Preference for Nitrogen versus Oxygen Donor Coordination in Uranyl- and Neptunyl(VI) Complexes

The first actinyl phosphinimine complexes have been synthesized and, in the case of uranium, exhibit strong U−N interactions. Competition reactions clearly demonstrate a surprising preference for R₃PNH ligands over R₃PO in the system [AnO₂Cl₂(R₃PX)₂] (An = U^VI, Np^VI; R = Ph, Cy; X = O, NH). Spectroscopic evidence for N-donor coordination to [NpO₂]²⁺ in solution indicates chemical similarities to the [UO₂]²⁺ moiety.