Protactinium occupies an important position in the periodic table, located at the electronicintersection between f- and d-element chemistries.  Electronic structure calculations suggestthat at Pa the energetics of the 5f and 6d orbitals are nearly degenerate.  This is unlike Th, where the 5f states are higher in energy than the 6d, and unlike U where the 5f are lower in energy than the 6d.  Inspired by the interesting chemical and electronic questions that these calculations pose we are undertaking a study of the coordination chemistry and physical properties of Pa compounds.  Because of the complex aqueous chemical behavior of Pa(V) we have initiated our studies using fluoride solutions and precipitates from these solutions.  Initial studies have focused on the coordination chemistry of Pa fluorides in the solid state and the speciation of Pa(V) in aqueous media using a series of spectroscopic and structural techniques. A series of homoleptic fluoride complexes have been synthesized and their single crystal structures determined. These complexes serve as models for our spectroscopic studies of Pa(V)in aqueous solution, providing insight into the speciation of Pa(V) in these systems.  They provide a starting point for further studies aimed at investigating the electronic structure usingPa(IV), for which there is a single 5f electron .  This work is funded by the U.S. DOE EarlyCareer Research Award program and was performed at Argonne National Laboratory forthe U.S. DOE, OBES, Division of Chemical Sciences, Geosciences, and Biosciences, under contract DE-AC02-06CH11357.

Chemistry of protactinium fluorides

247th National Meeting (2014)

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