Dihydrogen ligand or complex

This complex has been used for the synthesis of unusual complexes containing thiol ligands, dihydrogen ligands, or ligands with short proton-hydride distances. ... 

On the other hand, it is well known that a dihydrogen complex can be generated through direct proton attack on a hydride ligand or initial protonation of a metal center, leading to a new classical dihydride, [MH2]", which then converts to the dihydrogen complex [M(ti -H2)]. The latter is a thermodynamic product of the protonation reaction shown in Scheme 10.4 [16,17]. 

---