Tertiary phosphines are often used as ligands in coordination chemistry. The binding of phosphines bind to metals, which serve as Lewis acids. For example, silver chloride reacts with triphenylphosphine to 1;1 and 1:2 complexes:
:PPh + AgCl → ClAgPPh
:PPh + ClAgPPh → ClAg(PPh)
The adducts formed from phosphines and borane are useful reagents.  These phosphine-boranes are air-stable, but the borane protecting group can be removed by treatment with amines.