[Cu {S CN Bu } (acetylide) ] : A Two-Electron Superatom.

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