Hydrogenation mechanisms molecular hydrogen, activation

While the activation of H2 to give M-H bonds in soluble metal complexes and their use in homogeneous hydrogenations has been the subject of innumerable investigations and is now well understood, thanks to extensive NMR and IR spectroscopic and kinetic measurements, the actual mechanism of the activation of H2 on a metal surface and its transfer to an organic substrate, although understood in general terms, still lacks some detailed information at the molecular level. 

A review has illustrated the importance of atomic-level DFT studies in elucidation of the function of hydrogen bonds in organocatalytic reactions through influence on the mechanism of substrate activation and orientation, and the stabilization of transition states and intermediates. Examples discussed include stereoselective catalysis by bifunctional thioureas, solvent catalysis by fluorinated alcohols in epoxidation by hydrogen peroxide, and intra-molecular cooperative hydrogen bonding in trans-a,a -(dimethyl-l,3-dioxolane-4,5-diyl)bis(diphenyl methanol) (TADDOL) (7)-type catalysts. ... 

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