{[CuSn5Sb3]2-}2: A Dimer of Inhomogeneous Superatoms

Reaction of the binary Zintl anion (Sn2Sb2)(2-) with the beta-diketiminato complex [LCu(NCMe)] (L= nacnac= [(N((C6H3Pr2)-Pr-i-2,6)C(Me))(2)CH](-)) in ethylenediamine or DMF affords the ternary cluster dimer {[CuSn5Sb3](2-)}(2) (1) as its [K(crypt-222)](+) salt. The chemical formulation of 1 is supported by energy-dispersive X-ray spectroscopy (EDX) and quantum chemical calculations. Each monomeric part of the dimer represents a trimetallic [CuSn5Sb3](2-) cluster, with an architecture in between a tricapped trigonal prism and a capped square antiprism. As shown by quantum chemical investigations, the presence of Sb atoms and, in particular, of Cu atoms in the cluster skeleton makes the monomeric unit behave like an inhomogeneous superatom, which clearly prefers to dimerize, thereby producing a relatively short, yet virtually non-bonding Cu center dot center dot center dot Cu distance.