Uranium-Nitrogen Multiple Bonding: The Case of a Four-Coordinate Uranium(VI) Nitridoborate Complex

摘要

While uranium imido complexes are well established in the literature, complexes featuring a uranium nitride functionality are rare. Data pertaining to terminal uranium nitrides are limited to the spectroscopic observation of the binary uranium nitrides UN and NUN and the ternary nitride NUF_3 under matrix conditions. We are interested in the uranium nitride functional group as it incorporates metal-ligand multiple bonding, valence f orbitals, and redox activity. rnOne typical route to metal nitride species involves the reaction of azide anion with reducing metal complexes. In uranium chemistry, this approach had led to bi- and polymetallic complexes with μ-nitrido ligands bridging two or more uranium centers. We posited that use of an azide salt complexed by a simple Lewis acid would deliver a protected nitride ligand to uranium without bimetallic complex formation. Accordingly, we now report the synthesis and characterization of the first nitridoborate complexes of uranium, complexes that alternatively may be viewed as borane-capped uranium nitrides (Scheme 1).