Thesis (Ph.D.)--York University, 2005. Graduate Programme in Chemistry. / Typescript. Includes bibliographical references (leaves 160-178). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNR11543

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Resumo: O presente trabalho contemplou a síntese e a caracterização espectroscópica de complexos pirazólicos de rutênio(II), usando como precursores o composto [RuCl2(DMSO)4] ou o sal de rutênio RuCl3.3H2O, dependendo do caso. Foram obtidas três séries de compostos inéditos: a primeira, contendo ligantes pirazólicos monodentados, de fórmula geral [RuCl2(DMSO)2L2] {L = HPz (A2), HdmPz (A3), HIdmPz (A4)}; a segunda série envolveu o uso do ligante pirazólico bidentado 3-(2'- piridil)pirazol, e pode ser representada por [RuX2(py-pzH)2].H2O {X = Cl (B1), NCS (B2)}; o terceiro conjunto de compostos apresenta o ligante 3,5-dicarboxipirazol (H3pzdc) e possui a fórmula geral [RuCl2(H3pzdc)2(L)].xH2O {L = bpy, x = 1 (C1); L = py-pzH, x = 2 (C2); L = phen, x = 2 (C3)}. Além dessas três séries de compostos foi obtido, também, o complexo [RuCl2(dcbpy)2].H2O (D1) contendo o ligante bidentado 4,4'-dicarboxi-2,2'-bipiridina (dcbpy), já conhecido da literatura. A motivação do trabalho está baseada na tentativa de utilização destes complexos pirazólicos de Ru(II) como fotossensibilizadores alternativos ao complexo de rutênio N3 (cisditiocianatobis( 2,2'-bipiridina-4,4'-ácido dicarboxílico)rutênio(II)) que vem sendo usado como sistema-modelo em células solares sensibilizadas por corante (DSSC). Por essa razão, o ligante 3,5-dicarboxipirazol (H3pzdc) foi utilizado na síntese dos compostos da série C1-C3, pois a literatura tem reportado que a presença de grupos carboxílicos no complexo, entre outros grupos de ancoragem, propicia uma adsorção adequada do corante na superfície do semicondutor. Os dados espectroscópicos (espectroscopia vibracional na região do IV, espectroscopia eletrônica e reflectância difusa na região do UV-Vis, espectroscopia de luminescência e espectroscopia de ressonância... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The principal goal of the present work was the synthesis and the spectroscopic characterization of ruthenium(II) pyrazolyl complexes, using as precursor the compound [RuCl2(DMSO)4] or the salt of ruthenium RuCl3.3H2O, depending on the case. Three inedit compounds series had been obtained: the first one, containing monodentate pyrazolyl ligands of the general formula [RuCl2(DMSO)2L2] {L = HPz (A2), HdmPz (A3), HIdmPz (A4)}; the second series involved the use of the bidentate ligand 3-(2'-pyridil)pyrazole, and can be represented by [RuX2(py-pzH)2].H2O {X = Cl (B1), NCS (B2)}; the third set of compounds contain the ligand pyrazole-3,5-dicarboxylic acid (H3pzdc) and has the general formula [RuCl2(H3pzdc)2(L)].xH2O {L = bpy, x = 1 (C1); L = py-pzH, x = 2 (C2); L = phen, x = 2 (C3)}. The complex [RuCl2(dcbpy)2].H2O (D1) containing the 4,4'-dicarboxy-2,2'- bipyridine ligand (dcbpy), already known literature, was also prepared in this work. The motivation of this research is based on the attempt of use these Ru(II) pyrazolyl complexes as alternative photosensitizers to the complex of ruthenium N3 (cisdithiocyanatebis( 4,4'-dicarboxy-2,2'-bipyridine)ruthenium(II)) that it has been used as prototipe in dye sensitized solar cells (DSSC). For this reason, the ligand pyrazole- 3,5-dicarboxylic acid (H3pzdc) was used in the synthesis of the compounds C1-C3, due to the known effective adsorption capability of anchoring groups, such as carboxylic anions, in the surface of the semiconductor. The spectroscopic data (NMR, IR, UV-Vis and Luminescence) as well the analytical results were in accordance with the proposed stoichiometric compositions for the complexes. It is important to point out that an advanced study of RMN it was realized for the complexes B2, C1 and C3, which evidenced the presence of isomers in solution. / Orientador: Regina Célia Galvão Frem Di Nardo / Coorientador: Luiz Antonio Andrade de Oliveira / Banca: Marian Rosaly Davolos / Banca: Elia Tfouni / Mestre

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>Magister Scientiae - MSc / Herein we report the successful synthesis of a class of stable and flexible Schiff-base chelators capable of coordinating both ruthenium (II) and rhenium (VII) and which would be catalytically active for oxo-transfer reactions. The synthesis of bidentate (L1), tetradentate (L2-L3), and multidendate ligands (DL1-DL4) of nitrogen was a result of a reaction of primary amine with 2-pyridinecarboxaldehyde. Ligand (L3) is reported herein for the first time. The amines (n-propylamine, ethylenediamine, butanediamine, diaminobutane, propylene iminopyridyl (DAB-PPI) dendrimer) were varied as to afford metal complexes that exhibit different physical and chemical properties. The ligands were isolated and fully characterized by IR, NMR spectroscopy and elemental (H, C, N) analysis.The Schiff-base complexes of methyltrioxorhenium (MTO): Methyl(n-pyridin-2-yl)methylene)propan-1-amine)trioxorhenium (C1), Methyl([bis(pyridin-2- yl)formylidene]butane-1,4-diamine)trioxorhenium (C2), Methyl(diaminobutane propylene imonopyridyl)trioxorhenium G1(DC1) and G2(DC2) have exhibited sensitivity to water than MTO itself. Rapid ligand-exchange reactions in solution are observed at elevated temperatures. The MTO Schiff-base complexes are also slightly sensitive to light and slowly decompose as they are exposes to air. These complexes were isolated and fully characterized by IR, NMR, UV-Vis, EA and MS. In the ESI mass spectra of compound C1-C2 and DC1-DC2 show the peaks of the Schiff-base ligand and the MTO moiety separately, without a traceable fragmentation pattern. The isotopic cluster and the molecular ion peak were observed.The mononuclear ruthenium compounds (B1 and B3) were prepared from dichlorotetrakis(dimethyl sulfoxide)ruthenium (II) metal precursor by reacting the synthesized ligands (L2 and L3) with the metal precursor. Compounds (B2 and B4) were obtained by subsequently stabilizing the neutral compounds (B1 and B2) as hexaflourophosphate salts via metathesis employing thallium (I) hexafluorophosphate (V).The homobimetallic cationic compound (B5) was synthesized by reacting the dinuclear complex [(p-cymene)2RuCl2]2 with ligand (L4).The neutral tetranuclear (V1 and V3) and octanuclear (V2 and V4) (N,N) ruthenium(II) metallodendrimers were synthesized mimicking the same route as for the neutral mononuclear compounds (B1 and B3). The compounds (V1-V4) were prepared from the dichlotetrakis(dimethyl sulfoxide)ruthenium(II) based on the synthesized dendritic scaffolds (DL1-DL4). Compounds (V5 and V6) were fashioned in a similar manner to compound (B5),by reacting the iminopyridyl dendritic scaffolds (DL1 and DL3) with the dinuclear precursor[(p-cymene)2RuCl2]2 to afford two complexes of the type [{(p-cymene)RuCl2}4G1, V5] and [{p-cymene)RuCl2}8G2, V6]. Electronic spectra of the prepared complexes were obtained (in a Sharpless Biphasic solvent system: CCl4:MeCN:H2O) in order to understand the nature of the active species in the catalytic cycle and to propose a mechanism for the catalytic cycle .Confirmation of the prepared complexes (B1-V6) was done using several spectroscopic techniques (IR, NMR, UV-Vis, ESI-MS) in conjuction with elemental analysis.The compounds C1-DC2 were then tested towards the epoxidation of selected cyclic alkenesi.e cyclohexene and cis-cyclooctene, respectively and straight chain alkenes. The catalyzed epoxidation reactions were carried out at room temperature employing using Urea hydrogen peroxide adduct (UHP) as the oxidant and dichlomethane (DCM) as the solvent. The complexes displayed high catalytic activity and selectivity when applied to the epoxidation of cyclohexene and cis-cyclooctene with urea hydrogen peroxide adduct (UHP) as oxidant in dicholoromethane. The epoxidation reaction was quantified using gas chromatography.Conversions reached 100% for all the complexes within 6 hours. The catalytic activity of complex C1 and C2 was relatively low compared to the catalytic activity of complex DC1 and DC2.

Olefin metathesis is an outstandingly versatile methodology for the catalytic assembly of carbon-carbon bonds. Metathesis methodologies have been widely embraced since the advent of easily-handled ruthenium catalysts. However, industrial implementation has lagged. Problems of reliability and productivity arising from catalyst decomposition have impeded broad uptake of metathesis in process chemistry. Such challenges also hamper deployment of metathesis in forefront applications such as chemical biology. Better understanding of the mechanisms by which catalysts decompose can thus improve performance in demanding applications, as well as providing guidelines for informed process and catalyst design. Oxygen is often viewed as a relatively innocuous contaminant in reactions promoted by these late transition metal catalysts. Indeed, multiple reports comment on the desirability and operational simplicity of metathesis in air. We suspected, however, that deleterious impacts of O2 may be masked by the high catalyst loadings typically deployed in such reports. The first part of this thesis focuses on examining the robustness of leading metathesis catalysts toward oxygen. Systems examined include the classic, dominant N-heterocyclic carbene (NHC) derivatives, as well as recent breakthrough analogues containing cyclic alkyl amino carbene (CAAC) ligands. Both are shown to be decomposed by oxygen, but the CAAC catalysts are found to be not only more productive, but significantly more O2-tolerant. This is important as it overturns the widespread belief that high catalyst activity is invariably a trade-off against higher sensitivity. Studies of the initial oxidation event for the second-generation Grubbs catalyst RuCl2(H2IMes)(PCy3)(=CHPh) suggest that [2+2] cycloaddition of O2, as well as bimolecular decomposition of the four- coordinate species generated by PCy3 oxidation, account for ca. 90% of the observed decomposition. A previously-proposed pathway involving attack of O2 at the benzylidene ligand appears to be a minor contributor. In Chapter 3 of this thesis, a new strategy for inhibiting catalyst decomposition is examined. Specifically, cationic metathesis catalysts were encapsulated within a supramolecular resorcinarene capsule, which self-assembles around the catalysts in water-saturated toluene. Encapsulation nearly doubles RCM yields relative to the parent, neutral catalyst in water-saturated toluene. The increased catalyst productivity is enabled by site-isolation of the catalyst within the capsule, which prevents bimolecular decomposition, and by the hydrophobic nature of the capsule interior, which limits decomposition by water. A final study focuses on attempts to identify a more robust catalyst via ligand redesign. Examined for this purpose are recently reported, electron-rich pyridinylide aminophosphines (PyAPs; these take the general form R2P–N=Ar), which exhibit enhanced s-donor properties relative to NHCs. Strategies for incorporation of PyAP ligands into Ru metathesis catalysts are developed, and the catalytic activity of these species is described. PyAP catalysts are found be significantly less active than the corresponding NHC catalysts, despite their higher donicity. Poor performance results from facile catalyst decomposition. Where the N=Ar group lacks substituents at the ortho sites, o- metalation enables decomposition of the precatalyst. More problematically, the nitrogen atom appears to participate in nucleophilic attack on the key, metathesis-enabling [Ru]=CHR functionality, limiting the potential use of this class of phosphine in metathesis. Criteria for the development of more robust second-generation phosphine catalysts are proposed.

<p> The hydrogenolysis of propane over 0.5 weight percent ruthenium supported on (see symbol in text)-alumina in a continuous stirred-tank catalytic reactor was studied at various pressures and temperatures. </p> <p> The reaction orders with respect to propane and hydrogen and the activation energies were examined at various pressures. A mechanism was proposed and a Hougen-Watson type of rate expression was obtained from the analysis of the proposed mechanism. </p> <p> The product distributions were studied at various pressures and temperatures. A reaction network involving reversible adsorption-desorption of the hydrocarbons and irreversible rupture of the carbon-carbon bonds in the surface species was applied to the experimental data. </p> <p> The proposed mechanism was consistent with the data for kinetics and selectivity. </p> / Thesis / Master of Engineering (MEngr)

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