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

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.