Phosphorus ylides as a new class of compounds in CO2 activation: Thermodynamic and kinetic studies

- Phosphorus ylides were examined computationally for carbon dioxide activation.
- P-ylide-CO2 adducts, having lower Vmin values, are better organocatalyst for CO2 transformation.
- Hyperconjugation and negative hyperconjugation effects were investigated by the topological properties.
- P-ylides having the aliphatic and aromatic chains are the best candidates from the kinetic viewpoint.

Phosphorus ylides (P-ylides) including aliphatic or aromatic chains bonded to phosphorous atom and P-ylides containing NR2 groups are two kinds of P-ylides that are considered in carbon dioxide activation processes. Based on theoretical results an acceptable correlation between the Gibbs energy of the reaction and the minimum of the molecular electrostatic potential (MESP) (Vmin) was obtained. The product of the reaction is P-ylide-CO2 adducts. Because of a more negative character of the Vmin values, these adducts are potentially better organocatalysts than the P-ylides for CO2 transformation. Also, natural bond orbital (NBO) analyses show that hyperconjugation and negative hyperconjugation effects are responsible for the magnitude of the electron density of the bond between nucleophilic carbon and phosphorous atom. These effects have a remarkable influence on the kinetic behavior of P-ylides along the CO2 activation. Finally, it can be concluded that P-ylides containing aliphatic chains such as P(Me)3CH2, P(Et)3CH2 are kinetically and thermodynamically more efficient in CO2 activation than the other ones.

Compilation the activity of phosphorus ylides in CO2 activation.142