1. This phenomenon has been termed nonorbital hybridization and explains why p-bonds with phosphorus are weak but three-membered heterocycles are less strained than corresponding carbon- or nitrogen-containing compounds. [W. W. Schoeller in Multiple Bonds and Low Coordination in Phosphorus Chemistry M. Regitz and O. J. Scherer Eds. (Thieme Stuttgart 1990) pp. 5-32].
2. Kato T., Gornitzka H., Bacereido A., Schoeller W. W., Bertrand G., Science289, 754 (2000).
3. Buron C., Gornitzka H., Romanenko V., Bertrand G., Science288, 834 (2000).
4. Niecke E., Fuchs A., Baumeister F., Nieger M., Schoeller W. W., Angew. Chem. Int. Ed.34, 951 (2000).
5. Heteroatom stabilized carbenium ions