A Quantum Chemical View on the Mechanism of the Ta⁺-Mediated Coupling of Carbon Dioxide with Methane

Abstract

The mechanistic details of the coupling of methane and carbon dioxide mediated by a bare tantalum cation observed experimentally in the gas phase have been unraveled by means of quantum chemical calculations employing approximate density functional theory. All relevant intermediates and saddle points along the reaction coordinate have been located on the singlet and triplet potential energy surfaces. The energetically most favorable path has been identified and is characterized by several changes of the spin multiplicity. The reaction mechanism predicted by our calculations is in harmony with the available experimental information but provides additional information into the various elementary steps of this reaction, which could not be obtained by experimental means.