DFT Study on Co–H Bond Dissociation Enthalpies of Cobalt Hydrides in Metal-Catalyzed Hydrogen Atom Transfer Reactions

Metal-catalyzed hydrogen atom transfer (MHAT) reactions are widely used and nowadays constitute a large class of chemically catalyzed reactions and provide a convenient way to obtain various chemical products and synthesize building blocks. The cobalt compound has been identified as an effective catalyst for MHAT reactions due to its low cost, high abundance, high efficiency and high selectivity, in which the cobalt hydride is an indispensable catalytic active intermediate, and the breakage of cobalt-hydrogen bonds is crucial for the reaction to proceed. Therefore, the Co–H bond dissociation enthalpy (BDE) becomes an extremely significant thermodynamic property. In this report, the Co–H BDEs of some cobalt hydrides were calculated with experimental values by using ten DFT functionals, and the results show that the B97D functional gave the optimal precision with a root mean square error (RMSE) of 3.1 kcal/mol. Next, the BDEs and substituent effects of ten kinds of cobalt hydrides were further investigated. The results show that ligands may remarkably influence the Co–H BDEs and substituent effects on Co-H BDEs vary in different kinds of cobalt hydrides. In addition, analyses on the natural bond orbital (NBO) and the energies of frontier orbitals were performed to reveal more about the variation patterns of the Co–H BDE.