Band 190, Heft 1-2

An X-ray structural study of 1,8-bismethacryloyloxyoctadiyne-3,5 ( I ) ( R = 0.051 for 967 reflections) has been carried out. Infinite ribbons of molecules related by the b = 4.5340(4) Å translation can be distinguished in the crystal. The relative orientation of molecules does not permit their topochemical interaction via either shearing mechanism in ribbons involving the triple bonds or four-center polymerization involving the terminal double bonds.

From the keatite-type aluminosilicate LiAlSi 2 O 6 the corresponding compound HAlSi 2 O 6 has been prepared by ion exchange. Its structure is reported here, based on X-ray single crystal and neutron powder data. The keatite framework topology is not affected by the Li-H-exchange, but the framework geometry changes considerably: The bands of 5-rings extending in the a and b directions are stacked much more closely in the c direction than in LiAlSi 2 O 6 . This is primarily due to hydrogen bonds parallel to c that pull neighbouring 5-ring bands close together. Donor/acceptor distances of the O – H … O bonds are 1.04(1) and 2.03(1) Å, the bond angle at the hydrogen atom is 163.0(5)°.

The two following salts have been prepared [(CH 3 ) 2 C(NH 3 )-COOH] + · H 2 PO 4 − ( α MADP) and [CH 3 CH 2 CH(NH 3 )COOH] + · H 2 PO 4 − (L β MADP). The crystal parameters are: a = 10.060(2), b = 7.634(2), c = 5.852(2) Å, α = 97.32°(5), β = 107.50°(5), γ = 81.16°(5); Z = 2; P [unk] for α MADP and a = 7.164(2), b = 6.533(2), c = 9.458(2) Å; β = 105.48°(7); Z = 2; P 2 1 for L β MADP. Crystal structures were solved by direct methods and refined to a final R value 0.026 with 2889 independent data for α MADP and to R = 0.033 with 2027 reflexions for L β MADP. Hydrogen atoms located by difference-Fourier syntheses were refined. The layer structure of α MADP and the chain structure of L β MADP emphasize the importance of H 2 PO 4 − polymeric anion and its possible use in the design of polar inorganic materials. The effect of chirality on the anion-aggregation, through the hydrogen bonds, clearly indicated by the L β MADP structure and some others already described, may be easily transposed to individual, cylic, chain or layer inorganic oxoanions.

Inclusion of dispersion corrections in the generalized structure factor expression for the zinc blende structure give rise to the breakdown of Friedel's law for all even index reflections, an effect due to the presence of anharmonicity. Accurate X-ray diffraction intensity measurements have been obtained using a spherical single crystal of GaAs 0.065 P 0.935 at 298 K. Least-squares refinement yield the Debye-Waller factors, B Ga = 0.52 ± 0.01 Å 2 and B As/P = 0.39 ± 0.02 Å 2 , also the individual anharmonic thermal parameter β Ga = −1.8 ± 1.3 × 10 −17 J Å −3 and β As/P = −0.8 ± 0.6 × 10 −17 J Å −3 . The residual index for the discrepancy between measured and calculated structure factors in the present work is R = 0.0172. The Bijvoet inequality between inverse reflections, reveals good agreement with the calculated values for a large number of reflections.

The pyrochlore-related structure (trigonal P 3 1 21, a = 7.191 Å, c = 17.402 Å) proposed previously for Mn 2 Sb 2 O 7 on the basis of powder X-ray diffraction data has been confirmed and refined using neutron diffraction data. The atomic coordinates and bond lengths obtained are more precise than those reported previously: average bond lengths of 2.46 Å and 1.96 Å are consistent with Mn 2+ and Sb 5+ in 8- and 6-fold coordination respectively by O 2− . Data has been analysed by the two-stage profile decomposition method.

The structure of K 3.86 Na 5.30 H 3 O 0.84 + Fe 6 3+ O 2 (SO 4 ) 12 · 17.08 H 2 O was solved by direct methods and isotropically refined to a final R = 0.10 for 889 independent reflexions. Characteristic crystal data are: trigonal, space group P [unk], Z = 1, D m = 2.464, D x = 2.464 g cm −3 and unit-cell parameters: a = b = 9.611(3), c = 17.830(15) Å. The structure consists of big clusters of the composition [Fe 6 3+ O 2 (SO 4 ) 12 · 6 H 2 O] 4− connected in couples by means of Na and K, to form sandwich sheets. A disordered layer built up by H 3 O + and Na + cations is situated between them. There is a precise relation between the composition of this layer and the chemistry of the sandwich sheet, which appears to control the stability of the structure.

We analyse X-ray single crystal data taken at T = 393 K from the high temperature phase of KNO 2 I. Two models are used to describe the orientationally disordered NO 2 molecules: a Frenkel model made up from two sets of 24 discrete settings of the NO 2 group, and a continuous distribution model using symmetry adapted functions. Both models are compatible with anisotropic mass distributions centered around the molecular c enter o f m ass (COM) as a fixed point. We conclude from both numerical and dynamical reasons that the NO 2 disorder in KNO 2 I is dynamical i.e. that the continuous model applies in this case.

The 2-(p-nitrophenyl) thiazolidine (hereafter called 2PNPT) has medicinal importance, as the five-membered thiazolidine ring happens to be the active part of penicillin. This material is synthesised and the crystal structure has been solved. The absorption peaks pertaining to NH, NCS, aromatic C 6 H 4 and C – NO 2 have been identified from the infrared spectrum of 2PNPT. The Proton Magnetic Resonance (PMR) spectrum of the sample supports to propose the molecular structure of the compound. The 2PNPT sample (C 9 H 10 N 2 O 2 S, Mw = 210.26) crystallises in the orthorhombic space group P 2 1 2 1 2 1 , with a = 5.424(3), b = 11.537(6), c = 15.455(5) Å, V = 967.03 Å 3 , Z = 4, D cal = 1.44 g cm −3 , D mes = 1.43 g cm −3 . The crystal structure has been solved by Patterson syntheses and refined by full-matrix least-squares procedures; final values of R = 0.054 and Rw = 0.059. The phenyl ring is planar and makes an angle of 81.1° to the thiazolidine moiety omitting N atom.

The crystal structure of synthetic Ag 2 O · 2B 2 O 3 · 2H 2 O with the structural formula Ag 6 [B 12 O 18 (OH) 6 ] · 3H 2 O was determined from single-crystal X-ray diffractometer data. The compound crystallizes in the monoclinic space group P 2 1 / c with a = 1178.4(29) pm, b = 1065.4(16) pm and c = 1011.6(9) pm, β = 112.10(14)°, Z = 2 formula units and D c = 3.543 g · cm −3 . The crystal structure has been solved from 1769 observed reflections by means of direct methods and ΔF syntheses and refined by least-squares calculations to R = 5.6% and R w = 4.7%. The structure contains the new insular dodecaborate ion [B 12 O 18 (OH) 6 ] 6− ; two Ag + -ions occupy their positions statistically together with one molecule H 2 O per unit cell.

The crystals of the title compound are hexagonal, space group P 6 3 / mmc , a = 13.852(2), c = 20.107(7) Å, Z = 2. 690 independent reflexions with I ≥ 3 σ ( I ) were used for structure determination. The structure was solved by direct methods and refined by full-matrix least-squares to an R of 0.052. The cage anion [KV 15 O 36 ] 6− is nearly spherical, having D 3h symmetry. Each vanadium atom is coordinated by five oxygen atoms to form a tetragonal pyramid. Fifteen pyramids are connected to each other via corners or edges of the basal planes. A large cavity in the center is about 4 Å in free diameter. The K + ion is in the center of the cavity. The distances between K + and 21 oxygen atoms located in the interior surface of the cavity are in the range of 3.33 – 3.87 Å and the distances between K + and 15 V atoms are in the range of 3.32 – 3.53 Å. Six [(CH 3 ) 4 N] + cations around the anion form a trigonal prism.

The crystal structures of CdAl 2 S 4 , HgAl 2 S 4 , and HgGa 2 S 4 were solved and refined to R = 0.032, 0.042, and 0.046, respectively. CdAl 2 S 4 and HgGa 2 S 4 crystallize with the thiogallate type structure, space group I [unk]. The positional parameters of S are x = 0.2660(1), y = 0.2770(1), z = 0.1352(1) for CdAl 2 S 4 and x = 0.2718(3), y = 0.2675(3), z = 0.1374(1) for HgGa 2 S 4 . HgAl 2 S 4 crystallizes with space group I [unk]2 m . Hg is situated at the special site (2a) 0,0,0, Al1 at (2b) 0,0,1/2, whereas Al2 and the vacancy are randomly distributed at (4d) 0,1/2,1/4. The positional parameters for S at (8i) x , x , z are x = 0.2272(11) and z = 0.3633(8).

Single crystals of optical quality of LiNO 3 , NaNO 3 , KNO 3 , CsNO 3 , AgNO 3 and TlNO 3 have been grown from aqueous solutions. Their elastic and thermoelastic constants were determined from ultrasonic resonance frequencies of thick plates and from temperature-induced shifts of resonance frequencies. For NaNO 3 and AgNO 3 the pressure-derivatives have also been measured. A comparison of the elastic properties of the nitrates and the corresponding halides reveals close relations between them. For LiNO 3 and NaNO 3 even the temperature- and pressure-derivatives resemble those of the structurally related NaCl-type. As KNO 3 and TlNO 3 approach phase transitions at 402 K and 345 K, respectively, the temperature dependences of their elastic constants show an almost normal behaviour indicating a transition of strongly first order. With CsNO 3 an anomalous decrease of a few percent of the elastic constants between about 420 and the transition at 433 K is observed. This behaviour can be assigned to certain pretransitional fluctuations typical of transitions of partly second-order type.

Segments of the basic structures BaAl 4 , AlB 2 , W, Po, Cu 3 Au, CaF 2 or hybrids obtained combining two segments of these types are used with the mechanism of intergrowth to describe nine linear structures of binary and ternary intermetallic compounds formed by rare earth or alkaline earth metals. Such a representation allows to display relationship among the structures. All examined compounds with one exception contain AlB 2 fragments, that means rare earth or alkaline earth face-sharing trigonal prisms centred by the small atoms. Depending on the segments between which the AlB 2 fragment is comprised, the atoms centring the prisms show a different behaviour in their waist contacts.

A new molybdenum aluminophosphate MoAlP 2 O 9 has been isolated and its structure determined from X-Ray single crystal study. This tetragonal phase ( a = 8.803 Å, c = 8.697 Å), space group P 4/ ncc is isostructural with VSiP 2 O 9 . Its structure can be described in a very simple way by the assemblage of ReO 3 -type rows [MoO 3 ] ∞ with [AlP 2 O 6 ] ∞ tetrahedral columns. The MoO 6 octahedron exhibits one very short Mo — O distance (1.654 Å) characteristic of Mo(V), to be compared with other molybdenyl phosphates and silicophosphates.

The crystal structure of pyrite type PtP 2 hitherto only known from powder measurements and Weissenberg photographs was redetermined by single crystal X-ray diffractometer methods. Single crystals of PtP 2 were grown from a tin flux. The refinement of the structural parameters yielded a final R = 1.7% for 257 observed reflections ( I ⋝ 3 σ I ) and R = 4.0% for 184 ones (two experiments). The obtained structural parameter u are 0.38956(5) and 0.3896(3), respectively ( a = 569.68(2) pm, 295 K).

The crystal structure of the title compound has been determined at room temperature. The crystals are monoclinic, space group P 2 1 / c , Z = 2, with a = 7.867(2), b = 5.305(1), c = 12.574(2) Å and β = 72.73(2)°. The structure was refined to R = 0.042 for 589 observed reflections. The molecule is on an inversion center. The agreement among chemical equivalent bond lengths is generally very good, thus confirming the short carbonyl distance (1.185 Å). The crystal is built of stacks of only partially overlapping NTDA molecules along b .