Iron-Mediated Amination of Hydrocarbons in the Gas Phase

FeNH+ is chosen as a model system to probe the transition-metal-mediated transfer of imine groups in the gas phase by mass-spectrometric means. Ab initio calculations at the MR-ACPF level predict FeNH+ to have a linear sextet ground state (6Σ+); a bent quartet state (4A′) and a linear doublet state (2Δ) are higher in energy by 0.14 eV and 0.51 eV, respectively. The bond-dissociation energy is determined to D(Fe+−NH)=69±2 kcal mol−1 using ion-molecule reactions. Charge-stripping experiments combined with ab initio calculations yield an ionization energy of IE(FeNH+)=15.7±0.5 eV. The chemical behavior of FeNH+ towards oxygen, water, hydrogen, aliphatic hydrocarbons, benzene, and toluene reveals an intrinsically high reactivity of FeNH+. Because a transfer of the 〈NH〉 fragment to the substrate is feasible in most cases, attractive amination reactions like methane→methylamine, benzene→aniline, or toluene→benzylidenamine can be afforded by FeNH+.