POLYHALOMETHANES COMBINED WITH ALUMINUM HALIDES AS GENERATORS OF SUPERELECTROPHILES OF A NOVEL TYPE

Semi-empirical (AM1) and ab initio (MO LCAO SCF-RHF/6-31G) quantum che mical calculations of CCl4 . nAlCl(3)(n = 1, 2) and CCl3+AlCl3 systems were performed to elucidate the nature of complexes responsible for t he superelectrophilicity of tetrachloromethane in the presence of alum inum chloride. The results of the calculations do not allow us to rela te the high activity of these systems with formation of the species Cl 2CCl+-->AlCl3. The CCl4 . nAlCl(3) systems were shown to be generators of the superelectrophiles of a novel type, namely the electron defici ent 'chlorenium' cations Cl2C-Cl+ and dications Cl+-C-Cl+ which are di fferent from the known chloronium cations R-Cl+-R. The capability of f orming mono-, di- and tridentate ionic complexes, wherein Cl+ of the C Cl3+ cation is bonded with one, two or three Cl- of AlCl4-, is a pecul iarity of the CCl3+AlCl4- system. The bidentate complex CCl3+AlCl4- wi th positive charge 0.54a.u. on the Cl atom (instead of 0.33 a.u. in a free CCl3+) seems to be the best candidate for the role of key superel ectrophile in the CCl4 . nAlCl(3) systems. (C) 1997 Elsevier Science S .A.