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