity(1981) Pelling, Simon; Moss, John RTransition metal methoxymethyl and chloromethyl complexes may be versatile starting materials for the synthesis of several types of new complexes, including hydroxymethyl and carbene complexes, respectively [LₙMCH₂OH] and [LₙMCH₂]⁺ (M=transition metal, L=ligands). Hydroxymethyl and carbene transition metal complexes are models of catalytic intermediates in the Fischer-Tropsch reaction. We have synthesized the new chloromethyl complexes [Ru(Cp)(CO)₂CH₂CI], [Re(CO)₅CH₂CI], and cis-[Mn(CO)₄(PPh₃)CH₂CI], and the new methoxymethyl The existence of rotational isomerism in the complexes [Ru(Cp)(CO)₂CH₂ocH₃] and the previously reported [Fe(Cp)(CO)₂CH₂OCH₃],⁴⁸ is proposed on the basis of infrared data. Mass spectra of several methoxymethyl and chloromethyl transition metal complexes have been recorded.
- ItemOpen AccessA computational and synthetic study of poly(benzyl phenyl ether) dendrimers(1998) Hughes, Samantha Jayne; Moss, John R; Naidoo, Kevin JOrganic and organochromium poly(benzyl phenyl ether) dendrimers have been investigated by synthetic · and computational methods. The first generation organic benzyl alcohol and bromide wedges have been prepared, and a first generation organic dendrimer was synthesised. The preparation of novel organochromium dendrimers has been investigated. Several chromium arene complexes were prepared by different routes, and the halogenation methodology was thoroughly explored with various reagents. The target compound, a chromium complexed first generation dendritic wedge, was not accessible by any of the methods investigated. The novel compound (dibenzyl ether)bis[tricarbonylchromium(O)] has been prepared by two routes and the crystal structure of this complex was determined. Several other chromium arene complexes were synthesised, and the crystal structure of one of these, (benzyl methyl ether)tricarbonylchromium(O), was determined. The structure and properties of the organic and organochromium dendrimers have been investigated by molecular mechanics and molecular dynamics techniques. The existing CHARMm polymer force field was extended to include parameters for the tricarbonylchromium moiety. The two crystal structures solved as part of the synthetic effort, were used in this regard. The accuracy of the new parameters was assessed by simulation of the crystal structure of ( dibenzyl ether)bis[tricarbonylchromium(O)]. The important ether linkage torsion angle parameter, which plays a significant role in the topology of the dendrimer, was singled out for refinement. The torsion angle was parameterised with the model compound benzyl phenyl ether, by fitting the CHARMm results for rotation about the dihedral, to ab initio torsional data. Molecular dynamics simulations have been performed on generations one through five of the organic and organochromium dendrimers. The radius of gyration and RMS variation were investigated as a function of generation for both dendrimer series. The radius of gyration was found to increase exponentially with generation, whereas the relationship of RMS variation to generation was not as well defined. Density distributions were calculated for all five generations of the organic and organometallic dendrimers. In addition, the distribution of the monomers from each generation within the dendrimer was analysed. In the later generation dendrimers, the monomers belonging to the earlier generations are extended, while the terminal groups are mobile and found in all regions of the dendrimer. The solvent accessible surface was calculated for the organochromium dendrimers. It was concluded from these results that although the terminal groups are mobile, the majority of these monomers remain on the periphery of the dendrimer, or in solvent accessible areas.
- ItemOpen AccessComputer simulations of Fréchet dendrimers in solutions(2005) Simpson, Stephen Charles; Naidoo, Kevin; Moss, John RThe structure and dynamics of dendrimers in solution are studied through nanosecond atomistic Molecular Dynamics (MD) simulations of explicitly solvated Fréchet dendrimers, generations G1 to G5. The properties of these dendrimers are investigated in four solvent invironments: vacuum and water (representatives of poor solvents), and tetrahydrofuran (THF) and chloroform (representatives of good solvents). To establish the quality of the solvent on the conformation of the dendrimer, additional nanosecond MD simulations fo the dendrimers are performed, from both inititally folded and unfolded conformations.
- ItemOpen AccessThe conversion of refinery materials into useful inorganic and organometallic precursors(2005) Chiririwa, Haleden; Moss, John R
- ItemOpen AccessDevelopment of Pd(II)- and Pt(II)-based catalysts for polymerisation and oligomerisation of [alpha]-olefins(2001) Ndlovu, Mazwi Eugene; Moss, John R; Bourne, Susan AThe polymers were investigated by DSC and TGA to determine their melting point endotherms and thermal stability. All polymers exhibited low thermal stabilities and low melting point endotherms.
- ItemOpen AccessElectrochemical behaviour of some organometallic compounds containing iron and molybdenum(1996) Daries, Keith Louis; Moss, John RThe electrochemical behaviour of some mononuclear alkyl compounds of the types CpFe(CO)₂(CH₂)nCH₃ (n = 0 to 11, Cp = η-C₅H₅), CpMo(CO)₃(CH₂)nCH₃ (n = 3,4,17) have been investigated in aprotic solvents. The cyclic voltammograms obtained for all the iron alkyl compounds suggest similar behaviour after the initial oxidation. The oxidation potentials showed no linear correlation with the corresponding lengths of the alkyl chain, but could, however, be interpreted with the available Tolman's χ-values. The subsequent CO insertion reaction to give an acyl species was found to be dependent on the nucleophilicity of the solvent. The relative rates of decarbonylation of the acyl species could be assessed through cyclic voltammetry. The electrochemical behaviour of heterobimetallic complexes of the type CpFe(CO)₂(CH₂)nMo(CO)₃Cp (n = 3 to 6) was found to be solvent dependent. The anodic waves obtained for these complexes in acetonitrile showed up as two closely spaced waves. Our results suggest that the two metals in CpFe(CO)₂(CH)nMo(CO)₃Cp behave independently, with the iron end of the molecule being oxidized first, followed by CO insertion/alkyl migration at this end.
- ItemOpen AccessHalo- and organogold(I) complexes as potential metallomesogens(1999) Hess, Fiona Millicent; Moss, John RThere is currently much interest in how the properties of liquid crystals may be altered by metal atoms. Gold(I) complexes of the type RAuL have recently been shown to exhibit interesting liquid crystal behaviour. As molecular structure and intermolecular forces play a major role in liquid crystal chemistry, changing the nature of the R and L groups result in changes mesomorphic properties. The aim of the project was to synthesise RAuL complexes with stilbazole ligands and to investigate how different R groups influence the liquid crystal properties. ClAu(n-OST) complexes, n-OST = trans-4,4'-alkoxystilbazole with n = number of carbon atoms in the alkoxy chain, were synthesised from ClAu(tht) and n-OST. They were found to exhibit smectic A mesophases, melting between 135-153 °C and decomposing at the clearing point at 168-180 °C. The transition temperatures decreased as the chain length of the n-OST ligand increased.
- ItemOpen AccessHeterometallic complexes containing cobalt and chromium : synthesis, characterization and properties(1991) Domingo, Mark Russell; Moss, John RHeterometallic transition metal complexes have been extensively studied and the synthesis and chemistry of many complexes of the type has been reported. This thesis focuses on heterometallic complexes containing cobalt and chromium.
- ItemOpen AccessAn investigation into the alkene hydroformylation reaction using platinum complexes(2009) Kistamurthy, Deshen; Moss, John R; Smith, Gregory SHydroformylation is the most widely applied homogeneous catalysis reaction used in industry. The aldehyde product is an important commodity in both the bulk and specialty chemical industry. Platinum catalysts have shown significant chemo- and regioselectivities in alkene hydroformylation. This thesis investigates the activity as well as selectivity of platinum complexes containing bidentate ligands in the hydroformylation reaction.
- ItemOpen AccessAn investigation into the synthesis and structure of some pentamethylcyclopentadienyl complexes of molybdenum, tungsten and iron(1984) Stretch, Phillippa Moira; Moss, John RThe extensive series of cyclopentadienyl transition metal complexes known, has made of interest the corresponding chemistry of pentamethylcyclopentadienyl transition metal derivatives, and other substituted cyclopentdienyl species. In the study two synthetic routes are described for the synthesis of new halomethyl complexes of molybdenum, tungsten and iron.
- ItemOpen AccessLigand-bridged dinuclear carbonyl compounds of rutheniun and osmium(2008) Mushonga, Paul; Moss, John R; Haines, Raymond JLigand-bridged dinuc1ear carbonyl compounds of ruthenium and osmium have been successfully prepared and characterised by various analytical and spectroscopic techniques. X-ray crystal structures have been determined for the osmium complexes [OS2(CO)4(p-02CCsH4FeCsHs)2L2] {L = PPh3 (102), py (103)}. Some of the complexes were then investigated for their catalytic activity in the oxidation of cyc10hexane and octane. In this work, hydrogen peroxide was used as an oxidant and acetonitrile as the solvent. A higher selectivity for the alcohol products over the ketones was observed. The average ratio of alcohols to ketones was found to be 4.56 and 1.76 for cyc10hexane and octane respectively. The complexes [OS2(CO)6(p-02CMeh] (4) [Ru(CO)2(p-02CMe)2]n (86), [Ru2( CO )4(p-02CMe )(p-dppm h] [PF 6] (117) and [Ru2( CO)4(p -( 02CMe h(MeCN)2] (118), were tested as homogeneous catalysts for the isomerisation of terminal alkenes. Complex 4 was inactive while the complex 118 gave a 100 % conversion. It is proposed that the catalysis proceeded via the displacement of one acetonitrile ligand from the metal centre providing a vacant site onto which the substrate coordinated. The redox behaviour of the four complexes [Ru2(CO)2(p-COh(
- ItemOpen AccessModeling Diiron enzymes for alkanes activation(2008) Shiimi, Annatolia; Moss, John R; Smit, MSThe synthesis and characterization of a series of ruthenium 'sawhorse' complexes of the type [RU2(IJ-02CRh(CO)4(Lh]' has been successfully carried out. The complexes have been characterized by IR, 1H and 13C NMR spectroscopy, elemental analysis as well as by mass spectrometry.
- ItemOpen AccessModification of aspirin derivatives by coordination to iron and manganese(2000) Mshicileli, Ndumiso; Moss, John R; Chibale, KellyIn this work new metal complexes of acetylsalicylic acid (aspirin) derivatives have been synthesised. Complexes that were studied were those of manganese (Mn) and iron (Fe).
- ItemOpen AccessNew mono and bimetallic chloroquine derivatives : synthesis and evaluation as antiparasitic agents(2002) Blackie, Margaret Anne Lillias; Moss, John R; Chibale, KellySeveral series of new ferrocenyl-quinoline antimalarial agents have been synthesised and fully characterised using standard spectroscopic and analytical techniques. The molecular structure of N-(7-Chloro-quinolin-4-yl)-N'-[2 -( N”,N""-dimethylaminomethyl)ferrocenylmethyl]-ethane-1.2-diamine has been determined by x-ray crystallography. N-(7-Chloro-quinolin-4-yl)-N'-[2-( N”, N""-dimethylaminomethyl)ferrocenylmethyl]-alkyl-1 ,n-diamine compounds were made where n = 2-6. These compounds contain a reactive secondary amine centre through which derivatisation to form aryl urea and aryl sulfonamide compounds was achieved. Complexes of the types: triphenylphosphine(L)gold(l) nitrate, pentafluorophenyl(L)gold(l) and chloro(cyclooctadiene)(L)rhodium(l) have been synthesised (where L = chloroquine, ferroquine, N-(7-chloro-quinolin-4-yl)-N'-[2-( N”, N""-dimethylaminomethyl)ferrocenyl methyl]-ethane-1 ,2-diamine, 3-benzyl-1-[2-(7-chloro-quinolin-4-ylamino)-ethyl]-1-[2-(N"",N""-dimethylaminomethyl)-ferrocenylmethyl]urea). All compounds have been evaluated against chloroquine sensitive and chloroquine resistant strains of Plasmodium falciparum. In most cases good activity was found in both strains of the parasite. N-(7-Chloro-quinol in-4-yl)-N'-[2 -( N”, N""-dimethylaminomethyl)ferrocenyl methyl]-alkyl-1, n-diamine compounds have been made where n = 2-6. It was found that in vitro efficacy against P. falciparum diminished with increasing spacer length. The introduction of the aryl urea moiety served to influence efficacy towards P. falciparum and toxicity towards mammalian cells. In some cases the toxicity was significantly reduced accompanied by an improvement in efficacy. The coordination complexes where L = chloroquine showed improved efficacy in the chloroquine resistant K1 strain of P. falciparum. In the heterobimetallic complexes, the ligand L showed equivalent or better in vitro efficacy than the coordination complexes of L against both chloroquine sensitive D10 and chloroquine resistant K1 strains of P. falciparum. Preliminary structure-activity studies were carried out on some of the prepared compounds. Phenylene analogues of some of the ferrocenyl compounds have been synthesized and it was found that the analogues show similar in vitro efficacy to each other in both chloroquine sensitive 3D7 and chloroquine resistant K1 strains of P. falciparum. The presence of a ferrocenyl moiety in the side chain of chloroquine analogues appears to have a synergistic or additive effect on in vitro efficacy.
- ItemOpen AccessNi(II) and Pd(II) based catalysts for α-olefin polymerisation(1999) Moni, Lucky; Moss, John RA variety of Ni(II) and Pd(II) based catalysts have been synthesised and used in homopolymerisation of ethylene and 1-hexene at room temperature.
- ItemOpen AccessOlefin oligomerization reactions theoretical studies using cyclometallated palladium(II) catalysts and experimental studies on platinum(II) analogues(2012) Zheng, Feng; Moss, John R; Hutton, Alan T; Mapolie, Selwyn F; Van Sittert, Cornie GCEEthylene oligomerization reactions catalysed by cyclometallated palladium(II) N-benzylidenebenzylamine complexes were studied theoretically. Density functional theory (DFT) calculations are reported on the interaction of various MAO models with the methylated pre-catalyst. The neutral MAO dissociation process is shown to remain the major interaction that takes place in the Pd/MAO interactions. On the other hand, the formal methyl abstraction process could be also feasible if more energy is provided. Therefore, the relative energies were calculated for intermediates and transition states for both Cossee-type and metallacycle mechanisms.
- ItemOpen AccessOligomerization of higher olefins(2010) Kekana, Lizzy Mpho; Moss, John R; Hunter, Roger; Botha, SubeliaA series of new substituted cyclopentadienyl ligands and their chromium complexes were successfully synthesised and characterised using a wide range of analytical and spectroscopic techniques such as NMR, mass spectrometry, elemental analysis and melting points.The ligands were then tested for the oligomerization of ethylene and 1-hexene. The chromium complexes were tested for the oligomerization of 1-hexene.
- ItemOpen AccessRuthenium and osmium complexes as catalyst precursors for Fischer-Tropsch synthesis(2004) Bungane, Ntombovuyo; Moss, John R; Claeys, Micheal; Van Steen, EricRuthenium complexes of several types have been synthesized, supported on silica and their activity in CO hydrogenation was investigated in order to determine the cluster size of surface Ru atoms required for the formation of hydrocarbons. Previous studies have shown that more than one metallic site is needed for the Fischer-Tropsch synthesis.
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