Recent synthetic access to U(IV � VI) mono- and bis(imido) complexes has allowed us to begin to explore the reactivity of these compounds. The reactivity of the imido groups differs significantly as the oxidation state of the metal increases. Reaction of the U(IV) mono(imido) complexes with isocyanates proceeds via 2+2 cycloaddition of the isocyanate with the imido group, giving isolable ureate complexes. Reaction of isocyanates with U(VI) imido complexes leads to imido exchange that likely proceeds through a 2+2 cycloadduct as an intermediate. In the case of nitriles, U(IV) imidos undergo cycloaddition chemistry while U(VI) imidos react by ligand exchange. This chemistry can be explained by differences in the U=NR bonding as a function of oxidation state. We have also discovered that the U=NR multiple bond can be generated via H atom abstraction from uranium amides (U-NHR). This chemistry is similar to that observed in transition metal chemistry and provides a new route for the generation of U imido complexes. The generality of this novel actinide reactivity will also be discussed.

Cycloaddition vs. imido exchange: The role of covalency in the reactivity of uranium(IV-VI) mono- and bis-imido complexes

245th National Meeting (2013)

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