Neighbouring metal induced oxidative addition at the iron centre amongst the iron–arylpyridylphosphine complexes

Complexes of the type (η4-BuC5H5)Fe(CO)2(P) (P = PPh2Py 3, PPhPy24, PPy35; 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 (η4-BuC5H5). This results in a bridged hydrido heterodimetallic complex [(η5-BuC5H4)Fe(CO)(μ-P,N-PPh2Py)(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 [(η4-BuC5H5)Fe(CO)2(μ-P:N,N′-PPhPy2)M(CO)4] (M = Mo, 10a, 81%; W, 10b, 83%). Treatment of 5 with 6a,b gave [(η4-BuC5H5)Fe(CO)2(μ-P:N,N′,N″-PPy3)M(CO)3] (M = Mo, 12a, 96%; W, 12b, 78%).

A bridged hydrido heterodimetallic complex [(η5-BuC5H4)Fe(CO)(μ-P,N-PPh2Py)(μ-H)M(CO)4] (M = Mo,W) was produced as a result of induced oxidative addition of the endo-C–H of (η4-BuC5H5)Fe(CO)2PPh2Py by neighbouring metal. The CO transfer from Fe to M is more likely to be the slow step than the pyridyl N-ligation to M in the reaction coordinate to the state ready for oxidative addition of Fe(0). Complexes containing more than one pyridyl N-atoms could not exhibit hydride formation but produced heterodimetallic complexes [(η4-BuC5H5)Fe(CO)2(μ-P:N,N′-PPhPy2)M(CO)4] and [(η4-BuC5H5)Fe(CO)2(μ-P:N,N′,N″-PPy3)M(CO)3] (M = Mo, W).Figure optionsDownload as PowerPoint slide