Sulfur Dioxide Activation: A Theoretical Investigation into Dual SO Bond Cleavage by Three-Coordinate Molybdenum(III) Complexes RobinsonRobert AbbasiKiana Khadem AriafardAlireza StrangerRobert YatesBrian F. 2015 Cummins et al. have observed that 3 equiv of Mo­(N­[R]­Ar)<sub>3</sub> (R = C­(CD<sub>3</sub>)<sub>2</sub>CH<sub>3</sub>, Ar = 3,5-C<sub>6</sub>H<sub>3</sub>Me<sub>2</sub>) are required for dual SO bond cleavage within a SO<sub>2</sub> molecule. Using density functional theory calculations, this theoretical study investigates a mechanism for this SO<sub>2</sub> cleavage reaction that is mediated by MoL<sub>3</sub>, where L = NH<sub>2</sub> or N­[<sup><i>t</i></sup>Bu]­Ph. Our results indicate that an electron transfers into the SO<sub>2</sub> ligand, which leads to Mo oxidation and initiates SO<sub>2</sub> coordination along the quartet surface. The antiferromagnetic (AF) nature of the (NH<sub>2</sub>)<sub>3</sub>Mo–SO<sub>2</sub> adduct accelerates intersystem crossing onto the doublet surface. The first SO bond cleavage occurs from the resulting doublet adduct and leads to formation of L<sub>3</sub>MoO and SO. Afterward, the released SO molecule is cleaved by the two remaining MoL<sub>3</sub>, resulting in formation of L<sub>3</sub>MoS and an additional L<sub>3</sub>MoO. This mononuclear mechanism is calculated to be strongly exothermic and proceeds via a small activation barrier, which is in accordance with experimental results. An additional investigation into a binuclear process for this SO<sub>2</sub> cleavage reaction was also evaluated. Our results show that the binuclear mechanism is less favorable than that of the mononuclear mechanism.