A detailed study of the reaction between [Ni-6(CO)(12)](2-) and [AuCl4](-) afforded the isolation of the new Ni-Au cluster [Ni12Au(CO)(24)](3-) as well as identifying an improved synthesis for the previously reported [Ni32Au6(CO)(44)](6-). The new [Ni12Au(CO)(24)](3-) cluster is composed by two [Ni-6(CO)(12)](2-) moieties coordinated to a central Au(I) ion, as determined by X-ray diffraction. It is noteworthy that the two [Ni-6(CO)(12)](2-) fragments display different geometries, i.e., trigonal antiprismatic (distorted octahedral) and distorted trigonal prismatic (monocapped square pyramidal). The chemical reactivity of these clusters and their electrochemical behavior have been studied. [Ni12Au(CO)(24)](3-) is irreversibly transformed, upon electrochemical reduction, into Au(0) and [Ni-6(CO)(12)](2-), followed by the reversible reduction of the latter homometallic cluster. Conversely, [Ni32Au6(CO)(44)](6-) displays five reductions, with apparent features of reversibility, confirming the ability of larger metal carbonyl clusters to reversibly accept and release electrons.