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The terminal uranium nitride linkage is a fundamental target in the study of f-orbital participation in metal-ligand multiple bonding but has previously eluded characterization in an isolable molecule. Here, we report the preparation of the terminal uranium (V) nitride complex UN (Tren (TIPS) ) Na (12-crown-4) (2) in which Tren (TIPS) = N (CH (2) CH (2) NSiPr (i) (3) ) (3) (3-) and Pr (i) = CH (CH (3) ) (2) by reaction of the uranium (III) complex U (Tren (TIPS) ) with sodium azide followed by abstraction and encapsulation of the sodium cation by the polydentate crown ether 12-crown-4. Single-crystal x-ray diffraction reveals a uranium-terminal nitride bond length of 1. 825 (15) angstroms (where 15 is the standard uncertainty). The structural assignment is supported by means of (15) N-isotopic labeling, electronic absorption spectroscopy, magnetometry, electronic structure calculations, elemental analyses, and liberation of ammonia after treatment with water.
King et al. (2012) studied this question.