Transformation between Diphosphinoamines and Iminobiphosphines:  a Reversible PNP ↔ NP−P Rearrangement Triggered by Protonation/Deprotonation

The protonation of diphosphinoamines attached to pyridine at the ortho-position quantitatively affords the corresponding iminobiphosphine isomers. The starting material can be recovered quantitatively by deprotonation with base. The system represents a new type of molecular switch.