Seventeen-Coordinate Actinide Helium Complexes.

The geometries and electronic structures of molecular ions featuring He atoms complexed to actinide cations are explored computationally using density functional and coupled cluster theories. A new record coordination number is established, as AcHe17(3+) , ThHe17(4+) , and PaHe17(4+) are all found to be true geometric minima, with the He atoms clearly located in the first shell around the actinide. Analysis of AcHen(3+) (n=1-17) using the quantum theory of atoms in molecules (QTAIM) confirms these systems as having closed shell, charge-induced dipole bonding. Excellent correlations (R(2) >0.95) are found between QTAIM metrics (bond critical point electron densities and delocalization indices) and the average Ac-He distances, and also with the incremental He binding energies.