Selenium tetrachloride

Abstract: The condensation of diaminobenzenedithiol with sulfur monochloride leads to the chloride salt of the radical cation of 3,6-dichlorobenzo(1,2-d:4,5-d')bis(1,2,3-dithiazole), dichloro-(BB-123-DTA)(Cl), which can be reduced to neutral dichloro-(BB-123-DTA) with triphenylantimony. A similar condensation with selenium tetrachloride leads, upon reduction, to the corresponding bis(1,2,3-thiaselenazole) dichloro-(BB-123-TSA). The crystal and molecular structures of both compounds have been determined by X-ray diffraction. Both compounds, which are formally antiaromatic 16﷿-systems, exhibit internal bond lengths consistent with a quinoid formulation. The radical cations of both rings have been characterized by ESR spectroscopy; for dichloro-(BB-123-DTA) + g ) 2.0114 and aN ) 0.201 mT, while for dichloro-(BB-123-TSA) + g ) 2.021 and aN ) 0.44 mT. Further oxidation of both rings affords the corresponding dications, both of which have been characterized crystallographically as their AlCl 4 - salts. The structural features of these compounds are consistent with those expected for dithiazolylium (or thiaselenazolylium) derivatives. The structure and redox chemistry of the benzo(1,2-d:4,5-d')bis(1,2,3-dithiazole) framework is discussed in the light of the results of ab initio calculations.

Abstract: Selenium tetrachloride(SeCl4) reacts smoothly with alcohols in various nonpolar solvents to give the corresponding alkyl chlorides in 44–97% yield. Similar reaction also proceeds with tellurium tetrachloride (TeCl4), while the treatment of benzyl, 1-phenylethyl, and t-butyl alcohols with TeCl4 in aromatic solvents results in a high yield formation of alkylated aromatics instead of alkyl chlorides. Such Friedel-Crafts aromatic alkylation hardly occurs in the SeCl4 case. The chlorinating species is not chlorine which might be evolved by dissociation of SeCl4 or TeCl4, but the metal chloride itself. The conversion of optically active (R)-(+)-1-phenylethanol to 1-phenylethyl chloride proceeds with nearly complete racemization.