Elizabeth Gebert

Dimeric structure of di-tert-butylphosphinic acid

The molecular structure of di-tert-butylphosphinic acid, ((CH/sub 3/)/sub 3/C)/sub 2/PO(OH), as determined by single-crystal x-ray methods, is the first observed distinct dimeric R/sub 2/PO(OH) compound with two acid molecules linked through a centrosymmetric configuration. The molecule crystallizes in the monoclinic space group, P2/sub 1//c with cell parameters a = 8.973 (6) A, b = 13.130 (9) A, c = 10.539 (7) A, ..beta.. = 117.95 (3)/sup 0/, and Z = 4. The structure was solved and refined using 999 independent three-dimensional Mo K..cap alpha.. x-ray data collected with an automated diffractometer. Full-matrix least-squares refinement of 620 observations for which F/sub 0/ > 3 sigma (F/sub 0/) led to R/sub F/ = 0.059. The discrete dimer which was found contains strong, 2.506 (18) A, hydrogen bonds, in which the oxygen atoms of O--H--O are not related by a crystallographic symmetry element. The eight-membered, hydrogen bonded ring has 1 site symmetry and shows a small chair-conformation distortion from planarity. The P--O bond lengths are 1.521 (8) and 1.520 (6) A which indicates that the oxygen atoms are essentially equivalent. There appear to be weak C--H--O interactions which fix the methyl group orientations to give an overall eclipsed conformation.

The crystal structure of lithium uranate

Abstract Lithium uranate, Li2UO4, crystallizes in an orthorhombic unit cell, space group, Pnma(D2h16, No. 62) with a =10.547(3), b = 6.065(1), c = 5.134(1) A and Z = 4. Single crystal X-ray diffraction data complete to 2θ = 50° were collected on a Syntex P21, automated diffractometer. The structure was solved by a combination of Patterson, Fourier, and least-squares refinement techniques to an RF = 0.061 for 321 independent reflections. The structure consists of octahedrally coordinated U(VI) ions bonded to two crystallographically different primary oxygens at distances of 1.97(2) and 1.92(2) A and to four equivalent secondary oxygens at 2.19(1) A. Octahedrally coordinated Li(1) and tetrahedrally coordinated Li(2) form LiO bonds of lengths varying from 1.91(5) to 2.29(2) A.

Redetermination of the crystal structure of barium uranate

Abstract Barium uranate, BaUO4, crystallizes in the centro-symmetric orthorhombic space group, Pbcm (D2h11; No. 57) with a = 5.744(3), b = 8.136(4), c = 8.237(3) A for M = 439.36 and Z = 4 . X-ray diffraction data complete to 2θ = 60° (Mo Kα radiation) were collected using a G.E. XRD-490 automated diffractometer. The structure was solved by a combination of Patterson, Fourier and least-squares techniques. The final discrepancy indices are RF = 0.059 and wRF = 0.107 for 507 reflections where F0 > σ (F0). Distinct primary U-O bonds and polymeric secondary U-O bonds form a distorted octahedral U(VI) coordination sphere where the U-O bond distances are shown to be highly influenced by the Ba2+ ion. The apical primary uranium-oxygen bond length is 1.872(12) A while the basal secondary U-O bond distances are 2.196(6) and 2.223(6) A.

The crystal structure of cesium perbromate

The crystal structure of CsBrO4 was determined by single-crystal X-ray diffraction and found to be different from the structures of the lighter alkali perbromates. Cesium perbromate crystallizes in the tetragonal space group I41/a, with unit cell constants of a = 5.751(4)A and c = 14.821(12)A. Full-matrix least-squares analyses indicate that tetrahedral perbromate ions are situated in the lattice so that all corresponding tetrahedral faces are parallel. The observed BrO distance is 1.591(6) A. The Cs+ ions reside in twelve coordinate positions with CsO distances of 3.146(7), 3.383(9), and 3.389(9) A. This unique stucture causes CsBrO4 crystals to have noticeable plasticity.

Di-ϱ-methylphenylphosphoric acid—The solid state structure of a unique dimeric hydrogen bonded phosphoric acid☆

Abstract Di-ϱ-methylphenylphosphoric acid, [ϱ-CH3C6H4O]2PO(OH), HD(ϱ-MΦ)P, is the first phosphoric acid dimer to be characterized in the solid state. Two acid molecules are linked together by strong, 2.512(3)A, apparently centered, hydrogen bonds forming an eight-membered centrosymmetric ring. This X-ray structural result parallels IR spectral data showing the disappearance of the P=O stretching absorptions due to the formation of a nearly centered hydrogen bond. The two OH distances in the hydrogen bond are O(1)-H(1)=1.28(5) and O(2)H(1)= 1.23(5)A with an O(1)H(1)O(2)′ bond angle of 172(4)°. HD(ϱ-MΦ)P crystallizes in the centrosymmetric, triclinic space group, P1−, [C1i, No. 2], with unit cell parameters a = 9.2700(17), b = 0.5384(14), c = 9.7308(15) A , α = 85.27(1), β = 62.34(1), γ = 65.53(1)°, γ = 65.63(1)° and Z = 2 . Data were collected using a Syntex P21 automated diffractometer and the structure was solved by using a combination of direct methods, Fourier and least-squares refinement techniques to a final RF = 0.040 for all 1408 independent data. The PO bond lengths observed are: 1.489(2), 1.501(2), 1.559(2) and 1.570(2)A.

Characterization of airborne particles at a high-btu coal-gasification pilot plant

Airborne particles in fugitive emissions have been measured at a slagging fixed-bed coal-gasification pilot plant using lignite. Sampling was conducted during shutdown operations and opening of the gasifier following an aborted startup. Aerosol collected with a Sierra high-volume impactor was subjected to analysis by gas chromatography, mass spectrometry, and scanning electron microscopy; aerosol collected with an Andersen low-volume impactor was subjected to flameless atomic absorption analysis. The data show that the bulk of the trace organic material is associated with small particles: these data are similar to data on ambient air reported in the literature. Particle morphologies resemble those of fly ash from coal combustion, including smooth spheres, vesicular spheres, and crystalline material. Trace element size distributions are bimodal and resemble data for ambient air. Pb-containing particles are generally submicron, while particles containing Al, Fe, and other crustal species are mostly of supermicron size. Aluminum-based aerosol enrichment factors calculated from the lignite composition show that the composition of the aerosol resembles that of the coal, with the exception of modest enrichments of Mg, Na, As, and Pb in the submicron size range. Aerosol enrichment factors based on the earths crustal composition are somewhat greater than those based on coal composition for several elements, suggesting potential errors in using crustal enrichment data to investigate chemical fractionation during aerosol formation.

Some ternary oxides of neptunium and plutonium with the alkali metals

Abstract Crystal data and thermal stabilities are reported for ternary oxides formed by potassium, rubidium and cesium with neptunium and plutonium(VI). The compounds characterized include M2NpO4, M2Np2O7 and M2PuO4 (where M = K, Rb and Cs), Cs4Np5O17 and Cs2Np3O10. A reinvestigation of the lithium-neptunium(VI) oxide system has demonstrated the existence of Li2NpO4.

The Structure and Magnetic and Electrical Conductivity Properties of the Charge Transfer Compound 1,1′-Dimethylferrocenium Bis-(Tetracyanoquinodimethane), [(CH3C5H4)2Fe][TCNQ]2

Metallocenes react with tetracyanoquinodimethane (TCNQ) to yield charge transfer compounds predominantly of the stoichiometry [metallocene][TCNQ] or [metallocene][TCNQ]2.1,2 The 1:2. compounds have relatively high electrical conductivities which range from 4 ohm-1cm-1 for [(C5H5)2Fe][TCNQ]2 to 0.03 ohm-1cm-1 for [(CH3C5H4)2Fe]-[TCNQ]2,1 but, up to now, difficulties in obtaining high quality single crystals have prevented structural determinations.