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dc.contributor.authorConradie, Jeanet
dc.date.accessioned2016-11-16T09:16:57Z
dc.date.available2016-11-16T09:16:57Z
dc.date.issued1999
dc.identifier.urihttp://hdl.handle.net/11660/4551
dc.description.abstractEnglish: Synthetic routes to prepare new Rh(I)-β-diketonate complexes [Rh(FcCOCHCOR)(CO)2] and [Rh(FcCOCHCOR)(CO)(PPh3)] with Fc = ferrocenyl and R = Fc, C6H5, CH3 and CF3 have been developed and optimized. Optimized synthetic routes to iridium(I) complexes, [Ir(R'COCHCOR)(cod)], with R' = Fc and R = C6H5, CH3 and CF3, or with R' = CF3 and R = CH2CH3, CH(CH3)2 and C(CH3)3 have also been developed. 1H and 31P NMR studies indicated that for complexes of the type [Rh(β-diketonato)(CO)(PPh3)] with an unsymmetrical β-diketonato ligand, at least two main isomers exist in solution. The structure of one isomer of [Rh(fctfa)(CO)(PPh3)], as well as crystal structures of FcCOCH2COCF3, [Rh(fctfa)(CO)2] and [Rh(fctfa)(CO)(PPh3)(CH3)(I)] were solved. The chemical kinetics of the oxidative addition of iodomethane to [Rh(FcCOCHCOR)(CO)(PPh3)] has been studied utilizing IR, UV/visible, 1H NMR and 31P NMR techniques. The NMR studies revealed that the rate of oxidative addition of iodomethane to the different [Rh(FcCOCHCOR)(CO)(PPh3)] isomers was the same. A complete general reaction sequence for the oxidative addition of iodomethane to all [Rh(bidentate ligand)(CO)(PPh3)] complexes is: First set of reactionsSecond set of reactionsThird set of reactions{[Rh(III)-alkyl1] [Rh(III)-acyl1] }K2=k2/k-2Rh(I)+ CH3I k1k-1k3k-3k4k-4[Rh(III)-alkyl2][Rh(III)-acyl2] 1H and 31P NMR studies further showed that all rhodium-containing complexes in the above mentioned reaction scheme, are actually composed of at least two main isomers, that is Rh(I)A the rate of substitution becomes faster when the group electronegativity of the R groups increases. This tendency is, as expected, exactly the opposite to what was observed during oxidative addition. A general reaction mechanism for both Rh and Ir complexes was presented. An additional study on the rate of the β-diketonato substitution with 1,10-phenanthroline in complexes of the type [Ir(CF3COCHCOR)(cod)] with R = CH3, CH2CH3, CH(CH3)2 and C(CH3)3 showed that the size of R does not hamper the rate of substitution. All substitution reactions were independent of a solvent step. The cyclic voltammetry study of all the ferrocene-containing β-diketonato complexes of rhodium(I) and iridium(I) synthesized, exhibited a single electrochemically reversible redox couple corresponding to the formal reduction potential of the ferrocenyl group of the β-diketonato ligand coordinated to the rhodium or iridium complexes, as well as an electrochemically irreversible anodic oxidation peak which corresponds to the oxidation of the metal = Rh or Ir. The 31P NMR study on different six-membered chelate complexes, [Rh(L,L'-BID)(CO)(PPh3)], and related Rh(III) complexes, indicated a general decrease in coupling constants 1J(31P-103Rh) as the Rh-P bond length, determined by X-ray crystallography, increases according to the relationship d(Rh-P) = -0.0014(1) x 1J(31P-103Rh) + 2.49(2). The Rh-P bond lengths, d(Rh-P), varied between 2.23 Å and 2.36 Å. The electron density on the Rh(I) and Ir(I) metal centres was manipulated over a wide range by changing the R group on the coordinated ligand (FcCOCHCOR)- from the highly electron donating Fc group (χFc = 1.87) to C6H5, (χC6H5 = 2.21) to CH3(χCH3 = 2.34) to the strongly electron withdrawing CF3 group (χCF3 = 3.01). The effect of the different R groups on the β-diketonato ligand (FcCOCHCOR)- coordinated to the rhodium(I) and iridium(I) complexes was not only observed in kinetic rate constants, but also in formal reduction potentials of the ferrocenyl group, the oxidation potential of Rh(I) or Ir(I), pKa-values, IR stretching frequencies, and crystallographic bond lengths.en_ZA
dc.description.abstractAfrikaans: Sintese-tegnieke om nuwe Rh(I)-β-diketonato komplekse [Rh(FcCOCHCOR)(CO)2] en [Rh(FcCOCHCOR)(CO)(PPh3)] met Fc = ferroseniel en R = Fc, C6H5, CH3 and CF3 te berei, is ontwikkel en geoptimiseer. Geoptimiseerde sintese-tegnieke vir die bereiding van iridium(I) komplekse, [Ir(R'COCHCOR)(cod)], met R' = Fc en R = C6H5, CH3 en CF3, of met R' = CF3 en R = CH2CH3, CH(CH3)2 en C(CH3)3, is ook ontwikkel. 1H- en 31P-KMR-studies van die komplekse [Rh(β-diketonato)(CO)(PPh3)] wat ‘n asimmetriese β-diketonato-ligand bevat, het aangetoon dat daar ten minste twee isomere van hierdie komplekse in oplossing bestaan. Die kristalstruktuur van een van die isomere van [Rh(fctfa)(CO)(PPh3)], asook die kristalstrukture van FcCOCH2COCF3, [Rh(fctfa)(CO)2] en [Rh(fctfa)(CO)(PPh3)(CH3)(I)] is opgeklaar. Die oksidatiewe addisie van metieljodied aan [Rh(FcCOCHCOR)(CO)(PPh3)] is deur middel van infra-rooi, UV/sigbaar, 1H-KMR en 31P-KMR-spektroskopie ondersoek. Die KMR-studies het getoon dat die tempo van oksidatiewe addisie van metieljodied aan die verskillende [Rh(FcCOCHCOR)(CO)(PPh3)] isomere, dieselfde was. Die voorgestelde algemene reaksieskema vir die oksidatiewe addisie van metieljodied aan [Rh(bidentate-ligand)(CO)(PPh3)] komplekse is: Eerste stel reaksiesTweede stel reaksiesDerde van reaksies{[Rh(III)-alkiel1] [Rh(III)-asiel1] }K2=k2/k-2Rh(I)+ CH3I k1k-1k3k-3k4k-4[Rh(III)-alkiel2][Rh(III)-asiel2] Die 1H- en 31P-KMR-studies het verder aangetoon dat alle rodiumbevattende komplekse in bogenoemde reaksieskema uit minstens twee isomere bestaan, naamlik Rh(I)A Resultate van die substitusiekinetika van [Rh(FcCOCHCOH)(cod)] en [Ir(FcCOCHCOR)(cod)] (R= CF3, CH3 and C6H5) met 1,10-fenantrolien, het aangetoon dat die tempo van substitusie toegeneem het namate die groepelektronegatiwiteit van die R-groepe toegeneem het. Soos verwag, is hierdie tendens die teenoorgestelde as wat in die geval van oksidatiewe addisie waargeneem is. ‘n Algemene reaksieskema vir beide rodium en iridium komplekse is voorgestel. ‘n Addisionele studie van die tempo van substitusie van die β-diketonato-ligand met 1,10-fenantrolien in komplekse van die tipe [Ir(CF3COCHCOR)(cod)] met R = CH3, CH2CH3, CH(CH3)2 en C(CH3)3, het aangetoon dat die grootte van R nie die tempo van substitusie vertraag nie. Alle substitusiereaksies was onafhanklik van ‘n oplosmiddelroete. Die sikliese voltammetriese studie van alle gesintetiseerde ferroseen-bevattende β-diketonato-komplekse van rodium(I) en iridium(I), het ‘n elektrochemies omkeerbare redox koppel bevat, wat ooreengestem het met die formele reduksiepotensiaal van die ferrosenielgroep van die β-diketonato-ligand gekoördineer aan die rodium of iridium komplekse, asook ‘n chemies onomkeerbare anodiese oksidasiepotensiaal, wat ooreengestem het met die oksidasie van rodium of iridium. Die 31P-KMR-studie van verskillende seslid chelaatkomplekse, [Rh(L,L'-BID)(CO)(PPh3)], en verwante Rh(III) komplekse, het ‘n algemene afname in die koppelingskonstante 1J(31P-103Rh) getoon namate die kristallografies bepaalde Rh-P bindingslengtes toegeneem het, met die lineêre verwantskap d(Rh-P) = -0.0014(1) x 1J(31P-103Rh) + 2.49(2). Die Rh-P bindingslengtes, d(Rh-P), het tussen 2.23 Å en 2.36 Å gewissel. Die elektrondigtheid op die Rh(I) and Ir(I) metaalsentra is oor ‘n groot gebied gevarieër deur die R-groep op die gekoördineerde (FcCOCHCOR)- ligand te wissel vanaf die sterk elektrondonerende Fc-groep (χFc = 1.87), na C6H5, (χC6H5 = 2.21), na CH3 (χCH3 = 2.34), en na die sterk elektrononttrekkende CF3-groep (χCF3 = 3.01). Die invloed van die verskillende R-groepe op die gekoördineerde β-diketonato-ligand (FcCOCHCOR)- aan die rodium(I) and iridium(I) komplekse, is nie alleenlik in die kinetiese tempokonstantes waargeneem nie, maar ook in die formele reduksiepotensiale van die ferrosenielgroep, die oksidasiepotensiaal van Rh(I) of Ir(I), pKa-waardes, karbonielstrekkingsfrekwensies, en kristallografies bepaalde bindingslengtes.af
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectThesis (Ph.D. (Chemistry))--University of the Orange Free State, 1999en_ZA
dc.subjectElectrochemical analysisen_ZA
dc.subjectChemical kineticsen_ZA
dc.subjectRhodium(I)en_ZA
dc.subjectIridium(I)en_ZA
dc.subjectOxidative additionen_ZA
dc.subjectSubstitution kineticsen_ZA
dc.subjectCyclic voltammetryen_ZA
dc.subjectGroup electronegativityen_ZA
dc.subjectCrystallographyen_ZA
dc.titleChemical kinetics, electrochemistry and structural aspects of ferrocene-containing b-diketonato complexes of rhodium(I) and iridium(I)en_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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