Calculated structures of thiopyrylium-S-fluoride and S-trifluoride and attempts of their preparation

Structures and energies of cyclo-C5H5SF and cyclo-C5H5SF3 have been calculated. In both cases the 2- and 4-CF-isomers are more stable than the SF and SF3 isomers. The fluxional behavior of the sulfur bonded fluorides has been calculated also. In cyclo-C5H5SF an ellipsoidal rotation of the sulfur bonded fluorine atom is observed with a barrier of a few kcal mol−1. In sulfur bonded cyclo-C5H5SF3 the (Turnstile) rotation is predicted to occur without noticeable barrier, in agreement with previous work. ts to isolate the sulfur bonded isomers failed entirely: always 2 or 4-carbon-fluorides were obtained for cyclo-C5H5SF. The acyclic SF5− carrying precursors for the synthesis of cyclo-C5H5SF3 failed in crucial steps of the reactions.