Abstract: The invention relates to novel chelating ligands which incorporate a tripodal backbone. More particularly, the invention pertains to novel tripodal ligands which form coordination compounds with a variety of metal ions, particularly, but not exclusively, trivalent metal ions and lanthanide metal ions, which are useful in nuclear medicine. A novel amine phosphinate tripodal ligand, a chelating ligand and a process therefor involving a metal ion and particularly a trivalent metal ion of the group 13 metals and the rare earths. The process comprises complexing Tc or Re or any one of the group 13 metals, Al, Ga and In, and any one of the rare earths, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Th, Dy, Ho, En, Tm, Yb and Lu, with an amine phosphinate tripodal ligand.