On the performance of the M–C (M = Fe, Ru, Os) unit toward methane activation

Abstract

Gas-phase reactions of [MC]⁺ (M = Os and Ru) with methane at ambient temperature have been studied by using quadrupole-ion trap (Q-IT) mass spectrometry combined with quantum chemical calculations. Theoretical calculations reveal the influence of electronic signatures and that it is the energy gap of the associated frontier molecular orbitals that dominates the ability of the cluster in the initial H₃C–H bond breaking. By extension, a theoretical consideration upon changing the ligand from carbide to carbyne and eventually to carbene reveals that the reactivities of the M-complex (M = Os, Ru and Fe) are determined by the energy gap of the involved orbitals. In addition, a few factors like the dipole moment, spin density and charge distributions influence the orbital energy gap to different extents. Thus, altering the local structure of the active center to modulate the orbital distribution may be a possible means of regulation of the activity.