Synthesis and characterization of uranium(III) compounds supported by the hydrotris(3,5-dimethyl-pyrazolyl)borate ligand: Crystal structures of [U(TpMe2)2(X)] complexes (X = OC6H2-2,4,6-Me3, dmpz, Cl)

Reaction of [U(TpMe2)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(TpMe2)2(OAr)] (Ar = C6H2-2,4,6-Me3) (1), [U(TpMe2)2(dmpz)] (2), [U(TpMe2)2(η2-SC5H4N)] (3), and [U(TpMe2)2(CCPh)] (4) compounds. Reaction of [U(TpMe2)2(NR2)] with Me3SnCl or Me3SiBr gave [U(TpMe2)2Cl] (5) and [U(TpMe2)2Br] (6), respectively, in high yield. The amido precursors failed to react with cyclopentadiene, but metathesis of [U(TpMe2)2I] with NaCp yielded [U(κ3-TpMe2)(κ2-TpMe2)(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(TpMe2)(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.

Graphical abstractA series of [U(TpMe2)2(X)] complexes has been prepared by reaction of [U(TpMe2)2(NR2)] with protic substrates and halide sources and/or metathesis of [U(TpMe2)2I]. The compounds are structurally similar to the analogous samarium complexes, but the availability of higher oxidation states for uranium leads to a different outcome for the thermolysis of [U(TpMe2)2Cp].Figure optionsDownload full-size imageDownload as PowerPoint slide