Mono(pentamethylcyclopentadienyl)uranium(III) Complexes: Synthesis, Properties, and X-ray Structures of (η-C₅Me₅)UI₂(THF)₃, (η-C₅Me₅)UI₂(py)₃, and (η-C₅Me₅)U[N(SiMe₃)₂]₂

Abstract

The uranium(III) iodide complex UI3(THF)4 reacts cleanly at ambient temperature with 1 equiv of sodium and potassium pentamethylcyclopentadienide salts in tetrahydrofuran to form the mono-ring uranium(III) complex (η-C5Me5)UI2(THF)3 (1). Additionally, reaction of UI3(THF)4 with 2 equiv or more of K(C5Me5) in THF solution leads to the formation of the bis-ring adduct (η-C5Me5)2UI(THF) (2) in high yield. In the solid state 1 exhibits a pseudo-octahedral mer,trans ligand geometry with the C5Me5 ligand occupying one axial position. U−I bond lengths range from 3.161(1) to 3.179(1) Å, while U−O distances to the THF ligands lie in the range 2.496(8)−2.594(10) Å. 1 also provides a convenient entry into a variety of other mono-ring complexes of uranium(III). In the presence of excess pyridine, the coordinated THF ligands of 1 are readily displaced to form the tris(pyridine) adduct (η-C5Me5)UI2(py)3 (3), which exhibits a mer,trans ligand geometry in the solid state similar to that of 1. Metathesis of the iodide ligands in 1 with 2 equiv of KN(SiMe3)2 affords the bis(amido) complex (η-C5Me5)U[N(SiMe3)2]2 (4). An X-ray diffraction study of this molecule reveals that methyl groups from both amido ligands are involved in agostic interactions with the uranium(III) center.