On the relative scaling of X-ray photographs

The crystal structure has been determined from three-dimensional X-ray data collected by photographic methods. The crystals are monoclinic, with unit-cell dimensions a= 14.081 (5), b= 17.590 (5), c= 16.567 (5) A,, fl= 91-02 (10)°; the space group is P21/n and Z= 4. The structure was solved by Patterson and Fourier methods, and refined by the least-squares method on the basis of 3933 indelzendent observations. The final value of conventional R is 0.1009. The thorium atom has a coordination number of ten involving eight oxygen atoms from four bidentate nitrate groups and two oxygen atoms from the Th-O-P linkages as immediate neighbours. The triphenylphosphine groups are linked with thorium through Th-O-P linkages and are related by an approximate twofold axis of symmetry passing through the thorium atom. The phosphorus atoms have irregular tetrahedral coordination with average P-C bond length= 1"80 (3) and P-O= 1"45 (2) ,~. The phenyl rings are planar with average C-C distance = 1.40 (6) A. The Th-O(bridging) distances, 2.37 (2) and 2.33 (2) ,~, are shorter than the Th-O(nitrate) distances, 2.52 (2) to 2.58 (2) ,~. The nitrate groups are planar with average N-O distance= 1.24 (6) A. 2687

Section: Crystal Datamentioning

confidence: 99%

The crystal structure of tetranitratobis(triphenylphosphine oxide)thorium(IV)

Malik¹,

Jeffery²

1973

“…Standard deviations were assigned to single observations by means of an analysis of the residuals (Gramaccioli & Mariani, 1967). The evaluation of relative scale factors for all the layers and subsequent averaging of the observed F z values were performed according to the method proposed by Rollett & Sparks, modified to account for the dependence of the weights upon the final scale factors (Hamilton, Rollett & Sparks, 1965;Duchamp, 1964).…”

Section: The Structure Of L Lll-difluoro-16-methano[10]annulenementioning

confidence: 99%

The structure of 11,11-difluoro-1,6-methano[l0]annulene

Gramaccioli¹,

Simonetta²

1971

The crystal and molecular structure of 11,11-difluoro-l,6-methano[10]annulene has been determined and refined by least-squares methods. The crystals are orthorhombic, space group Pna2a, with a = 9-233, b= 13"235, c=7"055 A and four molecules per unit cell. Intensity data were collected visually from Weissenberg photographs. The solution of the phase problem was readily obtained by finding the orientation of a plausible molecular model with respect to the crystallographic axes through a systematic search of the Patterson synthesis around the origin; the position of the molecule in the unit cell was then found by molecular packing energy calculations. After refinement by least-squares, the final R index is 0.080. The presence of fluorine atoms does not seem to affect the conformation of 1,6-methano [10]annulene; the distance C(1)-C(6) is 2.25 A,, excluding any 'double norcaradiene' character for this compound, in agreement with chemical and spectroscopic evidence.

“…The visually estimated intensities were corrected for Lorentz and polarization factors but absorption was ignored. A set of scaled structure amplitudes was derived (Hamilton, Rollett & Sparks, 1965), which, after reduction, consisted of 1426 independent observed and 908 unobserved reflections. …”

Section: Methodsmentioning

confidence: 99%

Preparation and X-ray analysis of a 1:1 adduct of hexamethylenetetramine oxide and thiourea

Yu¹,

Mak²

1978

A 1:1 adduct of hexamethylenetetramine oxide and thiourea (C6HI2NgO.CH4N2S)has been prepared and subjected to crystal-structure analysis. The crystals are orthorhombic, space group Pbca, with a = 7.698 (5), b = 12.03 (1), c = 23.09 (2) ,~, and Z = 8. The structure was solved by direct methods and refined with 1426 observed Cu Ka film data to R = 0.099. In the crystal lattice each (CH2)6N40 molecule is linked by O---H-N hydrogen bonds to three thiourea molecules and vice versa, giving rise to corrugated layers normal to c. Neighboring layers, related by the c glide, pack with protruding (CH2)6N 4 groups fitting into hollows between the layers.