NATURE OF THE SPECIES RESPONSIBLE FOR THE HIGH-ACTIVITY OF RCOX.2ALX3 COMPLEXES IN REACTIONS WITH ALKANES AND CYCLOALKANES

The reasons for the high reactivity of aprotic organic superacids (AOS) containing an acyl halide and a double molar excess of Lewis acid in reactions with saturated hydrocarbons are studied. The synthesis and spectral properties of two pairs of acyl salts are studied: MstCO+AlBr4- and MstCO+Al2Br7- (Mst = 2,4,6-Me3C6H2) and Ac+SbF6- and Ac+Sb2F11-. Comparison of the reactivities of these salts in cracking of alkanes and isomerization of trimethylenenorbornane demonstrated that the AOS activity is due to generation of acyl salts with a dimeric anion in the slightly polar solutions. Analysis of the C-13 NMR spectra suggests that the superacid properties of these salts are due to formation of species containing acyl cations coordinated to the Lewis acid.