Definition of -adduct (pi-adduct)

1. An adduct formed by electron-pair donation from a pi orbital into a sigma orbital, or from a sigma orbital into a pi orbital, or from a pi orbital into a pi orbital. For example:

   

   Such an adduct has commonly been known as a "pi complex", but, as the bonding is not necessarily weak, it is better to avoid the term complex, in accordance with the recommendations in this Glossary. See also coordination.