Detlef Jensen

77Se-NMR and raman spectroscopic characterization of selenium dibromide (SeBr2) and its reaction with titanocene pentasulphide to give cyclic selenium sulphides of ring size 6, 7, 8, and 12☆

Abstract Selenium dibromide prepared from Se and SeBr 4 in acetonitrile shows a singlet at 1496 ppm in the 77 Se-NMR spectrum and Raman lines at 291, 265, and 105 cim −1 . Selenium dibromide which is in equilibrium with Se 2 Br 2 and Br 2 reacts with titanocene-pentasulphide at 20°C in CS 2 to give SeS 5 which partly dimerizes to give 1,2-Se 2 S 10 and 1,7-Se 2 S 10 . Raman spectra of Se 2 S 10 and Se 2 S 1O ·CS 2 are reported and their formation from SeS 5 is discussed. Other products of the SeBr 2 -titanocenepentasulphide reaction are 1,2-Se 2 S 5 (from Se 2 Br 2 ), S 1O (from Br 2 ), 1,2-Se 2 S 6 , 1,5-Se 2 S 6 , and 1,2,5,6-Se 4 S 4 .

Raman, mass, and 77se nmr spectra of sescl2 and its reactions with potassium iodide and titanocene pentasulphide to produce cyclic selenium sulphides☆

Abstract Mixing of S2Cl2 and Se2Cl2 at 21°C results in the formation of SeSCl2 as shown by 77Se NMR, mass, and Raman spectroscopy. The enthalpy of this reaction has been determined as + 13 kJ mol−1 (S2Cl2), and the equilibrium constant Kc = 0.066 at 294 K. In addition, the formation of other Se—S—Cl molecules and of SeCl2 is observed. An Se2Cl2-S2Cl2-SeSCl2 mixture (Se:S = 1:1) reacts with titanocene pentasulphide to give mainly S7, SeS6 and 1,2-Se2S5 but small concentrations of six-, eight-,nine- and 12-membered Se—S ring molecules have also been observed. The reaction of Se2Cl2-S2Cl2 mixtures (Se:S = 1:2) with potassium iodide affords 1,2,5-Se3S5 as the major product followed by 1,2-Se2S6, 1,4-Se2S6 and 1,3-Se2S6. HPLC analysis of this reaction shows, however, that selenium sulphide ring molecules of ring sizes 6–8 are formed. Mixing of SCl2 and Se2Cl2 at 21°C results in precipitation of SeCl4 and formation of S2Cl2, which reacts with Se2Cl2 to give SeSCl2.

Dinuclear Titanocene Chalcogenides as Sulfur and Selenium Transfer Reagents in Ring Synthesis1

Abstract The dinuclear titanocene complexes Cp4Ti2S6, Cp4Ti2S4 and Cp4Ti2Se4 have been reacted with SCl2, S2Cl2, and Se2Cl2, respectively. The reaction products are rings of type Sn (n = 6…20) and six-, seven- and eight-membered rings of type Sex Sy, respectively, which have been characterized by HPLC, Raman and Se-NMR spectroscopy, as well as X-ray diffraction on single crystals.

Spectroscopic Evidence for Pseudorotation of Seven-Membered Chalcogen Rings in Solution [1]

The 77Se NMR spectrum of 1,2-Se2S5 exhibits one singlet at 1077.3 ppm indicating pseudorotation in solution; the same conclusion is reached from the solution Raman spectrum of S7 showing characteristic line broadening compared to the solid state spectrum