Eva-Maria Strauss

Homocyclic Selenium Molecules and Related Cations

Publisher Summary This chapter discusses the homocyclic selenium molecules and related cations. The structures and bond properties of the homocyclic species discussed in this chapter explore that the selenium-selenium bond exhibits basically the same features as the well-investigated analogous sulfur-sulfur bond, which is known for its ability to adjust to a wide variety of bonding situations by large variations of the bond distances, bond angles, and dihedral angles. One of the major differences between two-coordinated sulfur and selenium is the tendency of the latter to increase its coordination number, as can be seen from the fairly strong intermolecular interactions between selenium rings in the various crystal structures. In this context the already better understood homocyclic sulfur compounds and, in particular, the mixed species, the heterocyclic selenium sulfides, can serve as models to study the structural and chemical behavior of the selenium-selenium bond.

Photolyse von elementarem Schwefel (S6 , S7 , S8 , S10 , S12 ) in Kohlenstoffdisulfidlösung [1] / Photolysis of Elemental Sulfur (S6, S7, S8, S10, S12) in Carbondisulfide Solution [1]

Abstract The photochemical decomposition of pure carbondisulfide as well as of solutions of pure S6 , S7 , S8 , S10 and S12 , respectively, in CS2 at 15 °C on irradiation by a high-pressure mercury lamp (200-600 nm) has been studied by quantitative HPLC analysis of the soluble products. In all cases mixtures of sulfur homocycles Sn (n = 5,6, ...) are formed with S8 , S7 and S6 being the dominating species, but traces of S5 , S9 , S10 and S12 have also been observed in most cases. S5 has been identified for the first time; it is formed in particular in the photolysis of S7 in CS2 . All irradiated sulfur solutions reach more or less the same photostationary equilibrium, but the decomposition of CS2 increases linearly with time and its effects are superimposed on the Sn interconversion reactions.

Chromatographische Trennung schwefelhaltiger Heterocyclen der Typen (CH2)nSm und SenS8-m mittels HPLC [1] / Chromatographie Separation of Sulfur Containing Heterocycles of Type (CH2)nSm und SenS8-m by HPLC [1]

Abstract The Separation of a number of cyclic methylene sulfides and selenides by reversed-phase high-pressure liquid chromatography is reported. The retention times as well as the capacity factors depend in a systematic way on the ring size, the number and kind of chalcogen atoms, and the number of heteronuclear bonds within the ring. These relation-ships are used to assign the chromatograms of cyclic selenium sulfides of type SenS8-n (n = 1-8) prepared in a new reaction from Se2Cl2, SCl2 and potassium iodide and containing all selenium atoms in neighboring positions.

Fundamental vibrations of six- and seven-membered selenium sulphide ring molecules

The fundamental vibrations of eleven possible six-membered selenium sulphide ring molecules SenS6 –n, as well as of all isomers of the two seven-membered rings 1,2-Se2S5 and 1,2-Se5S2, have been calculated using an extended Urey–Bradley force field in order to support ongoing and future preparative work by providing a convenient method for characterizing the new products which can be prepared by a variety of chemical reactions. The calculated wavenumbers for SeS5 and 1,2-Se2S5 have been used to assign the Raman spectra for both compounds. In general, the results indicate that the stretching vibrations of various selenium sulphides are sufficiently different to allow identification of the species by a detailed analysis of their Raman spectra.