Synthesis, structure, and electrochemistry of the Ni–Au carbonyl cluster [Ni12Au(CO)24]3–and its relation to [Ni32Au6(CO)44]6–

A detailed study of the reaction between [Ni6(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 [Ni6(CO)12]2– moieties coordinated to a central Au(I) ion, as determined by X-ray diffraction. It is noteworthy that the two [Ni6(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 [Ni6(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.