Download or read book Synthesis Characterization and Reactivity of Rhenium III Complexes for Catalytic Stoichiometric and Insertion Reactions written by Damaris Esther Pérez and published by . This book was released on 2018 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis Characterization and Reactivity of Rhenium Dithiodiolate and Monothiodiolate Complexes written by Pitak Chuawong and published by . This book was released on 2001 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: The rhenium dithiodiolate, Hydrido-tris-(3,5-dimethyl- 1 -pyrazol yl) borato(ethane- 1,2-dithiodiolato)(oxo)rheni um(V), and Hydrido-tris-(3,5-dimethyl- 1 -pyrazolyl)borato(phenylethanedithiodiolato)(oxo)rhenium(V), were synthesized by reductive cyclocondensation of alkane-1,2-dithiols with Tp'Re03 in a one pot fashion. The rhemium monothiodiolate, Hydrido-tris-(3,5-dimethyl- 1 -pyrazolyl) borato(ethane- 1,2-monothiodiolato)(oxo)rhenium(V), and Hydrido-tris-(3,5- dimethyl- 1 -pyrazolyl)borato(propanemonothiodiolato)(oxo)rhenium(V), were also synthesized by using the same procedure. The syn and anti isomers of rhenium phenylethanedithiodiolate and rhenium propanemonothiodiolate were characterized by using COSY, nOe, and HSQC experiments. An X-ray crystal structure of the rhenium ethanedithiodiolate was obtained, and an unusually small dihedral angle (S-C-C-S) of about 12° was observed. The solution conformation of these compounds was investigated by using a Karplus relationship between vicinal coupling constants and dihedral angle. The dihedral angle for the ethanedithiodiolate appeared to be 38° indicating a staggered geometry for the ring. All of these complexes failed to cyclorevert to any detectable extent at 120°C after 7 days. This observation reflects the thermal stability of rhenium dithiodiolate and monothiodiolate complexes. Energetics of ethylene addition to tetrathioperrhenate anion (ReS4−) and addition of hydrogen sulfide to the alkene adduct were calculated by DFT calculation using LACVP** basis set with B3LYP functionals. The heat of reaction of ethylene addition to ReS4− was 15.4 kcal/mol, and 111.1 kcal/mol for addition of hydrogen sulfide to the alkene adduct. These results are consistent with the stability of the dithiodiolate complex toward cycloreversion reaction. Reaction of Tp'Re03 and ethylene sulfide led to the rhenium ethanedithiolate complex both with and without acid catalysis. This observation led to a proposed multi step mechanism.

Download or read book Synthesis Characterization and Reactivity of Rhenium I Tris acetylene and Oxo Bis acetylene Complexes Oxygen Atom Transfer Reactions of Rhenium Triazacyclononane Compounds written by Rebecca Renae Conry and published by . This book was released on 1991 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of Rhenium Complexes for Use in Catalytic Oxidation Reduction and Carbonylation Reactions written by Jessica Lee Smeltz and published by . This book was released on 2013 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis Characterization and Reactivity of Technetium and Rhenium Complexes in Intermediate Oxidation States written by Harvey Stewart Trop and published by . This book was released on 1979 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis Characterization and Reactivity of Rhenium platinum Dihydrides written by Edward Walter Rutter and published by . This book was released on 1989 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis Characterization and Reactivity of Prochiral Ruthenium Clusters and Bimetallic Rhenium Complexes with an Unsymmetrical Diphosphine and Hard Soft Donor Ligands written by Darrell D. Mayberry and published by . This book was released on 2019 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Synthesis Characterization and Reactivity of High Oxidation State Rhenium Imido and Oxo Complexes written by Tiow-Gan Ong and published by . This book was released on 2000 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis Characterization and Reactivity Studies of Hexanuclear Rhenium Cluster Complexes with Oxygen and Sulfur Donor Ligands written by Julia A. Edwards and published by . This book was released on 2008 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Olefin Polymerization written by Walter Kaminsky and published by Wiley-VCH. This book was released on 2006-08-18 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: With an enormous velocity, olefin polymerization has expanded to one of the most significant fields in polymers since the first industrial use about 50 years ago. In 2005, 100 million tons of polyolefins were produced - the biggest part was catalyzed by metallorganic compounds. The Hamburg Macromolecular Symposium 2005 with the title "Olefin Polymerization" involved topics such as new catalysts and cocatalysts, kinetics, mechanism and polymer reaction engineering, synthesis of special polymers, and characterization of polyolefins. The conference combined scientists from different disciplines to discuss latest research results of polymers and to offer each other the possibility of cooperation. This is reflected in this volume, which contains invited lectures and selected posters presented at the symposium.

Download or read book Supported Molecular Rhodium Complexes and Dimers written by Dicle Yardimci and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Solid catalysts incorporating transition metals are important in industry, providing cost- effective syntheses, ease of separation from products, and control of selectivity. The metal is often expensive and thus often constitutes only about one percent of the catalyst mass, being highly dispersed on a high-area support. Dispersed metals in industrial catalysts are usually highly nonuniform in structure and challenging to characterize, and consequently relationships between structure and catalyst performance are typically less than fully understood. Our approach to the investigation of supported metal catalysts involves the synthesis of uniform catalytic sites that have essentially molecular character. Supported molecular catalysts can be characterized spectroscopically to provide fundamental understanding of the catalyst structure under reactive atmospheres, and thereby determination of structural changes of working catalysts that can be correlated with the catalytic activity and selectivity. The sample characterization techniques used in this work included infrared (IR), extended X-ray absorption fine structure (EXAFS), and X-ray absorption near edge structure (XANES) spectroscopies, as well as gas chromatography (GC) and mass spectrometry (MS) to characterize reaction products. The catalysts were prepared from the organometallic precursor Rh(C2H4)2(C5H7O2) and the supports MgO and zeolite HY. These catalysts initially incorporated site-isolated, mononuclear rhodium complexes on the supports. The complexes on MgO were treated in H2 at elevated temperatures to form the smallest supported rhodium clusters--rhodium dimers. These catalysts are essentially molecular in character and allowed tailoring of the rhodium nuclearity, the ligands bonded to the rhodium, and the rhodium-support interface. The catalysts incorporated mononuclear Rh(C2H4)2 and Rh(CO)2 complexes; dimeric rhodium clusters with ethyl ligands, and dimeric rhodium clusters with CO ligands. These were tested for the hydrogenation of ethylene. Rhodium in various forms is highly active for catalytic hydrogenation of olefins. However, rhodium has been little investigated for diene hydrogenation, because, like other noble metals in the form of supported clusters or particles, it is unselective. We postulated that new catalytic chemistry of rhodium could emerge if the catalytic species were essentially molecular so that they could be tuned by the choice of the rhodium nuclearity and ligands. Thus, we investigated the influence of the following catalyst design variables on the activity and selectivity of supported rhodium for 1,3-butadiene hydrogenation: (a) the metal nuclearity, ranging from one to several; (b) the electron-donor properties of the support (MgO vs. zeolite Y); and (c) other ligands on the rhodium, including reactive hydrocarbons (ethylene or ethyl) and CO. The data show that extremely small MgO-supported rhodium clusters that are partially carbonylated are highly active and selective for the hydrogenation of 1,3-butadiene to give n-butenes. The support, the rhodium nuclearity, and the ligands on rhodium are crucial to the catalyst selectivity, transforming a metal that is typically regarded as unselective for 1,3-butadiene hydrogenation into one that is highly selective even at high conversions. Transition metals in complexes and clusters tend to aggregate to form of more stable, bulk particles under reactive atmospheres, causing catalyst deactivation. We investigated the initial steps of the aggregation of supported metal species that were highly dispersed on MgO and zeolite HY, synthesizing samples that incorporated supported rhodium complexes bonded to ligands with different reactivities (including the support), and then spectroscopically investigated the formation of extremely small rhodium clusters in the presence of H2. The stability of the rhodium complexes and the stoichiometry of the surface-mediated transformations are regulated by the support and the other ligands bonded to the rhodium, being prompted at a lower temperature with zeolite HY than the better electron-donor MgO when the rhodium complexes incorporate ethylene ligands, but occurring more facilely on the MgO than on the zeolite when the ligands are CO. The preparation of highly uniform rhodium dimers is possible. We infer that results such as those presented here may be useful in guiding the design of stable, highly dispersed supported metal catalysts by choice of the support and other ligands on the metal.

Download or read book Synthesis Characterization and Reactivity of Organometallic Complexes of Uranium and Plutonium in the 2 and 3 Oxidation States written by Cory J. Windorff and published by . This book was released on 2017 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on the synthesis, characterization, and reactivity of unique organometallic complexes of uranium, plutonium, and the lanthanides in efforts to expand the limits of known redox chemistry of these elements. The results in this dissertation extend investigations of previously established reduction reactions involving these metal ions to extend them to more challenging systems. These reactions utilized the tri(cyclopentadienide) coordination environment examining the differences in the substitution pattern on the cyclopentadienide rings, particularly the Cp'' ligand [Cp'' = C5H3(SiMe3)--1,3]. In the course of these studies, the +2 oxidation state for plutonium was confirmed, and the most stable form of UII to date was isolated. To accomplish the plutonium chemistry, several surrogate syntheses were performed using lanthanides of similar size and reactivity to that of plutonium, namely cerium and neodymium. These experiments examined the electronic structure to compare and contrast the +2 oxidation state across the actinide series.In Chapter 1 29Si NMR spectra were recorded for a series of uranium complexes containing silicon and the data have been combined with results in the literature to determine if any trends exist between chemical shift and structure, ligand type, or oxidation state. Data on 48 paramagnetic inorganic and organometallic uranium complexes are presented. The survey reveals that although there is some overlap in the range of shifts of UIV complexes versus UIII complexes. In general UIII species have more negative shifts than their UIV analogs. The single UII example has the most negative shift of all at --322 ppm at 170 K. With only a few exceptions, UIV complexes have shifts between 0 and --150 ppm (vs. SiMe4) whereas U III complexes resonate between --120 and --250 ppm. The small data set on UV species exhibits a broad 250 ppm range centered near 40 ppm. The data also show that aromatic ligands such as cyclopentadienide, cyclooctatetraenide, and the pentalene dianion, exhibit less negative chemical shifts than other types of ligands.Chapter 2 describes the synthesis of new molecular complexes of U II that were pursued to make comparisons in structure, physical properties, and reactivity with the first UII complex, [K(crypt)][Cp '3U], 21-U (Cp' = C5H 4SiMe3, crypt = 2.2.2-Cryptand). Reduction of Cp ''3U, 20-U, [Cp'' = C 5H3(SiMe3)2--1,3] with KC 8 in the presence of crypt or 18-crown-6 generates [K(crypt)][Cp ''3U], 22-U, or [K(18-crown-6)(THF) 2][Cp''3U], 23-U, respectively. The UV/vis spectra of 22-U and 21-U are similar, and they are much more intense than those of UIII analogs. Variable temperature magnetic susceptibility data for 21-U and 22-U reveal a lower room temperature chiMT value relative to the experimental value for the 5f3 U III precursors. Stability studies monitored by UV/vis spectroscopy show that 22-U and 23-U have t 1/2 values of 20 and 15 h at room temperature, respectively, vs 1.5 h for 21-U. Complex 23-U reacts with H2 or PhSiH3 to form the uranium hydride, [K(18-crown-6)(THF) 2][Cp''3UH], 26. 21-U and 23-U both reduce cyclooctatetraene to form uranocene, (C8H8) 2U, as well as the UIII byproducts [K(crypt)][Cp '4U], 28-U, and Cp'' 3U, 20-U, respectively.In Chapter 3 Cp'4U, 37-U, was synthesized from (a) KCp' and [Cp' 3U(THF)][BPh4], 36, (b) Cp' 3U, 8-U, and Cp'2Pb,30, and (c) [K(crypt)][Cp'4U], 28-U, and AgBPh4 and identified by X-ray crystallography as a rare example of a structurally-characterized tetrakis(cyclopentadienyl)UIV complex. The corresponding Th complex, Cp'4Th, 37-Th, was obtained from the direct combination of ThBr4(THF)4 with excess KCp' in low yield. During the preparation of Cp' 3UMe, 35, the precursor of the [Cp '3U(THF)][BPh4], 36, reagent used above, it was discovered that the reaction of Cp'3UCl, 33-U, and MeLi gives a mixture of Cp'3UMe, 35 and 33-U that can co-crystallize better than 35 in pure form. Although 35 typically is an oil, a mixture of 35 and 33-U forms single crystals that are suitable for X-ray crystallography and contain a 4:1 ratio of the compounds. Hence, forming a mixture provided a new way to get structural data on the oil, 35. 33-U and Cp'3UI, 34, were also crystallographically characterized for comparison with the Cp '3UMe/Cp'3UCl, 35/33 crystals. (Abstract shortened by ProQuest.).

Download or read book Synthesis Characterization and Reactivity of Low valent Rhenium Oxo alkoxide and Hydride Complexes written by Torsten K. G. Erikson and published by . This book was released on 1988 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rhenium catalyzed Oxygen atom Transfer Reactions written by Eric C. Brown and published by . This book was released on 2002 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: In situ reduction of hydrido-tris-(3,5-dimethylpyrazolyl)borato(trioxo) rhenium(V) with triphenylphosphine or triethylphosphite leads to a reactive rhenium(V) species that catalytically deoxygenates epoxides at 75-105°C. The reaction is stereospecific, except for trans- and cis-butene oxide which formed minor amounts of the opposite isomer. A variety of different functional groups were tolerated and even epoxides that reacted slowly could be pushed to greater than 95% conversion given extended time and/or higher temperature. The absence of clustering processes shows how the choice of ligand can have a major influence on the design of the catalytic cycle. The rhenium(V) species formed from reduction of Tp'ReO3 was identified as Tp'Re(O)(OH)2. Tp'Re(O)(OH)2 reacted with ethanol and HCl to form ethoxide and hydroxo chloride complexes, respectively. In addition, Tp'Re(O)(OH)2 was an excellent catalytic and stoichiometric reagent for the deoxygenation of epoxides and sulfoxides. Loss of water from Tp'Re(O)(OH)2 to form the catalytically active species Tp'Re02 was shown to be a necessary preequilibrium process. The kinetic behavior of the catalytic system is complex. First-order behavior in [Re][subscript T], zero-order dependence in [PPh3] and saturation behavior for epoxide were observed. The reversible formation of a coordinated epoxide complex was proposed to explain the saturation behavior. The epoxide complex was shown experimentally and computationally to engage in two separate reactions: ring expansion to form a syn-diolate complex, and direct fragmentation to alkene and trioxide. A steady-state concentration of diolate is eventually reached explaining a "burst" of alkene production prior to generation of a pseudo-zero-order catalytic system. The diolate formed is the syn-isomer, which is the kinetically formed product. Direct epoxide fragmentation is the primary source of alkene. This process was determined to be four times faster than ring expansion for cis-stilbene oxide. The synthesis and characterization of a tethered-epoxide Cp* rhenium trioxide complex has been achieved. Reduction of this complex leads to an unsaturated rhenium(V) species that is immediately complexed by the tethered epoxide. Experimental data and molecular mechanics modeling support intramolecular coordination of the epoxide to the rhenium center. These results confirm that the coordinate epoxide is a viable intermediate in rhenium-catalyzed epoxide deoxygenations.

Download or read book The Synthesis Characterization and Reactivity of Nitro phosphine ruthenium III Complexes written by Randolph A. Leising and published by . This book was released on 1989 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book American Doctoral Dissertations written by and published by . This book was released on 1992 with total page 796 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Surface Organometallic Chemistry Molecular Approaches to Surface Catalysis written by Jean-Marie Basset and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface organometallic chemistry is a new field bringing together researchers from organometallic, inorganic, and surface chemistry and catalysis. Topics ranging from reaction mechanisms to catalyst preparation are considered from a molecular basis, according to which the "active site" on a catalyst surface has a supra-molecular character. This. the first book on the subject, is the outcome of a NATO Workshop held in Le Rouret. France, in May. 1986. It is our hope that the following chapters and the concluding summary of recommendations for research may help to provide a definition of surface organometallic chemistry. Besides catalysis. the central theme of the Workshop, four main topics are considered: 1) Reactions of organometallics with surfaces of metal oxides, metals. and zeolites; 2) Molecular models of surfaces, metal oxides, and metals; 3) Molecular approaches to the mechanisms of surface reactions; 4) Synthesis and modification of zeolites and related microporous solids. Most surface organometallic chemistry has been carried out on amorphous high-surf ace-area metal oxides such as silica. alumina. magnesia, and titania. The first chapter. contributed by KNOZINGER. gives a short summary of the structure and reactivity of metal oxide surfaces. Most of our understanding of these surfaces is based on acid base and redox chemistry; this chemistry has developed from X-ray and spectroscopic data, and much has been inferred from the structures and reactivities of adsorbed organic probe molecules. There are major opportunities for extending this understanding by use of well-defined (single crystal) oxide surfaces and organometallic probe molecules.