It is now a well-known fact that hydrogen can interact with transition-metal (TM) impurities, forming either electrically active or inactive complexes. An example of the former is the paramagnetic and orthorhombic (PtH2)- defect, observed experimentally by electron-paramagnetic resonance and IR-absorption [#!uftring-95!#]. Despite the success with the Pt- centre, experimental information on the structure and chemical composition of other TM-Hn complexes is still rather sparse and inconclusive.