ELECTRONIC-STRUCTURE, GEOMETRY, AND STABILITY OF ORGANIC CATIONS, DICATIONS, AND DONOR-ACCEPTOR COMPLEXES .2. POLYHALOMETHANE COMPLEXES WITH ALUMINUM HALIDES

Geometric, electronic, and energy characteristics of the complexes for med in the CF4 . nAIF(3) (n = 1 or 2) and CBr4 . nAIBr(3) (n = 1, 2, o r 4) systems have been determined by the semiempirical AM1 method, Bes ides the donor-acceptor complexes, the CBr3+...AIBr(4)(-), CBr3+...Al2 Br7-, CBr22+...(AIBr(4)(-))(2), and CBr22+...(Al2Br7-)(2) ionic comple xes can be formed in the CBr4 . nAIBr(3) systems. In the cations and d ications of polyhalomethanes (when Hal = Cl, Br, or I) in both the fre e and bound (included in ionic complexes) states, carbon atoms carry n egative charges, the C-Hal bonds are substantially shortened, and the positive charges are located on one-coordinate halogen atoms. These ca tions and dications can be considered as halenium ions that differ fro m halonium salts with dicoordinate halogen atoms. In the cationic and dicationic complexes of the CBr4 . nAIBr(3) systems, the maximum posit ive charges on the Br atoms are 0.39 and 0.94, respectively. Fluorine- containing cations and dications have structures similar to those of c arbenium ions, whereas in the CF4 . nAIF(3) systems. (n = 1 or 2), onl y donor-acceptor complexes are formed.