Theoretical Characterization of Stable (eta)^1-N2O-, (eta)^2-N2O-, (eta)^1-N2-, and (eta)^2-N2-Bound Species: Intermediates in the Addition Reactions of Nitrogen Hydrides with the Pentacyanonitrosylferrate(II) Ion

The addition of nitrogen hydrides (hydrazine, hydroxylamine, ammonia, azide) to the pentacyanonitrosylferrate(II) ion has been analyzed by means of density functional calculations, focusing on the identification of stable intermediates along the reaction paths. Initial reversible adduct formation and further decomposition lead to the (eta)^1- and (eta)^2-linkage isomers of N2O and N2, depending on the nucleophile. The intermediates (adducts and gas-releasing precursors) have been characterized at the B3LYP/6-31G** level of theory through the calculation of their structural and spectroscopic properties, modeling the solvent by means of a continuous approach. The (eta)^2-N2O isomer is formed at an initial stage of adduct decompositions with the hydrazine and azide adducts. Further conversion to the (eta)^1-N2O isomer is followed by Fe-N2O dissociation. Only the (eta)^1-N2O isomer is predicted for the reaction with hydroxylamine, revealing a kinetically controlled N2O formation. (eta)^1-N2 and (eta)^2-N2 isomers are also predicted as stable species.