Understanding the Reactivity of Neutral Geminal Group 14 Element/Phosphorus Frustrated Lewis Pairs

Abstract

The influence of the nature of the group 14 elements (E = Si, Ge, Sn) on the reactivity of (F 5 C 2 ) 3 E− CH 2 −P(tBu) 2 geminal frustrated Lewis pairs (FLPs) has been computationally explored by means of density functional theory calculations. To this end, the experimentally described activation reactions of CO 2 and phenyl isocyanate have been investigated and compared to the analogous processes involving the corresponding B/P geminal FLP. It is found that the reactivity of these species is kinetically enhanced when going down the group 14 (Si < Ge < Sn). This trend of reactivity is quantitatively analyzed in detail by means of the activation strain model of reactivity in combination with the energy decomposition analysis method, which identify the interaction energy between the deformed reactants as the main factor controlling the reactivity of these group 14 containing geminal FLPs.

Investigating Tetrel-Based Neutral Frustrated Lewis Pairs for Hydrogen Activation

“…These two synergistic interactions develop further with the advancement of the reaction, resulting in the progressive weakening of the H–H bond, which ultimately leads to the formation of product 2 . Note that Fernandez and co-workers reported a similar electron donation from the isocyanate moiety to the σ*­(E–R) orbital during their computational investigation of the reaction between PhCNO and these intramolecular FLP systems …”

“…The stronger interaction energy of 1-Sn-P can be rationalized by its low-lying LUMO (see Table S3) compared to 1-Si-P and 1-Ge-P , leading to a more favorable interaction with the σH 2 orbital. Note that Fernandez and co-workers also reported a stronger interaction energy and less destabilizing strain energy for 1-Sn-P during its reaction with PhCNO . Moreover, in the case of 1-Si-P and 1-Ge-P , while the ΔE int terms are almost superimposed along the reaction pathway, the ΔE strain term, which is the distortion energy experienced by the reactants during the transformation, widely differs for them, and the highest energy barrier for 1-Ge-P can be easily justified by its higher ΔE strain value.…”

Lewis Acidity of Carbon in Activated Carbonyl Group vs. B(C6F5)3 for Metal‐Free Catalysis of Hydrogenation of Carbonyl Compounds

“…The FLP chemistry has been subject of many EDA studies in the recent years. [40][41][42][43][44][45] activated) compounds 1-4 in eV are À 1.98, À 2.86, À 3.27, and À 3.45, respectively. Depending on the activation method and substitution on the carbonyl group, the LUMO energy decreases versus the corresponding free carbonyl compounds up to 3.5 eV (e. g. in case of H + activation of LA 4 it decreases to À 7.00 eV).…”

“…Δ E disp ( ζ) is the dispersion energy due to Van der Waals attractions. The FLP chemistry has been subject of many EDA studies in the recent years [40–45] …”

Recent Advances in Group 14 and 15 Lewis Acids for Frustrated Lewis Pair Chemistry

“…Interestingly, the CO 2 uptake by Sn/P FLP was found to be reversible which indicates its ability to reversibly bind oxygen‐containing molecules. The computational investigation [56] by Fernandez et al . reveals a cooperative interaction during the reaction between the small molecule i.e CO 2 , PhNCO and (C 2 F 5 ) 3 ECH 2 P(tBu) 2.…”