Aliphatic neodymium alkoxides with sterically demanding ligands. Preparation and x-ray crystal structures of Nd2(OCH-iso-Pr2)6L2 (L = THF, py) and [Nd2(OCH-iso-Pr2)6(.mu.-DME)].infin.

1993 ◽  
Vol 32 (19) ◽  
pp. 4077-4083 ◽  
Author(s):  
David M. Barnhart ◽  
David L. Clark ◽  
John C. Huffman ◽  
Rebecca L. Vincent ◽  
John G. Watkin
Keyword(s):  
Crystal Structures ◽  
X Ray ◽  
Sterically Demanding

Synthesis and crystal structures of β-[Be(DMF)4]I2, [Be(Pyr)4]I2, [Be(NMP)4]I2 and [BeI2(Lut)2]

2020 ◽  
Vol 75 (5) ◽  
pp. 509-516 ◽  
Author(s):  
Timotheus Hohl ◽  
Torben Sinn ◽  
Constantin Hoch
Keyword(s):  
Crystal Structures ◽  
Dimethyl Formamide ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Neutral Complex ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Sterically Demanding ◽  
Methyl Pyrrolidone

AbstractFour solvent complexes of beryllium iodide were prepared by dissolving BeI2 in N,N-dimethyl formamide (DMF), pyridine (Pyr), N-methyl pyrrolidone (NMP) and 2,6-dimethyl pyridine (2,6-lutidine, Lut). Their crystal structures were established from single crystal X-ray diffraction. For [Be(DMF)4]I2 a new modification is reported (monoclinic, space group P21/c, a = 12.491(2), b = 11.593(2), c = 15.310(3) Å, β = 94.7073(6)°). In [Be(Pyr)4]I2 (monoclinic, space group C2/c, a = 17.8799(13), b = 7.6174(5), c = 18.2611(14) Å, β = 113.508(4)°) and [Be(NMP)4]I2 (orthorhombic, space group Pbca, a = 13.941(5), b = 15.754(3), c = 24.634(7) Å) homoleptic tetrahedral complex cations are formed, while the sterically demanding solvent ligand Lut yields a neutral complex with covalently bound iodine ligands [BeI2(Lut)2] (monoclinic, space group P21/c, a = 7.8492(9), b = 24.265(3), c = 27.037(3) Å, β = 97.076(3)°). Their electrochemical stability with respect to their application as beryllium electrolytes for deposition of beryllium from solution is discussed.

Zirconium alkyl and borohydride complexes stabilized by a sterically demanding anionic organic amide. The crystal structures of ZrMeL3 (2) and Zr(BH4)L3 (3) (L = (3,5-Me2Ph)N(Ad); Ad = adamantyl)

1997 ◽  
Vol 75 (11) ◽  
pp. 1494-1499 ◽  
Author(s):  
Aparna Kasani ◽  
Sandro Gambarotta ◽  
Corinne Bensimon
Keyword(s):  
Crystal Structures ◽  
Molecular Structures ◽  
Crystal Data ◽  
Lithium Amide ◽  
X Ray ◽  
X Ray Crystallography ◽  
Sterically Demanding

The lithium amide [3,5-Me2PhN(Ad)]Li•Et2O (L) reacts with ZrCl4(THF)2 to give ZrClL3. Reactions of ZrClL3 with MeLi and NaBH4 produce the corresponding ZrMeL3 (2) and Zr(BH4)L3 (3), respectively. The molecular structures of 2 and 3 were determined by X-ray crystallography. Crystal data are as follows. 2: C55H75N3Zr, FW 869.45, orthorhombic, Pcab; a = 19.2436(3) Å,b = 45.9342(4) Å, c = 21.2935(3) Å, V = 18822.2(4) Å3Z = 8; 3: C54H76BN3Zr, FW 869.25, orthorhombic; Pbc21, a = 11.5399(3) Å,b = 19.4091(4) Å, c = 20.4471(5) Å,V = 4579.72(19) Å3Z = 4. Keywords: zirconium, amide, alkyl, borohydride, structure.

scholarly journals Kristallstrukturen komplexer Metalate mit dem sterisch anspruchsvollen 1,3,5-Tri(tert-butyl)tropylium-Kation / X-Ray Crystal Structures of Complex Metallates Containing the Sterically Demanding 1,3,5-Tri(tert-butyl)tropylium Cation

2006 ◽  
Vol 61 (10) ◽  
pp. 1189-1197 ◽  
Author(s):  
Matthias Tamm ◽  
Thomas Bannenberg ◽  
Victoria Urban ◽  
Tania Pape ◽  
Olga Kataeva
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Transition Metal Complexes ◽  
Crystal Packing ◽  
Proton Donor ◽  
Close Inspection ◽  
X Ray ◽  
Tert Butyl ◽  
Sterically Demanding ◽  
Anions And Cations

The X-ray crystal structures of anionic transition metal complexes containing the sterically demanding 1,3,5-tri-tert-butyltropylium cation, [1,3,5-C7H4tBu3]+, as the compensating ion are presented. Bis(1,3,5-tri-tert-butyltropylium) hexachlorodiferrate(II), [1,3,5-C7H4tBu3]2[Fe2Cl6] (4), was obtained from the reaction of the 1,3,5-tri-tert-butyltropylium hydrogendichloride, [1,3,5- C7H4tBu3][HCl2] (3), with FeCl2, whereas the 1,3,5-tri-tert-butyltropylium tetrabromooxomolybdate( V) [1,3,5-C7H4tBu3][trans-Mo(O)Br4(CH3CN)] (7) was isolated from the reaction of the cycloheptatrienyl complex [(η7-1,3,5-C7H4tBu3)Mo(CO)2Br] (6) with elemental bromine. The crystal structures of 3, 4, 7 and 7 · CH3CN show in each case well separated anions and cations and the absence of any covalent anion-cation interactions. However, close inspection of the crystal packing reveals that the 1,3,5-tri-tert-butyltropylium cation can act as a CH-proton donor towards the counterion leading to the formation of weak C-H· · ·Cl-M and C-H· · ·O=M hydrogen bonds in 4 and in 7 and 7 ·CH3CN, respectively.

Transmission electron microscope studies in special ceramics

1978 ◽  
Vol 36 (1) ◽  
pp. 268-269
Author(s):  
A. Zangvil ◽  
L.J. Gauckler ◽  
G. Schneider ◽  
M. Rühle
Keyword(s):  
Phase Diagrams ◽  
Crystal Structures ◽  
Thin Foil ◽  
Limited Extent ◽  
Complex Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Lattice Resolution

The use of high temperature special ceramics which are usually complex materials based on oxides, nitrides, carbides and borides of silicon and aluminum, is critically dependent on their thermomechanical and other physical properties. The investigations of the phase diagrams, crystal structures and microstructural features are essential for better understanding of the macro-properties. Phase diagrams and crystal structures have been studied mainly by X-ray diffraction (XRD). Transmission electron microscopy (TEM) has contributed to this field to a very limited extent; it has been used more extensively in the study of microstructure, phase transformations and lattice defects. Often only TEM can give solutions to numerous problems in the above fields, since the various phases exist in extremely fine grains and subgrain structures; single crystals of appreciable size are often not available. Examples with some of our experimental results from two multicomponent systems are presented here. The standard ion thinning technique was used for the preparation of thin foil samples, which were then investigated with JEOL 200A and Siemens ELMISKOP 102 (for the lattice resolution work) electron microscopes.

Crystal Structures of Fragments D and Double-D from Fibrinogen and Fibrin

1999 ◽  
Vol 82 (08) ◽  
pp. 271-276 ◽  
Author(s):  
Glen Spraggon ◽  
Stephen Everse ◽  
Russell Doolittle
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Crystal Structures ◽  
Structure And Function ◽  
X Ray ◽  
Long Period ◽  
And Function

IntroductionAfter a long period of anticipation,1 the last two years have witnessed the first high-resolution x-ray structures of fragments from fibrinogen and fibrin.2-7 The results confirmed many aspects of fibrinogen structure and function that had previously been inferred from electron microscopy and biochemistry and revealed some unexpected features. Several matters have remained stubbornly unsettled, however, and much more work remains to be done. Here, we review several of the most significant findings that have accompanied the new x-ray structures and discuss some of the problems of the fibrinogen-fibrin conversion that remain unresolved. * Abbreviations: GPR—Gly-Pro-Arg-derivatives; GPRPam—Gly-Pro-Arg-Pro-amide; GHRPam—Gly-His-Arg-Pro-amide

Synthesis of Sulfoquinovose and Sulfoquinovosyl Diacylglycerides, and a Fluorogenic Substrate for Sulfoquinovosidases

2019 ◽  
Author(s):  
Yunyang Zhang ◽  
Janice Mui ◽  
Thimali Arumaperuma ◽  
James P. Lingford ◽  
ETHAN GODDARD-BORGER ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Fluorogenic Substrate ◽  
Potassium Salts ◽  
X Ray ◽  
Sulfoquinovosyl Diacylglycerol ◽  
Sodium And Potassium

<p>The sulfolipid sulfoquinovosyl diacylglycerol (SQDG) and its headgroup, the sulfosugar sulfoquinovose (SQ), are estimated to harbour up to half of all organosulfur in the biosphere. SQ is liberated from SQDG and related glycosides by the action of sulfoquinovosidases (SQases). We report a 10-step synthesis of SQDG that we apply to the preparation of saturated and unsaturated lipoforms. We also report an expeditious synthesis of SQ and (<sup>13</sup>C<sub>6</sub>)SQ, and X-ray crystal structures of sodium and potassium salts of SQ. Finally, we report the synthesis of a fluorogenic SQase substrate, methylumbelliferyl a-D-sulfoquinovoside, and examination of its cleavage kinetics by two recombinant SQases.</p>

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