Uranium(III, IV) and thorium(IV) pyrazolylmethane complexes: Synthesis and structures

Reactions of UI3(THF)4, UCl4 and ThCl4 with 1 equiv. of tris(3,5-dimethylpyrazolyl)methane (Tpm∗) in THF led to the formation of the complexes [U(Tpm∗)I3(THF)] (1), [U(Tpm∗)Cl4] (2) and [Th(Tpm∗)Cl4] (3) in good yields. The NMR spectra indicated symmetrical structures in solution, with equivalent pyrazolyl groups of the Tpm∗ ligand. The X-ray crystal structures of the three complexes were determined and in all cases the metallic centre is seven-coordinated, presenting distorted capped octahedral coordination geometry with near C3v symmetry. In 1, the tridentate pyrazolylmethane ligand and the three iodine atoms define the two staggered triangular faces of the octahedron, respectively, and the latter is capped by the THF oxygen. In 2 and 3, the coordination geometry is similar, with three chlorine atoms defining a triangular face capped by the fourth chlorine.

Graphical abstractReactions of UI3(THF)4, UCl4 and ThCl4 with tris(3,5-dimethylpyrazolyl)methane led to the formation of the first actinide pyrazolylmethane complexes [U(Tpm∗)I3(THF)], [U(Tpm∗)Cl4] and [Th(Tpm∗)Cl4], which were characterized by NMR and X-ray crystallography.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► First synthesis and characterization of actinide pyrazolylmethane (Tpm∗) complexes. ► Tpm∗ complexes of U(III), U(IV) and Th(IV) fully characterized by NMR spectroscopy and X-ray crystallography. ► Complexes display distorted capped octahedral coordination geometries with near C3v symmetry.