Volume 175, Issue 1-2

A new family of silicate phases, Cs 2 MSi 5 O 12 : M = Be, Mg, Fe, Co, Ni, Zn, Cd; Rb 2 MSi 5 O 12 : M = Mg, Fe, (Co, Zn) has been prepared with the cubic pollucite structure, a in the range 13.3 to 13.8 Å, space group Ia 3 d , Z = 8. The structure of one, Rb 2 MgSi 5 O 12 , has been refined to R = 10.8% using X-ray powder data. The structures are built of a 3D, [MSi 5 O 12 ] 2− framework containing large, 12-coordinated cavities for the alkali cations. These structures are unusual in that a wide range of divalent cations have partially replaced Si 4+ in the silicate anion framework.

The crystal structure of 2-one phenanthrene (C 16 H 16 O 2 ) has been determined from three-dimensional X-ray data. The space group is P 2 1 / c with unit-cell parameters a = 12.519(9) Å, b = 7.654(3) Å, c = 12.988(3) Å, β = 98.14°(3), Z = 4, V = 1231.51 Å 3 , D c = 1.24 g/ml, D o = 1.23 g/ml, μ = 6.8/cm, λ = 1.5418 Å, F (000) = 512 and 1840 observed reflections ( R = 0.051). The H-atoms were located from difference syntheses. The structural relationships between the rings are discussed.

Insertion of a 2-connected vertex into alternate edges of a 2 D net leads to a new family of 3 D nets. The simplest operation is conversion of 2-connected vertices of adjacent parallel 2 D nets into a square-planar vertex. Relative rotation of tetrahedral vertices above and below each square-planar vertex converts it into a tetrahedral vertex. The simpler nets of each type are enumerated for the 6 3 , 3.12 2 , 4.8 2 and 4.6.12 2 D nets; these nets have higher symmetry and less geometrical distortion than the infinity of nets which are not listed. A further set of nets is obtained by applying a sigma transformation in the plane of each original 2 D net. The structures of the beryl and milarite groups of minerals are based on 3 D nets obtained from the 6 3 net, and that of steacyite from the 4.8 2 net.

Replacement of each 4-ring in a stack of congruent 2 D nets by a double-bifurcated chain leads to new 3 D nets. Each 3 D net is turned into 3 more nets by applying a σ -transformation either in the plane of each original 2 D net, or through each bifurcated chain, or both. The simpler nets with highest symmetry are enumerated for the 4.8 2 and 4.6.12 2 D nets. A further type of net is obtained by transforming each σ , σ -double-bifurcated chain from the rod symmetry group pmmm to p 4 2 / mmc by a screw operation.

Thin films of SnSe vacuum deposited on glass substrates kept at different temperatures have been studied by X-ray diffraction. It is observed that the high temperature phase of SnSe, usually found above 807 K is frozen in along with the low temperature phase when deposited at substrate temperatures of 473 K and above.

The bond lengths, edge lengths and angular distortions were evaluated for 311 TO 4 units of distorted tetrahedral symmetry for 16 T elements in 191 compounds and for three ZnCl 4 units. The bond length distortions increase fairly regularly with decreasing size of the central ion while the edge lengths and angular distortions have minima close to the ionic radius of P 5+ . The transition metal ions V 5+ , Cr 6+ , Mo 6+ and Zn 2+ and to some extent also second row elements follow the general trends observed for the other central ions. The average ratio of bond lengths to angular distortions also increases with decreasing ionic radius to a maximum at P 5+ . Possible influences of the valence of the central ion are also discussed. The distortions of the ZnCl 4 units are considerably smaller than the average of the ZnO 4 units, most likely as a result of the larger ionic size of the anions. There also appears to be an effect of the counterions since for ClO 4 − units in compounds of very bulky cations the average bond lengths are smaller and the average distortions are several times larger than in alkali and ammonium Perchlorates. The distortions also seem to increase with temperature.

In the system CuO – SeO 2 – H 2 O three new copper(II)-selenites were synthesized under hydrothermal conditions. The crystal structures were determined by single crystal X-ray techniques: Cu(SeO 3 )-II [ a = 5.962(1) Å, b = 7.010(1) Å, c = 12.240(1) Å, space group Pcab , Z = 8, R w = 0.020], Cu(SeO 3 )-III [ a = 7.725(1) Å, b = 8.241(1) Å, c = 8.502(1) Å, β = 99.16(2)°, space group P 2 1 / n , Z = 8, R w = 0.046] and Cu(SeO 3 )-IV [ a = 4.736(2) Å, b = 8.579(4) Å, c = 10.618(5) Å, α = 66.69(2)°, β = 88.53(2)°, γ = 88.40(2)°, space group P [unk], Z = 6, R w = 0.044]. All the Cu atoms are “square planar” four coordinated by oxygen atoms with Cu – O < 2.10 Å. In addition four of the seven crystallographically different Cu atoms have one distant O atom and one Cu atom has two distant O atoms. For two Cu [4+1] atoms the fifth O atom has Cu – O < 2.22 Å and the “square planar” coordination figure is strongly bent. In Cu(SeO 3 )-IV one CuO 4 square shares a common O – O edge with a SeO 3 group (O – O = 2.411 Å). The previously known high temperature – high pressure compound Cu(SeO 3 )-I has an approximately 12% closer packed atomic arrangement.

The crystal structures of N- para -bromobenzoyl- α -aminoisobutyric acid (1), and its 5(4H)-oxazolone (2) and methyl ester (3) derivatives have been determined by X-ray diffraction techniques. The compounds possess the following parameters: (1) monoclinic, space group P 2 1 / a , a = 10.057(4), b = 12.733(4), c = 9.706(4) Å, β = 99.8(3)°, and Z = 4; (2) monoclinic, P 2 1 / a , a = 12.637(4), b = 7.818(3), c = 12.241(4) Å, β = 110.7(2)°, and Z = 4;(3) orthorhombic Pcab , a = 17.615(5), b = 14.357(5), c = 10.251(4) Å, Z = 8. The crystal structures were solved by direct methods. The least-squares refinements led to R values of 0.067, 0.047 and 0.048 for 1205, 1510 and 734 reflections with I > 3 σ (I) for 1 – 3, respectively. The conformation of compounds (1) and (3) is remarkably similar, with a trans amide bond and folding about the N – α C bond. The C = N bond of the oxazolone group of compound (2) is not conjugated with the ester moiety.

Crystals of N 2 -dimethylthiosalicylohydrazide are monoclinic, with space group P 2 1 and cell parameters a = 10.667(2), b = 9.155(2), c = 10.378(2) Å, β = 92.46(1)°, Z = 4 (two molecules in the asymmetric unit), D c = 1.286 g cm −3 . The crystal structure has been solved by Direct methods and Fourier syntheses. The least-squares refinement led to a final R value of 0.055 with 1792 observed reflections. The ligand may exist in (i) thiolo or in (ii) thiono form. IR spectrum of the ligand did not exhibit ν (SH) at ca. 2600 cm −1 . So it is assumed that the configuration (ii) is the preferred one. Structure analysis of the ligand has further supported this. There exists intramolecular hydrogen bonding between nitrogen in position 1 and oxygen, but no intermolecular hydrogen bonding is observed.

Deca-dodecasil 3R, 120 SiO 2 · 6M 10 · 9M 12 · 6M 19 with M 12 = N 2 and M 19 = C 10 NH 17 (1-aminoadamantane), crystallizes in space group R [unk] m with a = 13.860(3) Å and c = 40.891(8) Å. Its crystal structure is built by corner-sharing [SiO 4 ] tetrahedra. The tetrahedra are connected to pseudohexagonal layers of face-sharing pentagonal dodecahedra ([5 12 ] cages). These layers are stacked in ABCABC sequence and interconnected by additional [SiO 4 ] tetrahedra which form six-membered rings between the layers. Thus two new types of cage arise, another small decahedron, [4 3 5 6 6 1 ] cage and a large 19-hedron, [4 3 5 12 6 1 8 3 ] cage, the latter housing the 1-aminoadamantane guest molecule. The 19-hedra are interconnected through 8-membered rings (pore width 4.5 Å), forming a two-dimensional pore system between the dodecahedral layers. Untreated deca-dodecasil 3 R is a member of the clathrasil family because the guest molecules trapped during synthesis are too large to pass through the 8-membered rings of the 19-hedra. However, on thermal treatment of deca-dodecasil 3 R the guest molecules are decomposed and the fragments are driven out of the cages, transforming the clathrasil to a phase possessing zeolitic properties.

Tetraethylammonium calcium triazide is formed by the reaction of tetraethylammonium azide with calcium azide in aqueous solution. The crystals are monoclinic, a = 7.154(2), b = 7.112(2), c = 7.154(2) Å, β = 96.05(1)°, space group P 2/ m , Z = 1. Additional weak reflections on highly exposed X-ray films point to the existence of a superlattice with each cell length six times the original value ( Z = 216). The crystal structure for the simple monoclinic cell was investigated by X-ray methods, R = 0.051. Calcium is octahedrally coordinated to six azide groups, the structure corresponds to a monoclinic distorted perovskite. The tetraethylammonium groups could not be completely localized, and they were approximated by a model consisting of several partially occupied lattice positions.

Single crystals of slightly hygroscopic barium nitrite Ba(NO 2 ) 2 were prepared by thermal decomposition of barium nitrite monohydrate and subsequent recrystallization in a solution of methanol and p-xylene. The compound crystallizes in the orthorhombic space group P 2 1 2 1 2 1 with a = 7.6331(16) Å, b = 8.3671(36) Å, c = 6.7336(8) Å and Z = 4. The structure was determined from X-ray intensities measured on a four-circle diffractometer and refined to R = 0.035 and wR = 0.048. The barium atoms exhibit an elevenfold coordination made up by nine oxygen atoms within distances ranging from 2.776(6) Å to 3.010(6) Å and two nitrogen atoms within distances of 3.059(7) Å and 3.125(7) Å. Values for the O – Ba – O angles range from 41.5(2)° to 151.1(2)°. The N – O distances are in the range 1.236(9) to 1.265(8) Å.

Bis(N-2-phenyl-ethyl salicylideneiminato)nickel(II) crystallizes in the monoclinic system, space group P 2 1 / n with a = 6.088(3), b = 13.601(2), c = 14.862(3) Å, α = 90.3(2)° and Z = 2. The intensity data were collected using a CAD-4 diffractometer with Mo Kα radiation. The structure was determined by Patterson and Fourier methods ( R = 0.061 for 1100 Mo Kα reflections). An interesting result of this structure determination is the confirmation of the square planar coordination of the nickel(II) ion in this complex. The Ni – O and Ni – N bond lengths have values 1.84(1) and 1.93(1) Å, respectively. The two aromatic rings are planar and the angle between these planes is 64.1(3)°.

The crystal structure of Ba 9 Ge 23 O 53 (OH) 4 has been determined at 300°K. Single crystals of this material were obtained at pressures of 4.0 – 6.0 GPa and temperatures of 750° – 1100°C. A previous report has incorrectly identified this material as “Ba 2 Ge 5 O 12 ”. The crystals belong to the hexagonal system with a = 11.6784(12), c = 19.2545(13) Å, space group P 6 3 cm , Z = 2. Calculated density is 5.58 gcm −3 . Of the 57 anion sites, the three O(7) sites are occupied by OH. A random partial occupancy by OH and O of the three O(4) anion sites was assumed (O/OH = 2/1). Of twenty three Ge atoms, twelve are tetrahedrally 4-fold, three are tetragonal pyramidally 5-fold, and eight are octahedrally 6-fold coordinated. Three Ba atoms are surrounded by nine, ten, eleven anions, respectively. There are Ge 3 O 10 and Ge 3 (O/OH) 11 rings and a quarter of the unit cell (1/4 c ) is close to the structure of BaGe 4 O 9 .

The molecular structure of the title compound has been determined by X-ray crystallography. The crystals are monoclinic, space group P 2 1 / a , with a = 10.818(1), b = 9.062(1), c = 11.822(1) Å, β = 91.87(1)°, Z = 4. The structure has been solved by direct methods and refined by least-squares techniques to R = 0.0469 on 1684 counter intensities. Crystallographic data analysis demonstrates that in the solid state the δ -lactone adopts a distorted half-chair conformation due to the planarity of the carbonyl group, and the benzene ring is in the axial position. The mutual orientation of the lactone ring and the phenyl substituent obtained by potential energy calculations and by NMR spectroscopic analysis is in agreement with the results of the present study.

The crystal structure of W-type hexaferrite, SrZn 2 Fe 16 O 27 (Zn 2 – W), has been refined with 932 3-dimensional symmetry-independent single crystal reflections. With anisotropic temperature factors for the cations an R -value of 0.061 ( R w = 0.048) has been attained.

The crystal structure of thallium(I) dideuteriumphosphate has been determined by single crystal X-ray analysis. The crystals are monoclinic, a = 6.512(2), b = 4.518(1), c = 14.319(2) Å, β = 91.63(3)°, space group (non-deuterium atoms) P 2 1 / c , Z = 4. The structure was refined to R = 0.038 and R w = 0.035 by full-matrix least-squares methods, using 710 independent reflections measured with single crystal diffractometer. The structure of TlD 2 PO 4 looks very similar to that of TlH 2 PO 4 . The shape of the PO 4 tetrahedron is rather regular. The PO 4 tetrahedra are connected by D-atoms to form a zigzag chain running along the smallest b -axis.

The title compound Cu(C 6 N 4 H 10 ) 2 (NO 3 ) 2 crystallizes in space group P [unk] with a = 9.708(3), b = 5.464(2), c = 9.367(3) Å, α = 92.99(3), β = 101.24(3) and γ = 108.54(3)°, Z = 1, ϱ c = 1.66 gm/cm 3 , μ = 2.05 mm −1 . The structure was solved by heavy-atom technique and was refined by least-squares method to R = 0.056. The Cu atom on the centre of inversion displayed a distorted octahedral coordination.

Single crystals of monoclinic betaine fluoroborate monohydrate of optical quality with dimensions up to 60 × 50 × 15 mm have been grown from aqueous solutions by controlled evaporation at constant temperature. The crystals belong to space group P 2 1 / c with cell parameters a 1 = 9.829(3) Å, a 2 = 9.192(2) Å, a 3 = 12.105(3) Å, α 2 = 110.94(2)°. Dielectric constants, coefficients of thermal expansion, indices of refraction, elastic and thermoelastic constants are reported. The dielectric tensor exhibits quasi-isotropy, whereas the other properties show distinct effects of anisotropy.