A study of the full dehydrogenation of hydrazine borane (H₂N–NH₂·BH₃) to give H₂ and N₂ as gaseous products catalysed by a variety of group 4 metallocene alkyne complexes of the type Cp^′₂M(L)(η²-Me₃SiC₂SiMe₃) (Cp′ = substituted or unsubstituted η⁵-cyclopentadienyl; M = Ti, no L; M = Zr, L = pyridine) and group 4 metallocene hydrides is presented. Volumetric data show that the amount of hydrogen released is strongly dependent on both, the metal and the cyclopentadienyl ligand.