IF5 affects the final stage of the Cl-F exchange fluorination in the synthesis of pentafluoro-λ6-sulfanyl-pyridines, pyrimidines and benzenes with electron-withdrawing substituents.

A difficult chlorine-fluorine (Cl-F) exchange fluorination reaction in the final stage of the preparation of pentafluoro-λ6-sulfanyl-(hetero)arenes having electron-withdrawing substituents has now been elucidated through the use of iodine pentafluoride. A major side-reaction of C-S bond cleavage was sufficiently inhibited by the potential interaction between F and I with a halogen bonding.