Browsing by Subject "Phosphine"

Now showing 1 - 6 of 6
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    An infrared study of solid phosphine.
    (Texas Tech University, 1975-08) Covington, Billy Charles
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    Contributions to the chemistry of the group V-group V bond
    (Texas Tech University, 1982-12) Avens, Larry Ross
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    Lewis acid-base exchange reactions of polypnicogens
    (Texas Tech University, 1984-12) Cribbs, Leonard V
    The insertion of a perfluoroalkylphosphinidene moiety RfP from perfluoroalkyclcycloplyphosphines (RfP)n into the pnicogen-pnicogen bond of tetraalkyl dipnicogens appears to be general. Thus, a CFo unit from (CFoP)/ c reacts with R2P-PR2 (where R = Me, Et, Bu) to form the tripnicogen compounds R2P-P(CF3)-PR-2. These tripnicogens undergo neutral water hydrolysis surprisingly easily to form chiral dipnicogens. For example, Me2P-P(CF3)-PMe2 hydrolyzes immediately at ambient temperature with an equimolar quantity of water to yield the new chiral secondary phosphine Me2P-P(CF3)H plus Me2P(O)OH and Me2PH. A second equivalent of water hydrolyzes the dipnicogens to the primary perfluoroalkylphosphine. To further investigate the generality of the "insertion" reaction, cyclic polyarsines were studied to ascertain the possibility of (RfAs)n or (RAs)n providing a source of the arsinidene species RfAs or RAs. Addition of an equimolar quantity of Me2As-AsMe2 to (CF3As)4,5 in C6D6 does form the tripnictide Me2As-As(CF3)-AsMe2. The reaction of a secondary alkyl or aryl phosphine or arsine with the cyclic polyphosphine (CF3P)4,5 or cyclic polyarsine (CF3As)4,5 produces the chiral dipnictides of the type R2E-E(CF3)H, E = P or As. In addition, a number of other products are produced in a complex equilibrium mixture. The origin of the complex equilibrium has been studied by examining the reaction of pairs of reactants and/or products and a reaction mechanism has been deduced. Exchange reactions of the pnicogen-pnicogen bond have also been investigated. Thus, unsymmetrical diphosphines of the type R2P-PR2 typically disproportionate to form the symmetrical species R2P-PR2 and R2P-PR2. However, an exception to this behavior is noted when the relative basicities of the two pnicogen atoms in a dipnicogen differ dramatically. Generality of the Lewis Acid-Base exchange reactions was observed by studying molecules in which P-P bond breakage of the diphosphine was associated with scission of a P-P, P-H, and/or P-X bond in the second reactant. In all cases studied in which reaction occurred, product formation could be explained as proceeding through a four-centered intermediate in which nucleophilic attack by a relatively basic pnicogen atom occurs on a relatively acidic pnicogen atom. A variety of di- and tripnictides were prepared by this method and their NMR parameters determined.
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    Proton-capped tripod triphosphines and their oxides and sulfides: synthesis and characterization
    (Texas Tech University, 1993-12) De Marquis, Virginia K.
    During the Cold War, the main focus of the United States was to develop nuclear technology as quickly as possible in order to maintain its status as the world's leading Super Power. One of the consequences of this extremely focused effort was that very little thought was given to responsible waste disposal. At that time, development and production was so important that everything else held a much lower priority. However, since the end of the Cold War, priorities have shifted from improving and stockpiling nuclear weapons to reducing the existing stockpile and remediating sites that were contaminated during the development and production process. With this new agenda comes the need for inexpensive and efficient waste disposal methods.
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    Rh-catalyzed reductive coupling under hydrogenation conditions and nucleophilic catalysis via phosphine conjugate addition
    (2007) Kong, Jongrock, 1972-; Krische, Michael J.
    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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    The development of metal-organic frameworks using palladium metal complexes for catalysis and the utilization of a dihaloimidazolidinedione for easy acid chloride generation
    (2016-08) Nguyen, An Ngoc-Michael; Humphrey, Simon M.; Jones, Richard A
    Part 1. Metal-Organic Frameworks (MOFs) have been extensively studied due to their functional versatility and well-defined, porous structures. It is, however, exceptionally rare to find MOFs that use late transition metal complexes as a building block. Incorporation of these complexes would have immediate applications in catalysis and enhanced gas adsorption/storage. Furthermore, because of the MOF’s well-defined structures, heterogeneous catalysis properties can be more readily studied and improved. Herein, 1,2-bis(bi(para-carboxyl)phenylphosphino)benzene palladium dichlo-ride’s (PdCl2(BBCB)) catalytic ability is studied using the Mizoroki-Heck reaction, and 1,2-bis(bi(4-carboxy-biphenyl-4’-phosphino))ethane palladium dichloride (PdCl2(BBCE-1L)) is used to make a MOF with an enlarged pore size and greater catalytic ability. BBCB, a tetra-para-carboxylic acid derivative of dppb, is used to form a palladium dichloride bis(phosphine) complex. This complex was found to perform a Mizoroki-Heck reaction in decent yields despite formation of palladium black. BBCE-1L, a tetra-4-carboxylic acid biphenyl derivative of dppe, was then developed to deter palladium black formation and enlarge the pore size of the MOF. A MOF was made using a Zn(II) paddlewheel as the metal node and PdCl2(BBCE-1L) as the organic linker. This MOF was found to have moderate thermal stability and potentially high pore volume. Part 2. Acid chloride generation is a widely researched field for the synthesis of amides and esters, motifs found throughout nature and pharmaceuticals. Recently, we found that dihaloimidazolidinediones could substitute a variety of alcohols with halogens through an amide-stabilized carbocation. As an extension of this chemistry, we were able to activate most carboxylic acids into the corresponding acid chloride with near quantitative yields. Mechanistic studies of electronic and steric effects suggest that the rate-determining step is the nucleophilic attack of a free chloride ion on the carbonyl center to produce the corresponding acid chloride. Electronic effects of ring size on electrophilicity was also observed and explained through analysis of a simplified Walsh diagram.