Reaction of (Bisimido)niobium(V) Complexes with Organic Azides: [3 + 2] Cycloaddition and Reversible Cleavage of β‑Diketiminato Ligands Involving Nitrene Transfer

We describe the unusual reactivity of a highly labile diethyl ether adduct of an asymmetric niobium­(V) bis­(imide) 2.OEt2 containing the mono­azabuta­diene (MAD) ligand. This species undergoes clean nitrene transfer on treatment with tert-butyl- or di-iso­propyl­phenyl azide resulting in the unprecedented reformation of nacnac ligands bound to the metal center. Corresponding reactions with tri­methyl­silyl- or tert-butyl azide allowed the isolation of two rare intermediates prior to N2 loss; mechanistic studies support the involvement of two different niobium species.