Intermolecular heterolysis

A mononuclear hydride results here as the final organometallic product (unlike unobserved 14 in Scheme 5). Another possible scenario in Scheme 5 is intermolecular heterolysis of H2, e.g., protonation of the Me group in equilibrium quantities of 11 by the acidic H2 in 13 to give CH4,12, and 14. 

In addition to the above simple stoichiometric reactions, intermolecular heterolysis is observed or postulated in several types of exchange that can be catalytic, e.g.,... 

Davies, A.G. (1961) 0-0 heterolysis intermolecular nucleophilic substitution at oxygen, in Organic Peroxides, Butterworth, London, pp. 128-142. 

There are two distinct paths for cleavage of H-H (and X-H) bonds homolysis to a dihydride (as above) and heterolysis, that is, breaking the H-H bond into H and H fragment. Both paths have been identified in catalytic hydrogenation and are available for other cr-bond activations. A proton can split off from the H2 and migrate to either an external Lewis base (intermolecular) or a ligand/anion (intramolecular) as in Scheme 3. 

---