Ab initio investigation on the mechanism of SO₂ activation by P/B intermolecular frustrated Lewis pairs

In silico study investigates the activation of sulfur dioxide by newly designed frustrated Lewis pairs, i.e., [P(^tBu)₃…B(C₂NBSHF₂)₃], where the Lewis acid part is a super Lewis acid. The activation process involves the making of P–S and B–O bonds, leading to the formation of an FLP-SO₂ adduct. The calculated results demonstrate that the activation of SO₂ by the FLP is almost barrierless and exothermic. Exploration of the impact of the solvent environment on the feasibility and energetics of the reaction has been investigated. The exothermicity is increasing in nonpolar solvents.

This study focuses on understanding the electronic activity of SO₂ activation by FLP with the help of the Minnesota 06 functional, M06-2X (global hybrid functional with 54% HF exchange) along with Pople’s basis set, 6-311G (d, p). Principal interacting orbital and extended transition state–natural orbitals for chemical valence studies, giving impactful insight into the favorable orbital interaction and electron transfer in this reaction. Furthermore, useful CDFT descriptors such as reaction force constant and reaction electronic flux profiles along the intrinsic reaction coordinate give insights into the synchronicity and total electronic activity of the reaction.