Band 189, Heft 1-2

The Mg – Sc warwickite, MgScOBO 3 , is an example of a normal orthorhombic warwickite [ Pnam , a = 9.490(1), b = 9.422(1), c = 3.2189(4) Å and Z = 4]. The structure has been refined to an R value of 0.043, using the 258 X-ray reflection intensities with I > 3 · σ ( I ) and sin θ / λ ≤ 0.63 Å −1 . The ratios of divalent to trivalent ions (Mg 2+ :Sc 3+ ) at the two different metal sites are about 1:3 and 3:1, respectively. The investigation yields improved structural data for the common warwickite structure type. The Mg – Mn warwickite, Mg 0.76 Mn 1.24 OBO 3 , represents the first example of a distorted warwickite structure [ P 2 1 / a , a = 9.370(2), b = 9.279(2), c = 3.181(1) Å, β = 85.65(2)° and Z = 4]. The derived structural model has been refined to an R value of 0.048 for the 385 X-ray reflection intensities with I > 3 · σ ( I ) and sin θ / λ ≤ 0.65 Å −1 . The lowering of the symmetry, from orthorhombic for normal warwickites to monoclinic, is apparently due to structural effects caused by the Mn 3+ ions. The coordination octahedra around the main Mn 3+ sites are elongated with four shorter coplanar Mn – O bonds of 1.88 to 1.99 Å and two longer ones of 2.25 and 2.34 Å. The distributions of divalent and trivalent ions in the metal positions are similar to those in common warwickites.

Cupric chloride dihydrate CuCl 2 · 2H 2 O crystals are in the space group Pbmn with a = 7.4141(4), b = 8.0886(5), c = 3.7458(3) Å and z = 2. The O – H bond lengths of 0.82(4) and the hydrogen positions are consistent with neutron diffraction, and infrared determinations but not the proton resonance interpretation.

The chemical preparation and the crystal structure of Ag 6 P 6 O 18 · H 2 O are reported. The title compound is trigonal ( R [unk]) with a = 14.807(10) Å, c = 6.597(7) Å ( a rh = 8.827 Å, α rh = 114.01°), V = 1257(3) Å 3 , Z = 3, M w = 1139.05 amu and D x = 4.515 g cm −3 . The structure has been solved using 1073 independent data with a final R value of 0.035. The P 6 O 18 anions have [unk] symmetry. They alternate along the [unk] axis with rings of six loosely bounded silver atoms. Each Ag 6 ring is connected to its six neighbours by a short Ag – Ag distance (3.003 Å).

The microstructure of a rapidly quenched Mn 4 Si alloy has been studied by EDP and HREM. The 37° rotation twins are generated from the metastable Mn 12 Si 5 phase while the 45° microdomain can not be explained by the same Mn 12 Si 5 phase as mentioned previously but it is found to be related to the β -Mn structure.

The structures of two synthetic oxyborates, the magnesium – manganese ludwigite Mg 1.93 Mn 1.07 O 2 BO 3 and the pure cobalt ludwigite Co 3 O 2 BO 3 have been investigated by single crystal X-ray diffraction techniques. The space group symmetries of both borates is Pbam , Z = 4. The unit cell dimensions are a = 9.202(2), b = 12.532(2) and c = 2.993(1) Å for the Mg – Mn borate, and a = 9.275(1), b = 12.146(1) and c = 3.0265(3) Å for the Co borate. The structural model of the Mg – Mn ludwigite has been refined versus the 645 most significant [ I > 3 σ ( I )] reflections with sin ( θ )/ λ ≤ 1.0 Å −1 to an R -value of 0.035. The results indicate the composition Mg 1.93(2) Mn 1.07(2) BO 5 . The structural model of the Co ludwigite has been refined versus the 670 most significant [ I > 3 σ ( I )] reflections with sin ( θ )/ λ ≤ 0.9 Å −1 to an R -value of 0.038. The structures obtained are well ordered and have indicated metal ion charge distributions in agreement with those found in other members of the pinakiolite family. Due to the differences in the X-ray scattering powers of the Mg and Mn atoms the scheme of the cation ordering in the Mg – Mn ludwigite could be experimentally obtained. As indicated by i.a. estimated bond valence distributions this scheme is possibly also valid for the Co ludwigite.

Five calderite-andradite garnets from Otjosondu, Namibia, were studied chemically and by optical absorption and Mössbauer spectroscopy. The combined results of chemical analyses and Mössbauer and optical absorption spectroscopy make small amounts of octahedral Mn 3+ likely, corresponding to up to 4.8 mol% of the blythite endmember, Mn 3 2+ Mn 2 3+ Si 3 O 12 .

The crystal structure of the title compound (BSPDIM hereafter) was determined from three-dimensional data of 2540 reflexions measured on a computer-controlled Philips PW 1100 diffractometer. The compound is orthorhombic with space group P 2 1 2 1 2 1 , and cell dimensions a = 17.950(2) Å, b = 13.128(1) Å, c = 6.9816(9) Å, Z = 4. The structure was solved by direct and Patterson methods and the positional and thermal parameters were refined by full-matrix least-squares calculations. The final R value was 0.042 ( wR = 0.048). In BSPDIM the two phenylsulfonyl groups are arranged so as to minimize the steric hindrance of their O atoms. There are significant deviations from the geometry of the so far known sulfonyl groups.

The crystal and molecular structures of two 5(4H)-oxazolones related to α , β -unsaturated amino acids have been determined from three-dimensional X-ray data. C 12 H 11 NO 2 (1a) is orthorhombic, space group Pbca , Z = 8, a = 7.629(2) Å, b = 14.944(3) Å, c = 17.802(3) Å. C 17 H 13 NO 2 (1b) is monoclinic, space group P 2 1 / n , Z = 8, a = 19.176(3) Å, b = 7.578(2) Å, c = 18.703(3) Å, β = 94.98(5)°. The investigation of this series of “Z” 5(4H)-oxazolones having tetra-substituted exocyclic double bond provides, by comparison with studies of analogous systems, information on the conformational flexibility of α , β -unsaturated amino acid derivatives. The main peculiarity is the presence of an accepting nitrogen atom instead of an NH group. This allows fully planar conformations, at least to compounds having trisubstituted (“Z” or “E”) exocyclic double bond systems. The 1 H-NMR spectra are also discussed.

BaCuInF 7 is tetragonal [space group I 4 1 / amd , a = 6.843(1) Å, c = 12.001(3) Å, Z = 4]. Its room temperature crystal structure was solved from 327 unique reflections to R = 0.035. The 8 c sites of the structure are statistically occupied by both copper and indium ions in octahedral coordination. The three-dimensional network is built up from infinite chains of edge-sharing octahedra. These rutile-like chains lie along the a and b axes and form a four-layer tetragonal packing. Barium ions (eightfold coordinated) ensure also a three-dimensional subnetwork described as a defect fluorite structure in the tunnels of which octahedral chains are inserted. The original topology is discussed in terms of scale of disorder since it allows a strict cationic ordering in a chain and a disorder between two chains.

The crystal structure of 5-hydroxy-7-methoxyflavanone has been determined by single crystal X-ray analysis. The crystals are orthorhombic, a = 15.835(3), b = 6.897(2), c = 25.064(5) Å, space group Pbca , Z = 8. The structure was refined to R = 0.063 and R w = 0.062 by full-matrix least-squares methods, using 1133 independent reflections measured with a single-crystal diffractometer. The methoxy group is slightly twisted. The chromon ring system has distorted half-chair conformation, and makes an angle of 71.5(2)° with the plane of the phenyl ring.

P. Debye ideas of equal a priori distance statistics in liquids were compared with M. v. Laue's ideas of the three-dimensional lattice and led to the inhomogeneous lattice of paracrystals. Their distortions produce a tangential enthalpy A o g 2 . A N 3 -lattice cube has an enthalpy ΔG = 6 N 2 σ / d + N 3 ΔG v + 3/2 N 4 A o g 2 . Its minimum Ng 2 = α * 2 = 1/2| ΔG v / A o |(1 + [unk]); β = 32( σ / d ) A o g 2 / ΔG v 2 defines the equilibrium state of N . α * has a value of 0.15 ± 0.05 according to the values of volume- and tangential enthalpies ΔG v (<0) and A o (>0). The parameter g , the relative distance fluctuation of the distance d of bearing netplanes, explains the state of aggregation of the samples (liquid, solid, amorphous, liquid crystal a.s.o.).

Nesper and von Schnering published in 1983 a valence rule which applies to tetrahedral structures or structures with tetrahedral anion partial structures with vacant structure sites. This rule is useful to correlate the number of available valence electrons with the number of available vacant structure sites. It is shown here that this valence rule, contrary to the original assumption, can be derived from the general tetrahedral structure equation.

The crystal structure of 9,10-dimethylphenanthrene, C 16 H 14 , at room temperature, has been determined by direct methods and refined by least-squares to R = 0.030 over 554 independent reflections measured by diffractometer from a single crystal. Two molecules crystallise in a monoclinic unit cell, a = 9.103(3) Å, b = 5.454(2) Å, c = 11.666(3) Å, β = 104.27(2)°, in space group P 2 1 . Carbon atoms of each ring are planar to within 0.01 Å and adjacent ring planes are inclined at 1°. Methyl carbons C(15) and C(16) lie respectively 0.06 and 0.04 Å above and below the mean molecular plane of carbon atoms; this plane also contains the non-methyl hydrogen atoms to within 0.1 Å. Carbon – carbon bond lengths are C(12) – C(13) = 1.444(3) Å at the bay and C(9) – C(10) = 1.356(4) Å at the substituted K region.

The crystal structure of Zr 2 P has been determined and refined using single crystal X-ray diffractometer data. This compound crystallizes in space group Cmmm (No. 65). There are 36 formula units in the unit cell which has the dimensions a = 29.5099(8) Å, b = 19.0634(7) Å and c = 3.6076(1) Å. Final conventional R = 0.019 for 1711 reflexions and 91 parameters. Zr 2 P represents a new structure type which can be described in terms of interconnected Zr 6 P triangular prisms with the phosphorus atom at the centre and the six zirconium atoms at the corners. Additional zirconium atoms are accommodated in somewhat distorted cubic holes formed between the prisms. The zirconium atoms have coordination numbers between 13 and 16 and are surrounded by 10 – 12 zirconium atoms and 2 – 5 phosphorus atoms.

The title compound CuN 2 O 2 C 16 H 16 [Cu(PP) 2 ] crystallizes in the triclinic system, space group P [unk], with a = 10.667(4) Å, b = 10.553(4) Å, c = 9.964(4) Å, α = 105.2°, β = 97.8°, γ = 87.9° { σ = 0.2°), Z = 3. The structure which consists of trimers of CuN 2 O 2 C 16 H 16 exhibits hexa - and penta -coordinated copper atoms. The crystal structure has been refined to R = 0.038 for 2268 observed reflections.

The crystal structures of the isotypic orthorhombic alkaline earth and lead halates Ba(ClO 3 ) 2 , Ba(BrO 3 ) 2 II, and Pb(ClO 3 ) 2 [Sr(ClO 3 ) 2 -type, oF 72, Fdd 2, Z = 8] were determined by single crystal X-ray diffraction data. The final R values (number of observed unique reflections) are 0.033(854), 0.067(853), and 0.051(720). The data obtained are compared with those of Sr(ClO 3 ) 2 and discussed in terms of metal oxygen coordination and distortion of the halate ions, respectively. A stereochemical effect of the lone-pair of the lead ion is not observed.

The crystal structure of [CN 3 H 6 ] 2 [Fe(CN) 5 NO] and Ba[Fe(CN) 5 -NO] · 3H 2 O has been determined at 293 K by X-ray diffraction methods. Guanidinium nitroprusside crystallizes in space group Pnma with a 1 = 8.943(1), a 2 = 10.240(2), a 3 = 16.143(2) Å, Z = 4, D m = 1.511(2), D c = 1.512 g/cm 3 . The space group of barium nitroprusside trihydrate is Pbcm with a 1 = 7.610(1), a 2 = 19.389(6), a 3 = 8.628(1) Å, Z = 4, D m = 2.121(2), D c = 2.13 g/cm 3 . Both structures have been solved by direct methods and refined by least-squares calculations to a final R -value of 0.036 with 1055 reflections for [CN 3 H 6 ] 2 [Fe(CN) 5 NO] and R = 0.017 with 1518 reflections for Ba[Fe(CN) 5 NO] · 3H 2 O. In both structures the bonding is mainly effectuated by dominant ionic interactions between nitroprusside anions and the corresponding cations. The barium ion is eightfold coordinated by 5 nitrogen atoms of CN-groups and 3 water molecules. There are no other contacts which range within the usually observed van der Waals distances. The Fe-NO-axes are aligned almost parallel and antiparallel to the a 3 -axis (guanidinium nitroprusside) and a 2 -axis (barium nitroprusside trihydrate).

The crystal structure of Zr 7 P 4 has been refined using single crystal methods. The structure is described on a monoclinic unit cell (space group C2 / m ) with a = 15.814(1) Å, b = 3.6053(3) Å, c = 14.738(1) Å, β = 104.843(8)° and Z = 4. Final conventional R = 0.018 for 1303 reflexions and 69 parameters. The results verify that this compound is isotypic with Nb 7 P 4 .