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

摘要

We describe the unusual reactivity of a highly labile diethyl ether adduct of an asymmetric niobium(Ⅴ) bis(imide) 2.OEt_2 containing the mono-azabutadiene (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 N_2 loss; mechanistic studies support the involvement of two different niobium species.