Rigid five-coordinate diorganotin derivatives of oxalic acid diamides, studied by 119Sn-NMR and X-ray structural analysis

2000 ◽  
Vol 604 (2) ◽  
pp. 229-233 ◽  
Author(s):  
Rosalinda Contreras* ◽  
Victor M Jimenez-Perez ◽  
Carlos Camacho-Camacho ◽  
Marisol Güizado-Rodriguez ◽  
Bernd Wrackmeyer*
Keyword(s):  
Structural Analysis ◽  
Oxalic Acid ◽  
X Ray ◽  
119Sn Nmr ◽  
Derivatives Of

Synthese, Koordinationschemie und Ligandeneigenschaften sekundärer Phosphane R(Ar*)PH mit sperrigen aromatischen Resten - Molekülstruktur von Ph(2,4,6-iPr3C6H2)PH, (2,4,6-iPr3C6H2)2PH und ClAu[PhP(2,4,6-Bu3C6H2)H] / Synthesis, Coordination Chemistry and Ligand Properties of Secondary Phosphines R(Ar*)PH with Bulky Aromatic Substituents - Molecular Structure of Ph(2,4,6-iPr3C6H2)PH, (2,4,6-iPr3C6H2)2PH and ClAu[PhP(2,4,6-tBu3C6H2)H]

1996 ◽  
Vol 51 (8) ◽  
pp. 1183-1196 ◽  
Author(s):  
David J. Brauer ◽  
Frank Bitterer ◽  
Frank Dörrenbach ◽  
Gisbert Heßler ◽  
Othmar Stelzer ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Subsequent Reduction ◽  
Coinage Metal ◽  
X Ray ◽  
Modeling Techniques ◽  
Electronic Parameters ◽  
Bulky Ligand ◽  
Derivatives Of ◽  
Nmr Signals ◽  
Secondary Phosphines

The secondary phosphines R(Ar*)PH(R = Me, iPr, Ph, Mes, Ar*) (2a-2h) with bulky aromatic substituents Ar* (Ar* = 2,3,6-R′ 3C6H2, R′ = iPr, tBu) are obtained in good yields by reaction of RPCl2, PCl3, PBr3 or Ar*P(Cl, Br)2 with 2,4,6-tBu3C6H2Li or 2,4,6- iPr3C6H2MgBr and subsequent reduction of the intermediate halophosphines R(Ar*)PX(X = Cl, Br) with LiAlH4. The X-ray structural analysis of Ph(2,4,6-iPr3C6H2)PH (2g), space group P1, shows P-C-distances of 1.824(1) and 1.838(1)Å. The lithium derivatives of 2a-2c are monomeric in solution as indicated by the 1 :1 :1 : 1-quartet 7L i - 31P fine structure of the 31P {1H} NMR signals at low temperatures. 2a-2c and 2f-2h form Ni(0) and Fe(0) complexes (CO)3NiL (6a-6f) and Fe(CO)4L (7a-7d), respectively. The Tolman electronic parameters of the bulky ligands are almost identical. Within the series 2a-2h the spatial shielding of the P atoms has been estimated using advanced molecular modeling techniques. The bulky ligand 2c forms coinage metal complexes [C u(CH3CN)2(2c)2] [PF6] (8), Cu2Cl2(2c)2 (9) and Cl-Au(2c) (10). While 10 is monomeric in solution, in the solid state it forms pairs of head to tail oriented monomers with almost linear Cl - Au - P skeletons (Cl - Au - P 175.47(9)°) as shown by an X-ray structural analysis.

X-Ray Structural Analysis of Ester and Ether Derivatives of 4,5-endo,endo-9,10-Dimethanonaphthalene-11-ol: Evidence for π - σCO* Participation in the Ground State

2008 ◽  
Vol 61 (12) ◽  
pp. 956 ◽  
Author(s):  
Wesley Jackson ◽  
Jonathan M. White
Keyword(s):  
Structural Analysis ◽  
Weak Interaction ◽  
Ground State ◽  
System Analysis ◽  
Diels Alder ◽  
Oxygen Probe ◽  
Structural Effects ◽  
X Ray ◽  
Carbon Carbon Bond ◽  
Derivatives Of

Application of the variable oxygen probe to the polycyclic alcohol 11 and its crystalline ester and ether derivatives provides evidence for a weak interaction between the neighbouring homo-allylic π-system and the C–OR bond; there is no evidence for interaction with the remote π-system. Analysis of the carbon–carbon bond distances in 11–14 reveals structural effects consistent with the manifestation of one of the two possible retro-Diels–Alder reactions in the ground state.

Thia- and Selena-Heterocycles Containing Cycloamidine Substructures: Ring Contraction Reactions of 1,3,4-Thia-/Selenadiazines

2008 ◽  
Vol 63 (4) ◽  
pp. 415-424 ◽  
Author(s):  
Jan Fleischhauer ◽  
Rainer Beckert ◽  
David Hornig ◽  
Wolfgang Günther ◽  
Helmar Görls ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Structural Analysis ◽  
Mass Spectroscopy ◽  
Elemental Analysis ◽  
Acid Water ◽  
Dimroth Rearrangement ◽  
Ring Contraction ◽  
X Ray ◽  
Acetic Acid Water ◽  
Derivatives Of

Abstract1,3,4-Thia/selena-diazines proved to be suitable starting materials for ring contraction reactions. Treatment with acetic acid/water mixtures leads to highly substituted 1,3,4-thia/selenadiazoles. In addition, the selenadiazoles formed undergo a fast Dimroth-rearrangement to finally yield derivatives of 1,2,4-triazole. The structures of all new derivatives were confirmed by NMR experiments, mass spectroscopy, elemental analysis and X-ray structural analysis.

RNA polymerase: Preparation and structural analysis of helical polymers

1984 ◽  
Vol 42 ◽  
pp. 152-153
Author(s):  
E. Loren Buhle ◽  
Pamela Rew ◽  
Ueli Aebi
Keyword(s):  
Structural Analysis ◽  
Rna Polymerase ◽  
Molecular Level ◽  
X Ray Diffraction ◽  
Helical Polymers ◽  
X Ray ◽  
E Coli ◽  
The Past ◽  
Ordered Arrays ◽  
Low Ionic Strength

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.

The crystal and molecular structure of tris(pentamethylenedithiocarbamate) chromium(III)-chloroform (1 : 2)

1981 ◽  
Vol 46 (1) ◽  
pp. 6-19 ◽  
Author(s):  
Viktor Kettman ◽  
Ján Garaj ◽  
Jaroslav Majer
Keyword(s):  
Molecular Structure ◽  
Structural Analysis ◽  
Crystal And Molecular Structure ◽  
Analysis Method ◽  
Complex Molecules ◽  
Coordination Polyhedra ◽  
X Ray ◽  
Cell Dimensions ◽  
Crustal Density ◽  
Unit Cell Dimensions

The crystal and molecular structure of [Cr(S2CN(CH2)5)3].2 CHCl3 was found by the X-ray structural analysis method. The value R 0.090 was found for 1 131 observed independent reflections. The substance crystallizes in a space group of symmetry P212121 with the following unit cell dimensions: a = 0.8675 (6), b = 1.815(2), c = 2.155(3) nm. The experimentally observed crustal density was 1.48 Mgm-3 and the value calculated for Z = 4 was 1.51 Mgm-3. The CrS6 coordination polyhedron has the shape of a trigonally distorted octahedron, where the D3 symmetry is a approximately retained. The degree of trigonal distortion expressed as the projection of the chelate S-Cr-S angle onto the plane perpendicular to the C3 pseudo axis is Φ = 41.7° (Φ = 60° for an octahedron). The skeleton of the structure formed by the complex molecules contains channels filled with chloroform molecules. The specific type of complex-chloroform interaction consists of the formation of hydrogen bonds of the chloroform protons with the fully occupied pπ-orbitals of the sulphur atoms in the coordination polyhedra. The low stability and crystal decomposition can be explained by loss of chloroform from the channels.

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