Aromaticity-promoted CS2 activation by heterocycle-bridged P/N-FLPs: a comparative DFT study with CO2 capture

Abstract

Carbon dioxide (CO₂) capture has attracted considerable attention from both experimental and theoretical chemists. In comparison, carbon disulfide (CS₂) activation is less developed. Here, we carry out a thorough comparative density functional theory study to examine the reaction mechanisms of CS₂ activation by five-membered heterocycle-bridged P/N frustrated Lewis pairs (FLPs). Calculations suggest that despite a weaker carbon–sulfur bond, all the CS₂ activations have higher reaction barriers than the CO₂ capture, which could be attributed to electrostatic repulsion between FLPs and CS₂ caused by the reversed polarity of CS in CS₂ rather than the electrostatic attraction in CO₂ capture. In addition, aromaticity is found to play an important role in CS₂ capture as it stabilizes both the transition states and products in heterocycle-bridged FLPs. All these findings could be useful for experimentalists to realize small molecule activations by FLPs.