Fission-fragment angular distributions for 230Th(n,f) in the vicinity of the 715 keV resonance

Fission-fragment angular distributions have been measured for the neutron-induced fission of ²³⁰Th in the vicinity of the 715 keV resonance with a 2.5 keV (FWHM) neutron energy resolution. An analysis was performed to find a set of fission barrier characteristics that reproduce simultaneously the present angular distribution data and the fission cross-section data of Blons et al. The analysis results show that the data for the 715 keV resonance could be fitted only if allowance is made for the existence of two rotational bands with opposite parities but with the same K quantum number. The moment of inertia parameter $\text{kh}{}^2\text{2}\text{I}$ extracted from the analysis has a value of 1.9 keV, which is compatible with the existence of a third minimum in the fission barrier at a quadrupole deformation of ε₂ = 0.85.     

Ruthenium- and palladium-catalyzed synthesis of polyfunctional 1,3-dienes

The ruthenium-catalyzed Markovnikov addition of acetic or benzoic acid to the triple bond of (E)-3-methylpent-2-en-4-yn-1-ol followed by acylation of the alcohol group in the diene formed under the action of low-toxic derivatives of carbonic and formic acids opens up a simple route to dienylic carbonates and formates. Activation of these esters by catalytic amounts of palladium(0) complexes under conditions of nucleophilic allylic substitution or decarboxylation affords functional dienes. Laboratoire de Chimie de Coordination et Catalyse, UMR 6509: CNRS—Unversité de Rennes, Campus de Beaulieu, 35042 Rennes, France. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 943–946, May, 1998.     

Alkene metathesis catalysis in ionic liquids with ruthenium allenylidene salts

Ring closing metathesis of dienes in 1-butyl-3-methylimidazolium salts in the presence of ruthenium allenylidene salts as catalyst is described.     

Ruthenium-catalyzed synthesis of alkylidenecyclobutenes via head-to-head dimerization of propargylic alcohols and cyclobutadiene-ruthenium intermediates

The reaction of propargylic alcohols with carboxylic acid, or phenol derivatives, in the presence of the precatalyst [RuCl(cod)(C5Me5)] leads selectively to a variety of alkylidenecyclobutenes through head-to-head dimerization of propargylic alcohol. The first step is the formation of a cyclobutadiene-ruthenium intermediate resulting from the head-to-head coupling of two molecules of propargylic alcohol. On protonation with strong acids (HPF6, HBF4) dehydration of the cyclobutadiene complex leads to formation of an alkylidenecyclobutenyl-ruthenium complex. The X-ray structure of one such complex, [RuCl(C5Me5)(eta4-R'CCH--CH--C=CR2)] (R'=cyclohexen-1-yl, CR2 = cyclohexylidene) has been determined. Carboxylate is added at the less substituted carbon of the cyclic allylic ligand. DFT/B3 LYP calculations confirm that the intermediate arising from head-to-head coupling of alkyne to the RuClCp* species yields the cyclobutadiene-ruthenium complex more easily with propargylic alcohol than with acetylene.     

Activation and functionalization of benzylic derivatives by palladium catalysts

Palladium-catalyzed transformations of aryl halides and pseudo-halides involving carbonylation, carbon-carbon and carbon-heteroatom bond-forming reactions, etc. are very well documented, and have already been reviewed several times. The metal-catalyzed activation of benzylic derivatives is much less described. However, during the last decades, a number of papers have shown the interest offered by benzylic derivatives (halides, carbonates, acetates, phosphonates) in selective catalytic reactions for organic synthesis, most of them in the presence of palladium catalysts. The purpose of this tutorial review is to highlight selected examples of palladium-catalyzed transformations involving reactive benzylic derivatives.     

Ruthenium‐Containing Phosphinesulfonate Chelate for the Hydrogenation of Aryl Ketones

Various ruthenium(II) complexes that contain phosphinesulfonate chelate have been synthesized. Arene‐free complexes were found to be efficient in the base‐free hydrogenation of various aryl ketones, whereas the arene‐containing precatalysts required the presence of an amine as an additive. The seminal asymmetric hydrogenation reaction by using the new Sulfo‐Binepine ligand was also investigated for the possible intervention of a dihydride species.     

Homogeneous Schr?dinger Operators on Half-Line

The differential expression L_m=-?_x²+(m²-1/4)x^-2{L_m=-\partial_x^2+(m^2-1/4)x^{-2}} defines a self-adjoint operator H _m on L ²(0, ∞) in a natural way when m ² ≥ 1. We study the dependence of H _m on the parameter m show that it has a unique holomorphic extension to the half-plane Re m > −1, and analyze spectral and scattering properties of this family of operators.