UN Coaxed to Neutrality

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Science  17 May 2013:
Vol. 340, Issue 6134, pp. 788-789
DOI: 10.1126/science.340.6134.788-d

The enormous quantity of energy released through fission of the uranium (U) nucleus has lent the element a widespread, intimidating reputation. At the lower energies prevailing in conventional chemistry, where electrons rather than neutrons are exchanged, U remains an intriguing target of study, chiefly on account of the involvement off orbitals in its bonding motifs. In this context, a long-sought coordination complex in which U formed a triple bond to nitrogen (N) was recently prepared (King et al., Reports, 10 August 2012, p. 717). The complex had a net negative charge (with U in the ÷5 oxidation state) that was compensated for by a sodium ion and relied for its stability on a protective chelating ligand. King et al. have now built on this prior work to oxidize the U(V) anion and thereby isolate, and structurally characterize, a neutral U(VI) nitride complex. Iodine proved the optimal outer sphere oxidant, and it was necessary that the sodium remain sequestered by a crown ether; attempts to oxidize a dimeric precursor with sodium bridging the terminal Ns led to competing halogenation in the coordination sphere. The U(VI)≡N linkage was prone to photoaccelerated C-H insertion chemistry, perhaps accounting for the failure of prior attempts to generate related motifs photolytically.

Nat. Chem. 5, 10.1038/nchem.1642 (2013).

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