Hans-Jürgen Meyer

Neubestimmung der Kristallstruktur von NbOCl3

NbOCl3 was obtained from a reaction of NbCl5 and Nb2O5 at 260?C. Contrary to the literature data, NbOCl3 crystallizes in the non-centrosymmetric space group P&4macr;21m as determined by single-crystal and powder X-ray diffraction data (crystal: a = b = 1089.59(6) pm, c = 394.79(2) pm, Z = 4, R1 = 0.0229, wR2 = 0.0459, powder: a = b = 1086.36(6) pm, c = 393.65(2) pm). The niobium atoms are surrounded by distorted octahedra built of four chlorine atoms and two oxygen atoms in trans positions. Two such octahedra are edge-bridged through shared chlorine atoms, forming dimers. These units are linked to each other by apical oxygen atoms forming one-dimensional Nb2Cl6O2 chains parallel [001]. Contrary to the literature data two different Nb-O distances are obtained.

Low-temperature preparation of tungsten halide clusters: Crystal structure of the adduct W5Br12 · SbBr3

Single-crystals of a new compound W5Br12 · SbBr3 (I) were isolated as a reaction product from the reduction of WBr6 with elemental antimony at 250°C. The crystal structure was determined by single-crystal X-ray diffraction analysis. The structure contains square-pyramidal tungsten clusters being linked into infinite [(W5Br8i)Br3aBr22/a-a] chains through shared W-Bra-a-W contacts of adjacent clusters. The structure of the adduct I can be viewed as an intercalation compound composed of double-layers of cluster chains alternating with mono-layers of SbBr3 molecules.

Cluster harvesting by successive reduction of a metal halide with a nonconventional reduction agent: a benefit for the exploration of metal-rich halide systems.

The preparation of thermally labile compounds is a great temptation in chemistry which requires a careful selection of reaction media and reaction conditions. With a new scanning technique denoted here as Cluster Harvesting, a whole series of metal halide compounds is detected by differential thermal analysis (DTA) in fused silica tubes and structurally characterized by X-ray powder diffraction. Experiments of the reduction of tungsten hexahalides with elemental antimony and iron are presented. A cascade of six compounds is identified during the reduction with antimony, and five compounds or phases are monitored following the reduction with iron. The crystal structure of Fe2W2Cl10 is reported, and two other phases in the Fe-W-Cl system are discussed.

Synthesis and SHG properties of two new cyanurates: Sr3(O3C3N3)2 (SCY) and Eu3(O3C3N3)2 (ECY).

The new cyanurates Sr3(O3C3N3)2 (SCY) and Eu3(O3C3N3)2 (ECY) were prepared via exothermic solid state metathesis reactions from MCl2 (M = Sr, Eu) and K(OCN) in silica tubes at 525 °C. Both structures were characterized by means of powder and single crystal X-ray diffraction, and their structures are shown to crystallize with the noncentrosymmetric space group R3c (No. 161). Infrared spectra and nonlinear optical properties (NLO) of SCY and ECY are reported in comparison to those of CCY and β-BaB2O4 (β-BBO).

Formation, Structure, and Frequency-Doubling Effect of a Modification of Strontium Cyanurate (α-SCY)

The low-temperature modification of Sr3(O3C3N3)2 was prepared and assigned as α-SCY after the high-temperature phase (now called β-SCY) and its frequency-doubling properties were reported recently. The crystal structure of α-SCY was solved and refined by single-crystal X-ray diffraction. Both modifications of SCY crystallize in noncentrosymmetric space groups, with the low-temperature phase (α-SCY) adopting the lower symmetry structure (Cc). Atomic positions in α-SCY (Cc) reveal only small deviations in comparison to those in the structure of β-SCY (R3c). The reversible phase transition between both modifications of SCY was studied by means of temperature-dependent powder X-ray diffraction. NLO measurements of both SCY modifications are reported in comparison to the commercial frequency-doubling material KTiOPO4 (KTP).

From WCl6 to WCl2: Properties of Intermediate Fe–W–Cl Phases

Phenomenological studies of WCl6 reduction with transition metal powders M = Mn, Fe, and Co have been recently reported. These reactions involve a series of reductive intercalation steps of M atoms into layered tungsten chloride arrangements, followed by exsolution of MCl2. In the series M = Fe, the presence of divalent iron is evidenced for Fe(x)WCl6, FeW2Cl10, Fe2W2Cl10, and (Fe,W)Cl2 by Mössbauer spectroscopy. Magnetic properties are reported. Bonding characteristics between tungsten atoms in edge-sharing [W2Cl10](n-) bioctahedra reveal that a double bond can be addressed to FeW2Cl10. A similar situation appears for Fe2W2Cl10, due to the localized and thus nonbonding character of the two electrons in the δ orbitals of this compound.

On the crystal structure of a new modification of 2-amino-4,6-dichloro-1,3,5-triazine

Abstract The sublimation of 2-amino-4,6-dichloro-1,3,5-triazine yielded well developed needle-shaped crystals whose X-ray-powder pattern did not match with that of the known orthorhombic compound with the space group P212121 [1]. The investigation of a needle-shaped single crystal revealed a new monoclinic modification, which crystallizes in the space group P21/c. At T = 220 K the following lattice parameters were refined: a = 8.403(1) Å, b = 12.152(1) Å, c = 13.898(2) Å and β = 123.01(1)°. The unit cell volume amounts to 1190(1) Å3 for 8 formula units.

Ca5Cl3(C2)(CBC): A Compound with a Layer Structure and an Unusual Anion Combination

Allene homologous cumulenes are not always linear! The title compound, which has now been synthesized and structurally characterized, contains a BC2 unit that is isoelectronic with CO2 and that deviates by 16° from linearity without losing the double-bond character of the B-C bonds. The BC2 unit is located in the center of a bicapped trigonal prism of calcium ions (see picture).

Cluster Harvesting in the WBr6–P System

A combined thermal scanning-X-ray diffraction (XRD) approach was performed for the WBr(6)-P system to detect and analyze phases in this system, including metal-rich phases generated with increasing amounts of elemental (red) phosphorus under partial PBr(3) release. Phases were characterized by powder XRD. A black crystalline powder of W(4)(PBr)Br(10) was obtained after reduction of WBr(6) with elemental phosphorus at 450 °C. The crystal structure of the new compound was found to be isotypic with the structure of W(4)(PCl)Cl(10) on the basis of powder XRD data. The structure of W(4)(PBr)Br(10) is represented by a cyclobutadiene-like tetranuclear tungsten cluster interconnected into a layered (W(4)(μ(4)-PBr)Br(6)(i))Br(8)/(2)(a-a) arrangement via outer bromide ligands. The μ(4)-capping bromophosphinidene ligand was verified by solid-state magic-angle spinning (31)P NMR spectroscopy.

LaSr3F5(CN2)(2): A Prototype Structure for Mixed-Valent Eu4F5(CN2)(2)

The new compound LaSr(3)F(5)(CN(2))(2) was prepared and structurally characterized as a prototype structure for the remarkably distorted mixed-valent compound Eu(4)F(5)(CN(2))(2), which contains four distinct europium ions in the structure: one Eu(3+) and three Eu(2+). Instead of repeating the given distorted structural pattern, LaSr(3)F(5)(CN(2))(2) forms a structure which can be considered as an ideal high-symmetry structure for Eu(4)F(5)(CN(2))(2), due to the occupation of La(3+) and Sr(2+) ions on one and the same crystallographic position. The crystal symmetry of this structure is an interesting issue to compare with what has been previously proposed.