Strategy for the determination of mixtures of alpha and beta emitters in water samples with a combination of rapid methods

Journal of Radioanalytical and Nuclear Chemistry - Quantification of several alpha and beta emitters in mixtures of radionuclides arouses great interest in many fields such as surveillance around...     

The application of pyranoside phosphite-pyridine ligands to enantioselective Ir-catalyzed hydrogenations of highly unfunctionalized olefins

Eight (biaryl)phosphite/pyridine ligands 1–2a–d have been prepared by the modular functionalization of positions C-2 and C-3 of two d-glucopyranoside backbones. The chiral ligands were examined in the iridium-catalyzed asymmetric hydrogenation of poorly functionalized alkenes, as a function of the relative position of the coordinating groups and the geometric properties of the biaryl phosphite moieties. Enantiomeric excesses of up to 90% were achieved in the hydrogenation of E-2-(4-methoxyphenyl)-2-butene by using 1a and 1c, which seemingly combine the beneficial effect of the phosphite at the 2-position with the matching (R_ax)-configuration of their encumbered biaryl substituents. The results of the hydrogenation of more challenging substrates, such as Z-trisubstituted alkenes, alkenes with a neighboring polar group or demanding 1,1-di-substituted alkenes, generally confirmed this trend, and in some significant cases, the chiral hydrogenated products were isolated with ees of 65–79%.     

A Capped Octahedral MHC6 Compound of a Platinum Group Metal

A MHC₆ complex of a platinum group metal with a capped octahedral arrangement of donor atoms around the metal center has been characterized. This osmium compound OsH{κ²‐C,C‐(PhBIm‐C₆H₄)}₃, which reacts with HBF₄ to afford the 14 e^? species [Os{κ²‐C,C‐(PhBIm‐C₆H₄)}(Ph₂BIm)₂]BF₄ stabilized by two agostic interactions, has been obtained by reaction of OsH₆(PiPr₃)₂ with N,N′‐diphenylbenzimidazolium chloride ([Ph₂BImH]Cl) in the presence of NEt₃. Its formation takes place through the C,C,C‐pincer compound OsH₂{κ³‐C,C,C‐(C₆H₄‐BIm‐C₆H₄)}(PiPr₃)₂, the dihydrogen derivative OsCl{κ²‐C,C‐(PhBIm‐C₆H₄)}(η²‐H₂)(PiPr₃)₂, and the five‐coordinate osmium(II) species OsCl{κ²‐C,C‐(PhBIm‐C₆H₄)}(PiPr₃)₂.     

Using expert’s rules as background knowledge in the ClusDM methodology

In complex domains it is usually quite difficult to introduce context information. However, sometimes that information should be taken into account to make decisions, because it provides some relevant knowledge that cannot be expressed using an attribute-value representation. This is the case of the determination of risk of contamination of soils. In this paper, we propose to use conjunctive rules to introduce additional background knowledge to a MCDM sorting method called ClusDM. ClusDM is based on the aggregation of the data with unsupervised clustering techniques. The paper presents a new algorithm to incorporate rules to guide the clustering process in a semi-supervised way. The paper also describes how it works in the case sorting a set of possible contaminated soils, and compares the results obtained by ClusDM when rules are used or not.     

X-ray powder structure of a new two-dimensional nickel(II) coordination polymer with pyrazine-2,3,5,6-tetracarboxylic acid

The new nickel(II) coordination polymer poly­[di­aqua­nickel(II)-μ-(pyrazine-2,3,5,6-tetra­carboxyl­ato)-tetra­aqua­nickel(II)], {[{Ni(C₈N₂O₈)(H₂O)₂}Ni(H₂O)₄]}_n, has been synthesized and characterized both spectroscopically and crystallographically, by X-ray powder diffraction analysis. In this two-dimensional coordination polymer, Ni^II ions are bridged by pyrazine-2,3,5,6-tetra­carboxyl­ic acid, coordinating in a bis-bidentate manner, so forming one-dimensional polymeric chains. The chains are linked by a second Ni^II ion, via an O atom of the coordinated carboxyl­ate group, resulting in the formation of a two-dimensional layer-like polymer. The remaining coordination sites of the two independent octahedral Ni^II ions are occupied by water mol­ecules. The layers are connected via hydrogen bonds involving all six coordinated water mol­ecules.     

Spatial bi-stacked central configurations formed by two dual regular polyhedra

In this paper we prove the existence of two new families of spatial stacked central configurations, one consisting of eight equal masses on the vertices of a cube and six equal masses on the vertices of a regular octahedron, and the other one consisting of twenty masses at the vertices of a regular dodecahedron and twelve masses at the vertices of a regular icosahedron. The masses on the two different polyhedra are in general different. We note that the cube and the octahedron, the dodecahedron and the icosahedron are dual regular polyhedra. The tetrahedron is itself dual. There are also spatial stacked central configurations formed by two tetrahedra, one and its dual.     

Use of sugar-based ligands in selective catalysis: Recent developments

This review describes recent development in the use of sugar-derived ligands in the selective synthesis of organic molecules. Developments in the recent literature (2004–2009) are highlighted in the areas of hydrogenation, 1,2- and 1,4-additions of nucleophiles to CO and CNR based substrates, cross-coupling, hydroformylation, oxidation and other reactions. Connections to earlier studies are also noted were relevant. Some suggestions as to the underlying features that make sugar-based ligands highly useful modular ligands in selective catalysis are given. Finally, advice is presented (for the non-specialist) on optimal entry points and basic starting materials for sugar-ligand synthesis.