Band 164, Heft 1-2

Gem-N 3 P 3 Az 4 Cl 2 , a novel anticancer agent, crystallizes in the monoclinic system (space group P 2 1 / n ). The cell-constants are a = 8.367(3), b = 24.231(6), c = 8.080(3) Å, β = 103.25(4)° and Z = 4. The structure has been determined using X-ray single crystal techniques and refined to R = 0.039. Aziridinyl wings exhibit a spatial arrangement which is consistent with the ones previously observed for some other anticancer inorganic rings systems, namely (NPAz 2 ) 3 and (NPAz 2 ) 2 (NSOAz).

The crystal structure of trans -2-isopropyl-1,3-dioxane-5-carbothioamide has been determined by single crystal X-ray analysis. The crystals are monoclinic, a = 4.923(1), b = 9.008(2), c = 22.802(4) Å, β = 96.925(2)°, space group P 2 1 / c , Z = 4. The structure was refined to R = 0.089 and R w = 0.085 by block-diagonal least-squares methods, using 743 independent reflections measured with a single-crystal diffractometer. The amino group takes part in an intermolecular hydrogen bond.

A neutron diffraction analysis was performed on a single crystal of natural natrolite, Na 2 Al 2 Si 3 O 10 · 2H 2 O, orthorhombic, Fdd 2, a = 18.326(5) Å, b = 18.652(5) Å, c = 6.601(3) Å, Z = 8. Refinement of 235 independent reflections yielded R = 0.028. The Al – O and Si – O bond distances are determined with a precision of 0.005 Å. The O – H bonds range from 0.9125 to 0.9130 Å. The mean angle O – H … O is 156.9°.

Co(H 2 PO 4 ) 2 · 2H 3 PO 4 , triclinic, P [unk], a = 8.121(4), b = 5.286(2), c = 7.195(4) Å, α = 92.97(3), β = 101.10(4), γ = 96.72(3)°, V = 300.1(2) Å 3 , D x = 2.48 g cm −3 (calculated for Z = 1), μ (Mo Kα ) = 2.11 mm −1 , final R = 0.030. The structure consists of Co 2+ and H 2 PO 4 − ions and H 3 PO 4 molecules. The coordination around cobalt is octahedral. Phosphate tetrahedra form layers parallel to y - z plane. Two neighbouring layers are linked by hydrogen bonds and Co 2+ ions in sheets. No hydrogen bonds exist between the sheets.

The parameter β and the squares of the axial ratios are calculated in a first step. These are then used to calculate the parameters a , b and c from the angular position of each diffracted line in a series of three very simple and short calculations. The influence of systematic errors and its partial elimination is also considered. All these points are illustrated by an actual case.

In a series of papers some results will be submitted which can be obtained by double diffractometric topography, whose principle, if the nondispersive ( n , − n ) setting is applied, consists in quasi-parallelity of the primary beam. Paper I demonstrates the imaging laws brought forward by this technique in the Laue case, which reveal to be very different from the familiar ones for the Bragg case. They are discussed by means of the topographic images of lattice defects, artificial ones (scratches) and those grown in (dislocations, stacking faults, point defects et al.). Subdividions of the defect images into two kinds only, “dynamical” and “kinematical” ones, are proposed.

The mineral Srilankit (Zr 0,33 Ti 0,67 )O 2 crystallizes orthorhombic in the space group Pbcn with the lattice constants a = 4,706(5), b = 5.553(5), c = 5.024(4) Å, Z = 4. The crystal structure was determined from single crystal X-ray diffractometer data and refined to R = 3.4%. Zr and Ti are distributed at random among the sites of the α -PbO 2 structure. Each metal ion is bonded to six oxygens forming distorted (Ti,Zr)O 6 -octahedra with metal-oxygen distances of 1.924(4), 2.002(4) and 2.138(4) Å.

Kirfel, Will, and Arndt (1979) reported a quenchable new phase of SiO 2 , synthesized in aqueous solution at 44 – 49 kbar and 610°C, having the space group P 2 1 / a and a crystal structure closely related to coesite. However, single-crystal X-ray and TEM studies have revealed that their observations could be the result of (100)-twinning of C 2/ c coesite. Therefore, a distinct P 2 1 / a phase probably does not exist. The evidence is: (1) The intensity distributions in the diffraction patterns of the (100)-twinned C 2/ c coesite are similar to those calculated using the reported P 2 1 / a structure. (2) The least-squares refinements using the (100)-twinned model yielded results similar to those reported for the P 2 1 / a phase. (3) The cell dimensions reported for the P 2 1 / a phase, when transformed to a C 2/ c cell, are not significantly different from those reported by other authors for normal coesite. (4) The P 2 1 / a phase cannot be distinguished from normal coesite on the basis of the calculated powder diffraction patterns. (5) Syntheses under a wide range of conditions have produced only C 2/ c coesite crystals.

The crystal structure of nepheline hydrate I, cesium exchanged at 80°C to an approximate composition of Cs 0.84 Na 2.16 Al 3 Si 3 O 12 · 0.32 H 2 O, was determined by studying the main reflections in the single crystal X-ray diffraction pattern. This average structure is orthorhombic with: a = 8.132(3), b = 15.179(2), c = 5.1865(8) Å, Pnm 2 1 , Z = 2, D m = 2.7, D c = 2.72 g cm −3 and was refined by least-squares techniques to the final residuals, R = 0.049 and R w = 0.072. Only small alterations were found in the framework geometry and in the environment of two independent Na + ions which coordinate 7 framework O atoms. The Cs + ion is located in the large void and coordinated by 7 framework O atoms in a distorted hexagonal pyramid. About 1/6 of the large voids still contain Na + ions and two water molecules as in the starting material. A limit is observed in the ion exchange at ∼ Cs 1 Na 2 i.e. the crystals exhibit a partial ion sieving effect. This is explained by the restricted volume of 2/3 of the cation sites and the diameter of the associated 6-ring windows of O atoms. Since the satellite reflections are situated along a *, the real structure is modulated in one dimension.

The crystal structures of dirubidium-tetrazidozincate, Rb 2 Zn(N 3 ) 4 , and of dithallium-tetrazidozincate, Tl 2 Zn(N 3 ) 4 , have been determined from Mo Kα . single crystal X-ray diffractometer data and refined to R values of 0.073 and 0.089 respectively. Both compounds crystallize orthorhombic in space group Pca 2 1 with Z = 4. The structures are built up of isolated Zn(N 3 ) 4 tetrahedra. The univalent cations are surrounded by nine azide groups.

Similarity operators are applied to the study of displacive transitions. The example considered is the transition from the hexagonal NiAs to the orthorhombic MnP type. The number of displacement modes is superior to that deduced from representation theory of the wave vector group.

The crystal structure of (triphenylphosphine)(nitrosyl)(O-cyclopentyldithiocarbonate)nickel, Ni(NO)(PPh 3 )(S 2 COC 5 H 9 ), has been determined from three-dimensional X-ray diffraction data, collected on a computer-controlled Philips PW1100 single-crystal diffractometer (2894 observed reflections). The crystals are monoclinic, space group P 2 1 / c , with a = 10.416(1), b = 9.890(1), c = 23.876(4) Å, β = 97.84(1)° and Z = 4. The structure was solved by direct phase determination with MULTAN and refined by least-squares calculations to a final R = 0.038 ( R w = 0.040). The Ni atom is fourfold coordinated by two S, one P and one N atom, which form a strongly distorted tetrahedron. The xanthate ligand acts as bidentate, while the group NiNO is slightly bent. The Ni – S distances are practically equal, 2.328(1) – 2.329(1) Å, and the Ni – P and Ni – N distances are 2.240(1) and 1.650(4) Å respectively. In the nitrosyl ligand the N – O distance is 1.136(5) Å, while in the xanthate and the triphenylphosphine ligands the determined distances and angles are as expected. The crystal cohesion may be attributed to normal van der Waals forces.

The crystal structures of LiScO 2 and NaNdO 2 were investigated. They belong to the α -LiFeO 2 type and can be regarded as “stuffed” derivatives of the anatase type. Starting from observed distances d (M III – O), it is not possible to deduce a , c , c / a or Z 0 . The same holds for three hypothetical modifications derived from the NaCl type. The Madelung Part of Lattice Energy, MAPLE, which is calculated for these oxides and the hypothetical forms cannot explain the adopted values of a , c , and z 0 .

The crystal structure of lead niobate Pb 2.8 Nb 2 O 7.8 [ a = 7.520(1) Å, b = 32.513(8) Å, c = 7.542(1) Å; Cmc 2 1 ; Z = 10; ϱ = 7.96(12)g/cm 3 ] 1 is closely related to the pyrochlore type of Pb 1.5 Nb 2 O 6.5 . Sheets with the pyrochlore type structure parallel (010), displaced by (1/2,1/2,0) are interconnected by layers, which only contain lead atoms, sixfold coordinated by oxygen atoms. These lead atoms occupy the sites of niobium and lead atoms as they are present in the undistorted pyrochlore structure. But they have changed the oxygen coordination because of their position at a regularly spaced antiphase boundary of the two adjacent pyrochlore type sheets with an antiphase-vector c /2. The cation sites in this structure are fully occupied, but similar to Pb 1.5 Nb 2 O 6.5 at one of the oxygen positions, which do not belong to the framework of NbO 6 -octahedra, half of the sites are vacant.

The title compound, Cu(H 2 O)(dpgH) 2 , was synthesized. Its structure was determined by X-ray single crystal methods. Crystals are triclinic, space group P[unk], with a = 10.190(5) Å, b = 10.851(5) Å, c = 13.883(6) Å, α = 105.75(4)°, β = 96.76(4)°, γ = 115.26(4)°, V = 1287 Å 3 , Z = 2. The structure consists of linearily H-bonded molecules Cu(H 2 O)(N 2 O 2 C 14 H 22 ) 2 . The copper atom is in a tetragonal pyramid CuN 4 Ow with an unusually short Cu-water apical bound of 2.14(1) Å. The compound has a Curie-Weiss magnetic behaviour between liquid nitrogen and room temperature with μ eff = 1.78 B.M.

The diacetylene monomer crystal of C 20 H 28 N 2 O 8 are triclinic, P[unk], a = 25.753(8), b = 13.966(2), c = 4.940(1) Å, α = 85.19(1), β = 90.38(2), γ = 84.52(2)°, Z = 3. The monomer crystals of C 22 H 32 N 2 O 8 present a monoclinic “orange form”, C 2/ c or Cc , a = 36.509(5), b = 7.983(1), c = 9.783(1) Å, β = 96.02(1)°, Z = 4, but a twin often gives them an orthorhombic appearance. This second compound presents a solid-state polymerization but the first one is inactive.

The values of the estimated standard deviations given by the Rietveld profile refinement method are formally invalid, since the method does not take into account systematic errors which are introduced into the residuals by the constraints of the model from which the calculated intensities are derived.