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The asymmetric unit of the title compound, C₉H₁₀N₄O, comprises three independent mol-ecules, two pairs of which differ significantly in the rotational orientation of the azido group and one pair having very similar conformations; the N-N-C-C torsion angles are -173.9 (2), -102.7 (2) and -173.6 (2)°. In the crystal, each independent mol-ecule forms N-H⋯O hydrogen bonds with its glide-plane-related counterparts, forming zigzag chains extending along the c-axis direction.

Compounds of the solid solution series SnTe_1-x Se _x , derived from pristine SnSe and SnTe, are considered as thermoelectric lead-free materials. The crystal structure re-refinement of NaCl-type SnTe_0.73 (2)Se_0.27 (2) is based on single-crystal X-ray diffraction data and results in higher precision of the bond length [Sn-(Te,Se) = 3.0798 (3) Å] compared to a previous report on basis of powder X-ray data [Krebs & Langner (1964 ▸). Z. Anorg. Allg. Chem. 334, 37-49].

The quinoxaline portion of the title mol-ecule, C₂₁H₁₉N₅O₃, is not quite planar as indicated by a dihedral angle of 3.38 (7)° between the constituent rings. The mol-ecule is 'U-shaped', which is consolidated by an intra-molecular anti-parallel carbonyl electrostatic inter-action with C··O distances of 2.8905 (16) and 3.0221 (15) Å, in the crystal forms corrugated layers through C-H⋯O and C-H⋯N hydrogen bonds and C-H⋯π(ring) and π-stacking inter-actions.

A djurleite crystal was discovered from a natural sample originally labelled as chalcocite. The djurleite crystal under investigation has a refined composition of Cu_61.39S₃₂, thus revealing a Cu deficiency compared to the originally reported Cu₆₂S₃₂ phase [Evans (1979). Z. Kristallogr. 150, 299-320], where all atomic sites are reported to be fully occupied. In addition, the current refinement revealed a splitting of eight of the Cu sites into pairs.

The title compound, [Ir(C₈H₁₂)(C₆H₁₁N₃)(C₁₈H₃₃P)]BF₄·CH₂Cl₂, a triazole-based N-heterocyclic carbene iridium(I) cationic complex with a tetra-fluorido-borate counter-anion, crystallizes with one di-chloro-methane solvent mol-ecule per formula unit. The Ir^I atom of the cationic complex has a distorted square-planar coordination environment, defined by a bidentate cyclo-octa-1,5-diene (COD) ligand, an N-heterocyclic carbene, and a tri-cyclo-hexyl-phosphane ligand. The complex crystallizes in a C-centered monoclinic unit cell and has an unusually high number of eight formula units.

[1,4]Ditellurino[2,3-b:5,6-b']di-pyrazine represents the first reported [1,4]chalcogena[2,3-b:5,6-b']di-pyrazine containing a heavy chalcogens The asymmetric unit consists of three mol-ecules. In contrast to its sulfur analog, which is planar [Lynch et al. (1994 ▸) Cryst. Struct. Commun. 50,1470-1472], C₈H₄N₄Te₂ is folded along the Te⋯Te axis to accommodate the larger chalcogenide atoms. The dihedral angle between the two Te₂C₂ rings of the central ring is 57.9° (mean of three). C-Te bond lengths range from 2.1105 (16) Å to 2.1381 (17) Å, in good agreement with those predicted by their covalent radii. All Te atoms are involved in inter-molecular Te⋯N contacts, with distances in the range 2.894 (2) to 2.963 (2) Å. These result in a spiral supra-molecular assembly, forming helical columns.

The title compound, (C₄H₁₂N₅)₄(C₂H₇N₄O)₂[V₁₀O₂₈]·4H₂O, is a by-product obtained by reacting ammonium metavanadate(V), metformin hydro-chloride and acetic acid in the presence of sodium hypochlorite, at pH = 5. The crystal structure comprises a deca-vanadate(V) anion (V₁₀O₂₈)^6- lying on an inversion centre in space group P , while cations and solvent water mol-ecules are placed in general positions, surrounding the anion, and forming numerous N-H⋯O and O-H⋯O hydrogen bonds. Metforminium (C₄H₁₂N₅)⁺ and guanylurea (C₂H₇N₄O)⁺ cations display the expected shape. Inter-estingly, in physiology the latter cation is known to be the main metabolite of the former one. The reported structure thus supports the role of sodium hypochlorite as an oxidizing reagent being able to degrade metformin hydro-chloride to form guanylurea.

The title compound, [Nb₆Cl₁₂I₂(H₂O)₄]·8THF (THF is tetra-hydro-furan, C₄H₈O), comprises an uncharged niobium cluster unit surrounded by THF solvent mol-ecules. The edges of the {Nb₆} octa-hedron are μ ₂-coordinated by twelve chlorido ligands. Four in-plane (equatorial plane) aqua ligands and two iodido ligands coordinating above and below the plane are bound at the corners of the {Nb₆} atomic octa-hedron. O-H⋯O hydrogen bonds are formed between the aqua ligands and the THF solvent mol-ecules; one THF molecule is disordered over two positions with the major component having a site occupancy of 0.64 (2).

The imidazolidine ring in the title mol-ecule, C₁₉H₂₀N₂O₂, is slightly 'ruffled'. In the crystal, a layer structure is generated by N-H⋯O and C-H⋯O hydrogen bonds plus C-H⋯π(ring) inter-actions.

The chemical formulation of the title compound was established as trans-[PtCl{P(C₂H₅)₃(CO)}BF₄ by single-crystal X-ray analysis, in contrast to the five-coordinate tetra-fluoro-ethyl-ene complex that had been anti-cipated. The compound had been prepared by reaction of trans-PtHCl(P(C₂H₅)₃)₂ with C₂F₄ in the absence of air, and the presence of the carbonyl group was not suspected. The square-planar cations and BF₄ ^- anions are linked by C-H⋯F and C-H⋯O inter-actions into thick wavy (010) sheets. The present crystal-structure refinement is based on the original intensity data recorded in 1967.