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.

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