Volume 203, Issue 2

The crystal structure of lignocaine tetrachloroferrate(III) complex, FeC 14 H 22 N 2 OCl 4 , has been determined by X-ray diffraction using Cu K α radiation. The compound crystallizes in triclinic space group P [unk] with unit cell parameters a = 8.7151(2) Å, b = 10.147(2) Å, c = 12.215(3) Å, α = 107.19(2)°, β = 106.29(2)°, γ = 92.69(2)° with V = 980.5(4) Å 3 , Z = 2, D m = 1.441 Mg · m −3 , D c = 1.463 Mg · m −3 , μ = 22.75 mm −1 . The structure was solved using 2728 reflections [ I > 2.5 σ ( I )] out of 3230 reflections by MULTAN. The final residuals are R f = 0.085 ( R w = 0.106).

(I) Ammonium hydrogen 3,3-dimethyl-cis-1,2-cyclopropanedicarboxylate (NH 4 H caronate), C 7 H 13 NO 4 , M r = 175.2, orthorhombic Pbca , a = 6.530(1) Å, b = 18.366(5) Å, c = 14.956(2) Å, V = 1793.7(6) Å 3 , Z = 8, D x = 1.290 g/cm 3 , μ = 0.10 mm −1 , F (000) = 752, wR = 0.041, R = 0.062 for 723 observed reflections [ I > 2 σ ( I )]. (II) Potassium hydrogen 3,3-dimethyl-cis-1,2-cyclopropanedicarboxylate (KH caronate) monohydrate, C 7 H 9 KO 4 · H 2 O, M r = 214.3, triclinic P [unk], a = 6.156(2) Å, b = 9.276(3) Å, c = 9.619(3) Å, α = 97.47(1)°, β = 107.94(2)°, γ = 107.29(1)°, V = 483.9(3) Å 3 , Z = 2, D x = 1.469 g/cm 3 , μ = 0.53 mm −1 , F (000) = 220, wR = 0.037, R = 0.044 for 1904 observed reflections [ I > 2 σ ( I )]. Both compounds show short intramolecular hydrogen bonds with O…O distances of 2.477(5) Å in (I) and 2.425(3) Å in (II). The present structures complement a series of comparable chelate systems. The different geometries in these chelates influence the hydrogen bond lengths (O…O) and produce distortions of the anions to different extents. These considerations, which make the tendency to form intra molecular hydrogen bonds (instead of inter molecular ones) plausible, are in accordance with predictions of the formation of intramolecular hydrogen bonds in aqueous solution by interpretation of the ratio between first and second dissociation constants of the respective dibasic acids.

The crystal structures of Li 2 CoCl 4 at room temperature and at 400° C were redetermined by X-ray measurements of a twinned trilling crystal and by neutron powder diffraction. The low-temperature polymorph Li 2 CoCl 4 oC 14 crystallizes in an ordered NaCl defect structure of SnMn 2 S 4 type (space group Cmmm , Z = 2, a = 724.1(1), b = 1027.8(1) and c = 358.69(3) pm, R I = 5.2%). Because of a pronounced pseudosymmetry this structure could only be solved by combination of several independent methods taking into account group theoretical aspects of the phase transitions involved. The high-temperature polymorph Li 2 CoCl 4 cF 56 obtained above 310°C crystallizes in the Li 2 MnBr 4 HTM I type (space group Fd [unk] m , Z = 8, a = 1043.53(7) pm (400°C), R I = 5.1 %). Whether a fully disordered deficient NaCl structure (aristotype) is reached before melting has not been fully established. The mechanisms of the phase transitions are discussed in terms of symmetry reduction and ordering of the metal ions.

N 2 H 7 I and N 2 D 7 I crystallize at room temperature in a cubic cell with symmetry Pm 3 m ( Z = 1) and a = 512.9(3) and 513.3(5) pm respectively. The cubic symmetry is caused by an orientational disorder of the N 2 H 7 + resp. N 2 D 7 + cations statistically orienting their N–N axes parallel to the three cubic axes within the crystal. Upon cooling N 2 H 7 I, the cubic phase transforms to a tetragonal one at 222 K, to an orthorhombic one at 201 K and to a monoclinic one at 130 K. N 2 D 7 I transforms at 233 K from the cubic phase directly to an orthorhombic phase and is also monoclinic below 130 K. The structure of the orthorhombic phase of N 2 D 7 I was determined using high-resolution neutron powder diffraction data collected at 160 K on the diffractometer D2B at the Institut Laue-Langevin, Grenoble. The refinements were performed using the Rietveld technique. The orthorhombic phase of N 2 D 7 I crystallizes in the space group Pcan ( Z = 4) with a = 758.4(1), b = 742.2(1) and c = 951.7(1) pm (160 K). The D 3 N–D ⋯ ND 3 + cations are ordered with respect to the N–N axis. The N–N distance is 281(1) pm. It is assumed that in the N 2 D 7 + cation an asymmetric hydrogen bond is present. The terminal ND 3 groups oscillate about their time-averaged positions. The point symmetry of the cation is close to C 3 v . One of the three deuterium atoms of each terminal ND 3 group is involved in a strong nearly linear hydrogen bond of the type N–D…I. The orthorhombic phase of N 2 H 7 I ( a = 751(1), b = 743(1), c = 958(2) pm, 202 K) very likely has the same structure. Single crystal X-ray structure investigations reveal an N–N distance of 276(5) pm. The structure of the tetragonal phase observed only with N 2 H 7 I differs from the orthorhombic one in that the hydrogen atoms of the terminal NH 3 groups do not possess fixed positions, but are rather positionally disordered around the N–N axis. Hence, no strong hydrogen bonds of the type N–H ⋯ I are formed. The space group of the tetragonal phase of N 2 H 7 I is I 4/ mcm ( Z = 4) with lattice constants a = 742(2) and c = 970(2) pm at 220 K. The N–N distance amounts to 268(6) pm.

Sodium pentaaluminum dodecaaluminogermanate (SPDAG) prepared by hydrothermal synthesis is nonstoichiometric with the approximate formula N 2+x Al 5 [Al 5+x Ge 7−x O 30 ], and x = 0.94–1.38 determined from electron microprobe measurements on compositionally-zoned crystals. The structure was determined for the average composition Na 2.90 Al 5 [Al 6.16 Ge 5.84 O 29.87 ]. SPDAG has a six-membered (sechser) double-ring structure with the space group P 6 3 / mcm , a = 9.716(3) Å, c = 14.192(3) Å, Z = 2, D x = 2.56 g · cm −3 . The structure was refined to R (unweighted) 0.021, R w (weighted) = 0.021 using 959 nonequivalent reflections. The double-ring units are linked by aluminum in octahedral coordination [Al(1), Al(2)]. Sodium occupies all four possible large cation positions; Na(1), within the cage of the double-ring, and Na(2), between double rings, are six-fold coordinated and fully occupied. Partial occupancy of Na(3) and Na(4) charge balances the additional substitution of Al in the tetrahedral position. This structure differs from the milarite-type structure of silicates in details of ring topology and the presence of linking Al(1)O 6 octahedra instead of T2O 4 tetrahedra in the latter.

The crystal structure of Pb(IO 3 ) 2 I [ Pbcn , Z = 4, a = 1670.4(3), b = 557.8(1), c = 608.3(1) pm] has been determined by single crystal X-ray diffraction. The final R is = 4.3% [number of observed (I > 3 σ I ) unique reflections 522]. Pb(IO 3 ) 2 I has a layered structure with unusually short interionic O 3 I … O distances (< 270 pm) and a stereochemically active s electron pair (contrary to other halates of lead). Because of the distorted octahedral coordination of iodine the IO stretching modes (IR and Raman spectra) are shifted on average by about 50 cm −1 to lower energies as compared to other iodates.

The crystal and molecular structure of the title compound, C 12 H 9 ClN 2 OS, has been determined from three-dimensional X-ray diffraction data. The structure is orthorhombic, Pca 2 1 , with a = 12.244(3), b = 10.664(2), c = 9.341(2) Å, and Z = 4. The structure was solved by direct methods and refined by least-squares to a final R = 0.052 for 1247 observed reflections [ Fo > 5 σ ( F o )]. The molecule consists of three parts: the phenyl ring, the thiophene ring and the central chain. Both rings are perfectly planar within the experimental error and their dimensions are as expected. The central chain is planar only approximately. The dihedral angles formed between the mean planes of the central chain and the phenyl and thiophene rings are 44.8(3)° and 12.7(2)° respectively. It seems that hydrogen bonds of N–H…O type contribute substantially to the molecular packing.

MnGa 1.4 Sc 0.6 S 4 (trigonal, P [unk] m 1, D 3 d 3 (no. 164), a = 375.2(1), c = 1222.8(4) pm, V = 0.1491(1) nm 3 , Z = 1, D x = 3.31 Mg·m −3 ) crystallizes in a layered FeGa 2 S 4 -type structure. The octahedral site of the lattice is statistically occupied by 0.6 Sc 3+ and 0.4 Mn 2+ . Gallium and the rest of the manganese is distributed over the tetrahedral sites.

The Ag distribution in the layered compound Ag 2 MnP 2 S 6 [non-conventional space group C 2/ n , a = 6.339(1) Å, b = 10.933(1) Å, c = 13.893(2) Å, β = 108.29(1)°, Z = 4, T = 300 K] is investigated as a function of temperature with the aid of single crystal X-ray data. Ag 2 MnP 2 S 6 is built of S/(Ag 2 ) 1/3 Mn 1/3 (P 2 ) 1/3 /S sandwiches, in which Mn and P 2 -pairs are distributed over the octahedral voids in an ordered triangular way; at room temperature the Ag + cations are located within the two sulfur layers of a sandwich, at the centers of the opposite triangular faces of sulfur octahedra. The Gram-Charlier expansion of the structure factor up to the fourth order is used to analyze the development of the Ag distribution with temperature. Joint probability density function maps calculated from the refined tensor elements of the atomic displacement parameter of Ag indicate that at higher temperatures the neighbouring tetrahedral sites within the gap between the sandwiches also become partly occupied. In addition they also show that the centers of the sulfur octahedra do not become occupied. The temperature dependence of the effective one-particle potential shows that the disorder in the Ag distribution is primarily static in nature. The development of the Ag distribution leads to a strengthening of the inter-sandwich bonding and to stronger distortions in the sulfur sheets. The anharmonic model is also applied to the parent phase Ag 2 ZnP 2 S 6 with improved result as compared to the split structure model.

The title adduct is a by-product of the synthesis of benzo-naphthopyrans. It crystallizes from dichloromethane/petroleum ether monoclinically in the space group P 2 1 / n with a = 1695.8(4), b = 2133.7(6), c = 935.3(2) pm, and β = 101.03(2)°.