Exploring the Coordination of Plutonium and Mixed Plutonyl–Uranyl Complexes of Imidodiphosphinates

The coordination chemistry of plutonium­(IV) and plutonium­(VI) with the complexing agents tetraphenyl and tetra-isopropyl imidodiphosphinate (TPIP– and TIPIP–) is reported. Treatment of sodium tetraphenylimidodiphosphinate (NaTPIP) and its related counterpart with peripheral isopropyl groups (NaTIPIP) with [NBu4]2[PuIV(NO3)6] yields the respective PuIV complexes [Pu­(TPIP)3(NO3)] and [Pu­(TIPIP)2(NO3)2] + [PuIV(TIPIP)3(NO3)]. Similarly, the reactions of NaTPIP and NaTIPIP with a Pu­(VI) nitrate solution lead to the formation of [PuO2(HTIPIP)2(H2O)]­[NO3]2, which incorporates a protonated bidentate TIPIP– ligand, and [PuO2(TPIP)­(HTPIP)­(NO3)], where the protonated HTPIP ligand is bound in a monodentate fashion. Finally, a mixed U­(VI)/Pu­(VI) compound, [(UO2/PuO2)­(TPIP)­(HTPIP)­(NO3)], is reported. All these actinyl complexes remain in the +VI oxidation state in solution over several weeks. The resultant complexes have been characterized using a combination of X-ray structural studies, NMR, optical, vibrational spectroscopies, and electrospray ionization mass spectrometry. The influence of the R-group (R = phenyl or iPr) on the nature of the complex is discussed with the help of DFT studies.