Dimethyl Carbonate Synthesis from CO2 and Dimethoxytin(IV) Complexes: The Anatomy of the Alkylation Step Viewed from DFT Modeling

In line with promoting environmentally acceptable chemical processes, the direct catalytic conversion of CO2 and methanol into dimethyl carbonate (DMC) is a target of current industrial interest. Despite breakthroughs to master thermodynamic limitations, the reaction mechanisms are not well understood for providing keys to boost rate and selectivity. Specifically, the pathways releasing DMC and regenerating the reactive alkoxy moiety are poorly justified. We herein address these steps by density functional theory modeling (DFT) with (CH3)(2)Sn(OCH3)(2). The study complements our kinetics experiments and end-products characterization obtained from Bu2Sn(OCH3)(2) counterpart. Indeed, DMC formation by an intermolecular process between two monomeric stannanes is preferred to that previously reported with the dimer. A following multistep process with methanol is advanced to regenerate the stannanes along with water, thereby promoting a catalytic cycle. Accordingly, dialkyltin(IV) organometallics are unique to promote such a sequence giving opportunity in reactor design to overcome catalyst poisoning as well as thermodynamics limitations.