ACID GENERATION IN THE THERMAL-DECOMPOSITION OF DIARYLIODONIUM SALTS

Diphenyliodonium tetrafluoroborate and diphenyliodonium hexafluorophos phate have been found to generate tip to two equivalents of hydrogen f luoride per equivalent of the iodonium salt by pyrolysis at 239 degree s C in the neat state and at 150 degrees C in the presence of-anisole or nitrobenzene. The formation of hydrogen fluoride is presumed to ari se by dissociation of hydrogen tetrafluoroborate or hydrogen hexafluor ophosphate initially formed due to the high temperatures, thus giving rise also to the Lewis acids boron trifluoride and phosphorus pentaflu oride, respectively. A detailed analysis of the volatile organic produ cts of the decomposition of the diphenyliodonium salts was also carrie d out. Many products were identified in all of the cases studied. For example, the Meat decomposition of diphenyliodonium tetrafluoroborate afforded benzene, fluorobenzene, iodobenzene, the three isomeric iodob iphenyls, biphenyl, three isomeric terphenyls, and one or move of the diiodobiphenyls, iodoterphenyls, and polyaromatics. Among the iodobiph enyls, the ortho and para isomers were found to predominate over the m eta isomer. The terphenyl isomers did not exhibit this ortho, para sel ectivity. If was significant that decomposition of the diaryliodonium salts in anisole suspension did not afford methoxybiphenyls or iodomet hoxybiphenyls. An interpretation of these results is presented. (C) 19 96 John Wiley & Sons, Inc.