Lewis Base Activation by Uranium(III) Complexes

Abstract

The combination of a bulky hypersilyl potassium [(Me 3 Si) 3 SiK] reagent with Tp* 2 UI (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate) in the presence of ethereal Lewis donors resulted in the formation of base-activated products Tp* 2 U[O(CH 2 ) 4 Si(SiMe 3 ) 3 ] (1-THF) and Tp* 2 U[O(CH 2 ) 2 OMe] (2-DME). The reactivity with another Lewis base, pyridine, was explored by treating Tp* 2 UI and hypersilyl potassium or benzyl potassium in the presence of pyridine, which resulted in formation of Tp* 2 U[NC 5 H 5 -4-Si(SiMe 3 ) 3 ] (3-py-Si) and Tp* 2 U(NC 5 H 5 -4-Bn) (4-py-Bn, Bn = benzyl), respectively. Multinuclear paramagnetic NMR spectroscopy ( 1 H, 11 B{ 1 H}, 29 Si{ 1 H}) supported the formation of the Lewis base activated uranium compounds as corroborated by electronic absorption spectroscopy and X-ray crystallography. To recognize the mechanistic possibilities, radical trap experiments were performed and [K(18-crown-6)][4-benzylpyridinide] (4-K), Tp*U(IV)[(�NC(Me)C(H)C(Me)N)-B(H)(3,5-dimethylpyrazole) 2 ] (6-Tp*UTp′), and [Tp* 2 U(NC 5 H 5 )] 2 (5-py-py) were observed.

Solution and solid-state characterization of rare silyluranium(iii) complexes

“…4). 31 The synthesis of the uranium(III) silyl species reported here is significant as previous derivatives have only featured a very bulky monodentate silyl ligand. Compounds 1 and 1-crown are rare in that two concurrent silyl bonds are formed trans to each other, and there is a relatively unhindered uranium ion that is capable of further chemistry.…”