Reversible O-H bond activation by an intramolecular frustrated Lewis pair

Abstract

The interactions of the O-H bonds in alcohols, water and phenol with dimethylxanthene-derived frustrated Lewis pairs (FLPs) have been probed. Within the constraints of this backbone framework, the preference for adduct formation or O-H bond cleavage to give the corresponding zwitterion is largely determined by pK a considerations. In the case of the PPh 2 /B(C 6 F 5 ) 2 system and p- t BuC 6 H 4 OH, an equilibrium is established between the two isomeric forms which allows the thermodynamic parameters associated with zwitterion formation via O-H bond cleavage to be probed.