Theoretical Investigation of Reaction Mechanisms of CoO+ with Propane

Density functional theory (DFT) has been employed to investigate the gas-phase reactions of CoO⁺ with propane. The geometries and energies of all stationary points involved are analyzed at the B3LYP/DZVP(d)(opt+3f)+6-311++G(2df,2pd) level of theory. Three types of stable complexes are identified: two η³- and one η⁴-CoO⁺-C₃H₈ configurations, formed through coordination of the Co center to the α, β, γ-H atoms of propane. Reaction mechanisms involving both C–H and C–C activation pathways are examined. When considering spin inversion, both C–H and C–C activations are important. Without spin inversion, the α,β-H abstraction, mechanism is the most favorable due to its simplicity (direct Cα -to-O H shift) and energetic favorability. The formation of C₃H₇OH occurs via a direct C-to-O hydrogen ,2- and ,,-3-OCo+(C3H8) followed by C–O coupling, while H2O and C3H6 are generated through multiple quintet and triplet pathways involving α,β-H and β,α-H abstraction. Spin-orbit coupling plays a crucial role in these reactions, particularly in intersystem crossing between quintet and triplet potential energy surfaces. The computational results align well with the available experimental data and offer new insights into the specific details of individual elementary steps. This study emphasizes the dynamic role of CoO⁺ in the selective catalytic oxidation of propane, providing a deeper understanding of the chemistry of transition metal oxide ions.