Addition of Bromotrichloromethane and Tetrachloromethane to cis-Cyclooctene,Cyclohexene, and Norbornadiene in the Presence of Palladium(II) Complexes

Addition of bromotrichloromethane and tetrachloromethane to alkenes in the presence of palladium(II) complexes begins with single-electron transfer from the palladium atom to polyhalomethane molecule, followed by fragmentation of the radical anion thus formed and generation of trichloromethyl radical. Halogen transfer to a carbon-centered radical arising from addition of trichloromethyl radical at the double bond occurs both from the polyhalomethane molecule and from halide palladium complex.     

Role of population analysis in LCAO-MO theory of transition-metal clusters

One-electron energy levels of NiF ₆ ^4– cluster, effective charges q_Ni and q_F, parameters 10Dq, _crys ,,f _s ,f andf were calculated using four alternative models of population analysis. The influence of the size of basis set was also investigated. Based on comparison of results it was shown that all evaluated quantities are dependent on the manner of division of overlap charge made up by virtual 4s and 4p nickel orbitals. To remove this discrepancy it was suggested to assign the whole 4s and 4p population to ligands. In this case all calculated parameters are nearly independent of a model of population analysis and the size of basis set and their values correspond better to experimental data.     

New synthesis of aryl β-bromoalkyl sulfones from arenesulfonyl chlorides via cross halogenation

A new procedure has been proposed for the synthesis of aryl β-bromoalkyl sulfones by radical addition of arenesulfonyl chlorides at the double bond of alkenes in the presence of copper(I) halides, sodium bromide, and phase-transfer catalyst. The key stage of the process is bromide ion insertion into intermediate copper(II) derivative formed in the initiation stage. The subsequent bromine atom transfer from copper to alkyl radical yields the addition product.     

Polyelectrolytes in the presence of multivalent ions: gelation versus segregation

We analyze solutions of strongly charged chains bridged by linkers such as multivalent ions. The gelation induced by the strong short range electrostatic attractions is dramatically suppressed by the long range electrostatic correlations due to the charge along the non-cross-linked monomers and ions. A modified Debye-Hückel approach of cross-linked clusters of charged chains is used to determine the mean field gelation transition self-consistently. Highly dilute polyelectrolyte solutions tend to segregate macroscopically. Semidilute solutions can form gels if the Bjerrum length l(B) and the distance between neighboring charged monomers along the chain b are both greater than the ion size a.     

Reaction of dicymanthrenylphenylbismuth with cupric chloride

Conclusions A synthesis is reported for dicymanthrenylphenylbismuth which is the first representative of cymanthrenyl derivatives of trivalent bismuth. The reaction of this compound with CuCl₂ leads to the loss of the phenyl and cymanthrenyl ligands from the central bismuth atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, p. 187, January, 1987.     

Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

Statistical thermodynamics of the formation of an infinite cluster of thermally reversible chemical bonds

A systematic “mean-field” treatment of the thermodynamic equilibrium formation of an infinite cluster of bonds in a system of identical monomers capable of forming from n=0 to n>2 reversible chemical bonds with one another is proposed within the Cayley-tree approximation. For this purpose the difference between the symmetry of the monomers appearing in “point-to-point” and closed bond paths, respectively, is taken into account on the basis of an analysis of the structure of the infinite cluster. Minimization with respect to the distribution of such monomers yields a nontrivial solution corresponding to a lower free energy than the classical solution, which does not allow for the symmetry difference indicated. In addition, it is shown that the classical solution corresponds to the free-energy maximum when the infinite cluster is formed and that the formation of the infinite cluster is a first-order phase transition. The possible form of the phase diagrams of the systems considered is analyzed. Zh. éksp. Teor. Fiz. 115, 979–990 (March 1999)     

Phenylation of sulfur dioxide by pentaphenylbismuth

Conclusions Pentaphenylbismuth phenylates sulfur dioxide to give diphenylsulfone under mild conditions in high yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2598–2599, November, 1987.     

Gelation in strongly charged polyelectrolytes

Crosslinking of strongly charged chains via multivalent ions of valence z was treated within the Flory approach, which accounts only for the treelike architecture of the clusters formed. Density–density correlations due to the electrostatic nature of the system were considered with a modified random‐phase approximation. At a certain concentration of multivalent ions that play the role of effective stickers among z monomers, an infinitely large polymer network was formed. We analyzed the gelation driven by the formation of locally neutral clusters induced by divalent and trivalent ions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 766–776, 2004