Two Modifications of (TeO)(HAsO4) and its Dehydration Product (Te3O3)(AsO4)2- Three more Examples of Tellurium(IV) with a Fivefold Oxygen Coordination

Oxygen coordination to the Xe(VI) atom of XeO3 was observed in its adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone. The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction and Raman spectroscopy. Unlike solid XeO3, which detonates when mechanically or thermally shocked, the solid [(C6H5)3PO]2XeO3, [(CH3)2SO]3(XeO3)2, and (C5H5NO)3(XeO3)2 adducts are insensitive to mechanical shock, but undergo rapid deflagration when ignited by a flame. Both [(C6H5)3PO]2XeO3 and (C5H5NO)3(XeO3)2 are air-stable whereas [(CH3)2SO]3(XeO3)2 slowly decomposes over several days and [(CH3)2CO]3XeO3 undergoes adduct dissociation at room temperature. The xenon coordination sphere of [(C6H5)3PO]2XeO3 is a distorted square pyramid which provides the first example of a five-coordinate XeO3 adduct. The xenon coordination spheres of the remaining adducts are distorted octahedra comprised of three Xe---O secondary contacts that are approximately trans to the primary Xe–O bonds of XeO3. Quantum-chemical calculations were used to assess the Xe---O adduct bonds, which are predominantly electrostatic σ-hole bonds between the nucleophilic oxygen atoms of the bases and the σ-holes of the xenon atoms.

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Structural reassignment of the dehydration product of 2′-Hydroxywarfarin

Journal of Heterocyclic Chemistry ◽

10.1002/jhet.5570140232 ◽

1977 ◽

Vol 14 (2) ◽

pp. 319-320 ◽

Cited By ~ 8

Author(s):

William H. Porter ◽

William F. Trager

Keyword(s):

Dehydration Product

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Incommensurate modulation of calcium barium niobate (CBN28 and Ce:CBN28)

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768111054863 ◽

2012 ◽

Vol 68 (2) ◽

pp. 101-106 ◽

Cited By ~ 15

Author(s):

Heribert A. Graetsch ◽

Chandra Shekhar Pandey ◽

Jürgen Schreuer ◽

Manfred Burianek ◽

Manfred Mühlberg

Keyword(s):

Crystal Structures ◽

Tungsten Bronze ◽

Atomic Displacement ◽

Type Structure ◽

Formula Unit ◽

Tetragonal Tungsten Bronze ◽

First Order ◽

Oxygen Coordination ◽

Incommensurate Modulation ◽

Atomic Displacement Parameters

The incommensurately modulated crystal structures of Ca0.28Ba0.72Nb2O6 (CBN28) and Ce0.02Ca0.25Ba0.72Nb2O6 (Ce:CBN28) were refined in the supercentred setting X4bm(AA0,−AA0) of the 3 + 2-dimensional superspace group P4bm(aa½,−aa½). Both compounds are isostructural with a tetragonal tungsten bronze-type structure. The modulation of CBN28 consists of a wavy distribution of Ba and Ca atoms as well as vacancies on the incompletely occupied Me2 site with 15-fold oxygen coordination. The occupational modulation is coupled with a modulation of the atomic displacement parameters and a very weak modulation of the positional parameters of Me2. The surrounding O atoms show strong displacive modulations with amplitudes up to ca 0.2 Å owing to the cooperative tilting of the rigid NbO6 octahedra. The Me1 site with 12-fold coordination and Nb atoms are hardly affected by the modulations. Only first-order satellites were observed and the modulations are described by first-order harmonics. In Ce:CBN28 cerium appears to be located on both the Me2 and Me1 sites. Wavevectors and structural modulations are only weakly modified upon substitutional incorporation of 0.02 cerium per formula unit of calcium.

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THE STRUCTURE OF RETAMINE AND THE PARTIAL SYNTHESIS OF THE (−)-ENANTIOMORPH

Canadian Journal of Chemistry ◽

10.1139/v65-270 ◽

1965 ◽

Vol 43 (7) ◽

pp. 2012-2016 ◽

Cited By ~ 3

Author(s):

Kju Hi Shin ◽

L. Fonzes ◽

Léo Marion

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Thin Layer ◽

Thin Layer Chromatography ◽

Opposite Sign ◽

Optical Rotation ◽

Partial Synthesis ◽

Dehydration Product ◽

Layer Chromatography ◽

Nuclear Magnetic

Previous work by many authors has led to the assumption that retamine might be (+)-12-hydroxysparteine. A partial synthesis of the enantiomorph of this compound has been effected by dehydration of (+)-13-hydroxylupanine and hydroboration of the product. The dehydration product consisted of two components that were separated by thin-layer chromatography and identified by the characteristics of their nuclear magnetic resonance (n.m.r.) spectra as Δ12,13-and Δ13,14-dehydrolupanine. Hydroboration of the Δ12,13-isomer gave rise to (−)-12-hydroxy-sparteine having, in thin-layer chromatography, the same Rf value as natural retamine and the same optical rotation numerically, although of opposite sign. The synthetic base had the same infrared and n.m.r. spectra as the alkaloid and the two had superimposable Debye–Scherrer patterns. Evidence is given showing the hydroxyl to be equatorial.

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Synthesis, Crystal Structure, Luminescence and Electronic Band Structure of K2BiZr(PO4)3 Phosphate Compound

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.230.55 ◽

2015 ◽

Vol 230 ◽

pp. 55-61 ◽

Cited By ~ 2

Author(s):

Vitalii Chornii ◽

Yuriy Hizhnyi ◽

Sergiy G. Nedilko ◽

Kateryna Terebilenko ◽

I. Zatovsky ◽

...

Keyword(s):

Electronic Band Structure ◽

Spontaneous Crystallization ◽

Electronic Band ◽

Coordination Numbers ◽

Crystallization Method ◽

Oxygen Coordination ◽

Spectroscopy Studies ◽

Main Components ◽

Flapw Method ◽

First Time

The single crystals of langbeinite-related K2BiZr(PO4)3 have been obtained for the first time by spontaneous crystallization method from K-Zr-P-O-F molten system. The compound crystallizes in a space group P213 with cell parameter a = 10.30360 Å. The framework is built up from isolated Bi/ZrO6 octahedra connected together by PO4 units. For the two K+ cations two types of oxygen coordination numbers 9 and 12 are observed. The photoluminescence (PL) spectroscopy studies of K2BiZr(PO4)3 are carried out under the VUV synchrotron excitations. The electronic structure of K2BiZr(PO4)3 crystal is calculated by the FLAPW method. The PL spectra reveal two main components in the UV and visible spectral regions (peaking near 3.6 and 2.7 eV respectively). It is assumed that the <st1:address><st1:street>UV PL</st1:street></st1:address> component of K2BiZr(PO4)3 originates from transitions in ZrO6 polyhedra, while the visible one is related to Bi3+ ions in oxygen coordination.

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