19F NMR SPECTRA OF SOME PENTAFLUOROPHENYL COMPOUNDS OF GROUP 4 ELEMENTS

Accurate chemical shifts have been determined for the pentafluorophenyl fluorine nuclei of a number of group IV pentafluorophenyl compounds by the use of an extended lock in the HA mode. All the compounds studied have a very large ortho shift, the trends of which can be predicted by both the Van der Waals electric field theory [1] and the through bond theory of Hruska et al. [2]. The meta- and para-19F chemical shifts have been used to predict the π-electron accepting ability of the various substituents attached to the group IV atom. The coupling constants obtained from those compounds which give resolvable spectra supports the chemical shift work. © 1968.