S. W. Peterson

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.

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.

A neutron diffraction study of structural changes in one-dimensional K2Pt(CN)4Br0.3 · 3H2O from 77–323°K

Abstract Single crystal neutron diffraction measurements of K2Pt(CN)4Br0.3 · 3H2O (KCP) above room temperature, to the point of irreversible crystal breakdown (318–323°K), and at liquid nitrogen temperature (77°K), give no indication of a crystallographic phase change. Full three-dimensional data collected at 77°K ( a = 9.848(5) A , c = 5.714(3) A , and space group P4mm ) indicate that the structure is essentially unchanged from that at room temperature except for increased hydrogen bonding association between H2O(2) and Br(1). The possible relationship between the hydrogen bonding changes and Br(1) site ordering is discussed.

A comparison of low temperature neutron and X-ray structures of K2Pt(CN)4Br0.3·3H2O, KCP (Br)

We compare the structure of KCP determined at 77°K by neutron methods with that recently determined at 90°K by x-rays. Both methods find two Pt-Pt distances which are equal within normal error limits. The neutron study shows however that the Pt thermal motion is slightly anisotropic with preferred motion perpendicular to c; this is contrary to the x-ray result which finds a strongly anisotropic thermal vibration parallel to c. No evidence is found in the neutron study for the occupation by water of a second disordered site located at ∼c6 from the normal Br− site at 121212.

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.

Evidence for the non-existence of a bragg reflection superlattice in K2Pt(CN)4Br0.3·3H2O and K2Pt(CN)4Cl0.3·3H2O

An extensive and careful search for superlattice reflections in K2Pt(CN)4Br0.3·3H2O and K2Pt(CN)4Cl0.3·3H2O has yielded no evidence for an enlarged cell. Six individual crystals obtained via different preparative methods, from solutions at several pH values from 2 to 10, and subjected to a variety of conditions of temperature and humidity have been examined. All samples gave identical cells and nearly identical diffraction patterns. Two samples gave a single weak non-integral 00l neutron reflection which is not explainable by order contamination or double diffraction.