No abstract

The uranium(III) iodide complex UI 3 (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-C 5 Me 5 )UI 2 (THF) 3 (1). Additionally, reaction of UI 3 (THF) 4 with 2 equiv or more of K(C 5 Me 5 ) in THF solution leads to the formation of the bis-ring adduct (η-C 5 Me 5 ) 2 UI(THF) (2) in high yield. In the solid state 1 exhibits a pseudooctahedral mer,trans ligand geometry with the C 5 Me 5 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-C 5 Me 5 )UI 2 (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(SiMe 3 ) 2 affords the bis(amido) complex (η-C 5 Me 5 )U[N(SiMe 3 ) 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.

The pentamethylcyclopentadieny1)uranium-(III) complex ( !&fe5)UIz(THF)3 reacts with KZcg& in THF to form :he mixed-ring uranium(III) complex (C~&)(C&fe5) r(THF) ( I ) . Treatment of 1 with 4,4'-dimethyl-2,Z-bipyridine (Mezbpy) gives the 10-coordinate complex (C&)(Cdtde5)U(Mezbpy) (2). The synthesesof landzand theX-raystructureofzaredescribed her e i n .Transition-metal' and lanthanide2 mixed cyclopentadienyl-cyclooctatetraenyl complexes were reported in the late 1960s and mid-19708, respectively. However, to date, there have been no reports of the incorporation of this combination of ring systems on a uranium(1II) metal center and, until recently? this combination of ring systems had not been used on any actinide metal center. Our interest in this ligand combination stems from its unique ability to offer multiple coordination sites and, hence, multiple sites of reactivity at a neutral, electrophilic metal center in a pseudo-bent-metallocene coordination sphere. Here we report our preliminary results on the synthesis and characterization of the first mixed-ring uranium(II1) complex.

No abstract