Protonation of hydride complex

The main synthetic methods used in the preparation of the coordination compounds mentioned above are reactions of coordinatively unsaturated complexes with hydrogen, protonation of hydride complexes, and formation of complexes containing molecular hydrogen by a synthesis reaction under reducing conditions. 

In the vast majority of studies on the protonation of hydride complexes, the kinetic site was the hydride ligand. This has been proven for many cases in which the thermodynamics of protonation favour a dihydride complex or a mixture of dihydride and dihydrogen complexes. In the case of CpW(CO)2(PMe3)H we have shown that hydride protonation (as monitored by exchange) is faster than protonation at the metal the intermediate dihydrogen complex rearranges too quickly to be observed [46]. 

Thus the protonation of hydride complexes often leads to loss of H. The reverse of this process, coordination and formation of a dihydrogen complex... 

Synthetic routes to H2 complexes include reaction of H2 with an unsaturated complex such as W(CO)3(PRj)2 or displacement of weak solvento ligands, for example, CH2CI2. Protonation of hydride complexes is common... 

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