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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Complexos contendo o ligante 2 - Mercaptopiridina derivados da série '[RUCL IND. 3(NO)(P-P)]'

Poelhsitz, Gustavo von [UNESP] January 2001 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:29:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2001Bitstream added on 2014-06-13T20:59:20Z : No. of bitstreams: 1 poelhsitz_g_me_araiq.pdf: 1569742 bytes, checksum: 1c42137408ccfde6142b90c3644361e4 (MD5) / Neste trabalho novos complexos nitrosilos de rutênio (II) contendo bifosfinas foram obtidos e caracterizados. A série de complexos [RuCl3(NO)(P-P)] (1) foi utilizada como precursora na obtenção de compostos do tipo [Ru(pyS)2(P-P)] (2), P-P = dppe, c-dppen, dppp e dppb e [Ru(pyS)2(NO)(η1-P-PO)]PF6 (3), P-P = dppm e dppb; pyS = 2-mercaptopiridina, em rendimentos e pureza satisfatórios. Utilizou-se as técnicas usuais para caracterização dos complexos, entre elas: espectroscopias IV, UV/vis e RMN multinuclear (1H, 13C{1H} e 31P{1H}), voltametria cíclica, voltametria de pulso diferencial e análise elementar. A maioria dos compostos forneceu monocristais adequados para estudos por difração de raios-X. Os complexos do tipo (1) foram obtidos por rotas sintéticas já estabelecidas em nossos laboratórios. O inédito fac-[RuCl3(NO)(c-dppen)] foi isolado e caracterizado, tendo inclusive a estrutura cristalográfica resolvida. Este fato permitiu a realização de interessantes comparações deste com o isômero mer-[RuCl3(NO)(dppb)]. Adicionalmente, obtevese a estrutura cristalográfica do [RuCl3(NO)(c-dppen)] e realizou-se pela primeira vez ensaios eletroquímicos para toda a série (1) e experimentos de RMN multinuclear para o mer-[RuCl3(NO)(dppb)]. Assim, aproveita-se a oportunidade para algumas discussões adicionais, importantes para o melhor entendimento da série como um todo e para fins de comparação com os complexos derivados. Os produtos isolados nas reações com a pySH mostraram ser dependentes da bifosfina utilizada, já que o mesmo procedimento foi utilizado para obtenção dos derivados (2) e (3). A série (2) acima citada, com exceção do derivado com a c-dppen que é inédito, foi obtida anteriormente na literatura por rota de síntese diferente da aqui descrita. Apresentase a caracterização e discussão dos resultados... / In this work new nitrosyl complexes of ruthenium (II) containing diphosphines were obtained and characterized. The series of compounds [RuCl3(NO)(P-P)] (1) was used as the precursor to obtain compounds of the type [Ru(pyS)2(P-P)] (2), P-P = dppe, c-dppen, dppp and dppb and [Ru(pyS)2(NO)(η1-PPO)] PF6 (3), P-P = dppm and dppb; pyS = 2-mercaptopyridine, in acceptable yields and purity. Standard techniques were used for characterization of the compounds, among them: infrared, visible-UV and multinuclear NMR (1H, 13C{1H} and 31P{1H}) spectroscopies, cyclic voltammetry, pulse diferential voltammetry and elemental analysis. Most of the studied complexes supplied crystals suitable for X-ray crystal structure analysis. Compounds of type (1) were obtained by synthetic routes previously established in our laboratories. The unpublished fac-[RuCl3(NO)(dppb)] was isolated, characterized and had its crystallographic structure solved. This fact allowed interesting comparisons with the geometrical isomer mer-[RuCl3(NO)(dppb)]. In addition, the crystallographic structure of the [RuCl3(NO)(c-dppen)] was obtained and electrochemical characterization for all series (1) as well as multinuclear NMR experiments for the mer-[RuCl3(NO)(dppb)] were carried out for the first time. These studies offer us the opportunity for some additional discussions about the precursor complexes important to the comparisons with the results for the derivative compounds. The isolated products of the reactions with 2-mercaptopyridine ligand showed to be dependent on the diphosphine from the precursor, since the same procedure was used for obtaining derivatives (2) and (3). The series (2), mentioned above, was described previously in the literature, except for the c-dppen derivative, utilizing another synthetic route. The characterization and discussion ...(Complete abstract, click electronic access below)
132

Studies on the reactivity of hexametal boride clusters

Waller, Anne January 1995 (has links)
No description available.
133

New and improved hydrogen isotope exchange reactions

Cummins, Veronica Clare January 1998 (has links)
Compounds labelled with deuterium and tritium are widely used in the life sciences. Consequently there is always a need for improved methods - better incorporation, higher specificity, reduced reaction time etc. and in the case of tritium, less radioactive waste. This thesis is concerned with such aspects. Chapter 1 is a review of the background to tritium and current methods of labelling and analysis of hydrogen isotopes. In chapter 2 the possible use of an organometallic compound - the ruthenium dihydro complex, RuH2CO(PPh3)3, which is known to catalyse the insertion of olefins into the ortho position of aromatic ketones, is explored. Solid deuterated formates e.g. 2-naphthy methyl-d-formate and d-formanilide were prepared and these were used to make the deuterated complex, RuD2CO(PPh3)3 which was used to exchange deuterium into the ortho position of aromatic ketones. Aromatic compounds with other functionalities, however were not so amenable to labelling, aromatic amides were the only other compounds successfully labelled. The method is therefore more restrictive than was hoped. A method to prepare tritiated formates by ozonolysis of 2-[T]-5-phenyloxazole to a mixed anhydride followed by nucleophillic attack was discovered. [T]-formanilide was prepared in this way but only at low levels of radioactivity (0.1 Ci/mmol, 3.67 GBq/mmol) which prevented the tritiated complex being prepared. In chapter 3 the use of zeolites as strong acid catalysts for hydrogen isotope exchange reactions was explored. Isotope exchange was carried out on simple organic molecules using hydrogen, platinum and palladium exchanged zeolite-Y with D2O and HTO as isotope source. Some studies were also carried out using solid deuterium sources with the metal exchanged zeolites. Exchange occurred using 2-naphthgyl methyl-d-formate, tetrabutyl ammonium-d-formate and potassium-d-formate. In addition, microwave activation was used in order to reduce reaction times and improve isotopic incorporation.
134

Activation of dihydrogen by ruthenium complexes containing chelating phosphines

Joshi, Ajey Madhav January 1990 (has links)
The previously reported synthesis of dinuclear mixed-valence ruthenium complexes of general formula Ru₂Cl₅(P-P)₂, P-P = DPPP, DPPB, 5,5-CHIRAPHOS, or R.R-DIOP, has been extended to include other diphosphines: P-P = DPPN, DPPH, rac-DPPCP, rac-DPCYCP, S,S-BDPP, R- and S-BINAP, or S-PHENOP. The complexes are prepared by the reaction of RuCl₃P₂(DMA)-DMA, P = PPh₃ or P(p-tolyl)₃, with one equivalent of the appropriate diphosphine. The H₂-reduction of Ru₂Cl₅(P-P)₂ complexes in DMA, or in toluene in the presence of an added base, affords the corresponding dimeric Ru(II) complexes [RuCl(P-P)(µ-Cl)]₂, P-P = DPPN, R- or S-BINAP, or S,S-BDPP, which have been characterised by NMR spectroscopy. The [RuCl(P-P)(µ,-Cl)]₂ complexes (Structure I) show a great propensity to form trichloro-bridged dinuclear species (Structure II) in the presence of neutral coordinating ligands (L). A series of trichloro-bridged complexes of the type [(L)(P-P)Ru-(µ-Cl)₃RuCl(P-P)] (e.g. P-P = DPPB; L = NEt₃, NHBu₂, CO, DMA, PhCN, Mel) have been isolated or studied in situ and characterised spectroscopically. The molecular structure of the DMSO analogue shows an S-bonded DMSO ligand with an unsymmetrical arrangement of the chelating DPPB ligand (cf. Structure II). [ Formulas omitted ] The reaction of [RuCl(DPPB)(µ,-Cl)]₂ with H₂ has been investigated. In benzene or toluene, in the absence of an added base, dihydrogen adds reversibly to the ruthenium dimer to give the remarkably simple molecular hydrogen complex (L = η²-H₂; Structure II); the η²-H₂ ligand (with an H-H distance of 0.86 Å as estimated by ¹H NMR variable temperature spin-lattice relaxation data; T₁(min) - 12 ms at 300 MHz) is replaceable by N2. The reaction of [RuCl(P-P)(µ-Cl)]₂, P-P = DPPB or 5,5-CHIRAPHOS, with H₂ in the presence of NEt₃ as the added base yields the corresponding trinuclear Ru(II) hydride complex, [RuHCl(P-P)]₃, along with [(NEt₃)(P-P)Ru(u-Cl)3RuCl(P-P)]. The hydride complexes had been synthesised previously, albeit in low yields (<10%), and the crystal structure of the CHIRAPHOS derivative obtained. During the present work the original synthetic procedure has been modified to obtain the desired [RuHCl(P-P)]₃ complexes in ∼50% yield. In addition, these species have been characterised completely by NMR spectroscopy. The conversion of [RuCl(P-P)-((µ-Cl)]₂ to the corresponding hydride derivative likely proceeds via deprotonation by NEt₃ of the initially formed molecular hydrogen species. Under hydrogen atmosphere, [RuHClQDPPB)]₃ breaks down to form the dinuclear derivative [(η²-H₂)(DPPB)Ru(µ-H)(µ-Cl)₂RuH(DPPB)] containing a molecular hydrogen ligand, which has been identified by ¹H NMR T₁ measurements; similar complexes, but with a nitrile ligand (MeCN or PhCN) in place of the η²-H₂, have also been observed. Alternative routes to ruthenium complexes containing only one diphosphine per Ru ("RuII(P-P)") have been investigated. Some of the trichloro-bridged derivatives (e.g. L = amine, CO; Structure II, see above) are also accessible through reactions of the mixed-phosphine complex RuCl₂(DPPB)(PPh₃) with amines and aldehydes, respectively. Studies on the reactions of RuCl₂(DMSO)₄ or [RuCl(p-cymene)-(µ,-Cl)]₂ with one equivalent of diphosphines show that the nature and the distribution of product(s) (i.e. RuCl₂(P-P)₂ vs. "RuCl₂(P-P)") are greatly influenced by the chelate size of the diphosphine. The "RuCl₂(P-P)" species is observed only for those phosphines which form at least a six-membered ring upon coordination to the metal. Solid-state ³¹P NMR studies indicate that the structure of RuCl₂(DPPB)(PPh₃) is similar to that of RuCl₂(PPh₃)₃, which has been characterised previously by X-ray crystallography. Reactions of RuCl₂(DPPB)(PPh₃) with chelating ligands afford six-coordinate complexes of the type RuCl₂(DPPB)(L-L), L-L = PPh₂Py, DPPM, or norbornadiene; the corresponding hydridochloro derivatives are obtained when the reactions are conducted under an atmosphere of H₂ in the presence of Proton Sponge®. The dimeric [RuCl(P-P)(µ-Cl)]₂ and the trinuclear [RuHCl(P-P)]₃ complexes described in this study are effective catalyst precursors for the hydrogenation of various alkene, ketone, imine, and nitrile substrates under relatively mild conditions (30-100 °C, 1-12 atm of H₂). A detailed kinetic study on the hydrogenation of styrene catalysed by [RuCl(DPPB)(µ-Cl)]₂ shows a first-order dependence of the maximum rate on catalyst concentration, a first- to zero-order dependence on styrene concentration and a zero- to first-order dependence on the H₂ pressure. A mechanism involving formation of the molecular hydrogen (η²-H₂) complex (see above) followed by hydrogen transfer to the substrate is proposed to account for the observations, and the rate constants at 30 ºC for the various steps have been determined. Preliminary data on acetophenone and benzonitrile hydrogenation shows that the trinuclear hydride complexes are an order of magnitude more effective than the corresponding dimeric precursors. / Science, Faculty of / Chemistry, Department of / Graduate
135

Formation and catalytic properties of some ruthenium (II) olefin complexes in solution.

Louie, Judy Sok Beng January 1968 (has links)
A kinetic study of the complex formation between chlororuthenate (II) species and the olefinic substrates, 1,1 difluoroethylene, fluoroethylene and acrylamide in aqueous hydrochloric acid solution has been carried out. The kinetics were studied either by measurement of gas uptake or by following spectrophotometrically at 680 mμ the disappearance of the blue Ru (II) species at experimental conditions in which ruthenium, olefin and chloride concentrations were varied. A two step process involving an initial dissociation of a chloride ligand seems likely for these systems, but a detailed discussion is limit ed by lack of information on the equilibria between chlororuthenate (II) species in solution. No evidence was obtained for hydrogenation by molecular hydrogen of the 1,1 difluoroethylene or fluoroethylene through a π-complex formed with the chlororuthenate (II) species. Catalytic hydration of these olefins to acetic acid and acetaldehyde respectively was however observed, and a mechanism is proposed to account for this; this appears to be the first, report of a transition metal catalysed hydration of olefins. Acrylamide was not hydrated but could be catalytically hydrogenated to propionamide; the kinetic data fit a well established mechanism. Similarities between the hydrogenation and hydration processes are pointed out. / Science, Faculty of / Chemistry, Department of / Graduate
136

Ruthenium Catalysts for Olefin Metathesis: Understanding the Boomerang Mechanism and Challenges Associated with Stereoselectivity

Bates, Jennifer M. 13 May 2014 (has links)
Ruthenium-alkylidene catalysts are widely used in organic synthesis to generate new C=C bonds in a process known as olefin metathesis. Much research has been dedicated to examining the organometallic species responsible for this transformation, and understanding the benefits and limitations of current state-of-the-art catalysts allows for the design of new and more efficient alternatives. Over the past decade, a topic of much debate has been the so-called “boomerang” (or release-return) mechanism, and whether it operates in the Hoveyda catalysts. The ability of the styrenyl ether ligand, once released from the catalyst during initiation, to be recaptured by the vulnerable active species, has major implications in catalyst recyclability. Chapter 3 describes the use of a 13C-labeled styrenyl ether ligand, in conjunction with an unlabeled second-generation Hoveyda catalyst, to confirm the operation of this mechanism during catalysis. This study demonstrated that the labeled styrenyl ether ligand competes with the substrate for the four-coordinate active species: the labeled moiety rapidly incorporates into the Hoveyda catalyst during both ring-closing- and cross-metathesis examples. Chapter 4 focuses on addressing the selectivity challenges associated with olefin metathesis, particularly during RCM macrocyclization reactions where E/Z mixtures are typically obtained. Designing catalysts that can dictate and control the stereochemistry of a product mixture minimizes waste, and ultimately reduces cost by eliminating the need for separation techniques. A great deal of research has focused on constructing catalysts with ligands that can exert the appropriate steric pressure on a metallocyclobutane intermediate, in order to generate the desired Z-product. Chapter 4 of this thesis examined the ability of a Hoveyda- and Grubbs-type catalyst containing monothiolate ligands, to promote Z-selective RCM macrocyclization. Catalyst lifetimes were also examined, in addition to the impact of altering reaction conditions, specifically concentration, on product distribution. These experiments afford information that will aid in the design of improved catalysts for Z-selective RCM macrocyclization.
137

Some chiroptical effects on the photophysics and photochemistry of tris(bipyridine)ruthenium(II) ions in solution

Sparks, Robert Henry January 1979 (has links)
The photoracemization of Ru(bipy)₃⁺⁺ in aqueous solution was studied. Quenching studies show the involvement of the (CT)³ Ru(bipy)₃⁺⁺ in the mechanism of racemization and the low quantum yield (2.9 x 10⁻⁴) shows that this state is asymmetric. Quenching studies show no increase of racemization rate for Ru(I) or (III) species. The temperature dependence gives evidence for a dissociative racemization mechanism. Quenching with Co(acac)₃ shows chiroselective electron transfer as measured by the resulting photochemistry. / Science, Faculty of / Chemistry, Department of / Graduate
138

Fluorosulfates of silver, ruthenium, and osium

Leung, Patrick Cheung Shing January 1979 (has links)
A number of synthetic routes to silver(II) fluorosulfate, Ag(SO₃F)₂, were systematically explored. The most suitable and versatile route was found to be the oxidation of silver metal by a solution of bisfluorosulfuryl peroxide, S₂0₆F₂, in fluorosulfuric acid, HSO₃F, according to: [chemical reaction] Additional methods which were found to be suitable involved the oxidation of a wide variety of silver(I) compounds such as Ag₂0 or AgSO₃F by S₂O₆F₂' or the insertion of S0₃ into AgF₂. Structural conclusions on Ag(S0₃F)₂ and the other compounds synthesized subsequently were based on the vibrational, electronic and electron spin resonance spectra, as well as on magnetic susceptibility measurements made between 300 and 77 K. Ag(S0₃F) ₂was found to be a true compound of divalent silver, with the Ag²⁺ ions in either square planar or tetragonally elongated octahedral environment. The only other example of a binary silver(II) compound is AgF₂. and characterized. The reactions of bromine(I) fluorosulfate with metallic silver and other silver(I) substrates resulted in a mixed valence complex Ag[sup I]Ag[sup II](SO₃F)₄ . Its potassium analogue K₂AgCSO₃F)₄, as well as two hexakisfluorosulfato- metallate (IV) complexes AgPt[sup= IV] (SO₃F)₆ , and AgSn[sup= IV] (SO₃F)₆, and the N-donor ligand complex [Ag(bipy)₂l (SO₃F)₂ (i-n which bipy = 2,2'-bipyridine) were also synthesized. The attempt to synthesize a silver(III) fluorosulfato complex by direct insertion of SO₃ into CsAgF₄ resulted in the fluorination of SO₃, to give S₂O₆F₂ and CsAg(SO₃F)₃. Finally, the solvolysi of Ag(SO₃F)₂ in trifluoromethylsulfuric acid, HSO₃CF₃, allowed its conversion into Ag(SO₃F₃). The principal synthetic route, the oxidation of metal by S₂O₆F₂ solutions in HSO₃F, was found to be useful in the preparation of Ru(SO₃F)₃. Ruthenium was also found to form a number of anionic derivatives with the metal in the +3 or +4 oxidation state, as in M[Ru(SO₃F)₄] with M = Cs⁺, ClO₂⁺ ; M₂[Ru(SO₃F)₆ with M = Cs⁺, K⁺; and Cs[Ru(SO₃F)₅]. Two different forms of Os(SO₃F)₃ were found. Initial oxidation of osmium metal with S₂O₆F₂ yielded the bright green a-Os(SO₃F)₃, which was converted to the light green β-form on long standing in S₂O₆F₂. / Science, Faculty of / Chemistry, Department of / Graduate
139

Characterization of chlorohydridobis (tertiaryphosphine) ruthenium (II) complexes, and their use as homogeneous hydrogenation catalysts

Thorburn, Ian Stuart January 1980 (has links)
The thesis describes a study of the catalytic hydrogenation of an olefinic substrate by the complex hydridochlorobis(triphenylphosphine) ruthenium(II) and an investigation of the complex in the solid state and in solution. The visible spectra of the complex, (HRuCl(PPh₃)₂)₂, at a series of concentrations showed that Beer's law is not obeyed, and that in solution a dissociative equilibrium exists: (1) (HRuCl(PPh₃)₂)₂ K ⇆ (2HRuCl(PPh₃)₂ The complex in N,N-dimethylacetamide solution was found to be an effective catalyst for the homogeneous hydrogenation of hex-l-ene. A detailed kinetic study on this system revealed a mechanism involving initial formation of a σ-alkyl intermediate which then reacts with molecular hydrogen to produce the saturated product and regenerate the catalyst: (2) HRuCl(PPh₃)₂ + olefin k₁ ⇆ k₋₁ RuCl(PPh₃)₂(alkyl) (3) HRuCl(PPh₃)₂(alkyl) + H₂ k₂→ HRuCl(PPh₃)₂ + alkane. The mechanism is quite different from that reported for the same catalyst system but using acrylamide as substrate, thereby showing that the nature of the substrate can have a pronounced affect on the course of hydrogenation. Addition of triphenylphosphine and lithium chloride to the (HRuCl(PPh₃)₂)₂- hex-l-ene system were found to decrease and increase the rate of hydrogenation, retrospectively. The added phosphine likely competes with the olefinic substrate for a coordination site; the role of the chloride ion is more uncertain, but a more active catalyst containing more than one chloride ligand is the most obvious rationale. To enhance the solubility of this hydridophosphine type catalyst the tri-p-tolylphosphine analogue of the triphenylphosphine complex was prepared; the variable temperature ¹H and ³¹P{¹H}-solution n.m.r. of the (HRuCl(P(p-tolyl)₃)₂)₂ complex showed the presence of both monomer and fluxional dimer. Addition of dimethyl maleate to the complex in order to obtain a Ru-alkyl species (equation (2)) gave very complex spectra which could not be interpreted in terms of a single species, but there was some evidence for a hydrido(olefin) species rather than an alkyl. An x-ray analysis of the p-tolyl complex confirmed the expected chloro-bridged dimeric structure of these hydridochlorobis(phosphine) species. There is a square pyramidal coordination geometry about each ruthenium atom, and two such centres share a basal edge, but the molecule has no symmetry as a result of the small hydride ligands allowing distortion. / Science, Faculty of / Chemistry, Department of / Graduate
140

The synthetic, structural and kinetic investigation of novel neutral and cationic Ruthenium(ll) complexes

Malan, Frederick Pieter 01 July 2014 (has links)
M.Sc. (Chemistry) / Please refer to full text to view abstract

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