[Cu13 {S2 CNn Bu2 }6 (acetylide)4 ]+ : A Two-Electron Superatom.

The first structurally characterized copper cluster with a Cu13 centered cuboctahedral arrangement, a model of the bulk copper fcc structure, was observed in [Cu13 (S2 CNn Bu2 )6 (C≡CR)4 ](PF6 ) (R=C(O)OMe, C6 H4 F) nanoclusters. Four of the eight triangular faces of the cuboctahedron are capped by acetylide groups in μ3  fashion, and each of the six square faces is bridged by a dithiolate ligand in μ2 ,μ2 fashion, which leads to a truncated tetrahedron of twelve sulfur atoms. DFT calculations are fully consistent with the description of these Cu13 clusters as two-electron superatoms, that is, a [Cu13 ]11+ core passivated by ten monoanionic ligands, with an a1 HOMO containing two 1S jellium electrons.