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*=η5‐C5Me5; Mes=mesityl). This all‐hydrocarbon ligand‐stabilized M55 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. Superatomic: The reaction of [AlCp*]4 and [CuMes]5 yields the Mackay 55‐metal atom two‐shell icosahedral cluster [Cu43Al12](Cp*)12. The intermetalloid cluster has a unique 67‐electron open‐shell superatomic [Cu43Al12]12+ core, embedded inside an all‐hydrocarbon shell of twelve Cp*− ligands. Its electronic structure comprises a set of entangled HOMO und low‐lying LUMOs, prefiguring the formation of a conduction band.