Solvent and Substituent Effects on the Phosphine + CO2 Reaction

Abstract

A theoretical study of the substituent and solvent effects on the reaction of phosphines with CO2 has been carried out by means of Møller-Plesset (MP2) computational level calculations and continuum polarizable method (PCM) solvent models. Three stationary points along the reaction coordinate have been characterized, a pre-transition state (TS) assembly in which a pnicogen bond or tetrel bond is established between the phosphine and the CO2 molecule, followed by a transition state, and leading finally to the adduct in which the P–C bond has been formed. The solvent effects on the stability and geometry of the stationary points are different. Thus, the pnicogen bonded complexes are destabilized as the dielectric constant of the solvent increases while the opposite happens within the adducts with the P–C bond and the TSs trend. A combination of the substituents and solvents can be used to control the most stable minimum.

Sequestration of CO2by Phosphatrane Molecules

“…Furthermore, we have already calculated and analysed possible formation of complexes and adducts between a variety of phosphines and CO 2 molecule, and provided and insight of the solvent and substituent effects on the stationary points along the R 3 P⋅⋅⋅CO 2 reaction path …”

“…The intermolecular distances (Table ) between P(1) and the interacting oxygen atom (between 3.25 and 3.61 Å) indicate that the two atoms are located at the limit of the sum of vdW radii (3.32 Å) . Similar distance range was previously observed in phophinines:CO 2 complexes in which CO 2 donates into the P σ‐hole . Thus, the complexes found present a weak pnicogen bonds …”

“…The second minima found is an adduct with short P(1)‐C(3) distances (between 1.90 and 1.96 Å). This geometry is similar to that found for the adducts previously reported based on theoretical methods or found in the CSD (Refcodes MALRAV and WAXGIO). This distance evolves with the PZ system considered, being NPN<PP∼PN, while it appears to be less sensitive to the size of [X.X′.X′′], slightly varying across the phosphatranes.…”

“…[32] Similar distance range was previously observed in phophinines:CO 2 complexes in which CO 2 donates into the P σ-hole. [31] Thus, the complexes found present a weak pnicogen bonds. [33] The second minima found is an adduct with short P(1)-C(3) distances (between 1.90 and 1.96 Å).…”

“…[30] Furthermore, we have already calculated and analysed possible formation of complexes and adducts between a variety of phosphines and CO 2 molecule, and provided and insight of the solvent and substituent effects on the stationary points along the R 3 P···CO 2 reaction path. [31] In the present article, we bring our attention to answer the following question: can phosphatranes sequestrate CO 2 and eventually form stable complex and adducts? For such purpose the stationary points along the reaction pathway of CO 2 with three families of phosphatranes have been considered (Scheme 1).…”