Observation of inserted oxocarbonyl species in the tantalum cation-mediated activation of carbon dioxide dictated by two-state reactivity

Reductive activation of carbon dioxide (CO2) has drawn increasing attention as an effective and convenient method to unlock this stable molecule, especially via transition metal-catalyzed reactions. Taking the [TaC4O8]+ ion-molecule complex formed in the laser ablation source as a representative, the reactivity of the tantalum metal cation towards CO2 molecules is explored using infrared photodissociation spectroscopy combined with quantum chemical calculations. The strong absorption in the carbonyl stretching region provides solid evidence for the insertion reactions into C00000000000000000000000000000000111111110000000011111111000000000000000000000000O bonds by the tantalum cation. Two inserted oxocarbonyl products are identified based on the great agreement between the experimental results and simulated infrared spectra of energetically low-lying structures in the singlet and triplet states. The pivotal role of two-state reactivity in driving CO2 activation among three different spin states is rationalized by potential energy surface analysis. Our conclusion provides valuable insight into the intrinsic mechanisms of CO2 activation by the tantalum metal cation, highlighting the affinity of tantalum for CO bond insertion in addition to typical end-on binding configurations. The production of inserted oxocarbonyl species in the carbon dioxide activation by tantalum cations was identified using infrared photodissociation spectroscopy, where the oxygen atom transfer reactions are driven by two-state reactivity.

Automated summary

This study investigates the mechanism of carbon dioxide activation using infrared spectroscopy and quantum chemical calculations, with tantalum metal cations as a representative. The results show that the tantalum ions insert into the C-O bonds of CO2, forming oxocarbonyl products. Potential energy surface analysis reveals the pivotal role of two-state reactivity in driving CO2 activation.