The existence of cation-cation interactions (CCIs) in actinide chemistry, which involve the association of either two actinyl cations or an actinyl cation with a transition metal cation, have been known for over 50 years. The most typical example involves An(V) cations, particularly Np(V), in a T-shaped configuration where the oxo oxygen on one actinyl (Lewis base) interacts with the central An of the other (Lewis acid). In the solid state, side-on CCI structures have also been observed. Unfortunately the nature of these interactions are still not completely understood so it is difficult to predict a priori how strong a given CCI complex might be. In order to obtain a fundamental understanding of actinyl CCIs, DKH3 relativistic coupled cluster CCSD(T) calculations have been carried out in the present work with large correlation consistent basis sets to determine the structures and binding energies of several actinyl CCI complexes in the gas phase. All CCIs calculated are characterized by strong coulombic repulsions upon approach but in many cases a kinetically stable CCI results which exhibits a finite barrier where the oxo oxygen begins to donate charge to the other actinyl as shown below for UO22+(NpO2+). Results for several CCIs (including both T-shaped and side-on approaches) involving U(VI), U(V), Np(V), Pu(V), etc., will be presented.

Actinyl cation-cation interactions in the gas phase: (AnO2n+)(AnO2m+), An=U–Am

252nd National Meeting (2016)

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