nan Mazhar-Ul-Haque

Crystal structure and absolute configuration of bromoisotenulin

Bromoisotenulin crystallises in the monoclinic space group P21, a= 8·732(3), b= 23·094(6), c= 10·237(5)A, β= 121·27(10)°, Z= 4, with two independent molecules in the asymmetric unit. Two sets of data were collected: photographic, 2300 reflections, and diffractometer, 1700 reflections. The structure was solved by Patterson and heavy-atom methods, and the diffractometer data refined by full-matrix least-squares to R 0·075. The results confirm the structure (IV) suggested by Herz et al. and supply the unknown stereochemistry and absolute configuration. The carbon skeleton is biogenetically abnormal, a methyl group having migrated from C(4) to C(5). Both five-membered rings are trans-fused to the seven-membered ring. Attention is drawn to an error in the published stereochemistry of the related compound, bromomexicanin E.

Crystal and molecular structure of NN-dimethyldiphenylphosphinamide

The crystal and molecular structure of the title compound (I) has been determined by single-crystal X-ray diffraction. Crystals are orthorhombic, space group P212121, a= 7.670(4), b= 11.141(3), c= 15.644(5)A, and Z= 4. The structure was solved from diffractometer data by the heavy-atom technique. Positional and anisotropic thermal parameters were refined by full-matrix least-squares methods to a final R factor of 6.5% for 1 005 observed reflections. The phosphorus, nitrogen, and two methyl carbon atoms are non-planar.

The X-ray crystal structure of trinitrato-1,2-di(pyridine-2-aldimino)ethanegadolinium(III)

The title compound is shown by X-ray crystallographic analysis to possess a ten-co-ordinated metal ion having an irregular co-ordination polyhedron of point group C1.

Crystal and molecular structure of 5-t-butyl-2-methyl-2-oxo-1,3,2-dioxaphosphorinan (C8H17PO3)

The crystal structure of 5-t-butyl-2-methyl-2-oxo-1,3,2-dioxaphosphorinan (C8H17PO3) has been determined by three-dimensional X-ray analysis. The crystals are orthorhombic, space group Pbca, with Z= 8 in a unit cell of dimensions a= 11·371, b= 12·557, and c= 14·608 A. Intensities of 971 reflections were measured on a diffractometer. The structure was solved by Patterson and Fourier methods and refined to R 6·9% for 529 observed reflections. The six-membered ring is in a distorted chair form with the t-butyl group cis to the methyl group at C(11). The bond angles around phosphorus range from 104·4–113·2°. Some bond distances are: PO 1·48, P–O 1·56 and 1·58, and C–C 1·47–1·59 A; the mean σ is 0·02 A for bond distances and 0·8° for bond angles. Comparisons with other 1,3,2-dioxaphosphorinans having oxygen or bromine substituted axially at phosphorus suggest a dependence of angular geometry on the size of the axial substituent.

Crystal and molecular structure of bromohelenalin (C15H17O4Br)

Bromohelenalin C15H17O4Br crystallises in the orthorhombic space group P212121 with Z= 4 in a unit-cell of dimensions, a= 8·873 ± 0·004, b= 12·272 ± 0·003, and c= 13·187 ± 0·003 A. Intensities were measured on a diffractometer and the structure refined to a final R of 5·8% for 1125 observed reflections. The conformation of the seven-membered ring is a deformed chair, with 1- and 5-junctions trans and the lactone junction is cis. The carbon skeleton is biogenetically abnormal, a methyl group having migrated from position 4 to 5. The bond distances and angles are normal. The standard deviations are 0·01–0·02 A for the interatomic distances and 0·6–0·9° for the bond angles.