PROTONATION STUDIES ON ISOMERIC TETRAFLUORO-2,11-DITHIA[3.3]CYCLOPHANES, TETRAFLUORO[2.2]METAPARACYCLOPHANE AND THEIR CORRESPONDING NONFLUORINATED ANALOGS - COMPARISON WITH FLUORINATED AND NONFLUORINATED [2.2]CYCLOPHANES - A STABLE ION AND SEMIEMPIRICAL (AM1, PM3) INVESTIGATION

Protonation of tetrafluoro-2,11-dithia [3.3]paracyclophane and tetrafl uoro-2,11-dithia [3.3]metaparacyclophane in high-acidity super acid me dia, namely FSO3H.SbF5 (1:1) 'magic acid'-SO2ClF, gave their correspon ding acidic disulfonium ions. Additional ring protonation to give a di sulfonium-monoarenium trication was not observed. With the non-fluorin ated 2,11-dithia [3.3]cyclophanes, the disulfonium ions can be ring pr otonated in equilibrium to give a dynamic disulfonium-monoarenium tric ation. Tetrafluoro [2.2]-metaparacyclophane is monoprotonated at the m eta ring and gives a complex mixture of conformational isomers. Multin uclear magnetic resonance data on the cyclophane precursors and their derived cations are compared and analysed. The energies, conformations and charge distributions of the isometric fluorinated and non-fluorin ated [2.2]- and dithia [3.3] cyclophanes were calculated by the AM1 an d PM3 methods, respectively. In all but one case the cyclophane areniu m ions predicted by theory to be energetically most favoured are those observed in solution under stable ion conditions. In agreement with e xperiment, the instabilities of S,S,C-cyclophane trications are also t heoretically predicted.