Dissertations / Theses on the topic 'Rh(I) chemistry]'

The catalytic hydrogenation of substituted benzenes to saturated cyclic products is an industrially relevant reaction. It is important in the production of fine chemicals, petroleum and in the fuel industry. It is used in the process of lowering the aromatic content in diesel fuels to follow up the up-to-date environmental legalisation. It has been widely reported that aromatic ring hydrogenation is a structure insensitive reaction, however more recent studies have suggested that structure sensitivity may indeed exist. Therefore, the demand to perform more research on substituted benzenes to understand their behaviour during the hydrogenation has increased. Unlike most of what was found in literature, this study involved substituents which include methyl, ethyl, propyl, hydroxyl and methoxy groups. These reactions were performed at different parameters of temperatures, H2 pressure and concentrations and over Rh/SiO2 catalyst. Different mechanisms were suggested for the hydrogenation of aromatic compounds. A stepwise mechanism is generally accepted to explain the reaction mechanism. This suggestion was built on the fact aromatic adsorption is zero order in aromatics which suggests a strong adsorption of the substrates. This mechanism was confirmed in this work by the observation of alkyl cyclohexenes as intermediates during the hydrogenation of alkyl benzenes. Interesting points were observed during the hydrogenation of phenols. Firstly, cyclohexane was formed independently and directly from the original phenol. This observation was not found in most of previous studies. The other point was that phenol and anisole reacted in different ways from each other. Phenol was found to react in three independent routes, the formation of cyclohexanone, the formation of cyclohexanol and the formation of cyclohexane. Whereas, cyclohexanol was not formed directly from anisole, it was formed from cyclohexanone and after the total conversion of anisole. Competitive hydrogenations were also executed in order to investigate the behaviour of different groups in the same reaction. The findings of these tests were different from what was observed during the solo tests. As for the hydrogenation of alkylbenzenes, a steric effect might explain the differences between these substrates. It was observed that the reaction rate decreased as the alkyl group attached to the ring increased. These findings were not the same during the competitive hydrogenation. n-Propylbenzene, which has a larger group attached to the aromatic ring, showed higher reactivity in the presence of toluene and ethylbenzene, which suggests that the steric effect was not the only factor affecting the hydrogenation of substituted benzenes. These findings were explained by an electronic effect applied by the alkyl groups attached to the ring. The effect of these groups increases as the group size increases. In addition to steric and electronic effects, the mode of adsorption was also suggested to affect the competitive hydrogenations of phenols. Different modes of adsorption and different medium species formed leads to different behaviour during the competitive hydrogenation. In addition, NMR analysis was performed on selected samples from toluene and deuterated toluene reactions with deuterium and hydrogen. Toluene reaction with deuterium showed that all hydrogen atoms were replaced by deuterium at the beginning of the reaction. It was also shown from NMR results that -CD3 group was contacted to the surface which confirms the ability of -CH3 group to be adsorbed to the surface as well as the aromatic ring.

Chapter 1.Copper-Catalysed Borylative Coupling of Vinylazaarenes and N-Boc Imines. Methodology for the copper-catalysed three-component couplings of vinylazaarenes, bis(pinacolato)diboron, and N-Boc imines has been developed. Oxidation of the initially formed boron species gives azaarene-containing, Boc-protected amino alcohols with reasonable to good diastereoselectivities. Additionally the synthetic utility of the reaction products have been demonstrated. The crude boron species have been shown to undergo a Suzuki-Miyaura cross coupling to give further functionalised products. Finally, facile deprotection of the reaction products is possible. Chapter 2. Chain Walking of Allylrhodium Species in Rhodium-Catalysed Nucleophilic Allylations of Imines and Aldehydes. Allylrhodium species derived from δ-trifluoroboryl β,γ-unsaturated esters undergo chain walking towards the ester moiety. The resulting allylrhodium species react with imines to give products containing two new stereocenters and a Z-alkene. By using a chiral diene ligand, products can be obtained with high enantioselectivities. A pronounced matched/mismatched effect with the chirality of the allyltrifluoroborate is also observed. In an analogous reaction a rhodium-hydride species has been shown to catalyse the addition of diene esters and aldehydes via allylrhodium intermediates which also undergo chain walking towards the ester moiety. The methodology enables allylation of aromatic aldehydes with compounds containing both diene and ester functionalities linked by carbon chains of up to eight carbons in length.

The Rh(III)-catalysed oxidative C–H allylation and homoallylation of N-acetylbenzamides with 1,3-dienes is described. The presence of allylic hydrogens cis to the less substituted alkene of the 1,3-diene is important for the success of these reactions, though not essential. With the assistance of reactions using deuterated 1,3-dienes, a proposed mechanism is provided. The key step is postulated to be the first reported examples of allyl-to-allyl 1,4-Rh(III) migration. Importantly, migration to primary or secondary allylic position results in allylation products, whereas migration to a tertiary position leads to homoallylation. Using 1,4-dienes as the coupling partner, N-tosylbenzamides are homoallylated. Preliminary results indicate a mixture of isomer products, with major isomer resulting from an allyl-to-allyl 1,4-Rh(III) migration.

The structural chemistry and magnetic properties of compounds isostructural with La₁₈Li₈Rh₅O₃₉ have been studied. In this cubic structure (space group Pm^_₃n), [111] chains of alternating RhO₆ octahedra (2a, 8e sites) and LiO₆ trigonal prisms (16i site) occupy channels within a La-O framework. In order to study the consequences of both reducing the dimensions of the channels and introducing paramagnetic cations into both the framework and the polyhedral chains, compositions in the series Nd₁₈Li₈Rh_5-xFe_xO₃₉ (1 ≤ x ≤ 4) have been synthesised and characterised by magnetometry, neutron diffraction and Mössbauer spectroscopy. Iron preferentially occupies the 2a site as low-spin Fe(IV) and the larger 8e site as high-spin Fe(III). Compositions having x > 1 show spin-glass-like behaviour below ~5 K. The behaviour of this series of compositions has been compared with that of the known series La₁₈Li₈Rh_5-xFe_xO₃₉. In order to facilitate this comparison, the structure of La₁₈Li₈Fe₅O₃₉ has been fully characterised by both neutron diffraction and EXAFS. The use of both techniques has revealed differences between the mean and local environments of iron. In order to explore and extend the range and combinations of elements that can be accommodated in this structure, the Ti-containing compounds Ln₁₈Li₈M₄TiO₃₉ (Ln=La,Nd,Pr,Sm; M=Rh,Fe,Co) have been synthesised. Nd₁₈Li₈Fe₄TiO₃₉ was selected for a detailed study by magnetometry, neutron diffraction, Mössbauer spectroscopy and XANES. Cations were found to be stabilised in unusual oxidation states and disordered over three sites of the Nd₁₈Li₈Fe₄TiO₃₉ polyhedral chains. The 8e site is occupied by high-spin Fe³⁺, Ti³⁺ and Li⁺ in a ratio of 76:20:4; the 2a site by low-spin Fe⁴⁺ and Ti⁴⁺ in a ratio of 79:21 and the trigonal-prismatic 16i site by Li⁺ and Fe³⁺ in a ratio of 98:2. Nd₁₈Li₈Fe₄TiO₃₉ undergoes a transition to a spin-glass state at 4.25(5) K, whereas La₁₈Li₈Fe₄TiO₃₉ revealed a different type of magnetic transition at ~8 K. The nature of this transition is not yet clear. Monophasic samples could not be prepared in the Nd/Rh system and cation vacancies were found in Nd/Co. No pure samples of Sm-containing compositions could be prepared, while the only Pr composition which was obtained pure, according to X-ray diffraction, Pr₁₈Li₈Co₄TiO ₃₉ shows the similar magnetic properties to Pr₁₈Li₈Co₃TiO₃₉. The compositions Ln₁₈Li₈M₃ M'O₃₉ (Ln=La,Nd,Pr,Sm; M,M'=Fe,Co,Ti) with 25% of the 8e sites vacant have been investigated. The Co-containing compositions Nd₁₈Li₈Co₃FeO_39-y, Nd₁₈Li₈CoFe₃O_39-y and Nd₁₈Li₈Co₃TiO_39-y were characterised by neutron diffraction. Cation vacancies on the 8e sites were found to coexist with anion vacancies around the 2a sites. The remaining octahedral sites are occupied by a disordered arrangement of transition-metal cations. The trigonal-prismatic sites are fully occupied by Li except in the case of Nd₁₈Li₈CoFe₃O_39-y where some Fe is present, as confirmed by Mössbauer spectral data. Antiferromagnetic interactions are present on the Nd sublattice in each composition, but a spin glass forms below 5 K when a high concentration of spins is also present on the octahedral sites. The magnetic character of the Ln cations plays an important role in determining the properties of these compounds. Long-range magnetic order of the transition-metal cations was not observed in any compositions. Although this might be partly attributable to the cation disorder in the polyhedral chains, the apparent antiferromagnetic behaviour of Nd-containing compositions in which the transition metals have a low magnetic moment, e.g. Nd₁₈Li₈Co₃TiO_39-y, and the marked contrast between certain La and Nd compositions in which the transition metal content is the same, e.g. Nd₁₈Li₈Fe₄TiO₃₉ and La₁₈Li₈Fe₄TiO₃₉, suggests that the Ln sublattice is fully involved in determining the magnetic behaviour.

Thesis (PhD)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: Radiochemical separation of 103Pd from natAg, usmg a 66 MeV proton-induced reaction at iThemba LABS, was studied and a radiochemical method was developed for the separation. For the separation, which comprises the separation of Pd from a large amount of target material (16 g Ag), as well as Rh radioisotopes produced from decay of their Pd parents (mainly 101Rhand IOORh),three ion exchange resins were tested: a Chelex 100 chelating resin, the AG 1-X8 anion exchange resin and a AG MP-I anion exchange resin. For the optimum elution ofPd from the latter two resins, two elution curves using water and 5% ammonia solution, were obtained. With an average recovery of 97.4% and sharper elution curve from the macroporous AG MP-I, this resin was finally chosen for routine production. To achieve the separation, a simple, easily operated radiochemical processing system was designed and installed in a hot cell. Radiochemical separation of 103Pd from a Rh target was also studied and several cation and anion exchange resins were tested. A carrier-free separation of 103Pd was developed, using an AG 1-X8 anion exchange resin. Bombarded tablets of RhCh.3H20, as the targets, were used for these separations. The procedure, originally designed for the separation of Pd from Cu and Rh, was modified using H202 for the oxidation of Ru prior to the sorption on the resin and successfully used for the separation of isotopes of Rh from the isotopes of Pd, Ru, Tc, Nb, Mo, Zr and Y, which were produced by 400 MeV 160_ and 12C-induced RhCb.3H20 targets. To elute the Pd from the resin, 5% ammonia solution was used; the recovery was about 92%. To prepare the Rh target for routine production, an electroplating method of Rh on a Cu substrate was developed. Rh(CI04)3, in 0.5 M perchloric acid, was used as the electrolyte bath. The electroplated Rh was then dissolved by an alternating current technique, using 6 M HCI and a current density of 2 Alcm2. For production of the seeds, I03Pd was sorbed on the weakly basic anion exchange resin Amberlite IRA-93 (600-700 Il), by recycling a 0.5 M Hel solution of Pd through a 0.5 cm x 1 cm column for 2 hours. The distribution of I03Pd on the resin beads was measured and RSD of5.7% was obtained. A funnel was designed to transfer the I03Pd-loaded resin beads into the Ti tubes to prepare the seeds (0.7 mm LD., 0.8 mm D.D., and 4.5 mm length). To enclose the tubes as capsules, the end caps were made from 0.02 mm Ti sheet and several pieces were designed and machined for the welding of the caps to the tubes. A spotwelding machine was used for the welding, after small, but vital modifications.
AFRIKAANSE OPSOMMING: Palladium-l03 kan volgens twee produksieroetes by iThemba LABS vervaardig word, naamlik deur die volgende protongeïnduseerde reaksies: natAg(p,xn)lo3Cd (ty,=7.3 m) ~ 103Ag (ty,=1.1 h) ~ 103Pden I03Rh(p,n) ~ 103Pd. 'n Radiochemiese metode om 103Pd van die Ag-skyfmateriaal te skei, is ontwikkel. Hierdie metode, wat gebaseer is op anioonuitruilerchromatografie met die makroporeuse hars AG MP-I, behels die skeiding van I03Pd van 'n groot hoeveelheid skyfmateriaal (16g Ag), sowel as van Rh-radionukliede (hoofsaaklik looRh en IOlRh), wat geproduseer word deur die verval van hulle Pd-moederisotope. As die Pd met 5% ammonia oplossing geëlueer word, is 'n 97.4% herwinning moontlik. 'n Radiochemiese paneel is ontwerp, gebou en in 'n warmsel geïnstalleer vir roetine produksie. 'n Metode om Rh op 'n kopersubstraat te elektroplateer is ook ontwikkel om 'n Rh-skyf te verkry vir die protonbombardement. 'n Oplossing van 0.5 M HCI04 - Rh(HCI04)3 is as die elektrolietbad gebruik. Die geëlektroplateerde Rh is opgelos in 6 M HCI deur gebruik te maak van 'n wisselstroomtegniek, met 'n stroomdigtheid van 2A1cm2. 'n Metode om "draervrye" I03Pd vanaf die Rh-skyfmateriaal te skei, is ook ontwikkel. Gebombardeerde pille van RhCh.3H20 is as skywe gebruik in die onaktiewe studies. AGI-X8 anioonuitruilerhars is vir hierdie skeidings gebruik en daar is gebruik gemaak van 'n metode wat oorspronklik ontwerp is vir die skeiding van Pd van Cu en Rh. Hierdie prosedure is net effens aangepas deur H202 te gebruik vir die oksidasie van Ru, alvorens dit op die hars gesorbeer is. Hierdie metode is ook suksesvol gebruik vir die isolering van Rh van radionukliede van Pd, Ru, Tc, Nb, Mo, Zr, ens, wat geproduseer is deur 400 MeV 160_ en 12C-geïnduseerde reaksies met Rh in RhCi).3H20 skywe. 5% ammoniakoplossing is gebruik om die Pd uit die hars te elueer, met 'n herwinning van 92%. Om die saadjies vir implantering te maak, is 103Pd op 'n matige basiese anioonuitruilerhars Amberlite IRA-93 gesorbeer deur 'n 103pd-oplossing, in 0.5 M Hel, deur 'n 0.5 ' lcm kolom te hersirkuleer vir 2 uur. 'n Tregter is ontwerp om die I03Pd-gelaaide harskorrels oor te dra na die titaanbuisies (0.7 mm binnedeursnit, 0.8 mm buitedeursnit en 4.5 mm lank). Om die buisies te verseël, is dekseltjies uit 'n 0.02 mm titaanplaat gesny. Verskeie dekseltjies is gemasjieneer om op die buisies vas te sweis. 'n Punt-sweismasjien is gebruik vir die sweiswerk nadat geringe, maar belangrike, aanpassings aan die masjien gedoen is.

This work is concentrated on the thermodynamic and kinetic aspects of water, alcohols, alkyl halides, ethers, and lactones bound and activated by the electrophilic [Cp'Ru(N0)] +2 and [Cp’Ru (NO)(CH3)] + centers (Cp' = cyclopentadienyl group). Counterions in these systems include OSO2CF3- (OTf-) and [(3, 5-(CF3)2C6H3)4B]- ([BAr4']-). The displacement of OTf- in Cp'Ru(N0) (0Tf)2 by H20 in dichloromethane is exothermic but entropically unfavorable due to the required reorganization of the solvent cage around released triflate ions. Thermodynamic parameters are also determined for OTf displacement by chloride and tetrahydrofuran (THF) using the 19F nuclear magnetic resonance (NMR) spectroscopy. The conversion of the [Cp’Ru (NO)(OH2)2] +2 to [Cp’Ru (NO)(μ-OH)} 2 +2 in aqueous solutions is characterized thermodynamically and kinetically by potentiometric and NMR methods. The results of the study of rhodium triflato complex trans- [Rh (CO)(PPh3)2(OTf)] show that OTf coordinates to the metal center in wet dichloromethane solutions, but the compound crystallizes as a water-coordinated triflate salt trans- [Rh (CO)(PPh3)2(OH2)] [OTf]. Thermodynamic parameters for alcohol (methanol, ethanol, isopropanol) binding to the Cp*Ru(N0) (0Tf)2 are determined from the 19F NMR spectroscopic data. The kinetics of the oxidation of alcohols to aldehydes or ketones via Ru (II) >>> Ru (0) redox process is studied by NMR methods. The results of the study support {3-hydrogen elimination mechanism, comprising one of the very few mechanistic investigations on reactions of this kind. Alkyl iodides are found to bind to the [Cp*Ru (NO)(CH3)] + fragment via displacement of a THF ligand in the presence of a BAr4 •-counterion, forming alkyl halide complexes that convert to [Cp’Ru (NO)(μ-I)]2+2. The mixed ruthenium-chromium complex [CpCr (NO)2(μ-I) (Ru (Cp’) (NOW is characterized as primarily a [Ru-I >> Cr] system as opposed to a [Ru << I-Cr] model. The complex [Cp*Ru (NO)(CH3) (THF)] is found to catalyze aerobic oxidation of THF to -y-butyrolactone. The new -y-butyrolactone ruthenium complex is isolated and characterized by X-ray methods in the solid state. The mechanism of catalytic oxidation is studied by 18O-labeled infrared spectroscopic methods. Radical decomposition of the intermediate hydroperoxy-tetrahydrofuran gives 1, 6-diol-diformate [CH(O)-(CH2)6-CH(O)]. The radical mechanism for the catalytic oxidation of THF is proposed.

Este trabalho de tese trata do estudo da interação de complexos dimetálicos contendo unidades do tipo [M2(µ-O2CCH3)4] (M = Ru, Rh ou Cu) com os ligantes 5-nitroimidazólicos (L): metronidazol, nimorazol, secnidazol e tinidazol. Novos compostos inéditos foram sintetizados e caracterizados principalmente por meio de análises elementares, técnicas espectroscópicas (espectroscopia eletrônica UV-VIS-IR, vibracional (FTIR, Raman,) e EPR, medidas magnéticas e termogravimetria (TGA). Os complexos de dirutênio, de fórmula [Ru2(µ-O2CCH3)4(L)2]PF6, apresentam bandas de absorção eletrônica em ~310 nm (IL), ~420 nm (π(RuO, Ru2) → π*(Ru2)) e ~1000 nm (δ(Ru2) → δ*(Ru2)), que são típicas de tetracarboxilatos de Ru2(II,III) que possuem dois centros metálicos unidos por ligação metal-metal múltipla de ordem 2,5. Os valores de µef (3,80 - 4,40 M.B.) indicam a configuração eletrônica σ2 π4 δ2 π*2 δ*1, em que há três elétrons desemparelhados para cada unidade Ru2. Os valores de Δv(CO2) = vas-vs (~50 cm-1), sendo vas(CO2) = 1443 - 1450 cm-1 e vs(CO2) = 1397 - 1409 cm-1, confirmam a coordenação dos carboxilatos em ponte. O deslocamento das bandas v(C=N) para maior frequência em comparação com os nitroimidazóis livres evidencia a coordenação desses ligantes ao rutênio por meio do N3 do anel. Bandas atribuídas aos estiramentos v(Ru-O) [IR, ~405 cm-1 (veu) e ~345 cm-1 (va2u)], v(Ru-N) [IR, 465 - 478 cm-1] e v(Ru-Ru) [Raman, ~326 - 334 cm-1] comprovam a formação das ligações envolvendo os íons rutênio. Os compostos são estáveis termicamente até ~200ºC, temperatura acima da qual começam a se decompor com a saída dos ligantes axiais, seguida de quebra do núcleo dimetálico. Todos os complexos comportam-se como eletrólitos 1:1 em solução, comprovando a presença do contra-íon PF6-. Os valores de potencial de meia-onda E1/2 (~0,25 V) são similares para todos os derivados contendo nitroimidazóis e são um pouco menores do que o do aquo-complexo [Ru2(µ-O2CCH3)4(H2O)2]PF6(0,31 V). Ensaios de partição em n-octanol-água indicam uma alta hidrofilicidade para os complexos. Os compostos de ródio, [Rh2(µ-O2CCH3)4(L)2], apresentam uma banda típica da transição π(Rh2) → σ*(Rh2) em ~555 nm (solução) e ~525 nm (estado sólido). O valor de µef igual a zero confirma que as espécies são diamagnéticas. Nestes casos os centros metálicos são unidos por ligação simples. Os valores de Δv (~110 cm-1) [vas(CO2), ~1590 cm-1; vs(CO2), 1423 - 1436 cm-1] confirmam a coordenação dos carboxilatos em ponte. A coordenação dos ligantes nitroimidazóis pelo N3 também é evidenciada pelo deslocamento das frequências v(C=N). Bandas atribuídas aos estiramentos v(Rh-O) [IR, ~385 cm-1 (veu) e ~340 cm-1 (va2u)], v(Rh-N) ) [IR, 475 - 490 cm-1] e v(Rh-Rh) [Raman, ~170 e 230 - 240 cm-1] comprovam a formação das ligações envolvendo os íons ródio. Estes compostos também se decompõem termicamente acima de 200ºC, mas neste caso a saída dos ligantes nitroimidazólicos ocorre juntamente com a quebra do núcleo dimetálico. Os complexos de cobre, [Cu2(µ-O2CCH3)4(L)2], apresentam uma banda em ~700 nm, denominada banda I, que é atribuída à transição dxz,yz →dx2-y2. A banda II característica de dímero foi observada em ~370 nm no espectro no estado sólido do complexo com metronidazol. Os valores de µef (1,40 - 1,55 M.B.) e dos parâmetros EPR [g// (2,160 - 2,180), g (2,010 - 2,050) e D (0,287 - 0,296 cm-1)] são característicos de estrutura dinuclear com carboxilatos em ponte e indicam a ocorrência de acoplamento antiferromagnético e existência de algum tipo de interação entre os centros metálicos. Os valores de Δv (~180 cm-1), [vas(CO2), 1619 - 1629 cm-1; vs(CO2), 1425 - 1433 cm-1] confirmam a coordenação dos carboxilatos em ponte. O deslocamento das bandas v(C=N) para maior frequência em relação aos nitroimidazóis evidencia a coordenação ao cobre também via N3 do anel. A banda v(Cu-O) é observada em ~350 cm-1. Estes compostos começam a se decompor também acima de 200ºC, no caso, com a saída de um dos ligantes nitroimidazólicos, sendo que a perda do segundo deve ocorrer justamente com a quebra do núcleo dimetálico. Os compostos são hidrofílicos. Todos os complexos de fórmula [M2(µ-O2CCH3)4(L)2]n (M = Ru, Rh, Cu; L = 5-nitroimidazol) investigados neste trabalho apresentam, portanto, estruturas constituídas por unidades diméricas. Dois núcleos metálicos são unidos por quatro ligantes acetato, em ponte equatorial, coordenados a eles pelos átomos de oxigênio, gerando um arcabouço do tipo gaiola. Os nitroimidazóis ocupam as posições axiais nestas unidades, coordenando-se aos íons metálicos pelo N3 do anel imidazólico. Como tetracarboxilatos diméricos, em geral, apresentam potencial na área de metalofármacos e os 5-nitroimidazóis pertencem a uma importante classe de fármacos de amplo uso clínico, ensaios foram realizados in vitro para verificar a possível atividade biológica dos novos complexos metálicos de rutênio e de cobre como: agentes antitumorais, radiossensibilizadores e agentes antimicrobianos (bactericida e fungicida). Os complexos de Ru2(II,III) apresentam maior atividade contra células cancerígenas (HeLa) do que contra células normais (NCTC-clone L929), enquanto que os complexos de Cu2(II,III), já em concentrações menores comparadas às dos análogos de Ru2(II,III), promovem a morte de células tumorais. Os complexos de cobre Cu2(II,II) exibem melhor atividade radiossensibilizadora no caso de baixas doses de radiação e 80% de sobrevivência celular. Os compostos são inativos contra bactérias aeróbicas, mas apresentam atividade no caso de bactérias anaeróbicas, sendo o complexo de cobre-metronidazol o mais eficaz. Este trabalho é o primeiro a relatar um estudo sobre atividade antifúngica para complexos de Ru2(II,III). Estes apresentam atividade contra fungos, embora em concentrações mais altas em comparação com alguns fármacos usuais. Os complexos de ródio não foram submetidos a estes ensaios devido à baixa solubilidade apresentada.
The interaction of dinuclear metal moieties [M2(µ-O2CCH3)4] (M = Ru, Rh or Cu) with 5-nitroimidazolic Iigands (L = metronidazole, nimorazole, secnidazole, tinidazole) were investigated. New compounds were synthesized and characterized by elemental analysis, spectroscopic (UV-VIS-NIR, FTIR, Raman, EPR) methods, magnetic measurements and thermogravimetry. Diruthenium complexes of general formula [Ru2(µ-O2CCH3)4(L)2]PF6 show absorption bands at ca, 310 nm (IL), 420 nm (π(RuO,Ru2) → π*(Ru2)) and 1000 nm (δ(Ru2) → δ*(Ru2)). These bands are typical of Ru2(II,III) tetracarboxylates where the metal centers are bonded by a metal-metal multiple bond of order 2.5. Values of µeff (3.80 - 4.40 MB) indicate an electronic configuration σ2 π4 δ2 π*2 δ*1, where three electrons are unpaired on each Ru2 unit. The differences Δv(CO2) = vas - vs (~ 50 cm-1), where vas(CO2) = 1443 - 1450 cm-1 and vs(CO2) = 1397 - 1409 cm-1, confirm the coordination through bridging carboxylates. The shifting of v(C=N) bands to higher energies compared to the free nitroimidazoles is an evidence of the coordination of these ligands through the N3 ring atoms. Bands that may be attributed to v (Ru-O) [IR, ~405 cm-1 (Veu) and ~345 cm-1 (Va2u)], v (Ru-N) [IR, 465 - 478 cm-1] and v(Ru-Ru) [Raman, ~ 326 - 334 cm-1] stretchings give evidence of the formation of bonds involving the ruthenium ions. The compounds are thermically stable up to ~200°C; above this temperature they start to decompose with loss of axial ligands followed by disruption of the dinuclear core. All complexes exhibit behavior of 1:1 electrolytes in solution, confirming the presence of the PF6- counter- ion. The values of half-wave potentials (E1/2, ~0,25 V) are similar for all the nitroimidazole derivatives but somewhat lower than that for the aqua-complex [Ru2(µ-O2CCH3)4(H2O)2]PF6 (0,31 V). Partition assays in n-octanol/water system show the high hydrophylicity of the compounds. The rhodium complexes [Rh2(µ-O2CCH3)4(L)2] exhibit a typical π(Rh2) → σ*(Rh2) transition at ~555 nm (solution) and ~525 nm (solid). The zero-values of µeff confirm that the species are diamagnetic. In this case the metal centers are linked by a single bond. The differences Δv (~ 110 cm-1), [Vas(CO2), ~1590 cm-1; vs(CO2), 1423 - 1436 cm-1], confirm the coordination through bridging carboxylates. Axial ligand coordination through the N3 nitroimidazole atom is also confirmed by the shifting of v (C=N) frequencies. Bands that may be attributed to v(Rh-O) [IR, ~385 cm-1 (Veu) and ~340 cm-1 (Va2u)], v(Rh-N) [IR, 475 - 490 cm-1] and v(Rh-Rh) [Raman, ~ 170 and 230 - 240 cm-1] stretchings agree with the formation of bonds involving the rhodium ions. These compounds also undergo decomposition above 200°C, but in this case the loss of nitroimidazole ligands occurs along with the disruption of the dimetal core. The copper complexes [Cu2(µ-O2CCH3)4(L)2] display the so-called Band I at ~700 nm, which is attributed to the dxz,yz → dx2-y2 transition. The characteristic dimmer band (Band II) was observed at ~370 nm for the metronidazole derivative in the solid state. The values of µeff (1.40 - 1.55 MB) and of EPR parameters (g//= 2.160 - 2.180; g = 2.010 - 2.050; D = 0.287 - 0.296) are in agreement with a carboxylate-bridged dinuclear structure and with antiferromagnetic coupling that indicates the presence of some type of interaction between the metal centers. The differences Δv (ca. 180 cm-1), [Vas(CO2), 1619 - 1629 cm-1; Vs(CO2), 1425 - 1433 cm-1], confirm the coordination through bridging carboxylates Axial ligand coordination through the N3 nitroimidazole atom is also confirmed by the shifting of v(C=N) frequencies. The band v(Cu-O) is observed at ~350 cm-1. These compounds also start to decompose above 200°C, initially with the loss of one of the nitroimidazole ligands, followed by loss of the second and disruption of the dimetal core, simultaneously. The compounds are hydrophilic. Therefore, all the studied complexes of general formula [M2(µ-O2CCH3)4(L)2] (M = Ru, Rh, Cu; L = 5-nitroimidazole) exhibit structures with dimeric units. Two metal centers are bonded by four equatorial bridging carboxylate ligands through oxygen atoms in a cage-like motif. Nitroimidazole molecules occupy the axial positions coordinating the metal through the N3 imidazole ring atom. Since dimeric tetracarboxylates are potential metal drugs and 5-nitromidazoles belong to an important class of broad clinicai spectrum, in vitro assays were performed to assess the antitumoral, radiosensitizer and antimicrobial (bactericide and fungicide) activities of the new ruthenium and copper complexes. The Ru2 (II,III) complexes are more active against tumor (HeLa) than normal (NCTC clone L929) cells, while the Cu2 (II,II) analogous promote tumor cell death at lower concentrations. Copper complexes also displayed the best radiosensitizer activity at low radiation doses and 80% of cell survival. The compounds are inactive against aerobic bacteria, but are active against the anaerobic, being the copper-metronidazole complex the most efficient. This is the first report of the antifungal activity of Ru2(II,III) complexes. They exhibit activity at concentrations somewhat higher than current used drugs. The rhodium complexes were not submitted to biological assays due to their low aqueous solubility.

The aim of this project was to synthesize and characterize new high nuclearity heterometallic Rh-Au clusters. The reactivity of rhodium clusters was studied starting from the precursor [Rh7(CO)16]3-, which was oxidated with different Au3+ and Au+ salts. Its behaviour was analysed in different reaction conditions, changing each time the Rh:Au stoichiometric ratio and solvents, under controlled CO atmosphere. Multiple new clusters were obtained: [Rh10Au(CO)26]3-, [Rh16Au6(CO)36]4-, [Rh19Au5(CO)40]4- and [Rh20Au7(CO)45]5-. A clean and reproducible synthetic pathway to synthesize the new [Rh10Au(CO)26]3- was discovered. Moreover, a new synthetic pathway to synthetize [Rh16Au6(CO)36]6- was discovered. Each compound has been characterized via FT-IR spectroscopy and single crystal X-ray diffractometry; [Rh10Au(CO)26]3-, [Rh16Au6(CO)36]4- and [Rh16Au6(CO)36]6- have been also analysed via ESI-MS analysis. Finally, chemical reactivity tests on [Rh10Au(CO)26]3- were conducted, verifying that a consecutive pathway starting from the latter leads to the formation of [Rh16Au6(CO)36]4-.

1. C–H Functionalisation of 2 Aryl Cyclic 1,3-Dicarbonyl Compounds Two enolate-directed C–H functionalisation protocols have been developed using 2-aryl cyclic 1,3-dicarbonyl compounds as substrates. Reactions with activated alkenes, under ruthenium or palladium catalysis produced benzopyrans in most cases, in moderate to good yield. Alternatively, an oxidative annulation of 2-aryl cyclic 1.3-dicarbonyls with 1,3-enynes was facilitated under rhodium catalysis, forming functionalised spiroindene structures in most cases, in generally good yields and high regioselectivity. During the investigation, the serendipitous formation of spirodialin structures was also observed. 2. Enantioselective Rh(I)-Catalysed Cyclisation of Arylboron Compounds onto Ketones Chiral tertiary alcohols, bearing aza-, oxa- and carbocyclic core structures of varying ring size were successfully formed from arylboron substrates under rhodium catalysis. In general the reactions proceeded with good yield and with moderate to high enantioselectivity. A protocol for the formation of a bicyclic lactam system was also achieved in moderate yield and enantioselectivity.

Abstract. In this thesis the synthesis of potentially biologically active heterocyclic compounds has been developed through novel catalytic methods involving C-N and C-O bond forming processes. The thesis consists of three main chapters: a) oxidative intramolecular palladium(II)-difunctionalizations of alkenes (Chapter 1); b) iodine species as a powerful tool in oxidative ring closing reaction (Chapter 2); c) intramolecular rhodium(I) allylic addition to afford α-vinyl-substituted heterocycles (Chapter 3). In Chapter 1.1 an aminoarylation process of allylic ureas has been investigated as a tool to construct 4-substituted imidazolidinones. In the presence of aryltin nucleophiles and hydrogen peroxide as an inexpensive and green oxidant, a 5-exo-regioselective procedure has been developed. On the other hand, when the homoallylic urea is used under similar conditions the seven-membered ring is obtained as a consequence of the β-elimination accountable to a Pd(II)/Pd(0) catalytic cycle. In Chapter 1.2 an intramolecular alkoxyacylation is described employing an hypervalent iodine (III) as both the acylating and oxidizing reagent. A regioselective 6-exo-trig Pd(II)-catalysed cyclisation of N-allyl aminophenol and N-allyl aminoethanol affords benzoxazine and morpholine nuclei, respectively. The synthetic utility of this new products is demonstrated through two-step transformations into purine derivatives, which are used for the treatment and prevention of cancer, and into β-aminoacids. In Chapter 2.1 it is reported the development of an intramolecular domino-type Diels Alder reaction initiated by hypervalent iodine reagents. The employment of N-allyl 2-aminophenols as substrates leads to the formation of a tricyclic system in the sole presence of I(III) species. Moreover, the insertion of various nucleophiles on the α-position of the amino group opens up the way to further unexplored functionalizations. The substrate scope is investigated varying both substituents on the aromatic ring, protective groups and nucleophiles, affording the respective products in 23-67% yields. In Chapter 2.2 a metal-free aminoiodination of O-allyl Ts-protected carbamates is described. Thus, by using hydrogen peroxide and potassium iodide in aqueous media, iodomethyl-substituted heterocycles are obtained in good yields and for selected substrates in a diastereoselective way, too. The reaction proceeds through the formation of an iodonium intermediate with the subsequent attack of the nitrogen in anti. In Chapter 3.1 an intramolecular hydroamination of Ts-protected allenyl amines is investigated. The ability of Rh(I) to catalyse a hydroamination process in a complete selective way, mostly modulating the type of ligand employed, is herein shown. Vinyl-substituted benzoxazine and benzoxazepine have been obtained in good yields and excellent enantioselectivity, as it has never been done before, by employing Josiphos J688-1 ligand and PPTS as co-catalyst. In Chapter 3.2 the results regarding the intramolecular hydroalkoxylation of allenyl alcohols are reported. N-allenyl aminoethanol, N-allenyl aminophenol, allenyl alcohols and allenyl phenols are subjects of our research. Despite the substrate diversity, the chiral ferrocelane diphosphine ligand, (R,R) Me-ferrocelane, is proven optimal for the intramolecular OH-addition to allenes. High yields and good enantioselectivity can be reached varying the Brønsted acid, employed as additive in the reaction. In conclusion, oxidative palladium(II)-catalysed alkene difunctionalizations, hypervalent iodine-promoted dearomatizing intramolecular Diels-Alder reaction, oxidative aminoiodinations and intramolecular enantioselective rhodium(I)-catalysed hydroaminations and alkoxylations of allenes are approaches described in this thesis as valuable methods for the construction of medicinally relevant heterocycles.

The properties of transition metal clusters differ from those of both atomic and bulk size regimes. Such clusters are incompletely understood and potentially useful, making them attractive targets for further study. The very smallest clusters studied in this thesis (CuO, Cu₂ and Cu₃) have been investigated with velocity map imaging. 1+1' photodissociation of CuO X ²Π_3/2 was observed, via the C, D, E, F and H states of CuO. CuO* was photodissociated to form Cu(²D_3/2) + O(¹D₂). D₀(CuO) was determined to be 3.041±0.030 cm^-1. Non-resonant three-photon Cu₂ photodissociation occurred throughout the energy range studied to produce one ground-state and one highly-excited copper atom,Cu*. Cu* was ionised by a single additional visible photon. Nearly all Cu* atoms with internal energies between 41000 and 53000 cm^-1 were observed. D₀(Cu₂) has been calculated to be 1.992±0.037 eV. Features arising from photodissociation of Cu₃ were observed in the Cu⁺ and Cu₂⁺ ion yield spectra and images. Their structure was ill-resolved due to uncertainties in the internal energy of both parent Cu₃ and product Cu₂. These features correspond to single-photon dissociation of Cu₃ to produce metastable D-states of the copper atom and vibrationally excited Cu₂. One series of features implies a previously-unobserved state of either Cu₂ or Cu₃. Rh_nN₂O⁺ and Rh_nON₂O⁺ (n=5, 6) were collisionally activated in collision-induced dissociation (CID) experiments with Ar and ¹³CO. These experiments were carried out in a Fourier Transform Ion Cyclotron Resonance(FT-ICR)spectrometer. Argon collisions induced both N₂O desorption and N₂O reduction. The branching ratios observed reproduced those seen in prior IR-MPD experiments. ¹³CO was observed to chemisorb to the cluster upon collision, activating not only N₂O desorption and reduction but also CO oxidation. Formation of CO2 was noted to be particularly rapid on the n=5 cluster compared to the n=6 cluster. Reactions of Rh_nN₂O⁺ (n=4-6) clusters were also activated by black body radiation. This technique is known as BIRD - black-body induced infrared radiative dissociation. These studies revealed that the N₂O desorption barrier exceeds the N₂O reduction barrier on all clusters studied, but that the entropic favourability of desorption increases its rate relative to reduction with increasing cluster internal energy. The BIRD rate was much reduced upon cooling the ICR cell to 100 K. A further test of the BIRD mechanism increased the number of N₂O ligands and hence the absorption rate. An approximately linear increase in the dissociation rate of Rh_n(N₂O)_m⁺ was observed with index m. Deviations from linearity were caused by variations in the N₂O desorption rate. In the case of Rh₅(N₂O)_m⁺, desorption rates corresponded closely to N₂O binding energies calculated by density functional theory. The system was modelled using a master equation approach.

LaNi5 (structure type CaCu5) est l'un des composés intermétalliques les plus étudiés pour le stockage de l'hydrogène. Les propriétés d'hydrogénation peuvent être modifiées en substituant le nickel ou le lanthane par d'autres éléments. Un modèle géométrique empirique relie la stabilité de l'hydrure au volume du composé intermétallique ternaire : plus le volume est grand, plus l'hydrure est stable. La substitution par le platine contredit pourtant ce modèle. Nous étudions les effets de la substitution du nickel par des éléments 4d et5d, voisins du platine (M=Ru, Rh, Pd, Ag, Re, Os, Ir, Au) afin de déterminer l'origine de l'anomalie constatée. Nous avons synthétisé et caractérisé plusieurs composés LaNi5−xMx afin de déterminer la limite de solubilité de l'élément M dans la phase type CaCu5, ainsi que la nature des phases avoisinantes dans les diagrammes de phases ternaires. Ces éléments modifient fortement les propriétés d'hydrogénation. Comme dans le cas du platine, les substituants étudiés contredisent le modèle géométrique. Afin d'apporter des éléments de réponse à ces anomalies, le système LaNi5−xPdx-D2 est étudié par diffraction de neutrons in situ, ce qui permet la détermination du diagramme de phases LaNi5−xPdx-D2. Les structures cristallographiques des hydrures sont caractérisées : une mise en ordre des atomes métalliques et/ou de deutérium conduit à la formation de différentes surstructures. L'origine de l'anomalie est également recherchée à travers la structure électronique des composés et de leurs hydrures. Une étude théorique par calculs ab initio est ainsi menée en accord avec les résultats expérimentaux. La déstabilisation des hydrures s'explique par la forte stabilisation du composé intermétallique ternaire.

Radiossensibilizadores são definidos como agentes químicos que aumentam a sensibilidade das células hipóxicas à radiação, visando o aumento da eficácia da radioterapia no tratamento do câncer. Alguns Carboxilatos de Rh (II) e compostos nitroimidazólicos têm sido testados como radiossensibilizadores em doses elevadas de radiação, obtendo-se resultados significativos. Neste trabalho, foram sintetizados vários carboxilatos e um amidato de Rh (II): propionato, butirato, trifluoroacetato, citrato e trifluoroacetamidato, assim como os seus respectivos adutos com metronidazol, de fórmula geral: [Rh2(RCOO)4metro2] (R = CH3, C2H5, C3H7, C5 H7O5, e CF3) para o caso dos carboxilatos e [Rh2(CF3CONH) 4 metro2] para o aduto de trifluoroacetamidato. Os compostos foram caracterizados por análise elementar, espectroscopia eletrônica, infravermelho e de ressonância magnética nuclear de próton. O resultado desta caracterização permitiu estabelecer as rotas de síntese confirmando a formação dos carboxilatos tipo ponte e a presença do metronidazol nas posições axiais, numa relação 1:2. O efeito radiossensibilizador desses complexos de Rh (II) foi testado in vitro, irradiando-se, em atmosfera hipóxica, células de ovário de hamster chinês (CHO k1), na presença dos complexos, utilizando-se raios gama provenientes de uma fonte de 60Co, com doses de 2,7 e 4,3 Gy. Foi realizado teste de citotoxicidade para determinar as concentrações atóxicas de cada composto, eliminando a possibilidade de morte celular devido ao efeito tóxico dos mesmos. Na dose 2,7 Gy não houve nenhum efeito interessante; já com a dose de 4,3 Gy o [Rh2(CH3 COO)4] mostrou uma atividade radiossensibilizadora maior do que nos demais complexos. Os resultados foram semelhantes aos obtidos na literatura com doses de radiação até 10 vezes maiores. Devido à ausência de mudanças significativas no efeito radiossensibilizador entre os carboxilatos e amidato e seus respectivos adutos com metronidazol, foi determinada a constante de formação destes últimos, demonstrando que os mesmos sofrem decomposição quando em solução aquosa diluída.
Radiosensitizers are chemical agents that enhance the radiation sensitivity of hipoxic tumor cells aiming to better radiotherapy efficacy in the treatment of cancer. Some Rhodium (II) carboxylates and its adducts with nitroimidazole derivatives, have been tested as radiosensitizers in high doses of radiation, being obtained significant results. In this work, several Rhodium carboxylates and one Rhodium amidate previously described were synthesized: propionate, trifluoroacetate, citrate and , trifluoroacetamidate, as well as their respective adducts with nitroimidazole of general formula [Rh2(RCOO)4metro2] for the carboxylates and [Rh2(CF3CONH)4metro2] for the trifluoroacetamidate adduct. The compositions where characterized by elementary analysis, electronic and infrared spectroscopy and proton nuclear magnetic resonance. The results of that characterization allowed us to establish the synthesis routes and confirm the bridge type structure of the Rodhium compounds, beyond the presence of the metronidazole at the axial positions in the proportions of 1:2. The radiosensitizing effects of these Rh (II) complexes were tested in vitro by irradiation of Chinese hamster (CHO k1) cells under hipoxic atmosphere in the presence of the complexes, using gamma rays from a 60Co source and doses of 2,7 and 4,3 Gy. A cytotoxicity test has been performed to determinate the non-toxic concentrations of these compounds, in order to rule out the possibility of cellular death induced by the complexe´s cytotoxicity. A 2,7 Gy dose showed no interesting effects but under a 4,3 Gy dose, the complex Rh2(CH3 COO)4 showed a higher radiosensitizing effect than the order compounds and close to previously reported effects which required high radiation doses. As there was not a significant change in the radiosensitizing effect between the carboxylate and the amidate and their respective metronidazole adducts it was performed the measurement of the formation constant of that adducts. The results of that measurements gave evidence of adduct decomposition when in dilute aqueous solution.

L'étude des systèmes uranium-cobalt ou rhodium-étain a permis de mettre en evidence les nouveaux stannures ternaires: UCo1,45Sn2, U3Rh4Sn13, UM2Sn et U2M2Sn (M=Co, Rh). Certains d'entre eux ont des propriétés physiques intéressantes comme UCo1,45Sn2 qui présente une transition métamagnétique induite par des faibles champs ou U3Rh4Sn13 qui est considère comme un "fermions lourds" magnétiquement ordonne. D'autre part, l'étude de la nouvelle famille U2M2Sn montre que le comportement magnétique de l'uranium dans ces stannures est fortement influence par la nature de l'élement de transition M présent. Ceci a été expliqué par la force de l'hybridation 5f (U)-nd (M) qui dépend en particulier du nombre d'électrons d de l'élement M.

In this thesis, graphene (i.e. monolayer carbon film) and carbon clusters supported on a transition metal surface are systematically studied by local probe techniques, with respect to their structures, electronic properties and formation mechanisms. The main tools used are low-temperature scanning tunnelling microscopy and spectroscopy (STM and STS), which are introduced in Chapter 2. The mechanism of the resonance tunnelling at electron energies higher than the work function of the surface is discussed in detail, and a qualitative explanation of the Gundlach oscillations in the corresponding spectroscopy is presented. Epitaxial graphene synthesised on the Rh(111) surface by ethylene dehydrogenation is investigated by STM in Chapter 4. Such carbon film exhibits a hexagonal Moiré pattern due to a lattice mismatch between graphene and the rhodium substrate. The periodicity and local registries of the graphene/Rh(111) superstructure are carefully analysed. Based on a thorough discussion about the “commensurate vs. incommensurate” nature of the Moiré pattern in surface science field, the graphene/Rh(111) system is identified to have a non-simple-commensurate superstructure. The surface electronic properties and geometric buckling of graphene/Rh(111) are investigated by resonance tunnelling spectroscopy (RTS) and density functional theory (DFT) calculations in Chapter 5. Spectroscopy measurements reveal a modulation of the electronic surface potential (or work function Φ) across the supercell of epitaxial graphene. Based on the microscopy/spectroscopy data and the extended DFT calculations, we examined the electronic coupling of the various local C-Rh registries, and identified both experimentally and theoretically the local atomic configurations of maximum and minimum chemical bonding between graphene and the rhodium substrate. We studied in Chapter 6 the growth mechanism of graphene on Rh(111) at elevated temperatures. This part starts by investigating the dehydrogenation of ethylene into ethylidyne. When the dehydrogenation process is complete, monodispersed carbon species, identified as 7C6, are found to dominate the cluster population on the rhodium terraces. A significant coalescence of the 7C6 clusters into graphene islands occurs at temperatures higher than 873 K. The structural and electronic properties of the 7C6 carbon clusters are examined by high-resolution STM and STS, and compared with coronene molecules, i.e. the hydrogenated analogues of 7C6. DFT calculations are further used to explain the stability of 7C6 supported on the Rh(111) surface, and also the structural characteristics of such magic-sized carbon clusters.

In this thesis the oxidation of monoterpenes by O3 and NO2 and factors that influenced the oxidation were studied. In the environment both ozone (O3) and nitrogen dioxide (NO2) are present as oxidising gases, which causes sampling artefacts when using Tenax TA as an adsorbent to sample organic compounds in the air. A scrubber was developed to remove O3 and NO2 prior to the sampling tube, and artefacts during sampling were minimised when using the scrubber. The main organic compounds sampled in this thesis were two monoterpenes, alfa-pinene and delta-3-carene, due to their presence in both indoor and outdoor air. The recovery of the monoterpenes through the scrubber varied between 75-97% at relative humidities of 15-75%.

The reactions of alfa-pinene and delta-3-carene with O 3, NO2 and nitric oxide (NO) at different relative humidities (RHs) and reaction times were studied in a dark reaction chamber. The experiments were planned and performed according to an experimental design were the factors influencing the reaction (O3, NO2, NO, RH and reaction times) were varied between high and low levels. In the experiments up to 13% of the monoterpenes reacted when O3, NO2, and reaction time were at high levels, and NO, and RH were at low levels. In the evaluation eight and seven factors (including both single and interaction factors) were found to influence the amount of alfa-pinene and delta-3-carene reacted, respectively. The three most influencing factors for both of the monoterpenes were the O 3 level, the reaction time, and the RH. Increased O3 level and reaction time increased the amount of monoterpene reacted, and increased RH decreased the amount reacted.

A theoretical model of the reactions occurring in the reaction chamber was created. The amount of monoterpene reacted at different initial settings of O3, NO2, and NO were calculated, as well as the influence of different reaction pathways, and the concentrations of O3 and NO2, and NO at specific reaction times. The results of the theoretical model were that the reactivity of the gas mixture towards alfa-pinene and delta-3-carene was underestimated. But, the calculated concentrations of O3, NO2, and NO in the theoretical model were found to correspond to a high degree with experimental results performed under similar conditions. The possible associations between organic compounds in indoor air, building variables and the presence of sick building syndrome were studied using principal component analysis. The most complex model was able to separate 71% of the “sick” buildings from the “healthy” buildings. The most important variables that separated the “sick” buildings from the “healthy” buildings were a more frequent occurrence or a higher concentration of compounds with shorter retention times in the “sick” buildings.

The outcome of this thesis could be summarised as follows;

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Nitrogen-containing compounds are essential structural units in a myriad of biologically active molecules including pharmaceuticals. Although numerous synthetic methods have been developed over the last few decades, new methods constructing them in an efficient way from readily accessible starting material are still great of interest. As a coupling partner of the reaction, alkenes are abundant, general, and therefore ideal starting materials to synthesize a variety of complex, value-added products. In this thesis, we have utilized Rh(III) catalysis to develop efficient synthetic methodologies for nitrogen-containing compounds using alkenes as coupling partners. In Chapter 2, we developed a unique disconnection approach to pyrrolidines using a-olefins as a 4-carbon source and hydroxylamine derivatives as a nitrogen source of the reaction. In Chapter 3, regio- and diastereoselective synthesis of a,b-unsaturated-d-lactams from acrylamide and unactivated alkenes initiated from C-H activation are discussed. In Chapters 4 and 5, three-component alkene difunctionalization of alkenes delivering acyclic aminated products including a-amino acids are described.

The Rh-catalyzed conjugate addition of TMS-acetylene to alkylidene Meldrum’s acids was developed. Exceptional ee’s and yields were attained using chiral 3,5-Xylyl-BIPHEP ligand. The scope of the reaction was also shown to be very broad with functionalities including phenol, silyl ether, and boronates being tolerated. The successful deprotection and subsequent Sonogashira coupling reaction of the terminal alkyne was also developed.

This work is aimed at elucidating the structures and spectroscopic properties of phosphine and b phosphonite complexes of Mn(III), Co(III) and Rh(III) porphyrins, a class of coordination compounds that has been little reported on in the literature to date. In this work, a range of novel bis(phosphine) and bis(phosphonite) complexes of the three aforementioned metals have been synthesized, crystalized and analysed by means of X-ray structure determination, 1H NMR, 13C NMR, 31P NMR as well as electronic and IR spectroscopy. [Mn(TPP)(PPh3)2](SbF6) crystallizes in the monoclinic space group P21/c and displays an extraordinarily long Mn-P bond length of 3.088(2) A. Moderate ruffling of the porphyrin ligand is observed. This complex is paramagnetic with fast proton relaxation times, and thus did not yield any useful 1H NMR data. In an attempt to crystallize [Mn(TPP){P(OPh)3}2](SbF6), a complex bearing an O-donor contamination product, [Mn(TPP){(O)PH(OPh)2} ](SbF6), was isolated and its solid state structure determined by X-ray diffraction methods. The structure of this complex has been included in this work as it displays interesting structural features and is the very first phosphonate complex of a metalloporphyrin. This compound crystallizes in the monoclinic space group P21/n and shows a significantly saddled conformation. The axial Mn-O bond length measures 2.122(3) A. The Mn-Nporph bond lengths are 1.998(6) and 2.002(3) A for the bis(phosphine) and phosphonate complexes, respectively. Since the diethyl phosphonate complex was an unintended reaction product, no further characterisation of it was undertaken. [Co(TPP)(depp)2](SbF6), where depp = diethylphenylphosphine, crystallizes in the monoclinic space group P21/c. This complex displays inversion symmetry at the metal center and the porphyrin core is effectively planar. However, [Co(TPP)(edpp)2](SbF6), where edpp = ethyldiphenylphosphine, crystallizes in the· monoclinic space group P21/n and shows a significantly ruffled conformation of the porphyrin core and displays no inversion symmetry. [Co(TPP)(deppt)2](SbF6), where deppt = diethylphenylphosphonite, also crystallizes in the monoclinic space group P21/n, but displays inversion symmetry through the central cobalt ion. As a result, this complex does not display any significant conformational deviations of the porphyrin core from planarity. The axial Co-P bond lengths are significantly shorter than that of . the equivalentbond in the manganese bis(triphenylphosphine) complex at 2.312(1) A, 2.323(10) A and 2.258(2) A for [Co(TPP)(depp)2](SbF6), [Co(TPP)(edpp)2](SbF6) and [Co(TPP)(deppt)2](SbF6), respectively. The Co-Nporph bond lengths average to 1.980(3) A, 1.972(7) A and 1.980(4) A for these three complexes, respectively. I03Rh NMR measurements of three rhodium bis(phosphine)/bis(phosphonite) porphyrins have been performed by the indirect probing of the rhodium metal center by means of the phosphorus nucleus of the coordinated axial ligand. The resulting I03Rh NMR shifts for [Rh(TPP)(edpp)2](SbF6), [Rh(TPP)(edppt)2](SbF6), where edppt = ethyldiphenylphosphonite, and [Rh(TPP)(deppt)2](SbF6) are 2558, 2413 and 2365 ppm, respectively. [Rh(TPP)(edpP)2](SbF6) crystallizes in the monoclinic space group P21/n and shows moderate ruffling of the porphyrin core. The axial Rh-P bond length is 2.401(2) A. [Rh(TPP)(edppt)2](SbF6) and [Rh(TPP)(deppt)2](SbF6) both crystallize in the monoclinic space group P21/c. The porphyrin core of [Rh(TPP)(edppt)2](SbF6) displays a moderate degree of ruffling, as observed in [Rh(TPP)(edpp)2](SbF6), yet the axial Rh-P bond length is substantially shorter at 2.361(9) A. [Rh(TPP)(deppt)2](SbF6) exhibits the shortest Rh-P bond length of the three complexes at 2.332(2) A. The porphyrin core is mostly planar. The Rh-Nporph distances average 2.034(1) A for the S4-ruffled complexes and 2.044(3) A for the planar complex, the shorter distance in the ruffled derivatives being consistent with a distortion-induced compression of the Rh(III) ion.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003

At the threshold of the 21st centry, a new set of challenges is defined by the need to develop sustainable means of preparing chemical commodities demanded by society. Hence, such concepts as atom economy, step economy, and 'green chemistry' have become the requirements for the development of synthetic reactions. Hydrogenation is one of the most powerful catalytic methods which successfully satisfy the stated requirements of modern chemistry. Accordingly, catalytic hydrogenation has been tremendously utilized in industrial settings. The profound impact of hydrogenation portended a powerful approach to reductive carbon-carbon bond formation under hydrogenation conditions, resulting in the discovery of the Fischer-Tropsch process and hydroformylation. However, since this discovery, processes have restricted to the incorporation of a single carbon monoxide unit. Even though there are a few seminal contributions, systematic efforts toward the development of hydrogen-mediated carboncarbon bond forming processes beyond hydroformylation have been absent from the literature. In an exciting advance, the Krische group has shown that it is possible to reductively couple two or more organic molecules simply through their exposure to gaseous hydrogen in the presence of a metal catalyst. This finding has led to the development of a broad, new family of hydrogen-mediated C-C bond formation. Herein, related to hydrogen-mediated C-C bond formation, the overview of metal catalyzed intermolecular reductive coupling in the presence of reducing agents such as borane, silane, alane, metal, and hydrogen is presented. Chapter 2 describes systematic approaches to the development of hydrogen-mediated C-C bond formation and successful preliminary results achieved by our research group. Chapters 3 and 4 will describe the further extension of these hydrogen-mediated C-C bond formations including (1) hydrogen-mediated reductive couplings of conjugated alkynes with iminoacetates, (2) hydrogen-mediated reductive couplings of 1,3-enynes with [alpha]-ketoesters, and (3) hydrogen-mediated multicomponent reductive couplings. The development of catalytic systems for the nucleophilic activation of enones using phosphine catalysts has received attractive attention. Recently, an intramolecular variant of the Rauhut-Currier reaction was developed in our lab. To further extend nucleophilic phosphine catalysis, we have sought to develop new catalytic methodology via phosphine conjugate addition. Chapter 5 describes two new methodologies related to their area: (1) catalytic cycloallylation via nucleophilic phosphine catalysis and (2) allylic amination of Morita-Baylis-Hillman acetates.
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Les composés aminés représentent une grande part des substances actives en chimie médicinale. Les travaux rapportés dans cette thèse décrivent les efforts consacrés au développement d’une nouvelle méthode d’amination de liens C-H propargyliques. Notre groupe de recherche a développé depuis quelques années un nouveau précurseur de nitrène métallique, les N-mésyloxycarbamates, permettant d’effectuer des réactions d’amination de liaisons C-H diversement activées. Au cours du développement de notre méthodologie, la synthèse du N-mésyloxycarbamate a fait l’objet de nombreuses optimisations, notamment en améliorant l’échelle globale de la synthèse ainsi que son efficacité. De même, des efforts ont été consacrés pour diminuer le nombre d’étapes nécessaires à la synthèse du réactif en développant la synthèse d’un des intermédiaires de manière énantiosélective. Enfin, la synthèse de ce réactif a également été envisagée à l’aide de la chimie en flux continu. Au cours du développement de la méthode de synthèse d’amines propargyliques, nous avons constaté que l’acide acétique jouait un rôle déterminant dans la conservation de bonnes sélectivités et réactivités de la réaction. Ces différentes observations ont permis de mettre au point un procédé diastéréosélectif efficace permettant d’obtenir des amines propargyliques avec des rendements allant de moyens à bons et avec d’excellentes diastéréosélectivités. A la suite de l’étude de l’étendue de notre procédé, nous avons tenté de déterminer les mécanismes réactionnels qui régissaient la réactivité et la sélectivité de celui-ci. Nous avons ainsi montré que l’espèce réactive du système catalytique était bel et bien un nitrène métallique, et que l’étape cinétiquement déterminante était celle d’insertion. Des expériences faites en oxydant l’espèce catalytique de rhodium ont suggéré que plusieurs états d’oxydation de cette espèce peuvent être présents et actifs dans le système catalytique.
The nitrogen containing compounds represent a large portion of the active substances in medicinal chemistry. The work reported in this manuscript describe the efforts devoted to the development of a new method of amination of propargylic C-H bonds. Our research group has developed recently a new metal nitrene precursor, N-mesyloxycarbamates, to perform amination reactions on various C-H bonds. During the development of our methodology, the synthesis of N-mesyloxycarbamate has undergone many improvements, including improved global scale synthesis and effectiveness. Similarly, efforts were devoted to reduce the number of steps required for the synthesis of the reagent by developing the synthesis of an intermediate enantioselectively. Finally, the synthesis of this reagent was also considered using continuous flow chemistry. During development of the method of synthesis of propargylic amines, we have found that acetic acid plays a key role in the conservation of good selectivity and reactivity of the reaction. These observations allowed to develop an efficient diastereoselective process in order to obtain propargylic amines with moderate to good yields and with excellent diastereoselectivities. Following the study of the scope of our process, we tried to determine the reaction mechanisms governing the reactivity and selectivity. We have shown that the reactive species of the catalyst system was indeed a metal nitrene, and that the rate-determining step was the insertion. Experiments made by oxidizing the rhodium catalytic species suggested that several oxidation states of this species may be present and active in the catalytic system.

Les dérivés cyclopropaniques di-accepteurs représentent des intermédiaires synthétiques précieux dans l’élaboration de structures moléculaires complexes, ayant des applications dans plusieurs domaines de la chimie. Au cours de cet ouvrage, nous nous sommes intéressés à la synthèse de ces unités sous forme énantioenrichie en utilisant la cyclopropanation d’alcènes par catalyse avec des complexes de Rh(II) utilisant des composés diazoïques di-accepteurs comme substrats. Suite au développement initial d’une méthode de cyclopropanation d’alcènes catalytique asymétrique utilisant des nitro diazocétones, de multiples études expérimentales quant au mécanisme de stéréoinduction dans ce type de réaction ont été effectuées. Nous avons alors pu identifier le groupement p-méthoxyphénylcétone du substrat et le catalyseur Rh2(S-TCPTTL)4 comme étant une combinaison clé pour l’atteinte de diastéréosélectivités et d’excès énantiomères élevés. Ceci a mené au développement de deux autres méthodes de cyclopropanation stéréosélectives distinctes, utilisant soit une cyano diazocétone ou un céto diazoester. Nous avons démontré l’utilité des dérivés cyclopropaniques énantioenrichis obtenus par ces trois méthodes dans une panoplie de manipulations synthétiques, dont l’addition nucléophile d’amines et de cuprates, la cycloaddition formelle avec un aldéhyde, et la synthèse de dérivés cyclopropaniques importants en chimie médicinale. Une étude structurelle approfondie des complexes de Rh(II) chiraux nous a permis de déterminer les facteurs responsables de leur pouvoir d’énantioinduction dans notre système réactionnel, ce qui a d’énormes implications dans d’autres méthodologies utilisant ces mêmes catalyseurs. Le dévoilement d’une conformation inattendue dite ‘All-up’, ainsi que de la présence d’interactions stabilisantes régissant la rigidité de cet arrangement se sont avérés cruciaux dans notre compréhension du mécanisme. Dans le cadre de cette investigation, nous avons développé une méthode générale pour la synthèse de complexes de Rh(II) hétéroleptiques, multipliant ainsi le nombre de catalyseurs accessibles dans l’élaboration éventuelle de nouvelles réactions stéréosélectives, et nous permettant d’effectuer une étude structurelle plus détaillée. De plus, nous avons développé une méthode particulièrement efficace pour la synthèse d’un autre type de dérivé cyclopropanique di-accepteur par catalyse avec des complexes de Rh(II), les cyano-cyclopropylphosphonates. Les produits de cette transformation sont obtenus avec des énantiosélectivités élevées, et sont des substrats intéressants pour des réactions tandem d’ouverture de cycle par addition nucléophile / oléfination de composés carbonylés. De plus, ces composés sont des précurseurs de molécules utiles en chimie médicinale tels que les acides aminocyclopropylphosphoniques.
Di-acceptor cyclopropane derivatives are valuable synthetic intermediates in the preparation of complex molecular structures, with applications in several fields of chemistry. During this work, we investigated the synthesis of these units in enantioenriched form via the Rh(II)-catalyzed cyclopropanation of alkenes using di-acceptor diazo compounds as substrates. Following the initial development of a method for the catalytic asymmetric cyclopropanation of alkenes using nitro diazoketones, many experimental studies on the mechanism of stereoinduction in this reaction were performed. We were able to identify the p-methoxyphenylketone group of the substrate and catalyst Rh2(S-TCPTTL)4 as a key combination for the obtention of high diastereoselectivities and enantiomeric excesses. This led to the development of two distinct stereoselective cyclopropanation methods, using either an cyano diazoketone or a keto diazoester. We demonstrated the utility of the enantioenriched cyclopropane derivatives obtained by these three methods in a variety of synthetic manipulations, including the nucleophilic addition of amines and cuprates, the formal cycloaddition with an aldehyde, and the synthesis of biologically relevant cyclopropane derivatives. A thorough structural study of chiral Rh(II) complexes allowed us to determine the factors responsible for their enantioinduction ability in our reaction system, which has enormous implications in other metal-carbene reactions using these catalysts. The unveiling of an unexpected conformation called 'All-up', and the presence of stabilizing interactions controlling the rigidity of this arrangement have been crucial in our understanding of the mechanism. As part of this investigation, we developed a general method for the synthesis of heteroleptic Rh(II) complexes, thus multiplying the number of catalysts available in the development of new stereoselective reactions, and allowing us to conduct a more detailed structural study. Moreover, we have developed a particularly efficient method for the synthesis of another type of di-acceptor cyclopropane derivative via Rh(II) catalysis, cyanocyclopropylphosphonates. The highly enantioenriched products obtained in this transformation are interesting substrates for tandem reactions of nucleophilic addition / olefination of carbonyl compounds, and are precursors of useful molecules in medicinal chemistry, such as aminocyclopropylphosphonic acids.

Les sulfilimines et les sulfoximines sont des motifs structuraux dont l’intérêt synthétique est grandissant, notamment du fait de leurs applications en chimie médicinale et en agrochimie. Les travaux rapportés dans cet ouvrage décrivent le développement de nouvelles méthodes de synthèse efficaces pour la production de ces unités atypiques. Ces méthodes sont basées sur la réactivité d’une source d’azote électrophile, vis-à-vis de thioéthers et de sulfoxydes. L’utilisation d’un complexe métallique introduit en quantité catalytique a permis de favoriser le processus réactionnel. En tirant bénéfice de l’expertise de notre groupe de recherche sur le développement de réactions d’amination stéréosélectives de liaisons C-H et d’aziridination de styrènes, nous avons d’abord étudié la réactivité des N-mésyloxycarbamates comme source d’azote électrophile. Après avoir optimisé sa synthèse sur grande échelle, ce réactif chiral a été utilisé dans des réactions d’amination de thioéthers et de sulfoxydes, catalysées par un dimère de rhodium (II) chiral. Un processus diastéréosélectif efficace a été mis au point, permettant de produire des sulfilimines et des sulfoximines chirales avec d’excellents rendements et sélectivités. Au cours de l’optimisation de cette méthode de synthèse, nous avons pu constater l’effet déterminant de certains additifs sur la réactivité et la sélectivité de la réaction. Une étude mécanistique a été entreprise afin de comprendre leur mode d’action. Il a été observé qu’une base de Lewis telle que le 4-diméthylaminopyridine (DMAP) pouvait se coordiner au dimère de rhodium(II) et modifier ses propriétés structurales et redox. Les résultats que nous avons obtenus suggèrent que l’espèce catalytique active est un dimère de rhodium de valence mixte Rh(II)/Rh(III). Nous avons également découvert que l’incorporation de sels de bispyridinium avait une influence cruciale sur la diastéréosélectivité de la réaction. D’autres expériences sur la nature du groupe partant du réactif N-sulfonyloxycarbamate nous ont permis de postuler qu’une espèce nitrénoïde de rhodium était l’intermédiaire clé du processus d’amination. De plus, l’exploitation des techniques de chimie en débit continu nous a permis de développer une méthode d’amination de thioéthers et de sulfoxydes très performante, en utilisant les azotures comme source d’azote électrophile. Basée sur la décompositon photochimique d’azotures en présence d’un complexe de fer (III) simple et commercialement disponible, nous avons été en mesure de produire des sulfilimines et des sulfoximines avec d’excellents rendements. Le temps de résidence du procédé d’amination a pu être sensiblement réduit par la conception d’un nouveau type de réacteur photochimique capillaire. Ces améliorations techniques ont permis de rendre la synthèse plus productive, ce qui constitue un élément important d’un point de vue industriel.
Sulfilimines and sulfoximines are interesting building blocks that have found many applications both in medicinal chemistry and agrochemistry. During our work, we have developed new efficient methods for the synthesis of these moieties. A catalytic amount of metal complex is used to enhance the reactivity of an electrophilic nitrogen source towards thioethers and sulfoxides. Our group has developed an expertise in the development of stereoselective C-H bond amination and aziridination reactions using chiral N-mesyloxycarbamate as electrophilic amination reagents. The large scale synthesis of the chiral reagent was first investigated. It was then tested in a diastereoselective dirhodium(II)-catalyzed amination of thioethers and sulfoxides, to produce respectively chiral sulfilimines and sulfoximines in excellent yields and selectivities. During the optimization process, we have found that some additives proved instrumental to enhance both the reactivity and the selectivity of the reaction. Mechanistic studies has been carried out to elucidate the exact role of the additives. We have observed that Lewis bases, namely 4-dimethylaminopyridine (DMAP), can coordinate to a rhodium(II) dimer catalyst, modifying its structural and redox properties. These studies suggest that a mixed-valent dirhodium Rh(II)/Rh(III) complex is the catalytically active species in the thioether amination process. Moreover, we have discovered that the use of bispyridinium salts is crucial to enhance the selectivity of the amination reaction. Diastereoselectivities were also influenced by the nature of the leaving group of the N-sulfonyloxycarbamate. Based on the results, we hypothetized a rhodium nitrenoïd species as key intermediate in the amination process. Continuous flow techniques were employed in the development of a very efficient amination process of thioethers and sulfoxides, using azides as electrophilic amination reagents. Based on the photochemical decomposition of azide derivatives with a simple and commercially available iron(III) complex, we were able to produce sulfilimines and sulfoximines in excellent yields. We investigated the design of a new type of capillary photoreactor to further reduce the residence time of the amination process. The technical improvements were pivotal to enhance the efficiency and productivity of the reaction process.