Schematic Design of Metal-Free NHC-Mediated Sequestering and Complete Conversion of SO₂ to Thiocarbonyl S-Oxide Derivatives at Room Temperature

Abstract

The sequestering and complete conversion of SO 2 to valuable chemicals in a metal-free pathway is highly demanded. The recent success of SO 2 fixation by N-heterocyclic carbenes instigated further studies in this regard. Previous reports were confined within the carbene−SO 2 reaction mechanism and the stability of oxathiirane S-oxide derivatives. The complete conversion of captured SO 2 to precious chemicals was not studied. The present inquisition has accomplished the scarcity of the earlier studies. It is observed that in the presence of an excess amount of carbene, the registered SO 2 is converted to the ketone derivative and thiocarbonyl S-oxide derivative. An electronic level investigation of these reactions is carried out. From the change of the molecular orbitals along the reaction path, it is concluded that the reaction between the oxathiirane S-oxide derivative and carbene follows a frog's hunting mechanism.

Sequestering and metamorphosis of molecular nitrogen at ambient conditions: role of bonding and back-bonding

“…This methodology involves electronic structure analysis at variable geometry along the reaction path and is termed Intrinsic Reaction Coordinate trapping. 7 Intrinsic Reaction Coordinate (IRC) is acquainted as the lowest energy path on the potential energy surface (PES) that connects the reactants to the product(s) through a transition state. It is trivial to construct the intermediate geometries along the reaction path using available computational chemistry programs.…”

“…21 The N 2 fixation by the non-metallic process has also attracted attention very recently. [22][23][24][25][26][27] In this new research avenue with the rapid development of carbene chemistry and its applications, 7,[28][29][30][31][32][33][34][35][36][37][38] carbenes are the front runners for the candidature of the N 2 sequestering agent. 23 The possibility of nitrogen fixation by carbene was first reported in 1964 by Moore et al 39 It is exhibited that methylene reacts with N 2 in matrix solution to form diazomethane.…”

“…24,[43][44][45] Carbene-boron is one such FLP that has been recognized as a significant candidate for sequestering of N 2 . [43][44][45] In 2019, Zhu et al 7 In this method, a pair of the same carbenes, as well as different carbenes, are equally effective for sequestering and complete conversion of SO 2 . From these two studies, 7,22 it could be concluded that the use of persistent carbene pair may be more effective for small molecule activation and conversion.…”

“…37 Very recently we reported that the modeling of proper carbenes, particularly, N-heterocyclic carbenes, is effective for the sequestering and conversion of SO 2 to valuable chemicals. 7,37,38 These carbenes are also highly reactive to N O 2 . 38 The success of these studies motivates us to extend our studies with these carbenes for N 2 activation.…”

“…The electronic mechanism of the nitrogen activation process by carbene is investigated using the IRC trapping method explained in our previous work. 7…”