Results 1 - 10 of 49381
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[en] Nucleophilic additions of water-soluble phosphines on α-alcynic acids afford new vinylphosphonium salts which are easily transformed into specifically deuteriated olefins or phosphine oxides by using sequentially H2O or D2O. (author)
[en] A series of organotin complexes was prepared involving phosphines bonded to the organotin moiety. The series include derivatives of SnClxPh4-x (where x varied from zero to four with the phosphines Ph3P, (Ph2P)CH2, (Ph2P)2(CH2)2, cis-(Ph2P)CH2, and CH3C(CH2PPh2)3. A host of new complexes was obtained, showing different stoichiometries, bonding modes, and coordination numbers around the tin atom. These complexes were characterized by several different chemical and physical methods. The 119Sn Moessbauer parameters varied differently. Whereas isomer shift values did not great variation for each group of complexs with the same organotin parent (SnClxPh4-x), reflecting a small change in s charge distribution on the Sn atom upon complexation, quadrupole splitting results varied widely, however, when the parent organotin compound was wholly symmetric (SnCl4 and SnPPh4), the complexes also tended to show quadrupole splitting values approaching zero. (author)
[en] The conformations of a series of organophosphine oxides, OP(CH_3)_2R, where R = methyl, ethyl, isopropyl, tert-butyl, vinyl, and phenyl, are predicted using the MP2/cc-pVTZ level of theory. Comparison of potential energy surfaces for rotation about P-C bonds with crystal structure data reveals a strong correlation between predicted location and energetics of minima and histograms of dihedral angle distributions observed in the solid state. In addition, the most stable conformers are those that minimize the extent of steric repulsion between adjacent rotor substituents, and the torsional barriers tend to increase with the steric bulk of the rotating alkyl group. MM3 force field parameters were adjusted to fit the MP2 results, providing a fast and accurate model for predicting organophosphine oxides shapes - an essential part of understanding the chemistry of these compounds. As a result, the predictive power of the modified MM3 model was tested against MP2/cc-pVTZ conformations for triethylphosphine oxide, OP(CH_2CH_3)_3, and triphenylphosphine oxide, OP(Ph)_3
[en] Two tetravalent uranium compounds have been characterized. The structure of a new uranium(IV) phosphonate, U(O3PC6H5)2, has been solved from laboratory X-ray powder diffraction data by using ab initio methodology, U(O3PC6H5)2 crystallizes in the space group Cw/m with a = 9.4559(7) Angstrom, b = 5.6769(5) Angstrom, c = 14.9687(12) Angstrom, Β = 96.539(5) Angstrom, V = 798.3(1) Angstrom 3, Z=2. The reliability factors were RWP = 8.0%, Rp = 6.04%, and RF = 3.0%. The structure is lamellar, and the framework of the U(O3P)2 layers is similar to that of the α-Zr(HOP4)2 · H2O and the phosphonate group in Zr(O3PC6H5)2. The phenyl groups are located in the interlamellar space, being inclined 10 degrees to the c-axis. The phenyl rings are tilted out 53 degrees from the ac plane, and they are disordered. The authors have also characterized this compound by UV-VIS-IR spectroscopies and thermal analysis. The thermal decomposition product is uranium(IV) pyro phosphate. This compound was identified through its X-ray powder diffraction pattern. UP2O7 crystallizes in the Pa3 space group (a = 8.6311(2) Angstrom, V = 642.99(4) Angstrom 3,Z=4). The structure belongs to the cubic ZrP2O7-type structure. The reliability factors were RWP = 11.7%, Rp = 8.6%, and RF = 10.4%. Disorder has been found in the oxygen that bridges the pyrophosphate groups, leading to an angular P-O-P arrangement. The VIS-near-IR adsorption spectra revealed the uranium(IV) presence and the oxygen environment
[en] Growth in the potential applications of nanomaterials has led to a focus on the development of new manufacturing approaches for these materials. In particular, an increased demand due to the unique properties of nanomaterials requires a substantial yield of high-performance materials and a simultaneous reduction in the environmental impact of these processes. In this paper, a high-rate production of phosphine-stabilized undecagold nanoclusters was achieved using a layer-up strategy which involves the use of microlamination architectures; the patterning and bonding of thin layers of material (laminae) to create a multilayered micromixer in the range of 25-250 μm thick was used to step up the production of phosphine-stabilized undecagold nanoclusters. The continuous production of highly monodispersed phosphine-stabilized undecagold nanoclusters at a rate of about 11.8 (mg s-1) was achieved using a microreactor with a size of 1.687 cm3. This result is about 500 times over conventional batch syntheses based on the production rate per reactor volume.