A computational mechanistic study of the cleavage of sulfur-sulfur bond by Frustrated Lewis Pairs

DFT calculations were performed to gain insight into the detailed mechanism of S-S bond cleavage in disulfides (i.e., iPrSSiPr) by a frustrated Lewis pair (FLP) (tBu)3P/B(C6F5)3. The calculations revealed that the reaction initiates from the generation of weak complex B(C6F5)3/iPrSSiPr (IM1) between iPrSSiPr and Lewis acid B(C6F5)3. Subsequently, the Lewis base (tBu)3P can activates the S-S bond leading to the final cleavage of S-S bond to give the product [(tBu)3P(SiPr)][(iPrS)B(C6F5)3] (PR). The computed kinetics and thermodynamics suggest that the reaction can take place reversibly under ambient condi-tions, which accounts well for the experimental observations. Furthermore, the mechanism is compared with that of the H-H bond cleavages by same FLP. Contrast to the H-H bond cleavage, a weak donor- acceptor complex IM1 between iPrSSiPr and B(C6F5)3 could be located before S-S bond cleavage. Nonetheless, the complete S-S bond cleavage essentially is still due to the synergistic catalytic Lewis acid/base effects of FLP (tBu)3P/B(C6F5)3.(c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

DFT calculations were used to investigate the mechanism of S-S bond cleavage in disulfides by a frustrated Lewis pair. The calculations revealed that the reaction proceeds through the formation of a weak complex between the disulfide and the Lewis acid. The S-S bond can be activated by the Lewis base leading to its cleavage and the formation of the desired product. The mechanism was compared to that of H-H bond cleavages and it was found that a weak donor-acceptor complex is formed before S-S bond cleavage.