Cr and Mo tetracarbonyl complexes bearing the diimine ligand N, N'-bis(ferrocenylmethylene)ethylenediamine (FcNN) have been prepared from the ligand and M(CO)(6). Two isomeric forms of (FcNN)Mo(CO)(4), corresponding to the cis, cis and cis, trans geometries with respect to the C=N bonds of the free ligand, were shown to exist in a 1:12.5 ratio by H-1 NMR (NOE experiments). By contrast, only the trans, trans isomer is observed for the Cr complex (FcNN)Cr(CO)(4). The compounds (FcNN)M(CO)(4) show ferrocene-based irreversible oxidation processes that lead to the deposition of a film at the electrode surface. (FcNN)Mo(CO)(4) was immobilised in permethylated beta-CD (TRIMEB) by addition of the guest to a solution of TRIMEB in dichloromethane. Removal of the solvent led to the isolation of an inclusion compound with a 2 : 1 host : guest stoichiometry, as evidenced by powder X-ray diffraction, thermogravimetric analysis, FTIR and C-13 CP MAS NMR spectroscopy. The electrochemical properties of (FcNN)Mo(CO)(4) upon encapsulation are discussed.