Synthesis and crystal structure of a ten-coordinate plutonium(IV) ion complexed by 2-[(diphenylphosphino)methyl]pyridine N,P-dioxide: [Pu(NO3)3{2-[(C6H5)2P(O)CH2]C5H4NO}2][Pu(NO3)6]0.5

The bifunctional ligand 2-[(C6H5)2P(O)CH2]C5H4NO (2), in EtOH, combined in a 1 ∶ 1 ratio with Pu(IV) in an aqueous nitric acid solution, produced an orange–brown coordination complex. The complex was characterized in MeOH solution by UV/vis/near-IR spectroscopy and in the solid state by single-crystal X-ray diffraction analysis. In the solid state, the complex exists as a 2 ∶ 1 coordination complex, [Pu(2)2(NO3)3+][Pu(NO3)62−]0.5, with the two ligands (2) bonded to the Pu(IV) ion in a bidentate fashion. Six oxygen atoms from three bidentate nitrate ions also occupy inner-sphere coordination positions. The complex cation charge is balanced by a hexanitratoplutonium(IV) dianion that resides on an inversion center between two monocationic [Pu(2)2(NO3)3+] units. The ten-vertex coordination polyhedron of the cation is distorted from square antiprismatic towards a sphenocorona. Optical absorbance spectra of the Pu(IV) in MeOH containing varying concentrations of nitrate and 2, show that multiple complexes form in solution.