Bulky metal complexes as model nanoscale catalysts
| dc.contributor.advisor | Roodt, Andreas | |
| dc.contributor.advisor | Bezuidenhout, Ben | |
| dc.contributor.author | Young, Cyril | |
| dc.date.accessioned | 2016-01-07T09:55:52Z | |
| dc.date.available | 2016-01-07T09:55:52Z | |
| dc.date.issued | 2012-11 | |
| dc.description.abstract | English: The lifestyle of modern society has created a massive demand for various chemicals such as fuels, chlorine-free refrigerants, high-strength polymers, stain-resistant fibres, cancer treatment drugs and thousands of other products. The demand for these compounds can only be met through the use of catalysts. Heterogeneous catalysis has become a fundamental part of the industrial scale production of these chemicals. Although heterogeneous catalysis is better suited for these processes than its homogeneous counterpart, some of the systems are plagued by poor distribution of the active metal species throughout the support. The aim of this study was to investigate the feasibility of synthesising robust, planar, bridging ligands that could act as spacers between active metal species in the deposition of active catalysts onto heterogeneous supports. By choosing different building blocks, for the simple Schiff base reaction, the distance and proximity between active metal species could theoretically be controlled for a desired application. 1,10-Phenanthroline and diamide type ligands (Figure 1) were identified as possible candidates for this application Figure 1: Different ligand systems identified as possible dispersion spacers. (A) represents the diamide type ligands and (B) the 1,10-phenanthroline ligands. The aim of this study was pursued by the identification and synthesis of building blocks such as 5,6-diamino-1,10-phenanthroline and 1,10-phenanthroline-5,6-dione which could act as bridging ligands and could be used to construct larger bridging systems. The bridging ligands and building blocks were coordinated to square planar metal centres such as platinum and palladium. This would enhance the possibility of creating a single layer network on the surface of the support. The ligands and complexes were characterised using solid state techniques and single crystal X-Ray Diffractometry to investigate the planarity of these species and the coordination mode to some of the diamide type complexes that have not found many applications in this field. The Heck coupling was identified as a standard reaction which could be utilised to test the catalytic properties of the palladium species. The catalytic activity of a range of diamide and 1,10-phenanthroline type ligands was evaluated after the optimisation of the Heck coupling. It was found that reducing the electron density on the five and six position of the phenanthroline ring drastically enhances the catalytic capabilities of these compounds. The diamide type complexes and larger bridging ligands showed less promising results. | en_ZA |
| dc.description.abstract | Afrikaans: Die lewenstyl van die moderne samelewing het 'n massiewe aanvraag na verskeie chemikalieë soos brandstof, chloor-vrye verkoelingsmiddels, hoë-sterkte polimere, vlekbestande materiaal, dwelms vir die behandeling van kanker en duisende ander produkte geskep . Die aanvraag na hierdie verbindings kan net nagekom word deur die gebruik van katalisators. Heterogene katalise is 'n fundamentele deel van die industriële skaal produksie van hierdie chemikalieë. Alhoewel heterogene katalise beter geskik is vir hierdie prosesse as homogene katalise, is 'n paar van die stelsels geteister deur swak verspreiding van die aktiewe metaalspesie dwarsdeur die steunraamwerke. Die doel van hierdie studie was om ‘n ondersoek in te stel na die haalbaarheid van die sintetisering van sterk, planêre, bruggende ligande wat die afstand tussen aktiewe metaal spesies op die heterogene steunraamwerke te kan beheer. Deurdat die keuse van die verskillende boustene vir die eenvoudige Schiff-basis reaksie te wissel, kan die afstand en nabyheid tussen aktiewe metaal spesies teoreties vir 'n gewenste kompleks beheer word. Die doel van hierdie studie is bewerkstellig deur die identifisering en sintese van die boustene soos 5,6-diamino-1,10-fenantrolien en 1,10- fenantrolien -5,6-dioon wat kan optree as oorbruggingsligande en gebruik kan word om groter oorbruggingsligande te bou. Die oorbruggingsligande en boublokke is gekoördineer aan vierkantig planêre metale soos platinum en palladium. Dit sal verder die moontlikheid van 'n enkellaag netwerk op die oppervlak van die steunraamwerke steun. Hierdie ligande en komplekse is gekarakteriseer deur gebruik te maak van vaste toestand tegnieke. Enkelkristal X-straaldiffraktometrie was gebruik om die planêriteit van hierdie spesies en die koördineringsmotief van sommige van die diamide tipe komplekse, wat nie baie toepassings vind in hierdie veld nie, te ondersoek. Die Heckkoppeling is geïdentifiseer as 'n standaard reaksie wat gebruik kan word om die katalitiese eienskappe van die palladium spesie te toets. Die katalitiese aktiwiteit van 'n reeks diamide en 1,10- fenantrolien tipe ligande is geëvalueer na die optimisering van die Heck koppeling. Daar is bevind dat die vermindering van die elektron digtheid op die vyf en ses posisie van die fenantrolien ring die katalitiese funksies van hierdie verbindings drasties verhoog. Die diamide en groter bruggingsligand tipe komplekse het minder belowende resultate getoon. | af |
| dc.identifier.uri | http://hdl.handle.net/11660/2040 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Thesis (Ph.D. (Chemistry))--University of the Free State, 2012 | en_ZA |
| dc.subject | Catalysis | en_ZA |
| dc.subject | Platinum | en_ZA |
| dc.subject | Palladium | en_ZA |
| dc.subject | Schiff Base | en_ZA |
| dc.subject | Bridging ligands | en_ZA |
| dc.subject | Heck coupling | en_ZA |
| dc.subject | Metal organic frameworks | en_ZA |
| dc.subject | Crystal structure | en_ZA |
| dc.title | Bulky metal complexes as model nanoscale catalysts | en_ZA |
| dc.type | Thesis | en_ZA |