Volume 61, Issue 6

The new polyoxotungstates Cs 6n K 2n [{(Pr(H 2 O) 7 )(Pr(H 2 O) 2 )(α-SiW 11 O 39 )} 4 ] n ・ 33nH 2 O (1), (NH 4 ) 14 [{Tb(H 2 O) 3 (α 2 -P 2 W 17 O 61 )} 2 ] ・ 39H 2 O (2) and (NH 4 ) 7.33 K 2.67 Ho 1.33 [{Ho(H 2 O) 3 (α 2 - P 2 W 17 O 61 )} 2 ] ・45H 2 O (3) were synthesized in aqueous solution and characterized by IR and Raman spectroscopy, 31 P NMR spectroscopy (for 2 and 3), energy dispersive X-ray fluorescence analysis and single-crystal X-ray analysis. 1 exhibits a novel one-dimensional chain-like structure which is built up from of monovacant (α-SiW 11 O 39 ) 8 − Keggin-type anions linked by Pr(III) atoms. Half of the Pr(III) atoms are eight-coordinate (square antiprism), with four sites occupied by one anion, three by water molecules, and the eighth site by a terminal oxygen atom of a second anion. The other Pr(III) atoms are coordinated by seven water molecules and two terminal oxygen atoms of two Keggin moieties. The dimeric [{Ln(H 2 O) 3 (α 2 -P 2 W 17 O 61 )} 2 ] 14− anions in 2 (Ln = Tb) and 3 (Ln = Ho) consist of two (α 2 -P 2 W 17 O 61 ) 10− Dawson-type anions linked by two trivalent lanthanides. The lanthanides exhibit a square-antiprismatic coordination sphere which is built up by three water molecules, four terminal oxygen atoms of one Dawson-anion and one oxygen atom of the second Dawson-anion. The crystal structures of the new compounds are compared with known species and the influence of the Ln(III) ionic radii is discussed

The crystal structures of approximants RECd 6 (RE = Tb, Ho, Er, Tm and Lu) have been refined from single crystal X-ray diffraction data. This work is a continuation of a previous study of MCd 6 approximants [1] in which the different types of disorder of the central Cd 4 tetrahedra located in the dodecahedral cavities were examined. The structures of the title compounds are all similar to GdCd 6 and disorder was observed in all these compounds. There is a correlation between the anisotropic displacement parameter and the unit cell dimension

The feasibility of growing alkali halides in the hypothetical 5-5 structure type on a specially prepared substrate of LiNbO 3 has been investigated. The highest degree of steering towards this structure is achieved by growing NaBr on a LiNbO 3 (001)-surface, where the outermost layer of oxygen atoms is followed by a layer of niobium atoms. The kinetic stability, against transition into the rock salt structure, of the 5-5 structure grown on the substrate is enhanced compared to the bulk 5-5 phase, but the 5-5 structure will nevertheless still be metastable compared to the rock salt structure type that constitutes the thermodynamically stable bulk phase of NaBr under standard conditions

Fluorite-type phases in the system Y-Ta-O-N have been prepared by ammonolysis of Y-Ta-O precursors. X-ray powder patterns show unusual asymmetrical reflection profiles explained by DFT and MD methods. The anion vacancy concentration of some of these oxynitrides is similar to that of yttria-doped zirconia, commercially used as solid electrolyte in fuel cells. Hence, these compounds are interesting candidates for mixed oxygen-nitrogen superion conductors

Well-crystallized particles of cubic and tetragonal γ -Fe 2 O 3 embedded in a Pd matrix were produced besides other oxides by internal oxidation of a Pd-Fe alloy in air. Particles of tetragonal γ -Fe 2 O 3 consist of orientation domains with the c axes normal to each other. Particles of the ordered cubic γ -Fe 2 O 3 appear single crystalline in bright field and in dark field images with reflections of the basic spinel structure. In dark field images enantiomorphous domains were observed using reflections of the ordered phase. From the analysis of electron diffraction patterns in the principal zone axes the description of ordered cubic γ -Fe 2 O 3 in the enantiomorphous space groups P4 1 32/P4 3 32 follows without further presumptions. In the sequence from space group Fd3m of disordered cubic γ -Fe 2 O 3 via P4 1 32/P4 3 32 of the ordered cubic phase to the pair P4 1 2 1 2/P4 3 2 1 2 of tetragonal γ -Fe 2 O 3 a continuous group-subgroup relation can be derived. This relation shows that ordered cubic γ -Fe 2 O 3 is an intermediate phase upon ordering of vacant octahedral sites towards tetragonal γ -Fe 2 O 3

Single crystals of Sm 2 Pt 6 P 3 (a = 4.095(1), c = 45.313(9) Å ) were prepared by heating the elements in a melt of NaCl/KCl at 1100°C. The compound crystallizes with a new tetragonal type of structure (I4 1 /amd; Z = 4) consisting of units which correspond to the CaBe 2 Ge 2 type except for one significant difference: In the layer of PPt 4 tetrahedra only two of four P positions are occupied. Therefore this layer is built up by corner- instead of edge-sharing PPt 4 tetrahedra. Four of these units are stacked along [001]. Single crystals of Ca 2 Pd 3 Sb 4 (a = 4.506(1), c = 41.538(8) Å ) were obtained by reaction of the elements at 900°C. The crystal structure (I4/mmm; Z = 4) consists of two blocks. The first one has the composition CaPd 2 Sb 3 and can be derived from the CaBe 2 Ge 2 type. In the second one (formula CaPdSb) the atoms are arranged analogous to the CeMg 2 Si 2 type. Both blocks alternate along [001]

Tin, tin alloys and intermetallic tin compounds play a key role in many technologies and high-tech applications. Many of these intermetallics find application in daily life such as pewterware, bronzes, solders, fusible alloys, superconductors, capsules for wine bottles or tinplate packaging. Many of the applications are directly related to distinct stannides or intermetallic tin compounds. The crystal chemistry and chemical bonding of these materials as well as their applications are briefly reviewed

The gadolinium(III) trifluoroacetates ((CH 3 ) 2 NH 2 )[Gd(CF 3 COO) 4 ] (1), ((CH 3 ) 3 NH)[Gd(CF 3 COO) 4 (H 2 O)] (2), Gd(CF 3 COO) 3 (H2O) 3 (3) as well as Gd 2 (CF 3 COO) 6 (H 2 O) 2 (phen) 3 · C 2 H 5 OH (4) (phen = 1,10-phenanthroline) were synthesized and structurally characterized by X-ray crystallography. These compounds crystallize in the space group P1̅ (No. 2, Z = 2) (1, 2 and 4) and P 2 1 /c (No. 14, Z = 4) (3), respectively, with the following lattice constants 1: a = 884.9(2), b = 1024.9(2), c = 1173.1(2) pm, α = 105.77(2), β = 99.51(2), γ = 107.93(2)°; 2: a = 965.1(1), b = 1028.6(1), c = 1271.3(2) pm, α = 111.83(2), β = 111.33(2), γ = 90.44(2)°; 3: a = 919.6(2), b = 1890.6(4), c = 978.7(2) pm, β = 113.94(2)°; 4: a = 1286.7(8), b = 1639.3(8), c = 1712.2(9) pm, α = 62.57(6), β = 84.13(5), γ = 68.28(5)°. The compounds consist of Gd 3+ ions which are bridged by carboxylate groups either to chains (1 and 2) or to dimers (3 and 4). In addition to the Gd 3+ dimers, compound (4) also contains monomeric Gd 3+ units. The magnetic behaviour of 2 and 3 was investigated in a temperature range of 1.77 to 300 K. The magnetic data for these compounds indicate weak antiferromagnetic interactions

Single crystals of α-HgCrO 4 , β -HgCrO 4 and HgCrO 4 ・ H 2 O were obtained by reacting yellow HgO in chromic acid of various concentrations under hydrothermal conditions at 200 °C (4 d). All crystal structures were solved and refined from single crystal diffractometer data sets [α-HgCrO4: P21/n, Z = 4, a = 5.5079(8), b = 8.5266(12), c = 7.3503(10) Å , β = 94.022(3)°, 955 structure factors, R[F 2 > 2σ (F 2 )] = 0.0296; β -HgCrO 4 : Cmcm, Z = 4, a = 5.7187(9), b = 9.0169(14), c = 7.0114(11) Å, 361 structure factors, R[F 2 > 2σ (F 2 )] = 0.0275; HgCrO 4 ・ H 2 O: P1̅, Z = 2, a=5.6157(15), b =6.1115(16), c= 7.590(2) Å , α =108.850(5), β =91.666(5), γ =116.569(5)°, 1235 structure factors, R[F 2 > 2σ (F 2 )] = 0.0316]. The previously reported structure of α-HgCrO 4 has been re-determined. It contains distorted [HgO 7 ] pentagonal bipyramids in which the short bonds are directed towards the apices. The new polymorph β -HgCrO 4 adopts the CrVO 4 (β -CrPO 4 ) structure type and is composed of slightly distorted [HgO 6 ] octahedra. The previously unknown monohydrate HgCrO 4 ・ H 2 O crystallizes in an unique structure and is composed of one nearly regular [HgO 4 (H 2 O) 2 ] octahedron and one considerably distorted [HgO 6 ] octahedron. All three structures contain tetrahedral chromate anions CrO 4 2− as the second building units with average Cr-O distances of ca. 1.65 Å

The new thioantimonate(III) (C 6 N 2 H 18 )Sb 4 S 7 (C 6 N 2 H 16 = 1,6-diaminohexane) was synthesized under solvothermal conditions using Sb, S and 1,6-diaminohexane (1,6-DAH). The compound crystallizes as orange needles in the triclinic space group P1̅ with lattice parameters a = 6.9834(5), b = 11.8748(10), c = 13.6588(12) Å , α = 115.248(9), β = 100.165(9) and γ = 92.568(9)°. A central SbS 4 group shares edges with two other SbS 4 moieties forming Sb 3 S 8 units which are joined by SbS 3 pyramids sharing vertices to form a chain of alternating Sb 3 S 8 and SbS 3 units. One S atom of the SbS 3 pyramid connects neighboring chains into sheets which contain large Sb 10 S 10 heterorings. The sheets are then further connected into four atoms thick double sheets. Six edge-linked SbS4 units are condensed yielding a complex Sb 6 S 14 building block. Layers of diprotonated amines and thioantimonate( III) layers are stacked along [001] in a sandwich-like fashion with an interlayer distance of 8.46 Å . The amine layer is two molecules thick with the amines being oriented parallel to the anionic layers. The title compound represents the first example for a layered [Sb 4 S 7 ] 2− anion with a diamine as structure director. The compound is an optical semiconductor with a band-gap of about 1.9 eV

Two polymorphic modifications of dibromo-bis(acetonitrile-N)-zinc(II) have been characterized by single crystal structure analysis and X-ray powder measurements. Form I cyrstallizes in the orthorhombic space group Pnma with a = 13.101(2), b = 10.210(1), c = 6.8078(7) Å and Z = 4. The structure is composed of discrete molecular complexes in which each zinc cation is coordinated by two bromide anions and two acetonitrile ligands within distorted tetrahedra. Form II crystallizes in the orthorhombic space group Cmcm with a=8.0734(8), b=11.012(1), c=10.204(1) Å and Z =4. In this compound also discrete complexes are found and the coordination of the zinc atoms is identical to that of form I. Two bromide atoms and two acetonitrile ligands coordinate to the zinc cations within distorted tetrahedra. The packing of the discrete molecular complexes in form II is completely different form that in form I. Form I was originally prepared in the presence of 2-chloropyrazine but can also be synthesized phase pure by crystallization from acetonitrile alone. In contrast, form II was only obtained in the presence of 2-chloropyrazine if the crystallization is performed under kinetic control but it immediately transforms into form I. Crystallization experiments reveal that form I is the thermodynamically most stable form between −40 ÅC and the boiling point of acetonitrile of 80 °C, whereas form II is metastable. On storing, the thermodynamically stable form I at room temperature decomposes into zinc(II) bromide within a few hours, but in a saturated acetonitrile atmosphere it is stable over a long period. On heating form I all ligands are liberated in one step leading to zinc bromide

The title compound was prepared from the elements by arc-melting followed by annealing in silica tubes at 1270 K for one week. The crystal structure was investigated by means of X-ray single crystal diffraction: space group P4/mbm, a = 5.366(1), c = 3.690(1) Å , Z = 2, R1 = 0.010, wR 2 = 0.022 for 245 unique reflections with Io > 2σ (I o ) and 12 refined parameters. Group-subgroup relationships of MB 6 and MB 2 C 2 structure models are discussed

Solid-state phase equilibria in the Sm-Ni-As system have been established using X-ray diffraction, scanning electron microscopy and electron probe microanalysis. The samarium-poor region up to 33 at. % Sm was studied at 1170 K, whereas the Sm-rich corner, due to the generally lower melting points, was investigated at 770 K. Six ternary compounds were isolated, among which two have been structurally characterized. The hexagonal structure of SmNiAs (SrPtSb-type) was solved from X-ray single crystal data: space group 6̅m2, a = 4.0904(3), c = 3.8957(4) Å , Z = 1, R1 = 0.0221, wR2 = 0.0224 for 134 unique reflections with I o > 2σ (I o ) and 9 variable parameters. The crystal structure of Sm 6 Ni 15 As 10 (Tb 6 Ni 15 As 10 -type) was determined from X-ray powder diffraction data: full profile refinement, space group P6 3 /m, a = 17.0632(4), c = 3.9526(1) Å , Z = 2, RB = 0.079, R p = 0.138

In 2 Ti 6 (PO 4 ) 6 [Si 2 O(PO 4 ) 6 ] has been obtained by heating (1100 °C) stoichiometric amounts of In 2 O 3 , SiP 2 O 7 , TiP 2 O 7 , and TiO 2 in air. Colourless crystals of the phosphate-silicophosphate suitable for a single crystal structure investigation have been grown by chemical vapour transport (1000°C → 900°C, mixture of 70 mg PtCl 2 and 3.5 mg TiP as transport agent). In 2 Ti 6 (PO 4 ) 6 [Si 2 O(PO 4 ) 6 ] adopts its own structure type (R3̅ (No. 148), Z = 3, a = 8.4380(10) Å , c = 44.295(1) Å , 1809 independent reflections, 109 variables, R1 = 0.044, wR2 = 0.112). The crystal structure represents a hybride built up from alternating layers (⟂ to the c-axis) of the NASICON structure-type and those showing the structure of silicophosphates M 4 [Si 2 O(PO 4 ) 6 ]. Isolated heteropolyanions [Si 2 O(PO 4 ) 6 ] 12− and double-octahedra [In III Ti IV O 9 ] occur as coordination polyhedra besides isolated octahedra [Ti IV O 6 ] and tetrahedral phosphate groups. The results of 29 Si and 31 P-MAS-NMR studies are in agreement with one crystallographically independent site for silicon and two sites for phosphorus. The phosphorus resonances can be related to the two sites by 2-dimensional cross-polarisation experiments, by the anisotropies of their chemical shifts, and by the observed line widths. All criteria lead to the same assignment. Substitution of In3+ by several trivalent transition metal ions leads to phosphate-silicophosphates M 2 Ti 6 (PO 4 ) 6 [Si 2 O(PO 4 ) 6 ] (M = Ti 3+ , V 3+ , Cr 3+ , Fe 3+ )

A further example of the class of Heusler compounds is presented. Co 2 CrIn is L2 1 ordered (face centered cubic, space group Fm3̅m) with a lattice constant of a = 6.0596(2) Å . The crystal structure was determined from powder diffraction data by means of the Rietveld method. The magnetic properties of Co 2 CrIn were measured by means of SQUID magnetometry. The material turns out to be a soft ferromagnet with a saturation moment of 1.2 μ B at 5 K

As part of our synthetic efforts for new triplesalen derivatives, we reacted 2,4,6-triacetyl- 1,3,5-trihydroxybenzene (1) with excess Cu(ClO 4 ) 2 · 6H 2 O, imidazole, and ethylenediamine. However, not the triple ketimine derivative was formed but the mononuclear CuII complex [LCu II (ImH)]ClO 4 · 0.5EtOH · 0.5H 2 O (HL = 6-(1-(2-aminoethylimino)ethyl)-2,4-diacetyl-1,3,5-trihydroxybenzene) with only one ketimine function. This complex forms a one-dimensional coordination polymer in the solid state through the apical binding of a keto-oxygen atom of one cation to the Cu II ion of a neighboring cation. Magnetic measurements reveal the presence of weak antiferromagnetic intra-chain interactions

[{Hg(CF 3 ) 2 }(ThpH)(H 2 O)](H 2 O) (1), [{Hg 4 (Thp) 4 }(ClO 4 ) 4 (H 2 O) 8 ](H 2 O) 4 (2), [{Hg(ThpH) 2 } (NO 3 )](NO 3 ) (3) and {Hg(Thp)Cl}(H 2 O) (4) (ThpH = theophylline, C 7 H 8 N 4 O 2 ) have been synthesized by slow evaporation of aqueous solutions of the mercuric salts Hg(CF 3 ) 2 , Hg(ClO 4 ) 2 , Hg(NO 3 ) 2 , or HgCl 2 and theophylline. Their crystal structures were determined on the basis of single crystal X-ray data. The coordination polymers 1 and 2 crystallize with triclinic symmetry, P1̅ (no. 2), with a = 468.8(2), b = 1256.4(5), c = 1445.5(6) pm, α = 67.15(3), β = 89.21(3), γ = 89.40(3)° and a = 833.6(1), b = 1862.7(2), c = 2182.9(2) pm, α = 111.61(1), β = 90.98(1), γ = 95.51(1)°, respectively. 3 and 4 crystallize with monoclinic symmetry, Pc (no. 7), a =1194.1(1), b=1258.8(2), c=735.5(2) pm, β =96.96(2)° and P21/n (no. 14), a=1069.0(2), b =911.6(1), c=1089.9(2) pm and β = 96.87(2)°. In 1 the theophylline molecules are non-coordinating to mercury and leave the Hg(CF 3 ) 2 molecule unchanged. Only weak electrostatic attractions to one keto-oxygen atom of theophylline and one water molecule hold this co-crystallisate together. In 2, the theophyllinate anion, Thp − , strongly coordinates with both N(7) and N(9) to Hg II forming a large ring with eight Hg atoms that incorporates the water molecules. One sort of nitrate ions in 3 is weakly attached to Hg II with the theophylline molecules still bound strongly through N(9). The chloride ligand and the theophyllinate ion seem to have the same strengths as ligands in 4 as they are both attached to Hg II with the shortest distances possible

Single crystals of the lanthanide(III) thiophosphates(V) with the composition M[PS 4 ] (M = La-Nd, Sm, Gd-Er) are formed within seven days at 950 °C by oxidation of the lanthanide metals and red phosphorus with sulfur (molar ratio: 1 : 1 : 4) in evacuated silica tubes without using any flux to avoid the entrapment of e. g. alkali metal cations. Their crystal structure (tetragonal, I4 1 /acd, Z = 16; e. g. La[PS 4 ]: a = 1098,97(5); c = 1953,26(9) pm and Er[PS 4 ]: a = 1062,41(5); c = 1892,38(9) pm for the borderline representatives discussed here) is built up by a distorted cubic closest packing of discrete [PS 4 ] 3− tetrahedra (d(P 5+ -S 2− ) = 203 - 204 pm; ∢(S-P-S) = 107 - 116°) where the M 3+ cations are situated in one half of the tetrahedral interstices, the same way as S 2− in the Pt 2+ arrangement of the cooperite-type PtS structure. Therefore an eightfold sulfur coordination for both crystallographically independent M 3+ cations results in the shape of a trigonal dodecahedron. The 31 P-MAS-NMR spectra of La[PS 4 ], Nd[PS 4 ], Gd[PS 4 ], and Er[PS 4 ] are reported and discussed