Complexes of the type (η 4 -BuC 5 H 5 )Fe(CO) 2 (P) (P=PPh 2 Py 3, PPhPy 2 4, PPy 3 5; Py=2-pyridyl) were satisfactorily prepared. Upon treatment of 3 with M(CO) 3 (EtCN) 3 (M=Mo, 6a; W, 6b), the pyridyl N-atom could be coordinated to the metal M, which then eliminates a CO ligand from the Fe-centre and induced an oxidative addition of the endo-C–H of (η 4 -BuC 5 H 5 ). This results in a bridged hydrido heterodimetallic complex [(η 5 -BuC 5 H 4 )Fe(CO)(μ-P,N-PPh 2 Py)(μ-H)M(CO) 4 ] (M=Mo, 7a, 81%; W, 7b, 76%). The reaction of 4 or 5 with 6a,b did not give the induced oxidative addition, although these complexes contain more than one pyridyl N-atom. The reaction of 4 with M(CO) 4 (EtCN) 2 (M=Mo, 9a; W, 9b) produced heterodimetallic complexes [(η 4 -BuC 5 H 5 )Fe(CO) 2 (μ-P:N,N′-PPhPy 2 )M(CO) 4 ] (M=Mo, 10a, 81%; W, 10b, 83%). Treatment of 5 with 6a,b gave [(η 4 -BuC 5 H 5 )Fe(CO) 2 (μ-P:N,N′,N″-PPy 3 )M(CO) 3 ] (M=Mo, 12a, 96%; W, 12b, 78%).