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

A nickel complex incorporating an N2O 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 15N‐labeling experiments. The isoelectronic nickel CO2 complex reported for comparison features a very similar solid‐state structure. Computational studies revealed that η2‐N2O 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 N2O complex. The characterization of η2‐N,N′‐N2O and CO2 complexes of nickel and the associated computational study reveal that the bonding ability of N2O to nickel is intermediate between that of CO2 and that of H2C=CH2. It is shown that in general, N2O η2‐binds to metals comparably to or stronger than CO2, indicating that the rarity of η2‐N2O metal complexes is due mostly to its oxidizing character and not to its weak σ‐donating and π‐accepting properties.