In this week’s issue of Nature magazine Arnold et al. have published an intriguing reactive complex of the notoriously stable uranyl dication [UO₂]⁺ that cleaves C-Si bonds and yields a functionalized U=O bond. This was accomplished by first encapsulating the UO₂ into a cyclic macrocycle, followed by the addition of the metal (either iron or zinc bound to the inner U=O bond) with a silylamide base. The major product is shown in the figure below.

Reprinted by permission from Macmillan Publishers Ltd: Nature, advance online publication, 17 January 2008 (doi:10.1038/nature06467) The crystal structure was also taken and is shown above. This reactivity was explained by postulating an U(VI) K₂ intermediate not observed. Postulated mechanism below.

Reprinted by permission from Macmillan Publishers Ltd: Nature, advance online publication, 17 January 2008 (doi:10.1038/nature06467)

A solution to the problem of determining the presence of the postulated intermediate might simply be to take mass specs along the course of the reaction; as one described prep takes 42 hours. In the end, this work literally builds the scaffold for future chemists to begin functionalizing uranyl. Although, no mention is given how to un-encapsulate the newly derivatized uranium.

Note 1: Link to article — Reduction and selective oxo group silylation of the uranyl dication

Mitch

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