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Synthesis of Dihydropyridines and Pyridines from Imines and Alkynes via C-H Activation

Description: A convenient one-pot C-H alkenylation/electrocyclization/aromatization sequence has been developed for the synthesis of highly substituted pyridine derivatives from alkynes and {alpha},{beta}-unsaturated N-benzyl aldimines and ketimines that proceeds through dihydropyridine intermediates. A new class of ligands for C-H activation was developed, providing broader scope for the alkenylation step than could be achieved with previously reported ligands. Substantial information was obtained about the mechanism of the reaction. This included the isolation of a C-H activated complex and its structure determination by X-ray analysis; in addition, kinetic simulations using the Copasi software were employed to determine rate constants for this transformation, implicating facile C-H oxidative addition and slow reductive elimination steps.
Date: November 20, 2007
Creator: Ellman, Jonathan A.; Colby, Denise & Bergman, Robert
Partner: UNT Libraries Government Documents Department

Large Friction Anisotropy of a Polydiacetylene Monolayer

Description: Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties.
Date: May 11, 1999
Creator: Burns, A.R.; Carpick, R.W. & Sasaki, D.Y.
Partner: UNT Libraries Government Documents Department

Organogermanium Chemistry: Germacyclobutanes and digermane Additions to Acetylenes

Description: This dissertation comprises two main research projects. The first project, presented in Chapter 1, involves the synthesis and thermochemistry of germacyclobutanes (germetanes). Four new germetanes (spirodigermetane, diallylgermetane, dichlorogermetane, and germacyclobutane) have been synthesized using a modified di-Grignard synthesis. Diallylgermetane is shown to be a useful starting material for obtaining other germetanes, particularly the parent germetane, germacyclobutane. The gas-phase thermochemistries of spirodigermetane, diallylgermetane and germacyclobutane have been explored via pulsed stirred-flow reactor (SFR) studies, showing remarkable differences in decomposition, depending on the substitution at the germanium atom. The second project investigates the thermochemical, photochemical, and catalytic additions of several digermanes to acetylenes. The first examples of thermo- and photochemical additions of Ge-Ge bonds to C{triple_bond}C are demonstrated. Mechanistic investigations are described and comparisons are made to analogous disilane addition reactions, previously studied in their group.
Date: December 12, 2003
Creator: Chubb, Andrew Michael
Partner: UNT Libraries Government Documents Department

The Reactivity Patterns of Low-Coordinate Iron-Hydride Complexes

Description: This article discusses the reactivity patterns of low-coordinate iron-hydride complexes. The authors report a survey of the reactivity of the first isolable iron-hydride complexes with a coordiination number less than 5.
Date: April 30, 2008
Creator: Yu, Ying; Sadique, Azwana R.; Smith, Jeremy M.; Dugan, Thomas R.; Cowley, Ryan E.; Brennessel, William W. et al.
Partner: UNT College of Arts and Sciences

Hydrogen gas getters: Susceptibility to poisoning

Description: About 40% ({approximately}9,000) of the {approximately}23,000 transuranic (TRU) waste drums at Los Alamos National Laboratory (LANL) are presently unshippable because conservative calculations suggest that the hydrogen concentration may exceed the lower explosive limit for hydrogen. This situation extends across nearly all DOE sites holding and generating TRU waste. The incorporation of a hydrogen getter such as DEB into the waste drums (or the TRUPACT II shipping containers) could substantially mitigate the explosion risk. The result would be to increase the number of drums that qualify for transportation to the Waste Isolation Pilot Plant (WIPP) without having to resort to expensive re-packaging or waste treatment technologies. However, before this approach can be implemented, key technical questions must be answered. Foremost among these is the question of whether the presence of other chemical vapors and gases in the drum might poison the catalytic reaction between hydrogen and DEB. This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project was to obtain fundamental information on the chemical mechanism of the catalytic reaction of hydrogen with one commonly used hydrogen getter, DEB. Experiments with these materials showed that the method of exposure affects the nature of the reaction products. The results of this work contributed to the development of a mechanistic model of the reaction.
Date: December 31, 1998
Creator: Mroz, E.J.; Dye, R.C.; Duke, J.R. & Weinrach, J.
Partner: UNT Libraries Government Documents Department

Draft test plan for hydrogen getters project

Description: Hydrogen levels in many transuranic (TRU) waste drums are above the compliance threshold, therefore deeming the drums non-shippable to the Waste Isolation Pilot Plant (WIPP). Hydrogen getters (alkynes and dialkynes) are known to react irreversibly with hydrogen in the presence of certain catalysts. The primary purpose of this investigation is to ascertain the effectiveness of a hydrogen getter in an environment that contains gaseous compounds commonly found in the headspace of drums containing TRU waste. It is not known whether the volatile organic compounds (VOCs) commonly found in the headspace of TRU waste drums will inhibit (poison) the effectiveness of the hydrogen getter. The results of this study will be used to assess the feasibility of a hydrogen-getter system, which is capable of removing hydrogen from the payload containers or the Transuranic Package Transporter-II (TRUPACT-II) inner containment vessel to increase the quantity of TRU waste that can be shipped to the WIPP.
Date: April 1, 1998
Creator: Mroz, G. & Weinrach, J.
Partner: UNT Libraries Government Documents Department

Metallacumulenes and carbide complexes. Final performance report

Description: We investigated many aspects of transition metal complexes of carbon-rich ligands, including cumulated transition metal carbene complexes of the types vinylidene (M=C=CR{sub 2})(M = Fe, Ru, Os, Mo, W), allenylidene (M=C=C=CR{sub 2}), and butatrienylidene (M=C=C=CR{sub 2}), as well as ``naked`` carbon ligands C{sub 1}, C{sub 2}, and C{sub 3}. In the last 3 years, we began to put some effort into studying the fullerenes. Finally, we investigated initial aspects of the coordination chemistry of thiophenes, from the perspectives of (1) modeling the transition- metal-catalyzed hydrodesulfurization of fossil fuels and (2) development of metal-doped, polythiophene-based polymers.
Date: December 31, 1992
Creator: Selegue, J.P.
Partner: UNT Libraries Government Documents Department

Energy randomisation. How much of rotational phase space is explored? How long does it take?

Description: In applying modern theories (RRKM) of unimolecular reaction, it is necessary to decide the volume of phase space in which the energy is assumed to be randomized. The question of whether the K rotational quantum number is conserved impacts on that choice. The conceptual sequence from experimental spectra, through analysis, and interpretation in terms of K relaxation is described for ethanol and 1-butyne in the 3 micron region. The interpretation of molecular eigenstate spectra involves identification of the bright state from the coherent excitation of part of the spectrum, evaluation of the rate of energy transfer out of the bright state, deducing the mechanism of the coupling of the bright state to the bath states, and modeling the spectra in order to determine the average coupling parameters for anharmonic coupling and Coriolis interactions.
Date: December 1995
Creator: Perry, D. S.; Bethardy, G. A.; Davis, M. J. & Go, J.
Partner: UNT Libraries Government Documents Department

Ligand intermediates in metal-catalyzed reactions; Annual technical report, August 1, 1992--August 1, 1993

Description: Achievements are reported for the following 4 areas: {pi}/{sigma} equillibria in aldehyde and ketone complexes; thermodynamic ligand binding affinities ({alpha},{beta} unsaturated organic carbonyl compounds); (a new form of coordinated carbon) an unsupported C{sub 3} chain that spans two different transition metals; and (a new form of coordinated carbon) an C{sub 3} chain that is anchored by a metal on each end and spanned by a third.
Date: August 10, 1993
Creator: Gladysz, J.A.
Partner: UNT Libraries Government Documents Department

Further studies on hydration of alkynes by the PtCl4-CO catalyst

Description: Under CO atmosphere, between 80 and 120 C, a glyme solution of PtCl{sub 4} forms a carbonyl compound that promotes hydration of internal as well as terminal alkynes to give aldehyde-free ketones. The catalytic process depends strongly on the electronic and steric nature of the substrates. Part of the carbonyl functions of the catalyst can be replaced by phosphine ligands. Chiral DIOP reacts with the PtCl{sub 4}-CO compound to give a catalyst that promotes partial kinetic resolution of a racemic alkyne. Replacement of part of the CO by polystyrene-bound diphenylphosphine enables to attach the catalyst to the polymeric support. Upon entrapment of the platinum compound in a silica sol-gel matrix, it reacts as a partially recyclable catalyst. A reformulated mechanism for the PdCl{sub 4}-CO catalyzed hydration is suggested on the basis of the present study.
Date: January 18, 2002
Creator: Israelsohn, Osnat; Vollhardt, K. Peter C. & Blum, Jochanan
Partner: UNT Libraries Government Documents Department

Subgap absorption in conjugated polymers

Description: Along with X{sup (3)}, the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of < 10{sup {minus}5}, Photothermal Deflection Spectroscopy (PDS) is ideal for determining the absorption coefficients of thin films of transparent'' materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination. 11 refs., 4 figs.
Date: January 1, 1991
Creator: Sinclair, M.; Seager, C.H. (Sandia National Labs., Albuquerque, NM (USA)); McBranch, D.; Heeger, A.J. (California Univ., Santa Barbara, CA (USA)) & Baker, G.L. (Bell Communications Research, Inc., Red Bank, NJ (USA))
Partner: UNT Libraries Government Documents Department

Photomodulation spectroscopy of photocarrier dynamics, electronic defects and morphology of conducting polymers. Progress report

Description: This is a progress report on the second period of activities associated with the DOE grant to the Physics Department of the University of Utah, starting on April 1st, 1991, on photocarrier dynamics, electronic defects and morphology of conducting polymers using the photomodulation spectroscopy. During the second period of this grant we have achieved impressive results and have started new studies, to be completed during the grant continuation period of the third year. We will describe our progress according to the material studied, since this is the best method to summarize our accomplishments. We have used a variety of techniques in our studies such as: CW photomodulation, photomodulation in the femtosecond and picosecond time ranges, CW resonant Raman scattering, transient photoinduced Raman scattering, electro-absorption, degenerate four-wave mixing and the newly technique of spin dependent photomodulation. These techniques have been used to obtain the transient electronic response of the studied conducing polymers.
Date: October 8, 1991
Creator: Vardeny, Z. V.
Partner: UNT Libraries Government Documents Department

The Stereoselective Formation of Bicyclic Enamines with Bridgehead Unsaturation via Tandem C-H Bond Activation/Alkenylation/Electrocyclization

Description: Rhodium-catalyzed intermolecular C-H activation of {alpha}, {beta}-unsaturated imines in the presence of alkynes leads to a tandem process in which coupling to the alkyne occurs at the {beta}-C-H bond of the imine, followed by electrocyclization of the resulting azatriene intermediates to give dihydropyridines (eq 1). Consideration of the intramolecular version of this overall transformation (Scheme 1) raises interesting regiochemical issues. For example in a compound such as 1, where the nitrogen and alkyne are connected by a 4-carbon tether, the presumed first-formed hydrido(vinyl)rhodium function can add to the triple bond in a 1,2-fashion, producing complex 2 with a new endocyclic double bond. Alternatively, addition might occur in a 2,1-fashion, leading to product 4 with an exocyclic double bond. We now wish to report that this intramolecular cyclization occurs smoothly at 100 C, and the exocyclic double bond route is exclusively followed. Remarkably, products such as 4 do not resist further cyclization. Even though both the transition state for this process and the resulting product are presumably strained, the overall transformation leads to good yields of unusual bridgehead doubly-bonded enamines such as 5. The unique chemistry of conjugated enamine 5 is consistent with the increased strain of this molecule as well as with inhibited conjugation between the nitrogen lone pair and the adjacent double bond (vida infra). We began our investigation into the C-H activation/cyclization of alkyne-tethered imine 1 by extensive screening of transition metal catalysts for this process. Rhodium-based catalysts were found to be the most efficient (Table 1), leading exclusively to the bridgehead dienamine; none of the catalysts that were employed in the screening led to quinolizidine 3 or to the product of intramolecular Diels-Alder reaction. The optimized reaction conditions employ the electron-rich monophosphine ligand (p-NMe{sub 2})PhPEt{sub 2} in 1:1 ratio relative to the metal (entry 6). Other phosphine ...
Date: December 10, 2007
Creator: Ellman, Jonathan A.; Yotphan, Sirilata & Bergman, Robert
Partner: UNT Libraries Government Documents Department

DHS Summer Student Project Report

Description: Tetanus and botulinum neurotoxins are among the most potent toxins known to man (Montecucco et al. al., 1995). Produced by the Clostridium tetani and Clostridium botulinum bacteria, respectively, these toxins concentrate in presynaptic axons and inhibit the release of neurotransmitters leading to paralysis and possibly death. Due to the potency of this lethal class of neurotoxins, we have undertaken a project to develop high affinity ligands that specifically bind to these toxins. Such compounds can have significant implications in both the design of detection systems to monitor for the possible release of these neurotoxins into the public and also the design of possible therapeutics to treat individuals exposed to tetanus or botulinum neurotoxins. The Clostridial neurotoxins are synthesized as 150 kDa proteins that are post-translationally cleaved into N- and C-terminal fragments held together by a single disulfide bond. The tetanus C-terminal fragment (TetC) has been shown to bind specifically to gangliosides present on the neuronal membrane surface and facilitate endocytosis of the toxin (Morris et al., 1980). Once the toxin is internalized in a membrane-bound vesicle, the light chain (N-terminal fragment) translocates to the cytosol where it interferes with neurotransmitter release. Previous work has demonstrated that various small molecule and peptide-based compounds bind to TetC, albeit in different locations. Among these molecules are the anticancer agent doxorubicin (Dox) and the tripeptides WEY and YEW (Figure 1; Cosman et al. al., 2002). The crystal structure of botulinum toxin and Dox (PDB code: 1I1E) demonstrates that Dox binds in a surface groove of in C-terminal fragment that is conserved in both botulinum and tetanus toxins. Similarly, YEW has been shown to bind to a second binding site that is highly conserved and also relatively close to the binding site of Dox. Thus, in our quest to design and synthesize high affinity ligands, ...
Date: August 19, 2005
Creator: Kawamoto, S
Partner: UNT Libraries Government Documents Department

Mixed aromatic-alkyne system on Pd surface - a first principles study

Description: Chemistry of mixed aromatic-alkyne systems on a metal surface is of general interest in many industrial processes. We use Density Functional Theory (DFT) to investigate the chemistry of one such system, i.e., 1,4-diphenyl-butadiyne, or DPB, in contact with Pd (110) and (111) surfaces. Reaction pathways and energetics of important processes are explored, including H{sub 2} adsorption, dissociation and migration on the metal surface, DPB-metal interaction, the energetics of H uptake, and the effects of impurities like CO and CO{sub 2} on H chemistry. We find that: (1) strong aromatic-metal interaction leads to significant binding strength of DPB molecule to both Pd surfaces, especially the (110); (2) H{sub 2} molecule readily dissociates on the Pd surface into H-radicals, which get taken up by alkyne triple bonds; (3) CO has strong binding to the metal surface, but interacts weakly with H radicals; (4) CO{sub 2} binds weakly to the metal surface, but could potentially lead to interesting chemical reactions with H.
Date: May 10, 2005
Creator: Maiti, A; Gee, R; Maxwell, R & Saab, A
Partner: UNT Libraries Government Documents Department

Harnessing the Chemistry of CO2

Description: Our research program is broadly focused on activating CO{sub 2} through the use of organic and organometallic based catalysts. Some of our methods have centered on annulation reactions of unsaturated hydrocarbons (and carbonyl substrates) to provide a diverse array of carbocycles and heterocycles. We use a combination of catalyst discovery and optimization in conjunction with classical physical organic chemistry to elucidate the key mechanistic features of the cycloaddition reactions such that the next big advances in catalyst development can be made. Key to all of our cycloaddition reactions is the use of a sterically hindered, electron donating N heterocyclic carbene (NHC) ligand, namely IPr (or SIPr), in conjunction with a low valent nickel pre-catalyst. The efficacy of this ligand is two-fold: (1) the high {delta}-donating ability of the NHC increases the nucleophilicity of the metal center which thereby facilitates interaction with the electrophilic carbonyl and (2) the steric hindrance prevents an otherwise competitive side reaction involving only the alkyne substrate. Such a system has allowed for the facile cycloaddition to prepare highly functionalized pyrones, pyridones, pyrans, as well as novel carbocycles. Importantly, all reactions proceed under extremely mild conditions (room temperature, atmospheric pressures, and short reaction times), require only catalytic amounts of Ni/NHC and readily available starting materials, and afford annulated products in excellent yields. Our current focus revolves around understanding the fundamental processes that govern these cycloadditions such that the next big advance in the cyclization chemistry of CO{sub 2} can be made. Concurrent to our annulation chemistry is our investigation of the potential for imidazolylidenes to function as thermally-actuated CO{sub 2} sequestering and delivery agents.
Date: May 11, 2010
Creator: Louie, Janis
Partner: UNT Libraries Government Documents Department

New Palladium-Catalyzed Approaches to Heterocycles and Carbocycles

Description: The tert-butylimines of o-(1-alkynyl)benzaldehydes and analogous pyridinecarbaldehydes have been cyclized under very mild reaction conditions in the presence of I{sub 2}, ICl, PhSeCl, PhSCl and p-O{sub 2}NC{sub 6}H{sub 4}SCl to give the corresponding halogen-, selenium- and sulfur-containing disubstituted isoquinolines and naphthyridines, respectively. Monosubstituted isoquinolines and naphthyridines have been synthesized by the metal-catalyzed ring closure of these same iminoalkynes. This methodology accommodates a variety of iminoalkynes and affords the anticipated heterocycles in moderate to excellent yields. The Pd(II)-catalyzed cyclization of 2-(1-alkynyl)arylaldimines in the presence of various alkenes provides an efficient way to synthesize a variety of 4-(1-alkenyl)-3-arylisoquinolines in moderate to excellent yields. The introduction of an ortho-methoxy group on the arylaldimine promotes the Pd-catalyzed cyclization and stabilizes the resulting Pd(II) intermediate, improving the yields of the isoquinoline products. Highly substituted naphthalenes have been synthesized by the palladium-catalyzed annulation of a variety of internal alkynes, in which two new carbon-carbon bonds are formed in a single step under relatively mild reaction conditions. This method has also been used to synthesize carbazoles, although a higher reaction temperature is necessary. The process involves arylpalladation of the alkyne, followed by intramolecular Heck olefination and double bond isomerization. This method accommodates a variety of functional groups and affords the anticipated highly substituted naphthalenes and carbazoles in good to excellent yields. Novel palladium migratiodarylation methodology for the synthesis of complex fused polycycles has been developed, in which one or more sequential Pd-catalyzed intramolecular migration processes involving C-H activation are employed. The chemistry works best with electron-rich aromatics, which is in agreement with the idea that these palladium-catalyzed C-H activation reactions parallel electrophilic aromatic substitution. A relatively efficient synthesis of cyclopropanes has been developed using palladium-catalyzed C-H activation chemistry, in which two new carbon-carbon bonds are formed in a single step. This method involves the palladium-catalyzed activation of ...
Date: December 19, 2004
Creator: Huang, Qinhua
Partner: UNT Libraries Government Documents Department

Group 4 Metalloporphyrin diolato Complexes and Catalytic Application of Metalloporphyrins and Related Transition Metal Complexes

Description: In this work, the first examples of group 4 metalloporphyrin 1,2-diolato complexes were synthesized through a number of strategies. In general, treatment of imido metalloporphyrin complexes, (TTP)M=NR, (M = Ti, Zr, Hf), with vicinal diols led to the formation of a series of diolato complexes. Alternatively, the chelating pinacolate complexes could be prepared by metathesis of (TTP)MCl{sub 2} (M = Ti, Hf) with disodium pinacolate. These complexes were found to undergo C-C cleavage reactions to produce organic carbonyl compounds. For titanium porphyrins, treatment of a titanium(II) alkyne adduct, (TTP)Ti({eta}{sup 2}-PhC{triple_bond}CPh), with aromatic aldehydes or aryl ketones resulted in reductive coupling of the carbonyl groups to produce the corresponding diolato complexes. Aliphatic aldehydes or ketones were not reactive towards (TTP)Ti({eta}{sup 2}-PhC{triple_bond}CPh). However, these carbonyl compounds could be incorporated into a diolato complex on reaction with a reactive precursor, (TTP)Ti[O(Ph){sub 2}C(Ph){sub 2}O] to provide unsymmetrical diolato complexes via cross coupling reactions. In addition, an enediolato complex (TTP)Ti(OCPhCPhO) was obtained from the reaction of (TTP)Ti({eta}{sup 2}-PhC{triple_bond}CPh) with benzoin. Titanium porphyrin diolato complexes were found to be intermediates in the (TTP)Ti=O-catalyzed cleavage reactions of vicinal diols, in which atmospheric oxygen was the oxidant. Furthermore, (TTP)Ti=O was capable of catalyzing the oxidation of benzyl alcohol and {alpha}-hydroxy ketones to benzaldehyde and {alpha}-diketones, respectively. Other high valent metalloporphyrin complexes also can catalyze the oxidative diol cleavage and the benzyl alcohol oxidation reactions with dioxygen. A comparison of Ti(IV) and Sn(IV) porphyrin chemistry was undertaken. While chelated diolato complexes were invariably obtained for titanium porphyrins on treatment with 1,2-diols, the reaction of vicinal diols with tin porphyrins gave a number of products, including mono-, bis-alkoxo, and chelating diolato complexes, depending on the identity of diols and the stoichiometry employed. It was also found that tin porphyrin complexes promoted the oxidative cleavage of vicinal diols and the oxidation ...
Date: December 19, 2004
Creator: Du, Guodong
Partner: UNT Libraries Government Documents Department

Catalytic Hydration of Alkenes and Alkynes

Description: The fifteen years of DOE support have encompassed two different projects, electron-transfer reactions of metal carbonyl anions and water-soluble organometallic complexes. Each of these is related to homogeneous catalysis and will be described in separate sections. Electron Transfer--Twenty-one manuscripts resulted from our studies of electron-transfer reactions of metal carbonyl anions and acknowledge DOE support. Construction of an infrared stopped-flow system allowed us to measure rates of reactions for the extremely air-sensitive metal carbonyl anions. As for carbanions, both one-electron and two-electron processes occur for metal carbonyl anions. The most unexpected feature was examples of a very rapid two-electron process, followed by a much slower one-electron back transfer. The two-electron processes were accompanied by transfer of a ligand between two metals, M-X + M{prime}{sup -} {yields} M{sup -} + M{prime}-X with X groups of CO{sup 2}, H{sup +}, CH{sub 3}{sup +} and Br{sup +}. These transfers, which can be considered nucleophilic displacements, occurred when M{prime}{sup -} was more nucleophilic than M{sup -}. The 21 published manuscripts explore one- and two-electron processes for many such organometallic complexes. Water-Soluble Organometallic Complexes--The potential of water-soluble organometallic complexes in ''green chemistry'' intrigued us. Sixteen manuscripts acknowledging DOE support have appeared thus far in this field. Our research centered on sulfonated phosphine ligands, PPh{sub 2}(m-C{sub 6}H{sub 4}SO{sub 3}Na) and P(m-C{sub 6}H{sub 4}SO{sub 3}Na){sub 3}, to solubilize organometallic complexes in water. These analogues of PPH{sub 3} allowed us to synthesize complexes of Ir, Rh, Ru, Ni, Pd, Pt and Ag that are water-soluble and contain such common organometallic ligands as CO, H and CH{sub 3} in addition to halides and the phosphine ligands. These metal complexes show the ability to activate H{sub 2}, CO, C{sub 2}H{sub 4}, H{sub 2}O, SO{sub 2} etc. in aqueous solution. The primary conclusion is that water-soluble organometallic complexes can be prepared and ...
Date: March 18, 2003
Creator: Atwood, Jim D.
Partner: UNT Libraries Government Documents Department

Controlled synthesis of polyenes by catalytic methods. Progress report, December 1, 1989--November 30, 1992

Description: A more direct approach to polyenes by the direct polymerization of acetylenes has been achieved. We were able to show that polymerization of acetylene itself can be controlled with a well- characterized alkylidene catalyst, but only if a base such as quinuclidine is present in order to slow down the rate of propagation relative to initiation. (Quinuclidine may also stabilize vinylalkylidene intermediates formed in the reaction). Unfortunately, ``living polyenes`` were no more stable than isolated polyenes, and so this approach had its limitations. Direct polymerization of acetylene by Mo(CH-t-Bu)(NAr)(O-t-Bu){sub 2} was more successful, but inherent polyene instability was still a problem. The most important result of the past grant period is the finding that dipropargyl derivatives (HC=CCH{sub 2}XCH{sub 2}C=CH; X = CH{sub 2}, C(CO{sub 2}R){sub 2}, SiR{sub 2}, etc.), which have been reported to be cyclopolymerized by various classical catalysts by as yet unknown mechanisms, are polymerized by Mo(CH-t-Bu)(NAr)[OCMe(CF{sub 3}){sub 2}]{sub 2} in dimethoxyethane. We speculate that intramolecular formation of a five-membered ring in the product of {alpha} addition is fast enough to yield another terminal alkylidene on the time scale of the polymerization reaction, while a six-membered ring is formed in a reaction involving a more reaction terminal alkylidene. Either intermediate alkylidene, but most likely the terminal alkylidene, could react with additional monomer to lead to growth of a chain having ``dangling`` triple bonds that eventually could be employed to form crosslinks.
Date: July 1, 1992
Creator: Schrock, R. R.
Partner: UNT Libraries Government Documents Department

An alkyne metathesis-based route toortho-dehydrobenzannulenes

Description: An application of alkyne metathesis to 1,2-di(prop-1-ynyl)arenes, producing dehydrobenzannulenes, is described. An efficient method for selective Sonogashira couplings of bromoiodoarenes under conditions of microwave irradiation is also reported.
Date: November 7, 2002
Creator: Miljanic, Ognjen S.; Vollhardt, Peter C. & Whitener, Glenn D.
Partner: UNT Libraries Government Documents Department