Side-on Coordination in Isostructural Nitrous Oxide and Carbon Dioxide Complexes of Nickel

A nickel complex incorporating an N₂ O ligand with a rare η² -N,N'-coordination mode was isolated and characterized by X-ray crystallography, as well as by IR and solid-state NMR spectroscopy augmented by ¹⁵ N-labeling experiments. The isoelectronic nickel CO₂ complex reported for comparison features a very similar solid-state structure. Computational studies revealed that η² -N₂ O binds to nickel slightly stronger than η² -CO₂ in this case, and comparably to or slightly stronger than η² -CO₂ to transition metals in general. Comparable transition-state energies for the formation of isomeric η² -N,N'- and η² -N,O-complexes, and a negligible activation barrier for the decomposition of the latter likely account for the limited stability of the N₂ O complex.