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Diffraction Structure (diffraction + structure)

Distribution by Scientific Domains
Chemistry100%

Kinds of Diffraction Structure

  • x-ray diffraction structure
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    Selected Abstracts

    Bis(fluoromesityl) Palladium Complexes, Archetypes of Steric Crowding and Axial Protection by ortho Effect , Evidence for Dissociative Substitution Processes , Observation of 19F,19F Through-Space Couplings

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2004
    Camino Bartolomé
    Abstract Bisarylated complexes trans -[Pd(Fmes)2(SR2)2] [Fmes = 2,4,6-tris(trifluoromethyl)phenyl (fluoromesityl); SR2 = SMe2, tht; tht = tetrahydrothiophene] are precursors for various bisarylated fluoromesityl palladium(II) complexes by ligand-substitution reactions. Boiling under reflux in acetonitrile gives the mixed complexes trans -[Pd(Fmes)2(NCMe)(SR2)], whereas boiling under reflux in toluene leads to trans -[PdCl2L2] (L = PMe3, tBuNC, pTol-NC, 4-MePy), in the presence of neutral monodentate ligands, or to (NnBu4)[trans -Pd(Fmes)2I(SR2)] when treated with (NnBu4)I. trans -[Pd(Fmes)2(SMe2)2] reacts with bidentate ligands, also boiling under reflux in toluene, to give [Pd(Fmes)2(L,L)] [L,L = Me2bipy, 2,2, - biquinolyl, ,2N,N, -OCPy2, dppm (Ph2PCH2PPh2), dppe (Ph2PCH2CH2PPh2), pte (PhSCH2CH2SPh), ,2S,N -SPPh2Py, ,2O,N -OPPhPy2], or the bimetallic complex [Pd(Fmes)2(,-1,N:1,2,O:2,N -Py2MeCO)Pd(Fmes)(SMe2)] (characterized by X-ray diffractometry) when treated with (OH)(CH3)CPy2. The crowding associated with two Fmes groups produces several interesting features: (1) trans complexes are preferred over cis complexes, against the expected electronic preferences; (2) the low-temperature NMR spectra of several complexes, or the X-ray diffraction structure of [Pd(Fmes)2(2,2, - biquinolyl)], reveal significant structural distortions associated with steric crowding; (3) the need for boiling under reflux in the synthesis suggests a dissociative substitution mechanism, which is unknown so far for Pd; (4) some of the complexes show 19F,19F through-space couplings. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    X-ray structure and density functional theory studies of an unexpected product: trans -bis{2-[(2-cyanoethyl)iminomethyl]phenolato}copper(II)

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2009
    Maddalena Corsini
    The title compound, [Cu(C10H9N2O)2] or [CuII(CYMB)2], (I), was obtained in an attempt to reduce trans -bis(2-{[3,5-bis(trifluoromethyl)phenyl]iminomethyl}phenolato)copper(II), [Cu(TIMB)2], (II), with bis(pentamethylcyclopentadienyl)cobalt(II) [decamethylcobaltocene, Cp*2Co, (III)]. The molecular structure of (I) has the CuII centre located on an inversion centre of the C2/c space group. A density functional theory (DFT) analysis at the B3LYP/Lanl2dz(CuF);6-31G**(CHNO) level performed in order to optimize the structures of the free ligands CYMB, and TIMB,, and the metal complexes [CuI/II(CYMB)2],/0 and [CuI/II(TIMB)2],/0, reproduced well the X-ray diffraction structure and allowed us to infer the insertion of the cyanomethide anion on the 3,5-bis(trifluoromethyl)phenyl system from an evaluation of the Mulliken atomic charges and the electronic energies. [source]

    X-ray diffraction structure of a cell-wall invertase from Arabidopsis thaliana

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2006
    Maureen Verhaest
    Cell-wall invertases play crucial roles during plant development. They hydrolyse sucrose into its fructose and glucose subunits by cleavage of the ,1,,2 glycosidic bond. Here, the structure of the Arabidopsis thaliana cell-wall invertase 1 (AtcwINV1; gene accession code At3g13790) is described at a resolution of 2.15,Ĺ. The structure comprises an N-terminal fivefold ,-propeller domain followed by a C-terminal domain formed by two ,-sheets. The active site is positioned in the fivefold ,-propeller domain, containing the nucleophile Asp23 and the acid/base catalyst Glu203 of the double-displacement enzymatic reaction. The function of the C-terminal domain remains unknown. Unlike in other GH 32 family enzyme structures known to date, in AtcwINV1 the cleft formed between both domains is blocked by Asn299-linked carbohydrates. A preliminary site-directed mutagenesis experiment (Asn299Asp) removed the glycosyl chain but did not alter the activity profile of the enzyme. [source]

    Surprising Coordination Geometry Differences in CeIV - and PuIV -Maltol Complexes,

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2008
    Géza Szigethy
    Abstract As part of a study to characterize the detailed coordination behavior of PuIV, single-crystal X-ray diffraction structures have been determined for PuIV and CeIV complexes with the naturally occurring ligand maltol (3-hydroxy-2-methylpyran-4-one) and its derivative bromomaltol (5-bromo-3-hydroxy-2-methylpyran-4-one). Although CeIV is generally accepted as a structural analog for PuIV, and the maltol complexes of these two metals are isostructural, the corresponding bromomaltol complexes are strikingly different with respect to ligand orientation about the metal ion: All complexes exhibit trigonal dodecahedral coordination geometry but the CeIV,bromomaltol complex displays an uncommon ligand arrangement not found in the PuIV complex.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]