Uranocenium: synthesis, structure and chemical bonding

Abstraction of iodide from [(?5-C5iPr5)2UI] (1) produces the cationic uranium(III) metallocene [(?5-C5iPr5)2U]+ (2) as a salt of [B(C6F5)4]–. The structure of 2 consists of unsymmetrically bonded cyclopentadienyl ligands and a bending angle of 167.82° at uranium. Analysis of the bonding in 2 shows that the uranium 5f orbitals are strongly split and mixed with the ligand orbitals, leading to non-negligible covalent contributions to the bonding. Studying the dynamic magnetic properties of 2 reveals that the 5f covalency leads to partially quenched anisotropy and fast magnetic relaxation in zero applied magnetic field. Application of a magnetic field leads to dominant relaxation via a Raman process.