Heteronuclear transition metal carbonyl cluster cations FeM-(CO)(8)(+) (M = Co, Ni and Cu) and MCu(CO)(7)(+) (M = Co and Ni) are produced via a laser vaporization supersonic cluster ion source in the gas phase, which are each mass-selected and studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Their geometric and electronic structures are established by comparison of the experimental spectra with those derived from density functional theoretical calculations. The FeM(CO)(8)(+) (M = Co, Ni, Cu) complexes are determined to have eclipsed (CO)(5)Fe-M(CO)(3) structures, and the MCu(CO)(7) (M = Co, Ni) ions are characterized to have staggered (CO)(4)M-Cu(CO)(3)(+) structures. Natural bonding orbital analysis indicates that the positive charge is mainly distributed on the M(CO)(3) fragment. The metal-metal interaction involves an a-type (OC)(4,5)M -> M(CO)(3) dative bonding.