Complexes of the type M(CO)5(N-N), M(CO)4(N-N) and M(CO)3(N-N)2, where M is Cr, Mo or W and N-N is 1,8-naphthyridine(napy), 2-methyl-1,8-naphthyridine(2-mnapy) ortrans-decahydro-1,8-naphthyridine(dhnapy), have been prepared and characterized by infrared and proton magnetic spectroscopy. Complexes of the type Mo(CO)3(N-N)(napy), where N-N is 1,10-phenanthroline(phen), 2,2′-bipyridine(bipy), 2,9-dimethyl-1,10-phenanthroline(2,9-dmphen) or 2,7-dimethyl-1,8-naphthyridine (2,7-dmnapy), were also prepared and characterized by infrared spectroscopy. In these systems, the various naphthyridine donors exhibit the unique ability to behave as both mono- and bidentate ligands. The mode of bonding between the metal and heterocycles is determined by proton magnetic resonance data.