CRYSTAL-STRUCTURE AND VIBRATIONAL CHARACTERIZATION OF THE REACTION-PRODUCTS OF N-METHYLTHIAZOLIDINE-2(3H)-SELONE(1) AND N-METHYLBENZOTHIAZOLE-2(3H)-SELONE(2) WITH BR-2

The products obtained by reacting the title selenium donors, 1 and 2, with molecular dibromine, both in 1 : 1 and 1 : 2 1(2)/Br-2 molar rati os in CH2Cl2 solution, are described. Depending on the molar ratio of the reagents, 1 gives two different products having stoichiometries 1 . Br-2 (I) and C8H14Br8N2S2Se (II). Compound II, characterised by X-ra y diffraction on a single crystal, is an ionic compound having formula (C4H7BrNS)(2)[SeBr6]. Thus, the reaction occurs through C=Se bond bre aking and formation of the N-methyl-2-bromothiazolidinium cation and o xidation of the selenium atom to a hexabromo selenate(2-) anion. In th e corresponding reaction with 2, the same compound of stoichiometry 2 . Br-2 (III) is obtained in both molar ratios. The X-ray diffractometr ic analysis on a single crystal of III shows that it is a hypervalent Se-compound, C8H7Br2NSSe, bearing the Br-Se-Br linear group. FT-IR and FT-Raman spectra are in accordance with structural results for II and III and help to characterise I. (C) 1997 Elsevier Science Ltd.