Free energy surfaces generated via ab initio molecular dynamics simulations for H2 activation reactions with intramolecular frustrated Lewis pairs (FLPs) point to a concerted (single-step) mechanism of H–H bond cleavage.… Click to show full abstract
Free energy surfaces generated via ab initio molecular dynamics simulations for H2 activation reactions with intramolecular frustrated Lewis pairs (FLPs) point to a concerted (single-step) mechanism of H–H bond cleavage. Statistical analysis carried out for a large number of reaction trajectories reveals notable asynchronicity in the development of donor-H and acceptor-H bonds with the latter being in a more advanced phase. These findings are fully consistent with the results of static quantum chemical calculations demonstrating that the previously established mechanistic picture of FLP-mediated heterolytic H2 cleavage remains plausible in a finite temperature dynamic model as well. As a consequence of asynchronicity, the excess kinetic energy released upon H2 cleavage is stored in the form of donor-H bond vibrations, which may influence the mechanism of catalytic hydrogenation.
               
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