Gas phase Lewis acidity and basicity scales for boranes, phosphines and amines based on the formation of donor-acceptor complexes

► Some reactivity indices help us to clarify the electronic effects coming from the substituents. ► The molecular electrostatic potential and the Fukui function are important to predict the protonation sites. ► The proton and hydride scales, correlates with the intrinsic tendencies to donate or receive electrons. ► There are numerical problems in locating true minima on the PES of some donor-acceptor complexes.