Arthur H. Reis

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.

Sterically hindered solvent extractants—III: The molecular and crystal structure and heavy-element extraction properties of the di-t-pentylphosphinic acid dimer☆

Abstract Di-t-pentylphosphinic acid, [C(CH3)2(CH2CH3)]2PO(OH), H[Dt-PeP], has been shown by single-crystal X-ray diffraction data to be dimeric in the solid state. Previously, di-t-butylphosphinic acid, [C(CH3)3]2PO(OH), H[Dt-BP], was the only phosphinic acid known to be dimeric in the solid state. H[Dt-PeP] crystallizes in the centro-symmetric orthorhombic space group, Cmca, with unit cell parameters, a = 17.694(7), b = 11.021(4), and c = 13.073(5) A , and Z = 8 , indicating that the molecule must conform to a crystallographic mirror plane or 2-fold axis. A measured density of 1.088 g/cm3 is in good agreement with a calculated value of 1.074 g/cm3 for a unit cell volume of 2549.3 (A)3 and a formula weight of 206.25 g. A total of 646 three-dimensional X-ray data were collected on an automated XRD-490 G.E. diffractometer. The structure was solved using a combination of direct methods, Patterson, Fourier, and least-squares refinement techniques. Refinement of the data indicates that H[Dt-PeP] is dimeric, and contains a mirror plane in which the hydrogen-bonded, eight-membered ring lies. A structural disorder involving principally the ethylene carbon but affecting the methyl carbons as well precluded a precise determination of the carbon positions and severely reduced the precision of the final refinement. In the liquid-liquid extraction system consisting of a solution of H[Dt-PeP] in benzene vs an acidic aqueous chloride phase, the extraction of UO22+ follows the stoichiometry: UO2A2+ + 2(HY2O ⇆ UO2(HY2)2O + 2HA+ where (HY)2 represents the dimer of H[Dt-PeP] and A and O represent the mutually equilibrated aqueous and organic phases. The expression for the distribution ratio, k, for UO22+ is: k =KSF2/[H+]2, 1.0 F(NaCl+HCl) where F is the concentration in formality units of H[Dt-PeP] in the organic phase, [H+] is the molar concentration of H+ in the aqueous phase, and Ks is a constant characteristic of the system, i.e. benzene diluent, aqueous phase 1.0 F in chloride. The Ks value for UO22+ is 3 × 104. This value is 1.5 times that for the corresponding extraction of UO22+ by H[Dt-BP] reported elsewhere.

STRUCTURE AND OXIDATION STATES OF Ir AND Pt ONE-DIMENSIONAL INORGANIC COMPLEXES*

This paper reviews attempts to accurately characterize several anisotropically conducting inorganic complexes. Structural data are presented on K/sub 2/Pt(CN)/sub 4/.3H/sub 2/O, K/sub 1/ /sub 75/Pt(CN)/sub 4/.1.5H/sub 2/O, K/sub 1/ /sub 6/Pt(C/sub 2/O/sub 4/)/sub 2/.1.2H/sub 2/O, and Ir(CO)/sub 3/Cl. In this discussion, emphasis is placed on the relationship of the structural properties, metal-metal distance and ligand conformation, and the partial oxidation state of the metal. 31 references, 19 figures, 2 tables.

Crystal structure and molecular geometry of 7,8-µ-dimethylalumina-1,2-dicarba-nido-undecaborane(13), B9C2H12AlMe2, at –100 °c

The title compound, has been subjected to a low-temperature (–100 °C)X-ray diffraction study. The compound crystallizes in the non-centrosymmetric triclinic space group P1 (C11, No. 1) with a= 7·460(6), b= 6·462(7), c= 6·985(4)A, α= 115·37(5), β= 97·02(11), γ= 87·61(10)°, Z= 1. The structure was solved from photographic data by Fourier methods and refined by least-squares techniques to R 13·5% for 875 non-zero reflections. All non-hydrogen atoms were located. The B9C2H12 moiety is present as an icosahedral fragment with the AlMe2 group lying outside the cage and interacting with only two boron atoms.

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.

Structural studies on clathro-chelate complexes. Part III. Trigonal prismatic co-ordination of d7 cobalt(II) in orthorhombic crystalline [{FB(ONCHC5H3N)3P}CoII+][BF4–],MeCN and a single-crystal transformation of unsolvated monoclinic [{FB(ONCHC5H3N)3P}CoII+][BF4–]

{Fluoro-[6,6′,6″-phosphinidynetris-(pyridine-2-carbaldehyde oximato)(3–)]borato(1–)}cobalt(1+) tetrafluoro-borate-acetonitrile (I) crystallizes in the noncentrosymmetric space group Aba2 with a= 23·408(19), b= 17·494(15), c= 12·090(8)A, and Z= 8. A single-crystal X-ray diffraction study by Patterson and Fourier methods from diffractometer data has led to the location of all non-hydrogen atoms, with R 10·5% for 1126 independent non-zero reflections. The cation has approximate C3v symmetry, with the central CoII atom co-ordinated to six nitrogen atoms, mean Co–N(aldoximo) 2·063(18) and Co–N(pyridyl) 2·118(38) A. The co-ordination sphere of the cobalt(II) atom defines a slightly tapered trigonal prism, with N(aldoximo)⋯ N(aldoximo) 2·738(25)–2·822(29), N(pyridyl)⋯ N(pyridyl) 2·917(30)–3·050(29)A, and the N(aldoximo)⋯ N(pyridyl)‘bite’ 2·512(30)–2·598(29)A. The triangle defined by the three aldoximo-nitrogen atoms is rotated by only 0·89° relative to that defined by the three pyridyl nitrogens.The unsolvated species [{FB(ONCHC5H3N)3P}CoII+][BF4–](II) crystallizes in the monoclinic space group P21/c with a= 13·262(12), b= 17·967(4), c= 10·656(16)Aβ= 108·87(12)°, and Z= 4. An attempted X-ray crystallographic study of this complex was thwarted by an apparently hydrolytic single-crystal transformation to an unknown species.

X-Ray study of the co-ordination geometry about iron in the {fluoro[6,6′,6″-phosphinidynetris(α-picolinaldehyde oximato)(3-)]borato(1-)}iron(1+) cation. Trigonal prismatic encapsulation vs. octahedral ligand-field stabilization energy

A single crystal X-ray diffraction study of [{FB(ONCH·C5H3N)3P}FeII]+[BF4]–, CH2Cl2 shows the co-ordination geometry about the iron atom to be distorted by approximately 21·5° from the ideal trigonal primatic case.

Crystal structure and molecular geometry of 3-ethyl-3-alumina-1,2-dicarba-closo-dodecaborane (12), 1,2-B9C2H11AlEt

The title compound crystallizes in the orthorhombic space-group Pnma(D2h16; No. 62) with a= 16·304(15), b= 7·533(7), c= 9·398(6)A, and Z= 4. A three-dimensional single-crystal X-ray structural analysis based on counter data has led to the location of all atoms save ethyl hydrogens. The structure was solved by Patterson and Fourier methods and refined by least-squares techniques to R 8·49% for 499 independent non-zero reflections. The crystal consists of discrete, well separated, molecular units of 1,2-B9C2H11AlEt in which the aluminium atom is σ-bonded to an ethyl group and is linked symmetrically to the open B3C2 face of a dicarba-nido-undecaborane ligand.