Metal-metal bonding in the actinide elements: Conceptual synthesis of a pure two-electron U-U f delta single bond in a constrained geometry of U-2(OH)(10)

摘要

By utilizing high symmetry and geometric constraints, it is proposed that a molecule with a pure U-U 5f delta bond can be constructed. The proposed molecule is D-4h U-2(OH)(10) with the following geometric constraints: (1) All of the U-O-H linkages are linear, assuring that each linear hydroxide group has two filled p orbitals capable of donating to the U atoms, and (2) all of the U-U-O(eq) bond angles are 90 degrees, which assures that all of the U valence orbitals except for the f delta[zxy] orbital are destabilized by ligand donation. Preliminary DFT calculations with relativistic effective core potentials indicate that the f sigma orbital is not destabilized enough in this simple model, and that it is essentially degenerate with the fd orbital, likely leading to a triplet (f sigma)(1)(f delta)(1) single bond. Single point calculations were used to estimate the U-U bond length and bond strength of the U-U single bond in constrained U-2(OH)(10) with an (f sigma)(2)(f delta)(0) configuration. We estimate that the bond length is 3.55 angstrom and the bond strength is 9.7 kcal/mol for this very fragile molecule. (C) 2014 Elsevier B.V. All rights reserved.