Regioselective [2+2] and [4+2] cycloaddition reactivity in an asymmetric niobium(bisimido) moiety towards unsaturated organic molecules.

The asymmetric bis-imido structure and the lability of the diethyl ether linkage in complex 1 provide a niobium complex that undergoes regioselective [4+2] cycloaddition reactions with an α,β-unsaturated ketone and cycloaddition reactions that involve bond formation to the MAD ligand (MonoAzabutaDiene). DFT calculations have been used to support an initial azametallacyclobutene intermediate in the alkyne reaction.