Trans Influence of Boryl Ligands in CO2 Hydrogenation on Ruthenium Complexes: Theoretical Prediction of Highly Active Catalysts for CO2 Reduction

In this work, we study the trans influence of boryl ligands and other commonly used non-boryl ligands in order to search for a more active catalyst than the ruthenium dihydride complex Ru(PNP)(CO)H-2 for the hydrogenation of CO2. The theoretical calculation results show that only the B ligands exhibit a stronger trans influence than the hydride ligand and are along increasing order of trans influence as follows: -H < -BBr2 < -BCl2 & AP; -B(OCH)(2) < -Bcat < -B(OCH2)(2) & AP; -B(OH)(2) < -Bpin < -B(NHCH2)(2) < -B(OCH3)(2) < -B(CH3)(2) < -BH2. The computed activation free energy for the direct hydride addition to CO2 and the NBO analysis of the property of the Ru-H bond indicate that the activity of the hydride can be enhanced by the strong trans influence of the B ligands through the change in the Ru-H bond property. The function of the strong trans influence of B ligands is to decrease the d orbital component of Ru in the Ru-H bond. The design of a more active catalyst than the Ru(PNP)(CO)H-2 complex is possible.