POP-type ligands: Variable coordination and hemilabile behaviour

Hemilabile ligands – ligands containing two or more potential donors to a metal centre, of which one or more can dissociate – have the ability to provide a transition metal complex with open coordination sites at which reactivity can occur, or stabilise low coordinate intermediates along reaction pathways. POP-type ligands and in particular POP, Xantphos, DBFphos and DPEphos-based ligands contain three possible binding sites: two phosphines and an ether linker, thus have the potential to show κ1-, κ2- or κ3-binding modes. This review summarises the examples where POP-type ligands display hemilabile, or closely related variable coordination, characteristics in either synthesis or catalysis.