Browsing by Subject "Phosphorus compounds"
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Item Contributions to the chemistry of the group V-group V bond(Texas Tech University, 1982-12) Avens, Larry RossNot availableItem Lewis acid-base exchange reactions of polypnicogens(Texas Tech University, 1984-12) Cribbs, Leonard VThe 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.Item Some chemistry of phosphorus-phosphorous bonds(Texas Tech University, 1980-08) Wolcott, Richard AlanNot availableItem Studies of trialkylphosphine-carbon disulfide adducts and chalcogenide phosphorus cages(Texas Tech University, 1989-05) Ettel, Mary L.Item Synthesis and characterization of group 13 & 15 complexes supported by N,N'-bidentate ligands(2007-12) Lu, Zheng, 1973-; Cowley, Alan H.The first example of an N,N'-chelated [beta]-diketiminato phosphenium salt has been isolated by careful tuning of both the ligand architecture and the electronic characteristics of the phosphorus containing moiety. Using a two-electron reduction approach, the first example of a phosphinidene valence isomer has been isolated and structurally characterized. The mechanism of formation of this valence isomer was elucidated via Density Functional Theory (DFT) calculations. These calculations revealed that the formation of this valence isomer involves the intermediacy of a triplet diradical. In turn, the triplet diradical decays by two further steps to generate the observed product. A cationic phosphinous acid has been prepared via the hydrolysis of a cationic phosphenium complex in basic solution. DFT calculations reveals that the introduction of a positive charge stabilizes the phosphinous acid form. Two N,C-bonded phosphenium cation salts have also been obtained, the crystal structures of which reveal that the formation of these compounds involves C-H activation of a methyl group on the [beta]-diketiminate ligand. Three synthetic methods, namely halide abstraction, aluminum/boron halide exchange process and salt metathesis, have been explored for the preparation of boron cations supported by [beta]-diketiminate ligands. The first structurally characterized boron cation supported by a [beta]-diketiminate ligand has been isolated as its [Al₂Cl₇]⁻ salt. A Ga-Fe organometallic complex supported by a [beta]-diketiminate ligand has also been synthesized via salt metathesis reaction and fully characterized. Finally, several bisamidinate supported boron complexes have been synthesized and structurally characterized. Such complexes may have applications as bifunctional catalysts or as building blocks for novel polymers.