Synthesis and characterization of uranium(III) compounds supported by the hydrotris(3,5-dimethyl-pyrazolyl)borate ligand: Crystal structures of [U(Tp)2(X)] complexes (X = OC6H2-2,4,6-Me3, dmpz, Cl)

Reaction of U(Tp^Me2)₂(NR₂)] (R = Ph, SiMe₃) with protic substrates such as 2,4,6-trimethylphenol (HOC₆H₂-2,4,6-Me₃), 3,5-dimethylpyrazole (Hdmpz), 2-mercaptopyridine (HSC₅H₄N) and phenylacetylene (HCCPh) afforded the corresponding U(Tp^Me2)₂(OAr)] (Ar = C₆H₂-2,4,6-Me₃) (1), U(Tp^Me2)₂(dmpz)] (2), U(Tp^Me2)₂(η²-SC₅H₄N)] (3), and U(Tp^Me2)₂(CCPh)] (4) compounds. Reaction of U(Tp^Me2)₂(NR₂)] with Me₃SnCl or Me₃SiBr gave U(Tp^Me2)₂Cl] (5) and U(Tp^Me2)₂Br] (6), respectively, in high yield. The amido precursors failed to react with cyclopentadiene, but metathesis of U(Tp^Me2)₂I] with NaCp yielded U(κ³-Tp^Me2)(κ²-Tp^Me2)(η⁵-Cp)] (7). Thermolysis of 7 resulted in oxidation of the metal centre and redistribution of the ligands, giving UCp₃(dmpz)] (8), pyrazabole (9) and U(Tp^Me2)(dmpz)₃] (10). The complexes have been fully characterized by spectroscopic methods and the structures of 1, 2, and 5 were confirmed by X-ray crystallographic studies. In the solid state the complexes exhibit distorted pentagonal bipyramidal geometries.