A stereoselective synthesis of symmetrical (E,E)-1,3-dienes by silver(I) promoted homo coupling of (E)-alkenylpentafluorosilicates

symmetrical (E,E)-1,3-dienes can be prepared by high yields from (E)-alkenylpentafluorosilicates either by treating with silver fluoride in acetonitrile or by stirring with silver nitrate in water/ether.     

Recoil-ion momentum distribution for He(e,2e)He+-and He(e,3e)He++-reactions

Using Recoil-Ion Momentum Spectroscopy (RIMS) we have measured the momenta of recoiling target ions in He(e,2e)He⁺- and He(e,3e)He⁺⁺-reactions at impact energies between 270 ev and 3200 eV. The recoil-ion momentum reflecting the sum momentum of all outgoing electrons was determined for the first time in all three spatial dimensions separately for single and double ionization by electron impact. The data are compared to results of a nCTMC-calculation.     

A pseudo-Jahn-Teller distortion in an Mo(2)(mu(2)-O)(2) ring having the shortest Mo(IV)-Mo(IV) double bond

Four structures of edge-sharing bioctahedral compounds of the type Mo(2)(mu(2)-DArF)(2)(eta(2)-L-L)(2)(mu(2)-O)(2), where DArF is an anion of an N,N'-diarylformamidine and L-L is a chelating acetate or DArF group, are reported here. The cores of the ring formed by the Mo(2)(mu(2)-O)(2) are very similar with very short Mo-Mo distances of 2.306[2] A. These are consistent with the presence of a Mo=Mo double bond of the type sigma(2)pi(2). As expected for these electronic configurations, the compounds are diamagnetic. The most striking characteristic is the distortion of the Mo(2)(mu(2)-O)(2) ring where a set of two Mo-O distances are significantly shorter then the other set (by ca. 0.05 A). This D(2)(h)--> C(2)(h) distortion is explained on the basis of a pseudo-Jahn-Teller effect.     

The chemical nature of the (plus sign in circle)C-H...X- (X=Cl or Br) interaction in imidazolium halide ionic liquids

The C-H...X (X=Cl or Br) interaction is traditionally characterized as a relatively weak interaction. However, this interaction becomes very strong in the imidazolium-based halide ionic liquids [J. Phys. Chem. 123, 174501 (2005)]. This strong interaction had been attributed to the electrostatic interaction between the imidazolium cation and the halide anion. In this paper, the chemical nature of the (plus sign in circle)C-H...Cl(-) and ( plus sign in circle)C-H...Br(-) interactions is investigated by atoms in molecules (AIM) and natural bond orbital (NBO) analyses. The AIM calculations indicate that in the EmimX complexes, the (plus sign in circle)C-H...Cl(-) and (plus sign in circle)C-H...Br(-) interactions have some covalent character, especially the (plus sign in circle)C-H...Cl(-) interaction. Mulliken, ChelpG charge, and natural bond orbital population analyses for these two kinds of interactions indicate that the charge transfer is important in the interaction of the cation with the anion. In addition, the NBO analysis demonstrated that the stabilization energy is due to an n-->sigma(C-H) (*) orbital interaction. However, in the Emim2X and Emim3X complexes, the calculated results suggested a dominant electrostatic character for the (plus sign in circle)C-H...Cl(-) and (plus sign in circle)C-H...Br(-) interactions.     

Binding energy and geometry of e+ A (A=Li,Na) by the hyperspherical approach

We calculate the binding energy and geometry of the weakly bound e(+)Li and e(+)Na systems within the framework of hyperspherical coordinates. The Schrodinger equation in hyperangular coordinates is solved at a series of fixed hyper-radii using B-splines and the resulting coupled hyper-radial equation is solved using the slow variable discretization method developed by Tolstikhin et al. [J. Phys. B 29, L389 (1996)]. Great efforts are made in optimizing the distribution of B-splines to overcome the slow convergence of the binding energy and geometrical quantities. This approach allows us to obtain the results with improved convergence that are in good agreement with the best values reported to date. In addition, an analysis of the structure of the two systems is also made and the e(+)Na system is seen to exhibit quantum halo features.     

Assignment and sign determination of (C,H) and (H,H) coupling constants in N-acetylimidazole with selective population inversion experiments

The assignment of the (C, H) couplings in N-acetylimidazole and the determination of the relative signs of all (C, H) and (H, H) couplings with SPI experiments are described. All coupling constants are of the same, positive, sign as the directly-bonded (C, H) coupling constants. Some advantageous features of the SPI technique, such as selectivity and increased sensitivity, are discussed in comparison to conventional double irradiation methods.     

Laser-assisted (e, 2e) collisions in helium

The influence of a strong laser field on the dynamics of fast (e, 2e) collisions in helium is analyzed in the asymmetric, coplanar geometry. The interaction of the laser field with the incident, scattered and ejected electrons is treated in a non-perturbative way, while the remaining interactions are treated by using first order perturbation theory. Detailed calculations are performed for an incident electron energyE _{k i}=600 eV, an ejected electron energyE _{k B}=5 eV and a scattering angle θ _A =4°. The influence of the laser parameters (photon energy, intensity and direction of polarization) on the angular distribution of the ejected electron is analyzed. We find that in general the triple differential cross sections are strongly dependent on the dressing of the projectile and the target by the laser field.     

A Convenient Method for the Preparation of 4(e)-Hydroxy-and 4(e)-Methoxyadamantan-2-ones

Hydrolysis or methanolysis of 4(a)-(trifluoromethyl-sulfonyloxy)adamantan-2-one affords 4(e)-hydroxy-or 4(e)-methoxyadamantan-2-one, respectively, as major product, both of which are easily separated from minor by-products.     

Simultaneous measurement of J(HH) and two different nJ(CH) coupling constants from a single multiply edited 2D cross‐peak

Three different J‐editing methods (IPAP, E.COSY and J‐resolved) are implemented in a single NMR experiment to provide spin‐state‐edited 2D cross‐peaks from which a simultaneous measurement of different homonuclear and heteronuclear coupling constants can be performed. A new J‐selHSQMBC‐IPAP experiment is proposed for the independent measurement of two different ⁿJ(CH) coupling constants along the F2 and F1 dimensions of the same 2D cross‐peak. In addition, the E.COSY pattern provides additional information about the magnitude and relative sign between J(HH) and ⁿJ(CH) coupling constants. Copyright © 2013 John Wiley & Sons, Ltd.     

The yields of1 P and1 D resonances in the He(e, 2e)He+ reaction

In the first Born approximation the dependence of the yields of the¹ P and¹ D resonances in the He(e, 2e)He⁺ reaction on the momentum transfer in the recoil peak region at incident energiesE ₀=1000 eV is studied. It is shown that in a certain range of the ejection angle and for the large momentum transfer the yield of the¹ D resonance dominates over the¹ P resonance one.     

Room temperature antiferromagnetic order in the Mn(II) Oxide 4H-Ba(0.5)Sr(0.5)MnO(2+delta)

The synthesis of the Mn(II) phase 4H-Ba(0.5)Sr(0.5)MnO(2+delta) via the topotactic reduction of 4H-Ba(0.5)Sr(0.5)MnO(3-x) with the novel reducing agent LiH, is described. Neutron powder diffraction data show that oxide ions are deintercalated from the host structure in a disordered manner to yield "tetrahedral" MnO(4) coordination sites. Magnetic susceptibility and neutron powder diffraction data show that the title phase adopts a canted antiferromagnetically ordered state below T(N) = 355K, consistent with the strong magnetic coupling expected between d(5) centers.     

A Stereoselective Synthesis of (E)-Divinyl Diselenides and (E)-Divinyl Ditellurides

Insertion of elemental selenium or tellurium into the Csp²-Zr bond of alkenylchlorozirconocenes followed by oxidation in air affords (E)-divinyl diselenides or (E)-divinyl ditellurides.     

Higher order speciation effects on plutonium L(3) X-ray absorption near edge spectra

Pu L(3) X-ray near edge absorption spectra for Pu(0-VII) are reported for more than 60 chalcogenides, chlorides, hydrates, hydroxides, nitrates, carbonates, oxy-hydroxides, and other compounds both as solids and in solution, and substituted in zirconolite, perovskite, and borosilicate glass. This large database extends the known correlations between the energy and shape of these spectra from the usual association of the XANES with valence and site symmetry to higher order chemical effects. Because of the large number of compounds of these different types, a number of novel and unexpected behaviors are observed, such as effects resulting from the medium and disorder that can be as large as those from valence.     

(e, 2e) Investigations of the Simultaneous Ionization and Excitation of Helium to He+(n=2) (cited: 1)

Three-Coulomb-wave method is employed to treat the process of (e, 2e) simultaneous ion-ization and excitation to the n=2 state of helium, with radial and angular correlated wave-function of He target. The triple differential cross sections are calculated and analyzed in very asymmetric coplanar geometry at incident energies of 5.50, 1.50 and 0.57 keV. Results are compared with the absolute measurements and the theoretical first and second Born approximation. The present triply differential cross section (TDCS) is found to be in good agreement with experimental data qualitatively. The distinguishing feature noted in TDCS structure is the presence of intense recoil peak that for certain parameters is even larger than the binary peak, an unusual feature for the single-ionization process at high and intermediate energies.