Complexation of lanthanide(III) ions with a β‐diphosphorylated ligand: Nonamethylimidodiphosphoramide (NIPA). A ¹H and ³¹P NMR study

Trivalent lanthanide ions form complexes of different stoichiometries with the bidentate ligand nonamethyl‐imidodiphosphoramide (NIPA). Depending on the method of preparation, compounds with two or three NIPA molecules may be obtained, which can be distinguished and characterized on the basis of their NMR spectra. The method of preparation for the tris‐chelates and an analysis of the isotropic paramagnetic shifts for these compounds are reported; the results allow the conclusion that the complexes in solution are isostructural along the lanthanide series. The same conclusion is drawn for the bis‐chelates. In both cases the contact and pseudo‐contact contributions to 31 P shifts are important, whereas for the 1 H nuclei the dipolar contribution is largely predominant.