Hydrogen Activation by Frustrated Lewis Pairs Revisited by Metadynamics Simulations

Frustrated Lewis pairs have great potential as metal-free catalysts, for example, for the activation of molecular hydrogen. However, rational design of improved catalysts is hampered because the catalytic reaction mechanisms still remain largely unclear. In this study, we present a density-functional-theory-based metadynamics study of the hydrogen activation by a typical frustrated Lewis pair, tBu₃P/B(C₆F₅)₃. The computed free-energy landscape reveals a different reaction path compared with the ones in the literature. Importantly, we found different roles of the Lewis acid and base centers in the hydrogen activation. The rate-determining step is the hydride transfer to the Lewis acid, and the overall reaction is found to be exothermic once the proton transfer to the Lewis base step is accomplished.