Reductive silylation of a uranyl dibenzoylmethanate complex: an example of controlled uranyl oxo ligand cleavage

Abstract

Reaction of UO₂(dbm)₂(THF) (dbm = OC(Ph)CHC(Ph)O) with 1 equiv. of R₃SiH (R = Ph, Et), in the presence of B(C₆F₅)₃, results in the formation of U(OB{C₆F₅}₃)(OSiR₃)(dbm)₂(THF) (R = Ph, 1; Et, 2), which were isolated as red-orange crystalline solids in good yields. Interestingly, the addition of 1 equiv. of H(dbm) to 2 results in protonation of the –OSiEt₃ ligand and formation of U(OB{C₆F₅}₃)(dbm)₃ (4) in 33% yield, along with formation of HOSiEt₃. Furthermore, addition of HOSiEt₃ and 1 equiv. of THF to 4, results in the formation 2, revealing that this process is reversible. The two-step conversion of UO₂(dbm)₂(THF) to 4 represents a rare example of controlled uranyl oxo ligand cleavage at ambient temperature and pressure. Comparison of diffraction and density functional theory data for 4 suggests the presence of the inverse trans influence, with a very shallow potential energy well for distortion along the trans U–O bond.