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.