Accessing a Highly Reducing Uranium(III) Complex through Cyclometalation

Abstract

High Resolution Image Download MS PowerPoint Slide U(IV) cyclometalated complexes have shown rich reactivity, but their low oxidation state analogues still remain rare. Herein, we report the isolation of [K(2.2.2-cryptand)][U III {N(SiMe 3 ) 2 } 2 (κ 2 -C,N–CH 2 SiMe 2 NSiMe 3 )], 1, from the reduction of [U III {N(SiMe) 2 } 3 ] with KC 8 and 2.2.2-cryptand at room temperature. Cyclic voltammetry studies demonstrate that 1 has a reduction potential similar to that of the previously reported [K(2.2.2-cryptand)][U II {N(SiMe) 2 } 3 ] (E pc = −2.6 V versus Fc +/0 and E pc = −2.8 V versus Fc +/0, respectively). Complex 1, indeed, shows similar reducing abilities upon reactions with 4,4′-bipyridine, 2,2′-bipyridine, and 1-azidoadamantane. Interestingly, 1 was also found to be the first example of a mononuclear U(III) complex that is capable of reducing pyridine. In addition, it is shown that a wide variety of substrates can be inserted into the U–C bond, forming new U(III) metallacycles. These results highlight that cyclometalated U(III) complexes can serve as versatile precursors for a broad range of reactivity and for assembling a variety of novel chemical architectures.

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