Kenneth V. Salazar

Crystal and molecular structure of tricyclopentadienyltetrahydrofuranuranium(III), (η5-C5H5)3U·OC4H8

Abstract Tricyclopentadienyltetrahydrofuranuranium(III), (η 5 -C 5 H 5 ) 3 U·OC 4 H 8 , crystallizes in the centrosymmetric monoclinic space group P2 1 / n with a 8.248(3), b 24.322(17), c 8.357(4) A, β 101.29(5)°, V 1644.0 A 3 and ρ(calc) 2.04 g cm −1 for Z = 4 and mol.wt. 595.0. Diffraction data (Mo-K α , 2θ(max) 45°) were collected on an Enraf-Nonius CAD4 diffractometer and the structure was refined to R w (F) 4.7% for those 1530 reflections having I > 2σ( I ). The molecule consists of a distorted tetrahedral arrangement of THF and (η 5 -C 5 H 5 ) ligands with CpUCp angles in the range 110.4–122.4° and CpUO angles between 90.2 and 106.0°. Individual uranium-carbon distances range from 2.76(2) to 2.82(2) A and average 2.79[1] A. The uranium-oxygen distance of 2.551(10) A suggests a 10-coordinate U 3+ radius of 1.20 A in this class of compounds.

Tetrahydroborate complexes of uranium: preparation and crystal structure of mixed-valent [Na(THF)6][C5Me5)U(BH4)3]2

Abstract Reaction of U(BH4)3·nTHF with Cp*2Th(PPh2)2 in a THF/toluene solution containing NaCl resulted in isolation of the novel tetrahydroborate complex [Na(THF)6][Cp*U(BH4)3]2, Cp*=C5Me5. The complex crystallizes in the space group P 1 with cell parameters of a=11.110(3), b=15.140(3), c= 17.856(3) A, α=88.27(1), β=74.49(2) and γ= 85.42(2)o, Z=2 and Dcalc=1.49 g/cm3. The unit cell contains two crystallographically independent uranium atoms in general positions, each coordinated by three tridentate, hydrogen-bridged BH4− groups and one η5-pentamethylcyclopentadienyl ligand. Two Na(THF)6+ cations, which occupy centers of crystallographic symmetry, complete the structure. Metrical parameters are not significantly different between the two independent uranium centers (av. UB distances 2.61 A) or the two independent sodium containing cations. Crystallographically independent Cp*U(BH4)3 moieties pack to form two separate chains parallel to the crystallographic a axis. The stoichiometry and accompanying black color for the crystal suggest a mixed-valent charge transfer compound for which the average uranium oxidation state is 3.5. An unexpected Cp* transfer from thorium to uranium is also noted in the reaction chemistry.

Catalytic reduction of sulfur dioxide

Many processes have been utilized with varying degrees of success for removal of sulfur dioxide from flue gases. Quite a few more have been proposed. One type of process that would appear quite attractive is the reduction of the SO/sub 2/ to sulfur. The present work was undertaken to examine the effect of using an extremely active hydrogenation catalyst to promote the reduction of SO/sub 2/ with H/sub 2/ at low enough temperatures such that H/sub 2/S formation could be minimized. Ruthenium on ..gamma..-alumina was examined and found to be quite active at temperatures as low as 150/sup 0/C. These results are discussed in this paper.

Hydrogen uptake on film surfaces produced by a unique codeposition process

Abstract Hydrogen uptake on several different film surfaces has been achieved by deposition of a conventional hydrogen gettering system via a novel combination of physical vapor deposition (PVD) and chemical vapor deposition (CVD) processes. We decided to use a conventional hydrogen gettering system, developed by Smith and Schicker [J.R. Schicker, AS/KCD Project No. EPN-047620, May 1994], that uses an acetylenic organic compound mixed with carbon supported palladium metal. The organic material, 1,4-bis-(phenylethynyl) benzene (DEB), is mixed with palladium and carbon by employing conventional solid state ceramic preparative techniques. Our novel codeposition process combines PVD and CVD techniques for fabricating thin-film coatings of the palladium-catalyzed DEB hydrogen gettering system. Hydrogen uptake was confirmed by 1 H NMR and our novel process lends itself well to placing hydrogen getter onto complex shapes and substrates of various compositions.

Progress Update on CVD of Beryllium

Abstract Capsules with beryllium ablators are very important targets for the DOE National Ignition Facility (NIF) laser in the Inertial Confinement Fusion Program. Two leading candidates for fabricating beryllium capsules are the machining and bonding of hemispheres, and physical vapor deposition of beryllium onto plastic or other shells. An attractive possibility would be to coat a spherical mandrel with a thin layer of beryllium by a non-line-of-sight process. This coating could be applied via the chemical vapor deposition (CVD) of beryllium. Our first attempt at coating beryllium via CVD was done by using bis(cyclopentadienyl)beryllium, (C5H5)2Be, as the precursor material. Results obtained by use of (C5H5)2Be as the precursor material is discussed. However, difficulties we encountered with use of the (C5H5)2Be precursor material led us to examine a relatively unexplored area of beryllium chemistry, namely that of its amines. This redirection also led us to change surrogate material for use in the developmental work.

Chemistry of M(allyl)3 (M = Rh, Ir) compounds: structural characterization of tris(allyl)iridium complexes with phosphorus ligands

While addition of phosphorus ligands such as P(OPh)3 to Rh(allyl)3 gives monovalent Rh(allyl)L2, the iridium analog gives stable mixed σ/π-tris(allyl) complexes, as evidenced by the structural characterization of mono-, bi-, and tri-dentate ligand complexes.

Improvement of luminescent properties of thin-film phosphors by excimer laser processing

Thin-films of europium doped yttrium oxide, (Y1-xEux)2O3, were deposited on sapphire substrates by metallorganic chemical vapor deposition. The films, -400 nm thick, were weakly luminescent in the as-deposited condition. A KrF laser was pulsed once on the surface of the films at a fluence level between 0.9 - 2.3 J/cm2. One pulse was sufficient to melt the film, which increased the photoluminescent emission intensity. Melting of a rough surface resulted in smoothing of the surface. The highest energy pulse resulted in a decrease in luminous intensity, presumably due to material removal. Computational modeling of the laser melting and ablation process predicted that a significant fraction of the film is removed by ablation at the highest fluence levels.

Tetrahydroborate complexes of uranium with 2-(diphenylphosphino)pyridine

U(BH4)3(THF)x, (THF = tetrahydrofuran,) and (η5-C5H5)UCl3 react with 2-(diphenylphosphino)pyridine, (Ph2Ppy), producing 1:2 and 1:1 adducts, respectively; and X-ray crystal structure of U(BH4)3(Ph2Ppy)2·1/2C6H6 shows U–P = 3.162(1) and U–N = 2.659(4)A.