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dc.contributor.advisorRoodt, Andreas
dc.contributor.advisorVisser, Hendrik G.
dc.contributor.authorEngelbrecht, Ilana
dc.date.accessioned2018-06-15T12:37:15Z
dc.date.available2018-06-15T12:37:15Z
dc.date.issued2013-02
dc.identifier.urihttp://hdl.handle.net/11660/8421
dc.description.abstractEnglish: Hydroformylation for the production of aldehydes from alkenes, is a large and important homogeneously catalyzed industrial process. Most of these resulting aldehydes are hydrogenated to alcohols, having applications in plasticizer alcohols, detergents, wood preservatives and surfactants. Numerous phosphine ligands have been applied in these catalytic reactions signifying that changes in the ligand environment induce different steric and electronic properties into the catalyst system allowing to "tune" catalyst behaviour towards higher activity and selectivity. A series of diphosphinoamine (PNP) ligands with various substituents on the N-atom, inducing different steric properties were synthesized and characterized (Scheme I). Single crystal X-ray crystallographic studies of the PNP ligands revealed that the P-N-P bond angle decreases as the steric bulk of the alkyl moiety increases. See scheme in PDF full text. The synthesis and coordination of the PNP-ligands to Pt(ID and Pd(ID served as models to quantify different effects which could then be rationalized for the Rh(I) and Ir(I) pre-catalysts systems for use in olefin hydroformylation. The reason for using Pt(ID and Pd(ID was therefore primarily to gain information on the coordination mode of these ligands, rather than the notoriously difficult to isolate and unstable Rh and Ir complexes. A total of three free PNP-ligands, four [Pt(PNP-alkyl)2] and one [Pd(PNP-alkyl)2] solid state crystal structures were solved, which provided excellent structural fundamentals from which the catalysis could be pursued. The study was also supplemented with theoretical chemistry. The comparison between the optimized structure and the crystal data revealed small differences, illustrating that predictions can be made in terms of ligand design in particular when solid state data is hard to obtain. The calculated structures indicated that the phenyl ring arrangement is affected by the steric bulk of the nitrogen-coordinated alkyl moiety which could ultimately affect the catalytic selectivity. The steric demand of the ligands was defined by the Effective Tolman-based N-substituent steric effect (ON-sub). The electron donating ability was evaluated through the first order Pt-P coupling constants as determined from the corresponding Pt-PNP complexes showing no significant difference between electronic properties of the ligands. The hydroformylation of 1-octene was investigated utilizing Rh(I) and Ir(I) metal centres. The linearity of the aldehyde product increased with an increase in steric bulk of the ligand at the expense of side product formation during the rhodium catalyzed hydroformylation catalysis of 1-octene. A striking feature was that a 27 % improvement in the linear selectivity could be achieved by increasing the ON-sub angle of the N-substituent from 64 to 84 °. The parallel competing isomerisation of 1-octene varied from 63.7 % for a cone angle of 64 °, with a decrease to 27.3 % observed for PNP-Dimprop, with cone angle of 86 °. The N-alkyl moiety of the PNPligand can therefore be structurally fine-tuned towards efficient hydroformylation catalysts. Combining the PNP-ligands with PPh3 gives rise to a more superior system with higher reactivity and lower alkene loss through isomerisation. Iridium catalyzed hydroformylation did not yield the same trend of linear selectivity increase with an increase in Bi;-sub of the ligand, but did show similar behaviour to the Rh analogue when PPh3 was combined with the PNP-ligands.en_ZA
dc.description.abstractAfrikaans: Hidroformilering vir die produksie van aldehiede vanaf alkene is 'n groot en belangrike homogene katalitiese nywerheidsproses. Die meeste van die gevolglike aldehiede word gehidrogeneer na alkohole en word gebruik as plastiseerder alkohole, skoonmaakmiddels, hout preserveermiddels en benatters. Veelvuldige fosfienligande is al gebruik in hierdie katalitiese reaksies, wat aandui dat veranderinge in die ligandomgewing verskillende steriese en elektroniese eienskappe in die katalitiese stelsel veroorsaak en dus hoer aktiwiteit en selektiwiteit tot gevolg het. 'n Reeks difosfienamien (PNP) ligande met verskeie substituente op die N-atoom, wat verskillende steriese eienskappe veroorsaak, is gesintetiseer en gekarakteriseer (Skema I). Enkelkristal X-straal kristallografiese studies van die PNP ligande het onthul dat die P-N-P bindingshoek afneem wanneer die steriese massa van die alkielgroep toeneem. Sien skema in PDF volteks. Die sintese en koordinasie van die PNP-ligande aan Pt(II) en Pd(II) <lien as modelle om verskillende effekte te kwantifiseer, wat dan gebruik kan word in die Rh(!) en Ir(!) pre-katalitiese stelsel met toepassing in olefien hidroformilering. Die rede vir die gebruik van Pt(!!) en Pd(!!) is dus primer die inwinning van inligting aangaande die koordinasiemodus van hierdie ligande, eerder as die aansienlik moeilike isolasie van onstabiele Rh and Ir komplekse. 'n Totaal van drie vry PNP-ligande, vier [Pt(PNP-alkiel)2] en een [Pd(PNP-alkiel)2] vaste toestand kristalstrukture is opgelos, wat uitstekende strukturele beginsels voorsien het waaruit die katalise opgevolg kon word. Die studie word ook ondersteun deur teoretiese chemie. Die vergelyking van die geoptimaliseerde stukture en die kristaldata onthul klein verskille, wat illustreer dat voorspellings gemaak kan word in terme van ligand-ontwerp, veral wanneer vaste toestand data moeilik is om te verkry. Die berekende strukture loon aan dat die fenielringrangskikking beYnvloed word deur die steriese massa van die stikstof-gekoordineerde alkielgroep wat uiteindelik die katalitiese selektiwiteit sal beïnvloed. Die steriese eise van die ligande word gedefinieer deur die Effektiewe Tolman-gebaseerde Nsubstituent steriese effek (ON-sub). Die elektronskenkende vermoe is geevalueer deur die eerste orde Pt-P koppelingskonstantes soos vasgestel uit die ooreenstemmende Pt-PNP komplekse, wat aandui dat elektroniese eienskappe tussen die ligande nie beduidend verskil nie. Die hidroformilering van 1-okteen is ondersoek deur die gebruik van Rh(I) en Ir(I) metaalkerne. Die lineariteit van die aldehied produk neem toe met 'n toename in steriese massa van die ligand, ten koste van neweprodukvorming gedrurende die rodium-gekataliseerde hidroformileringskatalise van 1-okteen. 'n Treffende eienskap was dat 'n 27 % verbetering in liniere selektiwiteit bereik kon word deur die BN-sub hoek van die N-substituent van 64 na 84 ° te verhoog. Die parallel-kompeterende isomerisasie van 1-okteen wissel vanaf 63.7 % vir 'n keelhoek van 64 °, met 'n afname na 27.3 % waargeneem vir PNP-Dimprop, met 'n keelhoek van 86 °. Die Nalkielgroep van die PNP-ligand kan dus struktureel verfyn word ten opsigte van effektiewe hidroformileringskataliste. Die kombinasie van PNP-ligande met PF 3 lei tot 'n meer voortreflike stelsel met hoër reaktiwiteit en laer alkeenverlies as gevolg van isomerisasie. Iridium gekataliseerde hidroformilering het me dieselfde neiging van liniere selektiwiteitstoename met 'n toename in ON-sub van die ligand opgelewer nie, maar toon soortgelyke gedrag as die Rh analoog wanneer PPh3 met die PNP-ligande gekombineer is.en_ZA
dc.description.sponsorshipDepartment of Science and Technology (DST) of South Africaen_ZA
dc.description.sponsorshipNational Research Foundation (NRF)en_ZA
dc.description.sponsorshipDST-NRF centre of excellence (c*change)en_ZA
dc.description.sponsorshipSASOLen_ZA
dc.description.sponsorshipINKABA yeAfricaen_ZA
dc.description.sponsorshipUniversity of the Free Stateen_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectHydroformylationen_ZA
dc.subjectCatalysisen_ZA
dc.subject1-octeneen_ZA
dc.subjectCrystallographic studyen_ZA
dc.subjectDiphosphinoamineen_ZA
dc.subjectTheoretical studyen_ZA
dc.subjectSteric parameteren_ZA
dc.subjectMetal-PNP complexesen_ZA
dc.subjectIridiumen_ZA
dc.subjectIridium catalystsen_ZA
dc.subjectPlatinumen_ZA
dc.subjectMetal complexesen_ZA
dc.subjectThesis (Ph.D. (Chemistry))--University of the Free State, 2013en_ZA
dc.titleCoordination chemistry of iridium and platinum complexes as model homogeneous catalystsen_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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