The reaction of the pentaene 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene(I) with Ru 3(CO) 12 under various conditions yield exo- and endo-tetrahaptotricarbonylruthenium complexes(IIa and IIIa). Mixed d 8 bimetallic complexes were obtained by the reaction of the exo-Fe(CO) 3 complex IIb with Ru 3(CO) 12, giving the exo-Fe(CO) 3, exo-Ru(CO) 3 (VI) and exoFe(CO) 3, endo-Ru(CO) 3 (VII) isomers. The same reaction starting with the endo-Fe(CO) 3 complex IIIb gave the third isomer endo-Fe(CO) 3, exo-Ru(CO) 3 (VIII). Metal substitution and intermolecular epimerisation occurs in the reaction of IIa with (benzalacetone)Fe(CO) 3 to give VII, VIII, and the endo, exo-bis(tricarbonylruthenium) complex (IVa), and with Fe 2(CO) 9 in excess to give IVb and the diexo-bis(tricarbonyliron) isomer Vb. Coordination of all five double bonds of I was achieved by the reaction of IIa with W(CO) 3(CH 3CN) 3 giving the exo-tetrahaptotricarbonylruthenium-hexahaptotricarbonyltungsten complex (IXa). Surprisingly, the oxidation of the bimetallic complexes with one equivalent Ce IV was found to be stereoselective in certain cases. The oxidation of VII, VIII, and IVb removes exclusively the metal in the exo position. In contrast, no selectivity was found during the oxidation of VI and of the endo, exo-bis(tricarbonyliron) complex X of the parent tetraene 2,3,5,6-tetrakis(methylene)bicyclo[2.2.2]octane In these systems the stereoselectivity of the oxidation is independent of the nature of the metal and occurs whenever stabilisation of the higher oxidation state of Ru or Fe can be achieved by transient coordination to the free endocyclic double bond of the ligand. The oxidation of the bimetallic complexes IXa (Ru) and IXb (FeMo) with one equivalent Ce IV removes the d 6 metal exclusively.