A pair of diastereomeric dinuclear complexes, [Tp′(CO)BrW{μ-η2-C,C′-κ2-S,P-C2(PPh2)S}Ru(η5-C5H5)(PPh3)], in which W and Ru are bridged by a phosphinyl(thiolato)alkyne in a side-on carbon P,S-chelate coordination mode, were synthesized, separated and fully characterized. Even though the isomers are similar in their spectroscopic properties and redox potentials, the like-isomer is oxidized at W while the unlike-isomer is oxidized at Ru, which is proven by IR, NIR and EPR-spectroscopy supported by spectro-electrochemistry and computational methods. The second oxidation of the complexes was shown to take place at the metal left unaffected in the first redox step. Finally, the tipping point could be realized in the unlike isomer of the electronically tuned thiophenolate congener [Tp′(CO)(PhS)W{μ-η2-C,C′-κ2-S,P-C2(PPh2)S}Ru(η5-C5H5)-(PPh3)], in which valence trapped WIII/RuII and WII/RuIII cationic species are at equilibrium. 相似文献
The NMR pulse sequence CODEX (centerband-only detection of exchange) is a widely used method to report on the number of magnetically inequivalent spins that exchange magnetization via spin diffusion. For crystals, this rules out certain symmetries, and the rate of equilibration is sensitive to distances. Here we show that for 13C CODEX, consideration of natural abundance spins is necessary for crystals of high complexity, demonstrated here with the amino acid phenylalanine. The NMR data rule out the C2 space group that was originally reported for phenylalanine, and are only consistent with a larger unit cell containing eight magnetically inequivalent molecules. Such an expanded cell was recently described based on single crystal data. The large unit cell dictates the use of long spin diffusion times of more than 200 seconds, in order to equilibrate over the entire unit cell volume of 1622 Å3. 相似文献
Mr = 353.9, monoclinic, P 21/c, a = 11.371(4), b = 11.391(5), c = 14.699(11) Å, β = = 97.78(2)0, Z = 4, V = 1888.6(6) Å3, Dx = 1.28 Mgm−3, final R = 0.052 for 2360 independent reflections excluding those with |F0| < 5 σ(F0). Intensities were measured with an automatic diffractometer. The PN C- part of the molecule is nearly coplanar with the pyridinring (torsion angle 6.4°). The P atom and the N(2) atom of the pyridinring overlap with their van der Waals spheres and have nearly the position with the maximum of steric hindrance. This conformation of the molecule is the consequence of a conjugation between the Ph3P=N-group and the N-standing pyridine ring as well as of an attraction between the P atom and the N(2) atom. 相似文献
Mr = 218.9, monoclinic, P 21/c, a = 6.870(1), b = 10.824(2), c = 11.337(2) Å, β = = 94.59(2)0, Z = 4, V = 840.5(3) Å3, Dx = 1.73 Mgm−3. Final R = 0.033 for 2648 independent reflections, excluding those with |F0| < 3σ(F0). Intensities were measured with an automatic diffractometer. This organophosphorous compound is characterized by two P C bonds. Four symmetrically independent intermolecular hydrogen bonds determine the threedimensional packing of the molecules and the unique chemical properties of the campound. 相似文献
The α,ω-dihaloalcanes could serve as model compounds for polyethylenes in further studies of infrared and Raman-spectra. The 1,12-dibromododecane, belonging to this class of compounds, has the monoclinic space group P 21/a with the cell parameters a = 24.8 Å, b = 5.40 Å, c = 5.50 Å, β = 99°, Z = 2. The preparation of crystals was very difficult. The crystal finally used gives only few and bad X-ray data measured by film method (equiinclination Weissenberg). Therefore the accuracy of the structure determination is not high, but the result is reliable and has model character for related compounds. All molecules are ordered with their long molecular axes parallel to the (401) planes of the unit cell. There are alternating plane layers of bromine atoms on the one hand and aliphatic parts of the molecules on the other hand, both parallel to the (100)-planes. This molecular arrangement explains well the spectroscopic and crystal optical properties of the structure and also of related compounds like 1,10-dibromodecane and 1,18-dibromooctadecane. 相似文献
Both title compounds crystallize in the orthorhombic space group Pnma with 4 formular units in the unit cell. The lattice parameters are: [C26H26O5N5Co], a = 8.589(4), b = 19.395(3), and c = 14.850(3) Å;[C26H28O4N4], a = 8.413(7), b = 19.166(4), and c = 14.807(28) Å. The crystal structures have been determined by direct methods and refined by full-matrix least square calculations. The ligands have a pronounced saddle-shaped conformation in each structure because of interactions of the methyl groups with the benzene rings. The overall conformations of the neutral ligand and the cobalt complex are remarkably similar. 相似文献
The crystal structures of pyrene and substituted and complexed derivatives of pyrene have been investigated by X-ray and neutron diffraction. The geometry of the pyrene skeleton has been determined experimentally with high accuracy and calculated by quantum chemical methods. In the cases reported in the literature and cited here the pyrene skeleton has the molecular symmetry mmm or mm2 with values for the bond lengths of the six symmetrically independent bondsa, b, c, d, e, f differing significantly in the limits of error. Mean values of a number of experimental and theoretical bond lengths are given and can be considered as standard values for the mm2 symmetric pyrene skeleton. In the case of substitution of the pyrene in 3-position with a polar heterocyclic molecule of the azomethine-imine type the mm2 symmetry vanishes, a C–H ... N intramolecular hydrogen bond arises and the directly neighbouring pyrene units are not packed parallel with their planes to each other, but they are considerably tilted. Relatively narrow intermolekular C-C contacts, 3.314 and 3.368 Å, have been observed. The conclusion is drawn that the asymmetry of the pyrene molecule and a tilt of directly neighbouring pyrene units in the crystal packing can be induced by substitution e. g. with suitable polar heterocycles.
Using X-ray crystal structure analysis of the title compound the positions of all the atoms (including all H atoms) in the monoclinic unit cell with the parameters a = 13.900 Å, b = 5.138 Å, c = 17.956 Å and β = 91.05° and the space group P 21/n were localized. The existence of an intramolecular N—H(N)…︁ O(1)-bridge was inferred, whose H-bridge acceptor predominantly is the π-electron density of the carbonyl group. At the same time the H(N) atom participates in the intermolecular bridge N H(N)…︁ O′(1) to the symmetry-equivalent neighbouring molecule. H-bridge-like interactions of the two phenyl hydrogen atoms H(6) and H(15) to the carbonyl oxygen O(2) have also been inferred from the torsion angles. 相似文献