Density Functional Theory Studies of the Catalyst Structure–Activity and Selectivity Relationships in Rh(I)-Catalyzed Transfer C–H Borylation of Alkenes

We report the results of a computational investigation that shed light on the catalyst structure–activity and selectivity relationships for our recently developed Rh­(I)-xantphos-catalyzed transfer C–H borylation of alkenes. Our study uncovered the influence that the ligand properties have on the free energy surfaces of the reactions catalyzed by a series of Rh catalysts bearing derivatives of the xantphos ligand with varied electronic features and steric demands. We present the full reaction profiles and provide a closer look on how different modifications to the ligand structure influence each step of the catalytic reaction. We observed that the increased steric effects have a large effect on the free energy surfaces, increasing the energy barriers, thereby decreasing the rates of the reaction. In turn, the electronic effects can stabilize key transition states and destabilize crucial intermediates, such as the resting of the catalyst, thus accelerating the overall catalytic process. Additionally, the electronic effects can modify the relative rates of the alternative pathways and therefore affect the selectivity preferences. In general, our study provides guidelines for the rational development of new catalysts to further enhance the performance of the catalytic system and address the remaining challenges.