Influence of the Element and Substituent Effects on the Reactivity of Catching Reactions of Difluorocarbene by Benzene-Bridged and Group-13/Group-15-Based Frustrated Lewis Pairs.

The trapping reactions of CF 2 by benzene-bridged Group-13/P-based and B/Group-15-based frustrated Lewis pairs (FLPs) have been computationally investigated based on density functional theory. Interestingly, our theoretical calculations predict that the capture of CF 2 by all five Group-13/P-based FLPs is energetically feasible. However, in the B/Group-15-based FLPs, only the phosphorus-based B/P-FLP can trap CF 2 from kinetic and thermodynamical viewpoints. According to the analyses of the activation strain model, it can be known that the atomic radius of the G15 element (Lewis base) of benzene-bridged B/Group-15-FLP plays an important role in controlling the reactivity of the CF 2 catching reactions, whereas the atomic radius of the Group-13 center (Lewis acid) does not play a role in influencing the activation barrier of these CF 2 catching reactions. Our theoretical findings based on sophisticated methods suggest that the forward bonding is the FLP-to- CF 2 interaction, the LP (Group-15-donor) → vacant p-π-orbital ( CF 2 ), which was quantitatively proved to be strong in such present CF 2 catching reactions. However, the back bonding is the CF 2 -to-FLP interaction, the empty σ-orbital (Group-13-acceptor) ← sp 2 -σ-orbital ( CF 2 ), which was verified to be relatively weak. Our theoretical pieces of evidence reveal that the stronger electron-donating ability of the substituents is attached to the Lewis basic center and can make the reaction barrier of the benzene-bridged Group-13/Group-15-based FLP-related compound catching CF 2 smaller and more exothermic.