Synthetic Utility of Tetrabutylammonium Salts in Uranium Metallocene Chemistry

Tetrabutylammonium chloride and nitrate salts react with (C₅Me₅)₂UCl₂ to expand the coordination sphere of the metallocene to form the formal 9- and 10-coordinate complexes, [NBu₄]­[(C₅Me₅)₂UCl₂(NO₃)], 1, and [NBu₄]­[(C₅Me₅)₂UCl₂(NO₃)], 2, respectively. Complex 2 displays modified reactivity compared to that of (C₅Me₅)₂UCl₂ in substitution reactions with Khpp [hpp =1,3,4,6,7,8-hexahydro-2H-pyrimido­(1,2-a)­pyrimidine] and K­(NC₄Me₄) in the synthesis of (C₅Me₅)₂U­(hpp)­Cl, (C₅Me₅)­U­(hpp)₃, and (C₅Me₅)₂U­(NC₄Me₄)­Cl. The U³⁺ complex, [NBu₄]­[(C₅Me₅)₂UCl₂], can be formed by reduction of 2 with K­(Hg), as well as with KC₅Me₅, K₂C₈H₈, and Li₃N.