PNNL

Abstract

A comprehensive understanding of when and how 5f orbitals participate in complex chemical bonding is important for a variety of applications. The actinides are unique in that they can access high oxidation states, which makes them attractive for use in catalysis. Fundamental studies of actinide-ligand interactions offer a route to examine the extent of activation of the 5f orbitals so that the selectivity of 5f orbitals can be assessed. A previous study examined the reaction of Pu+ + CO2 and determined that the reaction efficiency is restricted by a barrier, namely promotion from the Pu+ ground state configuration, 5f67s, to a reactive state configuration, 5f56d2. The present study illustrates the benefit of activation of Pu’s 5f orbitals when studying the reaction of Pu+ + NO. By this reaction, PuO+ forms in an exothermic, barrierless process and does not require Pu+ promotion to a reactive 5f56d2 configuration. As a result, the 5f orbitals can and do participate to form a linear intermediate, [N – Pu – O]+, and the reaction efficiency is not limited by promotion to a 6d2 configuration. Understanding the conditions under which 5f orbitals are active in chemical bonding is the key to exploiting the actinides’ selective catalytic capabilities.