The Mackay-Type Cluster [Cu43Al12](Cp*)12: Open-Shell 67-Electron Superatom with Emerging Metal-Like Electronic Structure

The paramagnetic cluster [Cu43Al12](Cp*)(12) was obtained from the reaction of [CuMes](5) and [AlCp*](4) (Cp*-eta(5)-C5Me5; Mes = mesityl). This all-hydrocarbon ligand-stabilized M-55 magic atom-number cluster features a Mackay-type nested icosahedral structure. Its open-shell 67-electron superatom configuration is unique. Three unpaired electrons occupy weakly antibonding jellium states. The situation prefigures the formation of a conduction band, which is in line with the measured temperature-independent magnetism. Steric protection by twelve Cp* ligands suppresses the intrinsic polyradicalar reactivity of the Cu43Al12 core.