Volume 210, Issue 9

The contribution of Umweganregung (multiple diffraction) on space group forbidden X-ray single crystal diffraction intensities in synthetic pyrope garnet, Mg 3 Al 2 Si 3 O 12 , (space group la [unk] d ) was measured with ω – 2[unk] scans at ψ values between 0 and 45 degrees in ψ -steps ≤ 0.2 degrees and also calculated with the program UMWEG90. These calculations require the orientation matrix, the refined structural parameters and an estimate of the mosaic block size and of the mosaic spread. Results indicate satisfactory agreement between experimental and modelled intensities caused by Umweganregung. Structure refinements of metrically cubic garnets from the literature where a space group lower than Ia [unk] d was suggested on the basis X-ray diffraction data are critically discussed with respect to Umweganregung.

Bismuth triiodide free of stacking faults was obtained by synthesis from the elements and sublimation in quartz tubes. X-ray investigations using a twinned crystal (space group R [unk] (No. 148), a = 752.49(3) pm, c = 2073.3(1) pm, V = 1016.7(2) · 10 6 pm 3 ) confirmed the rhombohedral stacking sequence of BiI 3 layers. The bismuth atoms are shifted about 4 pm along the c axis out of the centres of the octahedral sites. The stacking order of BiI 3 layers is discussed.

The structure of Al 2 GeO 4 (OH) 2 [ C 2/ c ; a = 5.4197(3) Å, b = 8.2464(3) Å, c = 9.3187(3) Å, β = 110.933(3); Z = 4] was refined by X-ray Rietveld methods. It contains GeO 4 tetrahedra having all four O atoms in common with an AlO 2 OH framework built from AlO 4 (OH) 2 octahedra sharing three edges. The H atom could be located only approximately. The coordinations of the atoms are mostly as in topaz, Al 2 SiO 4 (F,OH) 2 , and its synthetic OH endmember, but the arrangement of the oxygen atoms is that of a distorted cubic close-packing, while in topaz it is based on a close-packing of the type ABAC.

The crystal structure of the title complex has been determined by X-ray diffraction at room temperature. Monoclinic crystals of C 20 H 24 CuN 2 O 4 have space group P 2 l / n with unit cell dimensions a = 11.832(2) Å, b = 11.981(5) Å, c = 14.764(5) Å, β = 112.20(2)°, Z = 4, D x = 1.44 and D m = 1.44 Mg m −3 (by flotation). The structure was refined by a full-matrix procedure on 1771 reflections to final R = 0.069. The copper atom in the structure exists in a square-planar geometry formed by two O and two N atoms of two salicylideneaminato ligands. The molecule is almost planar with the perpendicular distance between Cu atom and the benzene ring planes from two salicylideneaminato ligands of 0.006(1) Å and 0.003(1) Å, respectively. In order to compare these results with those in the analogous structures of bis ( N -phenylsalicylideneaminato)copper(II) and bis ( N -2-hydroxyethylsalicylideneaminato)copper(II), the two latter structures have been redetermined by us and are published as New Crystal Structures on pages 728–730.

Zn (II)-tetra(3-hydroxyphenyl)porphyrin (C 44 H 28 N 4 O 4 Zn) was obtained as solvate (1:2) by recrystallization of the commercially available metalloporphyrin derivative from dimethylsulphoxide (DMSO). The crystals are monoclinic, space group C 2/ c , with a = 1883.9(4) pm, b = 1200.9(2) pm, c = 2084.6(5) pm and β = 117.45(2)°. They consist of five-coordinated square-pyramidal metalloporphyrin units, involving one DMSO ligand at the axial position. These units are cross-linked in the lattice by an extensive network of hydrogen bonds. The second molecule of the DMSO approaches the other side of the porphyrin core. It is not linked to the metal center, but takes part in H-bonding interactions with adjacent porphyrin molecules. The 1:2 porphyrin-DMSO clusters are orientationally disordered in the crystal lattice.

The crystal structures of three diimine adducts of diphenyltin dichloride have been determined at room temperature. The colorless crystals of the adduct formed with 5-methylphenanthroline, [Ph 2 SnCl 2 (5-Mephen)], C 25 H 20 Cl 2 N 2 Sn, are monoclinic, space group P 2 1 / n with unit cell dimensions a = 9.393(5) Å b = 12.896(3) Å, c = 18.034(4) Å, β = 94.48(3)°, Z = 4 and D x = 1.641Mg m −3 . The yellow crystals of the 4,7-dimethylphenanthroline adduct, [Ph 2 SnCl 2 (4,7-Me 2 phen)], C 26 H 22 Cl 2 N 2 Sn, are monoclinic, space group P 2 1 / n with unit cell dimensions a = 9.163(2) Å, b = 17.828(4) Å, c = 14.395(5) Å, β = 101.29(2)°, Z = 4 and D x = 1.590Mg m −3 . Yellow crystals of the 4,5-diazafluorene-9-one adduct, [Ph 2 SnCl 2 (4,5-diazafluorene-9-one)], C 23 H 16 Cl 2 N 2 OSn, are orthorhombic, space group Pbca with unit cell dimensions a = 16.239(2) Å, b = 16.673(2) Å, c = 16.058(2) Å, Z = 8 and D x = 1.607Mg m −3 . The structures were solved by direct methods and refined by a full-matrix least-squares procedure to final R = 0.043 using 2542 reflections for [Ph 2 SnCl 2 (5-Mephen)], R = 0.060 using 2521 reflections for [Ph 2 SnCl 2 (4,7-Me 2 phen)], and R = 0.038 using 1919 reflections for [Ph 2 SnCl 2 (4,5-diazafluorene-9-one)]. The tin atoms in the three adducts exist in distorted octahedral geometries with the phenyl substituents occupying trans positions. An examinations of the derived parameters in the three structures shows that the two phenanthroline ligands have similar coordinating abilities towards Ph 2 SnCl 2 and that these ligands are stronger Lewis bases than 4,5-diazafluorene-9-one.

Bis[acetatotriphenylphosphinesilver(I)] crystallizes from toluene as the hemihydrate, [CH 3 CO 2 Ag · P(C 6 H 5 ) 3 ] 2 · ½ H 2 O, which exhibits trigonal planar coordination at the silver atom. The structure has been refined to R = 0.051 for 3720 reflections.

The crystal structures of three 1,5-anhydropentitols of formulae C 5 H 10 O 4 and their per- O -acetyl derivatives of formulae C 11 H 16 O 7 are reported. 1,5-anhydro- D -arabinitol (ADA), 1,5-anhydroribitol (AR), 1,5-anhydroxylitol (AX), 2,3,4-tri- O -acetyl-1,5-anhydro- D -arabinitol (AcADA), 2,3,4-tri- O -acetyl-1,5-anhydroribitol (AcAR) and 2,3,4-tri- O -acetyl-1,5-anhydroxylitol (AcAX) have the following space group and unit cell parameters: ADA, orthorhombic, P 2 1 2 1 2 1 , a = 6.521(1) Å, b = 6.826(1) Å, c = 13.557(3) Å; AR, monoclinic, P 2 1 / n , a = 6.515(1) Å, b = 12.003(1) Å, c = 8.272(1) Å, β = 105.65(1)°; AX, monoclinic, P 2 1 / n , a = 6.652(2) Å, b = 9.224(2) Å, c = 10.548(2) Å, β = 101.80(1)°; AcADA, orthorhombic, P 2 1 2 1 2 1 , a = 8.182(2) Å, = 10.768(2) Å, c = 15.111(3) Å; AcAR, monoclinic, P 2 1 / c , a = 15.178(1) Å, b = 10.339(1) Å, c = 8.038(1) Å, β = 92.50(1)°; and AcAX, monoclinic, P 2 1 / c , a = 12.092(1) Å, b = 9.066(1) Å, c = 12.492(2) Å, β = 102.39(1)°. The structures were solved using direct methods and refined by full-matrix least-squares techniques to R indices of 0.033, 0.042, 0.045, 0.066, 0.055 and 0.048, respectively. The pyranoid ring adopts 4 C 1 chair confirmation in the molecules of AR, AX and AcAX, and the 1 C 4 one in the molecules of ADA, AcADA and AcAR. Theoretical methods were used to examine lattice energetics and molecular packing in the crystals formed.