Transfer of Hydrogen from H2 Ligands

The most well-known reaction of hydrogen is catalytic hydrogenation, and H2 complexes are always intermediates in these processes, even if only transients in 

Two key questions are whether q2-H2 directly transfers H atoms to substrates such as olefins [Eq. 9.3)], i.e., without cleavage to hydrides, and whether H2 complexes have unusual or advantageous properties as catalysts. Examples of Eq. 

Protonation of an olefin-hydride complex to generate M(olefin)(H2) and observation of transfer of protons from q2-H2 to the olefin could prove direct reaction of H2 ligands, as in Eq. (9.55), where NBD is seen to be hydrogenated to nortricyclene.2,95 A dinuclear hydride with a vinylcyclopentadiene ligand is also 

A T-shaped 14e Rh complex containing a rigid P-C-P pincer ligand (see Chapter 7) reversibly binds H2 (31) and C02 (33) giving net insertion of C02 into the H2 complex. The hydrido-formate 32 quantitatively forms either upon treating 31 with C02 or 33 with H2 at room temperature. In the latter case predissociation 

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Reactions of H2 Complexes Relevant to Catalysis 1.24.2.4.1 Direct transfer of hydrogen from H2 ligands... 

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