Reaction mechanisms for C-O bond coupling from Pt₄CH ₂⁺ and O₂: A relativistic density functional study

Computational investigations on the reaction of Pt₄CH ₂⁺ with O₂ have been carried out by the relativistic density functional approach. Calculations indicate that the reactivity of Pt₄CH₂⁺ toward O₂ is different from the metallic carbene PtCH₂⁺. The dehydrogenation route in the reaction of Pt₄CH₂ ⁺ with O₂ is quite unfavorable, both dynamically and thermodynamically. The reaction channels to products H₂O/CO and HCOOH with involvement of O-O bond activation and C-O bond coupling are strikingly exothermic, where the C-O bond coupling and the release of CO are the crucial steps for the entire reaction channels. Predicted overall Gibbs free energies of reaction ΔG are -66.2 kcal mol^-1 for H₂O/CO and -73.5 kcal mol^-1 for HCOOH, respectively. Both energy-favored routes have thus relatively high reaction efficiencies toward O₂ in comparison with dehydrogenation. On the basis of theoretical results, plausible mechanisms for the reaction of Pt₄CH₂⁺ with O₂ and candidates for the experimental neutral products [C, H ₂, O₂] in reaction have been proposed.