Carbon Dioxide Reduction by Pincer Rhodium η2-Dihydrogen Complexes:  Hydrogen-Binding Modes and Mechanistic Studies by Density Functional Theory Calculations

Density functional theory (DFT) calculations using the KMLYP method on a series of pincer PCP−rhodium dihydrogen complexes have been employed to model and examine the proposed mechanisms for the pincer PCP−rhodium complexes mediated hydrogenation of carbon dioxide (CO 2 ). The relative energies of dihydrogen rotamers and dihydride isomers were evaluated together with T 1 values to determine the molecular structures of these complexes. We have investigated possible pathways for the CO 2 reduction processes involving the formation of rhodium dihydride species. Although the dihydrogen complexes are more stable than the corresponding dihydride isomers, the reduction of CO 2 has to proceed through the dihydride structures.