The electronic characteristics of actinide complexes have been a rich research area for many decades because these elements behave unlike any other group on the periodic table. They generally retain the spectroscopic and magnetic properties associated with the number of f-electrons regardless of coordination environment, but can still form partially covalent bonds due to symmetry and energy matching of the 5f and 6d orbitals. This partially covalent interaction can lead to a discontinuity between low valent actinides and their lanthanide congeners either through shorter bond lengths, different structures, or differences in electronic character. This discontinuity is not always observed, and the expression of covalent effects depends greatly on the nature of the ligand. The more ionic ligands such as the aquo triflates, phosphonates, and phosphites generate very similar 4f and 5f compounds. Conversely, softer, more polarizable ligands such as borate, imidodiphosphinochalcogenides, and cyclic π-donors show differences between the lanthanides and actinides. We have recently explored the reactions of oxyanions with high hyperpolarizabilities and the actinides to probe this discontinuity as we believe that there is a direct relationship between the hyperpolarizability of a single M – O bond and the polarizability of the entire oxyanion. These oxyanions include molybdate and tungstate which have significantly high hyperpolarizabilities. This combination of a d0 metal with an actinide should result in interesting bonding as seen with other polarizable ligands.

Divergence between plutonium and americium in oxoanion materials

249th National Meeting (2015)

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