Intramolecular frustrated lewis pairs: formation and chemical features.

Intramolecular vicinal and geminal frustrated Lewis pairs (FLPs) featuring bulky substituents at phosphorus or nitrogen and strongly electron-withdrawing bulky pentafluorophenyl substituents at boron undergo a variety of addition and/or activation reactions with small molecules. A number of examples of such reactions are presented and discussed, among them the FLP activation of dihydrogen to give zwitterionic phosphonium (or ammonium)/hydridoborate zwitterions. Intramolecular FLPs also add to organic carbonyl compounds (including carbon dioxide), to alkenes and alkynes (including conjugated dienes, diynes or enynes), to heterocumulenes, to azides, and to nitric oxide.