Computational exploration of ligand effects in copper-catalyzed boracarboxylation of styrene with CO2    

The mechanism and effects of ligands and reagents in Rh-catalyzed C(sp²)–H bond carboxylation with CO₂ were investigated using density functional theory (DFT) calculations. The catalytic cycle involves sequential C–H oxidative addition, CO₂ insertion into the Rh–C(aryl) bond and transmetalation. Among these steps, CO₂ insertion is the rate-determining step. In addition to its role as a methylation reagent, AlMe₂(JOMe) can also serve as a Lewis acid to promote the CO₂ insertion step. The greater reactivity of the catalyst with the bulkier PIJMes) 3 ligand than that with PPh₃ benefits from the favorable agostic interaction between the Rh center and the ortho-methyl group in the P(Mes)₃ ligand, which can stabilize the transition state of CO₂ insertion.